Internet DRAFT - draft-kuhn-tsvwg-careful-resume
draft-kuhn-tsvwg-careful-resume
Internet Engineering Task Force N. Kuhn
Internet-Draft Thales Alenia Space
Intended status: Informational E. Stephan
Expires: 4 September 2023 Orange
G. Fairhurst
University of Aberdeen
C. Huitema
Private Octopus Inc.
3 March 2023
Careful convergence of congestion control from retained state with QUIC
draft-kuhn-tsvwg-careful-resume-00
Abstract
This document discusses careful convergence of Congestion Control
(CC) in QUIC, providing a cautious method that enables fast startup
in a wide range of connections : reconnections using previous
transport security credentials (0-RTT context), reconnections between
2 peers (prior knowledge of transport context), application-limited
traffic.
The method provides QUIC with transport services that resemble those
currently available in TCP, such as TCP Control Block (TCB) [RFC9040]
caching or updates to support application-limited traffic.
The method reuses a set of computed CC parameters that are based on
the previously observed path characteristics between the the same
pair of transport endpoints, such as the bottleneck bandwidth,
available capacity, or the RTT. These parameters are stored,
allowing then to be later used to modify the CC behavior of a
subsequent connection. The document also discusses assumptions and
defines requirements around how a sender utilizes these parameters to
provide opportunities for a new connection to more quickly get up to
speed (i.e. utilize the available capacity). It discusses how these
changes impact the capacity at a shared network bottleneck and the
safe response that is needed after any indication that the new rate
is inappropriate.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Copyright Notice
Copyright (c) 2023 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
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Using the Information with Care . . . . . . . . . . . . . 4
1.2. Receiver Preference . . . . . . . . . . . . . . . . . . . 4
1.3. Examples of Scenarios of Interest . . . . . . . . . . . . 4
1.3.1. A Satellite Access Network Example . . . . . . . . . 5
1.3.2. Another Network Example . . . . . . . . . . . . . . . 6
2. Language, notations and terms . . . . . . . . . . . . . . . . 6
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 6
2.2. Use of CC Information collected by the Sender . . . . . . 6
2.3. Notations and Terms . . . . . . . . . . . . . . . . . . . 6
3. The Phases of CC using Careful Resume . . . . . . . . . . . . 7
4. Congestion Control Guidelines and Requirements . . . . . . . 9
4.1. Determing the current Path Capacity in the Observe
Phase . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.2. Confirming the Path in the Reconnaissance Phase . . . . . 9
4.3. Confirming the Path . . . . . . . . . . . . . . . . . . . 9
4.4. Safety Requirements for the Unvalidated Phase . . . . . . 10
4.4.1. Variable Network Conditions - Choosing Careful
Resume . . . . . . . . . . . . . . . . . . . . . . . 11
4.4.2. Pacing in Careful Resume . . . . . . . . . . . . . . 12
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4.5. Safety Requirements for the Retreat Phase . . . . . . . . 12
4.5.1. Variable Network Conditions - Mitigating Mistakes . . 13
4.6. Returning to Normal Congestion Control . . . . . . . . . 13
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 14
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Annexe: An Endpoint Token . . . . . . . . . . . . . 16
A.1. Creating an Endpoint Token . . . . . . . . . . . . . . . 16
Appendix B. Summary . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction
All Internet transports are required to either use a CC method, or to
constrain there rate of transmission [RFC8085]. In 2010, a survey of
alternative CC methods [RFC5783], noted that there are challenges
when a CC operates across an Internet path with a high and/or
variable bandwidth-delay product (BDP).
A CC method typically takes time to ramp-up the packet rate, called
the "slow-start phase", informally known as the time to "Get up to
speed". This slow start phase is a period in which a sender
intentionally uses less capacity than might be available, with the
intention to avoid or limit overshooting the actual capacity at a
bottleneck. This can result in increased queuing (latency/jitter)
and/or congestion packet loss to the flow. Any overshoot in the
capacity can also have a detrimental effect on other flows sharing a
common bottleneck. In the extreme case, persistent congestion could
result in unwanted starvation of other flows [RFC8867] (i.e.,
Preventing other flows from successfully sharing a common
bottleneck).
