[tcpm] Loose ends tied up in draft-ietf-tcpm-accurate-ecn-19 (AccECN)

[Bob Briscoe <[e-mail]>]

@Yoshi, this completes all the changes I believe have been requested or 
are needed.

@tcpm, Summary of changes (see diff linked below for full details)


      ==Normative Changes==


3.3.3. 
<https://datatracker.ietf.org/doc/html/draft-ietf-tcpm-accurate-ecn-19#section-3.3.3> 
Requirements for TCP ACK Filtering

  * RFC3449 already says ACK filtering nodes have to ensure they don't
    interfere with the correction operation of ECN feedback.
      o Altho' RFC3449 references RFC3168, given AccECN updates RFC3168,
        the requirement can beassumed to apply to both RFC3168 and
        AccECN f/.
      o So no need to update RFC3449 and altered text accordingly.
  * Also stated worst-case wrap.
  * All as discussed in the thread "RFC3449 and AccECN
    <https://mailarchive.ietf.org/arch/msg/tcpm/hD9W-STuLv3Km04x0Cy1obgjApA/>"


      ==Normative/ Technical Changes==

3.2.3. 
<https://datatracker.ietf.org/doc/html/draft-ietf-tcpm-accurate-ecn-19#section-3.2.3> 
The AccECN Option

  * If partial implementation, recommended at least implementing sending
    of AccECN Option, even if not the receive logic (switched round from
    previous version).
  * All as discussed in the thread "Partial implementation of AccECN
    Option logic
    <https://mailarchive.ietf.org/arch/msg/tcpm/0uJumvVAu4i88fmbT7wKlrpP5B0/>"
    and as proposed at the IETF-113 tcpm meeting


      ==Editorial==

Altered order of "3.2.2.3. 
<https://datatracker.ietf.org/doc/html/draft-ietf-tcpm-accurate-ecn-19#section-3.2.2.3> 
Testing for Mangling of the IP/ECN Field" to better reflect the order 
the implementation uses (suggested by Ilpo).



Bob



On 11/07/2022 15:40, [e-mail] wrote:
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> This draft is a work item of the TCP Maintenance and Minor Extensions WG of the IETF.
>
>          Title           : More Accurate ECN Feedback in TCP
>          Authors         : Bob Briscoe
>                            Mirja Kühlewind
>                            Richard Scheffenegger
>    Filename        : draft-ietf-tcpm-accurate-ecn-19.txt
>    Pages           : 61
>    Date            : 2022-07-11
>
> Abstract:
>     Explicit Congestion Notification (ECN) is a mechanism where network
>     nodes can mark IP packets instead of dropping them to indicate
>     incipient congestion to the end-points.  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 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 to specify a scheme to provide 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 a new TCP option,
>     which is never used on the TCP SYN.  The document also specifies the
>     treatment of this updated TCP wire protocol by middleboxes.
>
>
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-tcpm-accurate-ecn/
>
> There is also an HTML version available at:
> https://www.ietf.org/archive/id/draft-ietf-tcpm-accurate-ecn-19.html
>
> A diff from the previous version is available at:
> https://www.ietf.org/rfcdiff?url2=draft-ietf-tcpm-accurate-ecn-19
>
>
> Internet-Drafts are also available by rsync at rsync.ietf.org::internet-drafts
>
>
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-- 
________________________________________________________________
Bob Briscoehttp://bobbriscoe.net/