draft-ietf-quic-recovery-30.txt   draft-ietf-quic-recovery-31.txt 
QUIC J. Iyengar, Ed. QUIC J. Iyengar, Ed.
Internet-Draft Fastly Internet-Draft Fastly
Intended status: Standards Track I. Swett, Ed. Intended status: Standards Track I. Swett, Ed.
Expires: March 14, 2021 Google Expires: 29 March 2021 Google
September 10, 2020 25 September 2020
QUIC Loss Detection and Congestion Control QUIC Loss Detection and Congestion Control
draft-ietf-quic-recovery-30 draft-ietf-quic-recovery-31
Abstract Abstract
This document describes loss detection and congestion control This document describes loss detection and congestion control
mechanisms for QUIC. mechanisms for QUIC.
Note to Readers Note to Readers
Discussion of this draft takes place on the QUIC working group Discussion of this draft takes place on the QUIC working group
mailing list (quic@ietf.org (mailto:quic@ietf.org)), which is mailing list (quic@ietf.org (mailto:quic@ietf.org)), which is
skipping to change at page 1, line 43 skipping to change at page 1, line 43
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 14, 2021. This Internet-Draft will expire on 29 March 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
skipping to change at page 3, line 40 skipping to change at page 3, line 40
B.1. Constants of interest . . . . . . . . . . . . . . . . . . 39 B.1. Constants of interest . . . . . . . . . . . . . . . . . . 39
B.2. Variables of interest . . . . . . . . . . . . . . . . . . 40 B.2. Variables of interest . . . . . . . . . . . . . . . . . . 40
B.3. Initialization . . . . . . . . . . . . . . . . . . . . . 40 B.3. Initialization . . . . . . . . . . . . . . . . . . . . . 40
B.4. On Packet Sent . . . . . . . . . . . . . . . . . . . . . 41 B.4. On Packet Sent . . . . . . . . . . . . . . . . . . . . . 41
B.5. On Packet Acknowledgement . . . . . . . . . . . . . . . . 41 B.5. On Packet Acknowledgement . . . . . . . . . . . . . . . . 41
B.6. On New Congestion Event . . . . . . . . . . . . . . . . . 42 B.6. On New Congestion Event . . . . . . . . . . . . . . . . . 42
B.7. Process ECN Information . . . . . . . . . . . . . . . . . 43 B.7. Process ECN Information . . . . . . . . . . . . . . . . . 43
B.8. On Packets Lost . . . . . . . . . . . . . . . . . . . . . 43 B.8. On Packets Lost . . . . . . . . . . . . . . . . . . . . . 43
B.9. Upon dropping Initial or Handshake keys . . . . . . . . . 43 B.9. Upon dropping Initial or Handshake keys . . . . . . . . . 43
Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 44 Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 44
C.1. Since draft-ietf-quic-recovery-29 . . . . . . . . . . . . 44 C.1. Since draft-ietf-quic-recovery-30 . . . . . . . . . . . . 44
C.2. Since draft-ietf-quic-recovery-28 . . . . . . . . . . . . 44 C.2. Since draft-ietf-quic-recovery-29 . . . . . . . . . . . . 44
C.3. Since draft-ietf-quic-recovery-27 . . . . . . . . . . . . 44 C.3. Since draft-ietf-quic-recovery-28 . . . . . . . . . . . . 44
C.4. Since draft-ietf-quic-recovery-26 . . . . . . . . . . . . 45 C.4. Since draft-ietf-quic-recovery-27 . . . . . . . . . . . . 45
C.5. Since draft-ietf-quic-recovery-25 . . . . . . . . . . . . 45 C.5. Since draft-ietf-quic-recovery-26 . . . . . . . . . . . . 45
C.6. Since draft-ietf-quic-recovery-24 . . . . . . . . . . . . 45 C.6. Since draft-ietf-quic-recovery-25 . . . . . . . . . . . . 45
C.7. Since draft-ietf-quic-recovery-23 . . . . . . . . . . . . 45 C.7. Since draft-ietf-quic-recovery-24 . . . . . . . . . . . . 45
C.8. Since draft-ietf-quic-recovery-22 . . . . . . . . . . . . 46 C.8. Since draft-ietf-quic-recovery-23 . . . . . . . . . . . . 45
C.9. Since draft-ietf-quic-recovery-21 . . . . . . . . . . . . 46 C.9. Since draft-ietf-quic-recovery-22 . . . . . . . . . . . . 46
C.10. Since draft-ietf-quic-recovery-20 . . . . . . . . . . . . 46 C.10. Since draft-ietf-quic-recovery-21 . . . . . . . . . . . . 46
C.11. Since draft-ietf-quic-recovery-19 . . . . . . . . . . . . 46 C.11. Since draft-ietf-quic-recovery-20 . . . . . . . . . . . . 46
C.12. Since draft-ietf-quic-recovery-18 . . . . . . . . . . . . 46 C.12. Since draft-ietf-quic-recovery-19 . . . . . . . . . . . . 46
C.13. Since draft-ietf-quic-recovery-17 . . . . . . . . . . . . 47 C.13. Since draft-ietf-quic-recovery-18 . . . . . . . . . . . . 47
C.14. Since draft-ietf-quic-recovery-16 . . . . . . . . . . . . 47 C.14. Since draft-ietf-quic-recovery-17 . . . . . . . . . . . . 47
C.15. Since draft-ietf-quic-recovery-14 . . . . . . . . . . . . 48 C.15. Since draft-ietf-quic-recovery-16 . . . . . . . . . . . . 47
