ÿWPCL ûÿ2BJ|xÐ ` ÐÐÌÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿH øÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÌÐÐ °°°è ÐÑ Âx„|ü@Ž ÑÐ Å°6Ø'°6Ø'Å ÐÓÓÃÃRecommendation I.604ÄÄ Ð ø ÐÁàð#ÁAPPLICATION OF MAINTENANCE PRINCIPLES TO ISDN PRIMARY RATE ACCESSESƒ 1.ÁHÁÃÃScope of applicationÄÄ Ð 8 ÐÁHÁThis Recommendation covers the maintenance of that part of the ISDN subscriber primary rate access, controlled by the network, follows the maintenance principles as defined in Recommendation M.20 and applies to the primary rate access connected to the local exchange. ÃÃNotes related to Figure 1/I.604ÄÄ Ð X ÐÃÃNote 1ÄÄ © The subscriber access contains a digital link which can use different varieties of transmission techniques and media. Figure 2/I.604 shows examples of configurations made by using existing digital line systems and multiplexers complying with G.700 and G.900©Series of Recommendations. ÃÃNote 2ÄÄ © A local exchange should be able to connect different types of digital line systems and different types of subscriber installations at V3 interfaces complying with Recommendation Q.512. ÃÃNote 3ÄÄ © The use of different types of digital line systems shall not affect the subscriber installation complying with Recommendation I.431. ÃÃNote 4ÄÄ © The subscriber access shall comply with the CRC procedure defined in Recommendations G.704 and G.706. ÃÃNote 5ÄÄ © In some countries the subscriber installation is allowed to control certain maintenance functions in the subscriber access. ÃÃNoteÄÄ © The digital sections may include one or more regenerators. ÁàÀIÁFIGURE 2/I.604ƒ ÁàÀPÁƒ ÁàÀ8ÁÃÃExamples of equipment configurations in the ISDNÄă ÁàÀAÁÃÃsubscriber primary rate accessÄă 3.ÁHÁÃÃFailure detectionÄÄ 3.1ÁHÁÃÃGeneralÄÄ ÁHÁUnlike the ISDN basic access, the digital section of the ISDN subscriber primary rate access is never deactivated (as seen by the exchange), continuous automatic supervision of the correct functioning of layer 1 up to NT2 is always operating. This supervision is called Continuous Automatic Supervision of layer 1. ÁHÁAutomatic supervision of the correct functioning of the D©Channel layers 2 and 3 is also operating. This supervision is called automatic supervision of layers 2 and 3 of the D©Channel protocol. 3.2ÁHÁÃÃAutomatic supervisionÄÄ 3.2.1ÁHÁÃÃObjectivesÄÄ ÁHÁThis supervision is realized by continuous automatic mechanisms located in various pieces of equipment of the ISDN primary rate access. ÁHÁThese automatic mechanisms are never deactivated and generally based on the operation of CRC information which is given by the CRC procedure associated with the link between the customer and the local exchange. These mechanisms are complemented by the detection of malfunctioning of particular items e.g. loss of power supply, loss of incoming signal, loss of frame alignment. Minimum functions which could be allocated to the subscriber installation and exchange termination are listed below. Further detail for these functions and those of the digital section are found in Annex A where various options concerning the handling of CRC functions are described. 