draft-fairhurst-tsvwg-transport-encrypt-05.txt   draft-fairhurst-tsvwg-transport-encrypt-06.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: June 20, 2018 University of Glasgow Expires: August 11, 2018 University of Glasgow
December 19, 2017 February 9, 2018
The Impact of Transport Header Encryption on Network Operation and The Impact of Transport Header Confidentiality on Network Operation and
Evolution of the Internet Evolution of the Internet
draft-fairhurst-tsvwg-transport-encrypt-05 draft-fairhurst-tsvwg-transport-encrypt-06
Abstract Abstract
This document describes implications of applying end-to-end This document describes implications of applying end-to-end
encryption at the transport layer. It identifies in-network uses of encryption at the transport layer. It identifies in-network uses of
transport layer header information. It then reviews the implications transport layer header information. It then reviews the implications
of developing encrypted end-to-end transport protocols on transport of developing end-to-end transport protocols that use encryption to
protocol design and the implications on network operation. Since provide confidentiality of the transport protocol header and expected
transport measurement and analysis of the impact of network implications of transport protocol design and network operation.
Since transport measurement and analysis of the impact of network
characteristics have been important to the design of current characteristics have been important to the design of current
transport protocols, it also considers some anticipated implications transport protocols, it also considers the impact on transport and
on transport and application evolution. application evolution.
Status of this Memo Status of this Memo
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provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on June 20, 2018. This Internet-Draft will expire on August 11, 2018.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Current uses of Transport Headers within the Network . . . . . 7 2. Current uses of Transport Headers within the Network . . . . . 8
2.1. Observing Transport Information in the Network . . . . . . 7 2.1. Observing Transport Information in the Network . . . . . . 8
2.1.1. Flow Identification . . . . . . . . . . . . . . . . . 7 2.1.1. Flow Identification . . . . . . . . . . . . . . . . . 9
2.1.2. Metrics derived from Transport Layer Headers . . . . . 8 2.1.2. Metrics derived from Transport Layer Headers . . . . . 9
2.1.3. Metrics derived from Network Layer Headers . . . . . . 11 2.1.3. Metrics derived from Network Layer Headers . . . . . . 12
2.2. Transport Measurement . . . . . . . . . . . . . . . . . . 12 2.2. Transport Measurement . . . . . . . . . . . . . . . . . . 14
2.2.1. Point of Measurement . . . . . . . . . . . . . . . . . 13 2.2.1. Point of Measurement . . . . . . . . . . . . . . . . . 14
2.2.2. Use by Operators to Plan and Provision Networks . . . 14 2.2.2. Use by Operators to Plan and Provision Networks . . . 15
2.2.3. Service Performance Measurement . . . . . . . . . . . 14 2.2.3. Service Performance Measurement . . . . . . . . . . . 15
2.2.4. Measuring Transport to Support Network Operations . . 14 2.2.4. Measuring Transport to Support Network Operations . . 16
2.3. Use for Network Diagnostics and Troubleshooting . . . . . 15 2.3. Use for Network Diagnostics and Troubleshooting . . . . . 17
2.4. Observing Headers to Implement Network Policy . . . . . . 16 2.3.1. Examples of measurements . . . . . . . . . . . . . . . 17
3. Encryption and Authentication of Transport Headers . . . . . . 16 2.4. Observing Headers to Implement Network Policy . . . . . . 18
3.1. Authenticating the Transport Protocol Header . . . . . . . 18 3. Encryption and Authentication of Transport Headers . . . . . . 18
3.2. Encrypting the Transport Payload . . . . . . . . . . . . . 18 3.1. Authenticating the Transport Protocol Header . . . . . . . 20
3.3. Encrypting the Transport Header . . . . . . . . . . . . . 18 3.2. Encrypting the Transport Payload . . . . . . . . . . . . . 20
3.3. Encrypting the Transport Header . . . . . . . . . . . . . 20
3.4. Authenticating Transport Information and Selectively 3.4. Authenticating Transport Information and Selectively
Encrypting the Transport Header . . . . . . . . . . . . . 19 Encrypting the Transport Header . . . . . . . . . . . . . 21
3.5. Adding Transport Information to Network-Layer Protocol 3.5. Optional Encryption of Header Information . . . . . . . . 21
Headers . . . . . . . . . . . . . . . . . . . . . . . . . 19 4. Addition of Transport Information to Network-Layer Protocol
4. Implications of Protecting the Transport Headers . . . . . . . 20 Headers . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.1. Independent Measurement . . . . . . . . . . . . . . . . . 20 5. Implications of Protecting the Transport Headers . . . . . . . 22
4.2. Characterising "Unknown" Network Traffic . . . . . . . . . 21 5.1. Independent Measurement . . . . . . . . . . . . . . . . . 22
4.3. Accountability and Internet Transport Protocols . . . . . 21 5.2. Characterising "Unknown" Network Traffic . . . . . . . . . 23
4.4. Impact on Research, Development and Deployment . . . . . . 22 5.3. Accountability and Internet Transport Protocols . . . . . 23
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 22 5.4. Impact on Research, Development and Deployment . . . . . . 24
6. Security Considerations . . . . . . . . . . . . . . . . . . . 23 6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 25
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23 8. Security Considerations . . . . . . . . . . . . . . . . . . . 27
8.1. Normative References . . . . . . . . . . . . . . . . . . . 23 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
8.2. Informative References . . . . . . . . . . . . . . . . . . 23 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Appendix A. Revision information . . . . . . . . . . . . . . . . . 28 10.1. Normative References . . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 28 10.2. Informative References . . . . . . . . . . . . . . . . . 28
