Recommendation I.605 APPLICATION OF MAINTENANCE PRINCIPLES TO STATIC MULTIPLEXED ISDN BASIC ACCESSES 1. Scope of application This Recommendation covers the maintenance of the static multiplexed basic rate access, con- trolled by the network, and describes the operations and maintenance aspects of the V4 interface. The V4 interface is defined in RecommendationQ.512. The specification of the operations and maintenance aspects of the V4interface is the subject of this Recommendation. This Recommendation follows the maintenance principles as defined in RecommendationM.20 and applies to the basic rate access connected to the exchange via a multiplexer. The principle of controlled maintenance is applied for maintaining the static multiplexed basic rate access. Controlled maintenance is a method of sustaining a desired technical performance by the system- atic application of supervision, testing and performance sampling in order to minimize preventive maintenance and to reduce corrective maintenance. 2. Network configuration for maintenance activities Figure 1/I.605 shows the general reference configuration of the multiplexed basic rate access, connected via a digital link to the Exchange Termination (ET). FIGURE 1/I.605 Equipment configuration for maintenance of the multiplexed basic rate access Note 1 - The digital link, as defined in CCITT RecommendationG.701, can make use of a variety of trans- mission techniques and media complying with RecommendationsG.703 and G.704. Note 2 - The digital link may not be present. (Colocated configuration). 3. Relationship to the maintenance of the basic rate access The same principles as given in RecommendationI.603 for the ISDN basic rate accesses directly con- nected to the local exchange, should be applied. Therefore, the NT1 and LT for the basic rate accesses connected via a static basic access multiplexer to the local exchange must have the same functions as NT1 and LT for the basic rate accesses connected directly to the local exchange. (Loopback mechanism must be implemented according to RecommendationI.603.) In order to support these principles, operation and maintenance information has to be exchanged between the digital section for the ISDN basic rate access and the exchange termination (ET). This infor- mation is conveyed in the Cv1Channel, which is defined in RecommendationQ.512. This Cv1Channel is shown in Figure 2/I.605. FIGURE 2/I.605 Information exchange between the digital section for the ISDN basic rate access and the local exchange termination (ET) These functions, which are allocated within this Cv1Channel are defined in RecommendationG.960 on the digital section for the ISDN basic rate access. These functions can be classified according to: - activation/deactivation procedures; - error and status reporting to the exchange (ET); - failure localization within the digital section for the ISDN basic rate access; - conveyance of control information from the exchange (ET) to the digital section of the ISDN basic rate access. 4. Maintenance of the digital link and basic access multiplexer 4.1 Failure detection Unlike the ISDN basic access, the digital, link and basic access multiplexer are always in the active state (as seen by the exchange). Continuous automatic supervision, supervising the correct functioning of layer1 up to basic access multiplexer, is operating. This supervision is called continuous automatic supervision on layer1. 4.1.1 Functions applied to the ET The functions which are allocated to the ET are listed below: - detection of loss of incoming signal; - detection of loss of frame alignment; - detection of AIS; - detection of RAI; - generation of the frame signal; - CRC code generation; - RAI generation; -CRC monitoring of the incoming signal (basic access multiplexer to the ET); - detection of CRC error information; -CRC error reporting (ET to the basic access multiplexer) (optional); - AIS generation. The implementation of these functions should be the same as for the ET in the ISDN primary rate access, as defined in RecommendationI.604 for the exchange termination (ET). 4.1.2 Functions applied to the static basic access multiplexer The functions which are allocated to the basic access multiplexer are listed below: - detection of loss of incoming signal; - detection of loss of frame alignment; - detection of AIS; - detection of RAI; - generation of the frame signal; - CRC code generation monitoring of the incoming signal (network to basic access multiplexer) and detection of CRC error information (if provided from the ET); - CRC error reporting (basic access multiplexer to the ET). The implementation of these functions should be the same as for the NT2 in the primary rate access, as defined in RecommendationI.604. In addition, the following functions are allocated to the basic access multiplexer: - sending of AIS on the V4 interface, in case of a defect in the basic access multiplexer between the V1 reference point and the V4 interface of the multiplexer; - signalling to all the basic rate access the condition "out of service due to failure", in the case of a defect occurring in the basic access multiplexer, between the V1 reference point and the V4 inter- face of the multiplexer, and in the digital link. 4.1.3 Functions allocated to the digital links The functions, which are allocated to the digital links are: - detection of loss of incoming signal on either end and within the digital link; - generation and transmission of AIS within the digital link. 4.2 System protection xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx 4.9 Overall performance measurements See Recommendation I.603 for the performance related to the digital section of the basic rate access, and RecommendationI.604 for the V4 digital section.