FW: AW: Call hold and transfer in H.323 AnnexF. Too limited??
Chris Purvis
Chris.Purvis at MADGE.COM
Tue Apr 6 09:21:41 EDT 1999
All,
I find it hard to believe that we can't do better (from the user's point of
view) than the old black-phone view of the world whereby people have to type
in various combinations of *s and digits to mean various different things to
the local exchange. Most endpoints, after all, have pretty UIs.
Now at the messaging level it may well make sense to have things APPEAR as
if that (ie the typing of arcane sequences of digits) is what is happening -
and it's possible that all we need to do to make that work in an
interoperable way is to define what sequences of characters in the
destination address in a setup message mean what sort of service. Do we
start from a point such as "Setup with a single destination address which is
e164 starting with '*' means arcane supplementary service", or define
another alias type for "arcane supplementary service" or what?
My aim is simply that an endpoint vendor should be ABLE to write things that
do not require the user to understand bizarre control sequences, and will be
able to access supplementary services wherever, and by whatever vendor, they
are provided.
Regards,
Chris
--
Dr Chris Purvis - Senior Development Engineer, WAVE CC Software
Madge Networks Ltd, Wexham Springs, Framewood Road, Wexham, Berks. ENGLAND
Phone: +44 1753 661 359 email: cpurvis at madge.com
> -----Original Message-----
> From: Espen Skjæran [mailto:Espen.Skjaeran at ERICSSON.COM]
> Sent: 26 March 1999 6:42
> To: ITU-SG16 at MAILBAG.INTEL.COM
> Subject: Re: AW: Call hold and transfer in H.323 AnnexF. Too limited??
>
>
> Hei,
>
> I do not think it is a bad thing if ISPs choose to control service
> profiles/configuration outside of H.450. There are a lot
> more flexible ways to transport data. Proven technologies
> exist today which are
> very flexible and extendible (HTTP, WAP, IVRs, etc). User
> oriented services
> might also include non-H.323 equipment (mobile, email, even a
> SIP terminal!), so
> confining it to H.450 and H.323 would limit the possibillity
> for "fancy"
> services significantly, thereby also limiting the
> distribution of H.323.
>
> If a Call Forward service is put in the network, it turns
> more into a user
> oriented than an endpoint oriented service, and the
> possibilities for extensions are huge. As soon as the "Call
> Forward Unreachable"
> is standardized, I might come up with a proposal for call
> forward based on
> week/time, and this will hardly ever stop. We need a flexible
> mechanism for
> controlling these services, not new detailed service specifications.
>
> As the mechanisms for a call forward done in the network does
> not require the
> same level of interactions as a terminal
> oriented (or in-call) service, we do not need to follow the
> same approach as
> H.450, where services are specified in detail.
> The H.450 approach makes the creation (and extension) of a
> service a very
> lenghty process, and is actually a great
> obstacle to creativity and development of new user oriented
> services. (Though
> for in-call services I don't see any way around it...)
>
> Espen
>
>
> "Derks, Frank" wrote:
>
> > Paul,
> >
> > you got my points exactly right. The reason that I weakened
> by arguments by
> > hinting at the ease of upgrade in an IP environment was to
> avoid people
> > coming back with this line of argument. Although using
> "DTMF digits" as the
> > means to access services may not be the most elegant one,
> it is probably the
> > simplest and it maps well onto a simple "blackphone" type
> of terminal. If we
> > do not provide for something fairly simple (both for the
> users and the
> > service providers) then the chances are that service
> providers will come up
> > with "(IP) Telephony unrelated" means to access services.
> E.g. they could
> > provide Web pages that allow customers to specify their
> service behaviour.
> >
> > Frank
> >
> > -----Original Message-----
> > From: Paul E. Jones [mailto:paul.jones at TIES.ITU.INT]
> > Sent: 22 March 1999 19:11
> > To: ITU-SG16 at MAILBAG.INTEL.COM
> > Subject: Re: AW: Call hold and transfer in H.323 AnnexF.
> Too limited??
> >
> > Frank,
> >
> > I do agree that two mechanisms for accomplishing the same
> task is a bad
> > idea. I, too, would rather see one mechanism employed-- we
> do want to
> > create interoperable equipment, after all. Unfortunately,
> we already have
> > two ways of doing "call hold"-- H.450.4 and "empty
> capability sets" (see
> > 7.6.2 of Annex F).
