scope:

This American National Standard:

a) Defines speed, accuracy, and dependability performance parameters for cell transfer in the Asynchronous Transfer Mode (ATM) layer of a national public Broadband Integrated Services Digital Network (B-ISDN) through its normative reference to ITU-T Recommendation I.356; ¹

b) Defines a national ATM performance model and provisionally allocates the ITU-T Recommendation I.356 performance values to defined portions of an end-to-end national ATM connection;

c) Provides supplemental information intended to assist performance characterization of national ATM services.

The network performance (NP) parameters and provisional allocations specified in T1.511-2003 apply to national public end-to-end point-to-point ATM connections and to designated portions of such connections when provided in accordance with the normative references (clause 2) and the requirements (clause 3) of this standard. The parameters are defined on the basis of ATM cell transfer reference events that may be observed at physical interfaces between ATM networks and associated customer equipment, and at physical interfaces between ATM networks.²

T1.511-2003 is intended to be used in the planning and offering of national B-ISDN ATM services. The intended users of this standard include ATM service providers, equipment manufacturers, and end users. This standard may be used by service providers in the planning, development, and assessment of ATM services that meet user performance needs, by equipment manufacturers as performance metrics that will affect equipment design, and by end users in evaluating performance.

The scope of T1.511-2003 is summarized in Figure 1. The ATM performance parameters are defined on the basis of ATM cell transfer reference events that may be observed at physical interfaces associated with specified boundaries. For comparability and completeness, ATM performance is considered in the context of the 3 x 3 performance matrix defined in ANSI X3.102, American National Standard for Information systems - Data communication systems and services - User-oriented performance parameters. Three protocol-independent communication functions are identified in the matrix:

1) access;

2) user information transfer; and

3) disengagement. Each function is considered with respect to three general performance concerns (or "performance criteria"):

1) speed;

2) accuracy; and

3) dependability. T1.511-2003 characterizes the speed, accuracy, and dependability of user information transfer provided by national public ATM networks. Planned American National Standards will define cell transfer availability parameters, and provide standard methods of measuring the cell transfer performance parameters in a national context. The national performance of the ATM layer access and disengagement functions, as well as the availability performance of switched B-ISDN services, will be addressed in separate ANSI standards.

T1.511-2003 is structured as follows. Clause 1 specifies the scope of the standard. Clause 2 specifies its normative references. Clause 3 specifies its requirements, many of which are direct references to ITU-T Recommendation I.356. Clause 4 specifies the national ATM performance model. Clause 5 specifies the (provisional) national ATM cell transfer performance allocations. Clause 6 specifies bringing-into-service (BIS) criteria for voice virtual channels. The informative annexes provide supplemental (i.e., nonnormative) information intended to assist application of ITU-T Recommendation I.356 and T1.511-2003.

NOTES

1 Consistent by reference to ITU-T Recommendation I.356, the T1.511-2003 parameters may be augmented or modified based upon further study of the requirements of the services to be supported on B-ISDNs. 2 Consistent by reference to ITU-T Recommendation I.356, the T1.511-2003 parameters are intended to characterize ATM connections in the available state.

3 Consistent by reference to ITU-T Recommendation I.356, the T1.511-2003 parameters apply to cell streams in which all cells conform with the negotiated ITU-T Recommendation I.371 traffic contract.

4 The recommended ATM performance values to be achieved nationally for each of the defined parameters depend on which Quality of Service (QoS) class the end-users and network providers agree upon for the connection. T1.511-2003 (clause 5) uses the four QoS classes defined in ITU-T Recommendation I.356 (§8).

5 Consistent by reference to ITU-T Recommendation I.356, the T1.511-2003 parameters are equally applicable to national virtual channel connections (VCCs) and national virtual path connections (VPCs). The national allocations in clause 5 are also applicable to both VCCs and VPCs. However, the end users (customers) of a national VPC will often be two networks that use the VPC to support individual VCCs. In order to meet the end-toend values on each VCC, the performance of the supporting VPC must be better. The degree to which the VPC performance must be better than VCC performance is for further study.

¹ ITU-T Recommendation I.356: (1) defines parameters for quantifying the ATM cell transfer performance of an international B-ISDN connection (including adjusted parameter definitions that might be used when cells do not conform with the ITU-T Recommendation I.371-negotiated traffic contract); (2) specifies provisional international performance objectives for cell transfer, some of which depend on the user's selection of QoS class; (3) defines QoS classes; and (4) allocates provisional performance objectives to the individual national portions in providing an international B-ISDN ATM connection.

² ITU-T Recommendation I.353 defines performance-significant reference events upon which the ITU-T Recommendation I.356 parameter definitions are based.