draft-fairhurst-tsvwg-transport-encrypt-04.txt   draft-fairhurst-tsvwg-transport-encrypt-05.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.S. Perkins
Expires: March 29, 2018 University of Glasgow Expires: June 20, 2018 University of Glasgow
September 27, 2017 December 19, 2017
The Impact of Transport Header Encryption on Operation and Evolution of The Impact of Transport Header Encryption on Network Operation and
the Internet Evolution of the Internet
draft-fairhurst-tsvwg-transport-encrypt-04 draft-fairhurst-tsvwg-transport-encrypt-05
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 some in-network encryption at the transport layer. It identifies in-network uses of
uses of transport layer header information that can be used with a transport layer header information. It then reviews the implications
transport header integrity check. It reviews the implication of of developing encrypted end-to-end transport protocols on transport
developing encrypted end-to-end transport protocols and examines the protocol design and the implications on network operation. Since
implication of developing and deploying encrypted end-to-end transport measurement and analysis of the impact of network
transport protocols. Since transport measurement and analysis of the characteristics have been important to the design of current
impact of network characteristics have been important to the design transport protocols, it also considers some anticipated implications
of current transport protocols, it also considers some anticipated on transport and application evolution.
implications on transport and application evolution.
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Current uses of Transport Headers within the Network . . . 6 2. Current uses of Transport Headers within the Network . . . . . 7
1.1.1. Observing Transport Information in the Network . . . . 7 2.1. Observing Transport Information in the Network . . . . . . 7
1.1.1.1. Flow Identification . . . . . . . . . . . . . . . 7 2.1.1. Flow Identification . . . . . . . . . . . . . . . . . 7
1.1.1.2. Metrics derived from Transport Layer Headers . . . 7 2.1.2. Metrics derived from Transport Layer Headers . . . . . 8
1.1.1.3. Metrics derived from Network Layer Headers . . . . 10 2.1.3. Metrics derived from Network Layer Headers . . . . . . 11
1.1.2. Transport Measurement . . . . . . . . . . . . . . . . 12 2.2. Transport Measurement . . . . . . . . . . . . . . . . . . 12
1.1.2.1. Point of Measurement . . . . . . . . . . . . . . . 12 2.2.1. Point of Measurement . . . . . . . . . . . . . . . . . 13
1.1.2.2. Use by Operators to Plan and Provision Networks . 13 2.2.2. Use by Operators to Plan and Provision Networks . . . 14
1.1.2.3. Service Performance Measurement . . . . . . . . . 13 2.2.3. Service Performance Measurement . . . . . . . . . . . 14
1.1.2.4. Measuring Transport to Support Network Operations 13 2.2.4. Measuring Transport to Support Network Operations . . 14
1.1.3. Use for Network Diagnostics and Troubleshooting . . . 15 2.3. Use for Network Diagnostics and Troubleshooting . . . . . 15
1.1.4. Observing Headers to Implement Network Policy . . . . 15 2.4. Observing Headers to Implement Network Policy . . . . . . 16
2. Encryption and Authentication of Transport Headers . . . . . . 15 3. Encryption and Authentication of Transport Headers . . . . . . 16
2.1. Authenticating the Transport Protocol Header . . . . . . . 17 3.1. Authenticating the Transport Protocol Header . . . . . . . 18
2.2. Encrypting the Transport Payload . . . . . . . . . . . . . 17 3.2. Encrypting the Transport Payload . . . . . . . . . . . . . 18
2.3. Encrypting the Transport Header . . . . . . . . . . . . . 18 3.3. Encrypting the Transport Header . . . . . . . . . . . . . 18
2.4. Authenticating Transport Information and Selectively 3.4. Authenticating Transport Information and Selectively
Encrypting the Transport Header . . . . . . . . . . . . . 18 Encrypting the Transport Header . . . . . . . . . . . . . 19
2.5. Adding Transport Information to Network-Layer Protocol 3.5. Adding Transport Information to Network-Layer Protocol
Headers . . . . . . . . . . . . . . . . . . . . . . . . . 18 Headers . . . . . . . . . . . . . . . . . . . . . . . . . 19
3. Implications of Protecting the Transport Headers . . . . . . . 19 4. Implications of Protecting the Transport Headers . . . . . . . 20
3.1. Independent Measurement . . . . . . . . . . . . . . . . . 19 4.1. Independent Measurement . . . . . . . . . . . . . . . . . 20
3.2. Characterising "Unknown" Network Traffic . . . . . . . . . 20 4.2. Characterising "Unknown" Network Traffic . . . . . . . . . 21
3.3. Accountability and Internet Transport Protocols . . . . . 20 4.3. Accountability and Internet Transport Protocols . . . . . 21
3.4. Impact on Research, Development and Deployment . . . . . . 21 4.4. Impact on Research, Development and Deployment . . . . . . 22
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 22
5. Security Considerations . . . . . . . . . . . . . . . . . . . 22 6. Security Considerations . . . . . . . . . . . . . . . . . . . 23
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.1. Normative References . . . . . . . . . . . . . . . . . . . 22 8.1. Normative References . . . . . . . . . . . . . . . . . . . 23
7.2. Informative References . . . . . . . . . . . . . . . . . . 22 8.2. Informative References . . . . . . . . . . . . . . . . . . 23
Appendix A. Revision information . . . . . . . . . . . . . . . . . 26 Appendix A. Revision information . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 28
1. Introduction 1. Introduction
This document discusses the implications of end-to-end encryption This document discusses the implications of end-to-end encryption
applied at the transport layer, and examines the impact on transport applied at the transport layer, and examines the impact on transport
protocol design, usage, and network operations and management. It protocol design, transport usage, and network operations and
also considers anticipated implications on transport and application management. It also considers anticipated implications on transport
evolution. and application evolution.
The transport layer provides the first end-to-end interactions across The transport layer provides the first end-to-end interactions across
the Internet. Transport protocols layer directly over the network- the Internet. Transport protocols layer directly over the network-
layer service and are sent in the payload of network-layer packets. layer service and are sent in the payload of network-layer packets.
They support end-to-end communication between applications, supported They support end-to-end communication between applications, supported
by higher-layer protocols, running on the end systems (or transport by higher-layer protocols, running on the end systems (or transport
endpoint). This simple architectural view hides one of the core endpoints). This simple architectural view hides one of the core
functions of the transport, however - to discover and adapt to the functions of the transport, however - to discover and adapt to the
properties of the Internet path that is currently being used. The properties of the Internet path that is currently being used. The
design of Internet transport protocols is as much about trying to design of Internet transport protocols is as much about trying to
avoid the unwanted side effects of congestion on a flow and other avoid the unwanted side effects of congestion on a flow and other
capacity-sharing flows, avoiding congestion collapse, adapting to capacity-sharing flows, avoiding congestion collapse, adapting to
changes in the path characteristics, etc., as it is about end-to-end changes in the path characteristics, etc., as it is about end-to-end
feature negotiation, flow control and optimising for performance of a feature negotiation, flow control and optimising for performance of a
specific application. specific 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 select appropriate mechanisms, to ensure a safe, selection of appropriate mechanisms, to ensure a safe, reliable, and
reliable and robust Internet. In turn, the network operations robust Internet (e.g., [RFC1273]). In turn, the network operations
community relies on being able to understand the traffic passing over community relies on being able to understand the pattern and
the Internet, both in aggregate and at the flow level -- inspecting requirements of traffic passing over the Internet, both in aggregate
transport layer headers to help understand traffic dynamics. and at the flow level - inspecting transport layer headers to help
understand traffic dynamics.
There are many motivations for deploying encrypted transports, and There are many motivations for deploying encrypted transports, and
encryption of transport payloads. The increasing public concerns encryption of transport payloads. 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. At the same time, network operators and access protocols like QUIC. At the same time, network operators and access
providers, especially in mobile networks, have come to rely on the providers, especially in mobile networks, 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. enhance performance (e.g., [I-D.dolson-plus-middlebox-benefits]).
