Question regd timestamp option

[Miku Jha]

--- Chuck Swiger <cswiger at mac.com> wrote:

> 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.
> 

The first time both ends negotiate and accept
timestamp
option.
The situation is that if the client crashes , the
server eventually sends a RST (10.39.53)
Following this RST, the client comes back in lets say
around 2-3 minutes.
Now when the client sends a SYN(10.42.23), there is no
timestamp option.

Is there some requirement that RST needs to be ACKED
or RST flag will remain set for some time window
within which if SYN is send, timestamp option will not
be set.

Thanks in advance for your help.




> -Chuck
> 
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