Subject: RE: [Megaco] Query about local control descriptor properties

From: "Tom-PT Taylor"<[email-masked]>
Date: Tue, 29 Jan 2002 11:00:40 -0500

This seems like a practical solution for LocalControl, but if we accept it,
we have to change the text of the Recommendation, meaning that it only holds
for H.248v2.  I'll note that we have a real problem of interoperability
here.  My previous note on the interpretation of this clause presented three
alternatives, and I got E-mails (one private) in support of all three of
them.  

I don't quite see Wayne's point on the Signals and Events descriptors.  In
both cases, the semantics of the situation require the repetition of all of
the signals/events you want to keep.  You also need at least the KeepActive
parameter where it applies to signals.  Are you saying, Wayne, that once an
event or signal is specified, then if it is retained in replacement
descriptors it is unnecessary to respecify all the parameters that went
along with it the first time?  I could live with that as an IG
clarification.  Other views?

-----Original Message-----
From: Chuong N. Nguyen [mailto:[email-masked]]
Sent: Tuesday, January 29, 2002 9:40 AM
To: [email-masked]'
Subject: Re: [Megaco] Query about local control descriptor properties

I agreed w/Wayne on option d which is how it was before v1 came out. 
Then we got into these Reserve parameters discussion and changes 
but I didn't think the statement should apply to Property parameters. 
  
Wayne Cutler wrote: 
  
What about an option d) that would regard an absent Property as meaning 
"leave the existing value unchanged"? 
As a related question, I note that section 7.1.7 (Local Control Desc.)of 
the spec. 
says that:- 
"A new setting of the LocalControl Descriptor completely replaces the 
previous setting of that descriptor in the MG.  Thus to retain information 
from 
the previous setting the MGC must include that information in the new 
setting". 
Similar statements are made for the Events & Signals Descriptors. 
In the case where an MG supports a number of packages, this text is saying 
that an MGC 
wishing to change data/attributes in one Package in a given Descriptor is 
forced to repeat any previous data against any other Packages. This is 
perverse. So, can this text be qualified to say that the new Descriptor 
replaces only data relating to Packages present in the new/latest message? 
Regards, 
Wayne. 
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---

From: Christian Groves <[email-masked]>
Date: Wed, 30 Jan 2002 14:00:28 +1100

G'Day Tom,

I don't think we can accept the exception for property parameters this
would be a big problem for interoperabilty between v1 and v2. Having to
repeat the entire descriptor when we want to change one item I agree is
not nice but the list came to a consensus that it was the way it would
work.

The other problem arises is that if  "leave a property absent from a
descriptor" means keep the property as is, how do you then describe how
to delete a single property from a descriptor?

Regards, christian

---

From: Christian Groves <[email-masked]>
Date: Wed, 30 Jan 2002 14:00:28 +1100

G'Day Tom,

Regards, christian

---

From: "Chuong N. Nguyen" <[email-masked]>
Date: Wed, 30 Jan 2002 19:25:29 -0600

If we just limit the discussion to LocalControlDescriptor and not thing about or
descriptor
in general or specifically Signal/Event Descriptor, the phrase

"how to delete a single property from descriptor"

What does it mean to delete a single property from LocalControlDescriptor?

From the Standard

7.1.7 LocalControl Descriptor

   The LocalControl Descriptor contains the Mode property, the
   ReserveGroup and ReserveValue properties and properties of a
   termination (defined in Packages) that are stream specific, and are
   of interest between the MG and the MGC.  Values of properties may be
   underspecified as in section 7.1.1.

LocalControlDescriptor always contains these properties which are always part
of a termination.
The only thing that changes is the value of the property or for properties that
are dependent
on what packages are supported by a termination.

For properties that can be added or deleted because of what packages are
supported by
a termination, MGC can't tell MG what package it needs to add or delete.
So I am not sure what deleting property really mean here?

Christian/Tom,
Do you happen to know the thread that this change was discussed and consensus was

reached?

Thanks
Chuong

---

From: "Chuong N. Nguyen" <[email-masked]>
Date: Wed, 30 Jan 2002 19:25:29 -0600

From the Standard

Christian/Tom,

reached?

Thanks
Chuong