C.16. Since draft-ietf-quic-recovery-13 . . . . . . . . . . . . 48 C.16. Since draft-ietf-quic-recovery-14 . . . . . . . . . . . . 48
C.17. Since draft-ietf-quic-recovery-12 . . . . . . . . . . . . 48 C.17. Since draft-ietf-quic-recovery-13 . . . . . . . . . . . . 48
C.18. Since draft-ietf-quic-recovery-11 . . . . . . . . . . . . 49 C.18. Since draft-ietf-quic-recovery-12 . . . . . . . . . . . . 48
C.19. Since draft-ietf-quic-recovery-10 . . . . . . . . . . . . 49 C.19. Since draft-ietf-quic-recovery-11 . . . . . . . . . . . . 49
C.20. Since draft-ietf-quic-recovery-09 . . . . . . . . . . . . 49 C.20. Since draft-ietf-quic-recovery-10 . . . . . . . . . . . . 49
C.21. Since draft-ietf-quic-recovery-08 . . . . . . . . . . . . 49 C.21. Since draft-ietf-quic-recovery-09 . . . . . . . . . . . . 49
C.22. Since draft-ietf-quic-recovery-07 . . . . . . . . . . . . 49 C.22. Since draft-ietf-quic-recovery-08 . . . . . . . . . . . . 49
C.23. Since draft-ietf-quic-recovery-06 . . . . . . . . . . . . 49 C.23. Since draft-ietf-quic-recovery-07 . . . . . . . . . . . . 49
C.24. Since draft-ietf-quic-recovery-05 . . . . . . . . . . . . 49 C.24. Since draft-ietf-quic-recovery-06 . . . . . . . . . . . . 49
C.25. Since draft-ietf-quic-recovery-04 . . . . . . . . . . . . 50 C.25. Since draft-ietf-quic-recovery-05 . . . . . . . . . . . . 49
C.26. Since draft-ietf-quic-recovery-03 . . . . . . . . . . . . 50 C.26. Since draft-ietf-quic-recovery-04 . . . . . . . . . . . . 50
C.27. Since draft-ietf-quic-recovery-02 . . . . . . . . . . . . 50 C.27. Since draft-ietf-quic-recovery-03 . . . . . . . . . . . . 50
C.28. Since draft-ietf-quic-recovery-01 . . . . . . . . . . . . 50 C.28. Since draft-ietf-quic-recovery-02 . . . . . . . . . . . . 50
C.29. Since draft-ietf-quic-recovery-00 . . . . . . . . . . . . 50 C.29. Since draft-ietf-quic-recovery-01 . . . . . . . . . . . . 50
C.30. Since draft-iyengar-quic-loss-recovery-01 . . . . . . . . 50 C.30. Since draft-ietf-quic-recovery-00 . . . . . . . . . . . . 50
C.31. Since draft-iyengar-quic-loss-recovery-01 . . . . . . . . 50
Appendix D. Contributors . . . . . . . . . . . . . . . . . . . . 51 Appendix D. Contributors . . . . . . . . . . . . . . . . . . . . 51
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 51 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 51
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51
1. Introduction 1. Introduction
QUIC is a new multiplexed and secure transport protocol atop UDP, QUIC is a new multiplexed and secure transport protocol atop UDP,
specified in [QUIC-TRANSPORT]. This document describes congestion specified in [QUIC-TRANSPORT]. This document describes congestion
control and loss recovery for QUIC. Mechanisms described in this control and loss recovery for QUIC. Mechanisms described in this
document follow the spirit of existing TCP congestion control and document follow the spirit of existing TCP congestion control and
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The RECOMMENDED initial value for the packet reordering threshold The RECOMMENDED initial value for the packet reordering threshold
(kPacketThreshold) is 3, based on best practices for TCP loss (kPacketThreshold) is 3, based on best practices for TCP loss
detection ([RFC5681], [RFC6675]). In order to remain similar to TCP, detection ([RFC5681], [RFC6675]). In order to remain similar to TCP,
implementations SHOULD NOT use a packet threshold less than 3; see implementations SHOULD NOT use a packet threshold less than 3; see
[RFC5681]. [RFC5681].
Some networks may exhibit higher degrees of packet reordering, Some networks may exhibit higher degrees of packet reordering,
causing a sender to detect spurious losses. Additionally, packet causing a sender to detect spurious losses. Additionally, packet
reordering could be more common with QUIC than TCP, because network reordering could be more common with QUIC than TCP, because network
elements that could observe and reorder out-of-order TCP packets elements that could observe and reorder TCP packets cannot do that
cannot do that for QUIC, because packet numbers are encrypted. for QUIC, because QUIC packet numbers are encrypted. Algorithms that
Algorithms that increase the reordering threshold after spuriously increase the reordering threshold after spuriously detecting losses,
detecting losses, such as RACK [RACK], have proven to be useful in such as RACK [RACK], have proven to be useful in TCP and are expected
TCP and are expected to be at least as useful in QUIC. to be at least as useful in QUIC.
