Re: Unacceptable ACK in SYN_RCVD state handling

Bob Braden <braden@ISI.EDU> Mon, 08 April 2002 22:13 UTC

From: Bob Braden <braden@ISI.EDU>
Date: Mon, 8 Apr 2002 22:13:38 GMT
Message-Id: <200204082213.WAA05024@gra.isi.edu>
To: braden@ISI.EDU, mbashyam@cisco.com
Subject: Re: Unacceptable ACK in SYN_RCVD state handling
Cc: tcp-impl@grc.nasa.gov
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  *> 
  *> No, the scenario that applies is described on page 68 (sequence number check),

Yes, sorry, I misinterpreted what you were asking (ACK field as opposed
to sequence field of ACK segment (But the man DID say "receive window"...
mumble).

  *> 
  *> The point u mentioned above is the conflict i am having as well, it seems to me
  *> that retransmitting
  *> a SYN-ACK seems the right thing to do. But the BSD stack doesn't seem to be
  *> doing that.

I thought you said earlier that the BSD DOES retransmit the SYN.  In
any case, I would agree that the text of RFC 793 seems to say
otherwise.  This particular test is one that has caused a great deal of
confusion over the years.  From the underlying logic of TCP,  I believe
that retransmitting the SYN is OK.  So it seems you can choose either
interpretation you want (unless there is some  subtle security
implication.)

Bob Braden

  *> 
  *> Murali
  *> 
  *> 
  *> 
  *> 
  *> >
  *> >
  *> > Bob Braden
  *>