> >
> > The issues you raise with supplementary services echoes the
> concerns of
> > those also participating in the TIPHON work. Essentially,
> service providers
> > would like to be able to add new services without upgrading
> software in the
> > endpoints. Although it may be possible to upgrade IP phone
> devices, I can
> > assure you that the average person would never do that--
> once the phone is
> > plugged in, it will stay there until it stops working.
> More importantly,
> > why would one want to require somebody who purchased a
> hardware phone device
> > to upgrade periodically?
> >
> > We need to engineer a solution so that the telephony
> service providers can
> > introduce new services without requiring software upgrades
> in the endpoints.
> > I would like to see SET device to take advantage of those
> newly introduced
> > services without software or hardware upgrades.
> >
> > Paul
> >
> > -----Original Message-----
> > From: Derks, Frank <F.Derks at PBC.BE.PHILIPS.COM>
> > To: ITU-SG16 at MAILBAG.INTEL.COM <ITU-SG16 at MAILBAG.INTEL.COM>
> > Date: Monday, March 22, 1999 5:45 AM
> > Subject: Re: AW: Call hold and transfer in H.323 AnnexF.
> Too limited??
> >
> > >Folks,
> > >
> > >when talking about a Simple Endpoint Type, I think we
> should aim for it to
> > >be something that closely resembles a black phone. This
> way it becomes a
> > lot
> > >easier to define what its capabilities are and it makes
> life easy on the
> > >users and on those companies that will actually make
> (physical) IP-phones.
> > >These phones should probably look and act like the normal
> phones that are
> > >currently being used. Looking at how most supplementary
> services are
> > >accessed in both the public and the private (PBX)
> networks, I think it is
> > >safe to say that in most cases we are talking about
> "stimulus protocols".
> > >I.e. DTMF digits are sent to an exchange and the exchange
> interprets
> > certain
> > >digit sequences as being the invocation of some service
> rather than a
> > number
> > >to be dialled. The big advantage over functional protocols
> (like H.450.x)
> > >being that services can be added from the exchange side,
> without the
> > >terminal having to be modified as well.
> > >
> > >Functional protocols never became a success in the ISDN
> world and this may
> > >end up to be the same in the IP world. However, having
> said this, there is
> > a
> > >lot more potential for easy upgrading of e.g. terminal
> software in this
> > >domain, which reduces the side effects of functional protocols.
> > >
> > >It does not seem to make sense to define "alternative"
> mechanisms to
> > provide
> > >services, so I would strongly opt for using H.450.x when
> possible and using
> > >a simple stimulus protocol otherwise. The latter would
> allow service
> > >providers to easily make services available and I see no
> reason why this
> > >should be standardised. In practice, today, we already see
> that certain
> > >digit sequences for service activation are identical in
> several countries.
> > >
> > >Frank
> > >
> > >-----------------------------------------------------
> > >Frank Derks |Tel +31 35 6893238 |
> > >Advanced Development |Fax +31 35 6891030 |
> > >Philip Business Communications |P.O. Box 32 |
> > > |1200 JD Hilversum |
> > > |The Netherlands |
> > >----------------------------------------------------|
> > >E-mail: mailto:f.derks at pbc.be.philips.com |
> > >WWW: http://www.business-comms.be.philips.com |
> > >-----------------------------------------------------
> > >
> > >
> > >
> > >-----Original Message-----
> > >From: Klaghofer Karl ICN IB NL IP 7
> > >[mailto:Karl.Klaghofer at ICN.SIEMENS.DE]
> > >Sent: 18 March 1999 22:36
> > >To: ITU-SG16 at MAILBAG.INTEL.COM
> > >Subject: AW: AW: Call hold and transfer in H.323 AnnexF.
> Too limited??
> > >
> > >
> > >See comment below.
> > >
> > >Karl
> > >
> > >> -----Ursprüngliche Nachricht-----
> > >> Von: Paul E. Jones [SMTP:paul.jones at TIES.ITU.INT]
> > >> Gesendet am: Donnerstag, 18. März 1999 18:57
> > >> An: ITU-SG16 at mailbag.cps.intel.com
> > >> Betreff: Re: AW: Call hold and transfer in H.323 AnnexF. Too
> > >> limited??