6.1.2. Time Threshold 6.1.2. Time Threshold
Once a later packet within the same packet number space has been Once a later packet within the same packet number space has been
acknowledged, an endpoint SHOULD declare an earlier packet lost if it acknowledged, an endpoint SHOULD declare an earlier packet lost if it
was sent a threshold amount of time in the past. To avoid declaring was sent a threshold amount of time in the past. To avoid declaring
packets as lost too early, this time threshold MUST be set to at packets as lost too early, this time threshold MUST be set to at
least the local timer granularity, as indicated by the kGranularity least the local timer granularity, as indicated by the kGranularity
constant. The time threshold is: constant. The time threshold is:
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path; path;
* the latest RTT sample is higher than the smoothed RTT, perhaps due * the latest RTT sample is higher than the smoothed RTT, perhaps due
to a sustained increase in the actual RTT, but the smoothed RTT to a sustained increase in the actual RTT, but the smoothed RTT
has not yet caught up. has not yet caught up.
The RECOMMENDED time threshold (kTimeThreshold), expressed as a The RECOMMENDED time threshold (kTimeThreshold), expressed as a
round-trip time multiplier, is 9/8. The RECOMMENDED value of the round-trip time multiplier, is 9/8. The RECOMMENDED value of the
timer granularity (kGranularity) is 1ms. timer granularity (kGranularity) is 1ms.
Note: TCP's RACK ([RACK]) specifies a slightly larger threshold,
equivalent to 5/4, for a similar purpose. Experience with QUIC
shows that 9/8 works well.
Implementations MAY experiment with absolute thresholds, thresholds Implementations MAY experiment with absolute thresholds, thresholds
from previous connections, adaptive thresholds, or including RTT from previous connections, adaptive thresholds, or including RTT
variation. Smaller thresholds reduce reordering resilience and variation. Smaller thresholds reduce reordering resilience and
increase spurious retransmissions, and larger thresholds increase increase spurious retransmissions, and larger thresholds increase
loss detection delay. loss detection delay.
6.2. Probe Timeout 6.2. Probe Timeout
A Probe Timeout (PTO) triggers sending one or two probe datagrams A Probe Timeout (PTO) triggers sending one or two probe datagrams
when ack-eliciting packets are not acknowledged within the expected when ack-eliciting packets are not acknowledged within the expected
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This exponential reduction in the sender's rate is important because This exponential reduction in the sender's rate is important because
consecutive PTOs might be caused by loss of packets or consecutive PTOs might be caused by loss of packets or
acknowledgements due to severe congestion. Even when there are ack- acknowledgements due to severe congestion. Even when there are ack-
eliciting packets in-flight in multiple packet number spaces, the eliciting packets in-flight in multiple packet number spaces, the
exponential increase in probe timeout occurs across all spaces to exponential increase in probe timeout occurs across all spaces to
prevent excess load on the network. For example, a timeout in the prevent excess load on the network. For example, a timeout in the
Initial packet number space doubles the length of the timeout in the Initial packet number space doubles the length of the timeout in the
Handshake packet number space. Handshake packet number space.
The time length of a connection that is experiencing consecutive PTOs The total length of time over which consecutive PTOs expire is
is limited by the endpoint's idle timeout. limited by the idle timeout.
The probe timer MUST NOT be set if the time threshold (Section 6.1.2) The probe timer MUST NOT be set if the time threshold (Section 6.1.2)
loss detection timer is set. The time threshold loss detection timer loss detection timer is set. The time threshold loss detection timer
is expected to both expire earlier than the PTO and be less likely to is expected to both expire earlier than the PTO and be less likely to
spuriously retransmit data. spuriously retransmit data.
6.2.2. Handshakes and New Paths 6.2.2. Handshakes and New Paths
Resumed connections over the same network MAY use the previous Resumed connections over the same network MAY use the previous
connection's final smoothed RTT value as the resumed connection's connection's final smoothed RTT value as the resumed connection's
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Since the server could be blocked until more datagrams are received Since the server could be blocked until more datagrams are received
from the client, it is the client's responsibility to send packets to from the client, it is the client's responsibility to send packets to
unblock the server until it is certain that the server has finished unblock the server until it is certain that the server has finished
its address validation (see Section 8 of [QUIC-TRANSPORT]). That is, its address validation (see Section 8 of [QUIC-TRANSPORT]). That is,
the client MUST set the probe timer if the client has not received an the client MUST set the probe timer if the client has not received an
acknowledgement for one of its Handshake packets and the handshake is acknowledgement for one of its Handshake packets and the handshake is
not confirmed (see Section 4.1.2 of [QUIC-TLS]), even if there are no not confirmed (see Section 4.1.2 of [QUIC-TLS]), even if there are no
packets in flight. When the PTO fires, the client MUST send a packets in flight. When the PTO fires, the client MUST send a
Handshake packet if it has Handshake keys, otherwise it MUST send an Handshake packet if it has Handshake keys, otherwise it MUST send an
Initial packet in a UDP datagram of at least 1200 bytes. Initial packet in a UDP datagram with a payload of at least 1200
bytes.
6.2.3. Speeding Up Handshake Completion 6.2.3. Speeding Up Handshake Completion
When a server receives an Initial packet containing duplicate CRYPTO When a server receives an Initial packet containing duplicate CRYPTO
data, it can assume the client did not receive all of the server's data, it can assume the client did not receive all of the server's
CRYPTO data sent in Initial packets, or the client's estimated RTT is CRYPTO data sent in Initial packets, or the client's estimated RTT is
too small. When a client receives Handshake or 1-RTT packets prior too small. When a client receives Handshake or 1-RTT packets prior
to obtaining Handshake keys, it may assume some or all of the to obtaining Handshake keys, it may assume some or all of the
server's Initial packets were lost. server's Initial packets were lost.