Appendix A. Revision information . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
1. Introduction 1. Introduction
This document describes implications of applying end-to-end
This document discusses the implications of end-to-end encryption encryption at the transport layer. It reviews the implications of
applied at the transport layer, and examines the impact on transport developing end-to-end transport protocols that use encryption to
protocol design, transport usage, and network operations and provide confidentiality of the transport protocol header and expected
management. It also considers anticipated implications on transport implications of transport protocol design and network operation. It
and application evolution. also considers anticipated implications on transport 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
endpoints). 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
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To achieve stable Internet operations the IETF transport community To achieve stable Internet operations the IETF transport community
has to date relied heavily on measurement and insights of the network has to date relied heavily on measurement and insights of the network
operations community to understand the trade-offs, and to inform operations community to understand the trade-offs, and to inform
selection of appropriate mechanisms, to ensure a safe, reliable, and selection of appropriate mechanisms, to ensure a safe, reliable, and
robust Internet (e.g., [RFC1273]). In turn, the network operations robust Internet (e.g., [RFC1273]). In turn, the network operations
community relies on being able to understand the pattern and community relies on being able to understand the pattern and
requirements of traffic passing over the Internet, both in aggregate requirements of traffic passing over the Internet, both in aggregate
and at the flow level - inspecting transport layer headers to help and at the flow level - inspecting transport layer headers to help
understand traffic dynamics. understand traffic dynamics.
There are many motivations for deploying encrypted transports, and There are many motivations for deploying encrypted transports (i.e.,
encryption of transport payloads. The increasing public concerns transport protocols that use encryption to provide confidentiality of
about the interference with Internet traffic have led to a rapidly some or all of the transport-layer header information), and
expanding deployment of encryption to protect end-user privacy, in encryption of transport payloads (i.e. Confidentiality of the
protocols like QUIC. At the same time, network operators and access payload data). The increasing public concerns about the interference
providers, especially in mobile networks, have come to rely on the with Internet traffic have led to a rapidly expanding deployment of
in-network measurement of transport properties and the functionality encryption to protect end-user privacy, in protocols like QUIC, but
provided by middleboxes to both support network operations and also expected to forma a basis of future protocol designs.
enhance performance (e.g., [I-D.dolson-plus-middlebox-benefits]).
This document considers some implications of working with encrypted Introducing cryptographic integrity checks to header fields can also
transport protocols, and discusses trade-offs around authentication, prevent undetected manipulation of the field by network devices.
and encryption of transport protocol headers. It describes some of However, it does not prevent inspection of the information by device
the architectural challenges and considerations in the way transport on path, and it is possible that such devices could develop
protocols are designed when using encryption [Measure]. mechanisms that rely on the presence of such a field, or a known
value in the field. This leads to ossification of the header: An
endpoint could be required to supply the header to receive the
network service that it desires. In some cases, this could be benign
to the protocol (e.g., recognising the start of a connection), but in
other cases, any change to the protocol use of a specific header can
have undesirable implications (e.g., a mechanism implemented in a
network device, such as a firewall, that requires a header field to
have only a specific known set of values could prevent the device
from forwarding packets using a different version of a protocol that
introduces a new feature that changes the value present in this
field). A protocol that intentionally varies the format and value of
header fields (sometimes known as Greasing) has been suggested as a
way to help avoid such ossification of the transport protocol.
Encryption of the transport layer brings some well-known privacy and Implementations of network devices are encouraged to avoid side-
security benefits, but also introduces various costs that need to be effects when protocols are updated. In particular, it is important
considered. Specifically, it can impact the following activities that protocols either do not expose information where the usage may
that rely on measurement and analysis of traffic flows: change in future protocols, or that methods that utilise the
information are robust to potential changes as protocols evolve over
time.
At the same time, some network operators and access providers, have
come to rely on the in-network measurement of transport properties
and the functionality provided by middleboxes to both support network
operations and enhance performance (e.g., [I-D.dolson-plus-middlebox-
benefits]).
A protocol design can use header encryption to provide
confidentiality of some or all of the protocol header information.
This prevents an on-path device from knowledge of the header field.
It therefore prevents mechanisms being built that directly rely on
the information or seeks to imply semantics of an exposed header
field. Protocol designers have often ignored these implications and
this document suggests that exposure of information should be
carefully considered when specifying new protocols.
