Subject: Question about Solaris' way to compute RTO

From: Ragon Philippe <[email-masked]>
Date: Tue, 06 Nov 2001 20:46:29 +0100

I am involved into TCP applications testing over a wireless network.
I am stumbling over a 'systematic' problem related to Solaris 2.6 when it 
is used as a server :  I am regurlarly getting spurrious retransmissions 
(Ack arriving a few tens of ms after the server has decided to retransmit) 
with a huge performance loss as a consequence.

This problem does not occur with Solaris 8, Linux or Windows NT 4 servers.
I have checked with traces and the use of Solaris' command 'ndd /dev/tcp 
tcp_status' that :
- Solaris 2.6 is taking one RTT sample per packet
- Solaris 2.6 seems to be RFC 2988 compliant in its computation of RTO from 
its RTT measurements (alpha =1/8, beta = 1/4, K= 4 and clock granularity 
is100 ms)

I am eager to get any information on how :
- Solaris 2.6 is actually computing RTO and whether there are some 
parameters to tune this computation.
- how Solaris 8 is different from Solaris 2.6 from this point of view

Any help will be appreciated.
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Philippe Ragon / Tour Atlas / 10, villa d'Este/ 75013 Paris/ FRANCE
Telephone & Fax    : (33) 01 45 70 79 53
E-mail                   :   [email-masked]
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