draft-fairhurst-tsvwg-transport-encrypt-09.txt   draft-fairhurst-tsvwg-transport-encrypt-10.txt 
TSVWG G. Fairhurst TSVWG G. Fairhurst
Internet-Draft University of Aberdeen Internet-Draft University of Aberdeen
Intended status: Informational C.S. Perkins Intended status: Informational C. Perkins
Expires: December 14, 2018 University of Glasgow Expires: February 28, 2019 University of Glasgow
June 14, 2018 August 27, 2018
The Impact of Transport Header Confidentiality on Network Operation and The Impact of Transport Header Confidentiality on Network Operation and
Evolution of the Internet Evolution of the Internet
draft-fairhurst-tsvwg-transport-encrypt-09 draft-fairhurst-tsvwg-transport-encrypt-10
Abstract Abstract
This document describes implications of applying end-to-end This document describes implications of applying end-to-end
encryption at the transport layer. It identifies in-network uses of encryption at the transport layer. It identifies in-network uses of
transport layer header information. It then reviews the implications transport layer header information. It then reviews the implications
of developing end-to-end transport protocols that use authentication of developing end-to-end transport protocols that use authentication
to protect the integrity of transport information or encryption to to protect the integrity of transport information or encryption to
provide confidentiality of the transport protocol header and expected provide confidentiality of the transport protocol header and expected
implications of transport protocol design and network operation. implications of transport protocol design and network operation.
Since transport measurement and analysis of the impact of network Since transport measurement and analysis of the impact of network
characteristics have been important to the design of current characteristics have been important to the design of current
transport protocols, it also considers the impact on transport and transport protocols, it also considers the impact on transport and
application evolution. application evolution.
Status of this Memo Status of This Memo
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provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Current uses of Transport Headers within the Network . . . . . 8 2. Context and Rationale . . . . . . . . . . . . . . . . . . . . 3
2.1. Observing Transport Information in the Network . . . . . . 9 3. Current uses of Transport Headers within the Network . . . . 9
2.1.1. Flow Identification . . . . . . . . . . . . . . . . . 9 3.1. Observing Transport Information in the Network . . . . . 9
2.1.2. Metrics derived from Transport Layer Headers . . . . . 10 3.2. Transport Measurement . . . . . . . . . . . . . . . . . . 15
2.1.3. Metrics derived from Network Layer Headers . . . . . . 13 3.3. Use for Network Diagnostics and Troubleshooting . . . . . 18
2.2. Transport Measurement . . . . . . . . . . . . . . . . . . 14 3.4. Observing Headers to Implement Network Policy . . . . . . 19
2.2.1. Point of Measurement . . . . . . . . . . . . . . . . . 15 4. Encryption and Authentication of Transport Headers . . . . . 19
2.2.2. Use by Operators to Plan and Provision Networks . . . 15 4.1. Authenticating the Transport Protocol Header . . . . . . 21
2.2.3. Service Performance Measurement . . . . . . . . . . . 16 4.2. Encrypting the Transport Payload . . . . . . . . . . . . 22
2.2.4. Measuring Transport to Support Network Operations . . 16 4.3. Encrypting the Transport Header . . . . . . . . . . . . . 22
2.3. Use for Network Diagnostics and Troubleshooting . . . . . 17 4.4. Authenticating Transport Information and Selectively
2.3.1. Examples of measurements . . . . . . . . . . . . . . . 18 Encrypting the Transport Header . . . . . . . . . . . . . 22
2.4. Observing Headers to Implement Network Policy . . . . . . 19 4.5. Optional Encryption of Header Information . . . . . . . . 23
3. Encryption and Authentication of Transport Headers . . . . . . 19 5. Addition of Transport Information to Network-Layer Protocol
3.1. Authenticating the Transport Protocol Header . . . . . . . 21 Headers . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2. Encrypting the Transport Payload . . . . . . . . . . . . . 21 6. Implications of Protecting the Transport Headers . . . . . . 24
3.3. Encrypting the Transport Header . . . . . . . . . . . . . 21 6.1. Independent Measurement . . . . . . . . . . . . . . . . . 24
3.4. Authenticating Transport Information and Selectively 6.2. Characterising "Unknown" Network Traffic . . . . . . . . 25
Encrypting the Transport Header . . . . . . . . . . . . . 22 6.3. Accountability and Internet Transport Protocols . . . . . 25
3.5. Optional Encryption of Header Information . . . . . . . . 22 6.4. Impact on Research, Development and Deployment . . . . . 26
4. Addition of Transport Information to Network-Layer Protocol 7. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 27
Headers . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 8. Security Considerations . . . . . . . . . . . . . . . . . . . 29
5. Implications of Protecting the Transport Headers . . . . . . . 23 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
5.1. Independent Measurement . . . . . . . . . . . . . . . . . 23 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 31
5.2. Characterising "Unknown" Network Traffic . . . . . . . . . 24 11. Informative References . . . . . . . . . . . . . . . . . . . 31
5.3. Accountability and Internet Transport Protocols . . . . . 25 Appendix A. Revision information . . . . . . . . . . . . . . . . 37
5.4. Impact on Research, Development and Deployment . . . . . . 25 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37
6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 27
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 29
8. Security Considerations . . . . . . . . . . . . . . . . . . . 29
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31
10.1. Normative References . . . . . . . . . . . . . . . . . . 31
10.2. Informative References . . . . . . . . . . . . . . . . . 31
Appendix A. Revision information . . . . . . . . . . . . . . . . . 36
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 37
1. Introduction 1. Introduction
This document describes implications of applying end-to-end This document describes implications of applying end-to-end
encryption at the transport layer. It reviews the implications of encryption at the transport layer. It reviews the implications of
developing end-to-end transport protocols that use encryption to developing end-to-end transport protocols that use encryption to
provide confidentiality of the transport protocol header and expected provide confidentiality of the transport protocol header and expected
implications of transport protocol design and network operation. It implications of transport protocol design and network operation. It
also considers anticipated implications on transport and application also considers anticipated implications on transport and application
evolution. evolution.
2. Context and Rationale
The transport layer provides end-to-end interactions between The transport layer provides end-to-end interactions between
endpoints (processes) using an Internet path. Transport protocols endpoints (processes) using an Internet path. Transport protocols
layer directly over the network-layer service and are sent in the layer directly over the network-layer service and are sent in the
payload of network-layer packets. They support end-to-end payload of network-layer packets. They support end-to-end
communication between applications, supported by higher-layer communication between applications, supported by higher-layer
protocols, running on the end systems (or transport endpoints). This protocols, running on the end systems (or transport endpoints). This
simple architectural view hides one of the core functions of the simple architectural view hides one of the core functions of the
transport, however, to discover and adapt to the properties of the transport, however, to discover and adapt to the properties of the
Internet path that is currently being used. The design of Internet Internet path that is currently being used. The design of Internet
transport protocols is as much about trying to avoid the unwanted transport protocols is as much about trying to avoid the unwanted
side effects of congestion on a flow and other capacity-sharing side effects of congestion on a flow and other capacity-sharing
flows, avoiding congestion collapse, adapting to changes in the path flows, avoiding congestion collapse, adapting to changes in the path
characteristics, etc., as it is about end-to-end feature negotiation, characteristics, etc., as it is about end-to-end feature negotiation,
flow control and optimising for performance of a specific flow control and optimising for performance of a specific
application. application.
To achieve stable Internet operations the IETF transport community To achieve stable Internet operations the IETF transport community
has to date relied heavily on measurement and insights of the network has to date relied heavily on measurement and insights of the network
operations community to understand the trade-offs, and to inform operations community to understand the trade-offs, and to inform
selection of appropriate mechanisms, to ensure a safe, reliable, and selection of appropriate mechanisms, to ensure a safe, reliable, and
robust Internet (e.g., [RFC1273]). In turn, the network operations robust Internet (e.g., [RFC1273]). In turn, the network operations
community relies on being able to understand the pattern and community relies on being able to understand the pattern and
requirements of traffic passing over the Internet, both in aggregate requirements of traffic passing over the Internet, both in aggregate
and at the flow level. and at the flow level.
There are many motivations for deploying encrypted transports There are many motivations for deploying encrypted transports
[RFC7624] (i.e., transport protocols that use encryption to provide [RFC7624] (i.e., transport protocols that use encryption to provide
confidentiality of some or all of the transport-layer header confidentiality of some or all of the transport-layer header
information), and encryption of transport payloads (i.e. information), and encryption of transport payloads (i.e.
confidentiality of the payload data). The increasing public concerns confidentiality of the payload data). The increasing public concerns
about the interference with Internet traffic have led to a rapidly about the interference with Internet traffic have led to a rapidly
expanding deployment of encryption to protect end-user privacy, in expanding deployment of encryption to protect end-user privacy, in
protocols like QUIC [I-D.ietf-quic-transport], but also expected to protocols like QUIC [I-D.ietf-quic-transport], but also expected to
form a basis of future protocol designs. form a basis of future protocol designs.
Some network operators and access providers, have come to rely on the Some network operators and access providers, have come to rely on the
in-network measurement of transport properties and the functionality in-network measurement of transport properties and the functionality
provided by middleboxes to both support network operations and provided by middleboxes to both support network operations and
enhance performance. There can therefore be implications when enhance performance. There can therefore be implications when
working with encrypted transport protocols that hide transport header working with encrypted transport protocols that hide transport header
information from the network. These present architectural challenges information from the network. These present architectural challenges
and considerations in the way transport protocols are designed, and and considerations in the way transport protocols are designed, and
ability to characterise and compare different transport solutions ability to characterise and compare different transport solutions
[Measure], Section 2.2. Implementations of network devices are
[Measure], Section 3.2. Implementations of network devices are
encouraged to avoid side-effects when protocols are updated. encouraged to avoid side-effects when protocols are updated.
Introducing cryptographic integrity checks to header fields can also Introducing cryptographic integrity checks to header fields can also
prevent undetected manipulation of the field by network devices, or prevent undetected manipulation of the field by network devices, or
undetected addition of information to a packet. However, this does undetected addition of information to a packet. However, this does
not prevent inspection of the information by a device on path, and it not prevent inspection of the information by a device on path, and it
is possible that such devices could develop mechanisms that rely on is possible that such devices could develop mechanisms that rely on
the presence of such a field, or a known value in the field. the presence of such a field, or a known value in the field.
Reliance on the presence and semantics of specific header information Reliance on the presence and semantics of specific header information
leads to ossification: An endpoint could be required to supply a leads to ossification: An endpoint could be required to supply a
specific header to receive the network service that it desires. In specific header to receive the network service that it desires. In
some cases, this could be benign or advantageous to the protocol some cases, this could be benign or advantageous to the protocol
(e.g., recognising the start of a connection, or explicitly exposing (e.g., recognising the start of a connection, or explicitly exposing
protocol information can be expected to provide more consistent protocol information can be expected to provide more consistent
decisions by on-path devices than the use of diverse methods to infer decisions by on-path devices than the use of diverse methods to infer
semantics from other flow properties). In some cases, this is not semantics from other flow properties). In some cases, this is not
beneficial (e.g., a mechanism implemented in a network device, such beneficial (e.g., a mechanism implemented in a network device, such
as a firewall, that required a header field to have only a specific as a firewall, that required a header field to have only a specific
known set of values could prevent the device from forwarding packets known set of values could prevent the device from forwarding packets
using a different version of a protocol that introduces a new feature using a different version of a protocol that introduces a new feature
that changes the value present in this field, preventing evolution of that changes the value present in this field, preventing evolution of
the protocol). the protocol).
Examples of the impact of ossification on transport protocol design
and ease of deployment can be seen in the case of Multipath TCP
(MPTCP) and the TCP Fast Open option. The design of MPTCP had to be
revised to account for middleboxes, so called "TCP Normalizers", that
monitor the evolution of the window advertised in the TCP headers and
that reset connections if the window does not grow as expected.
Similarly, TCP Fast Open has had issues with middleboxes that remove
unknown TCP options, that drop segments with unknown TCP options,
that drop segments that contain data and have the SYN bit set, that
drop packets with SYN/ACK that acknowledge data, or that disrupt
connections that send data before the three-way handshake completes.
In both cases, the issue was caused by middleboxes that had a hard-
coded understanding of transport behaviour, and that interacted
poorly with transports that tried to change that behaviour. Other
examples have included middleboxes that rewrite TCP sequence and
acknowledgement numbers but are unaware of the (newer) SACK option
and don't correctly rewrite selective acknowledgements to match the
changes made to the fixed TCP header; or devices that inspect, and
change, TCP MSS options that can interfere with path MTU discovery.
A protocol design that uses header encryption can provide A protocol design that uses header encryption can provide
confidentiality of some or all of the protocol header information. confidentiality of some or all of the protocol header information.
This prevents an on-path device from knowledge of the header field. This prevents an on-path device from knowledge of the header field.
It therefore prevents mechanisms being built that directly rely on It therefore prevents mechanisms being built that directly rely on
the information or seeks to imply semantics of an exposed header the information or seeks to imply semantics of an exposed header
field. Using encryption to provide confidentiality of the transport field. Using encryption to provide confidentiality of the transport
layer brings some well-known privacy and security benefits and can layer brings some well-known privacy and security benefits and can
therefore help reduce ossification of the transport layer. In therefore help reduce ossification of the transport layer. In
particular, it is important that protocols either do not expose particular, it is important that protocols either do not expose
information where the usage may change in future protocols, or that information where the usage may change in future protocols, or that
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transport protocol. transport protocol.
A level of ossification of the transport header can offer trade-offs A level of ossification of the transport header can offer trade-offs
around authentication, and confidentiality of transport protocol around authentication, and confidentiality of transport protocol
headers and has the potential to explicitly support for other uses of headers and has the potential to explicitly support for other uses of
this header information. For example, a design that provides this header information. For example, a design that provides
confidentiality of protocol header information can impact the confidentiality of protocol header information can impact the
following activities that rely on measurement and analysis of traffic following activities that rely on measurement and analysis of traffic
flows: flows:
Network Operations and Research: Observable transport headers enable Network Operations and Research: Observable transport headers enable
both operators and the research community to measure and analyse both operators and the research community to measure and analyse
protocol performance, network anomalies, and failure pathologies. protocol performance, network anomalies, and failure pathologies.
This information can help inform capacity planning, and assist in This information can help inform capacity planning, and assist in
determining the need for equipment and/or configuration changes by determining the need for equipment and/or configuration changes by
network operators. network operators.
The data can also inform Internet engineering research, and help The data can also inform Internet engineering research, and help
in the development of new protocols, methodologies, and in the development of new protocols, methodologies, and
procedures. Concealing the transport protocol header information procedures. Concealing the transport protocol header information
makes the stream performance unavailable to passive observers makes the stream performance unavailable to passive observers
along the path, and likely leads to the development of alternative along the path, and likely leads to the development of alternative
methods to collect or infer that data. methods to collect or infer that data.