Using encryption to provide confidentiality of the transport layer
brings some well-known privacy and security benefits. While a
protocol design that encrypts (hides) all the transport information
can help reduce ossification of the transport layer, it could result
in ossification of the network service. There can be advantages in
providing a level of ossification of the header in terms of providing
a set of specified header fields that are observable from in-network
devices.
There can also be implications when working with encrypted transport
protocols that hide transport header information from the network.
This present architectural challenges and considerations in the way
transport protocols are designed, and ability to characterise and
compare different transport solutions [Measure]. This results in
trade-offs around authentication, and confidentiality of transport
protocol headers and the potential support for other uses of this
header information. For example, it can impact the following
activities that rely on measurement and analysis of traffic flows:
Network Operations and Research: Observable transport headers enable Network Operations and Research: Observable transport headers enable
both operators and the research community to measure and analyse both operators and the research community to measure and analyse
protocol performance, network anomalies, and failure pathologies. protocol performance, network anomalies, and failure pathologies.
This information can help inform capacity planning, and assist in This information can help inform capacity planning, and assist in
determining the need for equipment and/or configuration changes by determining the need for equipment and/or configuration changes by
network operators. network operators.
This data information can inform Internet engineering research, This data information can inform Internet engineering research,
and help the development of new protocols, methodologies, and and help the development of new protocols, methodologies, and
procedures. Encryption of the entire transport protocol, procedures. Hiding the entire transport protocol, including
including header information, will restrict the availability of header information, will restrict the availability of data, and
data, and might lead to the development of alternative, and might lead to the development of alternative, and potentially more
potentially more intrusive, methods to acquire the needed data. intrusive, methods to acquire the needed data.
Encrypting the transport payload, but leaving some, or all, of the Providing confidentiality of the transport payload, but leaving
transport headers unencrypted, possibly with authentication, can some, or all, of the transport headers unencrypted, possibly with
provide the majority of the privacy and security benefits while authentication, can provide the majority of the privacy and
allowing some measurement. security benefits while allowing some measurement.
Protection from Denial of Service: Observable transport headers can Protection from Denial of Service: Observable transport headers can
provide useful input to classification of traffic and detection of provide useful input to classification of traffic and detection of
anomalous events, such as distributed denial of service attacks. anomalous events, such as distributed denial of service attacks.
To be effective, this protection needs to be able to uniquely To be effective, this protection needs to be able to uniquely
disambiguate unwanted traffic. An inability to separate this disambiguate unwanted traffic. An inability to separate this
traffic using packet header information is expected to lead to traffic using packet header information is expected to lead to
less precise pattern matching techniques or resort to less precise pattern matching techniques or resort to
indiscriminately (rate) limiting uncharacterised traffic. indiscriminately (rate) limiting uncharacterised traffic.
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like an unaffected flow when only observing network layer headers like an unaffected flow when only observing network layer headers
(if transport sequence numbers and flow identifiers are obscured). (if transport sequence numbers and flow identifiers are obscured).
This limits understanding of the impact of packet loss on the This limits understanding of the impact of packet loss on the
flows that share a network segment. Encrypted traffic therefore flows that share a network segment. Encrypted traffic therefore
implies "don't touch", and a likely trouble-shooting response will implies "don't touch", and a likely trouble-shooting response will
be "can't help, no trouble found". The additional mechanisms that be "can't help, no trouble found". The additional mechanisms that
will need to be introduced to help reconstruct transport-level will need to be introduced to help reconstruct transport-level
metrics add complexity and operational costs [I-D.mm-wg-effect- metrics add complexity and operational costs [I-D.mm-wg-effect-
encrypt]. encrypt].
Network Traffic Analysis: The use of encryption can make it harder to Network Traffic Analysis: Hiding transport protocol header
determine which transport protocols and features are being used information can make it harder to determine which transport
across a network segment. The trends in usage. This could impact protocols and features are being used across a network segment.
the ability for an operator to anticipate the need for network The trends in usage. This could impact the ability for an
upgrades and roll-out. It can also impact the on-going traffic operator to anticipate the need for network upgrades and roll-out.
engineering activities performed by operators. While the impact It can also impact the on-going traffic engineering activities
may, in many cases, be small there are scenarios where operators performed by operators. While the impact may, in many cases, be
directly support particular services (e.g., in radio links, or to small there are scenarios where operators directly support
troubleshoot issues relating to Quality of Service, QoS; the particular services (e.g., in radio links, or to troubleshoot
ability to perform fast re-routing of critical traffic, or support issues relating to Quality of Service, QoS; the ability to perform
to mitigate the characteristics of specific radio links). The fast re-routing of critical traffic, or support to mitigate the
more complex the underlying infrastructure the more important this characteristics of specific radio links). The more complex the
impact. underlying infrastructure the more important this impact.