This document considers some implications of working with encrypted This document considers some implications of working with encrypted
transport protocols, and discusses trade-offs around authentication, transport protocols, and discusses trade-offs around authentication,
encryption of transport protocol headers. It describes some of the and encryption of transport protocol headers. It describes some of
architectural challenges and considerations in the way transport the architectural challenges and considerations in the way transport
protocols are designed when using encryption [Measure]. protocols are designed when using encryption [Measure].
Encryption of the transport layer brings some well-known privacy and Encryption of the transport layer brings some well-known privacy and
security benefits, but also introduces various costs that need to be security benefits, but also introduces various costs that need to be
considered. Specifically, it can impact the following activities considered. Specifically, it can impact the following activities
that rely on measurement and analysis of traffic flows: that rely on measurement and analysis of traffic flows:
o Network Operations and Research: Observable transport headers Network Operations and Research: Observable transport headers enable
enable 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. This data also can inform Internet engineering network operators.
research, and help the develop of new protocols and procedures.
Encryption of the entire transport protocol, including header
information, will restrict the availability of data, and might
lead to the development of alternative, and potentially more
intrusive, methods to acquire the needed data. Encrypting the
transport payload, but leaving some, or all, of the transport
headers unencrypted but authenticated can provide the majority of
the privacy and security benefits while allowing some measurement.
o Network Troubleshooting and diagnostics: Encrypting transport This data information can inform Internet engineering research,
header information eliminates the incentive for operators to and help the development of new protocols, methodologies, and
troubleshoot what they cannot interpret. A flow experiencing procedures. Encryption of the entire transport protocol,
packet loss looks like an unaffected flow when only observing including header information, will restrict the availability of
network layer headers (if transport sequence numbers and flow data, and might lead to the development of alternative, and
identifiers are obscured). This limits understanding of the impact potentially more intrusive, methods to acquire the needed data.
of packet loss on the flows that share a network segment.
Encrypted traffic therefore implies "don't touch", and a likely
trouble-shooting response will be "can't help, no trouble found".
The additional mechanisms that will need to be introduced to help
reconstruct transport-level metrics add complexity and operational
costs [I-D.mm-wg-effect-encrypt].
o Network Traffic Analysis: The use of encryption can make it harder Encrypting the transport payload, but leaving some, or all, of the
to determine which transport protocols and features are being used transport headers unencrypted, possibly with authentication, can
provide the majority of the privacy and security benefits while
allowing some measurement.
Protection from Denial of Service: Observable transport headers can
provide useful input to classification of traffic and detection of
anomalous events, such as distributed denial of service attacks.
To be effective, this protection needs to be able to uniquely
disambiguate unwanted traffic. An inability to separate this
traffic using packet header information is expected to lead to
less precise pattern matching techniques or resort to
indiscriminately (rate) limiting uncharacterised traffic.
Network Troubleshooting and Diagnostics: Encrypting transport header
information eliminates the incentive for operators to troubleshoot
what they cannot interpret. A flow experiencing packet loss looks
like an unaffected flow when only observing network layer headers
(if transport sequence numbers and flow identifiers are obscured).
This limits understanding of the impact of packet loss on the
flows that share a network segment. Encrypted traffic therefore
implies "don't touch", and a likely trouble-shooting response will
be "can't help, no trouble found". The additional mechanisms that
will need to be introduced to help reconstruct transport-level
metrics add complexity and operational costs [I-D.mm-wg-effect-
encrypt].
Network Traffic Analysis: The use of encryption can make it harder to
determine which transport protocols and features are being used
across a network segment. The trends in usage. This could impact across a network segment. The trends in usage. This could impact
the ability for an operator to anticipate the need for network the 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. While the impact engineering activities performed by operators. While the impact
may, in many cases, be small there are scenarios where operators may, in many cases, be small there are scenarios where operators
directly support particular services (e.g., in radio links, or to directly support particular services (e.g., in radio links, or to
troubleshoot issues realting to Quality of Service, QoS). The more troubleshoot issues relating to Quality of Service, QoS; the
complex the underlying infrastructure the more important this ability to perform fast re-routing of critical traffic, or support
to mitigate the characteristics of specific radio links). The
more complex the underlying infrastructure the more important this
impact. impact.
o Open and Verifiable Network Data: The use of transport header Open and Verifiable Network Data: The use of transport header
encryption reduces the range of actors that can capture useful encryption reduces the range of actors that can capture useful
measurement data. This is, of course, its goal. Doing so, measurement data. This is, of course, its goal. Doing so,
however, limits the information sources available to the Internet however, limits the information sources available to the Internet
community to understand the operation of transport protocols, so community to understand the operation of transport protocols, so
preventing access to the information necessary to inform design preventing access to the information necessary to inform design
decisions and standards for new protocols and related operational decisions and standards for new protocols and related operational
practices. There are dangers in a model where only endpoints practices.
(i.e., at user devices and within service platforms) can observe
performance, and this cannot be independently verified. To ensure There are dangers in a model where only endpoints (i.e., at user
the health of the standards and research communities, we need devices and within service platforms) can observe performance, and
independently captured data to develop on the behaviour of the this cannot be independently verified.
transports. Independently verifiable performance metrics might
also important in order to demonstrate regulatory compliance in To ensure the health of the standards and research communities, we
some jurisdictions. need independently captured data to develop new transport protocol
mechanisms based on the behaviour experienced in deployed
networks.
Independently verifiable performance metrics might also important
in order to demonstrate regulatory compliance in some
jurisdictions.
The last point leads us to consider the impact of encrypting all the The last point leads us to consider the impact of encrypting all the
transport headers the specification and development of protocols and transport headers the specification and development of protocols and
standards. It has potential impact on: standards. It has potential impact on:
o Understanding Feature Interactions: An appropriate vantage point, o Understanding Feature Interactions: An appropriate vantage point,
coupled with timing information about traffic flows, provides a coupled with timing information about traffic flows, provides a
valuable tool for benchmarking equipment and/or configurations, valuable tool for benchmarking equipment, functions, and/or
and to understand complex feature interactions. Transport header configurations, and to understand complex feature interactions.
encryption limits the ability to diagnose and explore interactions Transport header encryption limits the ability to diagnose and
between features at different protocol layers, a side-effect of explore interactions between features at different protocol
not allowing a choice of vantage point from which this information layers, a side-effect of not allowing a choice of vantage point
is observed. from which this information is observed.
o Supporting Common Specifications: The Transmission Control Protocl o Supporting Common Specifications: The Transmission Control
(TCP) is the predominant transport protocol. Its many variants Protocol (TCP) is the predominant transport protocol used over
have broadly consistent approaches to avoiding congestion Internet paths. Its many variants have broadly consistent
collapse, and to ensuring the stability of the network. Increased approaches to avoiding congestion collapse, and to ensuring the
use of transport layer encryption can overcome ossification, stability of the network. Increased use of transport layer
allowing deployment of new transports with different types of encryption can overcome ossification, allowing deployment of new
congestion control. This flexibility can be beneficial, but it transports with different types of congestion control. This
comes at the cost of fragmenting the ecosystem. There's little flexibility can be beneficial, but it comes at the cost of
doubt that developers will try to produce high quality transports fragmenting the ecosystem. There's little doubt that developers
for their target uses, but it is not clear there are sufficient will try to produce high quality transports for their target uses,
incentives to ensure good practice that benefits the wide but it is not clear there are sufficient incentives to ensure good
diversity of requirements for the Internet community as a whole. practice that benefits the wide diversity of requirements for the
Increased diversity, and the ability to innovate without public Internet community as a whole. Increased diversity, and the
scrutiny, risks point solutions that optimise for specific needs, ability to innovate without public scrutiny, risks point solutions
but accidentally disrupt operations of/in different parts of the that optimise for specific needs, but accidentally disrupt
network. The social compact that maintains the stability of the operations of/in different parts of the network. The social
network relies on accepting common specifications, and on the contract that maintains the stability of the network relies on
ability to verify that others also conform. accepting common specifications, and on the ability to verify that
others also conform.
