1、CCITT FASCICLE VI-5 * W 48b2591 0508183 2 Recommendation 4.542 DIGITAL EXCHANGE DESIGN OBJECTIVES - OPERATIONS AND MAINTENANCE 1 General This Recommendation applies to digital local, combined, transit and international exchanges for telephony in Integrated Digital Networks (IDN) and mixed (analogue/
2、digital) networks, and also to local, combined, transit and international exchanges in an Integrated Services Digital Network (ISDN). The field of application of this Recommendation is more fully defined in Recommendation Q.500. Some objectives only apply to a certain type (or types) of exchange. Wh
3、ere this occurs, the application is defined in the text. Where no such qualification is made, the objective applies to all exchange applications. 2 Maintenance design objectives The exchange shall be arranged so that normal maintenance activities can be easily performed by maintenance personnel. It
4、should be capable of providing all information necessary for the identification of trouble conditions and the direction of repair activities. 2.1 Status and other information The exchange shall provide information to maintenance personnel so that they can quickly ascertain: - equipment/system status
5、, - critical load levels, - trouble conditions, - network management controls in effect. 2.2 Inputs and outputs The exchange shall be able to transmit and receive maintenance information and respond to commands from on-site and if appropriate, from remote maintenance centre(s) or systems over the re
6、commended interface(s) (Recommendation Q.513). In performing operations and maintenance functions, the exchange shall use CCITT MML at its input/output terminals as covered in the Z.300-series of Recommendations. 2.3 Routine testing The exchange shall have facilities for performing or directing rout
7、ine test activities on its component parts and possibly with interfacing equipment or systems. 2.4 Trouble localization The exchange shall have adequate facilities for diagnosing and locating faults within the exchange. 2.5 Fault and alarm detection and actions at interfaces A, B, VI, V, and V, The
8、exchange shall interact with transmission systems as required to detect fault and alarms and take appropriate actions. 2.5.1 Fault detection The following fault conditions should be detected: - failure of local power supply (if practicable); - loss of incoming signal; Note - The detection of this fa
9、ult condition is required only when the fault does not result in an indication of loss of frame alignment. I -. Fascicle VI.5 - Rec. 4.542 47 c 7 CCITT FASCICLE VI.5 f* m 4862573 0508L84 4 m - loss of frame alignment (see Recommendations G.706; the loss of frame alignment will also be assumed if no
10、CRC multiframe alignment can be achieved or if the proportion of corrupted CRC checks exceeds a certain value); excessive error ratio (without CRC procedure). The criteria for activating and deactivating the indication of the fault condition are given in draft Recommendation G.707. Consequent action
11、s are given in 8 2.5.3; CRC error reporting, if applicable: a) every time a received CRC block is detected errored by the exchange termination: - a report will be transmitted to the error monitoring function; - the information “one multiframe errored” is transmitted in the outgoing signal at the eve
12、ry time that an E bit in the binary state O is received, a report will be transmitted to the error monitoring functions. (On a provisional basis the considerations related to the E bit may only apply to V interfaces - for further study.) interface using an E bit (see Recommendation G.704, 8 2.3.3.4)
13、; b) 2.5.2 Alarm signal detection The following alarm indications should be detected: - - Alarm indication (remote alarm) received from the remote end. AIS (alarm indication signal). The equivalent binary content of the alarm indication signal (AIS) is a continuous stream of “1”s at 2048 or 8448 kbi
14、t/s. The strategy for detecting the presence of the AIS should be such that the AIS is detectable even in the presence of an error ratio of 1 in lo3. However, a signal with all bits except the frame alignment bit in the 1 state should not be mistaken as an AIS. 2.5.3 Consequent actions 2.5.3.1 Gener
15、ation of alarm signals for action within the exchange - The service alarm indication should be generated to signify that the service is no longer available (see Table UQ.542). The prompt maintenance alarm indication should be generated to signify that performance is below acceptable standards and th
16、at immediate maintenance attention is required locally (see Table 1/Q.542). - 2.5.3.2 Generation of alarm signals transmitted by the exchange - Alarm signals sent in the outgoing direction at the exchange interface. The relevant alarm bits for the remote alarm indication, as recommended in G.704 sho
17、uld be effected as soon as possible (see Table VQ.542). Alarm signals sent towards the switching function. Alarm indication signal applied in all received time-slots containing speech, data and/or signalling should be applied as soon as possible and not later than 2 ms after the detection of the fau
