[Serusers] ACC's ACK

Greg Fausak greg at august.net
Wed Feb 26 19:31:40 CET 2003


> 
> 
> At 05:18 PM 2/26/2003, Greg Fausak wrote:
> >I realize the accounting logging of ACK is only an attempt, but ...
> >
> >It does seem fairly important in determining when the actual
> >call started.
> 
> I'm little a bit reluctant to go into the ACK-accounting bussiness
> for reasons of how SIP is built.
> 
> In my opinon, one can consider a call to begin when 200 is sent out.

I agree.  Wouldn't it make sense to write an accounting record for
the OK200 message, and skip the ACK accounting, since it really
doesn't mean anything.  I mean, the wrong ACK is being accounted anyway.

---greg


> The problem with 200/ACK is that it is not a part of transaction.
> Why does it matter? Well, that's because a proxy server cannot
> recognize (even if ACK is forced to visit it through proxy
> through record-routing) whether an ACK belongs to an INVITE or
> not. It might have take a different upstream path and have thus
> different transaction identifier in Via/branch. Ambiguities
> would even exist if we tried dialog matching instead -- you
> may have forwarding resulting in spirals and then you would not
> really know to which of the dialogs the ACK belongs.
> 
> If you were really so much interested in it, we could introduce 
> some "transaction-matching parameter" to record-routes and try to
> match them. That's doable, though not right immediatelly.
> 
> -Jiri
> 
> [...]
> >I note the ACK times are all the same as the INVITE times.
> >Isn't the wrong ACK being recorded?  Is this a problem with
> >my .cfg?  A much more useful ACK would be the second one (when the
> >far end ACKs after the 180 Ringing and 200 OK messages.
> >
> >A typical call, from UA perspective:
> >
> >INVITE             ->
> >401 unauth..       <-
> >ACK                ->  (evidently, the one being accounted)
> 
> One can match negative ACKs but they maintain only a transport
> role -- I would not wait for it, with 401, the transaction is
> complete.
> 
> >INVITE (with cred) ->
> >100 Trying         <-
> >180 Ringing        <-
> >200 OK             <-
> >ACK                -> (the ACK that SHOULD be accounted, IMHO)
> 
> All is already decided when 200 is sent. Also, 200-ACKs are not
> easy to account, see above.
> 
> -Jiri 
> 




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