Annex 5 to AVC-743R

Requirements for Q.2931 signalling

Source	:	Q.2/15
Title	:	Terminal Information Exchange During Call Set-up
Purpose	:	Request for comments

CONTACT:	Sakae OKUBO
Rapporteur for Q.2/15
Graphics Communication Laboratories
6F ANNEX TOSHIN BLDG, 4-36-19 Yoyogi,
Shibuya-ku, Tokyo 151 Japan
Phone:	+81 3 5351 0181
Fax:	+81 3 5351 0185
e-mail:	okubo@gctech.co.jp

Experts Group for Video Coding and Systems in ATM and Other Network Environment in Study Group 15 has been studying the methods by which terminal related information can be exchanged between the calling and called end points.

Two methods are being considered that can be used in a complementary fashion.  These are out-of-band signaling (e.g., Q.2931) and in-band signaling (e.g., H.24X).

1.  Requests on VC signaling operation

The following scenarios are envisaged:

1-  A single VC established between the calling and the called terminal

In this scenario the network delay in renegotiating the QoS of the VC becomes important.  Advice is sought on estimates of such delay for renegotiation.

2-  Multiple VCs established between the calling and the called terminal

In this scenario the following are required:

a)	Additional connections should be routed in a way that minimizes VC differential delay,
b)	Since the initial call set up delay in B-ISDN (e.g., in the  order of 10 seconds) is not acceptable for subsequent VCs  there is a need to establish additional connections in less time. 

We wish to be informed on any activity in SG11 related to item a) above and receive  advice on order of magnitude estimates for item b).

In addition Q2/15 wishes to be informed on activities within SG11 that relate to specifications on end-to-end negotiation and renegotiation and the time frames for the availability of these specifications.

2.  Requests on Asymmetric VC Capabilities

SG11’s input is requested regarding the feasibility of the following:

a)	Specification of asymmetric traffic descriptors and AAL1 parameters on Q.2931 both user-to-network and user-to-user.

b) 	Specification of asymmetric AAL i.e., AAL1 on one direction and AAL5 on the reverse direction	

3.  Request of Code Points

For both of the above scenarios 1 and 2, a decision should be made as to how terminal information can be exchanged i.e., either out-of-band or in-band.

The choice depends on the following factors:

a)	The type of information exchanged e.g., terminal compatibility, capability etc.
b)	The impact of this information on the connection efficiency
 
As a guideline Q 2/15 is following the principle that the information be carried out-of-band only if absolutely necessary.

Table 1 lists the information types, information in each type and the potential field in Q.2931. It is assumed that the terminal information is sent by the calling terminal to the called terminal to which the called terminal responds correspondingly .  Based on the response the calling terminal decides whether to continue operation or disconnect the VC and specify the reason for disconnection. 

Table 1:  Requested terminal information on Q.2931

Information Type
	Information	Information Element	
Terminal Protocol	H.32X A1 & B1
H.32X A2 & B2
H.32Y
H.320	B-LLI byte 6	
Forward Multiplexing Capability	No multiplex
TS 
TS with FEC
PS
PS with FEC
H.221	B-LLI byte 6A	
Backward Multiplexing Capability	No multiplex
TS 
TS with FEC
PS
PS with FEC
H.221		
Session ID	Session_ID	B-LLI byte 6B	

Under the terminal protocol, H.32X A1 & B1 refer to mainly receive B-ISDN terminal protocols; H.32X A2 & B2 refer to both transmit and receive B-ISDN terminal protocols, H.32Y refers to an H.320 equivalent B-ISDN terminal protocol and H.320 refers to a N-ISDN H.320 terminal protocol.  In the last case it is noted that the H.320 terminal is not equipped to respond with Q.2931 and an equivalent action can be taken on H.32Y (by a terminal adapter on behalf of the H.320 terminal).  If  the H.32Y feature is not be implemented on the adapter then no response would follow and the default of H.320 should be assumed by the H.32X A2 & B2 calling terminals.  In order to study further the case of N-B ISDN interworking, SG15 seeks advice from SG11 on the status of signaling  for N-B ISDN interworking e.g., Progress Indication.

Under multiplexing capability on table 1, indicated are initial conditions on the established VC.  A number of options are present depending on the terminal protocol, see table 2:

H.32X A1 & B1	H.222.1 is used and the choice to be indicated is between  Transport stream (TS) or Program Stream (PS) mode and whether Forward Error Correction (FEC) is used.
H.32X A2 & B2	The choice is between either not using multiplexing or using H.222.1.  In the latter case a choice should be made between using a TS or a PS.
H.32Y	This case offers no choice and does not need to be explicitly indicated, however an explicit indication is preferred.
H.320	This case represent no choice and does not need to be explicitly indicated, however an explicit indication is preferred.

Session_ID is a generic parameter that indicates the correspondence of the VC to a certain previously established request carried outside Q.2931.  This case arises only when the terminal protocol indications are H.32X A1 & B1.

Table 2:  Relevance of information to terminal protocols

	H.32X A1 & B1	H.32X A2 & B2	H.32Y 	H.320 	
No multiplex		√			
TS	√				
TS with FEC	√	√			
PS	√				
PS with FEC	√	√			
H.221			√	√	
Session_ID	√				

Q2/15 wishes to relate to SG11 the need for the above information types with the express request for code point assignments and the earliest time for such accommodation.  For this purpose suggestions for fields are provide under the column for Information Element in table 1.

End