o Operational practice: Published transport specifications allow o Operational practice: Published transport specifications allow
operators to check compliance. This can bring assurance to those operators to check compliance. This can bring assurance to those
operating networks, often avoiding the need to deploy complex operating networks, often avoiding the need to deploy complex
techniques that routinely monitor and manage TCP/IP traffic flows techniques that routinely monitor and manage TCP/IP traffic flows
(e.g. Avoiding the capital and operational costs of deploying (e.g. Avoiding the capital and operational costs of deploying
flow rate-limiting and network circuit-breaker methods). This flow rate-limiting and network circuit-breaker methods [RFC8084]).
should continue when encrypted transport headers are used, but This should continue when encrypted transport headers are used,
methods need to confirm that the traffic produced conforms to the but methods need to confirm that the traffic produced conforms to
expectations of the operator or developer. the expectations of the operator or developer.
o Restricting research and development: The use of encryption may o Restricting research and development: The use of encryption may
impede independent research into new mechanisms, measurement of impede independent research into new mechanisms, measurement of
behaviour, and development initiatives. Experience shows that behaviour, and development initiatives. Experience shows that
transport protocols are complicated to design and complex to transport protocols are complicated to design and complex to
deploy, and that individual mechanisms need to be evaluated while deploy, and that individual mechanisms need to be evaluated while
considering other mechanism, across a broad range of network considering other mechanisms, across a broad range of network
topologies and with attention to the impact on traffic sharing the topologies and with attention to the impact on traffic sharing the
capacity. Adopting pervasive encryption of transport information capacity. Adopting pervasive encryption of transport information
could eliminate the independent self-checks that have previously could eliminate the independent self-checks that have previously
been in place from research and academic contributors (e.g., the been in place from research and academic contributors (e.g., the
role of the IRTF ICCRG, and research publications in reviewing new role of the IRTF ICCRG, and research publications in reviewing new
transport mechanisms and assessing the impact of their transport mechanisms and assessing the impact of their
experimental deployment). experimental deployment).
Pervasive use of transport header encryption can impact the ways that Pervasive use of transport header encryption can impact the ways that
protocols are designed, standardised, deployed, and operated. The protocols are designed, standardised, deployed, and operated. The
choice of whether future transport protocols encrypt their protocol choice of whether future transport protocols encrypt their protocol
headers therefore needs to be taken based not solely on security and headers therefore needs to be taken based not solely on security and
privacy considerations, but also taking into account the impact on privacy considerations, but also taking into account the impact on
operations, standards, and research. A network that is secure but operations, standards, and research. A network that is secure but
unusable due to persistent congestion collapse is not an improvement, unusable due to persistent congestion collapse is not an improvement,
and while that would be an extreme outcome proposals that impose high and while that would be an extreme outcome proposals that impose high
costs for very limited benefits need to be considered carefully, to costs for very limited benefits need to be considered carefully, to
ensure the benefits outweigh the costs. ensure the benefits outweigh the costs.
1.1. Current uses of Transport Headers within the Network 2. Current uses of Transport Headers within the Network
The transport layer is the first end-to-end layer in the network Despite transport headers having end-to-end meaning, some of these
stack. Despite headers having end-to-end meaning, some transport transport headers have come to be used in various ways within the
headers have come to be used in various ways within the Internet. In Internet. In response to pervasive monitoring [RFC7624] revelations
response to pervasive monitoring [RFC7624] revelations and the IETF and the IETF consensus that "Pervasive Monitoring is an Attack"
consensus that "Pervasive Monitoring is an Attack" [RFC7258], efforts [RFC7258], efforts are underway to increase encryption of Internet
are underway to increase encryption of Internet traffic, which would traffic, which would prevent visibility of transport headers. This
prevent visibility of transport headers. This affects on how network affects on how network protocols are designed and used [I-D.mm-wg-
protocols are designed and used [I-D.mm-wg-effect-encrypt]. To effect-encrypt]. To understand these implications, it is first
understand these implications, it is first necessary to understand necessary to understand how transport layer headers are currently
how transport layer headers are currently observed and/or modified by observed and/or modified by middleboxes within the network.
middleboxes 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 methods at the transport transport header fields. Authentication methods at the transport
layer can be sued to detect any changes to an immutable header field layer can be used to detect any changes to an immutable header field
that were made by a network device along a path. The intentional that were made by a network device along a path. The intentional
modification of transport headers by middleboxes (such as Network modification of transport headers by middleboxes (such as Network
Address Translation with Protocol Translation, NAT-PT, or Firewalls) Address Translation, NAT, or Firewalls) is not considered. Common
is not considered. issues concerning IP address sharing are described in [RFC6269].
1.1.1. Observing Transport Information in the Network 2.1. Observing Transport Information in the Network
In-network observation of transport protocol headers requires In-network observation of transport protocol headers requires
knowledge of the format of the transport header: knowledge of the format of the transport header:
o Flows need to be identified at the level required for monitoring; o Flows need to be identified at the level required for monitoring;
o The protocol and version of the header need to be observable. As o The protocol and version of the header need to be observable. 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 Location and syntax of any transport headers to be observed. IETF o Location and syntax of any transport headers to be observed. IETF
transport protocols specify this information. transport protocols specify this information.
The following subsections describe various ways that observable The following subsections describe various ways that observable
transport information may be utilised. transport information may be utilised.
1.1.1.1. Flow Identification 2.1.1. Flow Identification
Transport protocol header information (with information in the
network header), can identify a flow and the connection state of the
flow, together with the protocol options being used. In some usages,
a low-numbered (well-known ) port number can identify a protocol
(although port information alone is not sufficient to guarantee
identification of a protocol). Transport protocols, such as TCP and
Stream Control Transport Protocol (SCTP) specify a standard base
header that includes sequence number information and other data, with
the possibility to negotiate additional headers at connection setup,
identified by an option number in the transport header. UDP-based
protocols can use, but sometimes do not use, well-known port numbers.
Some can instead be identified by signalling protocols or through the
use of magic numbers placed in the first byte(s) of the datagram
payload.
Transport protocol header information can identify a flow and the Flow identification is more complex and less easily achieved when
connection state of the flow, together with the protocol options multiplexing is used at or above the transport layer.
being used. In some usages, a low-numbered (well-known ) port can
identify a protocol (although port information alone is not
sufficient to guarantee identification of a protocol). Transport
protocols, such as TCP and Stream Control Transport Protocol (SCTP)
specify a standard base header that includes sequence number
information and other data, with the possibility to negotiate
additional headers at connection setup, identified by an option
number in the transport header. UDP-based protocols can use, but
sometimes do not use, well-known ports. Some can instead be
identified by signalling protocols or through the use of magic
numbers placed in the first byte(s) of the datagram payload.
1.1.1.2. Metrics derived from Transport Layer Headers 2.1.2. Metrics derived from Transport Layer Headers
Some actors have a need to characterise the performance of link/ Some actors have a need to characterise the performance of link/
network segments. Passive monitoring uses observed traffic to makes network segments. Passive monitoring uses observed traffic to makes
inferences from transport headers to derive these measurements. A inferences from transport headers to derive these measurements. A
variety of open source and commercial tools have been deployed that variety of open source and commercial tools have been deployed that
utilise this information. The following metrics can be derived from utilise this information. The following metrics can be derived from
transport header information: transport header information:
Traffic Rate and Volume: Header infromation may allow derivation of Traffic Rate and Volume: Header information may allow derivation of
volume measures per-application, to characterise the traffic that volume measures per-application, to characterise the traffic that
uses a network segment or the pattern of network usage. This may uses a network segment or the pattern of network usage. This may
be measured per endpoint or aggregate of endpoint (e.g., by an be measured per endpoint or for an aggregate of endpoints (e.g.,
operator to assess subscriber usage). It can also be used to by an operator to assess subscriber usage). It can also be used to
trigger measurement-based traffic shaping and to implement QoS trigger measurement-based traffic shaping and to implement QoS
support within the network and lower layers. Volume measures can support within the network and lower layers. Volume measures can
be valuable for capacity planning (providing detail of trends be valuable for capacity planning (providing detail of trends
rather than the volume per subscriber). rather than the volume per subscriber).