> > >>
> > >> Karl,
> > >>
> > >> Unfortunately, I will have to disagree with your
> comments. While it is
> > >> true
> > >> that the H.450 supplementary services could be utilized
> in a SET device,
> > I
> > >> believe that introducing H.450 into a SET breaks the
> spirit of that work.
> > >>
> > >> The goal of Annex F is to define a "Simple Endpoint
> Type". There are
> > >> simpler ways to put a call on hold and to transfer a
> call. Introducing
> > >> H.450 introduces a lot more complexity that I believe we
> want to have.
> > If
> > >> Annex F is not sufficiently clear on how to simply
> transfer a call or put
> > >> a
> > >> call on hold, we should work on that text-- I will
> absolutely disagree
> > >> with
> > >> introducing H.450 into a SET device.
> > > [Klaghofer, Karl PN VS LP3] Whatever you mean with
> > "introducing" -
> > >H.450 as I sayd in my previous mail is a way of providing
> supplementary
> > >services like call hold and call transfer to a SET device.
> It IS already
> > >part of the H.323 Annex F!
> > >> Paul
> > >>
> > >> -----Original Message-----
> > >> From: Klaghofer Karl ICN IB NL IP 7
> <Karl.Klaghofer at ICN.SIEMENS.DE>
> > >> To: ITU-SG16 at MAILBAG.INTEL.COM <ITU-SG16 at MAILBAG.INTEL.COM>
> > >> Date: Wednesday, March 17, 1999 3:27 PM
> > >> Subject: AW: Call hold and transfer in H.323 AnnexF. Too
> limited??
> > >>
> > >>
> > >> >Gunnar,
> > >> >
> > >> >You are referring to call hold and transfer in
> conjunction with H.323
> > >> Annex
> > >> >F SETs (Audio or Text) and clause 7.6 of H.323 Annex F.
> > >> >
> > >> >Talking about call hold, clause 7.6 of H.323 Annex F is
> not needed for a
> > >> SET
> > >> >at all. Call Hold works for a SET as it is defined in H.450.4.
> > >> >
> > >> >Talking about Call Transfer, clause 7.6 of H.323 Annex
> F is not needed
> > >> for
> > >> a
> > >> >SET, if the transfer is executed by the endpoints as
> defined in H.450.2.
> > >> >Codec re-negotiation you are referring to is no problem
> and takes place
> > >> >between the transferred and the transferred-to
> endpoint. This may cover
> > >> your
> > >> >case with wireless endpoints being involved.
> > >> >
> > >> >For call transfer, section 7.6 of H.323 Annex F is only
> needed if the
> > >> >gatekeeper or a proxy acts on behalf of the transferred
> SET endpoint B.
> > >> >However, media re-negotiation also should work here as
> part of the
> > >> fastStart
> > >> >method.
> > >> >
> > >> >Regards,
> > >> >Karl
> > >> >------------------------------------------------
> > >> >Karl Klaghofer, Siemens AG, Dpmt. ICN IB NL IP7
> > >> >Hofmannstr. 51, D-81359 Munich, Germany
> > >> >Tel.: +49 89 722 31488, Fax.: +49 89 722 37629
> > >> >e-mail: karl.klaghofer at icn.siemens.de
> > >> >
> > >> >
> > >> >
> > >> >> -----Ursprüngliche Nachricht-----
> > >> >> Von: Gunnar Hellstrom [SMTP:gunnar.hellstrom at OMNITOR.SE]
> > >> >> Gesendet am: Dienstag, 16. März 1999 23:01
> > >> >> An: ITU-SG16 at mailbag.cps.intel.com
> > >> >> Betreff: Call hold and transfer in H.323 AnnexF.
> Too limited??
> > >> >>
> > >> >> Dear multimedia experts.
> > >> >>
> > >> >> In my efforts to establish the simple IP voice and
> text telephone Text
> > >> >> SET,
> > >> >> I came across a section in H.323 Annex F (Simple
> Endpoint Type, TD11
> > in
> > >> >> Monterey) that I feel is causing a functional
> obstacle also to the
> > >> voice
> > >> >> users. Can anyone clarify if I am correct and why it
> is specified the
> > >> way
> > >> >> it is.