3.2.2ÁHÁÃÃNT2 termination functionsÄÄ ÁHÁThe functions allocated to the NT2 are listed below: ÁHÁ©Á  Ádetection of loss of incoming signal; ÁHÁ©Á  Ádetection of loss of frame alignment; ÁHÁ©Á  Ádetection of AIS and RAI; ÁHÁ©Á  Ágeneration of frame signal; ÁHÁ©Á  ÁCRC code generation; ÁHÁ©Á  ÁRAI generation; ÁHÁ©Á  ÁCRC monitoring of the incoming signal (network©to©user); ÁHÁ©Á  Ádetection of CRC error information (user©to©network); ÁHÁ©Á  ÁCRC error reporting to the network (optional in 1544 kbit/s). 3.2.3ÁHÁÃÃExchange termination functionsÄÄ ÁHÁThe functions which are allocated to the ET are listed below: ÁHÁ©Âà  Âdetection of loss of incoming signal;ÆÆ ÁHÁ©Á  Ádetection of loss of frame alignment; Ô ñ,ÔŒÁHÁ©Á  Ádetection of AIS: generation of AIS (optional in 1544 kbit/s); ÁHÁ©Á  Ádetection of RAI; ÁHÁ©Á  Ágeneration of frame signal; ÁHÁ©Á  ÁCRC code generation; ÁHÁ©Á  ÁRAI generation; ÁHÁ©Âà  ÂCRC monitoring of the incoming signal (user©to©network);ÆÆ ÁHÁ©Âà  Âdetection of the CRC error information (network©to©user);ÆÆ ÁHÁ©Âà  ÂCRC error reporting to the user (optional in 1544 kbit/s).ÆÆ ÁHÁThe exchange termination may optionally detect the CRC error information reported by the user side. ÁHÁThe generation of RAI towards NT2 upon detection by ET of a fault in the input direction (loss of signal, loss of frame alignment, detection of AIS). ÁHÁThe exchange termination has the option to evaluate the transmission performance based on the statistical treatment of the local and remote CRC error reports and on the fault indications. ÁHÁThe transmission performance evaluation is based on a permanent processing of the elementary results presented by the continuous error monitoring of the digital transmission link. ÁHÁThe result of this processing will give information on the transmission quality level (normal quality, degraded quality, unacceptable quality) and on the unavailability of the access (see ÀÀ 5.6). 3.3ÁHÁÃÃAutomatic supervision of layers 2 and 3 of the D©Channel protocolÄÄ ÁHÁThis covers supervision of activities of layers 2 and 3 of the          D©Channel protocol. Automatic supervision of layers 2 and 3 will be made by self©acting mechanisms implemented in the network (e.g. in the ET). ÁHÁThere are three categories of automatic supervision which may be performed by layer 2 and layer 3 of the D©Channel protocols; ÁHÁ©Âà  Âservice provision incapability detection (e.g. incapability of layer 2 to establish a data link connection);ÆÆ ÁHÁ©Âà  Âprotocol misoperation detection;ÆÆ ÁHÁ©Âà  Âerror monitoring (e.g. the layer 2 CRC check procedure can detect the occurrence of an errored frame).ÆÆ ÁHÁThese events (defined in Recommendations I.440 and I.450) should be recorded. 4.ÁHÁÃÃSystem protectionÄÄ ÁHÁWhen a confirmed fault is detected which has an adverse effect on the availability and/or functionality of network equipment, the access is considered "out of service due to failure" and call attempts may be rejected to prevent further damage or to remove the adverse effect (see draft Recommendation I.601). 5.ÁHÁÃÃFailure indicationÄÄ 5.1ÁHÁÃÃDefault indication signalsÄÄ ÁHÁa)Á   ÁAIS © as defined in Recommendation I.431. ÁHÁb)Á   ÁRAI © as defined in Recommendation I.431. 5.2ÁHÁÃÃState tablesÄÄ ÁHÁState tables associated with failures in the primary rate access are given in Recommendation I.431. 5.3ÁHÁÃÃGeneration of defect indication signals by the NT2ÄÄ ÁHÁThe NT2 functions are listed in ÀÀ 3.2.2. ÁHÁThe generation of RAI toward the ET is used to indicate the loss of incoming layer 1 capability. 