scope:

This Recommendation defines parameters that may be used in specifying and assessing the performance of speed, accuracy, dependability and availability of IP packet transfer of international Internet Protocol (IP) data communication services. The defined parameters apply to the end-to-end, point-to-point IP service and to the network portions that provide, or contribute to the provision of, such service in accordance with the normative references specified in clause 2. Connectionless transport is a distinguishing aspect of the IP service that is considered in this Recommendation.

For the purpose of this Recommendation, end-to-end IP service refers to the transfer of user-generated IP datagrams (referred to in this Recommendation as IP packets) between two end hosts as specified by their complete IP addresses. This differs from the boundaries implied by the phrase "end-to-end" in some other Recommendations. For example, [ITU-T P.10] defines end-to-end quality as related to the performance of a communication system, including all terminal equipment. For voice services, end-to-end is equivalent to mouth-to-ear quality.

NOTE 1 - This Recommendation defines parameters that can be used to characterize IP service provided using IPv4 and IPv6; applicability or extension of this Recommendation to other protocols (e.g., RSVP) is for further study.

NOTE 2 - Recommendations for the performance of point-to-multipoint IP service are currently under development.

The Recommendation ITU-T Y.1540 performance parameters are intended to be used in planning and offering international IP service. The intended users of this Recommendation include IP service providers, equipment manufacturers and end users. This Recommendation may be used by service providers in the planning, development and assessment of IP service that meets user performance needs; by equipment manufacturers as performance information that will affect equipment design; and by end users in evaluating IP service performance.

The scope of this Recommendation is summarized in Figure 1. The IP service performance parameters are defined on the basis of IP packet transfer reference events that may be observed at measurement points (MPs) associated with specified functional and jurisdictional boundaries. For comparability and completeness, IP service performance is considered in the context of the 3 × 3 performance matrix defined in Recommendation [ITU-T I.350]. Three protocol-independent communication functions are identified in the matrix: access, user information transfer and disengagement. Each function is considered with respect to three general performance concerns (or "performance criteria"): speed, accuracy and dependability. An associated two-state model provides a basis for describing IP service availability.

The performance parameters defined in this Recommendation describe the speed, accuracy, dependability and availability of IP packet transfer as provided by the IP data communication service. Future ITU-T Recommendations may be developed to provide standard methods of measuring the ITU-T Y.1540 performance parameters in an international context. The end-to-end performance of international IP services providing access and disengagement functions (e.g., domain name service) and higher-layer transport capabilities (e.g., transmission control protocol) may be addressed in separate Recommendations.

This Recommendation is structured as follows: Clause 1 specifies its scope. Clause 2 specifies its normative references. Clause 3 provides a list of abbreviations. Clause 4 illustrates the layered model that creates the context for IP performance specification. Clause 5 defines the model used for IP performance, including network sections and measurement points, reference events and outcomes. Clause 6 uses this model to define IP packet transfer performance parameters. Clause 7 then defines IP service availability parameters. Appendix I describes IP packet routing considerations and their effects on performance. Appendix II provides secondary terminology for IP packet delay variation. Appendix III describes some possible metrics for IP packet rate and reference material for assessing the throughput and throughput capacity of IP service. Appendix IV describes estimation of IP service availability. Appendix V presents considerations for measuring the ITU-T Y.1540 parameters. Appendix VI gives some background on IP service availability. Appendix VII offers background information on the stream repair parameters, and Appendix VIII adds information on capacity parameters (including a mapping to prior IETF metrics and items for further study).

NOTE 4 - The ITU-T Y.1540 parameters may be augmented or modified based upon further study of the requirements of the IP applications (e.g., interactive, block, stream) to be supported.

NOTE 5 - The ITU-T Y.1540 speed, accuracy and dependability parameters are intended to characterize IP service in the available state.

NOTE 6 - The parameters defined in this Recommendation can apply to a single end-to-end IP service between two end hosts identified by their IP addresses. The parameters can also be applied to those IP packets from a given end-to-end IP service that are offered to a given network or exchange link.

NOTE 7 - The ITU-T Y.1540 parameters are designed to characterize the performance of service provided by network elements between specified section boundaries. However, users of this Recommendation should be aware that network elements outside the specified boundaries can sometimes influence the measured performance of the elements between the boundaries. Examples are described in Appendix V.

NOTE 8 - The parameters defined in this Recommendation can also be applied to any subset of the IP packets offered to a given set of network equipment. Methods for aggregating performance over a set of network equipment or over an entire network are outside of the scope of this Recommendation.

NOTE 9 - This Recommendation does not provide the tools for explicit characterization of routing stability. However, the effects of route instability can be quantified using the loss, delay and severe loss block parameters defined in this Recommendation.

NOTE 10 - Specification of numerical performance objectives for some of the ITU-T Y.1540 performance parameters may be found in [ITU-T Y.1541].

NOTE 11 - The word "provisional", as used in this Recommendation, means that there is agreement on the stability of the value referenced, but that the value may change following further study, or on the basis of real network operational experience.