H.323 delta doc

Scott Petrack Scott_Petrack at VOCALTEC.COM
Sun Jan 18 03:08:02 EST 1998


Thinking about Toby's concern, the only way I can think of to mandate
preservation and to be totally backward compatible is to add to the
H323-UU-PDU structure a new field after the dots:

H323-UU-PDU ::= SEQUENCE
{
     h323-message-body   CHOICE
     {
          setup               Setup-UUIE,
          callProceeding CallProceeding-UUIE,
          connect        Connect-UUIE,
          alerting       Alerting-UUIE,
          userInformation     UI-UUIE,
          releaseComplete     ReleaseComplete-UUIE,
          facility       Facility-UUIE,
          ...
     },
     nonStandardData          NonStandardParameter OPTIONAL,
     ...
     nonStandardSequence SEQUENCE of NonStandardParameter OPTIONAL
}

v2 implementations should be told not to write into the old
nonStandardParameter and to use the new one. Such a change is pretty tiny,
and if I'm not mistaken would guarantee complete backward compatible and
give the required new function.

If it is really too late it could be done in the implementor's guide, I
suppose.

Scott





tnixon at MICROSOFT.COM on 01/16/98 09:57:39 PM

Please respond to ITU-SG16 at mailbag.jf.intel.com

To:   ITU-SG16 at mailbag.jf.intel.com
cc:    (bcc: Scott Petrack)
Subject:  Re: H.323 delta doc




While we don't necessarily oppose migrating to a sequence of
nonStandardParameter in the nonStandardData element of H323-UU-PDU in
H.225.0 messages, everyone should be aware that NetMeeting does make use of
this element in the "old" unstructured form. I think you'd find NetMeeting
users disturbed by the loss of functionality that occurred if intermediate
devices overwrote nonStandardData, as provided for in the last paragraph of
the proposed text. We would be much more comfortable if the text did not
permit overwriting -- or mandated preservation -- when the message is being
conveyed between H.323v1 endpoints.
        -- Toby
___________________________________________________________
Toby Nixon, Program Manager - NetMeeting
http://www.microsoft.com/netmeeting
Microsoft Corporation, Applications and Internet Client Group, Redmond  WA
USA
+1 (425) 936-2792     Fax: +1 (425) 936-7329    mailto:tnixon at microsoft.com