Open and Verifiable Network Data: The use of transport header Open and Verifiable Network Data: The Hiding transport protocol
encryption reduces the range of actors that can capture useful header information can reduces the range of actors that can
measurement data. This is, of course, its goal. Doing so, capture useful measurement data. This is, of course, its goal.
however, limits the information sources available to the Internet Doing so, however, limits the information sources available to the
community to understand the operation of transport protocols, so Internet community to understand the operation of transport
preventing access to the information necessary to inform design protocols, so preventing access to the information necessary to
decisions and standards for new protocols and related operational inform design decisions and standards for new protocols and
practices. related operational practices.
There are dangers in a model where only endpoints (i.e., at user There are dangers in a model where only endpoints (i.e., at user
devices and within service platforms) can observe performance, and devices and within service platforms) can observe performance, and
this cannot be independently verified. this cannot be independently verified.
To ensure the health of the standards and research communities, we To ensure the health of the standards and research communities, we
need independently captured data to develop new transport protocol need independently captured data to develop new transport protocol
mechanisms based on the behaviour experienced in deployed mechanisms based on the behaviour experienced in deployed
networks. networks.
Independently verifiable performance metrics might also important Independently verifiable performance metrics might also important
in order to demonstrate regulatory compliance in some in order to demonstrate regulatory compliance in some
jurisdictions. jurisdictions.
The last point leads us to consider the impact of encrypting all the The last point leads us to consider the impact of hiding transport
transport headers the specification and development of protocols and headers in the specification and development of protocols and
standards. It has potential impact on: standards. This 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, functions, and/or valuable tool for benchmarking equipment, functions, and/or
configurations, and to understand complex feature interactions. configurations, and to understand complex feature interactions.
Transport header encryption limits the ability to diagnose and An inability to observe transport protocol information can limit
explore interactions between features at different protocol the ability to diagnose and explore interactions between features
layers, a side-effect of not allowing a choice of vantage point at different protocol layers, a side-effect of not allowing a
from which this information is observed. choice of vantage point from which this information is observed.
o Supporting Common Specifications: The Transmission Control o Supporting Common Specifications: The Transmission Control
Protocol (TCP) is the predominant transport protocol used over Protocol (TCP) is the predominant transport protocol used over
Internet paths. Its many variants have broadly consistent Internet paths. Its many variants have broadly consistent
approaches to avoiding congestion collapse, and to ensuring the approaches to avoiding congestion collapse, and to ensuring the
stability of the network. Increased use of transport layer stability of the network. Increased use of transport layer
encryption can overcome ossification, allowing deployment of new encryption can overcome ossification, allowing deployment of new
transports with different types of congestion control. This transports and different types of congestion control. This
flexibility can be beneficial, but it comes at the cost of flexibility can be beneficial, but it can come at the cost of
fragmenting the ecosystem. There's little doubt that developers fragmenting the ecosystem. There is little doubt that developers
will try to produce high quality transports for their target uses, will try to produce high quality transports for their target uses,
but it is not clear there are sufficient incentives to ensure good but it is not clear there are sufficient incentives to ensure good
practice that benefits the wide diversity of requirements for the practice that benefits the wide diversity of requirements for the
Internet community as a whole. Increased diversity, and the Internet community as a whole. Increased diversity, and the
ability to innovate without public scrutiny, risks point solutions ability to innovate without public scrutiny, risks point solutions
that optimise for specific needs, but accidentally disrupt that optimise for specific needs, but accidentally disrupt
operations of/in different parts of the network. The social operations of/in different parts of the network. The social
contract that maintains the stability of the network relies on contract that maintains the stability of the network relies on
accepting common specifications, and on the ability to verify that accepting common specifications, and on the ability to verify that
others also conform. 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 [RFC8084]). flow rate-limiting and network circuit-breaker methods [RFC8084]).
This should continue when encrypted transport headers are used, When it is not possible to observe transport header information,
but methods need to confirm that the traffic produced conforms to methods are still needed to confirm that the traffic produced
the expectations of the operator or developer. conforms to the expectations of the operator or developer.
o Restricting research and development: The use of encryption may o Restricting research and development: Hiding transport information
impede independent research into new mechanisms, measurement of can impede independent research into new mechanisms, measurement
behaviour, and development initiatives. Experience shows that of 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 mechanisms, 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. Hiding transport header information (e.g., by pervasive
could eliminate the independent self-checks that have previously encryption of transport information) could eliminate the
been in place from research and academic contributors (e.g., the independent self-checks that have previously been in place from
role of the IRTF ICCRG, and research publications in reviewing new research and academic contributors (e.g., the role of the IRTF
transport mechanisms and assessing the impact of their ICCRG, and research publications in reviewing new transport
experimental deployment). mechanisms and assessing the impact of their experimental
deployment).