18、lt condition (see Table 1/Q.542). - 2.5.3.3 Removal of alarm indications When all fault conditions have been cleared and alarm indication signal is no longer received, the alarm indication signal and remote alarm indication should be removed within the same respective time limits as specified in 0 2
19、.5.3.4 after the conditions have cleared. 48 Fascicle VI.5 - Rec. Q.542 CCITT FASCICLE VI-5 * m 4862573 0508385 b m TABLE 1/Q.542 Fault conditions and alarms detected by exchange termination functions and consequent actions (excluding inferface Vi) Fault conditions and alarm signals detected Failure
20、 of power supply Loss of incoming signal Loss of frame alignment Excessive error ratio Alarm indication received from remote end AIS received Service alarm indication generated Yes YeS YCS Yes 2048 + 8448 kbit/s: Yes 1544 + 6312 kbit/s: optional YeS Consequent actions (see 8 2.5.3) Prompt maintenanc
21、e alarm indication generated Yes Yes Yes Yes 1544 + 6312 kbit/s: Yes Alarm indication to remote end generated Yes, if practicable Yes YCS Yes YeS AIS towards the switching stages Yes, if practicable YeS Yes Yes Yes Note - A Yes in the table signifies that an action should be taken. An open space in
22、the table signifies that the relevant action should not be taken if this condition is the only one present. If more than one fault condition or alarm is simultaneously present, action should be taken if for at least one of the conditions a Yes is shown, except in the case of AIS received for which 8
23、 2.5.3.4 applies. The use of error performance monitoring in this table is for further study. 2.5.3.4 Alarm processing The following items are required to ensure that equipment is not removed from service due to short breaks in transmission (e.g. due to noise or transient fault) and to ensure that m
24、aintenance action does not result where no direct maintenance action is required. The persistence of service alarm and of the prompt maintenance alarm indications may be verified for 100 ms before action is taken. When the AIS is detected, the prompt maintenance alarm indication, associated with los
25、s of frame alignment and excessive error rate in the frame alignment pattern, should be inhibited. When the fault conditions cease, the service alarm and prompt maintenance alarm indications, if given, should be removed. Again, the persistence of this change in condition may be verified for 100 ms b
26、efore action is taken. - - - 7 49 Fascicle V.5 - Rec. Q.542 - 7 7 CCITT FASCICLE VI-5 * 48b259L 0500LBb - degraded transmission interface; - unacceptable transmission interface. Note 1 - This section may only apply to V interfaces (for study). Note 2 - The level at which an interface for ISDN access
27、 enters the degraded transmission condition Note 3 - The levels at which an interface enters the degraded or unacceptable transmission conditions (see 1.600-series of Recommendations): may be dependent on the quality of service provided to the customer. are for further study and are outside the scop
28、e of this Recommendation. 2.5.4.4 Consequent actions For further study. 2.6 Fault and alarm signal detection and actions at intedace V, The exchange shall interact with transmission systems as required to detect fault and alarm signals and take appropriate actions. a) Fault detection b.) Alarm detec
29、tion c) Consequent actions 50 Fascicle VIS - Rec. 4.542 To be specified CCITT FASCICLE VI.5 * 4862.591 0508387 T 2.1 Fault and alarm signal detection and actions at interface Z To be specified l a) Fault detection b) Alarm detection c) Consequent actions 2.8 Fault and alarm signal detection and acti
30、ons for transmission systems Faults and alarms which cannot be directly detected by the exchange termination function but which are detected by transmission equipment (e.g., group pilot failure) should be accepted by the exchange as needed to take appropriate action. 2.9 Fault and alarm signal detec
31、tion and actions for channel associated signalling (2048 and 8448 kbit/s) 2.9.1 Fault detecfion The exchange signalling function should detect the following fault conditions for each multiplex carrying a - - 64-kbit/s signalling channel: failure of local power supply (if practicable), loss of 64 kbi
32、t/s incoming signal, Note - The detection of this fault condition is required only when the fault does not result in an indication of loss of multiframe alignment. - loss of multiframe alignment. The criteria for activating and deactivating the indication of the fault condition are given in Recommen
33、da- tions G.132 and G.744. 2.9.2 Alarm detection The exchange signalling function should detect the alarm indication (remote alarm) received from the remote end. 2.9.3 Consequent actions 2.9.3.1 Generation of alarm signals for action within the exchange - The Service Alarm indication should be gener
