Subject: [Megaco] Response to a message with no command?

From: "Kevin Boyle" <[email-masked]>
Date: Mon, 8 Oct 2001 21:53:30 -0400

Megaco provides the ability to signal a transaction without a command in
certain instances, namely when signalling a "context property" to the MG.
In v1, these would be Emergency, Priority, and Topology.

While looking at the ABNF constructs for these, and the potential responses,
a hole/inconsistency is revealed.  Assume the MG has received the following
message:

!/1 [1.2.3.4]:2944 T=25{C=12{TP{term1,term2,isolate}}}

What, then, does the response look like?  If we go with something similar to
command responses, where the internal details of the command are not echoed,
one might choose a construct like this:

!/1 [1.2.3.4]:2944 P=25{C=12{}}

This response, however, is illegal.  A legal response has the Topology
descriptor repeated:

!/1 [1.2.3.4]:2944 P=25{C=12{TP{term1,term2,isolate}}}

However, this echoes back the internals of the command, which is not
consistent with other response constructs.

So, the question is, what should the response be?  As you can probably tell,
I lean toward the former, but it would be good to get a list consensus about
what should be returned to the MGC for these transactions (and, if need be,
a quick change to the ABNF).

Kevin