(Continuation of Questions 4 and 5/13 studied during 1997-2000)

Background and justification

The work on the basic definition of the ATM layer has been mostly completed and is in a stable condition. However, there remains the issue of how to support multicast services (point-to-multipoint, multipoint-to-point, and multipoint-to-multipoint) that needs to be addressed, particularly for satellite and other shared media technologies. Relevant issues at the ATM layer that may have impacts on existing Recommendations have to be addressed, in particular, the possible need for additional pre-assigned ATM cell header values.

Much of the work on ATM Adaptation Layer (AAL) specifications has been completed in past study periods. Specifications have been prepared for AAL Types 1, 2, 3/4 and 5 together with a number of service specific convergence sublayers. However a number of issues remain to be studied which may result in new Recommendations or enhancements to existing Recommendations.

Items for study

In particular the following points should be studied:

• ATM layer capabilities to support multicast services and other point-to-multipoint, multipoint-to-point, multipoint-to-multipoint services.
• Potential additional pre-assigned ATM cell header values

Tasks with deadlines

Enhancements of I.150, as appropriate

Enhancements of I.361, as appropriate

Establish specifications in new or existing Recommendations for AAL types as required. Possible areas of study include:

1. Clarification of the usage of AAL type 2 in an ATM based access network and specification of AAL type 2 SSCS if required (deadline: end 2001).
2. Clarification of ATM layer transfer capabilities and performance/QoS suitable for particular AAL protocols (deadline: end 2001).
3. Study of the management functions required by a specific AAL, in close relationship with overall management studies of Question 3/13.
4. Study of the possible AAL functions suitable for support of real-time VBR services.

Relationships

• ITU-T Study Groups on service aspects;
• ITU-T Study Groups on signalling and switching capabilities;
• ITU-T Study Groups on transport systems and equipment;
• ITU-R on wireless and satellite aspects;
• Other bodies outside the ITU such as the ATM Forum and the IETF.