May 2002 - sg16-avd - lists.packetizer.com

H.450.1 ASN.1 interoperability issue
by Mark Brown 10 May '02

10 May '02

We've been experiencing some fairly serious interoperability problems with some systems due to confusion over what exactly the ASN.1 for H.450.1 is and were hoping someone could clarify things for us. The problem stems from section 6.6.1.3 of the V4 implementors guide which adds a note below table 4: In the Invoke APDU, the invokeID is an INTEGER constrained by a PER-visible constraint (InvokeIdSet = 0..65535) and is therefore encoded as a *constrained* INTEGER (16 bits, no length field). In the ReturnResult and ReturnError APDUs, however, the invokeID is encoded as an *unconstrained* integer (with explicit length field) because the applicable constraint... is not PER-visible. However, in H.450.1 table 3 (on page 8) defines InvokeIdSet to be: InvokeIdSet INTEGER ::= {InvokeIds,...} InvokeIDs ::= INTEGER (0..65535) which does not gel with the text in the IG and causes interoperability issues since the two versions of the ASN.1 for InvokeIdSet are not encoded identically. This text appears to be unchanged from the prepublished edition on Packetizer. Our understanding of the text added in the IG is that the intent was to emphasise that the encoding of the invokeID is not consistent between the various APDUs and that the no change to the ASN.1 was intended. This is particularly the case since the IG doesn't modify table 3 as would be expected if it were correcting the ASN.1 there. Others read things differently and are using the definition of InvokeIdSet given in the IG. What is the intention here? If the intention is to redefine the ASN.1 then some clarification as to why this was done would be very much appreciated.

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Re: "Early media" with fast connect
by Douglas Clowes 09 May '02

09 May '02

Frank, Actually, media with PI=8 (inband tones and announcements) is probably a good thing, and I would expect it. The intention of "prepared to receive" is because it could receive valid media before it knows if it's associated with a connect or progress (PI=8) so it should play it. Indeed, this will often be the case over real networks, where RTP media is expedited ahead of regular TCP traffic. The intention is to not clip the media. The MG, being a "dumb" box should probably be provided with a "trigger" to stop local ringback on receipt of first media, and/or notify the MGC of "first media received". The MGC thus provides the logic of when, or if, to stop the local ringback. As for the "mediaWaitForConnect", what if there never will be a Connect? I assume that an announcement server, which sends Progress(PI=8) and plays media, will send media without sending Connect. The receiving endpoint should play it. The normal thing would be to establish media in the backward direction before sending Setup, so media would be played, and connect the forward media direction on receipt of Connect. Regards, Douglas At 11:42 02/05/2002 +0200, frank.derks(a)PHILIPS.COM wrote: >>>> <fontfamily><param>Courier</param>Ernst,</fontfamily> <fontfamily><param>Courier</param>obviously, conflict situations could arise if both a Progress indicator #1 or #8, in</fontfamily> <fontfamily><param>Courier</param>combination with actual media being transmitted by the called endpoint would occur, </fontfamily> <fontfamily><param>Courier</param>but this does not seem to be a likely event. </fontfamily> <fontfamily><param>Courier</param>The fact the calling endpoint "must be prepared to receive media" is not the same</fontfamily> <fontfamily><param>Courier</param>thing as "expecting to receive media". You have a valid point, though, that at some</fontfamily> <fontfamily><param>Courier</param>stage a switch-over from locally provided media to the media provided by the called</fontfamily> <fontfamily><param>Courier</param>endpoint must occur. When this occurs is governed by the Progress indicator and the</fontfamily> <fontfamily><param>Courier</param>mediaWaitForConnect.</fontfamily> <fontfamily><param>Courier</param>Regards,</fontfamily> <fontfamily><param>Courier</param>Frank </fontfamily> <fontfamily><param>Courier</param>Dear experts, there seems to be a possible conflict with early media during call establishment using fast connect. </fontfamily> <fontfamily><param>Courier</param>Clause 8.1.7.1 of H.323 clearly says that the calling endpoint must be prepared to receive media right away on the ports it indicated in fastStart, and that the called endpoint may start transmitting media as soon as it accepts a fastStart proposal (unless, of course, the calling endpoint indicated also "mediaWaitForConnect"). This is independent of any Progress indicator.</fontfamily> <fontfamily><param>Courier</param>Clause 8.1.7.4, on the other hand, requires that the calling endpoint provides tones like ringback locally if it did not receive a Progress indicator #1 or #8. So the calling endpoint is obliged to interrupt/ignore possible media streams from the called endpoint and replace them with its own tones. Isn't this a conflict situation?</fontfamily> <fontfamily><param>Courier</param>I would like to hear your opinion or any experience from implementations. </fontfamily> <fontfamily><param>Courier</param>Kind Regards, Ernst Horvath Siemens AG </fontfamily> <<<<<<<<