Providing confidentiality of the transport payload, but leaving Providing confidentiality of the transport payload, but leaving
some, or all, of the transport headers unencrypted, possibly with some, or all, of the transport headers unencrypted, possibly with
authentication, can provide the majority of the privacy and authentication, can provide the majority of the privacy and
security benefits while allowing some measurement. security benefits while allowing some measurement.
Protection from Denial of Service: Observable transport headers Protection from Denial of Service: Observable transport headers
currently provide useful input to classify traffic and detect currently provide useful input to classify traffic and detect
anomalous events (e.g., changes in application behaviour, anomalous events (e.g., changes in application behaviour,
distributed denial of service attacks). To be effective, this distributed denial of service attacks). To be effective, this
protection needs to be able to uniquely disambiguate unwanted protection needs to be able to uniquely disambiguate unwanted
traffic. An inability to separate this traffic using packet traffic. An inability to separate this traffic using packet
header information may result in less-efficient identification of header information may result in less-efficient identification of
unwanted traffic or development of different methods (e.g. rate- unwanted traffic or development of different methods (e.g. rate-
limiting of uncharacterised traffic). limiting of uncharacterised traffic).
Network Troubleshooting and Diagnostics: Encrypting transport header Network Troubleshooting and Diagnostics: Encrypting transport
information eliminates the incentive for operators to troubleshoot header information eliminates the incentive for operators to
what they cannot interpret. A flow experiencing packet loss or troubleshoot what they cannot interpret. A flow experiencing
jitter looks like an unaffected flow when only observing network packet loss or jitter looks like an unaffected flow when only
layer headers (if transport sequence numbers and flow identifiers observing network layer headers (if transport sequence numbers and
are obscured). This limits understanding of the impact of packet flow identifiers are obscured). This limits understanding of the
loss or latency on the flows, or even localizing the network impact of packet loss or latency on the flows, or even localizing
segment causing the packet loss or latency. Encrypted traffic may the network segment causing the packet loss or latency. Encrypted
imply "don't touch" to some, and could limit a trouble-shooting traffic may imply "don't touch" to some, and could limit a
response to "can't help, no trouble found". The additional trouble-shooting response to "can't help, no trouble found". The
mechanisms that will need to be introduced to help reconstruct additional mechanisms that will need to be introduced to help
transport-level metrics add complexity and operational costs reconstruct transport-level metrics add complexity and operational
(e.g., in deploying additional functions in equipment or adding costs (e.g., in deploying additional functions in equipment or
traffic overhead). adding traffic overhead).
Network Traffic Analysis: Hiding transport protocol header Network Traffic Analysis: Hiding transport protocol header
information can make it harder to determine which transport information can make it harder to determine which transport
protocols and features are being used across a network segment and protocols and features are being used across a network segment and
to measure trends in the pattern of usage. This could impact the to measure trends in the pattern of usage. This could impact the
ability for an operator to anticipate the need for network ability for an operator to anticipate the need for network
upgrades and roll-out. It can also impact the on-going traffic upgrades and roll-out. It can also impact the on-going traffic
engineering activities performed by operators (such as determining engineering activities performed by operators (such as determining
which parts of the path contribute delay, jitter or loss). While which parts of the path contribute delay, jitter or loss). While
the impact may, in many cases, be small there are scenarios where the impact may, in many cases, be small there are scenarios where
operators directly support particular services (e.g., to operators directly support particular services (e.g., to
troubleshoot issues relating to Quality of Service, QoS; the troubleshoot issues relating to Quality of Service, QoS; the
ability to perform fast re-routing of critical traffic, or support ability to perform fast re-routing of critical traffic, or support
to mitigate the characteristics of specific radio links). The more to mitigate the characteristics of specific radio links). The
complex the underlying infrastructure the more important this more complex the underlying infrastructure the more important this
impact. impact.
Open and Verifiable Network Data: Hiding transport protocol header Open and Verifiable Network Data: Hiding transport protocol header
information can reduce the range of actors that can capture useful information can reduce the range of actors that can capture useful
measurement data. For example, one approach could be to employ an measurement data. For example, one approach could be to employ an
existing transport protocol that reveals little information (e.g., existing transport protocol that reveals little information (e.g.,
UDP), and perform traditional transport functions at higher layers UDP), and perform traditional transport functions at higher layers
protecting the confidentiality of transport information. Such a protecting the confidentiality of transport information. Such a
design, limits the information sources available to the Internet design, limits the information sources available to the Internet
community to understand the operation of new transport protocols, community to understand the operation of new transport protocols,
so preventing access to the information necessary to inform design so preventing access to the information necessary to inform design
decisions and standardisation of the new protocols and related decisions and standardisation of the new protocols and related
operational practices. operational practices.
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support. The choice of whether future transport protocols encrypt support. The choice of whether future transport protocols encrypt
their protocol headers therefore needs to be taken based not solely their protocol headers therefore needs to be taken based not solely
on security and privacy considerations, but also taking into account on security and privacy considerations, but also taking into account
the impact on operations, standards, and research. Any new Internet the impact on operations, standards, and research. Any new Internet
transport need to provide appropriate transport mechanisms and transport need to provide appropriate transport mechanisms and
operational support to assure the resulting traffic can not result in operational support to assure the resulting traffic can not result in
persistent congestion collapse [RFC2914]. This document suggests persistent congestion collapse [RFC2914]. This document suggests
that the balance between information exposed and concealed should be that the balance between information exposed and concealed should be
carefully considered when specifying new protocols. carefully considered when specifying new protocols.
2. Current uses of Transport Headers within the Network 3. Current uses of Transport Headers within the Network
Despite transport headers having end-to-end meaning, some of these Despite transport headers having end-to-end meaning, some of these
transport headers have come to be used in various ways within the transport headers have come to be used in various ways within the
Internet. In response to pervasive monitoring [RFC7624] revelations Internet. In response to pervasive monitoring [RFC7624] revelations
and the IETF consensus that "Pervasive Monitoring is an Attack" and the IETF consensus that "Pervasive Monitoring is an Attack"
[RFC7258], efforts are underway to increase encryption of Internet [RFC7258], efforts are underway to increase encryption of Internet
traffic,. Applying confidentiality to transport header fields would traffic,. Applying confidentiality to transport header fields would
affect how protocol information is used [I-D.mm-wg-effect-encrypt]. affect how protocol information is used [RFC8404]. To understand
To understand these implications, it is first necessary to understand these implications, it is first necessary to understand how transport
how transport layer headers are currently observed and/or modified by layer headers are currently observed and/or modified by middleboxes
middleboxes within the network. within the network.
Transport protocols can be designed to encrypt or authenticate Transport protocols can be designed to encrypt or authenticate
transport header fields. Authentication at the transport layer can transport header fields. Authentication at the transport layer can
be used to detect any changes to an immutable header field that were be used to detect any changes to an immutable header field that were
made by a network device along a path. The intentional modification made by a network device along a path. The intentional modification
of transport headers by middleboxes (such as Network Address of transport headers by middleboxes (such as Network Address
Translation, NAT, or Firewalls) is not considered. Common issues Translation, NAT, or Firewalls) is not considered. Common issues
concerning IP address sharing are described in [RFC6269]. concerning IP address sharing are described in [RFC6269].
2.1. Observing Transport Information in the Network 3.1. Observing Transport Information in the Network
If in-network observation of transport protocol headers is needed, If in-network observation of transport protocol headers is needed,
this requires knowledge of the format of the transport header: this requires knowledge of the format of the transport header:
o Flows need to be identified at the level required to perform the o Flows need to be identified at the level required to perform the
observation; observation;
o The protocol and version of the header need to be visible. As o The protocol and version of the header need to be visible. As
protocols evolve over time and there may be a need to introduce protocols evolve over time and there may be a need to introduce
new transport headers. This may require interpretation of new transport headers. This may require interpretation of
protocol version information or connection setup information; protocol version information or connection setup information;
o The location and syntax of any observed transport headers needs to o The location and syntax of any observed transport headers needs to
be known. IETF transport protocols can specify this information. be known. IETF transport protocols can specify this information.
The following subsections describe various ways that observable The following subsections describe various ways that observable
transport information has been utilised. transport information has been utilised.
2.1.1. Flow Identification 3.1.1. Flow Identification
Transport protocol header information (together with information in Transport protocol header information (together with information in
the network header), has been used to identify a flow and the the network header), has been used to identify a flow and the
connection state of the flow, together with the protocol options connection state of the flow, together with the protocol options
being used. In some usages, a low-numbered (well-known) transport being used. In some usages, a low-numbered (well-known) transport
port number has been used to identify a protocol (although port port number has been used to identify a protocol (although port
information alone is not sufficient to guarantee identification of a information alone is not sufficient to guarantee identification of a
protocol, since applications can use arbitrary ports, multiple protocol, since applications can use arbitrary ports, multiple
sessions can be multiplexed on a single port, and ports can be re- sessions can be multiplexed on a single port, and ports can be re-
used by subsequent sessions). used by subsequent sessions).
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number in the transport header. UDP-based protocols can use, but number in the transport header. UDP-based protocols can use, but
sometimes do not use, well-known port numbers. Some flows can sometimes do not use, well-known port numbers. Some flows can
instead be identified by signalling protocols or through the use of instead be identified by signalling protocols or through the use of
magic numbers placed in the first byte(s) of the datagram payload. magic numbers placed in the first byte(s) of the datagram payload.
Flow identification is a common function. For example, performed by Flow identification is a common function. For example, performed by
measurement activities, QoS classification, firewalls, Denial of measurement activities, QoS classification, firewalls, Denial of
Service, DOS, prevention. It becomes more complex and less easily Service, DOS, prevention. It becomes more complex and less easily
achieved when multiplexing is used at or above the transport layer. achieved when multiplexing is used at or above the transport layer.
2.1.2. Metrics derived from Transport Layer Headers 3.1.2. Metrics derived from Transport Layer Headers
Some actors manage their portion of the Internet by characterizing Some actors manage their portion of the Internet by characterizing
the performance of link/network segments. Passive monitoring uses the performance of link/network segments. Passive monitoring uses
observed traffic to makes inferences from transport headers to derive observed traffic to makes inferences from transport headers to derive
these measurements. A variety of open source and commercial tools these measurements. A variety of open source and commercial tools
have been deployed that utilise this information. The following have been deployed that utilise this information. The following
metrics can be derived from transport header information: metrics can be derived from transport header information:
Traffic Rate and Volume: Header information e.g., (sequence number, Traffic Rate and Volume: Header information e.g., (sequence number,
length) allows derivation of volume measures per-application, to length) allows derivation of volume measures per-application, to
characterise the traffic that uses a network segment or the characterise the traffic that uses a network segment or the
pattern of network usage. This may be measured per endpoint or pattern of network usage. This may be measured per endpoint or
for an aggregate of endpoints (e.g., by an operator to assess for an aggregate of endpoints (e.g., by an operator to assess
subscriber usage). It can also be used to trigger measurement- subscriber usage). It can also be used to trigger measurement-
based traffic shaping and to implement QoS support within the based traffic shaping and to implement QoS support within the
network and lower layers. Volume measures can be valuable for network and lower layers. Volume measures can be valuable for
capacity planning (providing detail of trends rather than the capacity planning (providing detail of trends rather than the
volume per subscriber). volume per subscriber).
Loss Rate and Loss Pattern: Flow loss rate may be derived (e.g., from Loss Rate and Loss Pattern: Flow loss rate may be derived (e.g.,
sequence number) and has been used as a metric for performance from sequence number) and has been used as a metric for
assessment and to characterise transport behaviour. Understanding performance assessment and to characterise transport behaviour.
the root cause of loss can help an operator determine whether this Understanding the root cause of loss can help an operator
requires corrective action. Network operators have used the determine whether this requires corrective action. Network
variation in patterns of loss as a key performance metric, operators have used the variation in patterns of loss as a key
utilising this to detect changes in the offered service. performance metric, utilising this to detect changes in the
offered service.
There are various causes of loss, including: corruption of link There are various causes of loss, including: corruption of link
frames (e.g., interference on a radio link), buffer overflow frames (e.g., interference on a radio link), buffer overflow
(e.g., due to congestion), policing (traffic management), buffer (e.g., due to congestion), policing (traffic management), buffer
management (e.g., Active Queue Management, AQM [RFC7567]), management (e.g., Active Queue Management, AQM [RFC7567]),
inadequate provision of traffic preemption. Understanding flow inadequate provision of traffic preemption. Understanding flow
loss rate requires either maintaining per flow packet counters or loss rate requires either maintaining per flow packet counters or
by observing sequence numbers in transport headers. Loss can be by observing sequence numbers in transport headers. Loss can be
monitored at the interface level by devices in the network. It is monitored at the interface level by devices in the network. It is
often important to understand the conditions under which packet often important to understand the conditions under which packet
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Observation of transport feedback information (observing loss Observation of transport feedback information (observing loss
reports, e.g., RTP Control Protocol (RTCP) [RFC3550], TCP SACK) reports, e.g., RTP Control Protocol (RTCP) [RFC3550], TCP SACK)
can increase understanding of the impact of loss and help identify can increase understanding of the impact of loss and help identify
cases where loss may have been wrongly identified, or the cases where loss may have been wrongly identified, or the
transport did not require the lost packet. It is sometimes more transport did not require the lost packet. It is sometimes more
important to understand the pattern of loss, than the loss rate, important to understand the pattern of loss, than the loss rate,
because losses can often occur as bursts, rather than randomly- because losses can often occur as bursts, rather than randomly-
timed events. timed events.
Throughput and Goodput: The throughput achieved by a flow can be Throughput and Goodput: The throughput achieved by a flow can be
determined even when a flow is encrypted, providing the individual determined even when a flow is encrypted, providing the individual
flow can be identified. Goodput [RFC7928] is a measure of useful flow can be identified. Goodput [RFC7928] is a measure of useful
data exchanged (the ratio of useful/total volume of traffic sent data exchanged (the ratio of useful/total volume of traffic sent
by a flow). This requires ability to differentiate loss and by a flow). This requires ability to differentiate loss and
retransmission of packets (e.g., by observing packet sequence retransmission of packets (e.g., by observing packet sequence
numbers in the TCP or the Real Time Protocol, RTP, headers numbers in the TCP or the Real Time Protocol, RTP, headers
[RFC3550]). [RFC3550]).
Latency: Latency is a key performance metric that impacts application Latency: Latency is a key performance metric that impacts
response time and user-perceived response time. It often application response time and user-perceived response time. It
indirectly impacts throughput and flow completion time. Latency often indirectly impacts throughput and flow completion time.
determines the reaction time of the transport protocol itself, Latency determines the reaction time of the transport protocol
impacting flow setup, congestion control, loss recovery, and other itself, impacting flow setup, congestion control, loss recovery,
transport mechanisms. The observed latency can have many and other transport mechanisms. The observed latency can have
components [Latency]. Of these, unnecessary/unwanted queuing in many components [Latency]. Of these, unnecessary/unwanted queuing
network buffers has often been observed as a significant factor. in network buffers has often been observed as a significant
Once the cause of unwanted latency has been identified, this can factor. Once the cause of unwanted latency has been identified,
often be eliminated. this can often be eliminated.
