The Impact of Transport Header Encryption on Operation and Evolution of the Internet
draft-fairhurst-tsvwg-transport-encrypt-00
The information below is for an old version of the document.
| Document | Type |
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|---|---|---|---|
| Author | Gorry Fairhurst | ||
| Last updated | 2017-05-28 | ||
| Replaced by | draft-ietf-tsvwg-transport-encrypt, draft-ietf-tsvwg-transport-encrypt, RFC 9065 | ||
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draft-fairhurst-tsvwg-transport-encrypt-00
TSVWG G. Fairhurst
Internet-Draft University of Aberdeen
Intended status: Informational May 29, 2017
Expires: November 28, 2017
The Impact of Transport Header Encryption on Operation and Evolution of
the Internet
draft-fairhurst-tsvwg-transport-encrypt-00
Abstract
This document describes the implications of applying end-to-end
encryption at the transport layer. It identifies some in-network
uses of transport layer header information that can be used with
transport header authentication,. It reviews the implication of
developing encrypted end-to-end transport protocols and examines the
implication of developing and deploying encrypted end-to-end
transport protocols.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 28, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (http://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text
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as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Internet Transports and Pervasive Encryption . . . . . . . . . 4
2.1. Authenticating the Transport Protocol Header . . . . . . . 5
2.2. Encrypting the Transport Payload . . . . . . . . . . . . . 5
2.3. Encrypting the Transport Header . . . . . . . . . . . . . 6
2.4. Authenticating Transport Information and Selectively
Encrypting the Transport Header . . . . . . . . . . . . . 6
2.5. Adding transport information to network-layer Protocol
Headers . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Use of Transport Headers in the Network . . . . . . . . . . . 7
3.1. Use to Identify Flows . . . . . . . . . . . . . . . . . . 9
3.2. Use to derive Traffic Statistics . . . . . . . . . . . . . 9
3.2.1. Use to Characterise Traffic Rate and Volume . . . . . 9
3.2.2. Use of the Network-Layer DSCP . . . . . . . . . . . . 10
3.2.3. Measuring Loss rate and Loss Pattern . . . . . . . . . 10
3.2.4. Measuring Throughput and Goodput . . . . . . . . . . . 11
3.2.5. Measuring Latency (Network Transit Delay and Jitter) . 11
3.2.6. Measuring Flow Reordering . . . . . . . . . . . . . . 12
3.3. Network-Layer Header Information . . . . . . . . . . . . . 13
3.3.1. Use of IPv6 Network-Layer Flow Label . . . . . . . . . 13
3.3.2. Use Network-Layer Differentiated Services Code Point
Point (DSCP) . . . . . . . . . . . . . . . . . . . . . 13
3.3.3. Use of Explicit Congestion Marking . . . . . . . . . . 13
3.4. Use by Operators to Plan and Provision Networks . . . . . 14
3.5. Use for Network Diagnostics and Troubleshooting . . . . . 14
3.6. Verification of Acceptable Response to Congestion . . . . 15
3.6.1. Impact on Network Operations . . . . . . . . . . . . . 16
3.6.2. Accountability and the Evolution of Internet Transport 17
4. The Effect of Encrypting Transport Header Fields . . . . . . . 17
4.1. Flow Identifier . . . . . . . . . . . . . . . . . . . . . 17
4.1.1. Identification by a well-known Transport Port . . . . 18
4.1.2. Use of a Transport as a Substrate . . . . . . . . . . 18
4.1.3. Mobility and Flow Migration . . . . . . . . . . . . . 18
4.1.4. IPv6 Network-Layer Flow Label . . . . . . . . . . . . 19
4.1.5. Flow Start and Stop Indicator . . . . . . . . . . . . 19
4.2. Use of Transport Sequence Number . . . . . . . . . . . . . 19
4.3. Use of Transport Sequence Acknowledgment Number . . . . . 20
4.4. Use of ECN Transport Feedback Information . . . . . . . . 20
4.5. Interpretation of Transport Header Fields . . . . . . . . 21
5. Implications on Evolution of the Internet Transport . . . . . 21
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 24
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
8. Security Considerations . . . . . . . . . . . . . . . . . . . 25
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
9.1. Normative References . . . . . . . . . . . . . . . . . . . 25
9.2. Informative References . . . . . . . . . . . . . . . . . . 25
Appendix A. Revision information . . . . . . . . . . . . . . . . . 29
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 29
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1. Introduction
This document discusses the implications of end-to-end encryption
applied at the transport layer, and examines the impact on transport
protocol design, transport use, and network operations and
management. It also considers some anticipated implications on
transport and application evolution.
The transport layer is the first end-to-end layer in the network
stack. Despite headers having end-to-end meaning, transport headers
have come to be used in various ways within the Internet. In
response to pervasive monitoring [RFC7624] revelations and the IETF
consensus that "Pervasive Monitoring is an Attack" [RFC7258], efforts
are underway to increase encryption of Internet traffic, which
prvents visibility of transport headers, and have implications on how
network protocols are designed and used (e.g., [I-D.mm-wg-effect-
encrypt]).
Transport information that is sent without end-to-end authentication
could be modified by "middleboxes" - defined as any intermediary box
performing functions apart from normal, standard functions of an IP
router on the data path between a source host and destination host
[RFC3234]. When transport headers are modified by network devices on
the path this can change the end-to-end protocol transport protocol
behaviour in a way that may benefit the user or may hinder transport
performance and application experience. Whatever the outcome,
modification of packets by a middlebox was not usually intended when
the protocol was specified and is usually not known by the sender or
receiver.
Middleboxes have been deployed for a variety of reasons [RFC3234],
including middlebox protocol enhancement, proxy-based methods, such
as Protocol Enhancing Proxies (PEPs) [RFC3135], TCP acknowledgement
(ACK) enhancement [RFC3449], use of application protocol caches [I-D
.mm-wg-effect-encrypt], application layer gateways [I-D.mm-wg-effect-
encrypt], etc. [I-D.dolson-plus-middlebox-benefits] summarizes some
of the functions provided to the Internet by such middleboxes, and
the benefits that may arise when they are used in a number of
deployment scenarios. Methods that involve in-network modification
of transport headers are not further discussed.
This document notes that transport protocols can be designed to
encrypt or authenticate transport header fields. Authentication
methods can be used at the transport layer to detect any changes to
an immutable header field that were made by a network device along a
path. These methods do not require encryption of the header fields
and hence these fields may remain visible to network devices. End-
to-end authentication allows the receiving transport endpoint to
avoid accepting modified protocol headers. This document therefore
considers the case where protocol fields in the transport header are
not altered as a packet traverses the network path.
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Authentication methods have also been specified at the network layer,
and cover fields not protected by a transport authentication header.
Network layer header fields can convey codepoints that are
increasingly being used to help forwarding decisions reflect the need
of transport protocols, such the IPv6 Flow Label [RFC6437], the
Differentiated Services Code Point (DSCP) [RFC2474] and Explicit
Congestion Notification (ECN) [RFC3168].
Encryption methods can help to hide information from an eavesdropper
in the network. Encryption can also help protect the privacy of a
user, by hiding data relating to user/device identity or location.