To speed up handshake completion under these conditions, an endpoint To speed up handshake completion under these conditions, an endpoint
MAY send a packet containing unacknowledged CRYPTO data earlier than MAY send a packet containing unacknowledged CRYPTO data earlier than
the PTO expiry, subject to the address validation limits in the PTO expiry, subject to the address validation limits in
Section 8.1 of [QUIC-TRANSPORT]. Section 8.1 of [QUIC-TRANSPORT].
Endpoints can also use coalesced packets to ensure that each datagram Endpoints can also use coalesced packets (see Section 12.2 of
elicits at least one acknowledgement. For example, a client can [QUIC-TRANSPORT]) to ensure that each datagram elicits at least one
coalesce an Initial packet containing PING and PADDING frames with a acknowledgement. For example, a client can coalesce an Initial
0-RTT data packet and a server can coalesce an Initial packet packet containing PING and PADDING frames with a 0-RTT data packet
containing a PING frame with one or more packets in its first flight. and a server can coalesce an Initial packet containing a PING frame
with one or more packets in its first flight.
6.2.4. Sending Probe Packets 6.2.4. Sending Probe Packets
When a PTO timer expires, a sender MUST send at least one ack- When a PTO timer expires, a sender MUST send at least one ack-
eliciting packet in the packet number space as a probe. An endpoint eliciting packet in the packet number space as a probe. An endpoint
MAY send up to two full-sized datagrams containing ack-eliciting MAY send up to two full-sized datagrams containing ack-eliciting
packets, to avoid an expensive consecutive PTO expiration due to a packets, to avoid an expensive consecutive PTO expiration due to a
single lost datagram or transmit data from multiple packet number single lost datagram or transmit data from multiple packet number
spaces. All probe packets sent on a PTO MUST be ack-eliciting. spaces. All probe packets sent on a PTO MUST be ack-eliciting.
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The algorithm in this document specifies and uses the controller's The algorithm in this document specifies and uses the controller's
congestion window in bytes. congestion window in bytes.
An endpoint MUST NOT send a packet if it would cause bytes_in_flight An endpoint MUST NOT send a packet if it would cause bytes_in_flight
(see Appendix B.2) to be larger than the congestion window, unless (see Appendix B.2) to be larger than the congestion window, unless
the packet is sent on a PTO timer expiration (see Section 6.2) or the packet is sent on a PTO timer expiration (see Section 6.2) or
when entering recovery (see Section 7.3.2). when entering recovery (see Section 7.3.2).
7.1. Explicit Congestion Notification 7.1. Explicit Congestion Notification
If a path has been verified to support ECN ([RFC3168], [RFC8311]), If a path has been validated to support ECN ([RFC3168], [RFC8311]),
QUIC treats a Congestion Experienced (CE) codepoint in the IP header QUIC treats a Congestion Experienced (CE) codepoint in the IP header
as a signal of congestion. This document specifies an endpoint's as a signal of congestion. This document specifies an endpoint's
response when its peer receives packets with the ECN-CE codepoint. response when its peer receives packets with the ECN-CE codepoint.
7.2. Initial and Minimum Congestion Window 7.2. Initial and Minimum Congestion Window
QUIC begins every connection in slow start with the congestion window QUIC begins every connection in slow start with the congestion window
set to an initial value. Endpoints SHOULD use an initial congestion set to an initial value. Endpoints SHOULD use an initial congestion
window of 10 times the maximum datagram size (max_datagram_size), window of 10 times the maximum datagram size (max_datagram_size),
limited to the larger of 14720 or twice the maximum datagram size. limited to the larger of 14720 bytes or twice the maximum datagram
This follows the analysis and recommendations in [RFC6928], size. This follows the analysis and recommendations in [RFC6928],
increasing the byte limit to account for the smaller 8 byte overhead increasing the byte limit to account for the smaller 8 byte overhead
of UDP compared to the 20 byte overhead for TCP. of UDP compared to the 20 byte overhead for TCP.
If the maximum datagram size changes during the connection, the If the maximum datagram size changes during the connection, the
initial congestion window SHOULD be recalculated with the new size. initial congestion window SHOULD be recalculated with the new size.
If the maximum datagram size is decreased in order to complete the If the maximum datagram size is decreased in order to complete the
handshake, the congestion window SHOULD be set to the new initial handshake, the congestion window SHOULD be set to the new initial
congestion window. congestion window.
Prior to validating the client's address, the server can be further Prior to validating the client's address, the server can be further
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trip time. Expressed as a rate in bytes: trip time. Expressed as a rate in bytes:
rate = N * congestion_window / smoothed_rtt rate = N * congestion_window / smoothed_rtt
Or, expressed as an inter-packet interval: Or, expressed as an inter-packet interval:
interval = smoothed_rtt * packet_size / congestion_window / N interval = smoothed_rtt * packet_size / congestion_window / N
Using a value for "N" that is small, but at least 1 (for example, Using a value for "N" that is small, but at least 1 (for example,
1.25) ensures that variations in round-trip time do not result in 1.25) ensures that variations in round-trip time do not result in
under-utilization of the congestion window. Values of 'N' larger under-utilization of the congestion window.
than 1 ultimately result in sending packets as acknowledgments are
received rather than when timers fire, provided the congestion window
is fully utilized and acknowledgments arrive at regular intervals.
