ITU - Telecommunication Standardization Sector	Temporary Document 1/11-
STUDY GROUP 11	Original: English
	
Geneva, 1st - 19th September, 1997

Document addressed to: WP 1
Question(s):  20/11 (DSS2)

QUESTION:	20/11(1)    (DSS 2)

SOURCE*: 	Editor

TITLE:      	Proposed Changes to Q.2931

______________________________________

ABSTRACT

This document contains proposed changes to the text sections of Recommendation Q.2931.  This document reflects changes agreed upon at the Interim rapporteurs meeting in Oak Broak (Illinois),  June 1997.

______________________________________

Following enhancements were agreed to be introduced  to the living list:

-	technical flaw with regard to the handling of RELEASE and RELEASE COMPLETE message with invalid non-mandatory information elements has been resolved.
-	handling of a message containing a global call reference after two RESTART messages have collided has been clarified.
-	actions to be taken upon receipt of a message with the global or dummy call reference containing IEs in error, for which the instruction indicator is set to “clear call” have been clarified. However, further clarification is required on how call state associated to the global call reference value is returned to Null state.
-	Coding of the B-LLI has been enhanced in order to allow for indication of Terminal capability (i.e. AAL type(s)) supported as needed for H.310 Terminal protocol identification.

The convention for the proposed text changes is:
New text is underlined.
Deleted text has strike through.
Existing text is as shown.

1.  Introduction

This document contains proposed changes to the text sections of Recommendation Q.2931.  This document reflects changes agreed upon at the June meeting in Oak Brook (Illinois/USA).  Section 2 contains the entire list of changes.

2.  List of Changes

Clause 3.2.7/Q.2931 (SETUP message)
Ed: Add the following sentence to Note 1 to support AAL type negotiation:
One or two AAL parameters information elements may be included, in decreasing order of priority.

Clause 4.5.5/Q.2931 (AAL IE)

Ed: Add following codepoint and text to Table 4-6 (Sheet 3 of 3), Partially Filled Cell Method:
0000 0000    partially filled cells method is not used, i.e., cells are filled completely (Note)
Note: The indication of this codepoint is equivalent to the absence of the subfield for partially filled cells method.

Ed: Modify note at the end of Table 4-6 relating to default value for partially filled cells by replacing current text "default = 47 octets" by:
default = partially filled cells method is not used, i.e., cells are filled completely.

Clause 4.5.5/Q.2931 (AAL IE)

Add two new codepoints to the SSCS Type subfield (octet 8.1 for AAL type 5):
8 7 6 5 4 3 2 1	Bits
0 0 0 0 1 0 0 0   	ITU-T Rec. I.365.2 (SSCF to provide CONS and Q.2110 (SSCOP)) (Note 1)
0 0 0 0 1 0 0 1 	ITU-T Rec. I.365.3 (SSCF to provide COTS and Q.2110 (SSCOP))  (Note 1)

Note 1: This codepoint is only applicable for AAL type 5.

In addition, clarify the meaning for the following  existing codepoints for the SSCS Type subfield:

8 7 6 5 4 3 2 1	Bits
0 0 0 0 0 0 0 1	ITU-T Rec. Q.2110 (SSCOP assured operation) with unspecified SSCF
0 0 0 0 0 0 1 0	ITU-T Rec. Q.2110 (SSCOP non-assured operation) with unspecified SSCF
0 0 0 0 0 1 0 0 	ITU-T Rec. I.365.1 (SSCS to provide frame relay services)

Clause 4.5.6/Q.2931 (ATM Traffic Descriptor)

Ed: In Figure 4-13/Q.2931, octet groups 5 and 6 should be denoted as “5*, 5.1*, 5.2*, 5.3*, 
6*, 6.1*, 6.2*, 6.3*” instead of “5, 5.1, 5.2, 5.3, 6, 6.1, 6.2, 6.3”.

Clause 4.5.7/Q.2931	(B-BC; add to end of intro. text)

This information element carries information relating to the use of the connection associated with this call/connection.

(Ed: the following sentence needs further input from Mr. Dianda)
This information element represents information that does not change from connection to connection, except to reflect changes in the in-band protocol stack used from connection to connection.

Clause 4.5.8/Q.2931 (B-HLI; add to end of intro. text)

This information element carries information relating to the use of the connection associated with this call/connection.

This information element represents information that does not change from connection to connection, except to reflect changes in the in-band protocol stack used from connection to connection.