Neither authentication nor encryption methods prevent traffic
analysis, and usage needs to reflect that profiling of users and
fingerprinting of behaviour can take place even on encrypted traffic
flows.
This document seeks to identify the implications of various
approaches to transport protocol authentication and encryption.
2. Internet Transports and Pervasive Encryption
End-to-end encryption can be applied at various protocol layers. It
can be applied above the transport to encrypt the transport payload.
One motive to use encryption is a response to perceptions that the
network has become ossified by over-reliance on middleboxes that
prevent new protocols and mechanisms from being deployed. This has
lead to a common perception that there is too much "manipulation" of
protocol headers within the network, and that designing to deploy in
such networks is preventing transport evolution. In the light of
this, a method that authenticates transport headers may help improve
the pace of transport development, by eliminating the need to always
consider deployed middleboxes [I-D.trammell-plus-abstract-mech], or
potentially to only explicitly enable middlebox use for particular
paths with particular middleboxes [RFC3135].
Another perspective stems from increased concerns about privacy and
surveillance . Some Internet users have valued the ability to protect
identity and defend against traffic analysis, and have used methods
such as IPsec ESP and Tor [Tor]. Revelations about the use of
pervaisive surveillance [RFC7624] have, to some extent, eroded trust
in the service offered by network operators, and following the
Snowden revelation in the USA in 2013 has led to an increased desire
for people to employ encryption to avoid unwanted "eavesdropping" on
their communications. Whatever the reasons, there are now activities
in the IETF to design new protocols that may include some form of
transport header encryption (e.g., QUIC [I-D.ietf-quic-transport]).
The use of transport layer authentication and encryption exposes a
tussle between middlebox vendors, operators, applications developers
and users.
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o On the one hand, future Internet protocols that enable large-scale
encryption assist in the restoration of the end-to-end nature of
the Internet by returning complex processing to the endpoints,
since middleboxes cannot modify what they cannot see.
o On the other hand, encryption of transport layer header
information has implications to people responsible for operating
networks and researchers and analysts seeking to understand the
dynamics of protocols and traffic patterns.
Whatever the motives, a decision to use pervasive of transport header
encryption will have implications on the way in which design and
evaluation is performed, and which canin turn impact the direction of
evolution of the TCP/IP stack.
The next subsections briefly review some security design options for
transport protocols.
2.1. Authenticating the Transport Protocol Header
Transport layer header information can be authenticated. An
authentication method protects the integrity of immutable transport
header fields, but can still expose the transport protocol header
information in the clear, allowing in-network devices to observes
these fields. Authentication can not prevent in-network
modification, but can avoid accepting changes and avoid impact on the
transport protocol operation.
An example transport authentication mechanism is TCP-Authentication
(TCP-AO) [RFC5925]. This TCP option authenticates TCP segments,
including the IP pseudo header, TCP header, and TCP data. TCP-AO
protects the transport layer, preventing attacks from disabling the
TCP connection itself. TCP-AO may interact with middleboxes,
depending on their behavior [RFC3234].
The IPSec Authentication Header (AH) [RFC4302] works at the network
layer and authenticates the IP payload. This therefore also
authenticates all transport headers, and verifies their integrity at
the receiver, preventing in-network modification.
2.2. Encrypting the Transport Payload
The transport layer payload can be encrypted to protect the content
of transport segments. This leaves transport protocol header
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information in the clear. The integrity of immutable transport
header fields could be protected by combining this with
authentication methods (Section 2.1).
Examples of encrypting the payload include TLS over TCP [RFC5246]
[RFC7525] or DTLS over UDP [RFC6347] [RFC7525].
2.3. Encrypting the Transport Header
The network layer payload could be encrypted (including the entire
transport header and payload). This method does not expose any
transport information to devices in the network, which also prevents
modification along the network path.
The IPSec Encapsulating Security Payload (ESP) [RFC4303] is an
example of encryption at the network layer, it encrypts and
authenticates all transport headers, preventing visibility of the
headers by in-network devices. Some Virtual Private Network (VPN)
methods also encrypt these headers.
2.4. Authenticating Transport Information and Selectively Encrypting
the Transport Header
A transport protocol design can encrypt selected header fields, while
also choosing to authenticate some or all of other fields in the
transport header. This allows only specific transport header fields
to be observable by network devices. End-to end authentication can
prevent an endpoint from undetected modification of the immutable
transport headers.
The choice of which fields to expose and which to encrypt is a design
choice for the transport protocol. Any selective encryption method
requires trading two conflicting goals for a transport protocol
designer to decide which header fields to encrypt. On the one hand,
security work typically employs a design technique that seeks to
expose only what is needed. On the other hand, there may be
performance and operational benefits in exposing selected information
to network tools.
Mutable fields in the transport header provide opportunities for
middleboxes to modify the transport behaviour (e.g., the extended
headers described in [I-D.trammell-plus-abstract-mech]). This
considers only the use of immutable fields in the transport headers,
that is, fields that could be authenticated end-to-end across a
transport path.
An example of a method that encrypts some, but not all, transport
information is UDP-in-GRE [RFC8086] when it is used with GRE
encryption.
2.5. Adding transport information to network-layer Protocol Headers
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The transport information can be made visible in a network-layer
header. This has the advantage that this information can then be
observed by in-network devices. This has the advantage that a single
header can support all transport protocols, but there may also be
less desirable implications of separating the operation of the
transport protocol from the measurement framework.
Some measurements may be made by adding additional packet headers
carrying operations, administration and management (OAM) information
to packets at the ingress to a maintenance domain (e.g., adding an
Ethernet protocol header with timestamps and sequence number
information using a method such as 802.11ag) and removing the
additional header at the egress of the maintenance domain. This
approach enables some types of measurements, but does not cover the
entire range of measurments described in this document.
Another example of a network-layer approach is the IPv6 Performance
and Diagnostic Metrics (PDM) Destination Option [I-D.ietf-ippm-6man-
pdm-option]. This allows a sender to optionally include a
destination option that cariies header fields that can be used to
observe timestamps and packet sequence numbers. Transmission of the
packets with thsi option can be impacted by destination-options
processing by network devices. This information could be
authenticated by receiving transport endpoints when the information
is added at the sender and visible at the receiving endpoint,
although methods to do this have not currently been proposed. This
method needs to be explicitly enabled at the sender.
A drawback of using extension headers is that IPv4 network options
are often not supported (or are carried on a slower processing path)
and some IPv6 networks are also known to drop packets that set an
IPv6 header extension. Another disadvantage is that protocols that
seprately expose header information do not necessarily have an
advantage to expose the information that is utilised by the protocol
itself, and could manipulate this header information to gain an
advantage from the network.
3. Use of Transport Headers in the Network
This section identifies ways that observable (non-encrypted)
transport header fields can be used by devices in the network. There
are a number of actors who can benefit from observing this
information. These include:
o Protocol developers and implementors of TCP/IP stacks;
o Researchers working on new mechanisms or new applications of
existing applications;
o Analysis researching the impact of mechanisms on network equipment
or specific network topologies;
o Staff supporting operation of a network.