This document specifies a method that can improve performance by
reducing the time to get up to speed, and hence can reduce the total
duration of a transfer. It introduces an alternative method to
select initial CC parameters, including a way to more rapidly and
safely grow the congestion window (cwnd). This method is based on
temporal sharing (sometimes known as caching) of a set of computed CC
parameters that relate to a previously observed path, such as the
bottleneck bandwidth, available capacity, and RTT. These parameters
are stored and used to modify the CC behaviour of a subsequent
connection between the same local and remote endpoints.
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1.1. Using the Information with Care
Care is needed in the use of any temporal information to assure safe
use of the Internet and to be robust to changes in traffic patterns,
network routing and link/node failures. There are also cases where
using the parameters of a previous connection are not appropriate,
and a need to evaluate the potential for malicious use of the method.
The specification for the QUIC transport protocol [RFC9000] therefore
notes "Generally, implementations are advised to be cautious when
using previous values on a new path."
1.2. Receiver Preference
Whilst a sender could take optimization decisions without considering
the receiver's preference, there are cases where a client at the
receiver could have information that is not available at the sender.
In these cases, a client could could explicitely ask for tuning the
slow start when the application continues transmission, or to to
inhibit tuning. Examples where this could have benfit include:
1. when a receiver understands that the pattern of traffic that a
connection will use (e.g., the volume of data to be sent, the
length of the session, or the maximum transfer rate required);
2. when a receiver has a local indication that the path/local
interface has changed since CC parameters were stored;
3. when there is information related to the current hardware
limitations at the receiver;
4. where the receiver understands the capacity that will be needed
for other concurrent flows that might be expected to share the
capacity of the path.
A related document complements this CC method by allowing the sender-
generated transport information to be stored at the receiver
[I-D.kuhn-quic-bdpframe-extension]. This enables a receiver to
implement a policy that informs a sender whether the receiver desires
the sender to reuse the CC parameters. By transfering the
information to a receiver, it also releases the sender from needing
to retain CC parameter state for each receiver.
1.3. Examples of Scenarios of Interest
This secion provides a set of examples where the method is expected
to improve performance.
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QUIC introduces the concept of transport parameters (Section 4 of
[RFC9000]). The present document adds to this by noting that a new
connection can utilize a set of key transport parameters from a
previous connection to reduce the completion time for a transfer.
This is expected to have benefit when the transfer is significantly
larger than the IW, and the BDP is also significantly more than the
IW. This benefit is particularly evident for a path where the RTT is
much larger than for typical Internet paths.
The method can be used by a sender performing a unidirectional data
transfer towards the receiver, (e.g., a receiver downloading a file
or a web page). This applies to a CC that sends data to a remote
endpoint and that remote endpoint resumes the connection, which is
the focus of the current version of the document.
Both endpoints can assume the role of a sender or a receiver.
Receivers can therefore also perform a bidirectional data transfer,
where both endpoints simulatenously send data to each other (e.g.,
remote execution of an application, or a bidirectional video
conference call).
Examples where temporal sharing of CC parameters can eliminate round-
trip times at the start of a new connection include the following:
1. where an application uses a series of connections over the same
path (each connection which otherwise would need to individually
discover the CC parameters);
2. where an application resumes using capacity after a pause in
transmission (an application that pauses would otherwise need to
discover new CC parameters each time it connects over the same
path);
3. where an application reconnects after a disruption that had
temporarilly reduced the path capacity (e.g., after to a link
propagation impairment, or where a user on a train journey
travels through different areas of connectivity before the
endpoint returns to use a path with the original
characteristics).