Loss Rate and Loss Pattern: Flow loss rate may be derived and is Loss Rate and Loss Pattern: Flow loss rate may be derived and is
often used as a metric for performance assessment and to often used as a metric for performance assessment and to
characterise transport behaviour. Understanding the root cause of characterise transport behaviour. Understanding the root cause of
loss can help an operator determine whether this requires loss can help an operator determine whether this requires
corrective action. corrective action. Network operators may also use the variation
in patterns of loss as a key performance metric, utilising this to
detect changes in the offered service.
There are various cause of loss, including: corruption on a link There are various cause of loss, including: corruption on a link
(e.g., interference on a radio link), buffer overflow (e.g., due (e.g., interference on a radio link), buffer overflow (e.g., due
to congestion), policing (traffic management), buffer management to congestion), policing (traffic management), buffer management
(e.g., Active Queue Management, AQM). Understanding flow loss (e.g., Active Queue Management, AQM), inadequate provision of
rate requires either maintaining per flow packet counters or by traffic preemption. Understanding flow loss rate requires either
observing sequence numbers in transport headers. Loss can be maintaining per flow packet counters or by observing sequence
monitored at the interface level by devices in the network. It is numbers in transport headers. Loss can be monitored at the
often important to understand the conditions under which packet interface level by devices in the network. It is often important
loss occurs. This usually requires relating loss to the traffic to understand the conditions under which packet loss occurs. This
flowing on the network segment at the time of loss. usually requires relating loss to the traffic flowing on the
network node/segment at the time of loss.
Observation of transport feedback information (observing loss Observation of transport feedback information (observing loss
reports, e.g., RTP Control Protocol (RTCP), TCP SACK) can increase reports, e.g., RTP Control Protocol (RTCP), TCP SACK) can increase
understanding of the impact of loss and help identify cases where understanding of the impact of loss and help identify cases where
loss may have been wrongly identified, or the transport did not loss may have been wrongly identified, or the transport did not
require the lost packet. It is sometimes more important to require the lost packet. It is sometimes more important to
understand the pattern of loss, than the loss rate - since losses understand the pattern of loss, than the loss rate - since losses
can often occur as bursts, rather than randomly-timed events. can often occur as bursts, rather than randomly-timed events.
Throughput and Goodput: The throughput observed by a flow can be Throughput and Goodput: The throughput observed by a flow can be
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determines the reaction time of the transport protocol itself, determines the reaction time of the transport protocol itself,
impacting flow setup, congestion control, loss recovery, and other impacting flow setup, congestion control, loss recovery, and other
transport mechanisms. The observed latency can have many transport mechanisms. The observed latency can have many
components [Latency]. Of these, unnecessary/unwanted queuing in components [Latency]. Of these, unnecessary/unwanted queuing in
network buffers has often been observed as a significant factor. network buffers has often been observed as a significant factor.
Once the cause of unwanted latency has been identified, this can Once the cause of unwanted latency has been identified, this can
often be eliminated, and determining latency metrics is a key often be eliminated, and determining latency metrics is a key
driver in the deployment of AQM [RFC7567], DiffServ [RFC2474], and driver in the deployment of AQM [RFC7567], DiffServ [RFC2474], and
Explicit Congestion Notification (ECN) [RFC3168] [RFC8087]. Explicit Congestion Notification (ECN) [RFC3168] [RFC8087].
To measure latency across a part of the 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 may be used to locate a source of latency, e.g., by observing This may be used to locate a source of latency, e.g., by observing
cases where the ratio of median to minimum RTT is large for a part cases where the ratio of median to minimum RTT is large for a part
of a path. of a path.
An example usage of this method could identify excessive buffers An example usage of this method could identify excessive buffers
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Jitter: Some network applications are sensitive to changes in packet Jitter: Some network applications are sensitive to changes in packet
timing. For such applications, it can be necessary to measure the timing. For such applications, it can be necessary to measure the
jitter observed along a portion of the path. The requirements to jitter observed along a portion of the path. The requirements to
measure jitter resemble those for the measurement of latency. measure jitter resemble those for the measurement of latency.
Flow Reordering: Significant flow reordering can impact time-critical Flow Reordering: Significant flow reordering can impact time-critical
applications and can be interpreted as loss by reliable 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). rules).
As in the drive to reduce network latency, there is a need for As in the drive to reduce network latency, there is a need for
operational tools to detect mis-ordered packet flows and quantify operational tools to detect mis-ordered packet flows and quantify
the degree or reordering. Techniques for measuring reordering the degree or reordering. Techniques for measuring reordering
typically observe packet sequence numbers. Metrics have been typically observe packet sequence numbers. Metrics have been
defined that evaluate whether a network has maintained packet defined that evaluate whether a network has maintained packet
order on a packet-by-packet basis [RFC4737] and [RFC5236]. order on a packet-by-packet basis [RFC4737] and [RFC5236].
There has 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 reduced the requirements for ordering. These have promise to to reduce the requirements for ordering. These have promise to
simplify network equipment design as well as the potential to simplify network equipment design as well as the potential to
improve robustness of the transport service. Measurements of improve robustness of the transport service. Measurements of
reordering can help understand the level of reordering within reordering can help understand the level of reordering within
deployed infrastructure, and inform decisions about how to deployed infrastructure, and inform decisions about how to
progress such mechanisms. progress such mechanisms.
Some protocols provide in-built monitoring and reporting functions. Some protocols provide in-built monitoring and reporting functions.
Transport fields in the RTP header [RFC3550] [RFC4585] can be Transport fields in the RTP header [RFC3550] [RFC4585] can be
observed to derive traffic volume measurements and provide observed to derive traffic volume measurements and provide
information on the progress and quality of a session using RTP. Key information on the progress and quality of a session using RTP. Key
performance indicators are retransmission rate, packet drop rate, performance indicators are retransmission rate, packet drop rate,
sector utilization level, a measure of reordering, peak rate, the CE- sector utilisation level, a measure of reordering, peak rate, the CE-
marking rate, etc. Metadata is often important to understand the marking rate, etc. 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.
When encryption conceals information in packet headers, measurements When encryption conceals information in packet headers, measurements
need to rely on pattern inferences and other heuristics grows, and need to rely on pattern inferences and other heuristics grows, and
accuracy suffers [I-D.mm-wg-effect-encrypt]. accuracy suffers [I-D.mm-wg-effect-encrypt].
1.1.1.3. Metrics derived from Network Layer Headers 2.1.3. 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 can be protocol header. These header fields are not encrypted and can be
used to make flow observations. used 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 expose
flow information in the IPv6 Flow Label field of the network-layer flow information in the IPv6 Flow Label field of the network-layer
header (e..g. [RFC8085]). This can be used to inform network- header (e.g., [RFC8085]). This can be used to inform network-layer
layer queuing, forwarding (e.g., for equal cost multi-path (ECMP) queuing, forwarding (e.g., for equal cost multi-path (ECMP)
routing, and Link Aggregation, LAG). This can provide useful routing, and Link Aggregation, LAG). This can provide useful
information to assign packets to flows in the data collected by information to assign packets to flows in the data collected by
measurement campaigns. Although important to characterising a measurement campaigns. Although important to characterising a
path, it does not directly provide any performance data. path, it does not directly provide any performance data.