To measure latency across a part of a path, an observation point To measure latency across a part of a path, an observation point
can measure the experienced round trip time (RTT) using packet can measure the experienced round trip time (RTT) using packet
sequence numbers, and acknowledgements, or by observing header sequence numbers, and acknowledgements, or by observing header
timestamp information. Such information allows an observation timestamp information. Such information allows an observation
point in the network to determine not only the path RTT, but also point in the network to determine not only the path RTT, but also
to measure the upstream and downstream contribution to the RTT. to measure the upstream and downstream contribution to the RTT.
This has been used to locate a source of latency, e.g., by This has been used to locate a source of latency, e.g., by
observing cases where the ratio of median to minimum RTT is large observing cases where the ratio of median to minimum RTT is large
for a part of a path. for a part of a path.
The service offered by operators can benefit from latency The service offered by operators can benefit from latency
information to understand the impact of deployment and tune information to understand the impact of deployment and tune
deployed services. Latency metrics are key to evaluating and deployed services. Latency metrics are key to evaluating and
deploying AQM [RFC7567], DiffServ [RFC2474], and Explicit deploying AQM [RFC7567], DiffServ [RFC2474], and Explicit
Congestion Notification (ECN) [RFC3168] [RFC8087]. Measurements Congestion Notification (ECN) [RFC3168] [RFC8087]. Measurements
could identify excessively large buffers, indicating where to could identify excessively large buffers, indicating where to
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This has been used to locate a source of latency, e.g., by This has been used to locate a source of latency, e.g., by
observing cases where the ratio of median to minimum RTT is large observing cases where the ratio of median to minimum RTT is large
for a part of a path. for a part of a path.
The service offered by operators can benefit from latency The service offered by operators can benefit from latency
information to understand the impact of deployment and tune information to understand the impact of deployment and tune
deployed services. Latency metrics are key to evaluating and deployed services. Latency metrics are key to evaluating and
deploying AQM [RFC7567], DiffServ [RFC2474], and Explicit deploying AQM [RFC7567], DiffServ [RFC2474], and Explicit
Congestion Notification (ECN) [RFC3168] [RFC8087]. Measurements Congestion Notification (ECN) [RFC3168] [RFC8087]. Measurements
could identify excessively large buffers, indicating where to could identify excessively large buffers, indicating where to
deploy or configure AQM. An AQM method is often deployed in deploy or configure AQM. An AQM method is often deployed in
combination with other techniques, such as scheduling [RFC7567] combination with other techniques, such as scheduling [RFC7567]
[I-D.ietf-aqm-fq-codel] and although parameter-less methods are [RFC8290] and although parameter-less methods are desired
desired [RFC7567], current methods [I-D.ietf-aqm-fq-codel] [I-D [RFC7567], current methods [RFC8290] [RFC8289] [RFC8033] often
.ietf-aqm-codel] [I-D.ietf-aqm-pie] often cannot scale across all cannot scale across all possible deployment scenarios.
possible deployment scenarios.
Variation in delay: Some network applications are sensitive to small Variation in delay: Some network applications are sensitive to small
changes in packet timing. To assess the performance of such changes in packet timing. To assess the performance of such
applications, it can be necessary to measure the variation in applications, it can be necessary to measure the variation in
delay observed along a portion of the path [RFC3393] [RFC5481]. delay observed along a portion of the path [RFC3393] [RFC5481].
The requirements resemble those for the measurement of latency. The requirements resemble those for the measurement of latency.
Flow Reordering: Significant flow reordering can impact time-critical Flow Reordering: Significant flow reordering can impact time-
applications and can be interpreted as loss by reliable critical applications and can be interpreted as loss by reliable
transports. Many transport protocol techniques are impacted by transports. Many transport protocol techniques are impacted by
reordering (e.g., triggering TCP retransmission, or re-buffering reordering (e.g., triggering TCP retransmission, or re-buffering
of real-time applications). Packet reordering can occur for many of real-time applications). Packet reordering can occur for many
reasons (from equipment design to misconfiguration of forwarding reasons (from equipment design to misconfiguration of forwarding
rules). Since this impacts transport performance, network tools rules). Since this impacts transport performance, network tools
are needed to detect and measure unwanted/excessive reordering. are needed to detect and measure unwanted/excessive reordering.
There have been initiatives in the IETF transport area to reduce There have been initiatives in the IETF transport area to reduce
the impact of reordering within a transport flow, possibly leading the impact of reordering within a transport flow, possibly leading
to a reduction in the requirements for preserving ordering. These to a reduction in the requirements for preserving ordering. These
have promise to simplify network equipment design as well as the have promise to simplify network equipment design as well as the
potential to improve robustness of the transport service. potential to improve robustness of the transport service.
Measurements of reordering can help understand the present level Measurements of reordering can help understand the present level
of reordering within deployed infrastructure, and inform decisions of reordering within deployed infrastructure, and inform decisions
about how to progress such mechanisms. about how to progress such mechanisms.
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rate, etc. rate, etc.
Metrics have been defined that evaluate whether a network has Metrics have been defined that evaluate whether a network has
maintained packet order on a packet-by-packet basis [RFC4737] and maintained packet order on a packet-by-packet basis [RFC4737] and
[RFC5236]. [RFC5236].
Techniques for measuring reordering typically observe packet sequence Techniques for measuring reordering typically observe packet sequence
numbers. Some protocols provide in-built monitoring and reporting numbers. Some protocols provide in-built monitoring and reporting
functions. Transport fields in the RTP header [RFC3550] [RFC4585] functions. Transport fields in the RTP header [RFC3550] [RFC4585]
can be observed to derive traffic volume measurements and provide can be observed to derive traffic volume measurements and provide
information on the progress and quality of a session using RTP. As information on the progress and quality of a session using RTP. As
with other measurement, metadata is often important to understand the with other measurement, metadata is often important to understand the
context under which the data was collected, including the time, context under which the data was collected, including the time,
observation point, and way in which metrics were accumulated. The observation point, and way in which metrics were accumulated. The
RTCP protocol directly reports some of this information in a form RTCP protocol directly reports some of this information in a form
that can be directly visible in the network. A user of summary that can be directly visible in the network. A user of summary
measurement data needs to trust the source of this data and the measurement data needs to trust the source of this data and the
method used to generate the summary information. method used to generate the summary information.
2.1.3. Metrics derived from Network Layer Headers 3.1.3. Metrics derived from Network Layer Headers
Some transport information is made visible in the network-layer Some transport information is made visible in the network-layer
protocol header. These header fields are not encrypted and have been protocol header. These header fields are not encrypted and have been
utilised to make flow observations. utilised to make flow observations.
Use of IPv6 Network-Layer Flow Label: Endpoints are encouraged expose Use of IPv6 Network-Layer Flow Label: Endpoints are encouraged
flow information in the IPv6 Flow Label field of the network-layer expose flow information in the IPv6 Flow Label field of the
header (e.g., [RFC8085]). This can be used to inform network-layer network-layer header (e.g., [RFC8085]). This can be used to
queuing, forwarding (e.g., for Equal Cost Multi-Path, ECMP, inform network-layer queuing, forwarding (e.g., for Equal Cost
routing, and Link Aggregation, LAG). This can provide useful Multi-Path, ECMP, routing, and Link Aggregation, LAG). This can
information to assign packets to flows in the data collected by provide useful information to assign packets to flows in the data
measurement campaigns. Although important to characterising a collected by measurement campaigns. Although important to
path, it does not directly provide performance data. characterising a path, it does not directly provide performance
data.
Use Network-Layer Differentiated Services Code Point Point: Applicati Use Network-Layer Differentiated Services Code Point Point:
ons can expose their delivery expectations to the network by Applications can expose their delivery expectations to the network
setting the Differentiated Services Code Point (DSCP) field of by setting the Differentiated Services Code Point (DSCP) field of
IPv4 and IPv6 packets. This can be used to inform network-layer IPv4 and IPv6 packets. This can be used to inform network-layer
queuing and forwarding, and can also provide information on the queuing and forwarding, and can also provide information on the
relative importance of packet information collected by measurement relative importance of packet information collected by measurement
campaigns, but does not directly provide performance data. campaigns, but does not directly provide performance data.
This field provides explicit information that can be used in place This field provides explicit information that can be used in place
of inferring traffic requirements (e.g., by inferring QoS of inferring traffic requirements (e.g., by inferring QoS
requirements from port information via a multi-field classifier). requirements from port information via a multi-field classifier).
The DSCP value can therefore impact the quality of experience for The DSCP value can therefore impact the quality of experience for
a flow. Observations of service performance need to consider this a flow. Observations of service performance need to consider this
field when a network path has support for differentiated service field when a network path has support for differentiated service
treatment. treatment.
Use of Explicit Congestion Marking: ECN [RFC3168] is an optional Use of Explicit Congestion Marking: ECN [RFC3168] is an optional
transport mechanism that uses a code point in the network-layer transport mechanism that uses a code point in the network-layer
header. Use of ECN can offer gains in terms of increased header. Use of ECN can offer gains in terms of increased
throughput, reduced delay, and other benefits when used over a throughput, reduced delay, and other benefits when used over a
path that includes equipment that supports an AQM method that path that includes equipment that supports an AQM method that
performs Congestion Experienced (CE) marking of IP packets performs Congestion Experienced (CE) marking of IP packets
[RFC8087]. [RFC8087].
ECN exposes the presence of congestion on a network path to the ECN exposes the presence of congestion on a network path to the
transport and network layer. The reception of CE-marked packets transport and network layer. The reception of CE-marked packets
can therefore be used to monitor the presence and estimate the can therefore be used to monitor the presence and estimate the
level of incipient congestion on the upstream portion of the path level of incipient congestion on the upstream portion of the path
from the point of observation (Section 2.5 of [RFC8087]). Because from the point of observation (Section 2.5 of [RFC8087]). Because
ECN marks are carried in the IP protocol header, it is much easier ECN marks are carried in the IP protocol header, it is much easier
to measure ECN than to measure packet loss. However, interpreting to measure ECN than to measure packet loss. However, interpreting
the marking behaviour (i.e., assessing congestion and diagnosing the marking behaviour (i.e., assessing congestion and diagnosing
faults) requires context from the transport layer (path RTT, faults) requires context from the transport layer (path RTT,
visibility of loss - that could be due to queue overflow, visibility of loss - that could be due to queue overflow,
congestion response, etc) [RFC7567]. congestion response, etc) [RFC7567].
Some ECN-capable network devices can provide richer (more frequent Some ECN-capable network devices can provide richer (more frequent
and fine-grained) indication of their congestion state. Setting and fine-grained) indication of their congestion state. Setting
congestion marks proportional to the level of congestion (e.g., congestion marks proportional to the level of congestion (e.g.,
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ECN-enabled AQM-based networks [RFC8087]. ECN-enabled AQM-based networks [RFC8087].
AQM and ECN offer a range of algorithms and configuration options, AQM and ECN offer a range of algorithms and configuration options,
it is therefore important for tools to be available to network it is therefore important for tools to be available to network
operators and researchers to understand the implication of operators and researchers to understand the implication of
configuration choices and transport behaviour as use of ECN configuration choices and transport behaviour as use of ECN
increases and new methods emerge [RFC7567] [RFC8087]. ECN- increases and new methods emerge [RFC7567] [RFC8087]. ECN-
monitoring is expected to become important as AQM is deployed that monitoring is expected to become important as AQM is deployed that
supports ECN [RFC8087]. supports ECN [RFC8087].
2.2. Transport Measurement 3.2. Transport Measurement
The common language between network operators and application/content The common language between network operators and application/content
providers/users is packet transfer performance at a layer that all providers/users is packet transfer performance at a layer that all
can view and analyse. For most packets, this has been transport can view and analyse. For most packets, this has been transport
layer, until the emergence of QUIC, with the obvious exception of layer, until the emergence of QUIC, with the obvious exception of
Virtual Private Networks (VPNs) and IPsec. Virtual Private Networks (VPNs) and IPsec.
When encryption conceals more layers in each packet, people seeking When encryption conceals more layers in each packet, people seeking
understanding of the network operation rely more on pattern understanding of the network operation rely more on pattern
inferences and other heuristics reliance on pattern inferences and inferences and other heuristics reliance on pattern inferences and
accuracy suffers. For example, the traffic patterns between server accuracy suffers. For example, the traffic patterns between server
and browser are dependent on browser supplier and version, even when and browser are dependent on browser supplier and version, even when
the sessions use the same server application (e.g., web e-mail the sessions use the same server application (e.g., web e-mail
access). It remains to be seen whether more complex inferences can be access). It remains to be seen whether more complex inferences can
mastered to produce the same monitoring accuracy (see section 2.1.1 be mastered to produce the same monitoring accuracy (see section
of [I-D.mm-wg-effect-encrypt]). 2.1.1 of [RFC8404]).
When measurement datasets are made available by servers or client When measurement datasets are made available by servers or client
endpoints, additional metadata, such as the state of the network, is endpoints, additional metadata, such as the state of the network, is
often required to interpret this data. Collecting and coordinating often required to interpret this data. Collecting and coordinating
such metadata is more difficult when the observation point is at a such metadata is more difficult when the observation point is at a
different location to the bottleneck/device under evaluation. different location to the bottleneck/device under evaluation.
Packet sampling techniques can be used to scale the processing Packet sampling techniques can be used to scale the processing
involved in observing packets on high rate links. This exports only involved in observing packets on high rate links. This exports only
the packet header information of (randomly) selected packets. The the packet header information of (randomly) selected packets. The
utility of these measurements depends on the type of bearer and utility of these measurements depends on the type of bearer and
number of mechanisms used by network devices. Simple routers are number of mechanisms used by network devices. Simple routers are
relatively easy to manage, a device with more complexity demands relatively easy to manage, a device with more complexity demands
understanding of the choice of many system parameters. This level of understanding of the choice of many system parameters. This level of
complexity exists when several network methods are combined. complexity exists when several network methods are combined.
This section discusses topics concerning observation of transport This section discusses topics concerning observation of transport
flows, with a focus on transport measurement. flows, with a focus on transport measurement.
2.2.1. Point of Measurement 3.2.1. Point of Measurement
Often measurements can only be understood in the context of the other Often measurements can only be understood in the context of the other
flows that share a bottleneck. A simple example is monitoring of flows that share a bottleneck. A simple example is monitoring of
AQM. For example, FQ-CODEL [I-D.ietf-aqm-fq-codel], combines sub AQM. For example, FQ-CODEL [RFC8290], combines sub queues
queues (statistically assigned per flow), management of the queue (statistically assigned per flow), management of the queue length
length (CODEL), flow-scheduling, and a starvation prevention (CODEL), flow-scheduling, and a starvation prevention mechanism.
mechanism. Usually such algorithms are designed to be self-tuning, Usually such algorithms are designed to be self-tuning, but current
but current methods typically employ heuristics that can result in methods typically employ heuristics that can result in more loss
more loss under certain path conditions (e.g., large RTT, effects of under certain path conditions (e.g., large RTT, effects of multiple
multiple bottlenecks [RFC7567]). bottlenecks [RFC7567]).
