Revised version of APC-1539

Louis Christodoulides Louis_Christodoulides at INMARSAT.ORG
Fri Feb 12 06:29:42 EST 1999


Ami,

So in order to Make Things Work we probably need to do one of the following:

1.  Bind tightly for messages in fast connect, but loosely otherwise (which
may lead to implementations having to use different ASN for
encoding/decoding OLCs depending on whether or not they came in via fast
connect!).

2.  Add versioning information to OLCs (and possibly elsewhere while we're
at it).

3.  Bind versions tightly, as currently specified.

4(the controversial one).  Obselete fastStart

Regards,
Chris

> -----Original Message-----
> From: Ami Amir [mailto:amir at RADVISION.RAD.CO.IL]
> Sent: 10 February 1999 7:20
> To: ITU-SG16 at MAILBAG.INTEL.COM
> Subject: Re: Relationship of H.323 and H.245 versions
>
>
> Pete,
> It seems to me that your idea is great, and the right approach.
>
> I might be asking something out of context - but doesn't this
> neat model
> break down once we decided to do fast connect - and in essence convey
> bearer control inside the call control? Can we now assume
> that the versions
> can gallop along independently.
>
> Regards
>
> Ami
>
> -----Original Message-----
> From:   Pete Cordell [SMTP:pete.cordell at BT-SYS.BT.CO.UK]
> Sent:   Tuesday, February 09, 1999 5:05 PM
> To:     ITU-SG16 at mailbag.cps.intel.com
> Subject:        Re: Relationship of H.323 and H.245 versions
>
> Dear All,
>
> Just to clarify why the original question was asked,....
>
> It can be readily observed that functionality can be added to H.245
> without affecting H.225.  (For example, object oriented caps which
> enables H.RDC etc)  They are also functionally separate
> items.  In telco
> parlance (sorry!) H.225 is call control (or user invitation etc) and
> H.245 is bearer control (or media control).  It is quite
> legitimate for
> them to evolve at different paces as to a large degree they are
> orthogonal items.
>
> At a technical level I can see no benefit from inferring the version
> number of one from the version number of the other (any examples
> welcome) as these are basically two functional sub-systems working
> autonomously with only loose coupling (e.g. start, stop etc).
>  Also, as
> a gatekeeper can do call re-routing as defined in H.450 -
> assuming that
> the gatekeeper wants to relay messages as much as possible to
> allow the
> full functionality of the attached endpoints to be realised and not
> dumb-down the messaging to its level - an endpoint may well receive
> different versions of H.245 as the life of the call evolves
> (e.g. first
> connect to IVR, then route to agent, then connect to sales etc).  In
> this case inferring the H.245 version of the endpoint that you are
> connected to, say, third in a set of re-routes from the H.225
> version of
> the first endpoint you are connected to is totally bogus.
>
> However, to make life easier, if for marketing/procurement purposes
> alone, it does make sense for an H.323 version to require a minimum
> level of support from H.225 and H.245.  As H.323 and H.225 are
> intimately linked, saying that the H.323 version is one and
> the same as
> the H.225 version is no problem.  However, in a technology that is in
> its infancy and still trying to find its feet in terms of how people
> want to use it, it seems unreasonable to link H.245 versions
> explicitly
> in with the H.225 issue cycle if modifying H.245 allows more timely
> adaptation to perceived evolving market needs.
>
> For this reason I believe that the relationship of the H.245 version
> should be of the "or later" type so that exploitation of
> enhancements to
> H.245 do not need to wait for a new issue of H.323.  As an example of
> why this is attractive, it may be the case that there are no changes
> needed to justify an H.225 version 4.  However, enhancements
> may be made
> to H.245 after H.225 version 3 is issued.  What would we do with
> H.323/H.225 in this case?
>
> Regards,
>
> Pete
> =================================
> Pete Cordell
> BT Labs
> E-Mail: pete.cordell at bt-sys.bt.co.uk
> Tel: +44 1473 646436
> Fax: +44 1473 645499
> =================================
>
>
> >----------
> >From:  Santo Wiryaman[SMTP:swiryaman at VIDEOSERVER.COM]
> >Reply To:      Mailing list for parties associated with
> ITU-T Study Group
> 16
> >Sent:  05 February 1999 13:36
> >To:    ITU-SG16 at MAILBAG.INTEL.COM
> >Subject:       Re: Relationship of H.323 and H.245 versions
> >
> >Jim,
> >I do support this position. Thanks.
> >-santo
> >
