Paul,
I am wondering whether you are missing the point here. Jim and Mark have stated clearly how things are supposed to work:
- H.225.0 signaling carries a protocol identifier in the mandatory part of all relevant PDUs (RAS as well as call signaling channel)
- H.323/H.225.0 describe in each revesion explicitly which version of H.245 to use and which features of this to implement. (And, for clarity, this is *NOT* done in the ASN.1, but in the references section of the document!)
Hence you can deduce the H.245 version from the H.225.0 version number which is determined IN-BAND in the first PDU exchange between any two H.323 systems. And, of course, you cannot add anything to H.245 without this being appropriate reflected in the H.323/H.225.0 specification.
Also: you are talking about no H.323 version signaling? H.225.0 and H.323 go together at all times! H.225.0 defines the protocol syntax and H.323 the procedures; so there is no difference between an H.225.0 and an H.323 version number!
But you are right that we should pay attention problems that might arise from version conflicts and to clearly specify how systems are to behave if they encounter that their peer runs a lower version number.
Joerg
---------------------------------------------------------------------------- --- Joerg Ott jo@tzi.org Universitaet Bremen, Germany fax + 49 421 218-2085 TELES AG voice + 49 421 218-7000