January 1999 - sg16-avd - lists.packetizer.com

Re: Relationship of H.323 and H.245 versions
by Pete Cordell 20 Jan '99

20 Jan '99

Gary, Chris and others, To try an clear this issue up I propose that the text below should be added to the implementors' guide and be rolled into H.323 V3. Let me know what you think (No comment will probably mean OK by me as per normal, but will probably have to put a contribution into next meeting anyway.) Proposed text: In H.323 version 2 there is conflicting advice on which versions of H.245 should be used with versions H.323. The summary states that H.323 version 2 should use H.225 version 2 and H.245 version 3. However, in the Normative References section it states that implementors are "...encouraged to investigate the possibility of applying the most recent edition of the Recommendations...". To clarify this, the following section is published in the implementors' guide as a clarification to H.323 version 2 and a similar paragraph will be added to H.323 Version 3. The Relationship of H.323 versions to H.225.0 and H.245 versions Entities claiming compliance to H.323 Version 2 shall implement all mandatory features in this recommendation and in H.225.0 version 2. An H.225.0 version 2 implementation is identified by the protocolIdentifier in the messages being set to {itu-t (0) recommendation (0) h (8) 2250 version (0) 2}. H.323 version 2 compliant entities shall implement H.245 version 3 or later. An H.245 version 3 implementation is identified by the protocolIdentifier in the terminalCapabilitySet message being set to {itu-t (0) recommendation (0) h (8) 245 version (0) 3}. Implementations must also be aware that, due to the procedures for 'Third party initiated pause and re-routing,' they may be connected to different versions of H.245 at different times during the life of the call. Therefore, under no circumstances shall an entity infer the version of the H.245 implementation from the protocolIdentifier carried in H.225.0 messages. And as a word version to help editors! Regards, Pete ================================= Pete Cordell BT Labs E-Mail: pete.cordell(a)bt-sys.bt.co.uk Tel: +44 1473 646436 Fax: +44 1473 645499 ================================= >---------- >From: Gary A. Thom[SMTP:gthom@delta-info.com] >Sent: 14 January 1999 19:02 >To: Pete Cordell >Subject: Re: Relationship of H.323 and H.245 versions > >Pete, > >This is a very good question, and one which may need to be answered by bigger >minds than mine. > >I do not have a definitive answer, but my opinion is: > >In order to claim compliance with H.323 V2, an entity shall implement at >lease H.225.0 V2 and >H.245 V3. This would allow an advanced H.323V2 terminal to incorporate H.245 >V4. > >However, as part of the H.225.0 and H.245 message exchange >(protocolIdentifier parameter), each >entity will be aware of the version of the entity which it is communicating >with. > >The receiver, "shall not malfunction or be adversely affected by receiving >H.245 messages it does >not recognize". Does this include messages from future versions??? Or does >the transmitter have to >know that it is talking to a version X entity, so it cant send any messages >from versions greater >than X??? > >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(a)delta-info.com >------------------------------------------------------ > begin 600 H323-Versions.doc MT,\1X*&Q&N$`````````````````````/@`#`/[_"0`&```````````````! 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2 1

Re: Notice of the Monterey meeting
by Sakae OKUBO 20 Jan '99

20 Jan '99

Dear Henri Maenpaa, > I'm trying to prepare a brief proposal to one of the H.225's annex > concerning 'voice coding'. > > It will be just a brief text about transferring GSM in H.323, just like > there already is e.g. G.723 represented. APC-1491 has been allocated to your contribution. 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 ***********************************************************

1 0

H.323 Security Issues
by Avikal Jain 18 Jan '99

18 Jan '99

Hi all, I am studying the security issues related to H.323 proxy. I need to find out more about the security issues posed by a H.323 proxy. I believe that the H.323 proxies such as those developed by TIS, Checkpoint and Cisco, although permitting H.323 traffic, are not considered very secure. What are the possible security hazards one must be aware of? Thanks. Avikal Jain Center for Development of Advanced Computing, Pune 411007, India. e-mail: avikal(a)usa.net