Practical considerations, such as packetization, scheduling delays, Practical considerations, such as packetization, scheduling delays,
and computational efficiency, can cause a sender to deviate from this and computational efficiency, can cause a sender to deviate from this
rate over time periods that are much shorter than a round-trip time. rate over time periods that are much shorter than a round-trip time.
One possible implementation strategy for pacing uses a leaky bucket One possible implementation strategy for pacing uses a leaky bucket
algorithm, where the capacity of the "bucket" is limited to the algorithm, where the capacity of the "bucket" is limited to the
maximum burst size and the rate the "bucket" fills is determined by maximum burst size and the rate the "bucket" fills is determined by
the above function. the above function.
skipping to change at page 28, line 31 skipping to change at page 28, line 31
9. IANA Considerations 9. IANA Considerations
This document has no IANA actions. This document has no IANA actions.
10. References 10. References
10.1. Normative References 10.1. Normative References
[QUIC-TLS] Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure [QUIC-TLS] Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure
QUIC", Work in Progress, Internet-Draft, draft-ietf-quic- QUIC", Work in Progress, Internet-Draft, draft-ietf-quic-
tls-30, September 10, 2020, tls-31, 25 September 2020,
<https://tools.ietf.org/html/draft-ietf-quic-tls-30>. <https://tools.ietf.org/html/draft-ietf-quic-tls-31>.
[QUIC-TRANSPORT] [QUIC-TRANSPORT]
Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", Work in Progress, Multiplexed and Secure Transport", Work in Progress,
Internet-Draft, draft-ietf-quic-transport-30, September Internet-Draft, draft-ietf-quic-transport-31, 25 September
10, 2020, <https://tools.ietf.org/html/draft-ietf-quic- 2020, <https://tools.ietf.org/html/draft-ietf-quic-
transport-30>. transport-31>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage [RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>. March 2017, <https://www.rfc-editor.org/info/rfc8085>.
skipping to change at page 29, line 17 skipping to change at page 29, line 17
[FACK] Mathis, M. and J. Mahdavi, "Forward Acknowledgement: [FACK] Mathis, M. and J. Mahdavi, "Forward Acknowledgement:
Refining TCP Congestion Control", ACM SIGCOMM , August Refining TCP Congestion Control", ACM SIGCOMM , August
1996. 1996.
[PRR] Mathis, M., Dukkipati, N., and Y. Cheng, "Proportional [PRR] Mathis, M., Dukkipati, N., and Y. Cheng, "Proportional
Rate Reduction for TCP", RFC 6937, DOI 10.17487/RFC6937, Rate Reduction for TCP", RFC 6937, DOI 10.17487/RFC6937,
May 2013, <https://www.rfc-editor.org/info/rfc6937>. May 2013, <https://www.rfc-editor.org/info/rfc6937>.
[RACK] Cheng, Y., Cardwell, N., Dukkipati, N., and P. Jha, "The [RACK] Cheng, Y., Cardwell, N., Dukkipati, N., and P. Jha, "The
RACK-TLP loss detection algorithm for TCP", Work in RACK-TLP loss detection algorithm for TCP", Work in
Progress, Internet-Draft, draft-ietf-tcpm-rack-10, August Progress, Internet-Draft, draft-ietf-tcpm-rack-10, 22
22, 2020, <http://www.ietf.org/internet-drafts/draft-ietf- August 2020, <http://www.ietf.org/internet-drafts/draft-
tcpm-rack-10.txt>. ietf-tcpm-rack-10.txt>.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP", of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001, RFC 3168, DOI 10.17487/RFC3168, September 2001,
<https://www.rfc-editor.org/info/rfc3168>. <https://www.rfc-editor.org/info/rfc3168>.
[RFC3465] Allman, M., "TCP Congestion Control with Appropriate Byte [RFC3465] Allman, M., "TCP Congestion Control with Appropriate Byte
Counting (ABC)", RFC 3465, DOI 10.17487/RFC3465, February Counting (ABC)", RFC 3465, DOI 10.17487/RFC3465, February
2003, <https://www.rfc-editor.org/info/rfc3465>. 2003, <https://www.rfc-editor.org/info/rfc3465>.
skipping to change at page 44, line 25 skipping to change at page 44, line 25
pto_count = 0 pto_count = 0
SetLossDetectionTimer() SetLossDetectionTimer()
Appendix C. Change Log Appendix C. Change Log
*RFC Editor's Note:* Please remove this section prior to *RFC Editor's Note:* Please remove this section prior to
publication of a final version of this document. publication of a final version of this document.
Issue and pull request numbers are listed with a leading octothorp. Issue and pull request numbers are listed with a leading octothorp.
C.1. Since draft-ietf-quic-recovery-29 C.1. Since draft-ietf-quic-recovery-30
Editorial changes only.