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When encryption conceals more layers in a packet, people seeking
understanding of the network operation need to rely more on pattern
inferences and other heuristics. The accuracy of measurements
therefore suffers, as does the ability to investigate and
troubleshoot interactions between different anomalies. For example,
the traffic patterns between server and browser are dependent on
browser supplier and version, even when the sessions use the same
server application (e.g., web e-mail access). Even when measurment
datasets are made available (e.g., from endpoints) additional
metadata (such as the state of the network) is often required to
interpret the data, collecting such metadata is more difficult when
the observation point is at a different location to the bottleneck/
equipment under evaluation.
To observe protocol headers requires knowledge of the format of the
transport header. In-network observation of transport protocol
headers requires:
o Flows to be identified at the level required for monitoring. In
IETF transports, this is typically identified by the ports field.
o Knowledge of the protocol being used. In some usages, well-known
ports can be identified from the low-numbered port that can
identify a protocol (although port information alone is not
sufficient to guarentee identification of the protocol).
o To know the position and syntax of any transport headers that need
to be observed. IETF transport protocols specify this
information.
If there is more than one format for visible headers, the observer
needs to know the protocol that is used. As protocols evolve over
time and there mau be a need to introduce new transport headers.This
may require interpretation of protocol version information.TCP and
SCTP specify a standard base header that includes sequence number
information and other data. TCP and SCTP options may be negotiated
to indicate the presence of new (negotiated) features, the size and
function of each option is identified by an option number in the
transport header.
Protocols that expose header information that is utilised by the
protocol itself provide an incentive for the endpoints to provide
correct information.
Packet sampling techniques can be used to scale processing involved
in observing apckets on high rate links. This only exports the
packet header information of (randomly) selected packets. The
utility of these measurements depends on the type of bearer and
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number of mechanisms used by network devices. Simple routers are
relatively easy to manage, a device with more complexity demands
understanding of the choice of many system parameters. This level of
complexity exists when several network methods are combined.
The following subsections describe various ways that observable
transport information may be utilised.
3.1. Use to Identify Flows
Transport protocol header infromation can identify the connection
state of a flow, and identify separate flows operating over a path.
Connection information can assist a firewall in deciding which flows
are permitted through a security gateway [I-D.trammell-plus-
statefulness], or to help maintain the network address translation
(NAT) bindings in a NAPT or application layer gateway. This
information may also find use in load balancers, where visibility of
the 5-tuple and meaningful use could be used as a method for
determining forwarding or selecting a server [I-D.mm-wg-effect-
encrypt].
The use of UDP as a substrate protocol is discussed further in
Section 4.1.2, and the implications of mobility bindings in Section
4.1.3.
3.2. Use to derive Traffic Statistics
Passive monitoring uses observed traffic to makes inferences frok
transport headers to derive measurements. A variety of open source
and commecial tools exists that can utilise the information in RTP
and RTCP headers to derive traffic volume measurements and provide
infromation on the progress and quality of a session using RTP.
Any Internet transport or application could report data to the
network, by sending status packets or by providing access to
measurement data. However, to be useful a user of measurement data
needs to trust the source of this data and importantly require
metadata to understand the context under which the data was
collected, including the time, observation point, and way in which
metrics were accumulated.
When encryption conceals information in packet headers, measurments
need to rely on pattern inferences and other heuristics grows, and
accuracy suffers [I-D.mm-wg-effect-encrypt].
3.2.1. Use to Characterise Traffic Rate and Volume
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Operators can measure per-subscriber information about the volume and
pattern of network usage. Transport headers may be observed on a
per-application (or per endpoints) basis. Capacity usage ican be
valuable for capacity planning (providing more detail of trends
rather than the volume per subscriber). This can also be used for
measurement-based traffic shaping and to implement QoS support within
the network and lower layers.
3.2.2. Use of the Network-Layer DSCP
Applications can expose their delivery expectations to the network
allowing endpoints to encode in the Differentiated Services Code
Point (DSCP) field of IPv4 and IPv6 packets. Setting this field
provides explicit information that can be used in place of inferring
traffic requirements (e.g., by inferring QoS requirements from port
information via a multi-field classifier). This information can be
collected by measurement campaigns, but does not directly provide any
performance data.
3.2.3. Measuring Loss rate and Loss Pattern
Various actors have a need to characterise link/network segments and
derive key performance indicators (retransmission rate, packet drop
rate, sector utilization Level, a measure of reordering, peak rate,
the CE-marking rate, etc.). The quality of a transport path may be
assessed using dedicated tools that generate test traffic. However
such tools need to be run from an endpoint, and most operators do not
have access to this equipment. There also may be costs associated
with running such tests. (e.g., the implications of bandwidth tests
in a mobile network are obvious.) An alternative is to use in-network
techniques that observe visible transport packet sequence numbers to
determine transport flow statistics.
The design tradeoffs for radio networks are often very different to
those of wired networks. A radio-based network (e.g., cellular
mobile, enterprise WiFi, satellite access/backhaul, 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 pattern of loss and
congestion, impact of different traffic types, correlation with
propagation and interference measures can all have significant impact
on the cost and performance of providing a service. The need for
this type of information is expected to increase as operators seek to
bring together heterogeneous types of network equipment and seek to
deploy opportunistic methods to access radio spectrum.
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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. Often
impact is only understood in the context of the other flows that
share a bottleneck. In summary, the common language between network
operators and application/content providers/users is packet transfer
performance at a layer that all can view and analyze. For most
packets, this has been transport layer, until the emergence of QUIC,
with the obvious exception of VPNs and IPsec.
A simple example is the monitoring of Active Queue Management (AQM).
For example, FQ-CODEL [I-D.ietf-aqm-fq-codel], combines sub queues
(statistically assigned per flow), management of the queue length
(CODEL), flow-scheduling, and a starvation prevention mechanism.
Usually such algorithms are designed to be self-tuning, but current
methods typically employ heuristics that can result in more loss
under certain path conditions (e.g., large RTT, effects of multiple
bottlenecks [RFC7567]).
3.2.4. Measuring Throughput and Goodput
The throughput observed by a flow can be determined even when a flow
is encrypted, providing the individual flow can be identified.
Goodput [RFC7928] is a measure of useful data exchanged (the ratio of
useful/total volume of traffic sent by a flow), which requires
ability to differentiate the different ways packets are used at the
remote endpoint (e.g., by observing duplicate packet sequence numbers
in TCP).
3.2.5. Measuring Latency (Network Transit Delay and Jitter)
Latency is a key performance metric that impacts application response
time and user perceived response time. This often indirectly impacts
throughput and flow completion time. It also determines the reaction
time of the transport protocol itself, impacting flow setup,
congestion control, loss recovery, and other transport mechanisms.
The overall latency can have many components [Latency], but of these
unnecessary/unwanted queuing in network buffers has often been
observed as a significant factor. Once the cause of unwanted latency
has been identified, this can often be eliminated, and determining
latency metrics is a key driver in the deployment of AQM [RFC7567],
DiffServ [RFC2474], and ECN [RFC3168] [RFC8087].
To measure latency across a part of the path, an observation point
has to measure the experienced round-trip time (RTT). This can be
achieved using packet sequence numbers, and acknowledgement points.
