Sasha,

The fact that H.225.0 says a device shall send a Status message for an unknown message, yet leaves the Cause code unspecified, is certainly an issue we should close on.  My suggestion would be to use 97: “Message type non-existent or not

Implemented.”

I think an “unknown message” would be one that is not currently defined today in H.225.0.  If the message is syntactically invalid, then I believe that is a protocol error.  In that case, either 100 or 111 would be good choices depending on whether it is just an invalid IE or something that is impossible to decode.

Those are fairly minor changes, though the impact might be significant.  However, your problem description suggests you are looking for a broader statement.  Do you have a specific proposal in mind, either a new paragraph or section on error handling or a reference to Q.931?

Paul

From: itu-sg16-bounces@lists.packetizer.com [mailto:itu-sg16-bounces@lists.packetizer.com] On Behalf Of Sasha Ruditsky
Sent: Wednesday, September 30, 2009 6:01 PM
To: itu-sg16@lists.packetizer.com
Subject: [itu-sg16] AVD-3813 Handling Of Error Conditions in H.323

Q2 Experts,

The conclusion for the discussion of the AVD-3813 during the last SG16 meeting’s was to ask the experts opinion through the mailing list.

My apology for the short notice. I hope that we still have time before the next meeting for people to understand the problem and express their opinions.

The problem discussed in AVD 3813 is more or less as follows:

“

H.225.0 gives very little attention to the specification of processing of the H.225.0 Call Signaling messages errors. The only place dedicated to this subject is Clause 7.1 of H.225.0. 

On the other hand, ITU-T Recommendation Q.931 on which H.225.0 messages are based provides quite detailed information on the same subject. While H.225.0 states that Implementations shall follow ITU-T Rec. Q.931 as specified in H.225.0, there is a lot of confusion surrounding the cases which H.225.0 does not cover and Q.931 does.

In addition, ETSI TS 101 804 – 2 defines Conformance Test Specification for ITU-T H.225.0. This test specification apparently based on Q.931 procedures, not on the corresponding H.225.0 ones. More than this, in many cases ETSI TS 101 804 – 2 requests behavior which claims to be based on Q.931, however is not defined neither in Q.931, nor H.225.0.

“

Apparently “H.323 conformant” not always means “ETSI TS 101 804 – 2 conformant” and I believe we need to find some solution to at least make this particular point clear.

I’m going to resubmit AVD-3813.

It would be great to be able to get some ideas from the group into the resubmitted document.

Thank you,

Sasha