C.2. Since draft-ietf-quic-recovery-29
* Allow caching of packets that can't be decrypted, by allowing the * Allow caching of packets that can't be decrypted, by allowing the
reported acknowledgment delay to exceed max_ack_delay prior to reported acknowledgment delay to exceed max_ack_delay prior to
confirming the handshake (#3821, #3980, #4035, #3874) confirming the handshake (#3821, #3980, #4035, #3874)
* Persistent congestion cannot include packets sent before the first * Persistent congestion cannot include packets sent before the first
RTT sample for the path (#3875, #3889) RTT sample for the path (#3875, #3889)
* Recommend reset of min_rtt in persistent congestion (#3927, #3975) * Recommend reset of min_rtt in persistent congestion (#3927, #3975)
* Persistent congestion is independent of packet number space * Persistent congestion is independent of packet number space
(#3939, #3961) (#3939, #3961)
* Only limit bursts to the initial window without information about * Only limit bursts to the initial window without information about
the path (#3892, #3936) the path (#3892, #3936)
* Add normative requirements for increasing and reducing the * Add normative requirements for increasing and reducing the
congestion window (#3944, #3978, #3997, #3998) congestion window (#3944, #3978, #3997, #3998)
C.2. Since draft-ietf-quic-recovery-28 C.3. Since draft-ietf-quic-recovery-28
* Refactored pseudocode to correct PTO calculation (#3564, #3674, * Refactored pseudocode to correct PTO calculation (#3564, #3674,
#3681) #3681)
C.3. Since draft-ietf-quic-recovery-27 C.4. Since draft-ietf-quic-recovery-27
* Added recommendations for speeding up handshake under some loss * Added recommendations for speeding up handshake under some loss
conditions (#3078, #3080) conditions (#3078, #3080)
* PTO count is reset when handshake progress is made (#3272, #3415) * PTO count is reset when handshake progress is made (#3272, #3415)
* PTO count is not reset by a client when the server might be * PTO count is not reset by a client when the server might be
awaiting address validation (#3546, #3551) awaiting address validation (#3546, #3551)
* Recommend repairing losses immediately after entering the recovery * Recommend repairing losses immediately after entering the recovery
period (#3335, #3443) period (#3335, #3443)
* Clarified what loss conditions can be ignored during the handshake * Clarified what loss conditions can be ignored during the handshake
(#3456, #3450) (#3456, #3450)
* Allow, but don't recommend, using RTT from previous connection to * Allow, but don't recommend, using RTT from previous connection to
seed RTT (#3464, #3496) seed RTT (#3464, #3496)
* Recommend use of adaptive loss detection thresholds (#3571, #3572) * Recommend use of adaptive loss detection thresholds (#3571, #3572)
C.4. Since draft-ietf-quic-recovery-26 C.5. Since draft-ietf-quic-recovery-26
No changes. No changes.
C.5. Since draft-ietf-quic-recovery-25 C.6. Since draft-ietf-quic-recovery-25
No significant changes. No significant changes.
C.6. Since draft-ietf-quic-recovery-24 C.7. Since draft-ietf-quic-recovery-24
* Require congestion control of some sort (#3247, #3244, #3248) * Require congestion control of some sort (#3247, #3244, #3248)
* Set a minimum reordering threshold (#3256, #3240) * Set a minimum reordering threshold (#3256, #3240)
* PTO is specific to a packet number space (#3067, #3074, #3066) * PTO is specific to a packet number space (#3067, #3074, #3066)
C.7. Since draft-ietf-quic-recovery-23 C.8. Since draft-ietf-quic-recovery-23
* Define under-utilizing the congestion window (#2630, #2686, #2675) * Define under-utilizing the congestion window (#2630, #2686, #2675)
* PTO MUST send data if possible (#3056, #3057) * PTO MUST send data if possible (#3056, #3057)
* Connection Close is not ack-eliciting (#3097, #3098) * Connection Close is not ack-eliciting (#3097, #3098)
* MUST limit bursts to the initial congestion window (#3160) * MUST limit bursts to the initial congestion window (#3160)
* Define the current max_datagram_size for congestion control * Define the current max_datagram_size for congestion control
(#3041, #3167) (#3041, #3167)
C.8. Since draft-ietf-quic-recovery-22 C.9. Since draft-ietf-quic-recovery-22
* PTO should always send an ack-eliciting packet (#2895) * PTO should always send an ack-eliciting packet (#2895)
* Unify the Handshake Timer with the PTO timer (#2648, #2658, #2886) * Unify the Handshake Timer with the PTO timer (#2648, #2658, #2886)
* Move ACK generation text to transport draft (#1860, #2916) * Move ACK generation text to transport draft (#1860, #2916)
C.9. Since draft-ietf-quic-recovery-21 C.10. Since draft-ietf-quic-recovery-21
* No changes * No changes
C.10. Since draft-ietf-quic-recovery-20 C.11. Since draft-ietf-quic-recovery-20
* Path validation can be used as initial RTT value (#2644, #2687) * Path validation can be used as initial RTT value (#2644, #2687)
* max_ack_delay transport parameter defaults to 0 (#2638, #2646) * max_ack_delay transport parameter defaults to 0 (#2638, #2646)
* ACK delay only measures intentional delays induced by the * ACK delay only measures intentional delays induced by the
implementation (#2596, #2786) implementation (#2596, #2786)
C.11. Since draft-ietf-quic-recovery-19 C.12. Since draft-ietf-quic-recovery-19
* Change kPersistentThreshold from an exponent to a multiplier * Change kPersistentThreshold from an exponent to a multiplier
(#2557) (#2557)
* Send a PING if the PTO timer fires and there's nothing to send * Send a PING if the PTO timer fires and there's nothing to send
(#2624) (#2624)
* Set loss delay to at least kGranularity (#2617) * Set loss delay to at least kGranularity (#2617)
* Merge application limited and sending after idle sections. Always * Merge application limited and sending after idle sections. Always