1 0

Re: Ambiguity in H.225.0 Appendix D
by Jim Toga 18 Jan '99

18 Jan '99

Chris, The problem is that it is a _client_ issue as much as a GK issue. The (enterprise) site administrator, wants to be assured that no rougue client will get on the network and simple start conferencing... If he has 'compliant' stacks than he can be assured that GK policy will be followed.... Regards, jimt. At 05:59 PM 1/18/99 -0000, you wrote: >Jim, > >Surely this could be left as a configuration option for the administrator. >If he doesn't want the assurance you describe, why shouldn't he be allowed >to configure it out of suitably-written gatekeepers? I would expect it to >be an unusual thing to want to do, bearing in mind your comments, but is it >the place of the standard to deny such possibilities? > >Chris > >> -----Original Message----- >> From: Jim Toga [mailto:jim.toga@INTEL.COM] >> Sent: 15 January 1999 1:47 >> To: ITU-SG16(a)MAILBAG.INTEL.COM >> Subject: Re: Ambiguity in H.225.0 Appendix D >> >> >> There is a point behind having a GK respond to all GRQ messages. >> >> The administrator must be able to be assured that >> unauthorized endpoints >> (with compliant stacks) do not conference. H.323 stipulates >> that _if_ GKs >> are present, then endpoints must use them.... so if the GK >> are present and >> none of them will allow a particular endpoint to register - >> then it is not >> supposed to make/receives H.323 calls. >> >> The endpoint on the other hand, must be able to reasonably detect the >> difference between the complete absence of GKs and the >> absence of 'their' >> GK (especially if some specific control/policy is in place). >> >> If the GK receives a GRQ, it must respond with a (directed) >> GCF or GRJ. >> >> jimt. >> >> >> At 10:55 AM 1/13/99 -0800, you wrote: >> >Hi, >> > >> >This is wrt the second problem in the attached mail. >> >Chris Purvis mentioned that GK needs to know whether >> >a GRQ or LRQ is received via multicast or unicast so that >> >the response could be different. >> > >> >Actually, H.323 V2 specifies different multicast and unicast >> >responses only in case of LRQ. In case of GRQ, spec specifically >> >mentions that even in multicast case a response shall be >> >given (Section 7.2.1 para three which _only_ talks about >> >multicast GRQs). >> > >> >I believe spec should not mandate a GK to respond to >> >a multicast GRQ. It should be left to the implementor whether >> >a response should be sent out to a multicast GRQ or not. >> >The GK may have some additional information like redirecting >> >the endpoint to a different GK with altGKInfo etc, otherwise it >> >is just plain waste of bandwidth to mandate GK's to respond to >> >multicast GRQ's. The endpoints would time out if they >> >haven't received a single GCF. >> > >> >May be the following line in para 3 of section 7.2.1: >> > >> >"If a Gatekeeper does not want the endpoint to register to it, >> >it shall return Gatekeeper Reject (GRJ)" >> > >> >should be changed to something like: >> > >> >"On receiving a multicasted GRQ, if a Gatekeeper does not want >> >the endpoint to register to it, it MAY return