Hi Frank,
H.248 appears in H.323 in three contexts 1) Credit card tones and announcements from Gk. 2) Annex L 3) Endpoints reporting their H248 PackageDescriptors to Gks in RRQ.
Although Annex L defined H.248 messages as Octet Strings, the other two imported H.248 syntax. There was a proposal in last SG16 meeting to change them to Octet Strings as well for the reasons- Those who were not willing to support H.248 functionality, would not have to import the H.248 syntax (For Signals and Pacakges for (1) and (3) above).
Also these octet strings were proposed to contain PER encoded H.248. (Text in addition for Annex L) to allow single encoding and decoding scheme, namely PER for H.323.
I believe, it is due to lightweight reasons (as you pointed out), that ServiceControlSession also contained H.248 Signals which could as well be transported using Annex L.
regards Manoj.
-----Original Message----- From: Frank Derks [mailto:frank.derks@PHILIPS.COM] Sent: Wednesday, May 30, 2001 12:24 AM To: ITU-SG16@mailbag.cps.INTEL.COM Subject: Why use two different "H.248 mechanisms" in H.323?
There are two ways in which H.248 can be used in H.323. One way is through Annex L Stimulus Signalling, which basically "tunnels" H.248 messages in H.225.0 Call Signalling Messages (although Annex L only speaks about "commands", I assume that "replies" may also be carried).
Another way of carrying H.248 is through the serviceControlSession element, which can be transported in most of the Call Signalling messages and some of the RAS messages. Using this mechanism, however, introduces a limitation in that only H.248 _signals_ may be transported.
If the idea behind the second approach is to have a "lightweight" way of using only some of H.248's functionality, then I wonder why H.248 _events_ were not included as part of the solution.
Regards,
Frank
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