In-network measurements can distinguish between upstream and In-network measurements can distinguish between upstream and
downstream metrics with respect to a measurement point. These are downstream metrics with respect to a measurement point. These are
particularly useful for locating the source of problems or to assess particularly useful for locating the source of problems or to assess
the performance of a network segment or a particular device the performance of a network segment or a particular device
configuration. By correlating observations of headers at multiple configuration. By correlating observations of headers at multiple
points along the path (e.g., at the ingress and egress of a network points along the path (e.g., at the ingress and egress of a network
segment), an observer can determine the contribution of a portion of segment), an observer can determine the contribution of a portion of
the path to an observed metric (to locate a source of delay, jitter, the path to an observed metric (to locate a source of delay, jitter,
loss, reordering, congestion marking, etc.). loss, reordering, congestion marking, etc.).
2.2.2. Use by Operators to Plan and Provision Networks 3.2.2. Use by Operators to Plan and Provision Networks
Traffic measurements (e.g., traffic volume, loss, latency) is used by Traffic measurements (e.g., traffic volume, loss, latency) is used by
operators to help plan deployment of new equipment and configurations operators to help plan deployment of new equipment and configurations
in their networks. Data is also important to equipment vendors who in their networks. Data is also important to equipment vendors who
need to understand traffic trends and patterns of usage as inputs to need to understand traffic trends and patterns of usage as inputs to
decisions about planning products and provisioning for new decisions about planning products and provisioning for new
deployments. This measurement information can also be correlated deployments. This measurement information can also be correlated
with billing information when this is also collected by an operator. with billing information when this is also collected by an operator.
A network operator supporting traffic that uses transport header A network operator supporting traffic that uses transport header
encryption may not have access to per-flow measurement data. Trends encryption may not have access to per-flow measurement data. Trends
in aggregate traffic can be observed and can be related to the in aggregate traffic can be observed and can be related to the
endpoint addresses being used, but it may not be possible to endpoint addresses being used, but it may not be possible to
correlate patterns in measurements with changes in transport correlate patterns in measurements with changes in transport
protocols (e.g., the impact of changes in introducing a new transport protocols (e.g., the impact of changes in introducing a new transport
protocol mechanism). This increases the dependency on other indirect protocol mechanism). This increases the dependency on other indirect
sources of information to inform planning and provisioning. sources of information to inform planning and provisioning.
2.2.3. Service Performance Measurement 3.2.3. Service Performance Measurement
Traffic measurements (e.g., traffic volume, loss, latency) can be Traffic measurements (e.g., traffic volume, loss, latency) can be
used by various actors to help analyse the performance offered to the used by various actors to help analyse the performance offered to the
users of a network segment, and inform operational practice. users of a network segment, and inform operational practice.
While active measurements may be used in-network, passive While active measurements may be used in-network, passive
measurements can have advantages in terms of eliminating unproductive measurements can have advantages in terms of eliminating unproductive
test traffic, reducing the influence of test traffic on the overall test traffic, reducing the influence of test traffic on the overall
traffic mix, and the ability to choose the point of measurement traffic mix, and the ability to choose the point of measurement
Section 2.2.1. However, passive measurements may rely on observing Section 3.2.1. However, passive measurements may rely on observing
transport headers. transport headers.
2.2.4. Measuring Transport to Support Network Operations 3.2.4. Measuring Transport to Support Network Operations
Information provided by tools observing transport headers can help Information provided by tools observing transport headers can help
determine whether mechanisms are needed in the network to prevent determine whether mechanisms are needed in the network to prevent
flows from acquiring excessive network capacity. Operators can flows from acquiring excessive network capacity. Operators can
implement operational practices to manage traffic flows (e.g., to implement operational practices to manage traffic flows (e.g., to
prevent flows from acquiring excessive network capacity under severe prevent flows from acquiring excessive network capacity under severe
congestion) by deploying rate-limiters, traffic shaping or network congestion) by deploying rate-limiters, traffic shaping or network
transport circuit breakers [RFC8084]. transport circuit breakers [RFC8084].
Congestion Control Compliance of Traffic: Congestion control is a key Congestion Control Compliance of Traffic: Congestion control is a
transport function [RFC2914]. Many network operators implicitly key transport function [RFC2914]. Many network operators
accept that TCP traffic to comply with a behaviour that is implicitly accept that TCP traffic to comply with a behaviour that
acceptable for use in the shared Internet. TCP algorithms have is acceptable for use in the shared Internet. TCP algorithms have
been continuously improved over decades, and they have reached a been continuously improved over decades, and they have reached a
level of efficiency and correctness that custom application-layer level of efficiency and correctness that custom application-layer
mechanisms will struggle to easily duplicate [RFC8085]. mechanisms will struggle to easily duplicate [RFC8085].
A standards-compliant TCP stack provides congestion control may A standards-compliant TCP stack provides congestion control may
therefore be judged safe for use across the Internet. therefore be judged safe for use across the Internet.
Applications developed on top of well-designed transports can be Applications developed on top of well-designed transports can be
expected to appropriately control their network usage, reacting expected to appropriately control their network usage, reacting
when the network experiences congestion, by back-off and reduce when the network experiences congestion, by back-off and reduce
the load placed on the network. This is the normal expected the load placed on the network. This is the normal expected
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congestion control behaviour. Analysing observed packet sequence congestion control behaviour. Analysing observed packet sequence
numbers can be used to help build confidence that an application numbers can be used to help build confidence that an application
flow backs-off its share of the network load in the face of flow backs-off its share of the network load in the face of
persistent congestion, and hence to understand whether the persistent congestion, and hence to understand whether the
behaviour is appropriate for sharing limited network capacity. behaviour is appropriate for sharing limited network capacity.
For example, it is common to visualise plots of TCP sequence For example, it is common to visualise plots of TCP sequence
numbers versus time for a flow to understand how a flow shares numbers versus time for a flow to understand how a flow shares
available capacity, deduce its dynamics in response to congestion, available capacity, deduce its dynamics in response to congestion,
etc. etc.
Congestion Control Compliance for UDP traffic UDP provides a minimal Congestion Control Compliance for UDP traffic UDP provides a minimal
message-passing datagram transport that has no inherent congestion message-passing datagram transport that has no inherent congestion
control mechanisms. Because congestion control is critical to the control mechanisms. Because congestion control is critical to the
stable operation of the Internet, applications and other protocols stable operation of the Internet, applications and other protocols
that choose to use UDP as a transport are required to employ that choose to use UDP as a transport are required to employ
mechanisms to prevent congestion collapse, avoid unacceptable mechanisms to prevent congestion collapse, avoid unacceptable
contributions to jitter/latency, and to establish an acceptable contributions to jitter/latency, and to establish an acceptable
share of capacity with concurrent traffic [RFC8085]. share of capacity with concurrent traffic [RFC8085].
A network operator needs tools to understand if datagram flows A network operator needs tools to understand if datagram flows
comply with congestion control expectations and therefore whether comply with congestion control expectations and therefore whether
there is a need to deploy methods such as rate-limiters, transport there is a need to deploy methods such as rate-limiters, transport
circuit breakers or other methods to enforce acceptable usage for circuit breakers or other methods to enforce acceptable usage for
the offered service. the offered service.
UDP flows that expose a well-known header by specifying the format UDP flows that expose a well-known header by specifying the format
of header fields can allow information to be observed to gain of header fields can allow information to be observed to gain
understanding of the dynamics of a flow and its congestion control understanding of the dynamics of a flow and its congestion control
behaviour. For example, tools exist to monitor various aspects of behaviour. For example, tools exist to monitor various aspects of
the RTP and RTCP header information of real-time flows (see the RTP and RTCP header information of real-time flows (see
Section 2.1.2. Section 3.1.2.
3.3. Use for Network Diagnostics and Troubleshooting
2.3. Use for Network Diagnostics and Troubleshooting
Transport header information can be useful for a variety of Transport header information can be useful for a variety of
operational tasks [I-D.mm-wg-effect-encrypt]: to diagnose network operational tasks [RFC8404]: to diagnose network problems, assess
problems, assess network provider performance, evaluate equipment/ network provider performance, evaluate equipment/protocol
protocol performance, capacity planning, management of security performance, capacity planning, management of security threats
threats (including denial of service), and responding to user (including denial of service), and responding to user performance
performance questions. Sections 3.1.2 and 5 of [I-D.mm-wg-effect- questions. Sections 3.1.2 and 5 of [RFC8404] provide further
encrypt] provide further examples. These tasks seldom involve the examples. These tasks seldom involve the need to determine the
need to determine the contents of the transport payload, or other contents of the transport payload, or other application details.
application details.
A network operator supporting traffic that uses transport header A network operator supporting traffic that uses transport header
encryption can see only encrypted transport headers. This prevents encryption can see only encrypted transport headers. This prevents
deployment of performance measurement tools that rely on transport deployment of performance measurement tools that rely on transport
protocol information. Choosing to encrypt all the information protocol information. Choosing to encrypt all the information
reduces the operator's ability to observe transport performance, and reduces the operator's ability to observe transport performance, and
may limit the ability of network operators to trace problems, make may limit the ability of network operators to trace problems, make
appropriate QoS decisions, or response to other queries about the appropriate QoS decisions, or response to other queries about the
network service. For some this will be blessing, for others it may network service. For some this will be blessing, for others it may
be a curse. For example, operational performance data about be a curse. For example, operational performance data about
encrypted flows needs to be determined by traffic pattern analysis, encrypted flows needs to be determined by traffic pattern analysis,
rather than relying on traditional tools. This can impact the rather than relying on traditional tools. This can impact the
ability of the operator to respond to faults, it could require ability of the operator to respond to faults, it could require
reliance on endpoint diagnostic tools or user involvement in reliance on endpoint diagnostic tools or user involvement in
diagnosing and troubleshooting unusual use cases or non-trivial diagnosing and troubleshooting unusual use cases or non-trivial
problems. A key need here is for tools to provide useful information problems. A key need here is for tools to provide useful information
during network anomalies (e.g., significant reordering, high or during network anomalies (e.g., significant reordering, high or
intermittent loss). Although many network operators utilise transport intermittent loss). Although many network operators utilise
information as a part of their operational practice, the network will transport information as a part of their operational practice, the
not break because transport headers are encrypted, and this may network will not break because transport headers are encrypted, and
require alternative tools may need to be developed and deployed. this may require alternative tools may need to be developed and
deployed.
2.3.1. Examples of measurements 3.3.1. Examples of measurements
Measurements can be used to monitor the health of a portion of the Measurements can be used to monitor the health of a portion of the
Internet, to provide early warning of the need to take action. They Internet, to provide early warning of the need to take action. They
can assist in debugging and diagnosing the root causes of faults that can assist in debugging and diagnosing the root causes of faults that
concern a particular user's traffic. They can also be used to concern a particular user's traffic. They can also be used to
support post-mortem investigation after an anomaly to determine the support post-mortem investigation after an anomaly to determine the
root cause of a problem. root cause of a problem.
In some case, measurements may involve active injection of test In some case, measurements may involve active injection of test
traffic to complete a measurement. However, most operators do not traffic to complete a measurement. However, most operators do not
have access to user equipment, and injection of test traffic may be have access to user equipment, and injection of test traffic may be
associated with costs in running such tests (e.g., the implications associated with costs in running such tests (e.g., the implications
of bandwidth tests in a mobile network are obvious). Some active of bandwidth tests in a mobile network are obvious). Some active
measurements (e.g., response under load or particular workloads) measurements (e.g., response under load or particular workloads)
perturb other traffic, and could require dedicated access to the perturb other traffic, and could require dedicated access to the
network segment. An alternative approach is to use in-network network segment. An alternative approach is to use in-network
techniques that observe transport packet headers in operational techniques that observe transport packet headers in operational
networks to make the measurements. networks to make the measurements.
In other cases, measurement involves dissecting network traffic In other cases, measurement involves dissecting network traffic
flows. The observed transport layer information can help identify flows. The observed transport layer information can help identify
whether the link/network tuning is effective and alert to potential whether the link/network tuning is effective and alert to potential
problems that can be hard to derive from link or device measurements problems that can be hard to derive from link or device measurements
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to-point radio) has the complexity of a subsystem that performs radio to-point radio) has the complexity of a subsystem that performs radio
resource management,s with direct impact on the available capacity, resource management,s with direct impact on the available capacity,
and potentially loss/reordering of packets. The impact of the and potentially loss/reordering of packets. The impact of the
pattern of loss and congestion, differs for different traffic types, pattern of loss and congestion, differs for different traffic types,
correlation with propagation and interference can all have correlation with propagation and interference can all have
significant impact on the cost and performance of a provided service. significant impact on the cost and performance of a provided service.
The need for this type of information is expected to increase as The need for this type of information is expected to increase as
operators bring together heterogeneous types of network equipment and operators bring together heterogeneous types of network equipment and
seek to deploy opportunistic methods to access radio spectrum. seek to deploy opportunistic methods to access radio spectrum.
2.4. Observing Headers to Implement Network Policy 3.4. Observing Headers to Implement Network Policy
Information from the transport protocol can be used by a multi-field Information from the transport protocol can be used by a multi-field
classifier as a part of policy framework. Policies are commonly used classifier as a part of policy framework. Policies are commonly used
for management of the QoS or Quality of Experience (QoE) in resource- for management of the QoS or Quality of Experience (QoE) in resource-
constrained networks and by firewalls that use the information to constrained networks and by firewalls that use the information to
implement access rules (see also section 2.2.2 of [I-D.mm-wg-effect- implement access rules (see also section 2.2.2 of [RFC8404]).
encrypt]). Traffic that cannot be classified, will typically receive Traffic that cannot be classified, will typically receive a default
a default treatment. treatment.
3. Encryption and Authentication of Transport Headers 4. Encryption and Authentication of Transport Headers
End-to-end encryption can be applied at various protocol layers. It End-to-end encryption can be applied at various protocol layers. It
can be applied above the transport to encrypt the transport payload. can be applied above the transport to encrypt the transport payload.
Encryption methods can hide information from an eavesdropper in the Encryption methods can hide information from an eavesdropper in the
network. Encryption can also help protect the privacy of a user, by network. Encryption can also help protect the privacy of a user, by
hiding data relating to user/device identity or location. Neither an hiding data relating to user/device identity or location. Neither an
integrity check nor encryption methods prevent traffic analysis, and integrity check nor encryption methods prevent traffic analysis, and
usage needs to reflect that profiling of users, identification of usage needs to reflect that profiling of users, identification of
location and fingerprinting of behaviour can take place even on location and fingerprinting of behaviour can take place even on
encrypted traffic flows. encrypted traffic flows.