Gatekeeper >> >Reject (GRJ)" >> > >> >Comments? >> > >> >Regards, >> >-Kishore. >> > >> > >> >> -----Original Message----- >> >> From: Mailing list for parties associated with ITU-T Study Group 16 >> >> [mailto:ITU-SG16@mailbag.cps.intel.com]On Behalf Of Chris Purvis >> >> Sent: Thursday, January 07, 1999 9:33 PM >> >> To: ITU-SG16(a)mailbag.cps.intel.com >> >> Subject: Ambiguity in H.225.0 Appendix D >> >> >> >> >> >> We have had an ambiguity show up during interoperability >> >> testing, which >> >> I would like clarified by means of the implementer's guide >> and future >> >> versions of the standard. Any objections, please shout in >> the usual >> >> way! >> >> >> >> The problem comes in 19.1.1.1 where UDP port numbers are >> defined. The >> >> standard currently (I'm looking at version 2) says: >> >> Gatekeeper UDP Discovery Port 1718 >> >> Gatekeeper UDP Registration and Status Port 1719 >> >> >> >> There are two problems with this. The first is that it >> >> implies that the >> >> LRQ message (which is nothing to do with discovery) always >> needs to be >> >> sent to port 1719, which is a problem for multicast LRQs, >> because only >> >> one IP address and port number pair has been registered with >> >> the IETF - >> >> 224.0.1.41:1718. >> >> >> >> The second problem is, if anything, more subtle... The >> standard also >> >> seems to imply by the above that GRQ, which is a discovery message, >> >> should always be sent to port 1718, whether it is sent to the >> >> multicast >> >> discovery port or not. >> >> The reason this is a problem is that gatekeepers need to >> know whether >> >> these messages (GRQ and LRQ) have arrived by multicast or >> by unicast, >> >> because the failure response is different in the two cases >> >> (no response >> >> to a multicast xRQ, but xRJ response to a unicast xRQ). The only >> >> indication that most IP stacks give as to how a message >> has arrived is >> >> by a port number, however, so if all GRQs appear to port >> 1718 (and all >> >> LRQs to port 1719), there is no way for the gatekeeper to >> tell whether >> >> the message arrived by unicast or multicast. >> >> >> >> Common (but not universal - at least in products under >> development!) >> >> usage, driven by these practical considerations, seems to >> be that the >> >> most common implementations send both sorts of multicast >> addresses to >> >> the registered address - 224.0.1.41:1718, and unicast GRQ and LRQ >> >> messages to port 1719 (unless there is some private arrangement >> >> specifying other special usage). >> >> >> >> My suggestion is that this common usage is standardised, >> initially via >> >> the implementer's guide, and then when appropriate in future >> >> versions of >> >> H.225.0. >> >> >> >> Regards, >> >> Chris >> >> >> > >> +1-503-264-8816(voice) Intel - Hillsboro, OR >> mailto:jim.toga@intel.com mailto:james.toga@ties.itu.int >> PGP keyID 36 07 86 49 7D 74 DF 57 50 CB BA 32 08 9C 7C 41 >> > +1-503-264-8816(voice) Intel - Hillsboro, OR mailto:jim.toga@intel.com mailto:james.toga@ties.itu.int PGP keyID 36 07 86 49 7D 74 DF 57 50 CB BA 32 08 9C 7C 41