Pervasive use of transport header encryption can impact the ways that In summary, a lack of visibility of transport header information can
protocols are designed, standardised, deployed, and operated. The impact the ways that protocols are designed, standardised, deployed,
choice of whether future transport protocols encrypt their protocol and operated. The choice of whether future transport protocols
headers therefore needs to be taken based not solely on security and encrypt their protocol headers therefore needs to be taken based not
privacy considerations, but also taking into account the impact on solely on security and privacy considerations, but also taking into
operations, standards, and research. A network that is secure but account the impact on operations, standards, and research. A network
unusable due to persistent congestion collapse is not an improvement, that is secure but unusable due to persistent congestion collapse is
and while that would be an extreme outcome proposals that impose high not an improvement, and while that would be an extreme outcome
costs for very limited benefits need to be considered carefully, to proposals that impose high costs for very limited benefits need to be
ensure the benefits outweigh the costs. considered carefully, to ensure the benefits outweigh the costs.
2. Current uses of Transport Headers within the Network 2. Current uses of Transport Headers within the Network
Despite transport headers having end-to-end meaning, some of these Despite transport headers having end-to-end meaning, some of these
transport headers have come to be used in various ways within the transport headers have come to be used in various ways within the
Internet. In response to pervasive monitoring [RFC7624] revelations Internet. In response to pervasive monitoring [RFC7624] revelations
and the IETF consensus that "Pervasive Monitoring is an Attack" and the IETF consensus that "Pervasive Monitoring is an Attack"
[RFC7258], efforts are underway to increase encryption of Internet [RFC7258], efforts are underway to increase encryption of Internet
traffic, which would prevent visibility of transport headers. This traffic,. Applying confidentiality to transport header fields would
affects on how network protocols are designed and used [I-D.mm-wg- affect how network protocols are designed and used [I-D.mm-wg-effect-
effect-encrypt]. To understand these implications, it is first encrypt]. To understand these implications, it is first necessary to
necessary to understand how transport layer headers are currently understand how transport layer headers are currently observed and/or
observed and/or modified by middleboxes within the network. modified by 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 used 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, NAT, or Firewalls) is not considered. Common Address Translation, NAT, or Firewalls) is not considered. Common
issues concerning IP address sharing are described in [RFC6269]. issues concerning IP address sharing are described in [RFC6269].
2.1. Observing Transport Information in the Network 2.1. Observing Transport Information in the Network
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2.1.2. 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 information may allow derivation of Traffic Rate and Volume: Header information e.g., (sequence number,
volume measures per-application, to characterise the traffic that length) may allow derivation of volume measures per-application,
uses a network segment or the pattern of network usage. This may to characterise the traffic that uses a network segment or the
be measured per endpoint or for an aggregate of endpoints (e.g., pattern of network usage. This may be measured per endpoint or
by an operator to assess subscriber usage). It can also be used to for an aggregate of endpoints (e.g., by an operator to assess
trigger measurement-based traffic shaping and to implement QoS subscriber usage). It can also be used to trigger measurement-
support within the network and lower layers. Volume measures can based traffic shaping and to implement QoS support within the
be valuable for capacity planning (providing detail of trends network and lower layers. Volume measures can be valuable for
rather than the volume per subscriber). capacity planning (providing detail of trends 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 (e.g., from
often used as a metric for performance assessment and to sequence number) and is often used as a metric for performance
characterise transport behaviour. Understanding the root cause of assessment and to characterise transport behaviour. Understanding
loss can help an operator determine whether this requires the root cause of loss can help an operator determine whether this
corrective action. Network operators may also use the variation requires corrective action. Network operators may also use the
in patterns of loss as a key performance metric, utilising this to variation in patterns of loss as a key performance metric,
detect changes in the offered service. 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), inadequate provision of (e.g., Active Queue Management, AQM), inadequate provision of
traffic preemption. Understanding flow loss rate requires either traffic preemption. Understanding flow loss rate requires either
maintaining per flow packet counters or by observing sequence maintaining per flow packet counters or by observing sequence
numbers in transport headers. Loss can be monitored at the numbers in transport headers. Loss can be monitored at the
interface level by devices in the network. It is often important interface level by devices in the network. It is often important
to understand the conditions under which packet loss occurs. This to understand the conditions under which packet loss occurs. This
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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). Since this impacts transport performance, network tools
are needed to detect and measure unwanted/excessive reordering.
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 have been initiatives in the IETF transport area to reduce There have been initiatives in the IETF transport area to reduce
the impact of reordering within a transport flow, possibly leading the impact of reordering within a transport flow, possibly leading
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performance indicators are retransmission rate, packet drop rate, performance indicators are retransmission rate, packet drop rate,
sector utilisation 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 information in transport headers is concealed, measurements need
need to rely on pattern inferences and other heuristics grows, and 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].
2.1.3. 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
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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 a measurement point. These are downstream metrics with respect to a measurement point. These are
particularly useful for locating the source of problems or to assess particularly useful for locating the source of problems or to assess
the performance of a network segment or a particular device the performance of a network segment or a particular device
configuration. configuration.
