Paul,
I don't have a particular axe to grind, but would suggest that if the change is desired it might be improved by a small tweak: Where you have useSpecifiedTransport UseSpecifiedTransport OPTIONAL replace it with useSpecifiedTransport SEQUENCE OF SpecifiedTransport OPTIONAL
Then define SpecifiedTransport as you've defined UseSpecifiedTransport. This (with suitable text) would allow a gatekeeper to specify transports in a priority order: any transport not mentioned should not be used if the SEQUENCE OF is present at all (interestingly this would mean there would actually be a difference for a change between, on the one hand, the SEQUENCE OF being present but empty and, on the other hand, the SEQUENCE OF being absent!). I appreciate that this is going to be a pretty short SEQUENCE OF at the moment, but we might as well be prepared for someone wanting to define 38 new different transport types in the future!
Regards, Chris
"Paul E. Jones" wrote:
Folks,
While talking with people recently about some features in H.323 version 3, I discovered that a couple of fields in H.225.0v3 contained an error. Specifically:
o "useAnnexECallSignalling" in RCF was supposed to be OPTIONAL o "useAnnexECallSignalling" in ACF was supposed to be OPTIONAL o "supportsAnnexECallSignalling" in LCF was supposed to be OPTIONAL
The field descriptions in the H.225.0 document correctly describe the fields as if they were OPTIONAL, which followed the agreed text from TD-23 in the Monterey meeting.
In order to correct these errors, I brought a contribution to the Osaka meeting proposing to make these three fields OPTIONAL by making a correction to the Implementers Guide. Participants at the meeting were in agreement to make these corrections, especially since H.225.0v3 has not been published yet.
However, since a change such as this will break backward compatibility anyway, the attendees decided to go beyond simply making these 3 small editorial corrections. Instead, a proposal was made to replace these fields with new fields that have an expanded scope. It will now be possible to provide "AlternateTransportAddresses" for various transports: Annex E, SCTP, or something else (currently, only Annex E is defined). In addition, the Gatekeeper, knowing what is supported, may specify which transport an endpoint shall use.
I did not object to this proposed change because it looks reasonable and, given that H.225.0v3 is so new, I did not expect it to have a serious impact. However, I have been made aware that a few vendors have or are in the process of implementing H.323v3. This means that we must solidify this ASN.1 change. The participants in Osaka agreed to the proposed changes (attached as a Word document). I believe they are reasonable, but we cannot wait until November, which is when the official vote will be made by the various world governments, to approve those fields: by that time, H.225.0v3 will be published and will have been in a Decided state for 14 months!
So, I want to hear people's comments: are all of the vendors comfortable with these changes? I do not believe that any vendor would be put in an uncomfortable position today, so I want to get agreement that we will accept these ASN.1 changes now. I do not want to see a contribution in the November meeting proposing to change these structures in any way-- hopefully what we agreed to in Osaka is acceptable to everybody and we will have no objections. If there are objections, I want to hear them now. It will be too late in November, based on what I have been hearing from various companies.
Please give your comments to me and/or post them publicly here.
Best Regards, Paul E. Jones Editor, H.323 and the H.323 Implementers Guide
Name: asn1_error.zipasn1_error.zip Type: Zip Compressed Data (application/x-zip-compressed) Encoding: base64
-- Dr Chris Purvis -- Development Manager ISDN Communications Ltd, The Stable Block, Ronans, Chavey Down Road Winkfield Row, Berkshire. RG42 6LY ENGLAND Phone: +44 1344 899 007 Fax: +44 1344 899 001
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