Relationship of H.323 and H.245 versions

Paul Long Plong at SMITHMICRO.COM
Fri Jan 29 15:09:02 EST 1999


You be the judge:

Summary/H.323v2: "Products claiming compliance with Version 2 of H.323 shall
comply with all of the mandatory requirements of this document, H.323 (1998),
which references H.225.0 (1998) and H.245 (1998). Version 2 products can be
identified by H.225.0 messages containing a protocolIdentifier = {itu-t (0)
recommendation (0) h (8) 2250 version (0) 2} and H.225.0 messages containing a
protocolIdentifier = {itu-t (0) recommendation (0) h (8) 245 version (0) 3}."

Assuming this text is normative, H.323v2 uses H.225.0v2 and H.245v3. Period.

IMO, we will be asking for big trouble if we at some point decide that one can
mix and match versions and even use subsets or supersets of a particular
version. Whatever interoperability problems we have now will be magnified many
times over if we head down that slippery slope.

Paul Long
Smith Micro Software, Inc.

        -----Original Message-----
        From:   Gary A. Thom [SMTP:gthom at DELTA-INFO.COM]
        Sent:   Friday, January 29, 1999 1:37 PM
        To:     ITU-SG16 at MAILBAG.INTEL.COM
        Subject:        Re: Relationship of H.323 and H.245 versions

        One more question????

        > Dave,
        > Sorry, but I won't be in Monterey.
        > I agree with what you say, except that I would go further and state
that there
        > is always a one-to-one mapping between H.225.0 and H.245
        > via H.323. For example,
        >     H.225.0v1 => H.323v1 => H.245v2 and H.245v2 => H.323v1 =>
        >     H.225.0v2 => H.323v2 => H.245v3 and H.245v3 => H.323v2 =>
        > This is already implied by the Summary section of H.323 starting
with version
        > 2. I think it's clear, but you could add clarification text if you
like. IOW,
        > for example, an EP cannot use H.245v2 and H.225.0v2 in the same

        But can H.225.0 V2 (H.323 V2) and H.245V4 (or 5) be used in the same


        Name   : Gary A. Thom
        Company: Delta Information Systems, Inc.
        Address: 300 Welsh Rd., Bldg 3
                 Horsham, PA 19044 USA
        Phone  : +1-215-657-5270         Fax : +1-215-657-5273
        E-mail : gthom at

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