1 0

Re: Ambiguity in H.225.0 Appendix D
by Chris Purvis 18 Jan '99

18 Jan '99

Jim, Surely this could be left as a configuration option for the administrator. If he doesn't want the assurance you describe, why shouldn't he be allowed to configure it out of suitably-written gatekeepers? I would expect it to be an unusual thing to want to do, bearing in mind your comments, but is it the place of the standard to deny such possibilities? Chris > -----Original Message----- > From: Jim Toga [mailto:jim.toga@INTEL.COM] > Sent: 15 January 1999 1:47 > To: ITU-SG16(a)MAILBAG.INTEL.COM > Subject: Re: Ambiguity in H.225.0 Appendix D > > > There is a point behind having a GK respond to all GRQ messages. > > The administrator must be able to be assured that > unauthorized endpoints > (with compliant stacks) do not conference. H.323 stipulates > that _if_ GKs > are present, then endpoints must use them.... so if the GK > are present and > none of them will allow a particular endpoint to register - > then it is not > supposed to make/receives H.323 calls. > > The endpoint on the other hand, must be able to reasonably detect the > difference between the complete absence of GKs and the > absence of 'their' > GK (especially if some specific control/policy is in place). > > If the GK receives a GRQ, it must respond with a (directed) > GCF or GRJ. > > jimt. > > > At 10:55 AM 1/13/99 -0800, you wrote: > >Hi, > > > >This is wrt the second problem in the attached mail. > >Chris Purvis mentioned that GK needs to know whether > >a GRQ or LRQ is received via multicast or unicast so that > >the response could be different. > > > >Actually, H.323 V2 specifies different multicast and unicast > >responses only in case of LRQ. In case of GRQ, spec specifically > >mentions that even in multicast case a response shall be > >given (Section 7.2.1 para three which _only_ talks about > >multicast GRQs). > > > >I believe spec should not mandate a GK to respond to > >a multicast GRQ. It should be left to the implementor whether > >a response should be sent out to a multicast GRQ or not. > >The GK may have some additional information like redirecting > >the endpoint to a different GK with altGKInfo etc, otherwise it > >is just plain waste of bandwidth to mandate GK's to respond to > >multicast GRQ's. The endpoints would time out if they > >haven't received a single GCF. > > > >May be the following line in para 3 of section 7.2.1: > > > >"If a Gatekeeper does not want the endpoint to register to it, > >it shall return Gatekeeper Reject (GRJ)" > > > >should be changed to something like: > > > >"On receiving a multicasted GRQ, if a Gatekeeper does not want > >the endpoint to register to it, it MAY return Gatekeeper > >Reject (GRJ)" > > > >Comments? > > > >Regards, > >-Kishore. > > > > > >> -----Original Message----- > >> From: Mailing list for parties associated with ITU-T Study Group 16 > >> [mailto:ITU-SG16@mailbag.cps.intel.com]On Behalf Of Chris Purvis > >> Sent: Thursday, January 07, 1999 9:33 PM > >> To: ITU-SG16(a)mailbag.cps.intel.com > >> Subject: Ambiguity in H.225.0 Appendix D > >> > >> > >> We have had an ambiguity show up during interoperability > >> testing, which > >> I would like clarified by means of the implementer's guide > and future > >> versions of the standard. Any objections, please shout in > the usual > >> way! > >> > >> The problem comes in 19.1.1.1 where UDP port numbers are > defined. The > >> standard currently (I'm looking at version 2) says: > >> Gatekeeper UDP Discovery Port 1718 > >> Gatekeeper UDP Registration and Status Port 1719 > >> > >> There are two problems with this. The first is that it > >> implies that the > >> LRQ message (which is nothing to do with discovery) always > needs to be > >> sent to port 1719, which is a problem for multicast LRQs, > because only > >> one IP address and port number pair has been registered with > >> the IETF - > >> 224.0.1.41:1718. > >> > >> The second problem is, if anything, more subtle... The > standard also > >> seems to imply by the above that GRQ, which is a discovery message, > >> should always be sent to port 1718, whether it is sent to the > >> multicast > >> discovery port or not. > >> The reason this is a problem is that gatekeepers need to > know whether > >> these messages (GRQ and LRQ) have arrived by multicast or > by unicast, > >> because the failure response is different in the two cases > >> (no response > >> to a multicast xRQ, but xRJ response to a unicast xRQ). The only > >> indication that most IP stacks give as to how a message > has arrived is > >> by a port number, however, so if all GRQs appear to port > 1718 (and all > >> LRQs to port 1719), there is no way for the gatekeeper to > tell whether > >> the message arrived by unicast or multicast. > >> > >> Common (but not universal - at least in products under > development!) > >> usage, driven by these practical considerations, seems to > be that the > >> most common implementations send both sorts of multicast > addresses to > >> the registered address - 224.0.1.41:1718, and unicast GRQ and LRQ > >> messages to port 1719 (unless there is some private arrangement > >> specifying other special usage). > >> > >> My suggestion is that this common usage is standardised, > initially via > >> the implementer's guide, and then when appropriate in future > >> versions of > >> H.225.0. > >> > >> Regards, > >> Chris > >> > > > +1-503-264-8816(voice) Intel - Hillsboro, OR > mailto:jim.toga@intel.com mailto:james.toga@ties.itu.int > PGP keyID 36 07 86 49 7D 74 DF 57 50 CB BA 32 08 9C 7C 41 >

