1、 Page E 1 Recommendation T/Tph 41 (Edinburgh 1988) O RELIABILITY OF ANALOGUE LEASED CIRCUITS Recommendation proposed by the “Telephone Operation and Tariffs” Working Group T/WG 2 (Tph) Text of the Recommendation adopted by the “Telecommtnications” Commission, “The European Conference of Postal and T
2、elecommunications Administrations, considering - the need, for commercial reasons, to provide customers with information on the performance of international - the efforts made by Administrations, for the rational management of their circuits and the need to ensure that - that ILCs are provided and m
3、aintained in accordance with standards, procedures and organizational arrange- leased circuits (ILCs) for private use, customers requirements correspond to the actual technical capacity of the networks, ments as defined in the CCITT M series Recommendations, O recommends that Administrations make th
4、e following information available to customers : 1. The relevant CCITT M Recommendations, which form the basis of international arrangements and standards (see Annex). 2. The average performance of analogue ILCs (Note 1) between CEPT countries (Note 2) has been shown to be consistent and repeatable
5、within the range of observed results obtained during a series of tests over a period of four years (Note 3). 3. Mean values concerning the reliability of intra-CEPT-ILCs, which have been established over three-month observation periods as follows: Mean Downtime per circuit: Mean Time to Restore Serv
6、ice: Mean Time Between Failures : Mean Service Availability per circuit: 12.57 hours 6.06 hours 43.13 days 99.42% 4. This data will be updated when Administrations agree that a significant change of the figures has taken place. 5. The performance of any individual ILC may vary considerably from the
7、mean values stated above. If measured over a longer period than three months, the actual performance figures will tend to the mean value. 6. ILCs with a high degree of utilization tend to show a lower service availability than those of lower utilization, because the closer attention paid by the cust
8、omer to the former leads to a higher level of fault reporting. 7. ILCs used for data transmission tend to show a higher fault report rate than non-data utilizations. 8. As far as the utilization of voice-grade circuits is concerned, only the analogue transmission parameters as specified in CCITT Rec
9、ommendations M. 1020, M. 1025 and M. 1040 are guaranteed by the Administrations. 9. For a particular set of analogue standards, there is a significant variation in the performance of the many types of Modem that may be connected. As a result, no Recommendation on the bit error performance of such ci
10、rcuits can be made. 10. Customer equipment faults are not included in the circuit fault record. An ILC should therefore only be reported faulty after the customer has verified that his equipment and the distant terminal equipment are working correctly. 11. Should the information provided on the basi
11、s of this Recommendation fail to meet users requirements, Administrations will advise of additional means of improving service performance, and of the possible associated charges. O Edition of May 15, 1990 , i- -. . m 2326434 0010257 9 m T/Tph 41 E Page 2 12. The information provided to customers on
12、 the basis of this Recommendation can generally not be used in connection with any claims for refunds. As far as refiinds are concerned only CCITT Recommendation D. 1 or special contract clauses will apply. Note 1. Appropriate figures for digital ILCs will be provided as soon as-from a statistical p
13、oint of view-a sufficient population of such intra-CEPT circuits is in operation and can be observed. Note 2. These data represent the population of ILCs during the years 1982 until 1987 between the following countries: Austria Belgium France Germany (Fed. Rep. of) Italy Netherlands Spain Switzerlan
14、d United Kingdom The number of investigated international leased circuits was reduced by the following formula: s=- loo x N 200+N where S is the number of circuits included in the trial under operational conditions and N is the number of circuits for which the Administration involved had to perform
15、control functions. The actual circuits were selected on a purely random basis by each Administration. The definitions of faults, the observation period and method used to collect information on faults affecting circuits were according to CCITT Recommendation M. 1016, paragraph 3.2. Note 3. The avail
16、ability derived by this method is mean service availability as perceived by the customer. - Edition of May 15, 1990, I- 1 M 2326434 0030258 O = T/Tph 41 E Page 3 Annex INFORMATION ON CERTAIN CCITT M SERES REXOMMENDATIONS The relevant CCITT Recommendations are published in Volume IV-Fascicle IV.2 of
17、the Red Book: - CCITT Recommendations M.140 and M.1015 state that international leased circuits can be used: exclusively for telephony (Pl exclusively for telegraphy (TP) exclusively for data transmission (DP) exclusively for photo-telegraphy or facsimile (FP) (XP) and for services other than those
18、designated above or for combination of services - Analogue voice-grade circuits are provided on the basis of normal transmission characteristics as defined in CCITT - Analogue voice-grade circuits are provided on the basis of enhanced transmission characteristics especially suitable - The line-up pr
19、ocedures and parameters relevant to these circuits are described in CCITT Recommendation M. 1050. - The maintenance procedures are generally those described in CCITT Recommendation M. 1060. - Each KC has a circuit control station and at least one circuit sub-control station with location and respons
20、ibilities - The maintenance procedures defined in the M series Recommendations are designed to ensure compatibility and Recommendations M.1030 or M.1040. for data transmission as dened in CCITT Recommendations M.1020 and M.1025. O as defined in CCITT Recommendations M.1012 and M.1013 respectively. effectiveness of the maintenance organizations of the Administrations/RPOAs concerned with ILCs. Edition of May 15, 1990 :-
