Adjusting TCP windows on production systems?

Wed Oct 1 07:24:39 UTC 2003

Steve Francis wrote:

>
> Just as a head up - this sort of below should not be done on things 
> like web servers that support lots of concurrent connections - you'll 
> eat all your memory for sockets.
>
Unless you have something like FreeBSD´s auto-tuning inflight window 
stuff  which
would allow large windows to be allocated only when the delay*bandwidth 
product
justifies it.

Pete

> Marshall Eubanks wrote:
>
>> On Tue, 30 Sep 2003 15:44:03 -0400
>> "Temkin, David" <temkin at sig.com> wrote:
>>  
>>
>>> Is there anyone in a production environment who, as part of their 
>>> system
>>> build process, adjusts the TCP receive window/MSS/etc. on production
>>> systems?
>>>
>>>   
>>
> As a concrete data point:
> the tuning below on Solaris 9 increased the TCP data transfer rates from
> SJC to NYC by a factor of 10:
> (i.e. from 2 to about 20Mbps with ftp; 1 to 11Mbps with scp.)
>
> ndd -set /dev/tcp tcp_recv_hiwat 400000
> ndd -set /dev/tcp tcp_xmit_hiwat 400000
> ndd -set /dev/tcp tcp_wscale_always 1
> ndd -set /dev/tcp tcp_max_buf 10485760
>
>
>