November 1998 - sg16-avd - lists.packetizer.com

Re: H.323 Annex E
by Kaynam Hedayat 24 Nov '98

24 Nov '98

Kishore, It was decided at the last meeting that Q.931 headers will be present for UDP call signaling. The absence of Q.931 headers was an oversight by the members of the group. Kaynam Kishore Ramisetty <kish(a)TRILLIUM.COM> on 11/20/98 02:57:50 PM Please respond to Mailing list for parties associated with ITU-T Study Group 16 <ITU-SG16(a)mailbag.cps.intel.com> To: ITU-SG16(a)mailbag.cps.intel.com cc: (bcc: Kaynam Hedayat/PicTel) Subject: H.323 Annex E H.323 Annex E proposes using simultaneous (or a little later) TCP and UDP transport connections to provide seamless interoperability with non-Annex E devices. This results in inefficiencies because we now have to transmit two kinds of PDUs for the same call. (Q.931 headers are present for TCP transport and they are absent for UDP). This again has the unfortunate consequence of mandating higher layers to be aware of the transport because upper layers have to deal with duplicates arriving from TCP and UDP connections. (Section E.5.3 para 4 and 5) A simpler solution to this problem is, Annex E compliant end points should register with gatekeeper about their capability of supporting Annex E in RRQ message and gatekeeper propogates this in ACF messages. So, it is easy to determine apriori whether to attempt UDP/TCP connection to the destination end points (because non Annex E devices won't register anything with gatekeepers). This will also require some additions to GK-GK communication so that such kinds of profiles can be communicated across zones. This solution of course requires V3 GKs. If a V3 GK (or GK itself) is absent, then end points could have the option of trying simultaneous connections or simply falling back to TCP. This solution would make sure that going forward to V3 we can get rid of this simultaneous connection establishment procedures. I would like some comments from the group. Thanks, -Kishore.

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Torino meeting report
by Sakae OKUBO 22 Nov '98

22 Nov '98

Dear Torino meeting participants, The outcome of the closing session last Friday has been placed at the /incoming directory: ftp://standard.pictel.com/avc-site/Incoming/ or http://standard.pictel.com/ftp/avc-site/Incoming TD-12b.doc Genral TD-18b.doc Q.12 TD-19a.doc Q.13 TD-07a.doc Q.14 TD-15a.doc LS to SG15 TD-20a.doc LS to MPEG re MPEG-4 TD-22a.doc LS to MPEG re MPEG-2 These and other materials will later be integrated into APC-1485. PS - Please note that our mailserver(a)giti.or.jp will temporarily be shut down till around 1 AM (GMT) on Tuesday. Please use okubo(a)mxz.meshnet.or.jp if there is any message to me during that time. Best regards, Sakae OKUBO (Mr.) *********************************************************** Waseda Research Center Telecommunications Advancement Organization of Japan (TAO) 5th Floor, Nishi-Waseda Bldg. 1-21-1 Nishi-Waseda, Shinjuku-ku, Tokyo 169-0051 Japan Tel: +81 3 5286 3830 Fax: +81 3 5287 7287 e-mail: okubo(a)giti.or.jp ***********************************************************

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Re: Gateway Decomposition Requirements
by Dale L. Skran 21 Nov '98