> > >> >>
> > >> >> In section 7.6.1 and 7.6.2 it is specified:" The
> Audio SET device
> > >> shall
> > >> >> then resume transmitting its media stream(s) to the transport
> > >> address(es)
> > >> >> newly indicated in the OpenLogicalChannel structures."
> > >> >> I understand that this means that you cannot
> re-negotiate audio
> > coding,
> > >> >> and
> > >> >> you cannot add text conversation after rerouting the
> call from a Voice
> > >> >> only
> > >> >> SET to a Text SET.
> > >> >>
> > >> >> Re-negotiating the audio coding will probably be a
> desired function,
> > >> e.g.
> > >> >> when rerouting from a fixed to a wireless IP phone.
> > >> >> Adding a data channel for text will also be a desired
> function, after
> > >> >> answering a call in an audio-only SET, and then
> rerouting it to a
> > >> >> text-capable SET.
> > >> >> That action is very common in today's text telephone
> usage, and I
> > would
> > >> >> expect it to be just as common in the IP telephony
> world. You first
> > >> >> receive
> > >> >> the call in the terminal that is closest to you, and
> then you get a
> > >> reason
> > >> >> to start text mode. Then you transfer the call to
> another device with
> > >> text
> > >> >> capabilities, where you can switch mode.
> > >> >>
> > >> >> Questions:
> > >> >>
> > >> >> 1. Is that kind of call transfer that is handled by
> the mechanisms in
> > >> 7.61
> > >> >> and 7.6.2?
> > >> >>
> > >> >> 2. Are my conclusion right about the limitations?
> > >> >>
> > >> >> 3. Is this limitation a consequence of using Fast Connect?
> > >> >>
> > >> >> 4. Do you see any possibility to avoid the negative
> effects of it - to
> > >> >> make
> > >> >> re-negotiation possible?
> > >> >>
> > >> >> 5. Is the specified functionality acceptable in the
> voice world? If
> > two
> > >> >> devices have agreed on a voice coder, is it likely
> that the third
> > >> device
> > >> >> supports it? Will this not create a lot of
> unsuccessful call transfers
> > >> >> where the users will have a no chance to understand
> why they fail?
> > >> >>
> > >> >> ----
> > >> >>
> > >> >> Another question area:
> > >> >>
> > >> >> 6. When selecting the transport protocol for the text
> conversation,
> > the
> > >> >> current draft (APC 1504) specifies TCP or UDP. I
> realize that there
> > are
> > >> >> situations where TCP must be avoided. One such situation is a
> > >> sub-titled
> > >> >> H.332 transmission. Also other multi-casting
> situations is better off
> > >> with
> > >> >> a UDP based transport protocol.
> > >> >> I am therfore now leaning towards using RTP as the
> transport for text
> > >> >> conversation. With RTP we can discover dropped frames
> and possibly
> > >> invent
> > >> >> a
> > >> >> mechanism to mark that event in the text stream for
> T.140 to display.
> > >> If
> > >> >> we
> > >> >> have less than 3 % dropped frames, I think the users
> would accept it.
> > >> >>
> > >> >> 6.1 Do you agree that there are situations when TCP
> should be avoided,
> > >> and
> > >> >> a UDP based protocol preferred?
> > >> >>
> > >> >> 6.2 Do you agree that RTP is a good alternative, with
> a thin protocol
> > >> for
> > >> >> error indications to the user?
> > >> >>
> > >> >> 6.3 Most packets will carry only 1-4 characters . Can
> anyone give me
> > an
> > >> >> indication on the expected packet loss rates in
> different situations
> > >> for
> > >> >> such packets. Or a document giving such figures. Is
> max 3% loss
> > >> reachable?
> > >> >>
> > >> >> Please give your view on these questions.
> > >> >>
> > >> >> Best regards
> > >> >>
> > >> >> Gunnar Hellström
> > >> >> -----------------------------------------------
> > >> >> Gunnar Hellstrom
> > >> >> Representing Ericsson in ITU-T
> > >> >>
> > >> >> E-mail gunnar.hellstrom at omnitor.se
> > >> >> Tel +46 751 100 501
> > >> >> fax +46 8 556 002 06
>
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