Clause 4.5.9/Q.2931 (B-LLI)

Add the following two codepoints to the User information layer 3 protocol field (bits 5-1 Octet 7):    
5 4 3 2 1    Bits
0 1 1 0 0    ITU-T Recommendation H.310
0 1 1 0 1    ITU-T Recommendation H.321

Add the following octets to B-LLI contents: 

Additional B-LLI Contents		
8	7	6	5	4	3	2	1		
0/1	Terminal capability	Terminal Type	7a*	
Ext			(Note 6)	
1	0	Forward Multiplexing	Backward Multiplexing	7b*	
ext	Spare	Capability	Capability	(Note 6)	

Note 6: This octet may be present only if octet 7 indicates ITU-T Rec. H.310.

Terminal Type (bits 4-1 Octet 7a)
4 3 2 1	Bits
0 0 0 1  	Receive only
0 0 1 0  	Send only
0 0 1 1  	Receive and send

Terminal capability (bits 7-5 Octet 7a)
7 6 5	Bits
0 0 0	no indication
0 0 1	Terminal is capable of supporting only AAL 1
0 1 0	Terminal is capable of supporting only AAL 5
0 1 1	Terminal is capable of supporting both AAL1 and AAL 5

Forward Multiplexing Capability (bits 6-4 Octet 7b)
6 5 4	Bits
0 0 0   	No multiplexing
0 0 1   	Transport stream (TS)
0 1 0   	Transport stream with forward error correction
0 1 1   	Program stream (PS)
1 0 0   	Program stream with forward error correction
1 0 1   	ITU-T Rec. H.221

Backward Multiplexing Capability (bits 3-1 Octet 7b)
3 2 1	Bits
0 0 0   	No multiplexing
0 0 1   	Transport stream (TS)
0 1 0   	Transport stream with forward error correction
0 1 1   	Program stream (PS)
1 0 0   	Program stream with forward error correction
1 0 1   	ITU-T Rec. H.221

Note 1 - The allowable combination of codepoints for the Multiplexing capability and Terminal type fields  may be restricted.  These restrictions are provided within the terminal protocol specifications.

Clause 4.5.9/Q.2931 (B-LLI)

This information element carries information relating to the use of the connection associated with this call/connection.

This information element represents information that does not change from connection to connection, except to reflect changes in the in-band protocol stack used from connection to connection.

Octet groups 5 (layer 1 id.), 6 (layer 2 id.), and 7 (layer 3 id.) of the Broadband low layer information element are not position independent, but, if present at all, shall be sent in the order as specified in Figure 4-16/Q.2931.

Clause 4.5.18/Q.2931 (Figure 4-18)

Replace “Unspecified QOS class” by “No specific QoS class explictly requested”.
Modify Note 1 to read “When used, the network shall provide and quarantee a quality of service compatible and consistent with the requirements indicated in the Broadband bearer capability information element.”

Clause 4.6/Q.2931 (Figures 4-31, 4-32, 4-33, and 4-34)

Further contents as in Figure 4-xx/Q.931 and Table 4-xx/Q.931. (Note)

Note: The coding rules of Q.931 shall apply.

Clause 4.6.2/Q.2931 (Narrowband bearer capability, add to end of intro. text)

This information element carries information relating to the use of the connection associated with this call/connection.

This information element represents information that does not change from connection to connection, except to reflect changes in the in-band protocol stack used from connection to connection.

Clause 4.6.4 (Narrowband low layer compatibility, add to end of intro. text)

This information element carries information relating to the use of the connection associated with this call/connection.

This information element represents information that does not change from connection to connection, except to reflect changes in the in-band protocol stack used from connection to connection.

Clause 5.1.3/Q.2931

Ed: replace "ATM user cell rate" with "ATM traffic descriptor".

Clause 5.2.3/Q.2931 (change last two paragraphs)

The network and user shall support the non-associated signalling procedures and may as an option support the associated signalling procedures.  A subscription option is necessary if the network supports both non-associated and associated signalling. The associated signalling procedures are used only by bilateral agreement between the user and the network.

When the user network receives a Connection identifier information element...with a value not supported by the user network, the call shall be rejected with cause #36, "VPCI/VCI assignment failure".

Clause 5.6.3.2 e)/Q.2931
Add the following note after 5.6.3.2 e)
Note - The current state to be indicated is the one associated to the restart state machine relating to the global call reference value (including the flag) of the unexpected message received.

Clause 5.6.8.1/Q.2931

Action shall be taken on the message and those information elements which are recognized and have valid content.  Unrecognized information elements shall be discarded and ignored.

Clause 5.6.8.2/Q.2931

action shall be taken on the message and those information elements which are recognized and have valid content. Information elements with content error shall be discarded and ignored.