An observation point in the network is able to determine not only the
path RTT, but also to measure the upstream and downstream RTT,
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respectively to the sending and receiving endpoints. 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 of a path.
An example usage of this method could be to identify excessive
buffers and to deploy or configure Active Queue Management (AQM)
[RFC7567] [RFC7928]. Operators deploying such tools can effectively
eliminate unnecessary queuing in routers and other devices. AQM
methods need to be deployed at the capacity bottleneck, but are often
deployed in combination with other techniques, such as scheduling
[RFC7567] [I-D.ietf-aqm-fq-codel] and although parameter-less methods
are desired [RFC7567], current methods [I-D.ietf-aqm-fq-codel] [I-D
.ietf-aqm-codel] [I-D.ietf-aqm-pie] often cannot scale across all
possible deployment scenarios. The service offered by operators can
therefore benefit from latency information to understand the impact
of deployment and tune deployed services.
Some network applications are sensitive to packet jitter, and to
support this type of application, it can be useful to monitor the
jitter observed along a portion of the path. The requirements to
measure jitter resemble those for the measurement of latency.
3.2.6. Measuring Flow Reordering
Significant flow reordering can impact time-critical applications and
can be interpreted as loss by reliable transports. Many transport
protocols (e.g., TCP) therefore use technqiues that are impacted
reordering. Packet reordering can occur for many reasons (from
equipment design to misconfiguration of forwarding rules). As in the
drive to reduce network latency, there is a need for operational
tools to be able to detect misordered packet flows and quantify the
degree or reordering. Techniques for measuring reordering typically
observe packet sequence numbers. Metrics have been defined that
evaluate whether a network has maintained packet order on a packet-
by-packet basis [RFC4737] and [RFC5236].
There has been initiatives in the IETF transport area to reduce the
impact of reordering withing a transport flow, possibly leading to
reduced the requirements for ordering. These have promise to
simplify network equipment design as well as the potential to improve
robustness of the transport service. Measurements of reordering can
help understand the level of reordering within deployed
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infrastructure, and inform decisions about how to progress such
mechanisms.
3.3. Network-Layer Header Information
Some network-layer information is closely tied to transport protocol
operation.
3.3.1. Use of IPv6 Network-Layer Flow Label
Endpoints should expose flow information in the IPv6 Flow Label field
of the network-layer header (e..g. [RFC8085]). This can be used to
inform network-layer queuing, forwarding (e.g., for equal cost multi-
path (ECMP) routing, and Link Aggregation (LAG)). This can provide
useful information to assign packets to flows in the data collected
by measurement campaigns, but does not directly provide any
performance data.
3.3.2. Use Network-Layer Differentiated Services Code Point Point
(DSCP)
Application should expose their delivery expectations to the network
allowing endpoints to encode in the Differentiated Services Code
Point (DSCP) field of IPv4 and IPv6 packets. This can be used to
inform network-layer queuing and forwarding, and can also provide
information on the relative importance of packet information
collected by measurement campaigns, but does not directly provide any
performance data.
Setting this field provides explicit information that can be used in
place of inferring traffic requirements (e.g., by inferring QoS
requirements from port information via a multi-field classifier).
3.3.3. Use of Explicit Congestion Marking
Explicit Congestion Notification (ECN)[RFC3168] uses a codepoint in
the network-layer header. This exposes the presence of congestion on
a network path to the transport and network layer. Use of ECN can
offer gains in terms of increased throughput, reduced delay, and
other benefits when used over a path that includes equipment that
supports an AQM method that performs Congestion Experienced (CE)
marking of IP packets [RFC8087].
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ECN CE-marks are visible to in-network devices on the transport path.
The reception of CE-marked packets can therefore be used to monitor
the presence and estimate the level of incipient congestion on the
upstream portion of the path from the point of observation (Section
2.5 of [RFC8087]). Because ECN marks carried in the IP protocol
header, measuring ECN can be much easier than metering packet loss.
However, interpretting the marking behaviour (i.e., assessing
congestion and diagnosing faults) requires context from the transport
layer (path RTT, visibility of loss - that could be due to queue
overflow, congestion response, etc) [RFC7567].
Some proposed ECN-capable network devices provide richer (more
frequent and fine-grained) indication of their congestion state.
setting congestion marks proportional to the level of congestion
(e.g., DCTP [I-D.ietf-tcpm-dctcp], and L4S [I-D.ietf-tsvwg-l4s-
arch]).
AQM and ECN can use and combine a range of algorithms and
configuration options, it is therefore important for tools to be
available to network operators and researchers to understand the
implication of configuration choices and transport behaviour as use
of ECN increases and new methods emerge [RFC7567] [RFC8087]. ECN-
monitoring is expected to become important as AQM is deployed that
supports ECN [RFC8087]
Section Section 4.4 describes the transport layer feedback
information that accompanies the use of ECN.
3.4. Use by Operators to Plan and Provision Networks
Traffic measurements can and is used by operators to help plan
deployment of new equipment and configurations in their networks.
Data is also important to equipment vendors who also need to
understand trends in the volume of traffic and the patterns of usage
as inputs to decisions about planning and provisioning.
If the "unknown" or "uncharacterised" traffic forms a small part of
the traffic aggregate, the dynamics of this traffic may not have a
significant collateral impact on the other traffic that shares a
network segment. Once the proportion of traffic increases, the need
to monitor the traffic and determine if appropriate safety measures
need to be put in place.
3.5. Use for Network Diagnostics and Troubleshooting
Transport header information is useful for a variety of operational
tasks [I-D.mm-wg-effect-encrypt]: to diagnose network problems,
assess performance, capacity planning, management of denial of
service threats, and responding to user performance questions. These
tasks seldom involve the need to determine the contents of the
transport payload, or other application details.
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In-network measurements that can distinguish between upstream and
downstream metrics with respect to the measurement point are
particularly useful to locating the source of problems or to asses
the performance of a network segment.
A network operator supporting traffic that uses transport header
encryption can see only encrypted transport headers. This prevents
deployment of performance measurement tools that rely on transport
protocol information. Choosing to encrypt all information may be
expected to reduce the ability for networks to "help" (e.g. in
response to tracing issues, making appropriate Quality of Service,
QoS, decisions). For some this will be blessing, for others it may be
a curse. For example, operational performance data about encrypted
flows needs to be determined by traffic pattern analysis, rather than
relying on traditional tools. This can impact the ability of the
operator to respond to faults, it could require reliance on endpoint
diagnostic tools or user involvement in diagnosing and
troubleshooting unusual use cases or non-trivial problems. Although
many network operators utilise transport information as a part of
their operational practice, the network will not break because
transport headers are encrypted.
3.6. Verification of Acceptable Response to Congestion
Many network operators implicitly accept that TCP traffic to conform
to a behaviour that is acceptable for use in the shared Internet.
TCP algorithms have been continuously improved over decades, and they
have reached a level of efficiency and correctness that custom
application-layer mechanisms will struggle to easily duplicate
[RFC8085]. A standards-compliant TCP stack provides congestion
control that is therefore judged safe for use across the Internet.
