SACK retransmits multiple segments respond to single dupack

[Mark Allman]

> Which release are you experimenting with ? There was a bug 
> in 5.3 that would cause SACK to burst multiple segments on
> a dupack reception. But that was fixed both in -current
> and in RELENG_5 (1.100.2.3 and 1.102). From what I see,
> the fix was never MFC'ed to RELENG_5_3. 
> 
> Referencing the code in -current,
> 
> dupack handling starts at line tcp_input.c:1797. When SACK
> recovery is first set up, upon reception of 3 dupacks, we
> set cwnd to 3 (line 1867) and call tcp_output(), which would
> cause 3 segments from the scoreboard to be retransmitted.

I do not understand why receiving 3 dupacks would cause a retransmit of
3 segments.  One retransmit I can understand.  But, then we shouldn't be
in packet conservation for a bit while some of the segments drain from
the network to effectively halve the sending rate (because we noted
congestion).

allman



--
Mark Allman -- ICIR -- http://www.icir.org/mallman/



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