Subject: Washington Issue 6 - Extensions

From: Brian Rosen <[email-masked]>
Date: Mon, 15 Nov 1999 11:40:01 -0500

A number of issues were raised in the Washington meeting that
were "send to the list".  This is one of these issues, with the
problem and my suggested fix.

Problem:
The protocol has a number of places where extensions are
permitted by prefixing a token with "X-".  The current list
of places where extension is permitted is:
        MuxType in MuxDescriptor
        ModemType in ModemDescriptor
        Action Parameter in EventsDescriptor (but this may change)
        ServiceChangeMethod
        ServiceChange (add a new parameter)

Proposed Solution

Allow X- to allow an extension descriptor, as well as an
extension command.

I note we could also consider X- in Audit (a new kind of audit)
This would leave Media/Stream/Local/Remote as the only non
extendable descriptors (but TerminationState and Local Control,
which are components of these) are extendable via packages.

Brian

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From: Abdallah Rayhan <[email-masked]>
Date: Mon, 15 Nov 1999 15:02:24 -0500

Brian,

Extending parameters and descriptors make sense, even allowing
X-Descriptor for things that we might add later. However extending
commands is something that we should not do at all. A lot of effort has
been put to define the structure of megaco. Allowing new command
extensions would change the spirit and body of the protocol. If someone
wants to add new commands, then call it whatever you want but not
megaco.

Abdallah

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From: Christian Groves <[email-masked]>
Date: Tue, 16 Nov 1999 14:16:59 +0100

G'Day all,

I think that X- should not be supported in the protocol at all. If the
X- is used for testing new features then I assume these will not be used
in live networks and on experimental networks. Opening up the protocol
which you'll have to do whether X- is included or not is not an issue in
this experimental case.

New descriptors and commands should only be added in a new version of
the Megaco/H.248 protocol. Having proprietory X- extensions is not
Megaco. We'll end up in the situation where we have different flavours
of H248/Megaco which isn't desirable.

Cheers, Christian