34、ated by the exchange signalling function to signify that the service is no longer available (see Table 2/Q.542). - The prompt maintenance alarm indication should be generated to signify that performance is a below acceptable standards and that immediate maintenance attention is required locally (see
35、 Table 2/Q.542). 2.9.3.2 Alarm transmitted by the exchange An alarm indication (remote alarm) should be applied in the outgoing direction at the transmission/ switching interface as soon as possible (see Table 2/Q.542). The relevant alarm bit for the remote alarm indication is given in Recommendatio
36、n G.132. 2.9.3.3 Removal of alarm indication When all fault conditions have been cleared and AIS is no longer received, the remote alarm indication should be removed as soon as possible. 2.9.3.4 Alarm processing Same as in 8 2.5.3.4. ,- , .r-l Fascicle VI.5 - Rec. Q.542 51 - -_-_ L -. CCITT FASCICLE
37、 VI.5 * 4862593 0508388 L TABLE 2/Q.542 Fault conditions and alarms detected by the exchange signalling function and consequent actions Service alarm indication generated Fault conditions and alarms detected) Yes Loss of 64 kbit/s incoming signal Yes Loss of multiframe alignment Alarm indication rec
38、eived from remote end Yes Consequent actions (see 8 2.9.3) Prompt Alarm indication to maintenance alarm remote end indication generated generated Yes Yes, if practicable YeS YeS I CCITT FASCICLE VI-5 * = Y8b2593 0508389 3 W 2.12.3 Internal timing distribution The distribution of timing information t
39、o the major elements of the exchange shall be supervised as required. A service alarm shall be given when a failure is detected. A maintenance alarm shall be given if it is appropriate. Note - Remote elements may have to be taken into consideration. 2.13 Supervision or testing of interface function
40、The exchange shall have the capability of verifying the proper operation of the interface functions, including the fault detection and supervision functions. Routine tests, statistical tests, manual activities and/or other means may be used to verify proper operation of these functions. Information
41、shall be given to the far end exchange when new calls cannot be established on the circuits on which routine tests are being initiated. Established calls, including semi-permanent connections, must not be interrupted. During the tests, the generation of alarms at the far end exchange due to the remo
42、val of circuits from service should be avoided, if possible. 2.13.1 ETfunctions - Interfaces A, B, 6. V3 and V4 The verification of the proper operation of exchange termination functions can be performed by the means of statistical observations or by testing. Testing may be manual or automatic. 2.13
43、.2 ET functions - Interfaces C and Z i) ii) Failures of codecs (except those covered in ii) below) should be recognized by the exchange using the criteria defined in Recommendation G.732. Supervision or testing of codecs of one or a small number of channels may be accomplished according to i) above
44、or by inter-office transmission measurement and testing on circuits between exchanges or by statistical measurements. 2.13.3 ETfunctions - Interface VI To be specified. 2.14 Supervision or testing of signalling functions In addition to fault detection required in 0 2.7, the following applies. 2.14.1
45、 Channel associated signalling The exchange should be able to verify the proper operation of the signalling functions by generating and responding to test calls or by a statistical observation. 2.14.2 Common channel signalling The exchange should be able to verify the proper operation of the signall
46、ing functions as required by common channel signalling recommendations. 2.15 Supervision or testing of exchange connections Checking the different portions of the path individually in a digital exchange network helps to ensure the continuity of the connections overall. In this respect the exchange h
47、as to verify: - - the continuity across the exchange, as covered in this section; the continuity in the transmission links terminating on the exchange as covered in $0 2.16 and 2.17. F Fascicle VI.5 - Rec. 4.542 53 - P 7 7 - - CCITT FASCICLE VI-5 Xt m 48b2593 0508390 T m 2.15.1 Continuity across the
48、 exchange A means should be provided to determine that the operational error performance requirement e, on bit error ratio) is being met. (The design objective for error performance can be found in Recommendation 4.554.) The exchange should provide adequate provision of the cross office path continu
49、ity and verify the transmission performance. (The design objective for transmission performance can be found in Recommenda- tion 4,543.) This will guarantee, in particular, an acceptable transmission quality to its connections. 2.15.2 Verijcation depending on the type of connection The verifications to be performed by the exchange should depend also on the type of connection. In particular: - for 64 kbit/s switched connections, the transmission performance requirements of 4.543 may be considered to be sufficient in order to guarantee the cross office path continuit