1 0

None
by Patrik Suter 18 Jan '99

18 Jan '99

subscribe patrik.suter(a)bluewin.ch

2 1

Re: Ambiguity in H.225.0 Appendix D
by Kishore Babu Ramisetty 14 Jan '99

14 Jan '99

Hi, This is wrt the second problem in the attached mail. Chris Purvis mentioned that GK needs to know whether a GRQ or LRQ is received via multicast or unicast so that the response could be different. Actually, H.323 V2 specifies different multicast and unicast responses only in case of LRQ. In case of GRQ, spec specifically mentions that even in multicast case a response shall be given (Section 7.2.1 para three which _only_ talks about multicast GRQs). I believe spec should not mandate a GK to respond to a multicast GRQ. It should be left to the implementor whether a response should be sent out to a multicast GRQ or not. The GK may have some additional information like redirecting the endpoint to a different GK with altGKInfo etc, otherwise it is just plain waste of bandwidth to mandate GK's to respond to multicast GRQ's. The endpoints would time out if they haven't received a single GCF. May be the following line in para 3 of section 7.2.1: "If a Gatekeeper does not want the endpoint to register to it, it shall return Gatekeeper Reject (GRJ)" should be changed to something like: "On receiving a multicasted GRQ, if a Gatekeeper does not want the endpoint to register to it, it MAY return Gatekeeper Reject (GRJ)" Comments? Regards, -Kishore. > -----Original Message----- > From: Mailing list for parties associated with ITU-T Study Group 16 > [mailto:ITU-SG16@mailbag.cps.intel.com]On Behalf Of Chris Purvis > Sent: Thursday, January 07, 1999 9:33 PM > To: ITU-SG16(a)mailbag.cps.intel.com > Subject: Ambiguity in H.225.0 Appendix D > > > We have had an ambiguity show up during interoperability > testing, which > I would like clarified by means of the implementer's guide and future > versions of the standard. Any objections, please shout in the usual > way! > > The problem comes in 19.1.1.1 where UDP port numbers are defined. The > standard currently (I'm looking at version 2) says: > Gatekeeper UDP Discovery Port 1718 > Gatekeeper UDP Registration and Status Port 1719 > > There are two problems with this. The first is that it > implies that the > LRQ message (which is nothing to do with discovery) always needs to be > sent to port 1719, which is a problem for multicast LRQs, because only > one IP address and port number pair has been registered with > the IETF - > 224.0.1.41:1718. > > The second problem is, if anything, more subtle... The standard also > seems to imply by the above that GRQ, which is a discovery message, > should always be sent to port 1718, whether it is sent to the > multicast > discovery port or not. > The reason this is a problem is that gatekeepers need to know whether > these messages (GRQ and LRQ) have arrived by multicast or by unicast, > because the failure response is different in the two cases > (no response > to a multicast xRQ, but xRJ response to a unicast xRQ). The only > indication that most IP stacks give as to how a message has arrived is > by a port number, however, so if all GRQs appear to port 1718 (and all > LRQs to port 1719), there is no way for the gatekeeper to tell whether > the message arrived by unicast or multicast. > > Common (but not universal - at least in products under development!) > usage, driven by these practical considerations, seems to be that the > most common implementations send both sorts of multicast addresses to > the registered address - 224.0.1.41:1718, and unicast GRQ and LRQ > messages to port 1719 (unless there is some private arrangement > specifying other special usage). > > My suggestion is that this common usage is standardised, initially via > the implementer's guide, and then when appropriate in future > versions of > H.225.0. > > Regards, > Chris >

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Re: Ambiguity in H.225.0 Appendix D
by Rajesh Patwardhan 14 Jan '99

