svn commit: r232345 - user/andre/tcp_workqueue/sys/netinet

Andre Oppermann andre at
Thu Mar 1 18:20:16 UTC 2012

On 01.03.2012 18:05, Maxim Konovalov wrote:
>>>> Author: andre
>>>> Date: Thu Mar  1 16:18:39 2012
>>>> New Revision: 232345
>>>> URL:
>>>> Log:
>>>>   Increase the initial CWND to 10 segments as defined in IETF TCPM
>>>>   draft-ietf-tcpm-initcwnd-03 discussing why the higher initial window
>>>>   improves the overall performance of many web services without risking
>>>>   congestion collapse.
>>>>   As long as it remains a draft it is not enabled by default and placed
>>>>   under a sysctl marking it clearly as experimental:
>>>>    net.inet.tcp.exprimental.initcwnd10
>>>>   Linux as of kernel 3.0 has enabled it by default.
>>> Wouldn't it be better to just let user to specify icwnd size?
>> In SCTP we have a sysctl which gives the IW in MSS...
> Yes, that's why I'm asking mainly.

I'm a bit wary of abuse by non-clueful enough people who think bigger
must be better.  There was a recent discussion to this effect on TCPM.
Also there were reports of congestion collapse in some networks, due
to some other issues.  I've even seen botched windows servers that
respond with an icwnd of 64K.

Hence I'd rather not have it open to anyone to fumble with this important
parameter.  The (negative) effects are not directly visible to a normal


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