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1991-12-30
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Recommendation E.426
GENERAL GUIDE TO THE PERCENTAGE OF EFFECTIVE ATTEMPTS WHICH
SHOULD BE OBSERVED FOR INTERNATIONAL TELEPHONE CALLS
1 General considerations
1.1 The success of call attempts is fundamental to an automatic international
telephone service of high quality.
1.2 The periodic observation of completion ratio1) and the categorization of
failures to destination countries together with the exchange of such information
between countries are valuable to establish and/or maintain a high service
quality.
1.3 call completion ratio of the national
network of a given country, as manifested through its international
switching centre(s), affects the efficiency of operation of all
countries routing traffic to that country.
1.4 Call completion ratio information can be provided either
internally in an SPC international switching
centre or externally at the level of the outgoing international
circuits in any international switching centre in which access to
the circuits is provided for the purpose of establishing the
disposition of call attempts.
1.5 The availability, flexibility and capacity of minicomputers
provides an economically attractive method of obtaining call
completion ratio information with extreme accuracy. This includes
the observation of tones when suitable interfaces with the
minicomputer are provided.
2 A guide to the proportion of effective call attempts
2.1 A general guide for the expected percentage of effective call attempts
during the mean busy hour and its two immediately adjacent hours, as observed at
the originating international switching exchange, is indicated below. An
effective call attempt is defined, for this purpose, as one for which an answer
is received at the originating international exchange. Faults caused by the
originating international exchange shall be excluded to the extent feasible. All
attempts which succeed in seizing an international circuit shall be included in
the results:
a) low level of effective call attempts: less than 30%;
b) medium level of effective call attempts: 30% to 60%;
c) high level of effective call attempts: more than 60%.
2.2 When an originating country notes a downward change in the level of
effective call attempts towards any destination, the originating, destination or
transit Administrations should initiate investigations to determine and alleviate
the underlying causes (e.g. network provisioning, subscriber behaviour). The
objective of this action is to avoid degradation in the level of effective call
attempts.
1) See Recommendation E.600.
Fascicle II.3 - Rec. E.426 PAGE1