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There are several motivations: There are several motivations:
o One motive to use encryption is a response to perceptions that the o One motive to use encryption is a response to perceptions that the
network has become ossified by over-reliance on middleboxes that network has become ossified by over-reliance on middleboxes that
prevent new protocols and mechanisms from being deployed. This prevent new protocols and mechanisms from being deployed. This
has lead to a perception that there is too much "manipulation" of has lead to a perception that there is too much "manipulation" of
protocol headers within the network, and that designing to deploy protocol headers within the network, and that designing to deploy
in such networks is preventing transport evolution. In the light in such networks is preventing transport evolution. In the light
of this, a method that authenticates transport headers may help of this, a method that authenticates transport headers may help
improve the pace of transport development, by eliminating the need improve the pace of transport development, by eliminating the need
to always consider deployed middleboxes [I-D.trammell-plus- to always consider deployed middleboxes
abstract-mech], or potentially to only explicitly enable middlebox [I-D.trammell-plus-abstract-mech], or potentially to only
use for particular paths with particular middleboxes that are explicitly enable middlebox use for particular paths with
deliberately deployed to realise a useful function for the network particular middleboxes that are deliberately deployed to realise a
and/or users[RFC3135]. useful function for the network and/or users[RFC3135].
o Another motivation stems from increased concerns about privacy and o Another motivation stems from increased concerns about privacy and
surveillance. Some Internet users have valued the ability to surveillance. Some Internet users have valued the ability to
protect identity, user location, and defend against traffic protect identity, user location, and defend against traffic
analysis, and have used methods such as IPsec Encapsulated analysis, and have used methods such as IPsec Encapsulated
Security Payload (ESP), Virtual Private Networks (VPNs) and other Security Payload (ESP), Virtual Private Networks (VPNs) and other
encrypted tunnel technologies. Revelations about the use of encrypted tunnel technologies. Revelations about the use of
pervasive surveillance [RFC7624] have, to some extent, eroded pervasive surveillance [RFC7624] have, to some extent, eroded
trust in the service offered by network operators, and following trust in the service offered by network operators, and following
the Snowden revelation in the USA in 2013 has led to an increased the Snowden revelation in the USA in 2013 has led to an increased
desire for people to employ encryption to avoid unwanted desire for people to employ encryption to avoid unwanted
"eavesdropping" on their communications. Concerns have also been "eavesdropping" on their communications. Concerns have also been
voiced about the addition of information to packets by third voiced about the addition of information to packets by third
parties to provide analytics, customization, advertising, cross- parties to provide analytics, customization, advertising, cross-
site tracking of users, to bill the customer, or to selectively site tracking of users, to bill the customer, or to selectively
allow or block content. Whatever the reasons, there are now allow or block content. Whatever the reasons, there are now
activities in the IETF to design new protocols that may include activities in the IETF to design new protocols that may include
some form of transport header encryption (e.g., QUIC [I-D.ietf- some form of transport header encryption (e.g., QUIC
quic-transport]). [I-D.ietf-quic-transport]).
Authentication methods (that provide integrity checks of protocols Authentication methods (that provide integrity checks of protocols
fields) have also been specified at the network layer, and this also fields) have also been specified at the network layer, and this also
protects transport header fields. The network layer itself carries protects transport header fields. The network layer itself carries
protocol header fields that are increasingly used to help forwarding protocol header fields that are increasingly used to help forwarding
decisions reflect the need of transport protocols, such as the IPv6 decisions reflect the need of transport protocols, such as the IPv6
Flow Label [RFC6437], the DSCP and ECN. Flow Label [RFC6437], the DSCP and ECN.
The use of transport layer authentication and encryption exposes a The use of transport layer authentication and encryption exposes a
tussle between middlebox vendors, operators, applications developers tussle between middlebox vendors, operators, applications developers
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Whatever the motives, a decision to use pervasive of transport header Whatever the motives, a decision to use pervasive of transport header
encryption will have implications on the way in which design and encryption will have implications on the way in which design and
evaluation is performed, and which can in turn impact the direction evaluation is performed, and which can in turn impact the direction
of evolution of the TCP/IP stack. While the IETF can specify of evolution of the TCP/IP stack. While the IETF can specify
protocols, the success in actual deployment is often determined by protocols, the success in actual deployment is often determined by
many factors [RFC5218] that are not always clear at the time when many factors [RFC5218] that are not always clear at the time when
protocols are being defined. protocols are being defined.
The next subsections briefly review some security design options for The next subsections briefly review some security design options for
transport protocols. A Survey of Transport Security Protocols [I-D transport protocols. A Survey of Transport Security Protocols
.ietf-taps-transport-security] provides more details concerning [I-D.ietf-taps-transport-security] provides more details concerning
commonly used encryption methods at the transport layer. commonly used encryption methods at the transport layer.
3.1. Authenticating the Transport Protocol Header 4.1. Authenticating the Transport Protocol Header
Transport layer header information can be authenticated. An Transport layer header information can be authenticated. An
integrity check that protects the immutable transport header fields, integrity check that protects the immutable transport header fields,
but can still expose the transport protocol header information in the but can still expose the transport protocol header information in the
clear, allowing in-network devices to observes these fields. An clear, allowing in-network devices to observes these fields. An
integrity check can not prevent in-network modification, but can integrity check can not prevent in-network modification, but can
avoid a receiving accepting changes and avoid impact on the transport avoid a receiving accepting changes and avoid impact on the transport
protocol operation. protocol operation.
An example transport authentication mechanism is TCP-Authentication An example transport authentication mechanism is TCP-Authentication
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header, TCP header, and TCP data. TCP-AO protects the transport header, TCP header, and TCP data. TCP-AO protects the transport
layer, preventing attacks from disabling the TCP connection itself layer, preventing attacks from disabling the TCP connection itself
and provides replay protection. TCP-AO may interact with and provides replay protection. TCP-AO may interact with
middleboxes, depending on their behaviour [RFC3234]. middleboxes, depending on their behaviour [RFC3234].
The IPsec Authentication Header (AH) [RFC4302] was designed to work The IPsec Authentication Header (AH) [RFC4302] was designed to work
at the network layer and authenticate the IP payload. This approach at the network layer and authenticate the IP payload. This approach
authenticates all transport headers, and verifies their integrity at authenticates all transport headers, and verifies their integrity at
the receiver, preventing in-network modification. the receiver, preventing in-network modification.
3.2. Encrypting the Transport Payload 4.2. Encrypting the Transport Payload
The transport layer payload can be encrypted to protect the content The transport layer payload can be encrypted to protect the content
of transport segments. This leaves transport protocol header of transport segments. This leaves transport protocol header
information in the clear. The integrity of immutable transport information in the clear. The integrity of immutable transport
header fields could be protected by combining this with an integrity header fields could be protected by combining this with an integrity
check (Section 3.1). check (Section 4.1).
Examples of encrypting the payload include Transport Layer Security Examples of encrypting the payload include Transport Layer Security
(TLS) over TCP [RFC5246] [RFC7525], Datagram TLS (DTLS) over UDP (TLS) over TCP [RFC5246] [RFC7525], Datagram TLS (DTLS) over UDP
[RFC6347] [RFC7525], and TCPcrypt [I-D.ietf-tcpinc-tcpcrypt], which [RFC6347] [RFC7525], and TCPcrypt [I-D.ietf-tcpinc-tcpcrypt], which
permits opportunistic encryption of the TCP transport payload. permits opportunistic encryption of the TCP transport payload.
3.3. Encrypting the Transport Header 4.3. Encrypting the Transport Header
The network layer payload could be encrypted (including the entire The network layer payload could be encrypted (including the entire
transport header and the payload). This method provides transport header and the payload). This method provides
confidentiality of the entire transport packet. It therefore does confidentiality of the entire transport packet. It therefore does
not expose any transport information to devices in the network, which not expose any transport information to devices in the network, which
also prevents modification along a network path. also prevents modification along a network path.
One example of encryption at the network layer is use of IPsec One example of encryption at the network layer is use of IPsec
Encapsulating Security Payload (ESP) [RFC4303] in tunnel mode. This Encapsulating Security Payload (ESP) [RFC4303] in tunnel mode. This
encrypts and authenticates all transport headers, preventing encrypts and authenticates all transport headers, preventing
visibility of the transport headers by in-network devices. Some visibility of the transport headers by in-network devices. Some
Virtual Private Network (VPN) methods also encrypt these headers. Virtual Private Network (VPN) methods also encrypt these headers.
3.4. Authenticating Transport Information and Selectively Encrypting 4.4. Authenticating Transport Information and Selectively Encrypting
the Transport Header the Transport Header
A transport protocol design can encrypt selected header fields, while A transport protocol design can encrypt selected header fields, while
also choosing to authenticate fields in the transport header. This also choosing to authenticate fields in the transport header. This
allows specific transport header fields to be made observable by allows specific transport header fields to be made observable by
network devices. End-to end integrity checks can prevent an endpoint network devices. End-to end integrity checks can prevent an endpoint
from undetected modification of the immutable transport headers. from undetected modification of the immutable transport headers.
Mutable fields in the transport header provide opportunities for Mutable fields in the transport header provide opportunities for
middleboxes to modify the transport behaviour (e.g., the extended middleboxes to modify the transport behaviour (e.g., the extended
headers described in [I-D.trammell-plus-abstract-mech]). This headers described in [I-D.trammell-plus-abstract-mech]). This
considers only immutable fields in the transport headers, that is, considers only immutable fields in the transport headers, that is,
fields that may be authenticated End-to-End across a path. fields that may be authenticated End-to-End across a path.
An example of a method that encrypts some, but not all, transport An example of a method that encrypts some, but not all, transport
information is GRE-in-UDP [RFC8086] when used with GRE encryption. information is GRE-in-UDP [RFC8086] when used with GRE encryption.
3.5. Optional Encryption of Header Information 4.5. Optional Encryption of Header Information
There are implications to the use of optional header encryption in There are implications to the use of optional header encryption in
the design of a transport protocol, where support of optional the design of a transport protocol, where support of optional
mechanisms can increase the complexity of the protocol and its mechanisms can increase the complexity of the protocol and its
implementation and in the management decisions that are required to implementation and in the management decisions that are required to
use variable format fields. Instead, fields of a specific type ought use variable format fields. Instead, fields of a specific type ought
to always be sent with the same level of confidentiality or integrity to always be sent with the same level of confidentiality or integrity
protection. protection.
4. Addition of Transport Information to Network-Layer Protocol Headers 5. Addition of Transport Information to Network-Layer Protocol Headers
Transport protocol information can be made visible in a network-layer Transport protocol information can be made visible in a network-layer
header. This has the advantage that this information can then be header. This has the advantage that this information can then be
observed by in-network devices. This has the advantage that a single observed by in-network devices. This has the advantage that a single
header can support all transport protocols, but there may also be header can support all transport protocols, but there may also be
less desirable implications of separating the operation of the less desirable implications of separating the operation of the
transport protocol from the measurement framework. transport protocol from the measurement framework.
Some measurements may be made by adding additional protocol headers Some measurements may be made by adding additional protocol headers
carrying operations, administration and management (OAM) information carrying operations, administration and management (OAM) information
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a method such as 802.11ag or in-situ OAM [I-D.ietf-ippm-ioam-data]) a method such as 802.11ag or in-situ OAM [I-D.ietf-ippm-ioam-data])
and removing the additional header at the egress of the maintenance and removing the additional header at the egress of the maintenance
domain. This approach enables some types of measurements, but does domain. This approach enables some types of measurements, but does
not cover the entire range of measurements described in this not cover the entire range of measurements described in this
document. In some cases, it can be difficult to position measurement document. In some cases, it can be difficult to position measurement
tools at the required segments/nodes and there can be challenges in tools at the required segments/nodes and there can be challenges in
correlating the downsream/upstream information when in-band OAM data correlating the downsream/upstream information when in-band OAM data
is inserted by an on-path device. is inserted by an on-path device.
Another example of a network-layer approach is the IPv6 Performance Another example of a network-layer approach is the IPv6 Performance
and Diagnostic Metrics (PDM) Destination Option [I-D.ietf-ippm-6man- and Diagnostic Metrics (PDM) Destination Option [RFC8250]. This
pdm-option]. This allows a sender to optionally include a allows a sender to optionally include a destination option that
destination option that caries header fields that can be used to caries header fields that can be used to observe timestamps and
observe timestamps and packet sequence numbers. This information packet sequence numbers. This information could be authenticated by
could be authenticated by receiving transport endpoints when the receiving transport endpoints when the information is added at the
information is added at the sender and visible at the receiving sender and visible at the receiving endpoint, although methods to do
endpoint, although methods to do this have not currently been this have not currently been proposed. This method needs to be
proposed. This method needs to be explicitly enabled at the sender. explicitly enabled at the sender.
It can be undesirable to rely on methods requiring the presence of It can be undesirable to rely on methods requiring the presence of
network options or extension headers. IPv4 network options are often network options or extension headers. IPv4 network options are often
not supported (or are carried on a slower processing path) and some not supported (or are carried on a slower processing path) and some
IPv6 networks are also known to drop packets that set an IPv6 header IPv6 networks are also known to drop packets that set an IPv6 header
extension (e.g., [RFC7872]). Another disadvantage is that protocols extension (e.g., [RFC7872]). Another disadvantage is that protocols
that separately expose header information do not necessarily have an that separately expose header information do not necessarily have an
advantage to expose the information that is utilised by the protocol advantage to expose the information that is utilised by the protocol
itself, and could manipulate this header information to gain an itself, and could manipulate this header information to gain an
advantage from the network. advantage from the network.
5. Implications of Protecting the Transport Headers 6. Implications of Protecting the Transport Headers
The choice of which fields to expose and which to encrypt is a design The choice of which fields to expose and which to encrypt is a design
choice for the transport protocol. Any selective encryption method choice for the transport protocol. Any selective encryption method
requires trading two conflicting goals for a transport protocol requires trading two conflicting goals for a transport protocol
designer to decide which header fields to encrypt. Security work designer to decide which header fields to encrypt. Security work
typically employs a design technique that seeks to expose only what typically employs a design technique that seeks to expose only what
is needed. However, there can be performance and operational is needed. However, there can be performance and operational
benefits in exposing selected information to network tools. benefits in exposing selected information to network tools.
This section explores key implications of working with encrypted This section explores key implications of working with encrypted
transport protocols. transport protocols.
5.1. Independent Measurement 6.1. Independent Measurement
Independent observation by multiple actors is important for Independent observation by multiple actors is important for
scientific analysis. Encrypting transport header encryption changes scientific analysis. Encrypting transport header encryption changes
the ability for other actors to collect and independently analyse the ability for other actors to collect and independently analyse
data. Internet transport protocols employ a set of mechanisms. Some data. Internet transport protocols employ a set of mechanisms. Some
of these need to work in cooperation with the network layer - loss of these need to work in cooperation with the network layer - loss
detection and recovery, congestion detection and congestion control, detection and recovery, congestion detection and congestion control,
some of these need to work only End-to-End (e.g., parameter some of these need to work only End-to-End (e.g., parameter
negotiation, flow-control). negotiation, flow-control).
