Paul,

Thanks for your comment.

One confirmation.

...

Why are there issues in Fast Connect only?

With regular H.245 capability exchange and the use of OLCs, both sides will know the actual capabilities. Version 2 devices should then only send an OLC with a version that it knows the remote side can accept.

The problem has to do with sending a Fast Connect proposal (channel proposal) for T.38v2 (2002 syntax) to a version 0 device (1998) syntax and that device accepting the proposal and, subsequently, sending 2002-encoded IFP packets. The version 0 device cannot decode the IFP packets.

I understand it.

My question is, In Figure D.8 - D.11 in H.323 Annex D, does the same issue happen?

I think so.

In short, there is a potential for sending the wrong ASN.1 PER encoded messages.

Yes.

Regards, -- Hiroshi Tamura