5.4ÁHÁÃÃGeneration of defect indication signals by the subscriber accessÄÄ ÁHÁThe digital link functions are listed in the annex to this Recommendation for each option within the access. 5.5ÁHÁÃÃGeneration of defect indication signals by the exchange terminationÄÄ ÁHÁThe exchange termination functions are listed in section 3.2.3. ÁHÁThe generation of RAI toward the NT1 is used to indicate the loss of incoming layer 1 capability. 5.6ÂàHÂÃÃTransmission quality monitoring by the exchangeÄÄÆÆ 5.6.1ÁHÁÃÃError performance parametersÄÄ ÁHÁAccording to Recommendations M.20 and M.550, the anomaly and defect indications are treated on a statistical basis. 5.6.2ÁHÁÃÃError performance evaluationsÄÄ ÁHÁThe access is considered by the local exchange to be "unavailable", "unacceptable" or "degraded" according to Recommendation M.550. 5.7ÁHÁÃÃFailure information from the exchangeÄÄ ÁHÁA defect confirmed by the exchange and related to a subscriber access and/or a subscriber installation shall be reported to the SAMC in a message. ÁHÁThe detection of a degraded or unacceptable quality level or of the unavailability of the access by the exchange shall be reported to the SAMC in a message. ÁHÁThe message could be presented after an automatic identification of a failed Maintenance Entity (ME) has been made (see ÀÀ 6). 5.8ÁHÁÃÃFailure information to the subscriber installationÄÄ ÁHÁThe detection of a degraded or unacceptable quality level by the exchange may be reported to the user by the transmission of a state indication.Ô ñ,ÔŒ 6.ÁHÁÃÃFailure localizationÄÄ 6.1ÂàHÂÃÃAutomatic confirmation of failure within the subscriber primary rateÄÄ ÃÃaccessÄÄÆÆ ÁHÁAn automatic test procedure to confirm a detected possible failure condition within the subscriber access should be provided. It shall be initiated by an automatic reaction of the exchange, following abnormal conditions which have been detected by the processes presented above, i.e. continuous supervision of layer 1, supervision of layers 2 and 3 of the D©Channel protocol. ÁHÁIf failures are detected in the D©Channel layers 2 and 3 communication, clear differentiation between failures within the subscriber installation and within the subscriber access should be possible. 6.2ÁHÁÃÃIdentification of failed maintenance entitiesÄÄ 6.2.1ÁHÁÃÃGeneralÄÄ ÁHÁSuch a function has to be made on demand or automatically following the indication of failure conditions by the network or following a subscriber complaint. It is necessary, before undertaking the appropriate action, to identify (i.e. to know) the maintenance entity affected by the failure. 6.2.2ÁHÁÃÃObjectivesÄÄ ÁHÁThe main objective of this function, which is controlled by the SAMC, is to indicate to the SAMC whether the failure is: ÁHÁ©Á  Áwithin the ET; ÁHÁ©Á  Áwithin the digital transmission link (NT1 to LT); ÁHÁ©Á  Áwithin the subscriber installation. 6.3ÁHÁÃÃLoopbacks for maintenance of the subscriber primary rate accessÄÄ 6.3.1ÁHÁÃÃLocation of loopbacksÄÄ ÁHÁPossible loopback locations for failure localization and verification controlled by the SAMC are shown in Figure 3/I.604. ÁàÀIÁFIGURE 3/I.604ƒ ÁàÀPÁƒ ÁàÀ2ÁÃÃLocation of the loopbacks for the maintenance of the generalÄă ÁàÀ2ÁÃÃequipment configuration of the subscriber primary rate accessÄă Ð ð ÐÃÃNote 1ÄÄ © The digital section may contain one or more regenerators shown as "REG" in this figure. 