Re: question about TCPAgent reset()

[Lloyd Wood <l.wood@eim.surrey.ac.uk>]

On Wed, 26 Jan 2000, Lloyd Wood wrote:

> On Tue, 25 Jan 2000, Guo, Liang wrote:
> 
> > However, since the ACK packet (acking packet 100) for the previous
> > connection is still in flight, so as soon as $stcp starts, it
> > will get this ACK packet and end the session, but it hasn't
> > sent any packet out!
> 
> Surely the sequence number for that ack packet should (in most cases)
> be beyond the right window of the new $stcp session, so $stcp should
                     ^^ edge of the 

there. that makes more sense.

L.

> simply ignore it?
> 
> Looking in:
> 
> void TcpAgent::newack(Packet* pkt)
> [..]
> hdr_tcp *tcph = hdr_tcp::access(pkt);
> [..]
>         last_ack_ = tcph->seqno();
>         prev_highest_ack_ = highest_ack_ ;
>         highest_ack_ = last_ack_;
> 
>         if (t_seqno_ < last_ack_ + 1)
>                 t_seqno_ = last_ack_ + 1;
> 
> some sort of (untested conceptual suggestion; off the top of my head
> from a quick browse) sanity check would be sensible here:
> 
> 	last_ack_ = tcph->seqno();
> 	if (last_ack_ > maxseq_)
> 		break; /* ack isn't acking anything we sent */
> 	/* probably other ways to do it:
> 	   Got an int - TracedInt > TracedDouble here. ugh.
> 	   if (last_ack_ - highest_ack_ > cwnd_)
> 		   break;
> 	*/
> 	prev_highest_ack_ = highest_ack_ ;
>         highest_ack_ = last_ack_;
> 
> etc. This isn't quite Savage-et-al style defensiveness; just trying to
> turn:
> 
> /*
>  * Process a packet that acks previously unacknowleged data.
>  */
> 
> into
> 
> /*
>  * Process a packet that acks previously unacknowleged data
>  * that we think we sent.
>  */
> 
> cheers,
> 
> L.
> 
> thinks tcp really should distinguish pkts for different 'conceptual'
> tcp connections from the same 'physical' tcp agent object anyway.
> 
> <L.Wood@surrey.ac.uk>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>
> 
> 
> 
> 
> 
> 

<L.Wood@surrey.ac.uk>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>