By correlating observations at multiple points along the path (e.g., By correlating observations of headers at multiple points along the
at the ingress and egress of a network segment), an observer can path (e.g., at the ingress and egress of a network segment), an
determine the contribution of a portion of the path to an observed observer can determine the contribution of a portion of the path to
metric (to locate a source of delay, jitter, loss, reordering, an observed metric (to locate a source of delay, jitter, loss,
congestion marking, etc.). reordering, congestion marking, etc.).
2.2.2. 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 and patterns of usage as inputs to need to understand traffic trends and patterns of usage as inputs to
decisions about planning products and provisioning for new decisions about planning products and provisioning for new
deployments. This measurement information can also be correlated deployments. This measurement information can also be correlated
with billing information when this is also collected by an operator. with billing information when this is also collected by an operator.
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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.
2.2.3. 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 offered to the
users of a network segment, and inform operational practice. While users of a network segment, and inform operational practice.
active measurements may be used in-network passive measurements can
have advantages in terms of eliminating unproductive traffic, While active measurements may be used in-network passive measurements
can 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 2.2.1. and the ability to choose the point of measurement Section 2.2.1.
However, passive measurements may rely on observing transport
headers.
2.2.4. Measuring Transport to Support Network Operations 2.2.4. 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].
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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.
2.3.1. Examples of measurements
Future versions of this document may provide more about existing
tooling at Network Operations Centres that rely upon observing
transport layer header information.
Debugging and diagnosing the root causes of faults concern particular
users traffic is an activity that may depend on connection
information from the protocol - In some case, this may involve active
injection of test traffic to complete a measurement. Most operators
do not have access to user equipment. There may also be costs
associated with running such tests (e.g., the implications of
bandwidth tests in a mobile network are obvious). Some active
measurements (e.g., response under load or particular workloads) may
perturb other traffic, and could require dedicated access to the
network segment. An alternative approach is to use in-network
techniques that observe transport packet headers in operational
networks to make the measurements.
in other cases, measurement involves dissecting traffic flows. The
observed transport layer information can help identify whether the
link/network tuning is effective and alert to potential problems that
can be hard to derive from link or device measurements alone. The
design trade-offs for radio networks are often very different to
those of wired networks. A radio-based network (e.g., cellular
mobile, enterprise WiFi, satellite access/back-haul, point-to-point
radio) has the complexity of a subsystem that performs radio resource
management - with direct impact on the available capacity, and
potentially loss/reordering of packets. The impact of the pattern of
loss and congestion, differs for different traffic types, correlation
with propagation and interference can all have significant impact on
the cost and performance of a provided service. The need for this
type of information is expected to increase as operators bring
together heterogeneous types of network equipment and seek to deploy
opportunistic methods to access radio spectrum.
XXX Note: The authors are looking for contributions that say more
about the things people are currently doing with exposed transport
fields and what problems they are trying to solve, or how they use
the information they derive. How problematic is new tools to follow-
up. Examples could include: Health monitoring; anomoly/DoS
detection; Capacity planning, etc XXX
2.4. 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.
3. 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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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
(TCP-AO) [RFC5925]. This TCP option authenticates TCP segments, (TCP-AO) [RFC5925]. This TCP option authenticates TCP segments,
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] was designed to work
layer and authenticates the IP payload. This therefore also at the network layer and authenticate the IP payload. This approach
authenticates all transport headers, and verifies their integrity at authenticates all transport headers, and verifies their integrity at
the receiver, preventing in-network modification. the receiver, preventing in-network modification.
3.2. Encrypting the Transport Payload 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 3.1). check (Section 3.1).
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Mutable fields in the transport header provide opportunities for Mutable fields in the transport header provide opportunities for
middleboxes to modify the transport behaviour (e.g., the extended middleboxes to modify the transport behaviour (e.g., the extended
headers described in [I-D.trammell-plus-abstract-mech]). This headers described in [I-D.trammell-plus-abstract-mech]). This
considers only immutable fields in the transport headers, that is, considers only immutable fields in the transport headers, that is,
fields that may be authenticated End-to-End across a path. fields that may be authenticated End-to-End across a path.
An example of a method that encrypts some, but not all, transport An example of a method that encrypts some, but not all, transport
information is GRE-in-UDP [RFC8086] when used with GRE encryption. information is GRE-in-UDP [RFC8086] when used with GRE encryption.
3.5. Adding Transport Information to Network-Layer Protocol Headers 3.5. Optional Encryption of Header Information
There are implications to the use of optional header encryption in
the design of a transport protocol, where support of optional
mechanisms can increase the complexity of the protocol and its
implementation and in the management decisions that are required to
use variable format fields. Instead, fields of a specific type ought
to always be sent with the same level of confidentiality or integrity
protection.