6.3.2ÁHÁÃÃCharacteristics of loopbacksÄÄ ÁHÁThe characteristics of the loopbacks are given in Table 1/I.604. Áà8MÁTABLE 1/I.604ƒ Áà8SÁƒ Áà82ÁÃÃCharacteristics of the loopbacks for primary rate subscriber accessÄă ÃÃNote 1ÄÄ © These layer 1 signals may not be in the frame signals. They may be line signals. ÃÃNote 2ÄÄ © In the case of using existing digital systems, a manual loopback may replace loopback 2. This loopback is implemented between NT2 and NT1 and is controlled by the user on demand of the network staff. 6.4ÁHÁÃÃFailure localization mechanismsÄÄ ÁHÁIf a subscriber access failure is confirmed by the exchange and if the failure is not located in the exchange, then: ÁHÁ©Âà  Âeither the loopback 2 can be established under control of the exchange,Ô ñ,Ô then:ÆÆ ÁHÁÁ  Á©Âà øÂif the loopback 2 is successful, the exchange considers the subscriber access to be functioning correctly;ÆÆ ÁHÁÁ  Á©Âà øÂif the loopback 2 is unsuccessful, the exchange reports to the OAMC;ÆÆ ÁHÁ©Âà  Âor, if the loopback 2 cannot be established under control of the exchange, then the exchange informs the OAMC that the digital link is affected by a failure.ÆÆ ÁHÁIn the case of failed maintenance entity being detected, then an automatic localization process is initiated. This process could localize the failure within the digital link by the use of loopbacks or subscriber access fault information. ÃÃNoteÄÄ © SAME functions may be distributed in different equipment. Áà8LÁFIGURE 4/I.604ƒ Áà8SÁƒ Áà85ÁÃÃExample of network architecture for the failure localizationÄă Áà8@ÁÃÃwithin the subscriber primary rate linkÄă 6.4.1ÁHÁÃÃInitial failure localization performed by the ET and/or NT2 (TE)ÄÄ ÁHÁThe initial failure localization capability depends on the CRC option used in the network. For further information about different CRC options which may be applied in the access see Annex A to this Recommendation. ÁHÁIn general, CRC error information and fault indication signals may be used by either the NT2 or ET to deduce the location of some failures in operational conditions. ÁHÁFailure localization in the case of option 2 refers to the capability to distinguish between a failure occurring either: ÁHÁ©Á  Ábetween NT2 and NT1; or ÁHÁ©Á  Ábetween NT1 and ET. ÁHÁFailure localization in the case of option 3 refers to the capability to distinguish between a failure occurring either: ÁHÁ©Á  Ábetween NT2 and NT1; or ÁHÁ©Á  Ábetween NT1 and LT; or ÁHÁ©Á  Ábetween LT and ET. ÁHÁFailure localization in the case of option 4 refers to the capability to distinguish between a failure occurring either: ÁHÁ©Á  Ábetween NT2 and NT1; or ÁHÁ©Á  Ábetween NT1 and ET. ÁHÁThis localization may be achieved by either the NT2 or the ET obtaining additional information from the NT1. The means to obtain this information is for further study. 6.4.1.1Á  ÁFailure localization performed by the NT2 ÁHÁIn options 2 and 3 the combination of CRC error information and RAI received from the interface allows the NT2 to localize a fault in the upstream direction of the access as follows: ÁHÁ©Âà  Âreceipt of RAI by the NT2 with no, or a very small number of reported CRC errors indicates a failure inside the network; orÆÆ ÁHÁ©Âà  Âreceipt of RAI by the NT2 with constantly, or a very high number of, reported CRC errors indicates a fault between NT2 and NT1.