A brief illustrative "tcpdump -w" trace of a modified "netpipe" doing
unidirectional streaming of 1-byte messages from n027 to n028 is
enclosed. These excerpts were collected on the sender side. This
pattern repeats at every 41st message, delaying the message by about 10
milliseconds. (PentiumII/400, Linux kernel 2.2.2, tulip.c:v0.90Q,
switched fast ethernet in full duplex mode).
Andrea's patch speeds up acknowledgments and reduces the 10-20 ms delays
to about 1 ms (i.e. 1000 microseconds), but the root cause of the delays
is not yet clear. Under ideal circumstances, 1-byte messages can arrive
about 3-4 microseconds apart, so a delay of 1000 microseconds is still a
significant interruption in the flow.
Sincerely,
Josip
-- Dr. Josip Loncaric, Senior Staff Scientist mailto:josip@icase.edu ICASE, Mail Stop 403 http://www.icase.edu/~josip/ NASA Langley Research Center mailto:j.loncaric@larc.nasa.gov Hampton, VA 23681-2199, USA Tel. +1 757 864-2192 Fax +1 757 864-6134 --------------D000D00FFAB73DB2B0B33FA0 Content-Type: text/plain; charset=us-ascii; name="pattern" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="pattern"[...] 920325328.727886 0:a0:cc:39:1b:4c 0:a0:cc:39:2d:af ip 66: n028.5002 > n027.listen: . ack 243 win 32120 <nop,nop,timestamp 19773 19076> (DF) 920325328.727975 0:a0:cc:39:2d:af 0:a0:cc:39:1b:4c ip 67: n027.listen > n028.5002: P 243:244(1) ack 113 win 32120 <nop,nop,timestamp 19077 19773> (DF) 920325328.728013 0:a0:cc:39:2d:af 0:a0:cc:39:1b:4c ip 67: n027.listen > n028.5002: P 244:245(1) ack 113 win 32120 <nop,nop,timestamp 19077 19773> (DF) 920325328.728047 0:a0:cc:39:2d:af 0:a0:cc:39:1b:4c ip 67: n027.listen > n028.5002: P 245:246(1) ack 113 win 32120 <nop,nop,timestamp 19077 19773> (DF) [...] 920325328.729258 0:a0:cc:39:2d:af 0:a0:cc:39:1b:4c ip 67: n027.listen > n028.5002: P 281:282(1) ack 113 win 32120 <nop,nop,timestamp 19077 19773> (DF) 920325328.729291 0:a0:cc:39:2d:af 0:a0:cc:39:1b:4c ip 67: n027.listen > n028.5002: P 282:283(1) ack 113 win 32120 <nop,nop,timestamp 19077 19773> (DF) 920325328.729323 0:a0:cc:39:2d:af 0:a0:cc:39:1b:4c ip 67: n027.listen > n028.5002: P 283:284(1) ack 113 win 32120 <nop,nop,timestamp 19077 19773> (DF) 920325328.737886 0:a0:cc:39:1b:4c 0:a0:cc:39:2d:af ip 66: n028.5002 > n027.listen: . ack 284 win 32120 <nop,nop,timestamp 19774 19077> (DF) 920325328.737975 0:a0:cc:39:2d:af 0:a0:cc:39:1b:4c ip 67: n027.listen > n028.5002: P 284:285(1) ack 113 win 32120 <nop,nop,timestamp 19078 19774> (DF) 920325328.738013 0:a0:cc:39:2d:af 0:a0:cc:39:1b:4c ip 67: n027.listen > n028.5002: P 285:286(1) ack 113 win 32120 <nop,nop,timestamp 19078 19774> (DF) [...] 920325328.739291 0:a0:cc:39:2d:af 0:a0:cc:39:1b:4c ip 67: n027.listen > n028.5002: P 323:324(1) ack 113 win 32120 <nop,nop,timestamp 19078 19774> (DF) 920325328.739323 0:a0:cc:39:2d:af 0:a0:cc:39:1b:4c ip 67: n027.listen > n028.5002: P 324:325(1) ack 113 win 32120 <nop,nop,timestamp 19078 19774> (DF) 920325328.747886 0:a0:cc:39:1b:4c 0:a0:cc:39:2d:af ip 66: n028.5002 > n027.listen: . ack 325 win 32120 <nop,nop,timestamp 19775 19078> (DF) 920325328.747975 0:a0:cc:39:2d:af 0:a0:cc:39:1b:4c ip 67: n027.listen > n028.5002: P 325:326(1) ack 113 win 32120 <nop,nop,timestamp 19079 19775> (DF) 920325328.748013 0:a0:cc:39:2d:af 0:a0:cc:39:1b:4c ip 67: n027.listen > n028.5002: P 326:327(1) ack 113 win 32120 <nop,nop,timestamp 19079 19775> (DF)
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