Re: [tcpm] SYN in SYN_RCVD state

On Sun, Oct 21, 2007 at 04:25:25AM -0700, Vishal Study wrote:
> > Vishal Study ha scritto:
> > > Consider the following scenario:
> > >
> > > 1. TCP client sends SYN to server; server goes to SYN_SENT state
> > >
> > > 2. server responds with SYN+ACK;  server goes to SYN_RCVD state
> > > but SYN+ACK sent to client is lost somewhere in the network.
> > >
> > > 3. client re-sends SYN on its timeout (couple of seconds later) to server
> > >
> > > What should be the server behavior? Should it retransmit SYN+ACK or
> > > should it send a RST?
> > >
> But RFC 793, pg 71 seem to say that the server should send out a RST
> if SYN is rx in SYN-RCVD state (assuming SYN seq number is within the
> window, which is true in the example I had mentioned).
> 
> Any thoughts on this?

I think that because RCV.NEXT was set to SEG.SEQ+1 when the "server"
entered SYN-RECEIVED state (as documented on page 66 of 793) the resent
SYN is outside the window and will be acked.  The "server's" SYN+ACK
will be resent if it times out.

-- 
Ted Faber
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