Applications developed on top of well-designed transports can be
expected to appropriately control their network usage, reacting when
the network experiences congestion, by back-off and reduce the load
placed on the network. This is the normal expected behaviour for TCP
transports.
Tools exist that can interpret the transport protocol header
information to help understand the impact of specific transport
protocols (or protocol mechanisms) on other traffic that shares their
network. An observation in the network can gain understanding of the
dynamics of a flow and its congestion control behaviour, by observing
TCP sequence numbers to show how a flow shares available capacity,
deduce its congestion dynamics, etc. (e.g., it is common to
visualise plots of TCP sequence numbers versus time [Osterman]).
Analysing packet sequence numbers can be used to help understand
whether an application flow backs-off its share of the network load
in the face of persistent congestion, and hence to understand whether
the behaviour is appropriate for sharing limited network capacity.
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The User Datagram Protocol (UDP) provides a minimal message-passing
transport that has no inherent congestion control mechanisms.
Because congestion control is critical to the stable operation of the
Internet, applications and other protocols that choose to use UDP as
an Internet transport must employ mechanisms to prevent congestion
collapse, avoid unacceptable contributions to jitter/latency, and to
establish an acceptable share of capacity with concurrent traffic
[RFC8085]. A network operator has no way of knowing the specific
methods used by UDP applications, and an operator may need to deploy
methods such as rate-limited, transport circuit breakers or other
methods to enforce acceptable usage.
UDP flows can also expose a well-known header by specifying the
format of header fields. This information can be observed to gain
understanding of the dynamics of a flow and its congestion control
behaviour. For example, tools exist to monitor various aspects of
the RTP and RTCP header information of real-time flows (see Section
3.2).
Independent observation by multiple actors is important for
scientific analysis, and ability to validate the behaviour in-situ
within a network is important. Transport header encryption changes
the ability for other actors to collect and independently analyse
data. This is important when considering transport protocols (e.g.,
changes to transport mechanisms, changes in network infrastructure,
and changes in the transport use).
The growth and diversity of applications and protocols using the
Internet continues to expand - and there has been recent interest in
a wide range of new transport methods, e.g., Larger Initial Window,
Proportional Rate Reduction (PRR), BBR, the introduction of active
queue management (AQM) techniques and new forms of ECN response
(e.g., Data Centre TCP, DCTP [I-D.ietf-tcpm-dctcp], and methods
proposed for Low Latency Low Loss Scalable throughput, L4S). For
each new method 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.
This has implications:
3.6.1. Impact on Network Operations
By correlating observations at multiple points along the path (e.g.
at the ingress and egress of a network segment), an observer can
determine the contribution of a portion of the path to an observed
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metric (to locate a source of delay, jitter, loss, reordering,
congestion marking, etc).
Information provided by tools can help determine whether mechanisms
are needed in the network to prevent flows from acquiring excessive
network capacity. Operators can manage traffic flows (e.g., to
prevent flows from acquiring excessive network capacity under severe
congestion) by deploying rate-limiters, traffic shaping or network
transport circuit breakers [RFC8084].
3.6.2. Accountability and the Evolution of Internet Transport
One often used premise is to "trust but verify" the behaviours of
protocol using the network.
Internet transport protocols employ a set of mechanisms. Some of
these need to work in cooperation with the network layer - loss
detection and recovery, congestion detection and congestion control,
some of these need to work only end-to-end (e.g., parameter
negotiation, flow-control. Whatever the mechanism, experience has
shown that it is often difficult to correctly implement combination
of mechanisms [RFC8085]. These mechanisms therefore typically evolve
as a protocol matures, or in response to changes in network
conditions, changes in network traffic or changes to application
usage.
Measurement have a critical role in the design of transport protocol
mechanisms and their acceptance by the wider community (e.g., as a
method to judge the safety for Internet deployment. Open standards
suggest that such evaluation needs to include independent observation
and evaluation of performance data.
4. The Effect of Encrypting Transport Header Fields
This section examines implications of encrypting specific transport
header fields.
4.1. Flow Identifier
To measure and analyse flow traffic, a measurement tool needs to be
able to identify traffic flows. Aggregation of sessions, and
persistent use of established transport flows by multiple sessions
means that a flow at the transport layer is not necessarily the same
as a flow seen at the application layer. This is usually not a
consequence, and data is measured for the aggregate transport flow.
If flow information is observed from transport headers, then there
needs to be a way to identify the format of the header - such as
observing parameter negotiation at connection setup, identifying the
protocol version from other data (e.g., a "magic" number embedded in
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the header). This allows an observer to determine the presence, size
and position of any observable header fields fro protocol
decapsulation (decoding).
Some measurement methods sample traffic, rather than collecting all
packets passing through a measurement point. These methods still
require a way to determine the presence, size and position of any
observable header fields.
4.1.1. Identification by a well-known Transport Port
All IETF-defined transport protocols include a transport port field
in their transport header. Observation of a well-known port value
may be indicative of the protocol being encapsulated, but there is no
way to enforce this usage. This can be used to configure
decapsulation. This is not the necessarily case, e.g., RTP traffic
may utilise ephemeral ports, requiring measurement tools to include
additional methods to determine the protocol being used.
4.1.2. Use of a Transport as a Substrate
When a transport is used as a substrate, the transport provides an
encapsulation that allows another transport flow to be within the
payload of a transport flow. The transported protocol header may
provide additional information for multiplexing multiple flows over
the same 5-tuple. The UDP Guidelines [RFC8085] provides some
guidance on using UDP as a substrate protocol. If there is no
additional information about the protocol transported by the
substrate, this may be viewed as an opaque traffic aggregate.
Examples include GRE-in-UDP, SCTP-in-UDP. GRE-in-UDP may include an
encryped payload, but does not encrypt the GRE protocol header.
4.1.3. Mobility and Flow Migration
With the proliferation of mobile connected devices, there is a stated
need for connection-oriented protocols to maintain connections after
a network migration by an endpoint. The ability and desirability of
in-network devices to track such migration depends on the context.
On the one hand, a load-balancer device in front of server may find
it useful to map a migrated connection to the same server endpoint.
On the other hand, a user performing migration to avoid detection may
prefer the network not to be able to correlate the different parts of
a migrating session. Care must then be exercised to make sure that
the information encoded by the endpoints is not sufficient to
identify unique flows and facilitate a persistent surveillance attack
vector [I-D.mm-wg-effect-encrypt].
The impact of flow migration on measurement activities depends on the
data being measured, rate of migration and level of encryption that
is employed.
Requirements for load balancing and mobility can lead to complex
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protocol interactions.
QUIC is an example of a transport protocol designed to provide
mobolity, which is in development by the IETF.
4.1.4. IPv6 Network-Layer Flow Label
Endpoints should expose flow information in the IPv6 Flow Label field
of the network-layer header (e..g. [RFC8085]). This can be used to
inform network-layer queuing, forwarding (e.g., for equal cost multi-
path (ECMP) routing, and Link Aggregation (LAG)). This can provide
useful information to assign packets to flows in the data collected
by measurement campaigns, but does not directly provide any
performance data.