> -----Original Message-----
> From: Pete Cordell [SMTP:pete.cordell at BT-SYS.BT.CO.UK]
> Sent: Friday, January 16, 1998 4:59 AM
> To:   ITU-SG16 at MAILBAG.INTEL.COM
> Subject:      Re: H.323 delta doc
>
> Gary,
>
> Two things....
>
> 1.  I included the wrong text in the mail I originally sent you...  The
> text should have been:-
>
> "To include multiple elements of nonStandardData in an H.225 message the
> nonStandardParameter is used in the following way.  This special use of
> the nonStandardParameter is identified by setting the
> nonStandardIdentifier to be an OBJECT IDENTIFIER of type {itu-t (0)
> recommendation (0) h (8) 2250}.  In this case the information contained
> in the data part of the nonStandardParameter consists of a fragment of
> ASN.1 encoded into an OCTET STRING (The ASN.1 encoding rules are the
> same as those for all H.225 messages).  The ASN.1 fragment has the
> following syntax:
>
> ExtendNonStandard ::= SEQUENCE OF NonStandardParameter
>
> It is recommended that entities use this method for including
> nonStandardData in messages even if they only insert one piece of
> information as it allows other entities in the signalling path to either
> add or delete their own nonStandardData without overwriting information
> inserted by the originating entity.
>
> If intermediate entities on the signalling path need to insert
> nonStandardData when there is already nonStandardData present that is
> not of the extended form described above they are encouraged to take
> measures to ensure that the original nonStandardData can be recovered by
> entities further down the signalling path once those entities have
> removed any nonStandardData specific to them.  This can be achieved by
> nesting the original nonStandardData field inside the
> nonStandardParameter created by the intermediate entity.
>
> However, endpoints should be aware that if they do not insert
> nonStandardData in the extended form it may be overwritten by
> intermediate signalling entities."
>
> This is less enforcing than the text you received before, which seems
> more in line with backwards compatibility.
>
> 2.  If you're imply that it should be in H.225.0 I think that makes
> sense (even though I had originally assumed it would go in H.323).  In
> the discussion on nonStandardParameter in  Section 7.6 H.225.0 seems a
> good place.
>
> 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:  Gary A. Thom[SMTP:gthom at DELTA-INFO.COM]
> >Sent:  16 January 1998 00:40
> >To:    ITU-SG16 at MAILBAG.INTEL.COM
> >Subject:       Re: H.323 delta doc
> >
> >Pete,
> >
> >Is this text for a new section in H.323 or for
> >the non-standard semantics in H.225.0???
> >
> >Gary
> >
> >------------------------
> >  From: Pete Cordell <pete.cordell at BT-SYS.BT.CO.UK>
> >  Subject: Re: H.323 delta doc
> >  Date: Wed, 14 Jan 1998 14:01:48 -0000
> >  To: ITU-SG16 at MAILBAG.INTEL.COM
> >
> >
> >> Gary,
> >>
> >> I think we got consensus on the nonStandard issue to the point that no
> >> one objected (!) and most people seemed to be positive.  The suggested
> >> wording (including wording to cover off Joerg's comments) was:
> >>
> >> "To include multiple elements of nonStandardData in an H.225 message
> the
> >> nonStandardParameter SHALL BE in the following way.  This special use
> of
> >> the nonStandardParameter is identified by setting the
> >> nonStandardIdentifier to be an OBJECT IDENTIFIER of type {itu-t (0)
> >> recommendation (0) h (8) 2250}.  In this case the information
contained
> >> in the data part of the nonStandardParameter SHALL CONSIST of a
> fragment
> >> of ASN.1 encoded into an OCTET STRING (The ASN.1 encoding rules are
the
> >> same as those for all H.225 messages).  The ASN.1 fragment has the
> >> following syntax:
> >>
> >>  ExtendNonStandard ::= SEQUENCE OF NonStandardParameter
> >>
> >> Entities SHOULD use this method for including nonStandardData in
> >> messages even if they only insert one piece of information as it
allows
> >> other entities in the signalling path to either add or delete their
own
> >> nonStandardData without overwriting information inserted by the
> >> originating entity.
> >>
> >> If intermediate entities on the signalling path need to insert
> >> nonStandardData when there is already nonStandardData present that is
> >> not of the extended form described above (i.e. this sentence goes
below
> >> what I originally presented, just avoid any confusion!) they are
> >> encouraged to take measures to ensure that the original
nonStandardData
> >> can be recovered by entities further down the signalling path once
> those
> >> entities have removed any nonStandardData specific to them.  This can
> be
> >> achieved by nesting the original nonStandardData field inside the
> >> nonStandardParameter created by the intermediate entity.
> >>
> >> However, endpoints should be aware that if they do not insert
> >> nonStandardData in the extended form it may be overwritten by
> >> intermediate signalling entities."
> >>
> >> 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:  Gary A. Thom[SMTP:gthom at DELTA-INFO.COM]
> >> >Sent:  09 January 1998 23:00
> >> >To:    ITU-SG16 at MAILBAG.INTEL.COM
> >> >Subject:       H.323 delta doc
> >> >
> >> ><<File: H323DL.DOC>>
> >> >Hi all,
> >> >
> >> >
> >> >Attached is the Delta document for H.323.
> >> >
> >> >
> >> >I did not include any changes for nonStandard or Fast Start as I did
> >> >not hear a widely
> >> >accepted proposal.
> >> >
> >> >If I missed anyones comments, please let me know.
> >> >
> >> >
> >> >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
> >> >------------------------------------------------------
> >> >
> >
> >---------------End of Original Message-----------------
> >
> >------------------------------------------------------
> >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
> >------------------------------------------------------
> >



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