Subject: Re: [Tsvwg] Issues with draft-blanton-dsack-use-02

From: Mark Allman <[email-masked]>
Date: Thu, 14 Aug 2003 14:59:46 -0400

Folks-

Ethan and I just revised the i-d per the thread on tsvwg over the
last month.  The two major changes to the document are:

  * if the SACK scoreboard is empty when a DSACK rolls in then we
    say the TCP cannot revert its congestion control state because
    the presumption is that all the ACKs have been lost

  * if the TCP ertransmits something more than once then the TCP
    cannot revert the congestion control state because DSACKs can no
    longer resolve the retransmission ambiguity

We have sent the new version of the i-d to the archives and so it
will appear in the standard places in the next few days.  It is
available at: 

 http://roland.grc.nasa.gov/~mallman/papers/draft-ietf-tsvwg-dup-notify-01.txt

now.

We would appreciate comments on the new version.

Thanks,
allman

--
Mark Allman -- BBN/NASA GRC -- http://roland.grc.nasa.gov/~mallman/

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From: Sourabh Ladha <[email-masked]>
Date: Fri, 15 Aug 2003 07:45:13 -0400 (EDT)

Hi Mark/All,

* In the draft the following is about the SACK scoreboard: "We assume the
TCP sender has a data structure to hold selective acknowledgment
information (e.g., as outlined in [RFC3517])."

Traditionally entries lying below the cumulative ACK point are deleted
from the scoreboard. But the DSACK information normally comes after loss
recovery has exited. So how long should the scoreboard entries be
maintained beyond what is required in 3517? (1 ACK after loss recovery
exits in Fast retransmit; and N Acks after loss recovery exits in a
timeout (GoBackN)?)

* In the Security Considerations, ECN Nonce 3540 is offered as a
protection. But 3540 calls for disabling Nonce Sum checks for DupAcks. Is
the draft suggesting some extension to 3540 that NS be checked for DupAcks
carrying DSACK?

It may be helpful to be more explicit on the above in the ID.

Thanks