21 Nov '98

At 07:54 PM 11/19/98 -0500, Tom-PT Taylor wrote: >I have been told that APC-1466 states enough requirements for the device >control interface A, but that we should have requirements for the signalling It would be more accurate to say that it is a very good start. As mentioned at the meeting, and as discussed below, the terms of reference are not fully reflected in the requirements. >interfaces B, C, and D before committing ourselves to protocol design. I >just don't have the same feeling for detailed requirements in those areas >that I have for interface A. I can only think of two requirements: these >interfaces must >- pass all the signalling content offered to them Not sure what you mean. >- do it quickly and reliably. Of course. I suggest looking at what IPDC does, but this is what comes to mind: B Interface: 1)It must be possible to request that the MGW do H.323 signaling to a specified IP address, which might, for example, be a composed GW. Of course, this is an optional feature. 2)It must be possible to do this call by call, ie. for one call request 323 signaling and for the next not request it. 3)Point 2 strongly suggests that the protocol for B and A should be the same, for example, as in IPDC. C Interface: 1)It must be possible to bring call signaling up to the controller so that signaling can be terminated there (optionally). This suggests a need to map different types of call signaling into a single protocol. Q.931 is an obvious solution. See Ascend's "Reliable Gateway Signaling Protocol" for an example. 2)It must be possible to terminate/generate the Q.931, etc. call signaling on the gateway (optionally). This is equivalent to having the MGW signal 323 on the packet size. This allows a call from a MGW with IMT trunks to talk to a MGW with PRI/T1 trunks under SS7 control. 3)(1) is a kind of tunneling for Q.931, so it is not so clear that this should be the same protcol as A/B. 4)(2) seems like it should be a part of the A/B protcol. X requirements(common requirements on A/B/C): 1)A/B/C signaling must all travel over the same data network to the MGW. 2)It must be possible to use both UDP and TCP 3)Either the protocol is Message/ACK or we must use a reliable UDP like Annex E. 4)Given the similiarity of B/C to A, all should use a similar message format, the same ports, etc. to ease implementation. Note that both B/C parts are probably optional, but they are part of the same protocol as A. The only exception is the case where you want to put SCN call signaling(Q.931, FAS SS7) in the controller, and you need to tunnel it up. This stuff might be tunneled through the A/B/C protocol, or it might be a separate protocol/port, i.e. Q.931 on Annex E with a different port. 5)Part of the A/B/C message set must include an MGW cap set so the controller knows what to expect As noted at the meeting, you need to reflect the terms of reference in the A requirements. A couple of obvious ones: A Interface 1)Must include video/data (i.e. consider the possibility of incoming H.320/H.324 calls). 2)Must not duplicate H.323 functions, eg. cap exchange, conference management, etc. 3)Must be elemental. This goes along with (2). cap exchange is not an elemental function. 4)Must be suitable for connecting an MC (MultiPoint Controller) to an MP (Media Processer) as defined in H.323. This implies a need for elemental conferencing primatives, but broken out by media stream, ie. data MP, voice MP, video MP. I'm sure there is more that could be added by a careful review of the terms of reference. Dale Skran Rapporteur, Q13 WP2 SG16 ITU-T > >Can anyone get us down to another level of detail? > >Tom Taylor >E-mail: taylor(a)nortelnetworks.com (internally Tom-PT Taylor) >Tel.: +1 613 765 4167 (internally 395-4167) >FAX: +1 613 763 7236 (internally 393-7236) >

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Re: H.323 Annex E
by Yoav Medan 21 Nov '98

21 Nov '98

Kishore, IMHO this is more than just an interesting approach. I can see a backward compatibility problem only when endpoints are trying to engage in a peer-to-peer call setup (no GK, thank you). But in a GK routed call setup, why not negotiate UDP or TCP as part of the initial caps exchange? This applies to both endpoint-GK and to GK-GK communications, as you cleverly pointed out. I think we ought to design Internet "Green" (i.e. friendly) protocols that do not flood the network with redundant information unnecessarily. Let's be clever about it rather than smart. Regards Yoav Medan IBM Research, Haifa Lab, Israel Kishore Ramisetty <kish(a)TRILLIUM.COM> on 20-11-98 09:57:50 PM Please respond to Mailing list for parties associated with ITU-T Study Group 16 <ITU-SG16(a)MAILBAG.INTEL.COM> To: ITU-SG16(a)MAILBAG.INTEL.COM cc: (bcc: Yoav Medan/IBMHAIFA) Subject: H.323 Annex E H.323 Annex E proposes using simultaneous (or a little later) TCP and UDP transport connections to provide seamless interoperability with non-Annex E devices. This results in inefficiencies because we now have to transmit two kinds of PDUs for the same call. (Q.931 headers are present for TCP transport and they are absent for UDP). This again has the unfortunate consequence of mandating higher layers to be aware of the transport because upper layers have to deal with duplicates arriving from TCP and UDP connections. (Section E.5.3 para 4 and 5) A simpler solution to this problem is, Annex E compliant end points should register with gatekeeper about their capability of supporting Annex E in RRQ message and gatekeeper propogates this in ACF messages. So, it is easy to determine apriori whether to attempt UDP/TCP connection to the destination end points (because non Annex E devices won't register anything with gatekeepers). This will also require some additions to GK-GK communication so that such kinds of profiles can be communicated across zones. This solution of course requires V3 GKs. If a V3 GK (or GK itself) is absent, then end points could have the option of trying simultaneous connections or simply falling back to TCP. This solution would make sure that going forward to V3 we can get rid of this simultaneous connection establishment procedures. I would like some comments from the group. Thanks, -Kishore.