4. Addition of 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
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It can be undesirable to rely on methods requiring options or It can be undesirable to rely on methods requiring options or
extension headers. IPv4 network options are often not supported (or extension headers. IPv4 network options are often not supported (or
are carried on a slower processing path) and some IPv6 networks are are carried on a slower processing path) and some IPv6 networks are
also known to drop packets that set an IPv6 header extension (e.g., also known to drop packets that set an IPv6 header extension (e.g.,
[RFC7872]). Another disadvantage is that protocols that separately [RFC7872]). Another disadvantage is that protocols that separately
expose header information do not necessarily have an advantage to expose header information do not necessarily have an advantage to
expose the information that is utilised by the protocol itself, and expose the information that is utilised by the protocol itself, and
could manipulate this header information to gain an advantage from could manipulate this header information to gain an advantage from
the network. the network.
4. Implications of Protecting the Transport Headers 5. 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.
4.1. Independent Measurement 5.1. 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).
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information. Protocols that expose the state information used by the information. Protocols that expose the state information used by the
transport protocol in their header information (e.g., timestamps used transport protocol in their header information (e.g., timestamps used
to calculate the RTT, packet numbers used to asses congestion and to calculate the RTT, packet numbers used to asses congestion and
requests for retransmission) provide an incentive for the sending requests for retransmission) provide an incentive for the sending
endpoint to provide correct information, increasing confidence that endpoint to provide correct information, increasing confidence that
the observer understands the transport interaction with the network. the observer understands the transport interaction with the network.
This becomes important when considering changes to transport This becomes important when considering changes to transport
protocols, changes in network infrastructure, or the emergence of new protocols, changes in network infrastructure, or the emergence of new
traffic patterns. traffic patterns.
4.2. Characterising "Unknown" Network Traffic 5.2. 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.
4.3. Accountability and Internet Transport Protocols 5.3. 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 2.2.4. 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. classify and mechanisms to condition network traffic.
A lack of data seems likely to reduce the level of precision with A lack of data seems likely to reduce the level of precision with
which these mechanisms are applied, and this needs to be considered which these mechanisms are applied, and this needs to be considered
when evaluating the impact of designs for transport encryption. This when evaluating the impact of designs for transport encryption. This
could lead to increased use of rate limiting, circuit breaker could lead to increased use of rate limiting, circuit breaker
techniques [RFC8084], or even blocking of uncharacterised traffic. techniques [RFC8084], or even blocking of uncharacterised traffic.
This would hinder deployment of new mechanisms and/or protocols. This would hinder deployment of new mechanisms and/or protocols.
4.4. Impact on Research, Development and Deployment 5.4. Impact on Research, Development and Deployment
There are both opportunities and also challenges to the design,
evaluation and deployment of new transport protocol mechanisms.
Integrity checks can avoiding network devices undetected modification
of protocols, whereas encryption and obfuscation can prevent these
headers being utilised by network devices. This provides greater
freedom to update the protocols and can therefore ease
experimentation with new techniques and their final deployment in
endpoints.
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.
Attention needs to be paid to the expected scale of deployment of new Attention needs to be paid to the expected scale of deployment of new
protocols and protocol mechanisms. Whatever the mechanism, protocols and protocol mechanisms. Whatever the mechanism,
experience has shown that it is often difficult to correctly experience has shown that it is often difficult to correctly
implement combination of mechanisms [RFC8085]. These mechanisms implement combination of mechanisms [RFC8085]. These mechanisms
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 New transport protocol formats are expected to facilitate an
Internet continues to expand - and there has been recent interest in increased pace of transport evolution, and with it the possibility to
a wide range of new transport methods, e.g., Larger Initial Window, experiment with and deploy a wide range of protocol mechanisms.
Proportional Rate Reduction (PRR), congestion control methods based There has been recent interest in a wide range of new transport
on measuring bottleneck bandwidth and round-trip propagation time, methods, e.g., Larger Initial Window, Proportional Rate Reduction
the introduction of AQM techniques and new forms of ECN response (PRR), congestion control methods based on measuring bottleneck
(e.g., DCTP, and methods proposed for L4S). For each new method it is bandwidth and round-trip propagation time, the introduction of AQM
desirable to build a body of data reflecting its behaviour under a techniques and new forms of ECN response (e.g., DCTP, and methods
wide range of deployment scenarios, traffic load, and interactions proposed for L4S).The growth and diversity of applications and
with other deployed/candidate methods. protocols using the Internet also continues to expand. For each new
method or application it is desirable to build a body of data
reflecting its behaviour under a wide range of deployment scenarios,
traffic 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.
5. Acknowledgements 6. Conclusions
XXX Notes for a draft conclusion XXX
The majority of traffic sent by the present Internet uses two well-
known transport protocols: e.g., TCP and UDP.
Although TCP represents the majority of current traffic, some
important real-time applications have used UDP, and much of this
traffic utilises RTP format headers in the payload of the UDP data.
Since these protocol headers have been fixed for decades, a range of
tools and analysis methods have became common and well-understood.
Over this period, the transport protocol headers have mostly changed
slowly, and so also the need to develop tools track new versions of
the protocol.
Encryption (confidentiality and strong integrity checks) have
properties that are being incorporated into new protocols and which
have important benefits. The pace of development of transports using
the WebRTC data channel and the rapid deployment of QUIC prototype
transports can both be attributed to using a combination of UDP
transport and encryption of the UDP payload.
