Subject: [Tsvwg] T3 cannot timeout???

From: [email-masked]
Date: Fri, 26 Apr 2002 00:47:34 -0400

Hello,
We've found a Here's a case we found, hopefully someone can help!

2 peers (A and B) with 2 destinations (1 and 2) each, both using the same
path as the 'primary'.
Primary ethernet goes down.
Side A detects this, and switches to destination 2.
Side B's T3 timer hasn't yet expired, but starts receiving data from A on
2.  B sends SACK on 2nd path (since that's where it got the data), and
since it also has data to send, it bundles DATA chunks with the SACK.
The data bundled with the (many?) SACKs on dest 2 will eventually be
SACKed.  These SACKs must contain GAP reports, indicating the missing TSNs
(the ones sent to dest 1 with TSNs lower than those bundled with the
SACKs).  Once 4 of these SACKs with GAPs are received, Side B will "fast
retransmit" those chunks on dest 2.  According to the RFC (7.2.4), Side B
will restart T3 for dest 1, since it will be retransmitting the lowest TSN
sent to it.  It appears that this will continue forever.  Side B will never
see dest 1 as failed, since its T3 will continually be reset, but it will
waste a lot of time and energy sending it data!

Has anyone seen this?  Any suggestions?

======================================
Dave Sclarsky
Radisys Corporation
520 Fellowship Road
Suite C-304
Mt. Laurel, NJ 08054
email:[email-masked]
voice:856.642.9229x231 fax:856.642.0252

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From: Mohammed Ashraf <[email-masked]>
Date: Fri, 26 Apr 2002 13:08:57 +0530

> waste a lot of time and energy sending it data!

Shudn't the timer be started against the destination on which this lowest
TSN is retransmitted ( i.e here Dest :2  )?