Re: [Discussion] SEQ.ACK info

[Richard Carlson <rcarlson@xxxxxxxxxxxxx>]

Hi Matt;

Yes SEG.ACK (fat fingers typo).  Thanks for the explanation.

I'm trying to figure out a way to tell when a ACK fills in a whole in 
the receive buffer.  I'll look at SND.UNA to see if it makes these jumps.

Rich
At 11:32 AM 8/28/2007, Matt Mathis wrote:
> I assume you mean SEG.ACK.  It is not persistent.  It does not exist, except
> while processing an incoming segment.  Web100 is locked out while processing a
> segment so, no it can't be observed.
>
> Unless there are reordered ACKs, SND.UNA is the same as the last received
> SEG.ACK.  If there is reordering, SEG.ACK will sometimes be less than SND.UNA,
> and TCP knows that the segment is late.
>
> Does this make sense?  I think you want SND.UNA.  BTW outside of recovery,
> SND.NXT-SND.UNA is a direct measure of the TCP window size.
>
> (John, it would have been cool to count and sum negative SEG.ACK-SND.UNA
> This would yield a strong measure of return path reordering.  Oh well).
>
> Thanks,
> --MM--
> -------------------------------------------
> Matt Mathis      http://www.psc.edu/~mathis
> Work:412.268.3319    Home/Cell:412.654.7529
> -------------------------------------------
> Evil is defined by mortals who think they know
> "The Truth" and use force to apply it to others.
>
> On Mon, 27 Aug 2007, Richard Carlson wrote:
>
> > John;
> >
> > I'm wondering why the SEQ.ACK is not exposed as a Web100
> > variable?  Should it be?
> >
> > Rich
> >
> >
> > ------------------------------------
> >
> >
> >
> > Richard A. Carlson                              e-mail: 
> RCarlson@xxxxxxxxxxxxx
> > Network Engineer                                phone:  (734) 352-7043
> > Internet2                                       fax:    (734) 913-4255
> > 1000 Oakbrook Dr; Suite 300
> > Ann Arbor,  MI  48104
> >
> >
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------------------------------------



Richard A. Carlson                              e-mail: RCarlson@xxxxxxxxxxxxx
Network Engineer                                phone:  (734) 352-7043
Internet2                                       fax:    (734) 913-4255
1000 Oakbrook Dr; Suite 300
Ann Arbor,  MI  48104 


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