When encryption conceals information in the transport header, it When encryption conceals information in the transport header, it
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information. Protocols that expose the state information used by the information. Protocols that expose the state information used by the
transport protocol in their header information (e.g., timestamps used transport protocol in their header information (e.g., timestamps used
to calculate the RTT, packet numbers used to asses congestion and to calculate the RTT, packet numbers used to asses congestion and
requests for retransmission) provide an incentive for the sending requests for retransmission) provide an incentive for the sending
endpoint to provide correct information, increasing confidence that endpoint to provide correct information, increasing confidence that
the observer understands the transport interaction with the network. the observer understands the transport interaction with the network.
This becomes important when considering changes to transport This becomes important when considering changes to transport
protocols, changes in network infrastructure, or the emergence of new protocols, changes in network infrastructure, or the emergence of new
traffic patterns. traffic patterns.
5.2. Characterising "Unknown" Network Traffic 6.2. Characterising "Unknown" Network Traffic
The patterns and types of traffic that share Internet capacity The patterns and types of traffic that share Internet capacity
changes with time as networked applications, usage patterns and changes with time as networked applications, usage patterns and
protocols continue to evolve. protocols continue to evolve.
If "unknown" or "uncharacterised" traffic patterns form a small part If "unknown" or "uncharacterised" traffic patterns form a small part
of the traffic aggregate passing through a network device or segment of the traffic aggregate passing through a network device or segment
of the network the path, the dynamics of the uncharacterised traffic of the network the path, the dynamics of the uncharacterised traffic
may not have a significant collateral impact on the performance of may not have a significant collateral impact on the performance of
other traffic that shares this network segment. Once the proportion other traffic that shares this network segment. Once the proportion
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of the traffic aggregate passing through a network device or segment of the traffic aggregate passing through a network device or segment
of the network the path, the dynamics of the uncharacterised traffic of the network the path, the dynamics of the uncharacterised traffic
may not have a significant collateral impact on the performance of may not have a significant collateral impact on the performance of
other traffic that shares this network segment. Once the proportion other traffic that shares this network segment. Once the proportion
of this traffic increases, the need to monitor the traffic and of this traffic increases, the need to monitor the traffic and
determine if appropriate safety measures need to be put in place. determine if appropriate safety measures need to be put in place.
Tracking the impact of new mechanisms and protocols requires traffic Tracking the impact of new mechanisms and protocols requires traffic
volume to be measured and new transport behaviours to be identified. volume to be measured and new transport behaviours to be identified.
This is especially true of protocols operating over a UDP substrate. This is especially true of protocols operating over a UDP substrate.
The level and style of encryption needs to be considered in The level and style of encryption needs to be considered in
determining how this activity is performed. On a shorter timescale, determining how this activity is performed. On a shorter timescale,
information may also need to be collected to manage denial of service information may also need to be collected to manage denial of service
attacks against the infrastructure. attacks against the infrastructure.
5.3. Accountability and Internet Transport Protocols 6.3. Accountability and Internet Transport Protocols
Information provided by tools observing transport headers can be used Information provided by tools observing transport headers can be used
to classify traffic, and to limit the network capacity used by to classify traffic, and to limit the network capacity used by
certain flows. Operators can potentially use this information to certain flows. Operators can potentially use this information to
prioritise or de-prioritise certain flows or classes of flow, with prioritise or de-prioritise certain flows or classes of flow, with
potential implications for network neutrality, or to rate limit potential implications for network neutrality, or to rate limit
malicious or otherwise undesirable flows (e.g., for Distributed malicious or otherwise undesirable flows (e.g., for Distributed
Denial of Service, DDOS, protection, or to ensure compliance with a Denial of Service, DDOS, protection, or to ensure compliance with a
traffic profile Section 2.2.4). Equally, operators could use analysis traffic profile Section 3.2.4). Equally, operators could use
of transport headers and transport flow state to demonstrate that analysis of transport headers and transport flow state to demonstrate
they are not providing differential treatment to certain flows. that they are not providing differential treatment to certain flows.
Obfuscating or hiding this information using encryption is expected Obfuscating or hiding this information using encryption is expected
to lead operators and maintainers of middleboxes (firewalls, etc.) to to lead operators and maintainers of middleboxes (firewalls, etc.) to
seek other methods to classify, and potentially other mechanisms to seek other methods to classify, and potentially other mechanisms to
condition, network traffic. condition, network traffic.
A lack of data reduces the level of precision with which flows can be A lack of data reduces the level of precision with which flows can be
classified and conditioning mechanisms are applied (e.g., rate classified and conditioning mechanisms are applied (e.g., rate
limiting, circuit breaker techniques [RFC8084], or blocking of limiting, circuit breaker techniques [RFC8084], or blocking of
uncharacterised traffic), and this needs to be considered when uncharacterised traffic), and this needs to be considered when
evaluating the impact of designs for transport encryption [RFC5218]. evaluating the impact of designs for transport encryption [RFC5218].
5.4. Impact on Research, Development and Deployment 6.4. Impact on Research, Development and Deployment
The majority of present Internet applications use two well-known The majority of present Internet applications use two well-known
transport protocols: e.g., TCP and UDP. Although TCP represents the transport protocols: e.g., TCP and UDP. Although TCP represents the
majority of current traffic, some important real-time applications majority of current traffic, some important real-time applications
use UDP, and much of this traffic utilises RTP format headers in the use UDP, and much of this traffic utilises RTP format headers in the
payload of the UDP datagram. Since these protocol headers have been payload of the UDP datagram. Since these protocol headers have been
fixed for decades, a range of tools and analysis methods have became fixed for decades, a range of tools and analysis methods have became
common and well-understood. Over this period, the transport protocol common and well-understood. Over this period, the transport protocol
headers have mostly changed slowly, and so also the need to develop headers have mostly changed slowly, and so also the need to develop
tools track new versions of the protocol. tools track new versions of the protocol.
Looking ahead, there will be a need to update these protocols and to Looking ahead, there will be a need to update these protocols and to
develop and deploy new transport mechanisms and protocols. There are develop and deploy new transport mechanisms and protocols. There are
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opportunity for greater freedom to update the protocols and can ease opportunity for greater freedom to update the protocols and can ease
experimentation with new techniques and their final deployment in experimentation with new techniques and their final deployment in
endpoints. endpoints.
Hiding headers can limit the ability to measure and characterise Hiding headers can limit the ability to measure and characterise
traffic. Measurement data is increasingly being used to inform traffic. Measurement data is increasingly being used to inform
design decisions in networking research, during development of new design decisions in networking research, during development of new
mechanisms and protocols and in standardisation. Measurement has a mechanisms and protocols and in standardisation. Measurement has a
critical role in the design of transport protocol mechanisms and critical role in the design of transport protocol mechanisms and
their acceptance by the wider community (e.g., as a method to judge their acceptance by the wider community (e.g., as a method to judge
the safety for Internet deployment). Observation of pathologies are the safety for Internet deployment). Observation of pathologies are
also important in understanding the interactions between cooperating also important in understanding the interactions between cooperating
protocols and network mechanism, the implications of sharing capacity protocols and network mechanism, the implications of sharing capacity
with other traffic and the impact of different patterns of usage. with other traffic and the impact of different patterns of usage.
Evolution and the ability to understand (measure) the impact need to Evolution and the ability to understand (measure) the impact need to
proceed hand-in-hand. Attention needs to be paid to the expected proceed hand-in-hand. Attention needs to be paid to the expected
scale of deployment of new protocols and protocol mechanisms. scale of deployment of new protocols and protocol mechanisms.
Whatever the mechanism, experience has shown that it is often Whatever the mechanism, experience has shown that it is often
difficult to correctly implement combination of mechanisms [RFC8085]. difficult to correctly implement combination of mechanisms [RFC8085].
These mechanisms therefore typically evolve as a protocol matures, or These mechanisms therefore typically evolve as a protocol matures, or
skipping to change at page 27, line 11 skipping to change at page 27, line 23
a body of data reflecting its behaviour under a wide range of a body of data reflecting its behaviour under a wide range of
deployment scenarios, traffic load, and interactions with other deployment scenarios, traffic load, and interactions with other
deployed/candidate methods. deployed/candidate methods.
Open standards motivate a desire for this evaluation to include Open standards motivate a desire for this evaluation to include
independent observation and evaluation of performance data, which in independent observation and evaluation of performance data, which in
turn suggests control over where and when measurement samples are turn suggests control over where and when measurement samples are
collected. This requires consideration of the appropriate balance collected. This requires consideration of the appropriate balance
between encrypting all and no transport information. between encrypting all and no transport information.
6. Conclusions 7. Conclusions
The majority of present Internet applications use two well-known The majority of present Internet applications use two well-known
transport protocols: e.g., TCP and UDP. Although TCP represents the transport protocols: e.g., TCP and UDP. Although TCP represents the
majority of current traffic, some important real-time applications majority of current traffic, some important real-time applications
have used UDP, and much of this traffic utilises RTP format headers have used UDP, and much of this traffic utilises RTP format headers
in the payload of the UDP datagram. Since these protocol headers in the payload of the UDP datagram. Since these protocol headers
have been fixed for decades, a range of tools and analysis methods have been fixed for decades, a range of tools and analysis methods
have became common and well-understood. Over this period, the have became common and well-understood. Over this period, the
transport protocol headers have mostly changed slowly, and so also transport protocol headers have mostly changed slowly, and so also
the need to develop tools track new versions of the protocol. the need to develop tools track new versions of the protocol.
Confidentiality and strong integrity checks have properties that are Confidentiality and strong integrity checks have properties that are
being incorporated into new protocols and which have important being incorporated into new protocols and which have important
skipping to change at page 28, line 13 skipping to change at page 28, line 19
appropriate operational support functions and procedures. appropriate operational support functions and procedures.
Protocols that change their transport header format (wire format) or Protocols that change their transport header format (wire format) or
their behaviour (e.g., algorithms that are needed to classify and their behaviour (e.g., algorithms that are needed to classify and
characterise the protocol), will require new tooling needs to be characterise the protocol), will require new tooling needs to be
developed to catch-up with the changes. If the currently deployed developed to catch-up with the changes. If the currently deployed
tools and methods are no longer relevant and performance may not be tools and methods are no longer relevant and performance may not be
correctly measured. This can increase the response-time after correctly measured. This can increase the response-time after
faults, and can impact the ability to manage the network resulting in faults, and can impact the ability to manage the network resulting in
traffic causing traffic to be treated inappropriately (e.g., rate traffic causing traffic to be treated inappropriately (e.g., rate
limiting because of being incorrectly classified/monitored). There limiting because of being incorrectly classified/monitored). There
are benefits in exposing consistent information to the network that are benefits in exposing consistent information to the network that
avoids traffic being mis-classified and then receiving a default avoids traffic being mis-classified and then receiving a default
treatment by the network. treatment by the network.
As a part of its design a new protocol specification therefore needs As a part of its design a new protocol specification therefore needs
to weigh the benefits of ossifying common headers, versus the to weigh the benefits of ossifying common headers, versus the
potential demerits of exposing specific information that could be potential demerits of exposing specific information that could be
observed along the network path to provide tools to manage new observed along the network path to provide tools to manage new
variants of protocols. Several scenarios to illustrate different variants of protocols. Several scenarios to illustrate different
ways this could evolve are provided below: ways this could evolve are provided below:
skipping to change at page 28, line 38 skipping to change at page 28, line 44
between versions of the protocol. This ossification of the between versions of the protocol. This ossification of the
transport header allows an operator to establish tooling and transport header allows an operator to establish tooling and
procedures that enable it to provide consistent traffic management procedures that enable it to provide consistent traffic management
as the protocol evolves. In contrast to TCP (where all protocol as the protocol evolves. In contrast to TCP (where all protocol
information is exposed), evolution of the transport is facilitated information is exposed), evolution of the transport is facilitated
by providing cryptographic integrity checks of the transport by providing cryptographic integrity checks of the transport
header fields (preventing undetected middlebox changes) and header fields (preventing undetected middlebox changes) and
encryption of other protocol information (preventing observation encryption of other protocol information (preventing observation
within the network, or incentivising the use of the exposed within the network, or incentivising the use of the exposed
information, rather than inferring information from other information, rather than inferring information from other
characteristics of the flow traffic). The exposed transport characteristics of the flow traffic). The exposed transport
information can be used by operators to provide troubleshooting, information can be used by operators to provide troubleshooting,
measurement and any necessary functions appropriate to the class measurement and any necessary functions appropriate to the class
of traffic (priority, retransmission, reordering, circuit of traffic (priority, retransmission, reordering, circuit
breakers, etc). breakers, etc).
o An alternative scenario adopts different design goals, with a o An alternative scenario adopts different design goals, with a
different outcome. A protocol that encrypts all header different outcome. A protocol that encrypts all header
information forces network operators to act independently from information forces network operators to act independently from
apps/transport developments to provide the transport information apps/transport developments to provide the transport information
they need. A range of approaches may proliferate, as in current they need. A range of approaches may proliferate, as in current
skipping to change at page 29, line 40 skipping to change at page 29, line 36
actors (e.g., developers and transport designers) achieve more actors (e.g., developers and transport designers) achieve more
control of the way in which the Internet architecture develops.In control of the way in which the Internet architecture develops.In
particular, there is a possibility that designs could evolve to particular, there is a possibility that designs could evolve to
significantly benefit of customers for a specific vendor, and that significantly benefit of customers for a specific vendor, and that
communities with very different network, applications or platforms communities with very different network, applications or platforms
could then suffer at the expense of benefits to their vendors own could then suffer at the expense of benefits to their vendors own
customer base. In such a scenario, there could be no incentive to customer base. In such a scenario, there could be no incentive to
support other applications/products or to work in other networks support other applications/products or to work in other networks
leading to reduced access for new approaches. leading to reduced access for new approaches.
7. Acknowledgements
The authors would like to thank all who have talked to him face-to-
face or via email. ...
This work has received funding from the European Union's Horizon 2020
research and innovation programme under grant agreement No 688421.The
opinions expressed and arguments employed reflect only the authors'
view. The European Commission is not responsible for any use that
may be made of that information.
8. Security Considerations 8. Security Considerations
This document is about design and deployment considerations for This document is about design and deployment considerations for
transport protocols. Issues relating to security are discussed in transport protocols. Issues relating to security are discussed in
the various sections of the document. the various sections of the document.
Authentication, confidentiality protection, and integrity protection Authentication, confidentiality protection, and integrity protection
are identified as Transport Features by [RFC8095]. As currently are identified as Transport Features by [RFC8095]. As currently
deployed in the Internet, these features are generally provided by a deployed in the Internet, these features are generally provided by a
protocol or layer on top of the transport protocol [I-D.ietf-taps- protocol or layer on top of the transport protocol
transport-security]. [I-D.ietf-taps-transport-security].
Confidentiality and strong integrity checks have properties that can Confidentiality and strong integrity checks have properties that can
also be incorporated into the deisgn of a transport protocol. also be incorporated into the deisgn of a transport protocol.