skipping to change at page 46, line 51 skipping to change at page 47, line 5
packet is ack-eliciting but the largest_acked is not (#2592) packet is ack-eliciting but the largest_acked is not (#2592)
* Don't arm the handshake timer if there is no handshake data * Don't arm the handshake timer if there is no handshake data
(#2590) (#2590)
* Clarify that the time threshold loss alarm takes precedence over * Clarify that the time threshold loss alarm takes precedence over
the crypto handshake timer (#2590, #2620) the crypto handshake timer (#2590, #2620)
* Change initial RTT to 500ms to align with RFC6298 (#2184) * Change initial RTT to 500ms to align with RFC6298 (#2184)
C.12. Since draft-ietf-quic-recovery-18 C.13. Since draft-ietf-quic-recovery-18
* Change IW byte limit to 14720 from 14600 (#2494) * Change IW byte limit to 14720 from 14600 (#2494)
* Update PTO calculation to match RFC6298 (#2480, #2489, #2490) * Update PTO calculation to match RFC6298 (#2480, #2489, #2490)
* Improve loss detection's description of multiple packet number * Improve loss detection's description of multiple packet number
spaces and pseudocode (#2485, #2451, #2417) spaces and pseudocode (#2485, #2451, #2417)
* Declare persistent congestion even if non-probe packets are sent * Declare persistent congestion even if non-probe packets are sent
and don't make persistent congestion more aggressive than RTO and don't make persistent congestion more aggressive than RTO
verified was (#2365, #2244) verified was (#2365, #2244)
* Move pseudocode to the appendices (#2408) * Move pseudocode to the appendices (#2408)
* What to send on multiple PTOs (#2380) * What to send on multiple PTOs (#2380)
C.13. Since draft-ietf-quic-recovery-17 C.14. Since draft-ietf-quic-recovery-17
* After Probe Timeout discard in-flight packets or send another * After Probe Timeout discard in-flight packets or send another
(#2212, #1965) (#2212, #1965)
* Endpoints discard initial keys as soon as handshake keys are * Endpoints discard initial keys as soon as handshake keys are
available (#1951, #2045) available (#1951, #2045)
* 0-RTT state is discarded when 0-RTT is rejected (#2300) * 0-RTT state is discarded when 0-RTT is rejected (#2300)
* Loss detection timer is cancelled when ack-eliciting frames are in * Loss detection timer is cancelled when ack-eliciting frames are in
skipping to change at page 47, line 45 skipping to change at page 47, line 48
controller (#2138, 2187) controller (#2138, 2187)
* Process ECN counts before marking packets lost (#2142) * Process ECN counts before marking packets lost (#2142)
* Mark packets lost before resetting crypto_count and pto_count * Mark packets lost before resetting crypto_count and pto_count
(#2208, #2209) (#2208, #2209)
* Congestion and loss recovery state are discarded when keys are * Congestion and loss recovery state are discarded when keys are
discarded (#2327) discarded (#2327)
C.14. Since draft-ietf-quic-recovery-16 C.15. Since draft-ietf-quic-recovery-16
* Unify TLP and RTO into a single PTO; eliminate min RTO, min TLP * Unify TLP and RTO into a single PTO; eliminate min RTO, min TLP
and min crypto timeouts; eliminate timeout validation (#2114, and min crypto timeouts; eliminate timeout validation (#2114,
#2166, #2168, #1017) #2166, #2168, #1017)
* Redefine how congestion avoidance in terms of when the period * Redefine how congestion avoidance in terms of when the period
starts (#1928, #1930) starts (#1928, #1930)
* Document what needs to be tracked for packets that are in flight * Document what needs to be tracked for packets that are in flight
(#765, #1724, #1939) (#765, #1724, #1939)
skipping to change at page 48, line 30 skipping to change at page 48, line 30
* Limit ack_delay by max_ack_delay (#2060, #2099) * Limit ack_delay by max_ack_delay (#2060, #2099)
* Initial keys are discarded once Handshake keys are available * Initial keys are discarded once Handshake keys are available
(#1951, #2045) (#1951, #2045)
* Reorder ECN and loss detection in pseudocode (#2142) * Reorder ECN and loss detection in pseudocode (#2142)
* Only cancel loss detection timer if ack-eliciting packets are in * Only cancel loss detection timer if ack-eliciting packets are in
flight (#2093, #2117) flight (#2093, #2117)
C.15. Since draft-ietf-quic-recovery-14 C.16. Since draft-ietf-quic-recovery-14
* Used max_ack_delay from transport params (#1796, #1782) * Used max_ack_delay from transport params (#1796, #1782)
* Merge ACK and ACK_ECN (#1783) * Merge ACK and ACK_ECN (#1783)
C.16. Since draft-ietf-quic-recovery-13 C.17. Since draft-ietf-quic-recovery-13
* Corrected the lack of ssthresh reduction in CongestionEvent * Corrected the lack of ssthresh reduction in CongestionEvent
pseudocode (#1598) pseudocode (#1598)
* Considerations for ECN spoofing (#1426, #1626) * Considerations for ECN spoofing (#1426, #1626)
* Clarifications for PADDING and congestion control (#837, #838, * Clarifications for PADDING and congestion control (#837, #838,
#1517, #1531, #1540) #1517, #1531, #1540)
* Reduce early retransmission timer to RTT/8 (#945, #1581) * Reduce early retransmission timer to RTT/8 (#945, #1581)
* Packets are declared lost after an RTO is verified (#935, #1582) * Packets are declared lost after an RTO is verified (#935, #1582)
C.17. Since draft-ietf-quic-recovery-12 C.18. Since draft-ietf-quic-recovery-12
* Changes to manage separate packet number spaces and encryption * Changes to manage separate packet number spaces and encryption
levels (#1190, #1242, #1413, #1450) levels (#1190, #1242, #1413, #1450)
* Added ECN feedback mechanisms and handling; new ACK_ECN frame * Added ECN feedback mechanisms and handling; new ACK_ECN frame
(#804, #805, #1372) (#804, #805, #1372)
C.18. Since draft-ietf-quic-recovery-11 C.19. Since draft-ietf-quic-recovery-11
No significant changes. No significant changes.
