[Megaco] Re: Event descriptor handling for static logic inter

Kevin Boyle kboyle at NORTELNETWORKS.COM
Thu Oct 2 09:37:04 EDT 2003


Thomas,

The function you want already exists in the package.  Each one of the line
signalling events in both ICAS and BCAS have descriptions that contain the
following:

The event is reported by the MG if either the timed transition to this line
signal is detected or the line signal already exists.

This means that the strict=state behavior is already inherent in these
events.  I see no problem with this, and no need for a change to these
packages.

Kevin

-----Original Message-----
From: Thomas Voith [mailto:Thomas.Voith at alcatel.de] 
Sent: Thursday, October 02, 2003 4:00 AM
To: Christian Groves
Cc: megaco at ietf.org; ITU-SG16 at external.cisco.com
Subject: Re: [Megaco] Re: Event descriptor handling for static logic
interfaces like CAS


Hello Christian

I want both, 
- strict parameter for CAS Line signals and in future for all
'static'signalling interfaces.
- optionally a default strict="state" to shorten the Events Descriptor

In my opinion, this should be used for all 'static' signalling interfaces.
With 'static' I mean that this interface has always a state, when MG
receives an EventsDescriptor from MGC. For synchronizing the states from MGC
with MG the strict mechanism is very useful. Doing the same with
EventBuffer, Embedded Descriptor 
is much more complex and increases extreme with the number of possible
states on the interface.

Note: This 'strict' parameter is just used by MG to determine, whether a
Notify
      for the existing state on the interface has to be sent or not.
      Further on normal event handling applies.
      This approach has the advantage, that EventBuffer and Embedded can
still be used
      in addition.
 
For all 'dynamic' events like pulses, DTMF, SPCM, normal event handling
applies.

Best regards

Thomas



Christian Groves wrote:
> 
> Hello Thomas,
> 
> Are you wanting a general purpose mechanism such as the off-hook one 
> or do you just want the default stated for H.248.26 and H.246.ICASC?
> 
> Kevin Boyle is the editor of these he may have some opinion on this.
> 
> Its always possible to make amendments to existing recommendations. 
> Bring in a contribution for consideration to SG16 or propose a 
> detailed solution on the Megaco list for experts to review. If they 
> are agreeable then the change will be added.
> 
> Regards, Christian
> 
> Thomas Voith wrote:
> 
> > Dear list-members,
> >
> > H.248.26 and in H.248.ICAS I miss a feature, which has been used 
> > already for On-Hook, Off-Hook  the 'strict' parameter.
> >
> > All interfaces, which have static states, should implement such a 
> > mechanism.
> >
> > The problem is that the EventsDescriptor EventBufferDescriptor or an 
> > embedded EventsDescriptor may discard events, if the newly received 
> > or replacing Event Descriptor does not match the event.
> >
> > In the Megaco Secnarios, always just the good case is shown.
> >
> > e.g. a static interface with 4 logical incoming events ( 
> > S1,S2,S3,S4) would then set the EventsDescripror like:
> >
> > MGC guess the MG is in state i1, no Notify will be sent by MG, when 
> > state of interface is still i1.
> >
> > Events { 
> > S1{strict="exact"},S2{strict="state"},S3{strict="state"},S4{strict="
> > state"} }
> >
> > ( Note: in case "state" is the default, then EventsDescriptor could 
> > be shorter)
> >
> > The events descriptor remains active, after Notification is sent. 
> > The strict parameter avoids unnecessary Notifications for the 
> > already by MGC known state.
> >
> > This mechanism would be very simple and avoids lost of any events, 
> > which is strong required for signalling interfaces on MG transferred 
> > via H.248 to an MGC.
> >
> >
> > For a better illustration I have attached a Excel-File containing a 
> > simple scenario.
> >
> > So my question/proposal is:
> >
> > - Is it possible to extend the existing static state interfacepackages
like H.248.26 with this
> >   strict feature?
> > - If not, can I get this functionality otherwise ?
> >
> > Kind regards
> >
> > Thomas Voith
> >
> 
> _______________________________________________
> Megaco mailing list
> Megaco at ietf.org
> https://www1.ietf.org/mailman/listinfo/megaco

-- 
_______________________________________________________________
          _
          V                    | Thomas Voith                   
  +---------------+            | Dept. VS/EAC2 [Systems]      
  | A L C A T E L |            | FL/2/50
  +---------------+            | 
                               | Tel:   +49 711 821-40293
                               | Alcanet:       259-40293
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_______________________________________________________________

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