> >> -----Original Message-----
> >> From: Jim Toga [SMTP:jim.toga at INTEL.COM]
> >> Sent: Thursday, February 04, 1999 6:29 PM
> >> To:   ITU-SG16 at mailbag.cps.intel.com
> >> Subject:      Re: Relationship of H.323 and H.245 versions
> >>
> >> Chris (and others)
> >>
> >> I'm penning up text (proposed) for the implementers guide.
> (Which I will
> >> post here for comments by tommorow) At this point I'm
> going to go with
> >> Paul's suggestion below even in light of your comments.  Here's the
> >> reasoning:
> >>
> >> If the GK is routing H.225.0 and _not_ H.245 (which is for further
> study,
> >> btw) then is should _not_ be messing with any
> syntax/encoding that it
> >> absolutely does not understand (for exactly this reason).  If it is
> >> routing
> >> both, then it can 'proxy' and give what-ever 'face' revision to the
> >> protocol that it wants (as long as it is consistent).
> >>
> >> I think what we gain by constraining the mix'n-match is
> consistency and
> >> predictability.  The cost is that, as we revise the
> 'umbrella' H.323
> >> Recommendation - products may have to support 'sets' of
> H.225.0/H.245 to
> >> play in multiple worlds.  I don't see any great _system_
> advantage to
> >> allowing vendors to provide a complete hodge-podge of
> stack revisions.
> >> (This is orthogonal to allowing vendors to provide a hodge-podge of
> stack
> >> support - H.235, annex E, annex G etc...)
> >>
> >> Regards,
> >> jimt.
> >>
> >>
> >> At 12:36 PM 2/1/99 -0000, you wrote:
> >> >Paul (and others),
> >> >
> >> >Consider the case of a v1 gatekeeper routing H.225.0 and
> NOT H.245 in a
> >> call
> >> >between two v2 endpoints.  The gatekeeper certainly MAY
> relegate the
> >> H.225.0
> >> >messages to v1.  This may be a policy decision, or it may
> be due to
> stack
> >> >capabilities.  Note that the gatekeeper may not always
> desire to relay
> >> >messages entirely transparently, and is entirely within
> its rights to
> >> make
> >> >this sort of alteration (although people writing H.323 stacks for
> >> >gatekeepers would probably be well advised to implement
> relaying of
> >> messages
> >> >or message fragments).  Certainly the standard should not
> mandate that
> >> >message relay should be entirely transparent.  Anyway,
> the upshot of
> this
> >> is
> >> >that all H.225.0 messages in the call will be relegated
> to v1 by the
> >> >gatekeeper.  The H.245 session runs directly end-to-end
> and will hence
> be
> >> >version 3, so both endpoints in the call need to be able
> to cope with
> an
> >> >H.245 session of a different version from that implied by
> the H.225.0
> >> >session.
> >> >
> >> >Similar discrepancies may occur in the opposite direction (later
> version
> >> of
> >> >H.225.0 than H.245) for similar, but marginally more
> complex reasons.
> >> >
> >> >So what do we gain by insisting on an endpoint supporting EXACTLY
> version
> >> 3
> >> >of H.245 if it happens to be EXACTLY version 2 of H.225.0 and vice
> versa?
> >> >Although I agree that it is what is currently specified
> I'm unconvinced
> >> it
> >> >buys us anything.
> >> >
> >> >Regards,
> >> >Chris
> >> >
> >> >> -----Original Message-----
> >> >> From: Paul Long [mailto:Plong at SMITHMICRO.COM]
> >> >> Sent: 29 January 1999 8:09
> >> >> To: ITU-SG16 at MAILBAG.INTEL.COM
> >> >> Subject: Re: Relationship of H.323 and H.245 versions
> >> >>
> >> >>
> >> >> Gary,
> >> >>
> >> >> 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
> >> >> protocolIdentifiers
> >> >>         > via H.323. For example,
> >> >>         >
> >> >>         >     H.225.0v1 => H.323v1 => H.245v2 and H.245v2 =>
> >> >> H.323v1 =>
> >> >> H.225.0v1
> >> >>         >     H.225.0v2 => H.323v2 => H.245v3 and H.245v3 =>
> >> >> H.323v2 =>
> >> >> H.225.0v2
> >> >>         >
> >> >>         > 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
> >> >> call.
> >> >>         >
> >> >>
> >> >>         But can H.225.0 V2 (H.323 V2) and H.245V4 (or 5) be
> >> >> used in the same
> >> >> call???
> >> >>
> >> >>         Gary
> >> >>
> >> >>         ------------------------------------------------------
> >> >>         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 delta-info.com
> >> >>         ------------------------------------------------------
> >> >>
> >> >
> >> +1-503-264-8816(voice)              Intel - Hillsboro, OR
> >>  mailto:jim.toga at intel.com         mailto:james.toga at ties.itu.int
> >>  PGP keyID 36 07 86 49 7D 74 DF 57  50 CB BA 32 08 9C 7C 41
> >
>



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