Clause 5.6.8.2/Q.2931

Amend the first paragraph of section 5.6.8.2/Q.2931 as follows:
When a message other than RELEASE or RELEASE COMPLETE is received which has one or more information elements with invalid content Ö” 
Add the following text as new (second) paragraph afterwards:
If a clearing message is received with one or more invalid non-mandatory information elements, it shall be handled as follows:
-	if it is a RELEASE message, a RELEASE COMPLETE message with cause #100, “invalid information element contents’ shall be returned. The cause information element diagnostic field, if included, shall contain the information element  identifier for each invalid information element received.
-	If it is a RELEASE COMPLETE message, no action shall be taken on the invalid information elements.

Clause 5.7.2/Q.2931
Add following text at the beginning of section 5.7.2 (information element errors with explicit action indication):
These procedures only apply to call reference values other than the dummy call reference value.

Clause 5.7.2/Q.2931
Add following text as a new paragraph at the end of section 5.7.2 (information element errors with explicit action indication):
If a message with the global call reference is received which contains one or more unrecognised or invalid information elements with the instruction indicator set to ‘clear call’, no RELEASE message shall be returned (since the clearing procedures are not applicable to the global call reference value).

Clause 6.3 Interworking N-ISDN -> B-ISDN (add new subclause as follows)

6.3.6  Mapping of Clearing Messages

The DISCONNECT message of Q.931 is mapped to the RELEASE message of Q.2931.

Clause 6.4 Interworking B-ISDN -> N-ISDN (add new subclause as follows)

6.4.5 Mapping of Clearing Messages

The RELEASE message of Q.2931 is mapped to the DISCONNECT message of Q.931.

Clause 6.4.5/Q.2931

93 78 AAL parameters cannot be supported ) ==> value 79 Service or option not
                                                                               implemented, unspecified;
                                                                               95 Invalid message, unspecified

Clause 6.6.2/Q.2931

Ed: Delete reference to timer T312 from the list of timers in this clause because T312 only applies to DSS 1, not DSS 2.

Annex B/Q.2931 (second last paragraph)

Therefore,...that the terminal checks the B-LLI,...

Annex C/Q.2931 (Note in Section C.3)

Ed: Add to the note negotiation of octet 7a as follows:

... layer 2 mode (octet 6a), window size (octet 6b), User Specified Layer 2 information (octet 6a), layer 3 mode (octet 7a), default packet size (octet 7b), and packet window size (octet 7c). 

Annex E/Q.2931 (Tables E-1, E-2, E-3)

AAL parameters:  AAL for voice see ß E.4

Annex F.2/Q.2931

d) for User defined AAL:
   - User defined AAL Information (4 octets).

Annex F.3/Q.2931

c) is missing either the forward or backward maximum CPCS-SDU size;

the calling endpoint should shall clear the call with cause No. 100, “invalid information element contents.”

Annex F.4/Q.2931

the calling endpoint should shall clear the call with cause No. 100, “invalid information element contents.”

Annex F/Q.2931

Add the following new section F.6 to support AAL type negotiation.
The following procedures were agreed to when using BCOB-X.  Usage of these procedures for other Bearer classes are for further study.  Concern was expressed regarding complexity when using with voice.

F.6	AAL type selection and negotiation procedures

The AAL type selection and negotiation procedure is optional, but may be a mandatory requirement for the provision of certain services or applications.

If the calling user wishes to indicate an alternative AAL type, the AAL parameters information element is repeated in the SETUP message.  Up to two AAL parameters information elements may be included in a SETUP message, in descending order of priority so that the order of appearance of the AAL parameters information elements indicates the order of preference of the AAL type.

The called user indicates a single choice of AAL type among the choices offered in the SETUP message by including the AAL parameters information element in the CONNECT message.  The absence of  an AAL parameters information element in the CONNECT message implictly indicates the acceptance of the type of AAL as identified in the first AAL parameters ifnormation element that was included in the SETUP message.  The called user may also negotiate parameter values of the selected AAL type by using the procedures in subclauses F2 to F5.

If the network or called user does not support repeated AAL parameters information elements, and therefore discards the second AAL parameters information element (following the first that shall always be recognized and accepted), only the first AAL parameters information element is used in the negotiation.

If the calling user rejects the AAL parameters information element contents in the CONNECT message, the calling user shall initiate clearing with cause #100, “invalid information element contents”.

_______________________________________________________________

This is a new optional capability to Q.2931.  It is to be included as an Annex.