1.3.1. A Satellite Access Network Example
In a specific example of high BDP path, a satellite access network,
takes up to 9 seconds to complete a 5.3 MB transfer using standard
CC, whereas using the specified method the transfer time could reduce
to 4 seconds [IJSCN]; and the time to complete a 1 MB transfer could
be reduced by 62 % [MAPRG111]. Benefit is also expected for other
sizes of transfer and for different path characteristics that also
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result in a path with high BDP.
1.3.2. Another Network Example
{XXX-Editor note: A future revision can provide other Path Examples
here.}
2. Language, notations and terms
This section provides a brief summary of key terms and the
requirements language that is used.
2.1. Requirements Language
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2.2. Use of CC Information collected by the Sender
Sender-generated information is used in this document for two
functions:
Information to charactise the saved path, to allow a sender to
establish if the saved information indicates the saved path is
consistent with the current path.
Information about the capacity that was available on a saved path,
to allow a later sender to determine an appropriate set of CC
paramaters for its current path.
2.3. Notations and Terms
The document uses language drawn from a range of IETF RFCs. It
defines current, and saved values for a set of CC parameters:
* current_bb : The current estimated bottleneck bandwidth;
* saved_bb: The estimated bottleneck bandwidth preserved from a
previous connection;
* current_rtt: The current RTT;
* saved_rtt: The measured RTT, preserved from a previous connection;
* endpoint_token: The Endpoint Token of the receiver;
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* current_endpoint_token: The current Endpoint Token of the
receiver;
* saved_endpoint_token: The Endpoint Token of a previous connection
by the receiver;
* remembered BDP parameters: A combination of the saved_rtt and
saved_bb.
The Endpoint Token is described in Appendix A.
3. The Phases of CC using Careful Resume
This section defines a series of phases through that the CC algorithm
moves through as a connection gets up to speed when uit uses the
Careful Resume method.
1. Observe Phase: During a previous connection, information about
the specific path to an endpoint is saved. This is used to
characterise the path and to indicate the capacity that was
available. It includes the current RTT (current_rtt), bottleneck
bandwidth (current_bb) and current receiver Endpoint Token
(current_endpoint_token) are stored as saved_rtt, saved_bb and
saved_endpoint_token.
2. Reconnaissance Phase: When a sender resumes between the same pair
of endpoints, (aka the same path) it enters the Reconnaissance
Phase. The sender only enters this phase when there are saved CC
parameters for the same pair of endpoints and this information is
currnetly valid (i.e., the parameters have not expired.) When a
method is provided (such as the BDP_Frame), a receiver can
request the sender to not enter this phase. The sender is send
iniial data, limited by the Initial Window. This phase checks
whether the current path is consistent with the saved path
information. The sender then measures the path characteristics
of the present path to confirm that the path is consistent with
the previously characterised path (including a similar RTT).
1. If the sender determines that the path RTT or the other saved
path information are not consistent with the current path,
then the sender continues using the standard CC, and enters
the Normal Phase.
2. To ensure a sender avoids resuming under severely congested
conditions, if any sent initial data was not correctly
received, the sender continues using the standard CC, and
enters the Normal Phase.
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3. If the sender confirms both that the saved and current path
information are consistent and that the sent initial data was
correctly received, the sender enters the Unvalidated Phase.
3. Unvalidated Phase: In the Unvalidated Phase, a sender can utilize
the saved path information to update its CC parameters. This
phase a rate higher than allowed by a traditional slow-start
mechanism. The convergence towards the previous rate is expected
to be faster, but should not be instantaneous, to avoid adding
congestion to an already congested bottleneck. In this phase,
the sender continues to check the saved and current path
information are consistent.
1. If a sender determines either that previous parameters are
not valid (due to a detected change in the path) or
congestion was experienced, then the sender needs to enter
the Retreat Phase.
2. If acknowledgments show that the unvalidated rate was
succesfully used without inducing significant congestion to
the path, then the sender is permitted to continue at the
rate used in in the unvalidated phase when it continues in
the Normal Phase.
