Event reporting (was audio call Thursday: Minutes)

Flemming Andreasen fandreas at TELCORDIA.COM
Fri Apr 9 13:57:57 EDT 1999


Well, such is the nature of glare - glare resolution is a different story
and the MGC may implement whatever policy it wants. However, if it cannot
determine the order of events, it becomes rather hard for it to achieve any
kind of policy besides randomness. Having the ability to determine order
would seem a solid design principle to me.

Going back to lockstep again, it should be noted that without the
RequestId, you will *always* have to issue a new request in response to it,
since you don't know whether the Notify was generated before or after some
request had been received - that's hardly a good solution since you are now
forced to send more messages than needed and if signals are not idempotent,
you may in fact not achieve what you desired.

I still say there are lots of good reasons for a RequestID - is anybody
opposed to including this ?


Regards

          Flemming








Brian Rosen <brosen at eng.fore.com> on 04/09/99 01:32:52 PM

To:   "'Flemming Andreasen'" <fandreas at telcordia.com>
cc:   Mailing list for parties associated with ITU-T Study Group 16
      <ITU-SG16 at mailbag.cps.intel.com> (bcc: Flemming Andreasen/Bellcore)
Subject:  RE: Event reporting (was audio call Thursday: Minutes)




Suppose the flash hook came .5 ms after the call waiting
happened.  Clearly the intention is to initiate a new call,
but your email suggests it should connect to the waiting caller.

It seems to me that whichever action the MGC takes on the
event it can do the same thing with or without the RequestID.
This is true because all the events we are discussing have
long response times relative to MG/MGC communication.
With timestamps (also a suggestion), it could do something
approximating the right thing all the time with or without
RequestIDs.

Please note, I liked RequestIDs when they were suggested.
I still like them, but I can't currently seem to defend them
very well.