Use Network-Layer Differentiated Services Code Point Point: Applicati Use Network-Layer Differentiated Services Code Point Point: Applicati
on can expose their delivery expectations to the network by ons can expose their delivery expectations to the network by
setting the Differentiated Services Code Point (DSCP) field of 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 any performance data. campaigns, but does not directly provide any 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
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ECN marks carried in the IP protocol header, it is much easier to ECN marks carried in the IP protocol header, it is much easier to
measure ECN than metering packet loss. However, interpreting the measure ECN than metering packet loss. However, interpreting the
marking behaviour (i.e., assessing congestion and diagnosing 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.,
Data Center TCP, DCTP [I-D.ietf-tcpm-dctcp], and Low Latency Low Data Center TCP, DCTP [RFC8257], and Low Latency Low Loss Scalable
Loss Scalable throughput, L4S, [I-D.ietf-tsvwg-l4s-arch]. throughput, L4S, [I-D.ietf-tsvwg-l4s-arch].
Use of ECN requires feedback a transport to feed back reception Use of ECN requires a transport to feed back reception information
information on the path towards the data sender. Exposure of this on the path towards the data sender. Exposure of this Transport
Transport ECN feedback provides an additional powerful tool to ECN feedback provides an additional powerful tool to understand
understand 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].
1.1.2. Transport Measurement 2.2. 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
VPNs and IPsec. When encryption conceals more layers in a packet, VPNs and IPsec. When encryption conceals more layers in a packet,
people seeking understanding of the network operation need to rely people seeking understanding of the network operation need to rely
more on pattern inferences and other heuristics. The accuracy of more on pattern inferences and other heuristics. The accuracy of
measurements therefore suffers, as does the ability to investigate measurements therefore suffers, as does the ability to investigate
and troubleshoot interactions between different anomalies. For and troubleshoot interactions between different anomalies. For
example, the traffic patterns between a web server and a browser are example, the traffic patterns between a web server and a browser are
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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.
1.1.2.1. Point of Measurement 2.2.1. 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 [I-D.ietf-aqm-fq-codel], combines sub
queues (statistically assigned per flow), management of the queue queues (statistically assigned per flow), management of the queue
length (CODEL), flow-scheduling, and a starvation prevention length (CODEL), flow-scheduling, and a starvation prevention
mechanism. Usually such algorithms are designed to be self-tuning, mechanism. Usually such algorithms are designed to be self-tuning,
but current methods typically employ heuristics that can result in but current methods typically employ heuristics that can result in
more loss under certain path conditions (e.g., large RTT, effects of more loss under certain path conditions (e.g., large RTT, effects of
multiple bottlenecks [RFC7567]). multiple bottlenecks [RFC7567]).
In-network measurements can distinguish between upstream and In-network measurements can distinguish between upstream and
downstream metrics with respect to the 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. configuration.
By correlating observations at multiple points along the path (e.g., By correlating observations at multiple points along the path (e.g.,
at the ingress and egress of a network segment), an observer can at the ingress and egress of a network segment), an observer can
determine the contribution of a portion of the path to an observed determine the contribution of a portion of the path to an observed
metric (to locate a source of delay, jitter, loss, reordering, metric (to locate a source of delay, jitter, loss, reordering,
congestion marking, etc.). congestion marking, etc.).
1.1.2.2. Use by Operators to Plan and Provision Networks 2.2.2. 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 traffic and patterns of usage as need to understand traffic trends and patterns of usage as inputs to
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 this to the in aggregate traffic can be observed and can be related this 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.
1.1.2.3. Service Performance Measurement 2.2.3. 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 available to used by various actors to help analyse the performance available to
users of a network segment, and inform operational practice. While users of a network segment, and inform operational practice. While
active measurements may be used in-network passive measurements can active measurements may be used in-network passive measurements can
have advantages in terms of eliminating unproductive traffic, have advantages in terms of eliminating unproductive traffic,
reducing the influence of test traffic on the overall traffic mix, reducing the influence of test traffic on the overall traffic mix,
and the ability to choose the point of measurement Section 1.1.2.1. and the ability to choose the point of measurement Section 2.2.1.
2.2.4. Measuring Transport to Support Network Operations
1.1.2.4. 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 key
transport function. Many network operators implicitly accept that transport function. Many network operators implicitly accept that
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struggle to easily duplicate [RFC8085]. 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
behaviour for TCP and SCTP. behaviour for TCP and SCTP.
However when anomolies are detected, tools can interpret the However when anomalies are detected, tools can interpret the
transport protocol header information to help understand the transport protocol header information to help understand the
impact of specific transport protocols (or protocol mechanisms) on impact of specific transport protocols (or protocol mechanisms) on
the other traffic that shares a network. An observation in the the other traffic that shares a network. An observation in the
network can gain understanding of the dynamics of a flow and its network can gain understanding of the dynamics of a flow and its
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 transport that has no inherent congestion control message-passing transport that has no inherent congestion control
mechanisms. Because congestion control is critical to the stable mechanisms. Because congestion control is critical to the stable
operation of the Internet, applications and other protocols that operation of the Internet, applications and other protocols that
choose to use UDP as an Internet transport are required to employ choose to use UDP as a transport are required to employ mechanisms
mechanisms to prevent congestion collapse, avoid unacceptable to prevent congestion collapse, avoid unacceptable contributions
contributions to jitter/latency, and to establish an acceptable to jitter/latency, and to establish an acceptable share of
share of capacity with concurrent traffic [RFC8085]. capacity with concurrent traffic [RFC8085].
A network operator needs tools to understand if UDP flows comply A network operator needs tools to understand if UDP flows comply
with congestion control expectations and therefore whether there with congestion control expectations and therefore whether there
is a need to deploy methods such as rate-limiters, transport 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 1.1.1.2. Section 2.1.2.
1.1.3. Use for Network Diagnostics and Troubleshooting 2.3. Use for Network Diagnostics and Troubleshooting
Transport header information is useful for a variety of operational Transport header information is useful for a variety of operational
tasks [I-D.mm-wg-effect-encrypt]: to diagnose network problems, tasks [I-D.mm-wg-effect-encrypt]: to diagnose network problems,
assess performance, capacity planning, management of denial of assess performance, capacity planning, management of denial of
service threats, and responding to user performance questions. These service threats, and responding to user performance questions. These
tasks seldom involve the need to determine the contents of the tasks seldom involve the need to determine the contents of the
transport payload, or other application details. transport payload, or other 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
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response to tracing issues, making appropriate Quality of Service, response to tracing issues, making appropriate Quality of Service,
QoS, decisions). For some this will be blessing, for others it may be QoS, decisions). For some this will be blessing, for others it may be
a curse. For example, operational performance data about encrypted a curse. For example, operational performance data about encrypted
flows needs to be determined by traffic pattern analysis, rather than flows needs to be determined by traffic pattern analysis, rather than
relying on traditional tools. This can impact the ability of the relying on traditional tools. This can impact the ability of the
operator to respond to faults, it could require reliance on endpoint operator to respond to faults, it could require reliance on endpoint
diagnostic tools or user involvement in diagnosing and diagnostic tools or user involvement in diagnosing and
troubleshooting unusual use cases or non-trivial problems. A key troubleshooting unusual use cases or non-trivial problems. A key
need here is that tools need to provide useful information during need here is that tools need to provide useful information during
network anomalies (e.g., significant reordering, high or intermittent network anomalies (e.g., significant reordering, high or intermittent
loss). Although many network operators utilise transport information loss). Although many network operators utilise transport information
as a part of their operational practice, the network will not break as a part of their operational practice, the network will not break
because transport headers are encrypted. because transport headers are encrypted.
1.1.4. Observing Headers to Implement Network Policy 2.4. 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 QoS management for resource-constrained networks and by firewalls for QoS management for resource-constrained networks and by firewalls
that use the information to implement access rules. Traffic that that use the information to implement access rules. Traffic that
cannot be classified, will typically receive a default treatment. cannot be classified, will typically receive a default treatment.