4. Retreat Phase: In the Retreat Phase, the sender stops using the
saved CC parameters. This phase is designed to mitigate the
impact on other flows that might have been sharing a congested
bottleneck when in the Unvalidated Phase. The sender needs to
re-initialised CC parameters to drain any queue built at the
bottleneck duing the Unvalidated Phase and allow other flows to
then regain their share of the available capacity. This reaction
differs to a traditional CC reaction to congestion, because in
this case the capacity estimate was unvalidated. Saved CC
parameters for this path should be removed, to prevent the
parameters being used again with other flows.
1. The sender then enters the Normal phase with re-initialised
CC parameters.
5. Normal Phase: The sender resumes using the normal CC method.
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4. Congestion Control Guidelines and Requirements
The sender is limited by any rate-limitation of the transport
protocol with which the method is used. For QUIC this includes: flow
control mechanisms or amplification attack prevention. In
particular, a QUIC receiver may need to issue proactive MAX_DATA
frames to increase the flow control limits of a connection that is
started with this method.
4.1. Determing the current Path Capacity in the Observe Phase
Congestion controllers, such as CUBIC or RENO, could estimate the
saved_bb and current_bb values by utilizing a combination of the
cwnd/flight_size and the minimum RTT. A different method could be
used to estimate the same values when using a rate-based congestion
controller, such as BBR [I-D.cardwell-iccrg-bbr-congestion-control].
* (Observe Phase) The sender SHOULD NOT store and/or send CC
parameter information related to an estimated bottleneck bandwidth
(saved_bb) (see Section 2.3 for more details on bottleneck
bandwidth definition), if the cwnd is not at least four times
larger than the IW.
4.2. Confirming the Path in the Reconnaissance Phase
The sender sends the first data limited by the IW - this is assumed a
safe starting point for any path where there is no path information
or congestion control information. This limit avoids adding
excessive congestion to a potentially congested path.
The sender monitors reception of the IW data. If the path
characteristics resemble those of a recent previous connection from
to the same sender (i.e., current_rtt < 1.2*saved_rtt) and all data
was acknowledged without reported congestion, the method permits the
sender to utilize the saved_bb as an input to adapt current_bb to
rapidly determine a new safe rate.
* (Reconnaissance Phase) The sender MUST NOT send more than the IW
in the first RTT of transmitted data [RFC9000].
When used in a controlled network, additional information about local
path characteristics could be known, which might be used to configure
a non-standard IW.
4.3. Confirming the Path
Paths change with respect to time for many reasons. This could
result in previously measured CC parameters becoming irelevant.
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* Endpoint Token change: If the Endpoint Token changes (i.e., the
saved_endpoint_token is different from the
current_endpoint_token), the different Endpoint Token can be
assumed as an indication of a different network path. This new
path does not necessarily exhibit the same characteristics as the
old one.
* RTT change: A significant change in RTT might be an indication
that the network conditions have changed. Since the CC
information is directly impacted by the RTT, a significant change
in the RTT is a strong indication that the previously estimated
BDP parameters are likely to not be valid for the current path.
* Lifetime of the information: The CC information is temporal.
Frequent connections to the same Endpoint Token are likely to
track changes, but long-term use of previous values is not
appropriate.
{NOTE: A future revision of this document needs to specify how long
CC Parameters can be cached, possibly based on TCP-new-CWV or TCB}.
* (Reconnaissance Phase) The sender MUST compare the measured
transport parameters (in particular current_rtt) of the new
session with those of the previous session (in particular
saved_rtt). The method MUST NOT be used when the path fails to be
validated.
{XXX-Editor-note: RTT check should be a range rather than an
inequality (current_rtt < 1.2*saved_rtt).}
4.4. Safety Requirements for the Unvalidated Phase
This section defines the safety requirements for using saved CC
parameters.
{XXX-Editor note: The sender ought not to re-utilize all the capacity
it previously used, to avoid starving other flows that started or
increased their capacity after the last measurement. How strong
should this be stated: ... MUST or SHOULD ... What safety factor is
appropriate for the resuming sender? If using slow-start it would
anyway double the rate on the next RTT, so is capacity/2 appropriate
to initially try?}
The method needs to be designed to avoid sending excessive data into
a congested bottleneck, because this can have a material impact on
any flows sharing that bottleneck, and the ability of those flows to
control their own sending rate.
