ÿWPCL ûÿ2BJ|xÐ ` ÐÐÌÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿH øÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÌÐÐ °°°è ÐÑ Âx„|ü@Ž ÑÐ Å°6Ø'°6Ø'Å ÐÓÓÃÃRecommendation I.602ÄÄ Ð  ÐÁàh$ÁAPPLICATION OF MAINTENANCE PRINCIPLES TO ISDN SUBSCRIBER INSTALLATIONƒ 1.ÁHÁÃÃScope of applicationÄÄ Ð Ð ÐÁHÁThis Recommendation presents the possible elementary functions for the maintenance of the subscriber installation. The functions are to be considered as optional, except when needed to meet specific network interface requirements found in Recommendations I.430 and I.431. ÁHÁThese functions can be controlled by the local side (e.g. from the subscriber premises) and by a remote side (i.e. from an MSP, as described in Recommendation I.601). ÁHÁIt is the responsibility of the subscriber installation to ensure that only authorized MSPs are given access to the following functions. 2.ÁHÁÃÃNetwork configuration for maintenance activitiesÄÄ ÁHÁFigure 1/I.602 is the basis for the general maintenance principles of the ISDN subscriber installation. ÁHÁSAMC: Subscriber Access Maintenance Centre ÁHÁSIME: Subscriber Installation Maintenance Entities ÁHÁMSP:  Maintenance Service Provider ÃÃNoteÄÄ © In some countries the subscriber installation is allowed to control certain maintenance functions in the subscriber access without authorization of an SAMC. ÁàHHÁFIGURE 1/I.602ƒ ÁàH/ÁÃÃConfiguration for the Maintenance of the Subscriber InstallationÄă 3.ÁHÁÃÃAutomatic supervisionÄÄ 3.1ÁHÁÃÃContinuous automatic supervision on layer 1ÄÄ 3.1.1ÁHÁÃÃGeneralÄÄ ÁHÁThis supervision may be realized by permanent automatic mechanisms located in the pieces of equipment of the subscriber installation (see definition in Figure 1/I.602). ÁHÁThese automatic mechanisms are operational during the active period of the subscriber basic access. They are designed to detect malfunctioning of particular items, e.g. power supply, quality level of transmission, incoming signal, frame alignment. 3.1.2ÁHÁÃÃSubscriber installation functionsÄÄ ÁHÁThe following functions may be supervised: ÁHÁ©Âà  Âmonitoring of operation functions within the subscriber installation (e.g. power supply);ÆÆ ÁHÁ©Âà  Âsupervision of information related to or received from the digital transmission section.ÆÆ 3.2ÂàHÂÃÃAutomatic supervision on layer 2 and layer 3 of the D©Channel protocolÄÄÆÆ ÁHÁThis activity covers supervision of activities on layers 2 and 3 of the D©Channel protocol. Automatic supervision on layers 2 and 3 may be made by self©acting mechanisms implemented in the subscriber installation. ÁHÁThere are three categories of automatic supervision which may be performed by layer 2 and layer 3 of the D©channel protocol: ÁHÁ©Âà  Âservice provision incapability detection (e.g. detection of incapability of layer 2 to establish a data link connection);ÆÆ ÁHÁ©Âà  Âprotocol misoperation detection;ÆÆ ÁHÁ©Âà  Âerror monitoring (e.g. 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.ÁHÁÃÃInternal testsÄÄ 4.1ÁHÁÃÃInternal test of the TE1 and TAÄÄ ÁHÁSome of the TEs/TAs may manage internal tests for all or parts of their functionalities. The internal tests may be activated either automatically by the TE and TAs or by a local command on the TE and TAs or by a remote request. ÁHÁSome of these tests are dependent on the terminal type. Such tests shall not affect the user©network interface, i.e. no test signals shall be transmitted across the interface when a test is in operation. ÁHÁThe terminal equipment may have the ability to abort an internal test sequence, for example, in case of an incoming call attempt. If this test has been requested by a MSP, the subscriber installation should report it to the requesting MSP. ÁHÁThe results of an internal test procedure execution should be passed or failed and in the latter case an additional diagnostic information may be given. 4.2ÁHÁÃÃInternal test of the NT2ÄÄÔ ñ,ÔŒ ÁHÁThe subscriber should have facilities which can help to verify that the subscriber installation is not affected by a failure. Definitions of these procedures and functions require further study. ÁHÁThe functionalities may be similar to the ones presented for the TE and TA in ÀÀ 4.1. ÁHÁThe following internal tests of the NT2 have been identified: 4.2.1ÁHÁÃÃContinuity testÄÄ ÁHÁThe objective is to verify that the internal S interfaces of the NT2 can be activated. The mechanism which is implemented in the NT2 could be based on a normal activation of the layer 1 of the interfaces. ÁHÁThe principle for such a test is the same as the one defined for the local exchange function (see Recommendation I.603, ÀÀ 3.3). 