TCP Maintenance and Minor Extensions (tcpm) Internet Drafts

      
 TCP Extended Data Offset Option
 
 draft-ietf-tcpm-tcp-edo-14.txt
 Date: 05/09/2024
 Authors: Joseph Touch, Wesley Eddy
 Working Group: TCP Maintenance and Minor Extensions (tcpm)
 TCP segments include a Data Offset field to indicate space for TCP options but the size of the field can limit the space available for complex options such as SACK and Multipath TCP and can limit the combination of such options supported in a single connection. This document updates RFC 9293 with an optional TCP extension to that space to support the use of multiple large options. It also explains why the initial SYN of a connection cannot be extending a single segment.
 More Accurate Explicit Congestion Notification (ECN) Feedback in TCP
 
 draft-ietf-tcpm-accurate-ecn-30.txt
 Date: 07/07/2024
 Authors: Bob Briscoe, Mirja Kuehlewind, Richard Scheffenegger
 Working Group: TCP Maintenance and Minor Extensions (tcpm)
 Explicit Congestion Notification (ECN) is a mechanism where network nodes can mark IP packets instead of dropping them to indicate incipient congestion to the endpoints. Receivers with an ECN-capable transport protocol feed back this information to the sender. ECN was originally specified for TCP in such a way that only one feedback signal can be transmitted per Round-Trip Time (RTT). Recent new TCP mechanisms like Congestion Exposure (ConEx), Data Center TCP (DCTCP) or Low Latency, Low Loss, and Scalable Throughput (L4S) need more accurate ECN feedback information whenever more than one marking is received in one RTT. This document updates the original ECN specification in RFC 3168 to specify a scheme that provides more than one feedback signal per RTT in the TCP header. Given TCP header space is scarce, it allocates a reserved header bit previously assigned to the ECN-Nonce. It also overloads the two existing ECN flags in the TCP header. The resulting extra space is exploited to feed back the IP-ECN field received during the 3-way handshake as well. Supplementary feedback information can optionally be provided in two new TCP option alternatives, which are never used on the TCP SYN. The document also specifies the treatment of this updated TCP wire protocol by middleboxes.
 ECN++: Adding Explicit Congestion Notification (ECN) to TCP Control Packets
 
 draft-ietf-tcpm-generalized-ecn-16.txt
 Date: 20/10/2024
 Authors: Marcelo Bagnulo, Bob Briscoe
 Working Group: TCP Maintenance and Minor Extensions (tcpm)
 This document specifies an experimental modification to ECN when used with TCP. It allows the use of ECN in the IP header of the following TCP packets: SYNs, SYN/ACKs, pure ACKs, Window probes, FINs, RSTs and retransmissions. This specification obsoletes RFC5562, which described a different way to use ECN on SYN/ACKs alone.
 Proportional Rate Reduction for TCP
 
 draft-ietf-tcpm-prr-rfc6937bis-13.txt
 Date: 09/11/2024
 Authors: Matt Mathis, Nandita Dukkipati, Yuchung Cheng, Neal Cardwell
 Working Group: TCP Maintenance and Minor Extensions (tcpm)
 This document updates the experimental Proportional Rate Reduction (PRR) algorithm, described RFC 6937, to standards track. PRR provides logic to regulate the amount of data sent by TCP or other transport protocols during fast recovery. PRR accurately regulates the actual flight size through recovery such that at the end of recovery it will be as close as possible to the slow start threshold (ssthresh), as determined by the congestion control algorithm.
 TCP ACK Rate Request Option
 
 draft-ietf-tcpm-ack-rate-request-06.txt
 Date: 02/10/2024
 Authors: Carles Gomez, Jon Crowcroft
 Working Group: TCP Maintenance and Minor Extensions (tcpm)
 TCP Delayed Acknowledgments (ACKs) is a widely deployed mechanism that allows reducing protocol overhead in many scenarios. However, Delayed ACKs may also contribute to suboptimal performance. When a relatively large congestion window (cwnd) can be used, less frequent ACKs may be desirable. On the other hand, in relatively small cwnd scenarios, eliciting an immediate ACK may avoid unnecessary delays that may be incurred by the Delayed ACKs mechanism. This document specifies the TCP ACK Rate Request (TARR) option. This option allows a sender to request the ACK rate to be used by a receiver, and it also allows to request immediate ACKs from a receiver.
 Improve TCP Handling of Out-of-Window Packets to Mitigate Ghost ACKs
 