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Documents for the Bruges meeting
by OKUBO Sakae 09 May '02

09 May '02

Dear Q.D, F, G, 2-5 experts, I have uploaded the attached liaison statements at the following place: using browser http://standard.pictel.com/ftp/avc-site/0206_Bru/ using ftp tool ftp://standard.pictel.com/avc-site/0206_Bru/ Best regards, OKUBO Sakae ********************************************************* Global Information and Telecommunication Institute (GITI) Waseda University 29-7 Waseda University Bldg. 1-3-10 Nishi-Waseda, Shinjuku-ku, Tokyo 169-0051 Japan e-mail: okubo(a)giti.waseda.ac.jp Tel: +81 3 3204 8194 Fax: +81 3 5286 3832 ********************************************************* Document List for the Bruges Joint Q.D, F, G, 2, 3, 4, 5 Rapporteurs $B!G (B Meeting (24-28 June 2002) AVD-number Questions Title Source AVD-2175 D, 2, 3, 4 PROPOSED NEW QUESTION ON "Syntax language for the support of PSTN/ISDN services within IP session control protocols" SG11 AVD-2176 G Liaison Statement on Multimodality and Multimediality - Ref: A morphological model for multi-sensory technologies and coherence in security SG17 AVD-2177 G, ets Response to Liaison Statement to ITU-T Study Groups on Telecommunication Reliability and Security SG17 AVD-2178 ets Response to Liaison Statement to draft new Question Q.ets/16 on Emergency Telecommunications Service (ETS) SG17 AVD-2179 G Liaison on the Compendia of Communication Systems Security SG17 AVD-2180 All Liaison statement on the User Requirements Notation (URN) SG17 AVD-2181 2, 3 Liaison Statement to Working Parties 6E, 6S and 8A , Joint Task Group 1-6-8-9, and ITU-T Study Groups 9, 13 and 16 on the Sixth revision of the working document for diagrammatic interrelations of Recommendations for interactive broadcasting services and their summaries ITU-R Working Party 6M AVD-2182 F Consent of Draft New Recommendation M.2301 (ex-M.23ip) - PERFORMANCE OBJECTIVES AND PROCEDURES FOR provisioning AND MAINTENANCE OF ip-based networks Working Party 1/4 (Designations, Performance and Test Equipment) AVD-2183 3 CLARIFICATIONS TO H.246 ANNEX C SG 11 (Q11/11) AVD-2184 All Consent of M.3030, telecommunications Markup Language (tML) Framework SG 4 AVD-2185 ets Response to Study Group 16 Liaison on Draft New Question Qets/16 for Emergency Telecommunications Service (ETS) SG 4 AVD-2186 ets Response to SG16 Liaison on International Emergency Services SG 4 AVD-2187 F Response to SG 16 on Use of the CORBA in the TMN WP 4/4, Geneva, 8 $B%_ (B 19 April 2002 AVD-2188 All SG 4 Report and Request in its role as Lead SG on TMN SG 4 (Geneva, 8 $B%_ (B 19 April 2002) AVD-2189 2, 3, F Progress of the discussion on generic end-to-end QoS service requirements SG 11 AVD-2190 D, ets International Emergency Services SG 11 ----------