4.1.5. Flow Start and Stop Indicator
Transports can expose that start and end of flows in a transport
header field (e.g., TCP SYN, FIN, RST). This can also help
measurement devices identify the start of flows, or to remove stale
flow information. This use resembles the use by in-network devices
such as firewalls and NAPTs. It provides supplemental information -
flows can start and end at any time, the Internet network layer
provides only a best effort service that allows alternate routing,
reordering, loss, etc, so a network measurement tool can not rely
upon observing these indicators. The time to complete a protoocl
connection and/or session setup can be measured as a peformance
metric.
One consequence of encrypting transport headers, is that this
information is not visible to forwarding devices (such as a NAPT or
Firewall). This may impact the network service. For example, UDP-
based middlebox traversal usually relies on timeouts to remove old
state, since middleboxes are unaware when a particular flow ceases to
be used by an application [RFC8085]. This can often lead to the
state table entries not being kept as long as those for which the
flows are identifiable.
4.2. Use of Transport Sequence Number
The TCP or RTP sequence number can be observed in one direction (the
path that carries data segments). An authenticated header prevents
this field being modified or terminated/split [RFC3135] by a network
device, but allows this to be used to observe progress of the network
flow.
An incrementing sequence number enables detection of loss (either by
correlating ingress and egress value, or when assuming that all
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packets follow a single path), duplication and reordering (with
understanding that not necessarily all packets of a flow follow the
same path, and reordering can complicate processing of observations).
Tools are widely available to interpret RTP and TCP sequence numbers
- ranging from open source tools to dedicated commercial packages.
4.3. Use of Transport Sequence Acknowledgment Number
Acknowledgement (ACK) data provides information about the path from
the network device to the remote endpoint. The information can help
identify packet loss (or the point of loss), RTT, and other network-
related performance parameters (e.g., throughput, jitter,
reordering). Unless this information is correlated with other data
there is no way to disambiguate the cause of impairments (congestion
loss, link transmission loss, equipment failure).
An in-network device must not modify the flow of end-to-end ACK data
when using an authenticated protocol. That is, must not use the in-
network methods described in [RFC3449]. This can impact the
performance and/or efficiency (e.g., cost) of using paths where the
return capacity is limited or has implications on the overall design
(e.g., using TCP with cellular mobile uplinks, DOCSIS uplinks).
The TCP stream can be observed by correlating the stream of TCP ACKs
that flow from a receiver in the return direction. Although these
ACKs are cumulative, and are not necessarily sent on the same path as
the forward data, when visible, their sequence can confirm successful
transmission and the path RTT. In the case of TCP they may also
indicate packet loss (duplicate ACKs).
An RTP session can provide RTCP [RFC3605] [RFC4585] feedback using
the RTP framework. This reception information and can be observed by
in-network measurement devices and can be interpreted to provide a
variety of quality of experience information for the related RTP
flow, as well as basic network performance data (RTT, loss, jitter,
etc).
4.4. Use of ECN Transport Feedback Information
Transport protocols that use ECN Section 3.3.3 need to provide ECN
feedback information in the transport header to inform the sender
whether packets have been received with an ECN CE-mark [RFC3819].
This information can be in the form of feedback once each RTT
[RFC3819] or more frequent. The latter may involve sending a
detailed list of all ECN-marked packets (e.g., [I-D.ietf-tcpm-
accurate-ecn] and [RFC6679]). The detailed information can provide
detail about the pattern and rate of marking. The information
provided in these protocol headers can help a network operator to
understand the congestion status of the forward path and the impact
of marking algorithms on the traffic that is carried [RFC8087].
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IETF specifications for Congestion Exposure (CONEX) [RFC7713] and
Per-congestion Notification (PCN) [RFC5559] are examples of
frameworks that monitor reception reports for CE-marked packets to
support network operations.
4.5. Interpretation of Transport Header Fields
Understanding and analysing transport protocol behaviour typically
demands tracking changes to the protocol state at the transport
endpoints. Although protocols communicate state information in their
protocol headers, a protocol implementation typically also contains
internal state that is not directly visible from observing transport
protocol headers. Effective measurement tools need to consider that
not all packets may be observed (due to drops at the capture tap or
because packets take an alternate route that does not pass the tap).
Some flows of packets may also be encapsulatedmaintenance domain in
other protocols, which further complicates analysis.
Some examples of using network measurements of transport headers to
infer internal TCP state information include:
o The TCP congestion window (cwnd) and slow start threshold
(ssthresh. Tools for analysing in-network performance of TCP may
observe sequence number to infer the current congestion controller
state.)
o The TCP RTT estimator and TCP Retransmission Time Out (RTO) value.
This can be estimated by correlating sequence and acknowledgement
numbers, or possibly by observing TCP timestamp options.
o Use of pacing (and pacing rate) and use of methods such as
Proportional Rate Reduction (PRR) and Congestion Window validation
(CWV). This may be estimated from observing timing of segments
with TCP sequence numbers.
o Receiver window and flow control state. This may be inferred from
information in TCP ACK segments.
o Retransmission state and receiver buffer. This may be inferred
from information in TCP ACK segments (especially when SACK blocks
are provided).
o Use of ACK delay and Nagle algorithm. This may be estimated from
observing timing of segments with TCP sequence numbers.
5. Implications on Evolution of the Internet Transport
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Architectural, the transport layer provides the first end-to-end
interactions across the Internet. The transport protocols are
layered directly over the network service and are sent in the payload
of network-layer packets. However, this simple architecural view
hides one of the core functions of the transport, to discover and
adapt to the properties of the Internet path that is currently being
used. The design of Internet transport protocols is as much about
avoiding the unwanted side effects of congestion, avoiiding
congestion collapse, adapting to changes in the path characteristics,
etc., as it is about end-to-end feature negotiation, flow control and
optimising for performance for a specific application. The IETF
transport community has to date relied heavily on measurement and
insight provided from the wider community to understand the trade-
offs and to inform selection of select appropriate mechansims to
ensure a safe, reliable and robust Internet.
The increasing public concerns about the interference with Internet
traffic have led to a rapidly expanding deployment of encryption to
protect end-user privacy, in protocols like QUIC. At the same time,
network operators and access providers, especially in mobile
networks, have come to rely on the in-network functionality provided
by middleboxes both to enhance performance and support network
operations. This presents a need for architectural changes and new
approaches to the way network transport protocols are designed
[Measure].
There are many motivations for deploying encrypted transports, and
encryption of transport payloads. This document has expanded upon
the expected implications on operational practices when working with
encrypted transport protocols, and offers insight into the potential
benefit of authentication, encryption and techniques that require in-
network devices to interpret specific protocol header fields.
The use of encryption to protect individual privacy may reasonably be
considered a choice that users may make. This comes with
implications that need to be considered:
Troubleshooting and diagnostics. Encrypting all transport information
eliminates the incentive for operators to troubleshoot what they
cannot interpret: one flow experiencing packet loss looks like any
other. When transport header encryption prevents decoding the
transport header (if sequence numbers and flow ID are obscured),
and hence understanding the impact on a particular flow or flows
that share a common network segment. Encrypted traffic therefore
implies "don't touch", and a likely first response will be "can't
help, no trouble found", or the implication that this complexity
comes with an additional operational cost [I-D.mm-wg-effect-
encrypt].