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* (Unvalidated Phase) A new connection MUST NOT directly use the
previously measured saved_rtt and saved_bb to simply initialize a
new flow to resume sending at the same rate.
4.4.1. Variable Network Conditions - Choosing Careful Resume
The network conditions for the same path can also change over time.
Bottleneck bandwidth and network traffic can change at any time. An
Internet method needs to be robust to network conditions that can
differ from one connection to the next, due to variations in the
forwarding path, reconfiguration of equipment or changes in the link
conditions.
* (Unvalidated Phase) Careful Resume MUST be robust to changes in
network traffic, including the arrival of new traffic flows that
compete for the bottleneck capacity.
* The sender MUST check the validity of any received saved_rtt and
saved_bb parameters, whether these are sent by a receiver or are
stored at the sender. The following events indicates cases where
the use of these parameters is inappropriate:
{NOTE: A later revision needs to define how to decide a significant
change.}
* BB over-estimation: There are cases where using a measured cwnd
would inflate the bottleneck bandwidth. At the end of the CC slow
start phase, the value of cwnd can be significantly larger than
the minimum value needed to utilize the path (i.e., cwnd
overshoot). In most case, the cwnd finally converges to a stable
value after several more RTTs. It would be inappropriate to use
an overshoot in the cwnd as a basis for estimating the bottleneck
bandwidth. NOTE: One mitigation could be to further restrict to
only a fraction (e.g., 1/2) of the previously used cwnd; another
mitigation might be to calculate the bottleneck bandwidth based on
the flight_size or an averaged cwnd.
* Preventing Starvation of New Flows: It would not be appropriate to
fully use a bottleneck bandwidth estimate based on a previous
measurement of capacity, because new flows might have started
using the available capacity since that measurement was made. The
mitigation could be to restrict to only a fraction (e.g., 1/2) of
the previously used cwnd.
These safety guidelines are designed to mitigate the risk that sender
adds excessive congestion to an already congested path. The
following mechanisms help in fulfilling this objective:
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* (Unvalidated phase) The sender MUST NOT use the parameters unless
the first IW packets when packets are detected as lost or
acknowledgments indicate the packets were ECN CE-marked. These
are indication of potential congestion and therefore the method
MUST NOT be used;
* (Unvalidated phase) The sender MUST implement the retreat method
when packets are detected as lost or acknowledgments indicate the
packets were ECN CE-marked. These are indication of potential
congestion and therefore the method MUST NOT be used.
{XXX-Editor note: Decide on the mitigation for Starvation of New
Flows.}
4.4.2. Pacing in Careful Resume
The following mechanisms could be implemented.
The sender needs to avoid sending a burst of packets as a result of a
step-increase in the congestion window [RFC9000]. Pacing the packets
as a function of the current_rtt can provide this additional safety
during the unvalidated period.
Identify a relevant pacing rhythm:
* The sender estimates a pacing rhythm using saved_rtt and saved_bb.
The Inter-packet Transmission Time (ITT) is determined from the
ratio between the current Maximum Message Size (MMS) and the ratio
between the saved_bb and saved_rtt. A tunable safety margin can
avoid sending more than a recommended maximum IW (recom_iw):
- current_iw = min(recom_iw,saved_bb)
- ITT = MSS/(current_iw/saved_rtt)
* A successful receipt of the IW data confirms the path can be used
with the method specified in this document.
This follows the idea presented in [RFC4782],
[I-D.irtf-iccrg-sallantin-initial-spreading] and [CONEXT15].
4.5. Safety Requirements for the Retreat Phase
This section defines the safety requirements after a path change or
congestion is detected in the Unvalidated Phase.
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After transport parameters are set to a previously estimated
bottleneck bandwidth, if the slow-start mechanisms continue with
parameters set by Carfeul Resume, the sender might then overshoot the
bottleneck capacity. This can occur even when using the safety check
described in this section.
