AVC-828 ITU - Telecommunication Standardization Sector Q10/8 95-10-305 Study Group 8 Question 10 Rapporteur Group Paris, 2 - 6 October 1995 Audiographic Conferencing SOURCE: Rapporteur Q10/8 TITLE: Liaison statement to Q2/15 STATUS: Not approved by Study Group 8 SUBJECT: Need for H.245 to support addressing and association of media streams carried over separate network connections FOR: Action before 15 January 1996 CONTACT: Bruce DeGrasse BJ Communications 3311 Brookhaven Club Drive Dallas, TX 75234 USA Tel/Fax: +1 214 241 3139 73760.2250@CompuServe.com We are considering audiovisual sessions that include T.120 data conferencing and in which some of the control and media streams may be carried over separate network connections. We believe this is allowed as an option in H.310, and we expect it to be the norm for H.323. Since H.245 is used in both cases and already contains provision to open logical channels within a single multiplexed network connection, we propose that it should support whatever additional addressing and association mechanisms may be needed in these cases. Association means recognizing that several network connections together constitute a single audiovisual session. This is critical if a single node (MCU or terminal) can engage in multiple sessions at the same time. Some of these multiple sessions may originate at the same remote node. We are focusing on ways to associate the T.120 data stream with the control stream. If a mechanism for this exists, it might also be applied to associating the other media streams with the control stream, hence for associating all the streams of a session. We have these specific concerns in trying to understand whether H.245 now meets the perceived needs or how it should be extended: 1. We see no provision for B-ISDN or LAN addressing in H.245. This suggests that the data and control streams will always run parallel, connecting the same pair of nodes. Is this an acceptable restriction, particularly for H.323? 2. We envision associating two network connections by passing a unique identifier over the first connection to the called party of the second connection, then repeating that same unique identifier in the incoming second connection. We are uncertain what fields in H.245 may be used for this purpose (if the control stream is the first connection). 3. We expect in the incoming second connection to pass the unique identifier through an unused or locally managed part of the address selectors. We consider 16 bits to be the appropriate size for this purpose. 4. It is important to state in what context the presumed identifier is unique. If it is generated by the calling party, we must consider the calling address part of matching the second connection to the first. It may be preferrable to generate the unique identifier at the called party instead. 5. At this point, we consider it possible that either a data stream connection or a control stream connection may be established first. This may affect the scenario.