Date: Thu, 18 Jul 2002 12:29:22 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Bosko Milekic <bmilekic@unixdaemons.com> Cc: cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG Subject: Re: cvs commit: src/sys/netinet tcp_subr.c tcp_timer.c tcp_timer.h Message-ID: <200207181929.g6IJTMsF019578@apollo.backplane.com> References: <200207181906.g6IJ6CJI048667@freefall.freebsd.org> <20020718150731.A61071@unixdaemons.com>
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:On Thu, Jul 18, 2002 at 12:06:12PM -0700, Matt Dillon wrote:
:[...]
:> Please note that the 200ms slop is debateable.
:> This commit is not meant to be a line in the sand,
:> and if the community winds up deciding that increasing
:> it is the correct solution then it's easy to do.
:> Note that larger values will destroy performance
:> on lossy networks while smaller values may result in
:> a greater number of unnecessary retransmits.
:
: Thanks!
:
:> Revision Changes Path
:> 1.137 +3 -1 src/sys/netinet/tcp_subr.c
:> 1.52 +8 -0 src/sys/netinet/tcp_timer.c
:> 1.21 +21 -4 src/sys/netinet/tcp_timer.h
:
:Cheers,
:--
:Bosko Milekic
:bmilekic@unixdaemons.com
This will at least make it easier for people to test
different combinations.
Note that net.inet.tcp.rexmit_slop is instantaniously
applied, but net.inet.tcp.rexmit_min is cached when
a new TCP connection is initiated and so you must
exit and re-create the TCP connection when testing
changes in rexmit_min (e.g. you have to quit out of
ftp and ftp back in, if using passive-mode ftp).
Recommended testing (transmission path from the modified
host, not the receive path):
* over a wireless network
* over dummynet with packet losses of 0.1% to 10%
(0.001 to 0.10).
* over a LAN
* over the internet (cablemodem, DSL, etc...)
* with window scaling and large buffers
Test with slop values of 20, 50, 100, 200, 500, and 1000 ms.
Observe netstat -s | head -20 output for number of retransmits
sent and duplicate acks received. Observe performance variances
with netstat -in 1, observe interactive performance typing over
ssh through dummynet (or on a wireless network at the edge of
its range). etc...
-Matt
Matthew Dillon
<dillon@backplane.com>
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