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Open verifyable data The use of transport header encryption may
reduce the range of parties who can capture useful measurement
data. This may restricts the information sources of available to
the Internet community to understand the operation of the network
and transport protocols that use this to inform design decisions
for new protocols, new equipment and operational practice. This
could mean that key information is only available at endpoints:
i.e., at user devices and within service platforms. While these
devices could be designed to offer data about the network paths
that they use, this can not be independently captured - and
therefore a new level of trust is required between these actors
and those that use this data.
Operational practice Published transport specifications can bring
assurance to those operating networks that they have sufficient
understanding to not deploy complex techniques to not routinely
monitor and to not need to routinely manage TCP/IP traffic flows
(e.g. Avoiding the capital and operational costs of deploying
flow rate-limiting and network circuit-breaker methods). This
should continue when encrypted transport headers are used,
providing the traffic produced conforms to the expectations of the
operator. However, operators will need to establish this is the
case.
Traffic analysis The use of encryption makes it harder to determine
which transport methods are being used across a network segment
and the trends in usage. This could impact the ability for an
operator to anticipate the need for network upgrades and roll-out.
It can also impact on-going traffic engineering activities.
Although the impact in many case may be small, there are cases
where operators directly support services (e.g., in radio
environments) and the more complex the underlying infrastructure
the more important this impact.
Interactions between mechanisms Encryption restricts the ability to
explore interactions between functions at different protocol
layers. This is a side-effect of not allowing a choice of the
vantage point from which this information is observed, an
important issue in examining collateral impact of flows sharing a
bottleneck, or where the intention is to understand the
interaction between a layer 2 function (e.g., radio resource
management policy, a channel impairment, an AQM configuration, a
PHB or scheduling method) and a transport protocol. An
appropriate vantage point, coupled with timing information for the
flow (fine-grained timestamps) is a valuable tool in benchmarking
equipment/configurations and understanding non-trivial
interactions.
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Common specifications Since the introduction of congestion control,
TCP has continued to contribute the predominate transport, with a
range but consistent approach to avoiding congestion collapse.
There is also a risk that the diversity of transport mechanisms
could also increase, with incentives to use a wide range of
methods, this is not in itself a problem, nor is this a direct
result of encryption. However, when encryption is used, this risk
needs to be weighed against the reduced visibility to network
operators. Especially, if a development cycle focused on specific
protocols/applications could for instance incentivise
optimisations (e.g., expectations of capacity, expectations of
RTT, loss rate, level of multiplexing, etc) that may prove
suboptimal for users or operators that utilise a network segments
with different characteristics than targeted by the developer.
Encryption places the onus on validation in the hands of
developers. While there is little to doubt that developers will
seek to produce high quality code for their target use, it is not
clear whether there is sufficient incentive to ensure good
practice that benefits the wide diversity of requirements from the
Internet community as a whole.
Restricting research and development The use of encryption may impede
independent research and development initiatives. Experience
shows that high quality transport protocols are complicated to
design and complex to deploy, and that individual mechanisms need
to be evaluated while considering other mechanism, across a broad
range of network topologies and with attention to the impact on
traffic sharing the capacity. This could eliminate the
independent self-checks that have previously been in place from
research and academic contributors (e.g., the role of ICCRG, and
research publications in reviewing new transport mechanisms and
assessing the impact of their experimental deployment).
Pervasive use of transport header encryption can impact the ways that
future protocols are designed and deployed. The choice of whether
candidate transport designs should encrypt their protocol headers
therefore needs to be taken based not just on security
considerations, but also on the impact on operating networks and the
constrictions this may place on evolution of Internet protocols.
While encryption of all 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 open
specified header fields that are observable from in-network devices.
6. Acknowledgements
The author would like to thank all who have talked to him face-to-
face or via email. ...
7. IANA Considerations
XX RFC ED - PLEASE REMOVE THIS SECTION XXX
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This memo includes no request to IANA.
8. Security Considerations
This document is about design and deployment considerations for
transport protocols. Authentication, confidentiality protection, and
integrity protection are identified as Transport Features by
RFC8095". As currently deployed in the Internet, these features are
generally provided by a protocol or layer on top of the transport
protocol; no current full-featured standards-track transport protocol
provides these features on its own. Therefore, these features are
not considered in this document, with the exception of native
authentication capabilities of TCP and SCTP for which the security
considerations in RFC4895.
Like congestion control mechanisms, security mechanisms are difficult
to design and implement correctly. It is hence recommended that
applications employ well-known standard security mechanisms such as
DTLS, TLS or IPsec, rather than inventing their own.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997, <http://www.rfc-editor.org/info/
rfc2119>.
9.2. Informative References
[I-D.dolson-plus-middlebox-benefits]
Dolson, D., Snellman, J., Boucadair, M. and C. Jacquenet,
"Beneficial Functions of Middleboxes", Internet-Draft
draft-dolson-plus-middlebox-benefits-03, March 2017.
[I-D.ietf-aqm-codel]
Nichols, K., Jacobson, V., McGregor, A. and J. Jana,
"Controlled Delay Active Queue Management", Internet-Draft
draft-ietf-aqm-codel-00, October 2014.
[I-D.ietf-aqm-fq-codel]
Hoeiland-Joergensen, T., McKenney, P., Taht, D., Gettys,
J. and E. Dumazet, "FlowQueue-Codel", Internet-Draft
draft-ietf-aqm-fq-codel-00, January 2015.
[I-D.ietf-aqm-pie]
Pan, R., Natarajan, P., Baker, F. and G. White, "PIE: A
Lightweight Control Scheme To Address the Bufferbloat
Problem", Internet-Draft draft-ietf-aqm-pie-00, October
2014.
[I-D.ietf-ippm-6man-pdm-option]
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Elkins, N., Hamilton, R. and m. mackermann@bcbsm.com,
"IPv6 Performance and Diagnostic Metrics (PDM) Destination
Option", Internet-Draft draft-ietf-ippm-6man-pdm-
option-10, May 2017.
[I-D.ietf-quic-transport]
Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
and Secure Transport", Internet-Draft draft-ietf-quic-
transport-03, May 2017.
[I-D.ietf-tcpm-accurate-ecn]
Briscoe, B., Kuehlewind, M. and R. Scheffenegger, "More
Accurate ECN Feedback in TCP", Internet-Draft draft-ietf-
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]
Briscoe, B., Schepper, K. and M. Bagnulo, "Low Latency,
Low Loss, Scalable Throughput (L4S) Internet Service:
Architecture", Internet-Draft draft-ietf-tsvwg-l4s-
arch-00, May 2017.
[I-D.mm-wg-effect-encrypt]
Moriarty, K. and A. Morton, "Effect of Pervasive
Encryption on Operators", Internet-Draft draft-mm-wg-
effect-encrypt-11, April 2017.
[I-D.trammell-plus-abstract-mech]
Trammell, B., "Abstract Mechanisms for a Cooperative Path
Layer under Endpoint Control", Internet-Draft draft-
trammell-plus-abstract-mech-00, September 2016.