Attachment     End-to-end Connection Completion Indication

A1 	Introduction

This Attachment describes how indication of end-to-end connection completion can be provided to the called user. End-to-end connection indication is an end-to-end (user-to-user) feature and does not require any participation from the network beyond forwarding the messages and information element from one user to the other. 

A2	Coding Requirements

A2.1	Messages

End-to-end connection completion indication requires the use of the SETUP, CONNECT, and CONNECTION AVAILABLE messages. The SETUP, CONNECT, and CONNECTION AVAILABLE messages need to include the Broadband report type information element to support end-to-end connection completion indication.

A2.2	Information Elements

A2.2.1	Broadband report type

See section Figure 1/Q.2963 for the coding of the Broadband report type information element.

The following report types are used in the connection completion indication operation:

- End-to-end connection completion capability available
 This value is used by the calling user to indicate to the called user that an indication of end-to-end connection completion can be provided for completion of the call. It is included in the SETUP message.

- End-to-end connection completion indication requested
This value is used by the called user to indicate to the calling user that an indication of end-to-end connection completion is desired for completion of the call. It is included in the CONNECT message.

- End-to-end connection completed
This value is used by the calling user to indicate to the called user that the end-to-end connection is completed and that information transfer can begin. It is included in a CONNECTION AVAILABLE message.

The  type of report (octet 5) shall be coded as the following:

Bits	Meaning	
  8 7 6 5    4 3 2 1		
  x x x x    x x x x
  x x x x    x x x x
  x x x x    x x x x	End-to-end connection completion capability available
End-to-end connection completion indication requested
End-to-end connection completed	

A3	Call/connection Control Procedures for Connection Completion Indication

A3.1	Activation/deactivation/registration

Not applicable.

A3.2	Invocation and Operation

A3.2.1	Normal operation

The procedures for end-to-end connection completion indication are based on the Connection modification procedures of Q.2963, although support for Q.2963 itself is not required. The network, when it supports connection completion indication, shall forward the indications to the other user involved in the call. 

A3.2.2	Actions at the Destination Interface

A called user wishing to request an end-to-end connection completion indication during call establishment includes the Broadband report type information element in the CONNECT message, with the type of report coded as "End-to-end connection completion indication requested", and starts timer T333.  T333 is a new timer defined for this procedure.  The called user may do this whether or not the incoming SETUP message contained an End-to-end connection completion capability indication (see A3.2.3).

(Ed: is the word shall appropriate?)
The called user shall wait for the receipt of a CONNECTION AVAILABLE message, with the indication description coded as  “End-to-end connection completed" before sending information. Upon receipt of this indication, the called user shall stop timer T333.

A3.2.3   Actions at the Originating Interface

If the calling user is able to support connection completion indication if requested by the called user, it may optionally indicate this by including a Broadband report type information element in the SETUP message with the type of report coded to “End-to-end connection completion capability available”.

If, as part of call establishment, a calling user receives a Broadband report type  information element in the CONNECT message, with the type of report coded as "End-to-end connection completion  indication requested", it should interpret it as a request to send an indication that the end-to-end connection is completed. At  that time, the calling user shall send a CONNECTION AVAILABLE message, and include a Broadband report type information element with the type of report coded as "End-to-end connection completed", and the call reference of the existing call. 

A3.2.4		Exceptional Procedures

A3.2.4.1		Actions at the Destination Interface

The actions to be taken when timer T333 expires are implementation-dependent, e.g., the call could resume and information transfer could begin, or the call could be cleared according to normal procedures.

If the called user receives a CONNECTION AVAILABLE message with the indication description coded as "End-to-end connection completed", but the called user had not previously send a Broadband report type  information element in the CONNECT message, with the indication description coded as "End-to-end connection completion indication requested", the CONNECTION AVAILABLE message shall be ignored.

A3.2.4.2 	Actions at the Originating Interface

There is no exceptional procedure identified at the originating interface.

A4		Parameter Values

The following user-side timer has been identified in the procedures for invocation and operation:

Table A1-1  Timer  in the user side defined in Annex A1.
Timer Number	Default Time-
out Value	State
of
Call	Cause
for
Start	Normal
Stop	At The
Expiry	Implementation	
T333	10s	Connection Request	Sending of “End-to-end connection completion indication requested” in CONNECT message.	Receipt of “End-to-end connection completed” in CONNECTION AVAILABLE message.	Implementation Dependent (see section A3.2.4.1)	Mandatory	

Note:  The time for the CONNECTION AVAILABLE message to be received at the destination interface may be quite lengthy, and in some cases it may be better to use a local timer started on receipt of the CONNECT ACK message.