2. Encryption and Authentication of Transport Headers 3. 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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this, a method that authenticates transport headers may help improve this, a method that authenticates transport headers may help improve
the pace of transport development, by eliminating the need to always the pace of transport development, by eliminating the need to always
consider deployed middleboxes [I-D.trammell-plus-abstract-mech], or consider deployed middleboxes [I-D.trammell-plus-abstract-mech], or
potentially to only explicitly enable middlebox use for particular potentially to only explicitly enable middlebox use for particular
paths with particular middleboxes that are deliberately deployed to paths with particular middleboxes that are deliberately deployed to
realise a useful function for the network and/or users[RFC3135]. realise a useful function for the network and/or users[RFC3135].
Another motivation stems from increased concerns about privacy and Another motivation stems from increased concerns about privacy and
surveillance. Some Internet users have valued the ability to protect surveillance. Some Internet users have valued the ability to protect
identity, user location, and defend against traffic analysis, and identity, user location, and defend against traffic analysis, and
have used methods such as IPsec ESP and Tor [Tor]. Revelations about have used methods such as IPsec ESP. Revelations about the use of
the use of pervasive surveillance [RFC7624] have, to some extent, pervasive surveillance [RFC7624] have, to some extent, eroded trust
eroded trust in the service offered by network operators, and in the service offered by network operators, and following the
following the Snowden revelation in the USA in 2013 has led to an Snowden revelation in the USA in 2013 has led to an increased desire
increased desire for people to employ encryption to avoid unwanted for people to employ encryption to avoid unwanted "eavesdropping" on
"eavesdropping" on their communications. Whatever the reasons, there their communications. Whatever the reasons, there are now activities
are now activities in the IETF to design new protocols that may in the IETF to design new protocols that may include some form of
include some form of transport header encryption (e.g., QUIC [I-D transport header encryption (e.g., QUIC [I-D.ietf-quic-transport]).
.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 the IPv6 Flow decisions reflect the need of transport protocols, such the IPv6 Flow
Label [RFC6437], the Differentiated Services Code Point (DSCP) Label [RFC6437], the DSCP and ECN.
[RFC2474] and Explicit Congestion Notification (ECN) [RFC3168].
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
and users. and users.
o On the one hand, future Internet protocols that enable large-scale o On the one hand, future Internet protocols that enable large-scale
encryption assist in the restoration of the end-to-end nature of encryption assist in the restoration of the end-to-end nature of
the Internet by returning complex processing to the endpoints, the Internet by returning complex processing to the endpoints,
since middleboxes cannot modify what they cannot see. since middleboxes cannot modify what they cannot see.
skipping to change at page 17, line 18 skipping to change at page 18, line 16
understand the dynamics of protocols and traffic patterns. understand the dynamics of protocols and traffic patterns.
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. of evolution of the TCP/IP stack.
The next subsections briefly review some security design options for The next subsections briefly review some security design options for
transport protocols. transport protocols.
2.1. Authenticating the Transport Protocol Header 3.1. 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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including the IP pseudo header, TCP header, and TCP data. TCP-AO including the IP pseudo header, TCP header, and TCP data. TCP-AO
protects the transport layer, preventing attacks from disabling the protects the transport layer, preventing attacks from disabling the
TCP connection itself. TCP-AO may interact with middleboxes, TCP connection itself. TCP-AO may interact with middleboxes,
depending on their behaviour [RFC3234]. depending on their behaviour [RFC3234].
The IPsec Authentication Header (AH) [RFC4302] works at the network The IPsec Authentication Header (AH) [RFC4302] works at the network
layer and authenticates the IP payload. This therefore also layer and authenticates the IP payload. This therefore also
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.
2.2. Encrypting the Transport Payload 3.2. 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 2.1). check (Section 3.1).
Examples of encrypting the payload include Transport Layer Security Examples of encrypting the payload include Transport Layer Security
(TLS) over TCP [RFC5246] [RFC7525] or Datagram TLS (DTLS) over UDP (TLS) over TCP [RFC5246] [RFC7525] or Datagram TLS (DTLS) over UDP
[RFC6347] [RFC7525]. [RFC6347] [RFC7525].
2.3. Encrypting the Transport Header 3.3. 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 payload). This method does not expose any transport header and payload). This method does not expose any
transport information to devices in the network, which also prevents transport information to devices in the network, which also prevents
modification along the network path. modification along a network path.
The IPsec Encapsulating Security Payload (ESP) [RFC4303] is an The IPsec Encapsulating Security Payload (ESP) [RFC4303] is an
example of encryption at the network layer, it encrypts and example of encryption at the network layer, it encrypts and
authenticates all transport headers, preventing visibility of the authenticates all transport headers, preventing visibility of the
headers by in-network devices. Some Virtual Private Network (VPN) headers by in-network devices. Some Virtual Private Network (VPN)
methods also encrypt these headers. methods also encrypt these headers.
2.4. Authenticating Transport Information and Selectively Encrypting 3.4. 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.
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
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designer to decide which header fields to encrypt. On the one hand, designer to decide which header fields to encrypt. On the one hand,
security work typically employs a design technique that seeks to security work typically employs a design technique that seeks to
expose only what is needed. On the other hand, there may be expose only what is needed. On the other hand, there may be
performance and operational benefits in exposing selected information performance and operational benefits in exposing selected information
to network tools. to network tools.
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.
2.5. Adding Transport Information to Network-Layer Protocol Headers 3.5. Adding Transport Information to Network-Layer Protocol Headers
The transport information can be made visible in a network-layer The transport 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
to packets at the ingress to a maintenance domain (e.g., an Ethernet to packets at the ingress to a maintenance domain (e.g., an Ethernet
protocol header with timestamps and sequence number information using protocol header with timestamps and sequence number information using
a method such as 802.11ag) and removing the additional header at the a method such as 802.11ag or in-situ OAM [I-D.ietf-ippm-ioam-data])
egress of the maintenance domain. This approach enables some types and removing the additional header at the egress of the maintenance
of measurements, but does not cover the entire range of measurements domain. This approach enables some types of measurements, but does
described in this document. not cover the entire range of measurements described in this
document. In some cases, it can be difficult to position measurement
tools at the required segments/nodes and there can be challenges in
correlating the downsream/upstream information when in-band OAM data
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 [I-D.ietf-ippm-6man-
pdm-option]. This allows a sender to optionally include a pdm-option]. This allows a sender to optionally include a
destination option that caries header fields that can be used to destination option that caries header fields that can be used to
observe timestamps and packet sequence numbers. This information observe timestamps and packet sequence numbers. This information
could be authenticated by receiving transport endpoints when the could be authenticated by receiving transport endpoints when the
information is added at the sender and visible at the receiving information is added at the sender and visible at the receiving
endpoint, although methods to do this have not currently been endpoint, although methods to do this have not currently been
proposed. This method needs to be explicitly enabled at the sender. proposed. This method needs to be explicitly enabled at the sender.
A drawback of using extension headers is that IPv4 network options It can be undesirable to rely on methods requiring options or
are often not supported (or are carried on a slower processing path) extension headers. IPv4 network options are often not supported (or
and some IPv6 networks are also known to drop packets that set an are carried on a slower processing path) and some IPv6 networks are
IPv6 header extension. Another disadvantage is that protocols that also known to drop packets that set an IPv6 header extension (e.g.,
separately expose header information do not necessarily have an [RFC7872]). Another disadvantage is that protocols that separately
advantage to expose the information that is utilised by the protocol expose header information do not necessarily have an advantage to
itself, and could manipulate this header information to gain an expose the information that is utilised by the protocol itself, and
advantage from the network. could manipulate this header information to gain an advantage from
the network.
3. Implications of Protecting the Transport Headers 4. Implications of Protecting the Transport Headers
This section explores key implications of working with encrypted This section explores key implications of working with encrypted
transport protocols. transport protocols.