ÆÆ ÁHÁThis capability is not provided by option 1. ÁHÁConcerning the downstream direction of the access, failure localization can be made in options 1, 2 and 3, by distinguishing between the following conditions at the receiving side of the NT2: ÁHÁ©Âà  ÂAIS, indicating a fault inside the network; orÆÆ ÁHÁ©Âà  Âloss of incoming signal or loss of frame alignment, indicating a failure between NT1 and NT2.ÆÆ 6.4.1.2Á  ÁFailure localization performed by the ET ÁHÁThe failure localization capability of the ET depends on the CRC option used in the access, on the fault detection and reporting capability of the equipment installed (see ÀÀÀÀ 6.4, 6.4.2 and 6.5) and the provision of optional loopbacks as given in Table 1/I.604. For further information about different CRC options applied in the access see Annex A to this Recommendation. 6.4.2ÁHÁÃÃFurther failure localizationÄÄ ÁHÁFor more precise localization, further techniques may be necessary, e.g. line parameter measurements. ÁHÁThis is for further study. Ô ñ,ÔŒ6.4.3ÁHÁÃÃAdditional signalsÄÄ ÁHÁThe use and definition of additional signals for transmission direction indication, extension of remote CRC reporting mechanisms and specific equipment signals is for further study. 7.ÁHÁÃÃLogistic delay timeÄÄ ÁHÁSee Recommendation M.20. 8.ÁHÁÃÃFailure connectionÄÄ ÁHÁSee Recommendation M.20. 9.ÁHÁÃÃVerificationÄÄ ÁHÁThe verification that the failure has been corrected is performed on demand of the staff. ÁHÁTests described in ÀÀÀÀ 3, 6 and 11 may be used. 10.ÁHÁÃÃRestorationÄÄ Ãà                                                                ÄÄ Áà8PÁANNEX Aƒ Áà8SÁƒ Áà8GÁ(to Recommendation I.604)ƒ Áà8GÁÃÃSubscriber access optionÄÄ ƒ A.1ÁHÁÃÃDigital link without CRC processing (option 1)ÄÄ A.1.1ÁHÁÃÃDefinitionÄÄ ÁHÁThe transmission equipment used between interfaces at the T and V reference points (multiplexers, NT1©LT) could be existing equipment which have standard functions of supervision and defect and fault detections. ÁHÁIn this case, the digital link is said to be "without CRC processing": the CRC procedure is between ET and NT2 (see Figure A.1/I.604). ÁHÁLegend: L = Local CRC error information ÁHÁÁ  Á  R = Remote CRC error information ÁHÁÁ  Á  M = CRC monitor ÁHÁÁ  Á  G = CRC generator ÁHÁÁ  Á  ÀÀÀÀÀÀÀÀÀÀ = Mandatory ÁHÁÁ  Á  ÃÃ.....ÄÄ = Optional ÃÃNoteÄÄ © CRC error reporting may require storage functions in the NT2 and ET. Áà8KÁFIGURE A.1/I.604ƒ Áà8SÁƒ Áà8BÁÃÃDigital link without CRC processingÄă A.1.2ÁHÁÃÃDigital link functionsÄÄ ÁHÁFunctions allocated to the digital link are listed below: ÁHÁ©Âà  Âdetection of loss of incoming signal on either side and inside the transmission section, and generation of AIS "downstream";ÆÆ ÁHÁ©Âà  Âdetection of AIS inside the transmission section and generation of AIS "downstream".ÆÆ ÁHÁ©Âà  Âdetection of defect and anomaly in the digital link.ÆÆ A.1.3ÁHÁÃÃNT2 functionsÄÄ ÁHÁFunctions allocated to the NT2 are given in ÀÀ 3.2.2 of Recommendation I.604. A.2ÁHÁÃÃDigital link with CRC processing in the NT1 (Option 2)ÄÄ A.2.1ÁHÁÃÃDefinitionÄÄ ÁHÁThe transmission equipment used between interfaces at the T and V referenceÔ ñ,Ô points could be new equipment with CRC processing in the NT1 (see Figure A.2/I.604). In this case, the digital link is said to be with "CRC processing in the NT1". ÁHÁLegend: L = Local CRC error information ÁHÁÁ  Á  R = Remote CRC error information ÁHÁÁ  Á  M = CRC monitor ÁHÁÁ  Á  G = CRC generator ÁHÁÁ  Á  ÀÀÀÀÀÀÀÀÀÀ = Mandatory ÁHÁÁ  Á  ÃÃ.....