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Re: h235v2
by Euchner Martin ICN M SR 3 07 May '02

07 May '02

Wu, thanks for your good observation. I read the two paragraphs together in conjunction with chapter 7 and can indeed agree with you that there is a mismatch. As a resolution, I will prepare a proposal for the H.323 Implementors Guide that recommends to delete the incorrect "logical", as shown below. Assuming that the connection procedures in the previous clause (Connection establishment procedures) indicate a secure mode of operation, the negotiated handshake and authentication shall occur for the H.245 channel before any other H.245 messages are exchanged. If negotiated, any exchange of certificates shall occur using any mechanism appropriate for the H-Series terminal(s). After completing the securing of the H.245 channel, the terminals use the H.245 protocol in the same manner that they would in an insecure mode. With kind regards Martin Euchner. ----------------------------------------------------------------------- | Dipl.-Inf. Rapporteur Q.G/SG16 | Martin Euchner Phone: +49 89 722 55790 | Siemens AG.....................Fax : +49 89 722 47713 | ICN M SR 3 mailto:Martin.Euchner@icn.siemens.de | mailto:martin.euchner@ties.itu.int | Hofmannstr. 51 Intranet: http://intranet.icn.siemens.de/marketing/cs27/topics/security/ | D-81359 Muenchen Internet: http://www.siemens.de/ | __________________ | Germany ----------------------------------------------------------------------- -----Original Message----- From: wu.yongming(a)ZTE.COM.CN [mailto:wu.yongming@ZTE.COM.CN] Sent: Friday, April 26, 2002 5:15 AM To: ITU-SG16(a)echo.jf.INTEL.COM Subject: h235v2 hi,all experts is the following i marked by <<<>>> a error? i think it should possibly be H.245 control channe. 8.1 Secure H.245 channel operation Assuming that the connection procedures in the previous clause (Connection establishment procedures) indicate a secure mode of operation, the negotiated handshake and authentication shall occur for the <<<H.245 logical channel>>> before any other H.245 messages are exchanged. If negotiated, any exchange of certificates shall occur using any mechanism appropriate for the H-Series terminal(s). After completing the securing of the H.245 channel, the terminals use the H.245 protocol in the same manner that they would in an insecure mode. special to paul,because i am not sure this mail can get to the maillist,so i have send a copy to your address.if it is a trouble,please forgive me about that. regards, wu.y.m

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FW: Question about the use of alternateEndpoints in ACF
by Lyons, Terry 05 May '02

05 May '02

> H.225 v4 contains this text: > "7.11.2 AdmissionConfirm (ACF) > ... alternateEndpoints - A sequence of prioritized endpoint alternatives > for destCallSignalAddress or destinationInfo." > > The feature seems intended to support robustness through redundancy in > large networks, > where there may be more than one media gateway capable of serving the same > AdmissionRequest (ARQ). > This would accord with the support for alternate gatekeepers in H.323 v4: > "7.2.6 Alternate gatekeeper procedures > For the purposes of ensuring system availability, redundancy, and > scalability, the Gatekeeper may provide the RAS signalling function by > utilizing multiple physical or logical devices, referred to as Alternate > Gatekeepers. If the endpoint supports the Alternate Gatekeeper procedures > defined in this section, it should include the supportsAltGK field in the > GRQ and RRQ messages. > When an endpoint initiates communication with the Gatekeeper, it may be > provided with a list of Alternate Gatekeepers via the GCF message. If the > Gatekeeper does not respond to the subsequent RRQ, the endpoint shall > attempt to register with the Gatekeeper using the list of Alternate > Gatekeepers provided in the GCF. If no Alternate Gatekeeper responds, the > endpoint shall reinitiate the Gatekeeper discovery process." > > The problem is that there are no procedures specified for the use of > alternateEndpoints. > What is it that causes a caller to terminate its Setup attempt to one > destination and to initiate a Setup attempt to the next destination in > priority order? > > Can we presume that the critical event is receiving a ReleaseComplete? > Then how do we determine whether the release reason or cause code is final > (no further Setup should be sent) or not (try another destination)? > Some calls should end after an announcement is played, eg. "The number you > are calling has been disconnected", > and will never succeed no matter how many alternative endpoints are > attempted. > > If the intention of alternateEndpoints has already been clarified > somewhere, please point me to it and excuse my ignorance. > > - TLyons(a)sonusnet.com +1 732 625-3003 ext 212 >

