Date: Wed, 17 Jul 2002 19:28:38 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Garrett Wollman <wollman@lcs.mit.edu> Cc: cvs-committers@FreeBSD.ORG, <cvs-all@FreeBSD.ORG> Subject: Re: cvs commit: src/sys/netinet tcp_timer.h Message-ID: <200207180228.g6I2Scpv004823@apollo.backplane.com> References: <20020717185653.C82638-100000@patrocles.silby.com> <200207180102.g6I129Gw004350@apollo.backplane.com> <200207180206.g6I266ma000510@khavrinen.lcs.mit.edu>
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:<<On Wed, 17 Jul 2002 18:02:09 -0700 (PDT), Matthew Dillon <dillon@apollo.backplane.com> said:
:
:> Actually,
:> I think the one second minimum is absurd anyway, so no, I am not
:> going to back it out.
:
:The standard says one second, period. It's not your choice to make.
:
:-GAWollman
I've looked through five RFCs. I have been unable to locate any
lower bound requirement fro the retransmission timeout. The best
I've found is in RFC1122, 4.2.3.1:
The recommended upper and lower bounds on the RTO are known
to be inadequate on large internets. The lower bound SHOULD
be measured in fractions of a second (to accommodate high
speed LANs) and the upper bound should be 2*MSL, i.e., 240
seconds.
All the other references I've found... New Reno and the two
congestion control RFCs (one being the fast-retransmit RFC) simply
state something on the order of 2*RTT or something similar.
RFC793 has an eample of an RTO timeout calculation where it says
"where UBOUND is an upper bound on the timeout (e.g., 1 minute),
LBOUND is a lower bound on the timeout (e.g., 1 second), ALPHA is
a smoothing factor (e.g., .8 to .9), and BETA is a delay variance
factor (e.g., 1.3 to 2.0)."
This is obviously NOT a requirement of any sort, and besides it is in
RFC793... an extremely old RFC (1981).
-Matt
Matthew Dillon
<dillon@backplane.com>
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