Date: Fri, 12 Aug 2005 15:52:28 -0400 From: Chuck Swiger <cswiger@mac.com> To: jha miku <jha0147@yahoo.com> Cc: freebsd-net@freebsd.org Subject: Re: Question regd timestamp option Message-ID: <42FCFDFC.2020903@mac.com> In-Reply-To: <20050812020814.30073.qmail@web34105.mail.mud.yahoo.com> References: <20050812020814.30073.qmail@web34105.mail.mud.yahoo.com>
next in thread | previous in thread | raw e-mail | index | archive | help
jha miku wrote: > In case of active open, the SYN segments always have > timestamp enabled, since the RFC flg is set. But, > Currently, I am seeing some SYN segments without > timestamp option. FreeBSD (and OS X, and other things using a BSD network stack) will generate initial TCP SYN packets containing the "MNWNNT" TCP options, at least by default in the absense of other information or settings. > The only condition that I am aware of when timestamp > is disabled, is on sending the 3rd SYN in retransmit code > when the timestamp gets disabled. > looking at the tcpdump, it is unclear why the SYNs are > sent during active open without timestamp option. The TCP stack seems to remember some information about which TCP options a remote host is willing to accept. If the remote system didn't accept a timestamp the first time (perhaps it's talking to an old windows box which does "MNNS"), there is no point in sending that option out the next time you open a new connection to the same system. -- -Chuck
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?42FCFDFC.2020903>