Strange TCP-networking problems with Mac OS X 10.4 and Solaris 10
Strange TCP-networking problems with Mac OS X 10.4 and Solaris 10
- Subject: Strange TCP-networking problems with Mac OS X 10.4 and Solaris 10
- From: Heiko <email@hidden>
- Date: Thu, 12 Oct 2006 12:37:49 +0200
Hello,
I have a strange problem with TCP-communications, which is not
directly related to developing software. I hope you forgive me, and
can help me solve the issue, or point out OS parameters to workaround
the problem (or even tune the OS' TCP-Stack to work properly :-) ).
Short description: The Mac is a OS X.4 client with 100MBit network
connection (172.27.2.127), and the Sun is Solaris 10 AFP-Server
(Ethershare) with a 1000MBit network connection (172.27.1.40). The
problem only occurs while reading data from the Sun.
The Mac acknoledges data packets from the Sun very lazily, meaning
the Sun sends up to 6 packets, the Mac ack's just one. This way the
retransmission queue of the sun fills up with unacknoledged packets,
forcing the Sun to throttle down.
Some packets later, the Sun only sends new packets if prior packets
are acknoledged.
Now the Mac sends acks for more then one packet at a time (good
thing), but delays the send about 500microseconds...this gets worse,
until the delay is about 200ms (milliseconds!). As you can imagine,
the throughput is near zero.
The whole description with TCP-dumps is available here:
http://www.wurst-wasser.net/Wurst-Wasser.net/Wiki-Uploads/
BerlinTCPPerformanceProblem.pdf (10MB, good quality, better viewed in
Preview than in Safari)
Has anyone heard of such a problem before?
It would be great if someone could point out possible causes,
workarounds or even solutions.
Thank you!
-
Heiko
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