Q10 Summary March 14 - 23, 1995 Geneva

(Complements of Communications Standards Review)

Question 10 is the part of ITU-T (previously CCITT) Study Group 8 where work on multi-point data conferencing is done. There is unfortunately a great deal of jargon in this report but the sciences are hierarchic and the jargon serves as pointers to previous work. I hope the more interested members of this conference will struggle through. Or e-mail questions to me.

Communications Standards Review Telecommunications is a technical journal (Ken Krechmer technical editor) reporting on formal standards work. CSR also reports on SG 15 (where H.32X video conferencing is done) and SG 14 (where V.34 was done) as well as related US technical committees TR-29, TR-30, TR-41. For additional information (this is the only plug) on CSR-T (subscriptions are $595.00 per year) contact E. Baskin tel: 415 856-8836 or 72540.113@compuserve.com.

The updated action plan is given in TD-2187. Electronic drafts of working documents are posted at the anonymous FTP site ftp.csn.net in subdirectory ConferTech . Correspondence may be conducted through the Email reflector t120-interest@world.sTD-.com. To join, send Email to t120-interest-request.

Interim meetings

31 July - 4 August 1995 Quebec City, Canada

18-29 September 1995 Paris, France (dates to be selected)

Note - The T.128 AVC editor will hold an ad hoc working meeting 8-10 May 1995 in Lexington, Kentucky, USA.

White documents finalizing T.120 and T.121 will be submitted by 15 October 1995 after review and approval of the members at the second interim meeting. A stable draft of T.128 and a stable revision of T.123 will be submitted as delayed documents for determination of Resolution No. 1 at the February 1996 meeting of SG 8.

Submitted for decision under Resolution No. 1 at this meeting

TD-2184 (amendment of COM 8-63-E) is the final draft Recommendation T.124 Generic Conference Control

TD-2185 and corrigendum (amendment of COM 8-66-E) is the final draft Recommendation T.126, Multipoint still image and annotation protocol

TD-2186 and corrigendum (amendment of COM 8-92-E)is the final draft Recommendation T.127, Multipoint binary file transfer protocol.

Submitted for determination of Resolution No. 1

TD-2183 is the abstracts of Recommendations T.120 and T.121 proposed for decision at the February 1996 meeting

Final drafts of these documents will be submitted as white contributions by 15 October 1995.

Recommendations and editors

Rec       Working Title                                Editor        

T.120     Data Protocols for Multimedia Conferencing   J. Boucher    

T.121     Generic Application Template                 T. Peers      

T.122     MCS Service Definition                       Rapporteur    

T.123     Audiovisual Protocol Stacks                  T. Lyons      

T.124     Generic Conference Control                   J. Bernstein  

T.125     MCS Protocol Specification                   T. Lyons      

T.126     Multipoint Still Image and Annotation        P. Romano     

T.127     Multipoint Binary File Transfer Protocol     T. Peers      

T.128     Audio Visual Control for Multipoint          J. Boucher    
          Multimedia Systems                                         

T.RES     Conference Reservation Protocols             B. Ceccaldi   

T.120 - Data Protocols for Multimedia Conferencing

D225, (J. Boucher BT) the proposed draft of T.120 was reviewed. Some of the description of MCS will be corrected. The overview of T.126 will be rewritten in line with the approved text. The section on AVC will caution that the work is not yet finalized. Bandwidth control will be deleted from the channel allocations of Annex A. Appendix 1 a model of the APIs will be removed entirely, since some consortia (e.g. IMTC, International Multimedia Teleconferencing Consortium URL=http://www.imtc.org/imtc) do not picture the API structure this way and the relationship between the data stack and the audio visual system is beyond the scope of this work..

The conformance requirements of section 10 will mandate MCS protocol version 2 (Packed Encoding Rules) as specified in T.125. T.126 will not be mandated as the only solution for application sharing, because its provisions for remote keyboard and pointing device events are optional and remain to be proven effective.