 draft-ietf-tcpm-tcp-ghost-acks-01.txt
 Date: 18/10/2024
 Authors: Yepeng Pan
 Working Group: TCP Maintenance and Minor Extensions (tcpm)
 Historically, TCP as specified in RFC 793 was threatened by the blind data injection attack because of the loose SEG.ACK value validation, where the SEG.ACK value of a TCP segment is considered valid as long as it does not acknowledge data ahead of what has been sent. RFC 5961 improved the input validation by shrinking the range of acceptable SEG.ACK values in a TCP segment. Later, RFC 9293 incorporated the updates proposed by RFC 5961 as a TCP stack implementation option. However, an endpoint that follows the RFC 9293 specifications can still accept a TCP segment containing an SEG.ACK value acknowledging data that the endpoint has never sent. This document specifies small modifications to the way TCP verifies incoming TCP segments' SEG.ACK value to prevent TCP from accepting such invalid SEG.ACK values.

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TCP Maintenance and Minor Extensions (tcpm)

WG Name TCP Maintenance and Minor Extensions
Acronym tcpm
Area Web and Internet Transport (wit)
State Active
Charter charter-ietf-tcpm-10 Approved
Status update Show Changed 2020-07-23
Document dependencies
Additional resources Issue tracker, Wiki, Zulip Stream
Personnel Chairs Ian Swett, Michael Tüxen, Yoshifumi Nishida
Area Director Zaheduzzaman Sarker
Mailing list Address tcpm@ietf.org
To subscribe https://www.ietf.org/mailman/listinfo/tcpm
Archive https://mailarchive.ietf.org/arch/browse/tcpm/
Chat Room address https://zulip.ietf.org/#narrow/stream/tcpm

Charter for Working Group

TCP is currently one of the Internet's predominant transport protocols. TCPM
is the working group within the IETF that handles small TCP changes,
i.e., minor extensions to TCP algorithms and protocol mechanisms.
The TCPM WG serves several purposes:

  • The WG mostly focuses on maintenance issues (e.g., bug fixes) and
    modest changes to the protocol, algorithms, and interfaces that
    maintain TCP's utility.

  • The WG is a venue for moving current TCP specifications along the
    standards track.

  • The WG maintains Multipath TCP (MPTCP) and is a home for minor
    MPTCP enhancements including updates to the existing multipath
    congestion control.

The preferred venue for Congestion control work is generally CCWG or ICCRG. However, TCPM can take on such work in coordination with those groups, especially if it relies on TCP-specific protocol elements.

New TCPM milestones that fall within the scope specified within the
charter can be added after consensus on acceptance in the working
group and approval by the responsible Area Director.

Milestones

Date Milestone Associated documents
Aug 2025 Submit document on adding acknowledgement rate handling for TCP to the IESG for publication as Experimental RFC draft-ietf-tcpm-ack-rate-request
Apr 2025 Submit document on handling ghost ACKS to the IESG as a Proposed Standard RFC draft-ietf-tcpm-tcp-ghost-acks
Apr 2025 Submit document on a TCP Extended Data Offset Option to the IESG as a Proposed Standard RFC draft-ietf-tcpm-tcp-edo
Dec 2024 Submit document on adding Explicit Congestion Notification (ECN) to TCP Control Packets to the IESG for publication as Experimental RFC draft-ietf-tcpm-generalized-ecn
Oct 2024 Submit RFC6937bis document to the IESG for publication as a Proposed Standard RFC draft-ietf-tcpm-prr-rfc6937bis
Sep 2024 Submit specification of more accurate ECN feedback in TCP to the IESG for publication as a Proposed Standard RFC draft-ietf-tcpm-accurate-ecn