14 Jan '99

Just FYI on multicast/unicast taken from Stevens book: "...Some applications also bind the multicast address to the socket, in addition to the port. This prevents any other datagrams that might be received for that port from being delivered to the socket. Historically, Berkeley-derived implementations only require that some socketon the host join the mcast group, not necessarily the socket that binds the port and then receives the mcast datagram. There is a potential, however, with these implementations for mcast datagrams to be delivered to the applications that are not mcast aware. Newer mcast kernels now require that the process bind the port and set any mcast socket option for the socket, the latter being an indication that the application is mcast aware. Solaris 2.5 differs slightly and only delivers received mcast datagrams to a socket that has both joined the group and bound the port. For portability, all mcast apps should join a group and bind the port. Some older mcast-capable hosts do not allow the bind of mcast addr to a socket. For portability an application may wish to ignore a bind error for a mcast address...." ----rrp

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Re: Relationship of H.323 and H.245 versions
by Chris Purvis 14 Jan '99

14 Jan '99

Pete, The answer to your direct question is, I believe, a) - but I don't see why it needs to be. In some senses an H.323 version is defined by a combination of an H.225.0 version and an H.245 version. You may or may not discover the second of these pieces of information from another endpoint, in particular if you're using faststart (it seems only to be communicated in a terminalCapabilitySet message). How you'd discover an H.323 version by any other means I don't know! There's also the issue that when people say they support version n, they do not necessarily mean that they support ALL the features of that version (it generally simply means that all the ASN.1 is there); also there may be cases where different signalling channels follow different routes (eg a version 28 gatekeeper or proxy routing a version 1 endpoint's (or vice versa) H.225 but not H.245) - so it's dangerous to make assumptions on the basis of knowledge of another party's version. Is there something particular that you're trying to achieve? If there's a reason for it, we need to think about how to put more versioning information in to the standards. I'd add the further question: Is there any point at which we can assume support of some of the H.450 supplementary services? Or H.235 security? I doubt it... Regards, Chris > -----Original Message----- > From: Pete Cordell [mailto:pete.cordell@BT-SYS.BT.CO.UK] > Sent: 14 January 1999 2:59 > To: ITU-SG16(a)MAILBAG.INTEL.COM > Subject: Relationship of H.323 and H.245 versions > > > Gary, > > As H.323 editor can you comment on which of the following > statements is > more correct: > > a) H.323 version 2 can be used with H.245 version 3 ONLY > b) H.323 version 2 can be used with H.245 version 3 OR LATER. > > My view is that it is undesirable to have to up-issue H.323 to a new > version if all you want to do is make use of new features in H.245. > Also, as part of third party re-routing, in the future it may > occur that > an H.323 version 3 endpoint originally connected to another H.323 > version 3 endpoint will end up being connected to the H.245 from an > H.323 version 2 endpoint. Hence assuming that the H.323 and H.245 > versions are locked together does not work. However, I'm not sure if > this aligns with the groups understanding. Do you have any comments? > > Regards, > > Pete > > ================================= > Pete Cordell > BT Labs > E-Mail: pete.cordell(a)bt-sys.bt.co.uk > Tel: +44 1473 646436 > Fax: +44 1473 645499 > ================================= >

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Relationship of H.323 and H.245 versions
by Pete Cordell 14 Jan '99

14 Jan '99

Gary, As H.323 editor can you comment on which of the following statements is more correct: a) H.323 version 2 can be used with H.245 version 3 ONLY b) H.323 version 2 can be used with H.245 version 3 OR LATER. My view is that it is undesirable to have to up-issue H.323 to a new version if all you want to do is make use of new features in H.245. Also, as part of third party re-routing, in the future it may occur that an H.323 version 3 endpoint originally connected to another H.323 version 3 endpoint will end up being connected to the H.245 from an H.323 version 2 endpoint. Hence assuming that the H.323 and H.245 versions are locked together does not work. However, I'm not sure if this aligns with the groups understanding. Do you have any comments? Regards, Pete ================================= Pete Cordell BT Labs E-Mail: pete.cordell(a)bt-sys.bt.co.uk Tel: +44 1473 646436 Fax: +44 1473 645499 =================================

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