ITU-T M.1235 PDF

General

This Recommendation describes the use of automatic subscriber-to-subscriber test calls as one of the methods for assessing overall network performance [1]. It is intended as a basis for bilateral or multilateral agreements between Administrations interested in this method of investigating network performance.

In correspondence with the objectives of efficient maintenance methods as described in Recommendation M.730 [2] and, in particular, in line with the application of controlled maintenance methods as explained in § 4 of Recommendation M.730 [2], there is a recognized need to continuously assess network performance.

Considering the fact that an international call engages both national and international links, any method for assessing overall network performance should cover the entire chain of national and international links.

Modern switching and transmission systems may have built-in facilities for checking the overall network performance by means of test calls set up automatically from the exchange of origin to the exchange of destination of international calls. Similar facilities may be provided by independent test call generators having access to the switching multiple at the exchange of origin and making test calls to various test call responders in distant countries. Such test call responders may be connected to test numbers in various terminal exchanges in the distant country.

Automatic subscriber-to-subscriber test calls performed either by system-independent test call generators and test call responders, or by built-in facilities performing the same functions, can be applied in bilateral test call programmes involving the networks of two Administrations or regional programmes involving more than two Administrations. It is important that such programmes are well planned and not interfered with by the use of the same test number for other purposes as well.

In order to reflect the real network performance, test call programmes should be carried out both during non-busy and busy periods. The number of test calls to be generated on each selected route will depend on the frequency of difficulties encountered on the route and is independent of the traffic load carried on the route, or the size of the route. In other words, the higher the fault frequency, the fewer test calls will be required to arrive at statistically significant results. Considering that most of a test generator's occupation time is used for sending address information to its own national switching equipment, international links and national links in the distant country are only occupied for a very short time by a test call. The additional load created by test call generators on international traffic routes is therefore normally negligible even on very small routes.

It should be stressed that test call programmes of the type described here always necessitate an agreement between Administrations concerned.