Integrity checks can protect an endpoint from undetected modification Integrity checks can protect an endpoint from undetected modification
of protocol fields by network devices, whereas encryption and of protocol fields by network devices, whereas encryption and
obfuscation can further prevent these headers being utilised by obfuscation can further prevent these headers being utilised by
network devices. Hiding headers can therefore provide the network devices. Hiding headers can therefore provide the
opportunity for greater freedom to update the protocols and can ease opportunity for greater freedom to update the protocols and can ease
experimentation with new techniques and their final deployment in experimentation with new techniques and their final deployment in
endpoints. A protocol specification needs to weigh the benefits of endpoints. A protocol specification needs to weigh the benefits of
skipping to change at page 30, line 39 skipping to change at page 30, line 28
field. Hiding headers can limit the ability to measure and field. Hiding headers can limit the ability to measure and
characterise traffic. characterise traffic.
Exposed transport headers are sometimes utilised as a part of the Exposed transport headers are sometimes utilised as a part of the
information to detect anomalies in network traffic. This can be used information to detect anomalies in network traffic. This can be used
as the first line of defence yo identify potential threats from DOS as the first line of defence yo identify potential threats from DOS
or malware and redirect suspect traffic to dedicated nodes or malware and redirect suspect traffic to dedicated nodes
responsible for DOS analysis, malware detection, or to perform packet responsible for DOS analysis, malware detection, or to perform packet
scrubbing "Scrubbing" (the normalization of packets so that there are scrubbing "Scrubbing" (the normalization of packets so that there are
no ambiguities in interpretation by the ultimate destination of the no ambiguities in interpretation by the ultimate destination of the
packet). These techniques are currently used by some operators to packet). These techniques are currently used by some operators to
also defend from distributed DOS attacks. also defend from distributed DOS attacks.
Exposed transport headers are sometimes also utilised as a part of Exposed transport headers are sometimes also utilised as a part of
the information used by the receiver of a transport protocol to the information used by the receiver of a transport protocol to
protect the transport layer from data injection by an attacker. In protect the transport layer from data injection by an attacker. In
evaluating this use of exposed header information, it is important to evaluating this use of exposed header information, it is important to
consider whether it introduces a significant DOS threat. For consider whether it introduces a significant DOS threat. For
example, an attacker could construct a DOS attack by sending packets example, an attacker could construct a DOS attack by sending packets
with a sequence number that falls within the currently accepted range with a sequence number that falls within the currently accepted range
of sequence numbers at the receiving endpoint, this would then of sequence numbers at the receiving endpoint, this would then
skipping to change at page 31, line 9 skipping to change at page 31, line 4
An attack can, for example, disrupt receiver processing, trigger loss An attack can, for example, disrupt receiver processing, trigger loss
and retransmission, or make a receiving endpoint perform unproductive and retransmission, or make a receiving endpoint perform unproductive
decryption of packets that cannot be successfully decrypted (forcing decryption of packets that cannot be successfully decrypted (forcing
a receiver to commit decryption resources, or to update and then a receiver to commit decryption resources, or to update and then
restore protocol state). restore protocol state).
One mitigation to off-path attack is to deny knowledge of what header One mitigation to off-path attack is to deny knowledge of what header
information is accepted by a receiver or obfusticate the accepted information is accepted by a receiver or obfusticate the accepted
header information, e.g., setting a non-predictable initial value for header information, e.g., setting a non-predictable initial value for
a sequence number during a protocol handshake, as in [RFC3550] and a sequence number during a protocol handshake, as in [RFC3550] and
[RFC6056], or a port value that can not be predicted (see section 5.1 [RFC6056], or a port value that can not be predicted (see section 5.1
of [RFC8085]). A receiver could also require additional information of [RFC8085]). A receiver could also require additional information
to be used as a part of check before accepting packets at the to be used as a part of check before accepting packets at the
transport layer (e.g., utilising a part of the sequence number space transport layer (e.g., utilising a part of the sequence number space
that is encrypted; or by verifying an encrypted token not visible to that is encrypted; or by verifying an encrypted token not visible to
an attacker). This would also mitigate on-path attacks. An an attacker). This would also mitigate on-path attacks. An
additional processing cost can be incurred when decryption needs to additional processing cost can be incurred when decryption needs to
be attempted before a receiver is able to discard injected packets. be attempted before a receiver is able to discard injected packets.
Open standards motivate a desire for this evaluation to include Open standards motivate a desire for this evaluation to include
independent observation and evaluation of performance data, which in independent observation and evaluation of performance data, which in
turn suggests control over where and when measurement samples are turn suggests control over where and when measurement samples are
collected. This requires consideration of the appropriate balance collected. This requires consideration of the appropriate balance
between encrypting all and no transport information. Open data, and between encrypting all and no transport information. Open data, and
accessibility to tools that can help understand trends in application accessibility to tools that can help understand trends in application
deployment, network traffic and usage patterns can all contribute to deployment, network traffic and usage patterns can all contribute to
understanding security challenges. understanding security challenges.
9. IANA Considerations 9. IANA Considerations
XX RFC ED - PLEASE REMOVE THIS SECTION XXX XX RFC ED - PLEASE REMOVE THIS SECTION XXX
This memo includes no request to IANA. This memo includes no request to IANA.
10. References 10. Acknowledgements
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997, <http://www.rfc-editor.org/info/
rfc2119>.
10.2. Informative References
[I-D.dolson-plus-middlebox-benefits]
Dolson, D., Snellman, J., Boucadair, M. and C. Jacquenet,
"Beneficial Functions of Middleboxes", Internet-Draft
draft-dolson-plus-middlebox-benefits-03, March 2017.
[I-D.ietf-aqm-codel] The authors would like to thank Mohamed Boucadair, Spencer Dawkins,
Nichols, K., Jacobson, V., McGregor, A. and J. Iyengar, Jana Iyengar, Mirja Kuehlewind, Kathleen Moriarty, Al Morton, Chris
"Controlled Delay Active Queue Management", Internet-Draft Seal, Joe Touch, Brian Trammell, and other members of the TSVWG for
draft-ietf-aqm-codel-10, October 2017. their comments and feedback.
[I-D.ietf-aqm-fq-codel] This work has received funding from the European Union's Horizon 2020
Hoeiland-Joergensen, T., McKenney, P., research and innovation programme under grant agreement No 688421.The
dave.taht@gmail.com, d., Gettys, J. and E. Dumazet, "The opinions expressed and arguments employed reflect only the authors'
FlowQueue-CoDel Packet Scheduler and Active Queue view. The European Commission is not responsible for any use that
Management Algorithm", Internet-Draft draft-ietf-aqm-fq- may be made of that information.
codel-06, March 2016.
[I-D.ietf-aqm-pie] This work has received funding from the UK Engineering and Physical
Pan, R., Natarajan, P., Baker, F. and G. White, "PIE: A Sciences Research Council under grant EP/R04144X/1.
Lightweight Control Scheme To Address the Bufferbloat
Problem", Internet-Draft draft-ietf-aqm-pie-10, September
2016.
[I-D.ietf-ippm-6man-pdm-option] 11. Informative References
Elkins, N., Hamilton, R. and m. mackermann@bcbsm.com,
"IPv6 Performance and Diagnostic Metrics (PDM) Destination
Option", Internet-Draft draft-ietf-ippm-6man-pdm-
option-13, June 2017.
[I-D.ietf-ippm-ioam-data] [I-D.ietf-ippm-ioam-data]
Brockners, F., Bhandari, S., Pignataro, C., Gredler, H., Brockners, F., Bhandari, S., Pignataro, C., Gredler, H.,
Leddy, J., Youell, S., Mizrahi, T., Mozes, D., Lapukhov, Leddy, J., Youell, S., Mizrahi, T., Mozes, D., Lapukhov,
P., Chang, R., daniel.bernier@bell.ca, d. and J. Lemon, P., Chang, R., daniel.bernier@bell.ca, d., and J. Lemon,
"Data Fields for In-situ OAM", Internet-Draft draft-ietf- "Data Fields for In-situ OAM", draft-ietf-ippm-ioam-
ippm-ioam-data-02, March 2018. data-03 (work in progress), June 2018.
[I-D.ietf-quic-transport] [I-D.ietf-quic-transport]
Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
and Secure Transport", Internet-Draft draft-ietf-quic- and Secure Transport", draft-ietf-quic-transport-14 (work
transport-03, May 2017. in progress), August 2018.
[I-D.ietf-taps-transport-security] [I-D.ietf-taps-transport-security]
Pauly, T., Perkins, C., Rose, K. and C. Wood, "A Survey of Pauly, T., Perkins, C., Rose, K., and C. Wood, "A Survey
Transport Security Protocols", Internet-Draft draft-ietf- of Transport Security Protocols", draft-ietf-taps-
taps-transport-security-01, May 2018. transport-security-02 (work in progress), June 2018.
[I-D.ietf-tcpinc-tcpcrypt] [I-D.ietf-tcpinc-tcpcrypt]
Bittau, A., Giffin, D., Handley, M., Mazieres, D., Slack, Bittau, A., Giffin, D., Handley, M., Mazieres, D., Slack,
Q. and E. Smith, "Cryptographic protection of TCP Streams Q., and E. Smith, "Cryptographic protection of TCP Streams
(tcpcrypt)", Internet-Draft draft-ietf-tcpinc-tcpcrypt-11, (tcpcrypt)", draft-ietf-tcpinc-tcpcrypt-12 (work in
November 2017. progress), June 2018.
[I-D.ietf-tsvwg-l4s-arch] [I-D.ietf-tsvwg-l4s-arch]
Briscoe, B., Schepper, K. and M. Bagnulo, "Low Latency, Briscoe, B., Schepper, K., and M. Bagnulo, "Low Latency,
Low Loss, Scalable Throughput (L4S) Internet Service: Low Loss, Scalable Throughput (L4S) Internet Service:
Architecture", Internet-Draft draft-ietf-tsvwg-l4s- Architecture", draft-ietf-tsvwg-l4s-arch-02 (work in
arch-01, October 2017. progress), March 2018.
[I-D.mm-wg-effect-encrypt]
Moriarty, K. and A. Morton, "Effects of Pervasive
Encryption on Operators", Internet-Draft draft-mm-wg-
effect-encrypt-24, March 2018.
[I-D.thomson-quic-grease] [I-D.thomson-quic-grease]
Thomson, M., "More Apparent Randomization for QUIC", Thomson, M., "More Apparent Randomization for QUIC",
Internet-Draft draft-thomson-quic-grease-00, December draft-thomson-quic-grease-00 (work in progress), December
2017. 2017.
[I-D.trammell-plus-abstract-mech] [I-D.trammell-plus-abstract-mech]
Trammell, B., "Abstract Mechanisms for a Cooperative Path Trammell, B., "Abstract Mechanisms for a Cooperative Path
Layer under Endpoint Control", Internet-Draft draft- Layer under Endpoint Control", draft-trammell-plus-
trammell-plus-abstract-mech-00, September 2016. abstract-mech-00 (work in progress), September 2016.
[I-D.trammell-plus-statefulness]
Kuehlewind, M., Trammell, B. and J. Hildebrand,
"Transport-Independent Path Layer State Management",
Internet-Draft draft-trammell-plus-statefulness-02,
December 2016.
[Latency] Briscoe, B., "Reducing Internet Latency: A Survey of [Latency] Briscoe, B., "Reducing Internet Latency: A Survey of
Techniques and Their Merits", November 2014. Techniques and Their Merits", November 2014.
[Measure] Fairhurst, G., Kuehlewind, M. and D. Lopez, "Measurement- [Measure] Fairhurst, G., Kuehlewind, M., and D. Lopez, "Measurement-
based Protocol Design", June 2017. based Protocol Design", June 2017.
[RFC1273] Schwartz, M.F., "Measurement Study of Changes in Service- [RFC1273] Schwartz, M., "Measurement Study of Changes in Service-
Level Reachability in the Global TCP/IP Internet: Goals, Level Reachability in the Global TCP/IP Internet: Goals,
Experimental Design, Implementation, and Policy Experimental Design, Implementation, and Policy
Considerations", RFC 1273, DOI 10.17487/RFC1273, November Considerations", RFC 1273, DOI 10.17487/RFC1273, November
1991, <https://www.rfc-editor.org/info/rfc1273>. 1991, <https://www.rfc-editor.org/info/rfc1273>.
[RFC2474] Nichols, K., Blake, S., Baker, F. and D. Black, [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS "Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI Field) in the IPv4 and IPv6 Headers", RFC 2474,
10.17487/RFC2474, December 1998, <http://www.rfc- DOI 10.17487/RFC2474, December 1998,
editor.org/info/rfc2474>. <https://www.rfc-editor.org/info/rfc2474>.
[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41, RFC [RFC2914] Floyd, S., "Congestion Control Principles", BCP 41,
2914, DOI 10.17487/RFC2914, September 2000, <https://www RFC 2914, DOI 10.17487/RFC2914, September 2000,
.rfc-editor.org/info/rfc2914>. <https://www.rfc-editor.org/info/rfc2914>.
[RFC3135] Border, J., Kojo, M., Griner, J., Montenegro, G. and Z. [RFC3135] Border, J., Kojo, M., Griner, J., Montenegro, G., and Z.
Shelby, "Performance Enhancing Proxies Intended to Shelby, "Performance Enhancing Proxies Intended to
Mitigate Link-Related Degradations", RFC 3135, DOI Mitigate Link-Related Degradations", RFC 3135,
10.17487/RFC3135, June 2001, <http://www.rfc-editor.org/ DOI 10.17487/RFC3135, June 2001,
info/rfc3135>. <https://www.rfc-editor.org/info/rfc3135>.
[RFC3168] Ramakrishnan, K., Floyd, S. and D. Black, "The Addition of [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
Explicit Congestion Notification (ECN) to IP", RFC 3168, of Explicit Congestion Notification (ECN) to IP",
DOI 10.17487/RFC3168, September 2001, <http://www.rfc- RFC 3168, DOI 10.17487/RFC3168, September 2001,
editor.org/info/rfc3168>. <https://www.rfc-editor.org/info/rfc3168>.
[RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and [RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and
Issues", RFC 3234, DOI 10.17487/RFC3234, February 2002, Issues", RFC 3234, DOI 10.17487/RFC3234, February 2002,
<http://www.rfc-editor.org/info/rfc3234>. <https://www.rfc-editor.org/info/rfc3234>.
[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation [RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
Metric for IP Performance Metrics (IPPM)", RFC 3393, DOI Metric for IP Performance Metrics (IPPM)", RFC 3393,
10.17487/RFC3393, November 2002, <https://www.rfc- DOI 10.17487/RFC3393, November 2002,
editor.org/info/rfc3393>. <https://www.rfc-editor.org/info/rfc3393>.
[RFC3449] Balakrishnan, H., Padmanabhan, V., Fairhurst, G. and M.