Brian

> -----Original Message-----
> From: Flemming Andreasen [mailto:fandreas at telcordia.com]
> Sent: Friday, April 09, 1999 12:58 PM
> To: Mailing list for parties associated with ITU-T Study Group 16
> Cc: Flemming Andreasen; brosen at eng.fore.com
> Subject: Re: Event reporting (was audio call Thursday: Minutes)
>
>
>
>
> Consider the following example:
>
> 1. Party A is currently involved in a call with Party B. The
> active request
> for A is RA-1
> 2. Another call now arrives to A, who happens to subscribe to
> call-waiting
> as well as three-way calling.
> 3a. The MGC decides that since A subscribes to call-waiting,
> A should hear
> call-waiting tones so the MGC sends a new request RA-2 to A
> 3b. At the same time, party A could have decided to put B on
> hold and place
> another call. Party A would then generate a flash-hook which
> results in a
> Notify (N-x) message being sent to the MGC.
>
> Now, if RA-2 arrived at A prior to A generating the flash-hook, the
> call-waiting tone would have been played prior to the
> flash-hook, and the
> correct glare resolution would probably be for the incoming call to be
> connected.
>
> On the other hand, if RA-2 arrived at A after A generated the
> flash-hook,
> we should probably consider A to attempt to initiate a new
> call, and the
> correct glare resolution would probably be for the incoming
> call to get
> called-party-busy treatment, and for A to continue with the
> call attempt.
> (In this case, the call-waiting tone would actually be played
> after the
> flash-hook, so you may even have a need to specify that "the following
> request is only to be applied if there is currently no outstanding
> Notify"). Also note, that if the RA-2 message had been lost,
> there would no
> longer be a need for retransmitting it.
>
> The only way you can determine the order of events is by including the
> request id (I would not favor a transaction-id based
> approach), and I do
> believe that order matters in some cases, so you might as
> well include a
> solution, especially when it's this simple. We can probably
> come up with
> more examples if needed.
>
>
> Regards
>
>           Flemming
>
>
>
>
>
>
>
>
>
>
>
> Brian Rosen <brosen at ENG.FORE.COM> on 04/09/99 11:48:08 AM
>
> Please respond to Mailing list for parties associated with ITU-T Study
>       Group 16 <ITU-SG16 at mailbag.cps.intel.com>
>
> To:   ITU-SG16 at mailbag.cps.intel.com
> cc:    (bcc: Flemming Andreasen/Bellcore)
> Subject:  Re: Event reporting (was audio call Thursday: Minutes)
>
>
>
>
> You might be right, but I am confused.
>
> The simple case of lockstep works.  The EventDescriptor is
> set up with the event, it happens, you get notified, and you
> send a modify to rearm it.  If the event happens again before
> the rearm, you ignore it.  If it happens after, you get
> another Notify.
>
> The only way I see a problem is when you have time order
> of a Modify; you have a lockstep event "armed", you send down
> a Modify with a new EventDescriptor, and the event either
> happens before or after the Modify command is executed.
> Perhaps you think it's important to know if the event
> happened before or after the Modify, but I can't come up with
> a scenario where it matters.  If it does, then I agree, you
> need a tag that is unique to the setting of the
> EventDescriptor.
>
> I do note that you could (theoretically) report the
> transactionID of the command that set the event.  That would
> make you sent TerminationID, Event Name and TransactionID on
> the Notify.  It would solve the problem.  It might be better
> to use RequestID rather than that.
>
> Brian
>
> > -----Original Message-----
> > From: Flemming Andreasen [mailto:fandreas at telcordia.com]
> > Sent: Friday, April 09, 1999 10:13 AM
> > To: Mailing list for parties associated with ITU-T Study Group 16
> > Cc: brosen at eng.fore.com; Flemming Andreasen
> > Subject: Re: Event reporting (was audio call Thursday: Minutes)
> >
> >
> >
> >
> > There is actually a good reason for the RequestID. It
> > basically enables you
> > to determine whether a notification was issued before or after the
> > reception of a given request for the notification. As an
> > example where this
> > is important, consider what we refer to as "lockstep mode".
> > It essentially
> > states that a given request can at most generate one Notify,
> > which implies
> > that after receiving a Notify you must send down a new
> > request. Without a
> > RequestID you cannot determine whether that request has already been
> > received or not. This is not only protocol-wise important but
> > semantically
> > as well, as your new request may contain instructions to look
> > for a new set
> > of events that all of a sudden either became important to
> > know about, or
> > you no longer want to hear about. Thus we should keep the RequestID.
> >
> >
> > Regards
> >
> >           Flemming Andreasen
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > Brian Rosen <brosen at ENG.FORE.COM> on 04/09/99 08:18:46 AM
> >
> > Please respond to Mailing list for parties associated with
> ITU-T Study
> >       Group 16 <ITU-SG16 at mailbag.cps.intel.com>
> >
> > To:   ITU-SG16 at mailbag.cps.intel.com
> > cc:    (bcc: Flemming Andreasen/Bellcore)
> > Subject:  Re: Event reporting (was audio call Thursday: Minutes)
> >
> >
> >
> >
> > As the protocol is currently defined, there is
> > thus thing we called a RequestID.  You supply
> > a RequestID with the EventDescriptor, and it is
> > returned by the Notify.  A RequestID is a 32 bit
> > integer.  The syntax defines the requestID, and
> > uses it in the Notify, but does not show it in
> > the EventDescriptor.  That should be fixed, but...
> >
> > As I noted, TerminationID + EventName is logically
> > equivalent to an MGC assigned RequestID if you
> > can only have one instance of an event on a
> > termination.  Implementation seems to be simple
> > in either case at both ends.  At the MG, storing
> > the requestID is easy, but not storing is easier.
> > At the MGC, the RequestID would be a separate table,
> > but it would have to have TerminationID and
> > EventName at least implicitly, and probably
> > explicitly in it.  Searching a structure by
> > TerminationID and then EventName (or the other way
> > around) is also easy.Thinking about it overnight, if it
> > really is the same, then it would be best to
> > eliminate the RequestID artifice and use Termination
> > ID + EventName.
> >
> > At the time, I believed we thought that there were
> > circumstances where there was not uniqueness.  Right
> > now, I can't see how that can occur.
> >
> > Brian
> >
> > > -----Original Message-----
> > > From: Chip Sharp [mailto:chsharp at cisco.com]
> > > Sent: Thursday, April 08, 1999 5:46 PM
> > > To: ITU-SG16 at mailbag.cps.intel.com
> > > Subject: Re: Event reporting (was audio call Thursday: Minutes)
> > >
> > >
> > > Yes that was my understanding as well.  The TerminationID
> > > would be used to
> > > associate the event to the termination.  Thus the event
> report would
> > > contain the Termination ID and the event ID.
> > >
> > > Chip
> > >
> > > At 02:21 PM 4/8/99 -0700, Rex Coldren wrote:
> > > >Actually I believe this item was not correctly written.  I
> > > believe the
> > > >discussion was about how you associate a reported event
> to a given
> > > >Termination.  There was talk that notifications come back with a
> > > >RequestID, which must be somehow associated to a Termination.
> > > >Paul suggested using TerminationID directly.
> > > >
> > > >Christian Huitema wrote:
> > > >
> > > >> > 5) event handling
> > > >> > - currently an event is identified to the MGC with an
> > > eventId - Paul
> > > >> > Sijben suggested that it would be better to use a
> terminationId
> > > >>
> > > >> Sorry for missing the call, but let's comment on that
> > > specific point.  We
> > > >> discussed the event reporting model at length during the
> > > IETF meetings and
> > > >> in the following week, and I don't beleive that there is
> > > any advantage in
> > > >> opening the debate again.
> > > >>
> > > >> Termination Id and event names just do not belong to the
> > > same space.
> > > >>  Terminations are defined on a per MG basis; events are defined
> > > >> independently of the MG, and in many cases independently of the
> > > >> termination class.
> > > >>
> > > >> The current notifications identify both the termination on
> > > which the event
> > > >> was observed and the name of the event.  There is a lot of
> > > experience to
> > > >> show that this is a very efficient decomposition, and I
> > > don't see any
> > > >> reason whatsoever for ditching the experience in favor of
> > > an unproven
> > > >> theoretical design.
> > > >>
> > > >> --
> > > >> Christian Huitema
> > > >> ------------------------------
> > > >> Please note my new address: huitema at research.telcordia.com
> > > >> http://www.telcordia.com/
> > > >
> > > >
> > > --------------------------------------------------
> > > Chip Sharp                 voice: +1 (919) 851-2085
> > > Cisco Systems              Consulting Eng. - Telco
> > > Reality - Love it or Leave it.
> > > --------------------------------------------------
> > >
> >
> >
> >
> >
> >
> >
>
>
>
>
>
>



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