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"Early media" with fast connect
by Horvath Ernst 02 May '02

02 May '02

Dear experts, there seems to be a possible conflict with early media during call establishment using fast connect. Clause 8.1.7.1 of H.323 clearly says that the calling endpoint must be prepared to receive media right away on the ports it indicated in fastStart, and that the called endpoint may start transmitting media as soon as it accepts a fastStart proposal (unless, of course, the calling endpoint indicated also "mediaWaitForConnect"). This is independent of any Progress indicator. Clause 8.1.7.4, on the other hand, requires that the calling endpoint provides tones like ringback locally if it did not receive a Progress indicator #1 or #8. So the calling endpoint is obliged to interrupt/ignore possible media streams from the called endpoint and replace them with its own tones. Isn't this a conflict situation? I would like to hear your opinion or any experience from implementations. Kind Regards, Ernst Horvath Siemens AG

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Fast Connect and terminating a call
by frank.derks＠PHILIPS.COM 02 May '02

02 May '02

Experts, 8.1.7.3/H.323 states that when Fast Connect is used to establish a call and no initiation of the H.245 procedures took place, the call _may_ be terminated by sending a RELEASE COMPLETE message. First of all, there is no reference to 8.1.7.3/H.323 in section 8.5/H.323, which describes the call termination procedure. This may lead the reader to believe that the procedures from 8.5/H.323 always apply and that the H.245 procedures must be initiated first (I.e. at a minimum the exchange of the terminal capability sets) to be able to send an EndSessionCommand message. Secondly, by stating that the call _may_ be terminated by sending a RELEASE COMPLETE message the reader may think that there are other ways of terminating the call. Obviously, there are (as described above, for example), but this would not seem the logical thing to do. Why not state that the call SHALL be terminated by sending a RELEASE COMPLETE message? Regards, Frank

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Re: "Early media" with fast connect
by frank.derks＠PHILIPS.COM 02 May '02

02 May '02

Ernst, obviously, conflict situations could arise if both a Progress indicator #1 or #8, in combination with actual media being transmitted by the called endpoint would occur, but this does not seem to be a likely event. The fact the calling endpoint "must be prepared to receive media" is not the same thing as "expecting to receive media". You have a valid point, though, that at some stage a switch-over from locally provided media to the media provided by the called endpoint must occur. When this occurs is governed by the Progress indicator and the mediaWaitForConnect. Regards, Frank Dear experts, there seems to be a possible conflict with early media during call establishment using fast connect. Clause 8.1.7.1 of H.323 clearly says that the calling endpoint must be prepared to receive media right away on the ports it indicated in fastStart, and that the called endpoint may start transmitting media as soon as it accepts a fastStart proposal (unless, of course, the calling endpoint indicated also "mediaWaitForConnect"). This is independent of any Progress indicator. Clause 8.1.7.4, on the other hand, requires that the calling endpoint provides tones like ringback locally if it did not receive a Progress indicator #1 or #8. So the calling endpoint is obliged to interrupt/ignore possible media streams from the called endpoint and replace them with its own tones. Isn't this a conflict situation? I would like to hear your opinion or any experience from implementations. Kind Regards, Ernst Horvath Siemens AG

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