1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 % TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%0(/.%G0G0.%47/2+G0G0!.$G0G0)3$.15!,)49G0G0/ otherwise very seriouscongestion can result from repeated attempts.5 General notesNote 1 Teletraffic implications for international switching and operational pr
2、ocedures under failure of atransmission facility are discussed in Supplement No. 5 of this fascicle.Note 2 Alternative routing in the national and in the international networks provides on average a grade ofservice that is better than that provided in the theoretical final route.Note 3 Non-coinciden
3、ce of traffic peaks in the national and international networks will provide reduction inthe overall grade of service compared with the sum of the design grade of service values per link.Note 4 Time differences will also improve the resulting grade of service.Note 5 The methods of measuring and calcu
4、lating the traffic base for provisioning purposes in the nationalnetworks may be different in various countries and differ from the methods for the international network given inRecommendation E.500. This means that the national traffic values are not always comparable among themselves orwith the va
5、lues of the international network. Each Administration must estimate how its design traffic level compareswith that recommended for the international network.Note 6 The design grade of service value of each link will only apply if the traffic at each switching stage isequal to the forecast. In pract
6、ice, such a situation will seldom occur. Furthermore, the planning procedure normally issuch that the specified grade of service should not be exceeded until the end of the planning period. In a growingnetwork, this means that the circuit groups during almost the whole planning period give a better
7、service than thespecified critical standard.In conclusion, the overall grade of service depends on the accuracy of forecasts made and the planningprocedure used, i.e. it depends on the interval between plant additions and on the specific traffic value in future towhich the grade of service is related.Reference1 CCITT Recommendation International routing plan, Rec. E.171.