T.121 - Generic Application Template (T.GAT)

D226 (T. Peers, BT) draft T.GAT was reviewed. The editor noted that two work items remain from the interim meeting. The Application Resourse Manager (ARM) interface should be made precise enough so that T.126 and T.127 can reference T.121 in future editions and need not duplicate its content. And a tutorial should be added on the basics of channel, token, and registry use.

T.123 - Audiovisual Protocol Stacks

Q10/8 had intended (D216 Q10/8 meeting report October 1994 in Ipswich, UK) to draft enhancements to T.123 to utilize the data channel provided in H.22P (LBC videophone multiplex layer), by replacing the V.14 layer with the H.22P multiplex. Since stable text from Q2/15 for H.22P and H.24P(LBC videophone control channel) was not available in time for the SG 8 meeting, this did not happen. There are other challenging issues that remain to be discussed: Should the Q10/8 approach be the common denominator now present in T.123, which applies equally to the use of ASVD and DSVD, or should it be specialized to derive value from the Adaptation Layer of H.22P? If the latter, can Q10/8 eliminate redundancy of retransmission protocols? All that was agree is to encourage the use of V.8bis as an automated way to exchange modem and multiplexer capabilities and to select a common operating mode. Q10/8 does not intend to intrude on the discussions between SG 14 and SG 15 concerning harmonized operation of the multiplex layer.

TD-0057 from Q21/7 (OSI Application Layer) and Q22/7 (OSI Presentation and Session Layers) Rapporteurs meeting was accepted for information. TD-0057 discusses mechanisms to improve OSI upper layer protocol efficiency for applications such as G4 facsimile. To support work in Q15/8 on Cooperative Document Handling, Q10/8 wishes to complete the full seven-layer extended mode protocol stacks of T.123, which now are marked for further study. Ways of making OSI more efficient, through minimal OSI functionality or fast bytes draft recommendations from SG7 noted in TD-0057, appear relevant to this study.

TD-2148 (N. Kenyon BT Labs) This notes the need for a standard to govern signals flowing on a V.24 interface between personal computer and videotelephone for the purpose, among others, of conveying T.120 series protocol data. Local messages are envisioned for management of the data port interface, for call control, and for audiovisual control. Attached to TD-2148 is a proposal from Norwegian Telecom to use the low speed data (LSD) channel within H.221 framed signals to emulate V.24 attached modems. Also attached is a proposal from N. Kenyon proposing a videotelephone data port using T.120 in the MLP channel, suggesting that the MLP (multi layer protocol multiplexed into the H.221 frame structure) channel could operate up to 32kbit/s with the V.24 channel operating at 38.4kbit/s. The liaison reply from Q10/8 to SG15 (copy also to SG 14) is TD-2180. This notes that Q10/8 expects that they will use start/stop framing of Q.922 (LAP-F) data links and specify unused DLCIs for management and audio visual control.

This work is closely related to T.123 and will be handled for the time being as an Appendix. It merits further discussion whether the proposed interface should be a normative matter for standardization.

TD-2149 from SG15 Q2 is a request for comments on H.24X protocol stacks in the interest of harmonizing with that of the T.120 series. This suggests introducing X.224 Class 0 above the LAP-M to provide a X.214 service. In the Q10 meeting it was remarked that if Q2/15 is able to combine H.24X and H.24P (using LAP-M) into one document, a new issue will arise over harmonizing PSTN stacks. The liaison reply to SG 15 is TD-2181 which notes that Q10/8 will review the issue further.

T.124 - Generic Conference Control

The amendments included in D248 (Report of the Q10 meeting February 6-10, 1995 in Irvine, CA) and TD-2154 were reaffirmed. TD-2154 (Rapporteur) makes clear which side of a connection must act to avoid deadlock during conference establishment. Also it elevates the notion of multiport terminal (previously Terminal/MCU) midway between terminal and MCU and completes the conference establishment scenarios to cover connections between two multiport terminals. D257 from BT, Challenge-Response Passwording within T.124, was rewritten to detail the changes required, improved through further discussion, and adopted by a plurality vote. Discussion of D286 from France Telecom, Modification of call control elements, demonstrated a need for more explanation of network address in the service description, but no changes in the ASN.1 were ultimately required. The editorial corrections of TD-2152 (Rapporteur) were accepted.

