ITU-T X.131 PDF

Introduction

Quality of service in circuit-switched public data networks has been considered in five basic areas as follows:

i) call processing delays (Recommendation X.130);

ii) failures due to congestion (blocking) (Recommendation X.131);

iii) failures due to malfunction;

iv) loss of service; and

v) transmission performance (including throughput).

This Recommendation specifies the objectives for ii) above. Each of the other areas of circuit-switching quality of service identified above will be the subject of a separate Recommendation in the X-series.

In telecommunication networks it is necessary, for economic reasons, to limit the resources provided for carrying the offered traffic. This limitation may affect the quality of service to the user of circuit-switched services in two different ways: by call processing delays and by blocking. Both of these aspects, that are consequences of the finite traffic handling capacity of the network, constitute the grade of service. Grade of service together with malfunction, loss of service and transmission performance constitute the quality of service.

In this Recommendation the values for the network blocking are quoted for two types of connection according to Recommendation X.92 as follows:

Type 1: Typical terrestrial interconnection of moderate length with no satellite circuits either in the national or international portions. (International portion: 1000 km.)

Type 2: Long distance international connection with a satellite circuit in one national portion and two satellite circuits in the international portion. (International portion: 160 000 km.)

Where appropriate, values are also specified separately for the following network portions:

- originating national network,

- international portion,

- destination national network.