4.5.1. Variable Network Conditions - Mitigating Mistakes
The impact of a mistaken decision to use Careful Resume can be
mitigated by 2 potential solutions:
* When resuming, restore the current_bb and current_rtt from the
saved_bb and saved_rtt CC parameters estimated from a previous
connection.
* When resuming, implement a safety check to measure and avoid using
the saved_bb and saved_rtt CC parameters to cause congestion over
the path. In this case, the current_bb and current_rtt might not
be set directly from the saved_bb and saved_rtt: the sender might
wait for the completion of the safety check before this is done.
{XXX-Editor note: Decide on the mitigation after detected
congestion.}
4.6. Returning to Normal Congestion Control
At the end of Carfeul Resume, the CC controller returns to the Normal
Phase.
* For NewReno and CUBIC, it is recommended to exit slow-start and
enter the congestion avoidance phase.
* For BBR CC, it is recommended to enter the "probe bandwidth"
state.
5. Acknowledgments
The authors would like to thank John Border, Gabriel Montenegro,
Patrick McManus, Ian Swett, Igor Lubashev, Robin Marx, Roland Bless
and Franklin Simo for their fruitful comments on earlier versions of
this document.
The authors would like to particularly thank Tom Jones for co-
authoring previous versions of this document.
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6. IANA Considerations
{XXX-Editor note: Text is required to register any IANA
Considerations.
7. Security Considerations
This document does not exhibit specific security considerations since
only sender level considerations are proposed. Security
considerations for the interactions with the receiver are discussed
in [I-D.kuhn-quic-bdpframe-extension].
8. References
8.1. 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,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4782] Floyd, S., Allman, M., Jain, A., and P. Sarolahti, "Quick-
Start for TCP and IP", RFC 4782, DOI 10.17487/RFC4782,
January 2007, <https://www.rfc-editor.org/info/rfc4782>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8801] Pfister, P., Vyncke, É., Pauly, T., Schinazi, D., and W.
Shao, "Discovering Provisioning Domain Names and Data",
RFC 8801, DOI 10.17487/RFC8801, July 2020,
<https://www.rfc-editor.org/info/rfc8801>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>.
[RFC9040] Touch, J., Welzl, M., and S. Islam, "TCP Control Block
Interdependence", RFC 9040, DOI 10.17487/RFC9040, July
2021, <https://www.rfc-editor.org/info/rfc9040>.
8.2. Informative References
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[CONEXT15] Li, Q., Dong, M., and P B. Godfrey, "Halfback: Running
Short Flows Quickly and Safely", ACM CoNEXT , 2015.
[I-D.cardwell-iccrg-bbr-congestion-control]
Cardwell, N., Cheng, Y., Yeganeh, S. H., Swett, I., and V.
Jacobson, "BBR Congestion Control", Work in Progress,
Internet-Draft, draft-cardwell-iccrg-bbr-congestion-
control-02, 7 March 2022,
<https://datatracker.ietf.org/doc/html/draft-cardwell-
iccrg-bbr-congestion-control-02>.
[I-D.irtf-iccrg-sallantin-initial-spreading]
Sallantin, R., Baudoin, C., Arnal, F., Dubois, E., Chaput,
E., and A. Beylot, "Safe increase of the TCP's Initial
Window Using Initial Spreading", Work in Progress,
Internet-Draft, draft-irtf-iccrg-sallantin-initial-
spreading-00, 15 January 2014,
<https://datatracker.ietf.org/doc/html/draft-irtf-iccrg-
sallantin-initial-spreading-00>.
[I-D.kuhn-quic-bdpframe-extension]
Kuhn, N., Emile, S., Fairhurst, G., Jones, T., and C.
Huitema, "BDP Frame Extension", Work in Progress,
Internet-Draft, draft-kuhn-quic-bdpframe-extension-00, 6
March 2022, <https://datatracker.ietf.org/doc/html/draft-
kuhn-quic-bdpframe-extension-00>.
