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Date:      Wed, 14 Jul 1999 14:05:25 -0700
From:      David Greenman <dg@root.com>
To:        Mike Smith <mike@smith.net.au>
Cc:        "John W. DeBoskey" <jwd@unx.sas.com>, freebsd-hackers@FreeBSD.ORG
Subject:   Re: tcp windowsize query? 
Message-ID:  <199907142105.OAA21468@implode.root.com>
In-Reply-To: Your message of "Wed, 14 Jul 1999 13:21:55 PDT." <199907142021.NAA01388@dingo.cdrom.com> 

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>>    delayed ack sounds interesting....
>
>Turning that off disables TCP slow-start.  It's a huge performance 
>booster for things like SMB service, where you have lots of short-lived 
>TCP connections on a local net.

   Uh, that's not what it does. Slow start is a behavior where the sender
opens the window slowly - starting with one segment for the window and
adding one more segment for each ack that comes back successfully. What the
above option does is disable delayed acks on the receiver, thus reducing the
round-trip time and increasing the speed of transaction style (small) TCP
sends. Actually the real purpose of it is to eliminate the internal overhead
that is normally imposed by the delayed ack timers, which can become
substantial on large systems like wcarchive. That it has other beneficial
side effects is almost accidental. :-)

-DG

David Greenman
Co-founder/Principal Architect, The FreeBSD Project - http://www.freebsd.org
Creator of high-performance Internet servers - http://www.terasolutions.com


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