[lwip-devel] [bug #20126] Zero ssthresh bug

[Per-Henrik Lundblom]

Follow-up Comment #2, bug #20126 (project lwip):

Oh, as always when you go public with something it appears you are wrong =/

Actually, my interpretion was a bit wrong. Now when I read the text I would
say ssthresh never can be less than 2*MSS. This haven't been tested with lwIP
because I don't have the test setup at hand today.

Anyway, I get the minimum value of 2*MSS from TCP/IP Illustrated chapter 21.6
from the part describing the congestion avoidance algoritm. Point 3 reads:

"When congestion occurs (indicated by a timeout or the reception of duplicate
ACKs), one-half of the current window size (the minimum of cwnd and the
receiver's advertised window, but at least two segments) is saved in
ssthresh. Additionally, if the congestion is indicated by a timeout, cwnd is
set to one segment (i.e., slow start)."

It clearly says that at least two segments are saved in ssthresh.

/PH

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