[IJSCN] Thomas, L., Dubois, E., Kuhn, N., and E. Lochin, "Google
QUIC performance over a public SATCOM access",
International Journal of Satellite Communications and
Networking 10.1002/sat.1301, 2019.
[MAPRG111] Kuhn, N., Stephan, E., Fairhurst, G., Jones, T., and C.
Huitema, "Feedback from using QUIC's 0-RTT-BDP extension
over SATCOM public access", IETF 111 - MAPRG meeting ,
2022.
[RFC5783] Welzl, M. and W. Eddy, "Congestion Control in the RFC
Series", RFC 5783, DOI 10.17487/RFC5783, February 2010,
<https://www.rfc-editor.org/info/rfc5783>.
[RFC8867] Sarker, Z., Singh, V., Zhu, X., and M. Ramalho, "Test
Cases for Evaluating Congestion Control for Interactive
Real-Time Media", RFC 8867, DOI 10.17487/RFC8867, January
2021, <https://www.rfc-editor.org/info/rfc8867>.
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Appendix A. Annexe: An Endpoint Token
This proposes an Endpoint Token to allow a sender to identify its own
view of the network path that it is using. In
[I-D.kuhn-quic-bdpframe-extension] this Endpoint Tokencould be shared
and used as an opaque path identifier to other parties and the sender
can verify if this is one of its current paths.
A.1. Creating an Endpoint Token
When computing the Endpoint Token, the sender includes information to
identify the path on which it sends, for example:
* it must include a unique identifier for itself (e.g., a globally
assigned address/prefix; or randomly chosen value).
* it must include an identifier for the destination (e.g., a
destination IP address or name).
* it should an interface identifier (e.g., an index value or a MAC
address to associate the endpoint with the interface on which the
path starts);
* it could include other information such as the DSCP, ports, flow
label, etc (recognising that this additional infromation might
improve the path differentiation, but that this can can reduce the
re-usability of the token);
* it could include any other information the sender chooses to
include, and potentially including PvD information [RFC8801] or
information relating to its public-facing IP address;
* it could include a nonce;
* it could include a time-dependent value to define the validity
period of the token.
When creating an Endpoint Token, the sender has to ensure the
following:
1. To reduce the likelihood of misuse of the Endpoint Token, the
value should be encoded in a way that hides the component
information from the recipient and any eavesdropper on the path.
2. The sender can recalculate the Endpoint Token if it needs to
validate a previously issued token; and that the Endpoint Token
itself can be included in the computed integrity check for any
path information it provides.
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3. The Endpoint Token is designed so that if shared it prevents
another party from deriving private data from the token, or to
use the token to perform unwanted likability with other
information. This implies that the Endpoint Token MUST
necessarily be different when used to identify different
interfaces.
Appendix B. Summary
+---------+-----------+----------------+---------------+-----------+
|Rationale| Solution | Advantage | Drawback | Comment |
+---------+-----------+----------------+---------------+-----------+
|#1 |#1 | | | |
|Variable |set |Ingress optim. |Risk of adding |MUST NOT |
|Network |current_* | | congestion |implement |
| |to saved_* | | | |
| +-----------+----------------+---------------+-----------+
| |#2 | | | |
| |Implement |Reduce risk of |Negative impact|MUST |
| |safety | adding | on ingress |implement |
| |check | congestion | optim. |Section 3 |
+---------+-----------+----------------+---------------+-----------+
Figure 1: Comparing Careful Resume solutions
Authors' Addresses
Nicolas Kuhn
Thales Alenia Space
Email: nicolas.kuhn.ietf@gmail.com
Emile Stephan
Orange
Email: emile.stephan@orange.com
Godred Fairhurst
University of Aberdeen
Department of Engineering
Fraser Noble Building
Aberdeen
Email: gorry@erg.abdn.ac.uk
Christian Huitema
Private Octopus Inc.
Email: huitema@huitema.net
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