C.19. Since draft-ietf-quic-recovery-10 C.20. Since draft-ietf-quic-recovery-10
* Improved text on ack generation (#1139, #1159) * Improved text on ack generation (#1139, #1159)
* Make references to TCP recovery mechanisms informational (#1195) * Make references to TCP recovery mechanisms informational (#1195)
* Define time_of_last_sent_handshake_packet (#1171) * Define time_of_last_sent_handshake_packet (#1171)
* Added signal from TLS the data it includes needs to be sent in a * Added signal from TLS the data it includes needs to be sent in a
Retry packet (#1061, #1199) Retry packet (#1061, #1199)
* Minimum RTT (min_rtt) is initialized with an infinite value * Minimum RTT (min_rtt) is initialized with an infinite value
(#1169) (#1169)
C.20. Since draft-ietf-quic-recovery-09 C.21. Since draft-ietf-quic-recovery-09
No significant changes. No significant changes.
C.21. Since draft-ietf-quic-recovery-08 C.22. Since draft-ietf-quic-recovery-08
* Clarified pacing and RTO (#967, #977) * Clarified pacing and RTO (#967, #977)
C.22. Since draft-ietf-quic-recovery-07 C.23. Since draft-ietf-quic-recovery-07
* Include ACK delay in RTO(and TLP) computations (#981) * Include ACK delay in RTO(and TLP) computations (#981)
* ACK delay in SRTT computation (#961) * ACK delay in SRTT computation (#961)
* Default RTT and Slow Start (#590) * Default RTT and Slow Start (#590)
* Many editorial fixes. * Many editorial fixes.
C.23. Since draft-ietf-quic-recovery-06 C.24. Since draft-ietf-quic-recovery-06
No significant changes. No significant changes.
C.24. Since draft-ietf-quic-recovery-05 C.25. Since draft-ietf-quic-recovery-05
* Add more congestion control text (#776) * Add more congestion control text (#776)
C.25. Since draft-ietf-quic-recovery-04 C.26. Since draft-ietf-quic-recovery-04
No significant changes. No significant changes.
C.26. Since draft-ietf-quic-recovery-03 C.27. Since draft-ietf-quic-recovery-03
No significant changes. No significant changes.
C.27. Since draft-ietf-quic-recovery-02 C.28. Since draft-ietf-quic-recovery-02
* Integrate F-RTO (#544, #409) * Integrate F-RTO (#544, #409)
* Add congestion control (#545, #395) * Add congestion control (#545, #395)
* Require connection abort if a skipped packet was acknowledged * Require connection abort if a skipped packet was acknowledged
(#415) (#415)
* Simplify RTO calculations (#142, #417) * Simplify RTO calculations (#142, #417)
C.28. Since draft-ietf-quic-recovery-01 C.29. Since draft-ietf-quic-recovery-01
* Overview added to loss detection * Overview added to loss detection
* Changes initial default RTT to 100ms * Changes initial default RTT to 100ms
* Added time-based loss detection and fixes early retransmit * Added time-based loss detection and fixes early retransmit
* Clarified loss recovery for handshake packets * Clarified loss recovery for handshake packets
* Fixed references and made TCP references informative * Fixed references and made TCP references informative
C.29. Since draft-ietf-quic-recovery-00 C.30. Since draft-ietf-quic-recovery-00
* Improved description of constants and ACK behavior * Improved description of constants and ACK behavior
C.30. Since draft-iyengar-quic-loss-recovery-01 C.31. Since draft-iyengar-quic-loss-recovery-01
* Adopted as base for draft-ietf-quic-recovery * Adopted as base for draft-ietf-quic-recovery
* Updated authors/editors list * Updated authors/editors list
* Added table of contents * Added table of contents
Appendix D. Contributors Appendix D. Contributors
The IETF QUIC Working Group received an enormous amount of support The IETF QUIC Working Group received an enormous amount of support
from many people. The following people provided substantive from many people. The following people provided substantive
contributions to this document: Alessandro Ghedini, Benjamin contributions to this document:
Saunders, Gorry Fairhurst, 奥 一穂 (Kazuho Oku), Lars Eggert, Magnus
Westerlund, Marten Seemann, Martin Duke, Martin Thomson, Nick Banks, * Alessandro Ghedini
Praveen Balasubramanian.
* Benjamin Saunders
* Gorry Fairhurst
* 山本和彦 (Kazu Yamamoto)
* 奥 一穂 (Kazuho Oku)
* Lars Eggert
* Magnus Westerlund
* Marten Seemann
* Martin Duke
* Martin Thomson
* Mirja Kühlewind
* Nick Banks
* Praveen Balasubramanian
Acknowledgments Acknowledgments
Authors' Addresses Authors' Addresses
Jana Iyengar (editor) Jana Iyengar (editor)
Fastly Fastly
Email: jri.ietf@gmail.com Email: jri.ietf@gmail.com
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