3.1. Independent Measurement 4.1. 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
could be possible for an applications to provide summary data on could be possible for an applications to provide summary data on
performance and usage of the network. This data could be made performance and usage of the network. This data could be made
available to other actors. However, this data needs to contain available to other actors. However, this data needs to contain
sufficient detail to understand (and possibly reconstruct the network sufficient detail to understand (and possibly reconstruct the network
traffic pattern for further testing) and to be correlated with the traffic pattern for further testing) and to be correlated with the
configuration of the network paths being measured. Sharing configuration of the network paths being measured. Sharing
information between actors needs also to consider the privacy of the information between actors needs also to consider the privacy of the
skipping to change at page 20, line 28 skipping to change at page 21, line 24
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.
3.2. Characterising "Unknown" Network Traffic 4.2. 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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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.
3.3. Accountability and Internet Transport Protocols 4.3. Accountability and Internet Transport Protocols
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, and where needed to flows from acquiring excessive network capacity, and where needed to
deploy appropriate tools Section 1.1.2.4. Obfuscating or hiding this deploy appropriate tools Section 2.2.4. Obfuscating or hiding this
information using encryption is expected to lead operators and information using encryption is expected to lead operators and
maintainers of middleboxes (firewalls, etc.) to seek other methods to maintainers of middleboxes (firewalls, etc.) to seek other methods to
classify and mechanisms to condition network traffic. A lack of data classify and mechanisms to condition network traffic.
seems likely to reduce the level of precision with which these
mechanisms are applied, and this needs to be considered when
evaluating the impact of designs for transport encryption.
3.4. Impact on Research, Development and Deployment A lack of data seems likely to reduce the level of precision with
which these mechanisms are applied, and this needs to be considered
when evaluating the impact of designs for transport encryption. This
could lead to increased use of rate limiting, circuit breaker
techniques [RFC8084], or even blocking of uncharacterised traffic.
This would hinder deployment of new mechanisms and/or protocols.
4.4. Impact on Research, Development and Deployment
Measurement data is increasingly being used to inform design Measurement data is increasingly being used to inform design
decisions in networking research, during development of new 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.
skipping to change at page 21, line 41 skipping to change at page 22, line 38
therefore typically evolve as a protocol matures, or in response to therefore typically evolve as a protocol matures, or in response to
changes in network conditions, changes in network traffic or changes changes in network conditions, changes in network traffic or changes
to application usage. to application usage.
The growth and diversity of applications and protocols using the The growth and diversity of applications and protocols using the
Internet continues to expand - and there has been recent interest in Internet continues to expand - and there has been recent interest in
a wide range of new transport methods, e.g., Larger Initial Window, a wide range of new transport methods, e.g., Larger Initial Window,
Proportional Rate Reduction (PRR), congestion control methods based Proportional Rate Reduction (PRR), congestion control methods based
on measuring bottleneck bandwidth and round-trip propagation time, on measuring bottleneck bandwidth and round-trip propagation time,
the introduction of AQM techniques and new forms of ECN response the introduction of AQM techniques and new forms of ECN response
(e.g., Data Centre TCP, DCTP [I-D.ietf-tcpm-dctcp], and methods (e.g., DCTP, and methods proposed for L4S). For each new method it is
proposed for Low Latency Low Loss Scalable throughput, L4S). For desirable to build a body of data reflecting its behaviour under a
each new method it is desirable to build a body of data reflecting wide range of deployment scenarios, traffic load, and interactions
its behaviour under a wide range of deployment scenarios, traffic with other deployed/candidate methods.
load, and interactions with other 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.
4. Acknowledgements 5. Acknowledgements
The author would like to thank all who have talked to him face-to- The author would like to thank all who have talked to him face-to-
face or via email. ... face or via email. ...
This work has received funding from the European Union's Horizon 2020 This work has received funding from the European Union's Horizon 2020
research and innovation programme under grant agreement No 688421.The research and innovation programme under grant agreement No 688421.The
opinions expressed and arguments employed reflect only the authors' opinions expressed and arguments employed reflect only the authors'
view. The European Commission is not responsible for any use that view. The European Commission is not responsible for any use that
may be made of that information. may be made of that information.
5. Security Considerations 6. Security Considerations
This document is about design and deployment considerations for This document is about design and deployment considerations for
transport protocols. Authentication, confidentiality protection, and transport protocols. Authentication, confidentiality protection, and
integrity protection are identified as Transport Features by integrity protection are identified as Transport Features by
RFC8095". As currently deployed in the Internet, these features are RFC8095". As currently deployed in the Internet, these features are
generally provided by a protocol or layer on top of the transport generally provided by a protocol or layer on top of the transport
protocol; no current full-featured standards-track transport protocol protocol; no current full-featured standards-track transport protocol
provides these features on its own. Therefore, these features are provides these features on its own. Therefore, these features are
not considered in this document, with the exception of native not considered in this document, with the exception of native
authentication capabilities of TCP and SCTP for which the security authentication capabilities of TCP and SCTP for which the security
skipping to change at page 22, line 34 skipping to change at page 23, line 34
Open data, and accessibility to tools that can help understand trends Open data, and accessibility to tools that can help understand trends
in application deployment, network traffic and usage patterns can all in application deployment, network traffic and usage patterns can all
contribute to understanding security challenges. Standard protocols contribute to understanding security challenges. Standard protocols
and understanding of the interactions between mechanisms and traffic and understanding of the interactions between mechanisms and traffic
patterns can also provide valuable insight into appropriate security patterns can also provide valuable insight into appropriate security
design. Like congestion control mechanisms, security mechanisms are design. Like congestion control mechanisms, security mechanisms are
difficult to design and implement correctly. It is hence recommended difficult to design and implement correctly. It is hence recommended
that applications employ well-known standard security mechanisms such that applications employ well-known standard security mechanisms such
as DTLS, TLS or IPsec, rather than inventing their own. as DTLS, TLS or IPsec, rather than inventing their own.
6. IANA Considerations 7. 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.
7. References 8. References
7.1. Normative References 8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997, <http://www.rfc-editor.org/info/ RFC2119, March 1997, <http://www.rfc-editor.org/info/
rfc2119>. rfc2119>.
7.2. Informative References 8.2. Informative References
[I-D.dolson-plus-middlebox-benefits] [I-D.dolson-plus-middlebox-benefits]
Dolson, D., Snellman, J., Boucadair, M. and C. Jacquenet, Dolson, D., Snellman, J., Boucadair, M. and C. Jacquenet,
"Beneficial Functions of Middleboxes", Internet-Draft "Beneficial Functions of Middleboxes", Internet-Draft
draft-dolson-plus-middlebox-benefits-03, March 2017. draft-dolson-plus-middlebox-benefits-03, March 2017.
[I-D.ietf-aqm-codel] [I-D.ietf-aqm-codel]
Nichols, K., Jacobson, V., McGregor, A. and J. Jana, Nichols, K., Jacobson, V., McGregor, A. and J. Jana,
"Controlled Delay Active Queue Management", Internet-Draft "Controlled Delay Active Queue Management", Internet-Draft
draft-ietf-aqm-codel-00, October 2014. draft-ietf-aqm-codel-00, October 2014.
skipping to change at page 23, line 25 skipping to change at page 24, line 25
Lightweight Control Scheme To Address the Bufferbloat Lightweight Control Scheme To Address the Bufferbloat
Problem", Internet-Draft draft-ietf-aqm-pie-00, October Problem", Internet-Draft draft-ietf-aqm-pie-00, October
2014. 2014.