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H.323 Annex E
by Kishore Ramisetty 20 Nov '98

20 Nov '98

H.323 Annex E proposes using simultaneous (or a little later) TCP and UDP transport connections to provide seamless interoperability with non-Annex E devices. This results in inefficiencies because we now have to transmit two kinds of PDUs for the same call. (Q.931 headers are present for TCP transport and they are absent for UDP). This again has the unfortunate consequence of mandating higher layers to be aware of the transport because upper layers have to deal with duplicates arriving from TCP and UDP connections. (Section E.5.3 para 4 and 5) A simpler solution to this problem is, Annex E compliant end points should register with gatekeeper about their capability of supporting Annex E in RRQ message and gatekeeper propogates this in ACF messages. So, it is easy to determine apriori whether to attempt UDP/TCP connection to the destination end points (because non Annex E devices won't register anything with gatekeepers). This will also require some additions to GK-GK communication so that such kinds of profiles can be communicated across zones. This solution of course requires V3 GKs. If a V3 GK (or GK itself) is absent, then end points could have the option of trying simultaneous connections or simply falling back to TCP. This solution would make sure that going forward to V3 we can get rid of this simultaneous connection establishment procedures. I would like some comments from the group. Thanks, -Kishore.

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signoff itu-g16
by Staffan Olsén 20 Nov '98

20 Nov '98

signoff itu-g16

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Gateway Decomposition Requirements
by Tom-PT Taylor 19 Nov '98

19 Nov '98

I have been told that APC-1466 states enough requirements for the device control interface A, but that we should have requirements for the signalling interfaces B, C, and D before committing ourselves to protocol design. I just don't have the same feeling for detailed requirements in those areas that I have for interface A. I can only think of two requirements: these interfaces must - pass all the signalling content offered to them - do it quickly and reliably. Can anyone get us down to another level of detail? Tom Taylor E-mail: taylor(a)nortelnetworks.com (internally Tom-PT Taylor) Tel.: +1 613 765 4167 (internally 395-4167) FAX: +1 613 763 7236 (internally 393-7236)

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None
by Robert Webber 18 Nov '98

18 Nov '98

Please be advised that services at standard.pictel.com will be inaccessible for some period of time on both 19 and 21 November. This outage is due to a change in our Internet connection, and the change is expected to increase available bandwidth to the ftp repositories and WWW pages here. The first outage will be tomorrow night, 11/19, starting at approximately 5:00pm EST. This outage should last for about an hour. The second outage will be this Saturday, 11/21, starting at 9:00am EST. This outage will last for between three and four hours. Bob Webber PictureTel Corporation

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subscribe
by Carl Yang 17 Nov '98

17 Nov '98

Carl Yang carl(a)shoretel.com

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Re: Usage of CallID in H.323v2 for rerouted (diverted, transferre d,.. .) calls
by Santo Wiryaman 17 Nov '98

