Enforcing symmetric operation in the context of slow startfor H. 323v4

Anatoli Levine alevine at RADVISION.COM
Fri Sep 8 15:36:05 EDT 2000


Chris,

if you originate the fast start and you offer only one codec for both receive and
transmit (g711Ulaw = 60, for instance), the receiving side can either accept this
or drop the call, but it can't use any other codec and also can't change
parameters for the codec which was offered.

Anatoli

Chris Wayman Purvis wrote:

> This may be a silly question, but how is symmetry enforced in fastStart?
>
> Regards,
> Chris
>
> Roni Even wrote:
> >
> > Hi,
> > I think the issue is very important, there is no clear way to achieve
> > symmetric operation today.
> > In H.323 it states that if a terminal supports H.263 CIF it implies that it
> > support H.261 CIF. On the other hand it states that a terminal can use the
> > receive capabilities to signal which codec it supports, it is not clear if
> > for example a terminal signal that it can receive H.263 CIF, if the
> > transmitter can send H.261 CIF since it is implied but is less preferable,
> > or does it mean that it can only receive H.263 CIF.
> > I think that we can use this change also to make the text correct at least
> > for the symmetric mode. It should state that these are the modes that the
> > terminal can do in symmetric mode and not the implied ones.
> > Roni Even
> > -----Original Message-----
> > From: Mike Nilsson [mailto:mike.nilsson at BT.COM]
> > Sent: Thursday, September 07, 2000 11:47 AM
> > To: ITU-SG16 at MAILBAG.INTEL.COM
> > Subject: Enforcing symmetric operation in the context of slow start for
> > H. 323v4
> >
> > At the Portland rapporteur's meeting of Q12-14, document APC-1881,
> > 'Enforcing symmetric operation in the context of slow start for H.323v4',
> > was discussed. The outcome of the discussion, as described in the meeting
> > report, is:
> >
> >         This was accepted for the H.323 IG and also H.323 V4.   It was
> > agreed that this was meritorius, but that some further discussion was
> > needed. See TD-47.  The agreement is that APC-1881 is adopted for changes to
> > H.323 V4, and TD-47 for H.245 V7, with the redefinition of the
> > receiveAndTransmitt capability being the preferred approach. It was noted
> > that the rejectReason needs to be mentioned in TD-47. Text will also be
> > added to note that the procedures of TD-47 only apply if the slave has
> > detected a conflict.  All are urged to look very closely at this, and to
> > consider if there are any issues with this.  If any are found, we will make
> > changes in November. The editor will post this discussion on the mailing
> > list to ensure broad discussion.
> >
> > The purpose of this mail is simply to do as the meeting report stated, and
> > highlight the issue and to try to get broad agreement on the proposed
> > solution. As far as H.245 is concerned the proposed solution is to include
> > text from TD-47a that is labelled as 'Proposal for immediate action' and the
> > first option (redefinition of the receiveAndTransmitt capability) from the
> > section labelled 'Longer term options'.
> >
> > The documents are available at:
> >
> >         ftp://standard.pictel.com/avc-site/0008_Por/APC-1881.zip
> >         ftp://standard.pictel.com/avc-site/0008_Por/TD-47a.zip
> >
> > Best regards
> >
> > Mike Nilsson
> >
> > --------------------
> > Mike Nilsson
> > Multimedia Applications
> > B81 Room 102 pp14
> > BT Advanced Communications Technology Centre
> > Adastral Park, Martlesham Heath, Ipswich, IP5 3RE, UK
> > Tel:    +44 1473 645413
> > Mobile: +44 7808 635412
> > Fax:    +44 1473 646589
> > Email:  mike.nilsson at bt.com
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > For help on this mail list, send "HELP ITU-SG16" in a message to
> > listserv at mailbag.intel.com
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > For help on this mail list, send "HELP ITU-SG16" in a message to
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>
> --
> Dr Chris Purvis -- Development Manager
> ISDN Communications Ltd, The Stable Block, Ronans, Chavey Down Road
> Winkfield Row, Berkshire.  RG42 6LY  ENGLAND
> Phone: +44 1344 899 007
> Fax:   +44 1344 899 001
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> For help on this mail list, send "HELP ITU-SG16" in a message to
> listserv at mailbag.intel.com
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