џWPCL ћџ2BJ|xа АH аа АА X агга ХА6p&А6p&Х аеЮ† а Hр аааУ Уб cмˆ4 PŽТ б Fascicle II.3 Р-Р Rec. E.428 Ф ФPAGE1У Уб cмˆ4 PŽТ б ЮееЃ† а HH аааб cмˆ4 PŽТ бPAGE2У Уб cмˆ4 PŽТ б Fascicle II.3 Р-Р Rec. E.428 Ѓеа HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаа X  аУ Уб cмˆ4 PŽТ бRecommendation E.428 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр8HСб cмˆ4 PŽТ бCONNECTION RETENTION аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б1ТX ТIntroductionФ ФЦЦ а H аС СConnection retention is one of the parameters influencing the quality of service (QOS) after the call has been set up. As the assessment of this parameter is difficult and costly, it is recommended to investigate only after information from sources such as operator trouble reports, subscriber complaints, interviews and/or service observations indicate that there is a problem. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У2С  Сб cмˆ4 PŽТ бCutР-Рoff call ratioФ ФЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бС СThe cutР-Рoff call ratio is the percentage of the established calls that are released for a reason other than intentional by any of the parties involved in the call. The cutР-Рoff call ratio can only be measured by placing test calls (see Recommendation G.181). ‚У У3ТX ТInvestigations requiredФ ФЦЦ а H аС СBefore measuring the cutР-Рoff call ratio the source information leading to the investigation should be utilized to the extent possible (see Annex B to Recommendation E.420) and the outcome should be compared with other relevant sources. For example, subscriber complaints can be followed up by investigating operator trouble reports. С СThese investigations should lead to a suspect part of the network. ‚У У4ТX ТExchange of informationФ ФЦЦ а H аС СIn case the suspect part of the network is outside the territory of an Administration, the Administration which has responsibility for the suspect part of the network should be contacted and informed of the results of the investigations. In the information given, the type of cutР-Рoffs should be classified by causes such as Р"Рabsence of answer signalР"Р, Р"Рartificial clearback signalР"Р, etc. ‚У У5ТX ТFurther investigation requiredФ ФЦЦ а H аС СWithin the suspect part of the network, the Administration should look for obvious causes of cutР-Рoffs such as exchange or facility failures. If obvious causes cannot be identified the Administration should consider test calls. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У6С  Сб cмˆ4 PŽТ бTest callsЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ ФС СOne or both Administrations may decide to set up a test call programme. а H аС СInternational standardized test call types are contained in Recommendation E.424. As stated in that Recommendation, before applying type 3 test calls or subscriberР-РtoР-Рsubscriber type test calls, it should be verified that there are no evident faults in the national network. This verification can easily be undertaken by applying nonР-Рstandardized test calls, for example from the international centre to a subscriber number in the national network of the same country (see Recommendation E.424, 4) of РSР 1). а H аС СThe usefulness of standardization in these kinds of test calls is under study in several Administrations. а H аС СFor making test calls on connection retention, the responding equipment used should send an answer signal after 10 seconds followed by a continuous tone in conformity with Recommendation O.61. The threshold level of the detector in the directing equipment should also be in conformity with Recommendation O.61. ‚У У7ТX ТObjectivesФ ФЦЦ С СThe longР-Рterm objectives as well as the allocations are given in Recommendation G.181. In the intermediate time the following requirements should apply: the cutР-Рoff call ratio for subscriberР-РtoР-Рsubscriber tests should, measured over 24Р-Рhour periods, be below 0.5% for 5 minute calls. In any timeР-Рconsistent hour the call cutР-Рoff rate may not exceed 3%. а H аС СIt should be noted that, in general, cutР-Рoff problems have a more severe impact on customers' perception of service on routes with a low answer seizure ratio than on routes with a low completion rate.