17 Nov '98

Hi Karl, Chris: >From the very beginning there was Conference ID (CID) that was created to identify a "conference". There was also CRV which is used to associate call signalling. messages. However, since the RAS and H.225 CRV values are independent, a GK may not be able to associate the ARQ pair with the Setup message. The in version 2, the Call ID was created to associate the H.225.0 messages with the call. Karl is now proposing to add CallLegID to identify the leg of the call. It seems clear that as soon as we define a new ID to identify a particular thing, there is a need to identify yet another thing related to the thing. I am not saying that a new field called the CallLegID is a bad thing. However, perhaps we need to step back and think what is it that we are really trying to get a handle of. I propose that what we are dealing here is a call, a conference, and the connection legs to the call. A word can mean different things to different people, and the H.323 spec does not necessarily help either. My favorite definitions so far came from the ECTF CTI Encyclopedia Volume 3, p 10: Device - And endpoint Call - The association of one or more devices Connection - A device's representation in a given call Consider the example of device D1 in a call with device D2: D1 --------- C1 --------- D2 Call C1 associates devices D1 and D2. Call C1 consists of 2 connections: D1C1 and D2C2. H.450.2 (Call Transfer SS), for example, uses a similar notation. CT with consultaion figure 7/H.450.2 can be redrawn in ASCII art as: Before Service: A ----------- C1 ----------- B C (idle) Consultation: A ----h----- C1 -----h----- B ( A puts B on hold) A ----------- C2 ------------ C ( A makes a new call to C) Transfer A ----t----- C1 -----t----- B ( A transfers B to C) A ----t----- C2 -----t----- C After Service: A (idle) B ----------- C3 ----------- C The question is how do CID, CRV, CallID, CallLegID map to the above model. CID somewhat maps to the ID of the calls, e.g. C1, C2, C3. It breaks down, though, if an MCU calls out to A, B, C with the same CID. As far as the model goes, there are 3 calls: MCU ----------- C1 ----------- A MCU ----------- C2 ----------- B MCU ----------- C3 ----------- C As far as a device is concerned, the CRV is the ID for the connections. For a GK, however, the ID for the connections is (CRV plus the EndpointID). The ambiguity with CRV's is when an endpoint can make multiple calls. For example, A makes two simultaneous calls to B: 1. A sends ARQ to GK with CRV=1 2. A sends ARQ to GK with CRV=2 3. A sends Setup to GK with CRV= 17 4. A sends Setup to GK with CRV= 21 Since the CRV's of RAS and Q.931 are independent, the GK can not associate the Setup with the correct ARQ. Version 2 CallID was suppose to fix this since it associate the RAS and the Call Signalling for the same connection (i.e. connection leg). Section 7.5 of H.323v2 says that the CallID must be the same for the following call: A ----------- C1 ----------- B Specifically it says that the CallID of the AC1 connection must be the same as the BC1 connection and that in both connections, the RAS and Call Signalling messages CallID's must be the same. Karl is proposing that in the case of a rerouted call, as described in Fig 19/H.323, the second Setup uses the same CallID. I agree that this is fine. However, in the case of a call transfer as described above, during the Consultation phase when A makes a new call to C, the CallID for the AC2 connection leg shall be diferent than the AC1 leg, because by definition, this is a new call. Would you agree with that Karl? Otherwise, if the CallID of AC1 and AC2 are the same, then we'll make it impossible for the GK to match the RAS and CallSignalling messages once again. Or is this why you are proposing a new CallLeg field? Finally, I have a question on the After Service phase of the call transfer operation. At this phase we have a new call (C3) with CC3 and BC3 connections. If the SS-CT was done on the GK w/gk-routed model, the H.225 connections on CC3 and BC3 could remain connected during the whole procedure. At the end, though, we end up with a call (C3) and two different CallID's on CC3 (which was the same as AC2) and on BC3 (which was the same as AC1). This is permitted and should not cause any misoperations, correct? Should this be pointed out in an implementor's guide? A similar situation is true today with meet-me MCU's. In theory, all the calls in the same conference would use the same CID. However, in a meet-me MCU, the endpoints initiates the call each generating unique CID's. There are procedures to change CID's during a call, but I don't know if that happens in the field. Regards, Santo Wiryaman VideoServer Inc. > -----Original Message----- > From: Klaghofer Karl PN VS LP3 [SMTP:Karl.Klaghofer@VS.SIEMENS.DE] > Sent: Monday, November 16, 1998 8:34 AM > To: ITU-SG16(a)mailbag.cps.intel.com > Subject: AW: Usage of CallID in H.323v2 for rerouted (diverted, > transferre d,.. .) calls > > Chris, > > Thanks for your comment. > > CRV is unique just at one signalling link of a call (e.g. between EP A and > GK; and may be different between GK and EP2 of the same call) . > > Since CallID may be preserved when calls are redirected (incl. transfer, > forward,...), the CallID actually identifies the call scenario and not > exactly one call. I think this is fine. > > A CallLegID would be a new identifier that is somehow in between CallID > and > CRV by identifying exactly one call (or call attempt) between two > endpoints. > We might think about for H.225.0v3. > > Regards, > Karl > > > -----Ursprüngliche Nachricht----- > > Von: Chris Purvis [SMTP:CPurvis@MADGE.COM] > > Gesendet am: Montag, 16. November 1998 12:52 > > An: ITU-SG16(a)mailbag.cps.intel.com > > Betreff: Re: Usage of CallID in H.323v2 for rerouted (diverted, > > transferre d,.. .) calls > > > > Karl, > > > > I agree with your comments on CallID being preserved when calls are > > transferred. However... > > > > > > >As an alternative, we might add a new multilevel CallID (e.g. > > >to H.225.0 v3) > > >that consists of an identifier that indicates the "overal > > >call" and a second > > >identifier that indicates the call leg. > > > Isn't this the CRV, that's always been there? > > > Regards, > > Chris > > -- > > Dr Chris Purvis - Senior Development Engineer, WAVE CC Software > > Madge Networks Ltd, Wexham Springs, Framewood Road, Wexham, Berks. > > Phone:+44 1753 661359 email: cpurvis(a)madge.com

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