The traffic that can be observed by devices in a network is a
function of transport protocol design/options, network use,
applications and user characteristics. In general, when only a small
proportion of the traffic has a specific (different) characteristic.
Such traffic seldom leads to an operational issue although the
ability to measure and monitor it is less. The desire to understand
the traffic and protocol interactions typically grows as the
proportion of traffic increases in volume. The challenges increase
when multiple instances of an evolving protocol contribute to the
traffic that share network capacity.
An increased pace of evolution therefore needs to be accompanied by
methods that can be successfully deployed and used across operational
networks. This leads to a need for network operators (at various
level (ISPs, enterprises, firewall maintainer, etc) to identify
appropriate operational support functions and procedures.
Protocols that change their transport header format (wire format) or
their behaviour (e.g., algorithms that are needed to classify and
characterise the protocol), will require new tooling needs to be
developed to catch-up with the changes. If the currently deployed
tools and methods are no longer relevant and performance may not be
correctly measured. This can increase the response-time after
faults, and can impact the ability to manage the network resulting in
traffic causing traffic to be treated inappropriately (e.g., rate
limiting because of being incorrectly classified/monitored). There
are benefits in exposing consistent information to the network that
avoids traffic being mis-classified and then receiving a default
treatment by the network.
A protocol specification therefore needs to weigh the benefits of
ossifying common headers, versus the potential demerits of exposing
specific information that could be observed along the network path to
provide tools to manage new variants of protocols. Several scenarios
to illustrate different ways this could evolve are provided below:
o One scenario is when transport protocols provide consistent
information to the network by intentionally exposing a part of the
transport header. The design fixes the format of this information
between versions of the protocol. This level of ossification
allows an operator to establish tooling and procedures that allow
it to provide consistent traffic management as the protocol
evolves. In contrast to TCP (where all protocol information is
exposed), evolution of the transport is facilitated by providing
cryptographic integrity checks of the transport header fields
(preventing undetected middlebox changes) and encryption of other
protocol information (preventing observation within the network).
The transport information can be used by operators to provide
troubleshooting, easement and any necessary functions for the
class of traffic (priority, retransmission, reordering, circuit
breakers, etc).
o An alternative scenario adopts different design goals, with a
different outcome. A protocol that encrypts all header
information forces network operators to act independently from
apps/transport developments to provide the transport information
they need. A range of approaches may proliferate - as in current
networks, operators can add a shim header to each packet as a flow
as it crosses the network ; other operators/managers could develop
heuristics and pattern recognition to derive information that
classifies flows and estimates quality metrics for the service
being used; some could decide to rate-limit or block traffic until
new tooling is in place. In many cases, the derived information
can be used by operators to provide necessary functions for the
class of traffic (priority, retransmission, reordering, circuit
breakers, etc). Troubleshooting, and measurement becomes more
difficult or could require additional information. In some cases,
operators might need access to keying information to interpret
encrypted data that they observe. Some use cases could demand use
of transports that do not use encryption.
The outcome could have significant implications on the way the
Internet architecture develops. It exposes a risk that significant
actors (e.g., developers and transport designers) achieve more
control of the way in which the Internet architecture develops.In
particular, there is a possibility that designs could evolve to
significantly benefit of customers for a specific vendor, and that
communities with very different network, applications or platforms
could then suffer at the expense of benefits to their vendors own
customer base. In such a scenario, there could be no incentive to
support other applications/products or to work in other networks
leading to reduced access for new approaches.
7. 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.
6. Security Considerations 8. Security Considerations
This document is about design and deployment considerations for This document is about design and deployment considerations for
transport protocols. 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 23, line 34 skipping to change at page 27, line 51
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.
7. IANA Considerations 9. IANA Considerations
XX RFC ED - PLEASE REMOVE THIS SECTION XXX XX RFC ED - PLEASE REMOVE THIS SECTION XXX
This memo includes no request to IANA. This memo includes no request to IANA.
8. References 10. References
10.1. 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>.
8.2. Informative References 10.2. 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 28, line 50 skipping to change at page 33, line 7
-04 This adds an additional contributor 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.
-05 Corrections received and helpful inputs from Mohamed Boucadair. -05 Corrections received and helpful inputs from Mohamed Boucadair.
-06 Updated following comments from Stephen Farrell, and feedback via
email. Added a draft conclusion section to sketch some strawman
scenarios that could emerge.
Authors' Addresses Authors' Addresses
Godred Fairhurst Godred Fairhurst
University of Aberdeen University of Aberdeen
Department of Engineering Department of Engineering
Fraser Noble Building Fraser Noble Building
Aberdeen, AB24 3UE Aberdeen, AB24 3UE
Scotland Scotland
Email: gorry@erg.abdn.ac.uk Email: gorry@erg.abdn.ac.uk
URI: http://www.erg.abdn.ac.uk/ URI: http://www.erg.abdn.ac.uk/
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