[I-D.ietf-ippm-6man-pdm-option] [I-D.ietf-ippm-6man-pdm-option]
Elkins, N., Hamilton, R. and m. mackermann@bcbsm.com, Elkins, N., Hamilton, R. and m. mackermann@bcbsm.com,
"IPv6 Performance and Diagnostic Metrics (PDM) Destination "IPv6 Performance and Diagnostic Metrics (PDM) Destination
Option", Internet-Draft draft-ietf-ippm-6man-pdm- Option", Internet-Draft draft-ietf-ippm-6man-pdm-
option-10, May 2017. option-10, May 2017.
[I-D.ietf-ippm-ioam-data]
Brockners, F., Bhandari, S., Pignataro, C., Gredler, H.,
Leddy, J., Youell, S., Mizrahi, T., Mozes, D., Lapukhov,
P., Chang, R. and d. daniel.bernier@bell.ca, "Data Fields
for In-situ OAM", Internet-Draft draft-ietf-ippm-ioam-
data-01, October 2017.
[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", Internet-Draft draft-ietf-quic-
transport-03, May 2017. transport-03, May 2017.
[I-D.ietf-tcpm-accurate-ecn] [I-D.ietf-tcpm-accurate-ecn]
Briscoe, B., Kuehlewind, M. and R. Scheffenegger, "More Briscoe, B., Kuehlewind, M. and R. Scheffenegger, "More
Accurate ECN Feedback in TCP", Internet-Draft draft-ietf- Accurate ECN Feedback in TCP", Internet-Draft draft-ietf-
tcpm-accurate-ecn-00, December 2015. tcpm-accurate-ecn-00, December 2015.
[I-D.ietf-tcpm-dctcp]
Bensley, S., Thaler, D., Balasubramanian, P., Eggert, L.
and G. Judd, "Datacenter TCP (DCTCP): TCP Congestion
Control for Datacenters", Internet-Draft draft-ietf-tcpm-
dctcp-06, May 2017.
[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", Internet-Draft draft-ietf-tsvwg-l4s-
arch-00, May 2017. arch-00, May 2017.
[I-D.mm-wg-effect-encrypt] [I-D.mm-wg-effect-encrypt]
Moriarty, K. and A. Morton, "Effect of Pervasive Moriarty, K. and A. Morton, "Effect of Pervasive
Encryption on Operators", Internet-Draft draft-mm-wg- Encryption on Operators", Internet-Draft draft-mm-wg-
effect-encrypt-11, April 2017. effect-encrypt-11, April 2017.
skipping to change at page 24, line 15 skipping to change at page 25, line 17
"Transport-Independent Path Layer State Management", "Transport-Independent Path Layer State Management",
Internet-Draft draft-trammell-plus-statefulness-02, Internet-Draft draft-trammell-plus-statefulness-02,
December 2016. 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-
Level Reachability in the Global TCP/IP Internet: Goals,
Experimental Design, Implementation, and Policy
Considerations", RFC 1273, DOI 10.17487/RFC1273, November
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, DOI
10.17487/RFC2474, December 1998, <http://www.rfc- 10.17487/RFC2474, December 1998, <http://www.rfc-
editor.org/info/rfc2474>. editor.org/info/rfc2474>.
[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, DOI
10.17487/RFC3135, June 2001, <http://www.rfc-editor.org/ 10.17487/RFC3135, June 2001, <http://www.rfc-editor.org/
skipping to change at page 25, line 42 skipping to change at page 26, line 52
rfc5246>. rfc5246>.
[RFC5559] Eardley, P., Ed., "Pre-Congestion Notification (PCN) [RFC5559] Eardley, P., Ed., "Pre-Congestion Notification (PCN)
Architecture", RFC 5559, DOI 10.17487/RFC5559, June 2009, Architecture", RFC 5559, DOI 10.17487/RFC5559, June 2009,
<http://www.rfc-editor.org/info/rfc5559>. <http://www.rfc-editor.org/info/rfc5559>.
[RFC5925] Touch, J., Mankin, A. and R. Bonica, "The TCP [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, <http://www.rfc-editor.org/info/rfc5925>.
[RFC6269] Ford, M., Ed., Boucadair, M., Durand, A., Levis, P. and P.
Roberts, "Issues with IP Address Sharing", RFC 6269, DOI
10.17487/RFC6269, June 2011, <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, <http://www.rfc-editor.org/info/rfc6347>.
[RFC6437] Amante, S., Carpenter, B., Jiang, S. and J. Rajahalme, [RFC6437] Amante, S., Carpenter, B., Jiang, S. and J. Rajahalme,
"IPv6 Flow Label Specification", RFC 6437, DOI 10.17487/ "IPv6 Flow Label Specification", RFC 6437, DOI 10.17487/
RFC6437, November 2011, <http://www.rfc-editor.org/info/ RFC6437, November 2011, <http://www.rfc-editor.org/info/
rfc6437>. rfc6437>.
[RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P. [RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.
skipping to change at page 26, line 32 skipping to change at page 27, line 46
"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, DOI
10.17487/RFC7624, August 2015, <http://www.rfc-editor.org/ 10.17487/RFC7624, August 2015, <http://www.rfc-editor.org/
info/rfc7624>. info/rfc7624>.
[RFC7713] Mathis, M. and B. Briscoe, "Congestion Exposure (ConEx) [RFC7713] Mathis, M. and B. Briscoe, "Congestion Exposure (ConEx)
Concepts, Abstract Mechanism, and Requirements", RFC 7713, Concepts, Abstract Mechanism, and Requirements", RFC 7713,
DOI 10.17487/RFC7713, December 2015, <http://www.rfc- DOI 10.17487/RFC7713, December 2015, <http://www.rfc-
editor.org/info/rfc7713>. editor.org/info/rfc7713>.
[RFC7872] Gont, F., Linkova, J., Chown, T. and W. Liu, "Observations
on the Dropping of Packets with IPv6 Extension Headers in
the Real World", RFC 7872, 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 D.
Ros, "Characterization Guidelines for Active Queue 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, <http://www.rfc-editor.org/info/rfc7928>.
[RFC8084] Fairhurst, G., "Network Transport Circuit Breakers", BCP [RFC8084] Fairhurst, G., "Network Transport Circuit Breakers", BCP
208, RFC 8084, DOI 10.17487/RFC8084, March 2017, <http:// 208, RFC 8084, DOI 10.17487/RFC8084, March 2017, <http://
www.rfc-editor.org/info/rfc8084>. www.rfc-editor.org/info/rfc8084>.
[RFC8085] Eggert, L., Fairhurst, G. and G. Shepherd, "UDP Usage [RFC8085] Eggert, L., Fairhurst, G. and G. Shepherd, "UDP Usage
skipping to change at page 26, line 54 skipping to change at page 28, line 22
[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-in-
UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086, March UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086, March
2017, <http://www.rfc-editor.org/info/rfc8086>. 2017, <http://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, DOI
10.17487/RFC8087, March 2017, <http://www.rfc-editor.org/ 10.17487/RFC8087, March 2017, <http://www.rfc-editor.org/
info/rfc8087>. info/rfc8087>.
[RFC8257] Bensley, S., Thaler, D., Balasubramanian, P., Eggert, L.
and G. Judd, "Data Center TCP (DCTCP): TCP Congestion
Control for Data Centers", RFC 8257, DOI 10.17487/RFC8257,
October 2017, <https://www.rfc-editor.org/info/rfc8257>.
[Tor] The Tor Project, ., "https://www.torproject.org", June [Tor] The Tor Project, ., "https://www.torproject.org", June
2017. 2017.
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.
-03 This draft follows feedback from people reading this draft. -03 This draft follows feedback from people reading this draft.
-04 This adds an additional contributore and includes significant -04 This adds an additional contributor and includes significant
reworking to ready this for review by the wider IETF community Colin reworking to ready this for review by the wider IETF community Colin
Perkins joined the author list. Perkins joined the author list.
Comments from the community are welcome on the text and Comments from the community are welcome on the text and
recommendations. recommendations.
Authors' Addresses -05 Corrections received and helpful inputs from Mohamed Boucadair.
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/
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