Sooriyabandara, "TCP Performance Implications of Network
Path Asymmetry", BCP 69, RFC 3449, DOI 10.17487/RFC3449,
December 2002, <http://www.rfc-editor.org/info/rfc3449>.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R. and V. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <http://www.rfc-editor.org/info/rfc3550>. July 2003, <https://www.rfc-editor.org/info/rfc3550>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302, DOI [RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
10.17487/RFC4302, December 2005, <http://www.rfc- DOI 10.17487/RFC4302, December 2005,
editor.org/info/rfc4302>. <https://www.rfc-editor.org/info/rfc4302>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
4303, DOI 10.17487/RFC4303, December 2005, <http://www RFC 4303, DOI 10.17487/RFC4303, December 2005,
.rfc-editor.org/info/rfc4303>. <https://www.rfc-editor.org/info/rfc4303>.
[RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C. and J. Rey, [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
"Extended RTP Profile for Real-time Transport Control "Extended RTP Profile for Real-time Transport Control
Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, DOI Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585,
10.17487/RFC4585, July 2006, <http://www.rfc-editor.org/ DOI 10.17487/RFC4585, July 2006,
info/rfc4585>. <https://www.rfc-editor.org/info/rfc4585>.
[RFC4737] Morton, A., Ciavattone, L., Ramachandran, G., Shalunov, S. [RFC4737] Morton, A., Ciavattone, L., Ramachandran, G., Shalunov,
and J. Perser, "Packet Reordering Metrics", RFC 4737, DOI S., and J. Perser, "Packet Reordering Metrics", RFC 4737,
10.17487/RFC4737, November 2006, <http://www.rfc- DOI 10.17487/RFC4737, November 2006,
editor.org/info/rfc4737>. <https://www.rfc-editor.org/info/rfc4737>.
[RFC5218] Thaler, D. and B. Aboba, "What Makes for a Successful [RFC5218] Thaler, D. and B. Aboba, "What Makes for a Successful
Protocol?", RFC 5218, DOI 10.17487/RFC5218, July 2008, Protocol?", RFC 5218, DOI 10.17487/RFC5218, July 2008,
<https://www.rfc-editor.org/info/rfc5218>. <https://www.rfc-editor.org/info/rfc5218>.
[RFC5236] Jayasumana, A., Piratla, N., Banka, T., Bare, A. and R. [RFC5236] Jayasumana, A., Piratla, N., Banka, T., Bare, A., and R.
Whitner, "Improved Packet Reordering Metrics", RFC 5236, Whitner, "Improved Packet Reordering Metrics", RFC 5236,
DOI 10.17487/RFC5236, June 2008, <http://www.rfc- DOI 10.17487/RFC5236, June 2008,
editor.org/info/rfc5236>. <https://www.rfc-editor.org/info/rfc5236>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/ (TLS) Protocol Version 1.2", RFC 5246,
RFC5246, August 2008, <http://www.rfc-editor.org/info/ DOI 10.17487/RFC5246, August 2008,
rfc5246>. <https://www.rfc-editor.org/info/rfc5246>.
[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation [RFC5481] Morton, A. and B. Claise, "Packet Delay Variation
Applicability Statement", RFC 5481, DOI 10.17487/RFC5481, Applicability Statement", RFC 5481, DOI 10.17487/RFC5481,
March 2009, <https://www.rfc-editor.org/info/rfc5481>. March 2009, <https://www.rfc-editor.org/info/rfc5481>.
[RFC5559] Eardley, P., Ed., "Pre-Congestion Notification (PCN) [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Architecture", RFC 5559, DOI 10.17487/RFC5559, June 2009,
<http://www.rfc-editor.org/info/rfc5559>.
[RFC5925] Touch, J., Mankin, A. and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925, Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <http://www.rfc-editor.org/info/rfc5925>. June 2010, <https://www.rfc-editor.org/info/rfc5925>.
[RFC6056] Larsen, M. and F. Gont, "Recommendations for Transport- [RFC6056] Larsen, M. and F. Gont, "Recommendations for Transport-
Protocol Port Randomization", BCP 156, RFC 6056, DOI Protocol Port Randomization", BCP 156, RFC 6056,
10.17487/RFC6056, January 2011, <https://www.rfc- DOI 10.17487/RFC6056, January 2011,
editor.org/info/rfc6056>. <https://www.rfc-editor.org/info/rfc6056>.
[RFC6269] Ford, M., Ed., Boucadair, M., Durand, A., Levis, P. and P. [RFC6269] Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and
Roberts, "Issues with IP Address Sharing", RFC 6269, DOI P. Roberts, "Issues with IP Address Sharing", RFC 6269,
10.17487/RFC6269, June 2011, <https://www.rfc-editor.org/ DOI 10.17487/RFC6269, June 2011,
info/rfc6269>. <https://www.rfc-editor.org/info/rfc6269>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <http://www.rfc-editor.org/info/rfc6347>. January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC6437] Amante, S., Carpenter, B., Jiang, S. and J. Rajahalme,
"IPv6 Flow Label Specification", RFC 6437, DOI 10.17487/
RFC6437, November 2011, <http://www.rfc-editor.org/info/
rfc6437>.
[RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P. [RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
and K. Carlberg, "Explicit Congestion Notification (ECN) "IPv6 Flow Label Specification", RFC 6437,
for RTP over UDP", RFC 6679, DOI 10.17487/RFC6679, August DOI 10.17487/RFC6437, November 2011,
2012, <http://www.rfc-editor.org/info/rfc6679>. <https://www.rfc-editor.org/info/rfc6437>.
[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an [RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
2014, <http://www.rfc-editor.org/info/rfc7258>. 2014, <https://www.rfc-editor.org/info/rfc7258>.
[RFC7525] Sheffer, Y., Holz, R. and P. Saint-Andre, "Recommendations [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
for Secure Use of Transport Layer Security (TLS) and "Recommendations for Secure Use of Transport Layer
Datagram Transport Layer Security (DTLS)", BCP 195, RFC Security (TLS) and Datagram Transport Layer Security
7525, DOI 10.17487/RFC7525, May 2015, <http://www.rfc- (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
editor.org/info/rfc7525>. 2015, <https://www.rfc-editor.org/info/rfc7525>.
[RFC7567] Baker, F.Ed., and G. Fairhurst, Ed., "IETF [RFC7567] Baker, F., Ed. and G. Fairhurst, Ed., "IETF
Recommendations Regarding Active Queue Management", BCP Recommendations Regarding Active Queue Management",
197, RFC 7567, DOI 10.17487/RFC7567, July 2015, <http:// BCP 197, RFC 7567, DOI 10.17487/RFC7567, July 2015,
www.rfc-editor.org/info/rfc7567>. <https://www.rfc-editor.org/info/rfc7567>.
[RFC7624] Barnes, R., Schneier, B., Jennings, C., Hardie, T., [RFC7624] Barnes, R., Schneier, B., Jennings, C., Hardie, T.,
Trammell, B., Huitema, C. and D. Borkmann, Trammell, B., Huitema, C., and D. Borkmann,
"Confidentiality in the Face of Pervasive Surveillance: A "Confidentiality in the Face of Pervasive Surveillance: A
Threat Model and Problem Statement", RFC 7624, DOI Threat Model and Problem Statement", RFC 7624,
10.17487/RFC7624, August 2015, <http://www.rfc-editor.org/ DOI 10.17487/RFC7624, August 2015,
info/rfc7624>. <https://www.rfc-editor.org/info/rfc7624>.
[RFC7872] Gont, F., Linkova, J., Chown, T. and W. Liu, "Observations [RFC7872] Gont, F., Linkova, J., Chown, T., and W. Liu,
on the Dropping of Packets with IPv6 Extension Headers in "Observations on the Dropping of Packets with IPv6
the Real World", RFC 7872, DOI 10.17487/RFC7872, June Extension Headers in the Real World", RFC 7872,
2016, <https://www.rfc-editor.org/info/rfc7872>. DOI 10.17487/RFC7872, June 2016,
<https://www.rfc-editor.org/info/rfc7872>.
[RFC7928] Kuhn, N., Ed., Natarajan, P., Ed., Khademi, N.Ed., and D. [RFC7928] Kuhn, N., Ed., Natarajan, P., Ed., Khademi, N., Ed., and
Ros, "Characterization Guidelines for Active Queue D. Ros, "Characterization Guidelines for Active Queue
Management (AQM)", RFC 7928, DOI 10.17487/RFC7928, July Management (AQM)", RFC 7928, DOI 10.17487/RFC7928, July
2016, <http://www.rfc-editor.org/info/rfc7928>. 2016, <https://www.rfc-editor.org/info/rfc7928>.
[RFC8084] Fairhurst, G., "Network Transport Circuit Breakers", BCP [RFC8033] Pan, R., Natarajan, P., Baker, F., and G. White,
208, RFC 8084, DOI 10.17487/RFC8084, March 2017, <http:// "Proportional Integral Controller Enhanced (PIE): A
www.rfc-editor.org/info/rfc8084>. Lightweight Control Scheme to Address the Bufferbloat
Problem", RFC 8033, DOI 10.17487/RFC8033, February 2017,
<https://www.rfc-editor.org/info/rfc8033>.
[RFC8085] Eggert, L., Fairhurst, G. and G. Shepherd, "UDP Usage [RFC8084] Fairhurst, G., "Network Transport Circuit Breakers",
BCP 208, RFC 8084, DOI 10.17487/RFC8084, March 2017,
<https://www.rfc-editor.org/info/rfc8084>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <http://www.rfc-editor.org/info/rfc8085>. March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[RFC8086] Yong, L., Ed., Crabbe, E., Xu, X. and T. Herbert, "GRE-in- [RFC8086] Yong, L., Ed., Crabbe, E., Xu, X., and T. Herbert, "GRE-
UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086, March in-UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086,
2017, <http://www.rfc-editor.org/info/rfc8086>. March 2017, <https://www.rfc-editor.org/info/rfc8086>.
[RFC8087] Fairhurst, G. and M. Welzl, "The Benefits of Using [RFC8087] Fairhurst, G. and M. Welzl, "The Benefits of Using
Explicit Congestion Notification (ECN)", RFC 8087, DOI Explicit Congestion Notification (ECN)", RFC 8087,
10.17487/RFC8087, March 2017, <http://www.rfc-editor.org/ DOI 10.17487/RFC8087, March 2017,
info/rfc8087>. <https://www.rfc-editor.org/info/rfc8087>.
[RFC8095] Fairhurst, G., Ed., Trammell, B.Ed., and M. Kuehlewind, [RFC8095] Fairhurst, G., Ed., Trammell, B., Ed., and M. Kuehlewind,
Ed., "Services Provided by IETF Transport Protocols and Ed., "Services Provided by IETF Transport Protocols and
Congestion Control Mechanisms", RFC 8095, DOI 10.17487/ Congestion Control Mechanisms", RFC 8095,
RFC8095, March 2017, <https://www.rfc-editor.org/info/ DOI 10.17487/RFC8095, March 2017,
rfc8095>. <https://www.rfc-editor.org/info/rfc8095>.
[RFC8257] Bensley, S., Thaler, D., Balasubramanian, P., Eggert, L. [RFC8250] Elkins, N., Hamilton, R., and M. Ackermann, "IPv6
Performance and Diagnostic Metrics (PDM) Destination
Option", RFC 8250, DOI 10.17487/RFC8250, September 2017,
<https://www.rfc-editor.org/info/rfc8250>.
[RFC8257] Bensley, S., Thaler, D., Balasubramanian, P., Eggert, L.,
and G. Judd, "Data Center TCP (DCTCP): TCP Congestion and G. Judd, "Data Center TCP (DCTCP): TCP Congestion
Control for Data Centers", RFC 8257, DOI 10.17487/RFC8257, Control for Data Centers", RFC 8257, DOI 10.17487/RFC8257,
October 2017, <https://www.rfc-editor.org/info/rfc8257>. October 2017, <https://www.rfc-editor.org/info/rfc8257>.
[Tor] The Tor Project, ., "https://www.torproject.org", June [RFC8289] Nichols, K., Jacobson, V., McGregor, A., Ed., and J.
2017. Iyengar, Ed., "Controlled Delay Active Queue Management",
RFC 8289, DOI 10.17487/RFC8289, January 2018,
<https://www.rfc-editor.org/info/rfc8289>.
[RFC8290] Hoeiland-Joergensen, T., McKenney, P., Taht, D., Gettys,
J., and E. Dumazet, "The Flow Queue CoDel Packet Scheduler
and Active Queue Management Algorithm", RFC 8290,
DOI 10.17487/RFC8290, January 2018,
<https://www.rfc-editor.org/info/rfc8290>.
[RFC8404] Moriarty, K., Ed. and A. Morton, Ed., "Effects of
Pervasive Encryption on Operators", RFC 8404,
DOI 10.17487/RFC8404, July 2018,
<https://www.rfc-editor.org/info/rfc8404>.
Appendix A. Revision information Appendix A. Revision information
-00 This is an individual draft for the IETF community. -00 This is an individual draft for the IETF community.
-01 This draft was a result of walking away from the text for a few -01 This draft was a result of walking away from the text for a few
days and then reorganising the content. days and then reorganising the content.
-02 This draft fixes textual errors. -02 This draft fixes textual errors.
skipping to change at page 37, line 29 skipping to change at page 37, line 33
-05 Corrections received and helpful inputs from Mohamed Boucadair. -05 Corrections received and helpful inputs from Mohamed Boucadair.
-06 Updated following comments from Stephen Farrell, and feedback via -06 Updated following comments from Stephen Farrell, and feedback via
email. Added a draft conclusion section to sketch some strawman email. Added a draft conclusion section to sketch some strawman
scenarios that could emerge. scenarios that could emerge.
-07 Updated following comments from Al Morton, Chris Seal, and other -07 Updated following comments from Al Morton, Chris Seal, and other
feedback via email. feedback via email.
-08 Updated to address comments sent to the TSVWG mailing list by -08 Updated to address comments sent to the TSVWG mailing list by
Kathleen Moriarty (on 08/05/2018 and 17/05/2018), Joe Touch on 11/05/ Kathleen Moriarty (on 08/05/2018 and 17/05/2018), Joe Touch on
2018, and Spencer Dawkins. 11/05/2018, and Spencer Dawkins.
-09 Updated security considerations. -09 Updated security considerations.
-10 Updated references, split the Introduction, and added a paragraph
giving some examples of why ossification has been an issue.
Authors' Addresses Authors' Addresses
Godred Fairhurst Godred Fairhurst
University of Aberdeen University of Aberdeen
Department of Engineering Department of Engineering
Fraser Noble Building Fraser Noble Building
Aberdeen, AB24 3UE Aberdeen AB24 3UE
Scotland Scotland
Email: gorry@erg.abdn.ac.uk EMail: gorry@erg.abdn.ac.uk
URI: http://www.erg.abdn.ac.uk/ URI: http://www.erg.abdn.ac.uk/
Colin Perkins Colin Perkins
University of Glasgow University of Glasgow
School of Computing Science School of Computing Science
Glasgow, G12 8QQ Glasgow G12 8QQ
Scotland Scotland
Email: csp@csperkins.org EMail: csp@csperkins.org
URI: https://csperkins.org// URI: https://csperkins.org//
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