The base document for T.124 is COM 8-63. The final revisions are presented in TD-2184. T.124 is submitted for decision under Resolution No. 1 at this meeting.

T.126 - Multipoint Still Image and Annotation Protocol

The amendments to T.126 included in D248 (Report of the Q10 meeting February 6-10, 1995 in Irvine, CA) were reaffirmed. The Rapporteurs proposal of TD-2153 to add support for 24-bit RGB JBIG encoded images was worked out to a small number of detailed changes, and these were accepted. The predominately editorial comments in D274 (from Japanese experts group) were appreciated and were worked into the document.

D-269 which proposes changes to T.42 for soft copy and color reproduction was discussed jointly with Q4 (see Q4 report). T.126 specifies YCbCr and optionally T.42 (CIELAB), while T.42 specifies CIELAB color space only. During editing of T.126, definitions of YCbCr based on video standards, gamma, white point and monitor primaries were described.

D254 (Siemens, Need for harmonization between draft T.126 and T.84) notes that T.126 is scheduled for decision at this meeting of SG8, while T.84 (JPEG extensions) is advancing in ISO/IEC to a DIS ballot and is proposed for determination at this meeting. This was resolved through a joint meeting with Q16/8. It was clarified that T.126 uses T.81(JPEG) as an internal format for image transmission in a multipoint conference and that it does not specify local matters like import/export to other coresident applications. However, because T.84 is a compatible extension, implementers could choose to use only this format for their transmissions.

The base document for T.126 is COM 8-66. The final revisions are presented in TD-2185. T.126 is submitted for decision under Resolution No. 1 at this meeting.

4.2.6 T.127 - Multipoint Binary File Transfer Protocol

The amendments to T.126 included in D248 (Report of the Q10 meeting February 6-10, 1995 in Irvine, CA) were reaffirmed. D213 (Austria, France),proposes using ETS 300 383 (copy included), Eurofile, which is equivalent to T.101 Annex C part 9. It was noted that the editor had researched Eurofile transfer, and it was discussed at meetings in 1994 and this was a stimulus for adding remote directory listing features to T.127. D227 from BT proposes removing support for optional use of V.42bis compression since new patent issues have developed. It was not adopted. No problem is seen as the use of V.42bis is optional; the text will be reworded in places to emphasize this. Since no equally good compression standard exists, Q10 hoped that licensing issues will be resolved quickly. The comments of D275 (Japan) are appreciated and were worked into the document.

The base document for T.127 is COM 8-92. The final revisions are presented in TD-2186. T.127 is submitted for decision under Resolution No. 1 at this meeting.

T.128 - Audio Visual Control for Multipoint Multimedia Systems (T.AVC)

D272 (BT) draft T.AVC is essentially unchanged from the interim meeting. Since T.128 is a high priority, it is proposed to form an ad hoc editor's group to progress the work towards determination at the next meeting of SG 8.

TD-2138 (liaison from SG1 on multipoint session operation and procedures) announces the intention of Q20/1 to replace F.701 teleconference, F.710 audiographic conference and F.730 video conference services with a single Recommendation and harmonize their contents. TD-2147 (liaison from SG 15 reports decisions on continuous presence video). SG15 decided to standardize screen layout and sub-picture numbering but to leave most of the picture composition control to T.AVC. It includes a list of suggested commands. These two liaison were reviewed and are considered consistent with Q10/8's expectation for the content and coverage of T.128. The liaison replies are TD-2176 and TD-2179 respectively.

T.RES - Conference Reservation Protocols

The work proceeds under a new editor in the directions indicated by D287. D287 (France Telecom) - Proposal for T.RES. This notes that a reservation system is especially useful if it can be accessed by a customer currently engaged in a conference for operations such as extending the time or adding new conferees. It judges that the current idea of modeling the reservation-to-MCU interface on X.700 CMISE is not adapted for such transactional communication. It proposes a new study of configurations involving multiple reservation systems and multiple MCUs. It identifies an explicit phase of operation in which the customer binds to the appropriate reservation server. It asks to what extent the resulting interface should be functionally oriented and close to the semantics of reservation.