ÄÄ = Optional ÃÃNote 1ÄÄ © Optional in 1544 kbit/s systems. ÃÃNote 2ÄÄ © CRC error reporting may require storage functions in the NT2, NT1 and ET. Áà8KÁFIGURE A.2/I.604ƒ Áà8SÁƒ Áà8>ÁÃÃDigital link without CRC processing in NT1Äă A.2.2ÁHÁÃÃDigital link functionsÄÄ Ãà                                                           ÄÄ A.2.3ÁHÁÃÃNT2 functionsÄÄ ÁHÁFunctions allocated to the NT2 are given in ÀÀ 3.2.2 of Recommendation I.604. A.3ÁHÁÃÃDigital link with CRC processing in the LT and NT1 (Option 3)ÄÄ A.3.1ÁHÁÃÃDefinitionÄÄ ÁHÁThe transmission equipment used between interfaces at the T and V reference points may be new equipment with CRC processing, treatment and reporting of the results of that processing in the NT1 and the LT (see Figure A.3/I.604). In this case the digital link is said to be with "CRC processing and reporting in the NT1 and the LT". ÃÃNoteÄÄ © CRC error reporting may require storage and processing function in NT2, NT1, LT and ET. ÁHÁLegend: L = Local CRC error information ÁHÁÁ  Á  R = Remote CRC error information ÁHÁÁ  Á  M = CRC monitor ÁHÁÁ  Á  G = CRC generator ÁHÁÁ  Á  T = CRC error treatment and reporting ÁHÁÁ  Á  ÀÀÀÀÀÀÀÀÀÀ = Mandatory ÁHÁÁ  Á  ÃÃ.....ÄÄ = Optional Áà8KÁFIGURE A.3/I.604ƒ Áà8SÁƒ Áà83ÁÃÃDigital link with CRC processing and reporting in the LT and NT1Äă A.3.2ÁHÁÃÃLT functionsÄÄ ÁHÁFunctions allocated to the LT are listed below: Ô ñ,ÔŒÁHÁÃà                                                    ÄÄ A.3.3ÁHÁÃÃNT1 functionsÄÄ ÁHÁFunctions allocated to the NT1 are listed below: A.4ÁHÁÃÃDigital link with CRC monitoring in the NT1 (Option 4)ÄÄ A.4.1ÁHÁÃÃDefinitionÄÄ ÁHÁThe transmission equipment used between interfaces at the T and V reference points could be new equipment with CRC monitoring in the NT1 (see Figure A.4/I.604). In this case, the digital link is said to be "with CRC monitoring in the NT1". ÁHÁLegend: L = Local CRC error information ÁHÁÁ  Á  R = Remote CRC error information ÁHÁÁ  Á  M = CRC monitor ÁHÁÁ  Á  G = CRC generator ÁHÁÁ  Á  SN = Storage for network side monitor ÁHÁÁ  Á  SU = Storage for user side monitor ÁHÁÁ  Á  ÀÀÀÀÀÀÀÀÀÀ = Mandatory ÁHÁÁ  Á  ÃÃ.....ÄÄ = Optional Áà8KÁFIGURE A.4/I.604ƒ Áà8SÁƒ Áà8@ÁÃÃDigital link with CRC monitoring in NT1Äă A.4.2ÁHÁÃÃNT1 functionsÄÄ ÁHÁFunctions allocated to the NT1 are listed below: ÁHÁ©Âà  Âdetection of loss of signal or loss of frame alignment at either side;ÆÆ ÁHÁ©Âà  Âgeneration of AIS toward either side when signal or frame alignment on opposite side is lost;ÆÆ ÁHÁ©Âà  Âmonitor CRC from both directions;ÆÆ ÁHÁ©Âà  Âstore information derived from the CRC monitoring.ÆÆ ÁHÁThe information derived from the CRC monitoring and stored in the NT1 may be retrieved from either the NT2 or ET. The means of this retrieval is for further study. A.4.3ÁHÁÃÃNT2 functionÄÄ ÁHÁIn addition to the functions described in ÀÀ 3.2.2, NT2s may also, optionally, have the capability of retrieving from the NT1 the stored information derived from CRC monitoring. A.4.4ÁHÁÃÃET functionÄÄ ÁHÁIn addition to the functions described in ÀÀ 3.2.3, ETs may also, optionally, have the capability of retrieving from the NT1 the stored information derived from CRC monitoring. Ô ñ,ÔŒ