[I-D.trammell-plus-statefulness]
Kuehlewind, M., Trammell, B. and J. Hildebrand,
"Transport-Independent Path Layer State Management",
Internet-Draft draft-trammell-plus-statefulness-02,
December 2016.
[Latency] Briscoe, B., "Reducing Internet Latency: A Survey of
Techniques and Their Merits", November 2014.
[Measure] Fairhurst, G., Kuehlewind, M. and D. Lopez, "Measurement-
based Protocol Design", June 2017.
[RFC2474] Nichols, K., Blake, S., Baker, F. and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI
10.17487/RFC2474, December 1998, <http://www.rfc-
editor.org/info/rfc2474>.
Fairhurst Expires November 28, 2017 [Page 26]
Internet-Draft Transport Encryption May 2017
[RFC3135] Border, J., Kojo, M., Griner, J., Montenegro, G. and Z.
Shelby, "Performance Enhancing Proxies Intended to
Mitigate Link-Related Degradations", RFC 3135, DOI
10.17487/RFC3135, June 2001, <http://www.rfc-editor.org/
info/rfc3135>.
[RFC3168] Ramakrishnan, K., Floyd, S. and D. Black, "The Addition of
Explicit Congestion Notification (ECN) to IP", RFC 3168,
DOI 10.17487/RFC3168, September 2001, <http://www.rfc-
editor.org/info/rfc3168>.
[RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and
Issues", RFC 3234, DOI 10.17487/RFC3234, February 2002,
<http://www.rfc-editor.org/info/rfc3234>.
[RFC3449] Balakrishnan, H., Padmanabhan, V., Fairhurst, G. and M.
Sooriyabandara, "TCP Performance Implications of Network
Path Asymmetry", BCP 69, RFC 3449, DOI 10.17487/RFC3449,
December 2002, <http://www.rfc-editor.org/info/rfc3449>.
[RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute
in Session Description Protocol (SDP)", RFC 3605, DOI
10.17487/RFC3605, October 2003, <http://www.rfc-editor.org
/info/rfc3605>.
[RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D.,
Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J. and L.
Wood, "Advice for Internet Subnetwork Designers", BCP 89,
RFC 3819, DOI 10.17487/RFC3819, July 2004, <http://www
.rfc-editor.org/info/rfc3819>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302, DOI
10.17487/RFC4302, December 2005, <http://www.rfc-
editor.org/info/rfc4302>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC
4303, DOI 10.17487/RFC4303, December 2005, <http://www
.rfc-editor.org/info/rfc4303>.
[RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C. and J. Rey,
"Extended RTP Profile for Real-time Transport Control
Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, DOI
10.17487/RFC4585, July 2006, <http://www.rfc-editor.org/
info/rfc4585>.
[RFC4737] Morton, A., Ciavattone, L., Ramachandran, G., Shalunov, S.
and J. Perser, "Packet Reordering Metrics", RFC 4737, DOI
10.17487/RFC4737, November 2006, <http://www.rfc-
editor.org/info/rfc4737>.
Fairhurst Expires November 28, 2017 [Page 27]
Internet-Draft Transport Encryption May 2017
[RFC5236] Jayasumana, A., Piratla, N., Banka, T., Bare, A. and R.
Whitner, "Improved Packet Reordering Metrics", RFC 5236,
DOI 10.17487/RFC5236, June 2008, <http://www.rfc-
editor.org/info/rfc5236>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/
RFC5246, August 2008, <http://www.rfc-editor.org/info/
rfc5246>.
[RFC5559] Eardley, P., Ed., "Pre-Congestion Notification (PCN)
Architecture", RFC 5559, DOI 10.17487/RFC5559, June 2009,
<http://www.rfc-editor.org/info/rfc5559>.
[RFC5925] Touch, J., Mankin, A. and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <http://www.rfc-editor.org/info/rfc5925>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <http://www.rfc-editor.org/info/rfc6347>.
[RFC6437] Amante, S., Carpenter, B., Jiang, S. and J. Rajahalme,
"IPv6 Flow Label Specification", RFC 6437, DOI 10.17487/
RFC6437, November 2011, <http://www.rfc-editor.org/info/
rfc6437>.
[RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.
and K. Carlberg, "Explicit Congestion Notification (ECN)
for RTP over UDP", RFC 6679, DOI 10.17487/RFC6679, August
2012, <http://www.rfc-editor.org/info/rfc6679>.
[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
2014, <http://www.rfc-editor.org/info/rfc7258>.
[RFC7525] Sheffer, Y., Holz, R. and P. Saint-Andre, "Recommendations
for Secure Use of Transport Layer Security (TLS) and
Datagram Transport Layer Security (DTLS)", BCP 195, RFC
7525, DOI 10.17487/RFC7525, May 2015, <http://www.rfc-
editor.org/info/rfc7525>.
[RFC7567] Baker, F.Ed., and G. Fairhurst, Ed., "IETF
Recommendations Regarding Active Queue Management", BCP
197, RFC 7567, DOI 10.17487/RFC7567, July 2015, <http://
www.rfc-editor.org/info/rfc7567>.
[RFC7624] Barnes, R., Schneier, B., Jennings, C., Hardie, T.,
Trammell, B., Huitema, C. and D. Borkmann,
"Confidentiality in the Face of Pervasive Surveillance: A
Threat Model and Problem Statement", RFC 7624, DOI
10.17487/RFC7624, August 2015, <http://www.rfc-editor.org/
info/rfc7624>.
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[RFC7713] Mathis, M. and B. Briscoe, "Congestion Exposure (ConEx)
Concepts, Abstract Mechanism, and Requirements", RFC 7713,
DOI 10.17487/RFC7713, December 2015, <http://www.rfc-
editor.org/info/rfc7713>.
[RFC7928] Kuhn, N., Ed., Natarajan, P., Ed., Khademi, N.Ed., and D.
Ros, "Characterization Guidelines for Active Queue
Management (AQM)", RFC 7928, DOI 10.17487/RFC7928, July
2016, <http://www.rfc-editor.org/info/rfc7928>.
[RFC8084] Fairhurst, G., "Network Transport Circuit Breakers", BCP
208, RFC 8084, DOI 10.17487/RFC8084, March 2017, <http://
www.rfc-editor.org/info/rfc8084>.
[RFC8085] Eggert, L., Fairhurst, G. and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <http://www.rfc-editor.org/info/rfc8085>.
[RFC8086] Yong, L., Ed., Crabbe, E., Xu, X. and T. Herbert, "GRE-in-
UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086, March
2017, <http://www.rfc-editor.org/info/rfc8086>.
[RFC8087] Fairhurst, G. and M. Welzl, "The Benefits of Using
Explicit Congestion Notification (ECN)", RFC 8087, DOI
10.17487/RFC8087, March 2017, <http://www.rfc-editor.org/
info/rfc8087>.
[Tor] The Tor Project, ., "https://www.torproject.org", June
2017.
Appendix A. Revision information
-00 This is an individual draft for the IETF community
Author's Address
Godred Fairhurst
University of Aberdeen
Department of Engineering
Fraser Noble Building
Aberdeen, AB24 3UE
Scotland
Email: gorry@erg.abdn.ac.uk
URI: http://www.erg.abdn.ac.uk/
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