4.2.2ÁHÁÃÃS interface check using loopback 3ÄÄ ÁHÁThe loopbacks are shown in ÀÀ 7/I.602. The results could be used for failure localization particularly in the case where the NT2 functions are distributed. 4.2.3ÁHÁÃÃTest call of the terminal equipment from the NT2ÄÄ ÁHÁAn NT2 may address one particular terminal equipment of the installation. Thus, it easily controls a test call. This procedure would allow the NT2 to verify the connection of the TE or TA to the installation and also to check layers 1, 2 and 3 operating conditions (e.g. response time supervision). ÁHÁThe test call could be initiated by the SIME. ÁHÁThe test call could be a normal call made for maintenance purposes. 5.ÁHÁÃÃTest call from the MSPÄÄ ÁHÁFurther study is required, especially concerning charging and authorization aspects. 6.ÁHÁÃÃCall to a test responder from the subscriber installationÄÄ ÁHÁMSP may provide test responders that are accessed via normal call procedures. There may be test responders for various teleservices and bearer services. ÁHÁThe selection of the service involved with the test call is made using the lower layer and higher layer compatibility information elements as defined for the normal call control procedures. 7.ÁHÁÃÃLoopbacksÄÄ 7.1ÂàHÂÃÃLocations of loopbacks associated with the subscriber installationÄÄÆÆ ÁHÁLoopback locations for failure localization and verification are shown in Figure 2/I.602. ÁàHHÁFIGURE 2/I.602ƒ ÁàHOÁƒ ÁàH0ÁÃÃLoopback locations associated with the subscriber installationÄă 7.2ÁHÁÃÃLoopback characteristics for basic rate subscriber installationsÄÄ ÁHÁCharacteristics of loopbacks are given in Table 1/I.602 ÁàHIÁTABLE 1/I.602ƒ ÁàHOÁƒ ÁàH<ÁÃÃCharacteristics of loopback mechanismsÄă ÁàH?ÁÃÃfor ISDN subscriber installationsÄă ÃÃNote 1ÄÄ © This loop might also be controlled by signalling in the B Channel as specified in the X© and V©Series Recommendations. ÃÃNote 2ÄÄ © Activation/deactivation of loopback 3 may be initiated by request from a MSP (by management messages carried via layer 3 in the D Channel). However, the generalization of the test pattern over the loopback would be by the NT2. ÃÃNote 3ÄÄ © From a technical viewpoint, it is desirable that loopback 3 can always be implemented (although not mandatory) and so the design of protocols for loopback control should include the operation of loopback 3.Ô ñ,ÔŒ ÃÃNote 4ÄÄ © Whether the loopback is transparent or non©transparent is an implementor's decision. Whether or not a transparent loopback is used, the loopback should not be affected by configurations and conditions beyond the point at which the loopback is provided e.g. by the presence of short circuits, open circuits or foreign voltages. 7.3ÂàHÂÃÃLoopback characteristics for primary rate subscriber installationsÄÄÆÆ ÁHÁCharacteristics of loopbacks are given in Table 2/I.602 TABLE 2/I.602 ÃÃCharacteristics of optional loopbacks for primary rate accessÄÄ Ð ð ÐÃÃNote 1ÄÄ © Transfer of layer 3 service messages may take place between TE (or NT2) and the exchange prior to the use of the layer 1 control mechanism. However, there are situations where the TE (or NT2) may not receive a reply: ÁHÁa)Âh   Âthe message may not be transmitted when the interface is in a failure situation;ÆÆ ÁHÁb)Âh   Âa network that does not support layer 3 signalling option need not respond.ÆÆ Definition of layer 1 control signals from TE (or NT2) towards NT1 remains for further study. ÃÃNote 2ÄÄ © Loopback B, is applicable to each individual interface at reference point S. ÃÃNote 3ÄÄ © The different part B, H0 and H11 channel loopbacks are controlled by separate control signals. However, several per channel loopbacks may be applied at the same time. ÃÃNote 4ÄÄ © The signal toward ET from the NT1 needs further study. ÃÃNote 5ÄÄ © For 1544 kbit/s interface. ÃÃNote 6ÄÄ © For 2048 kbit/s interface. ÃÃNote 7ÄÄ © Activation/deactivation of loopback 3 may be requested from a maintenance service provider (MSP). ÃÃNote 8ÄÄ © From a technical viewpoint, it is however desirable that loopback 3 always be implemented (though it is not mandatory) and so the design of protocols for loopback control should include the operation of loopback 3. 8.ÁHÁÃÃStatus requestÄÄ ÁHÁA piece of equipment i.e. NT2, TE, TA may have different states regarding its operation and/or maintenance conditions, e.g. in service, out of service, under tests, etc. ÁHÁThese states may be defined in the future. ÁHÁA MSP may request a SIME in the subscriber installation to indicate the current status of a particular terminal and/or of the connected terminal equipment. 9.ÁHÁÃÃFailure report to MSPÄÄ ÁHÁA subscriber installation which has detected that a TE is in a failed condition (e.g. when it is detected that a threshold has been exceeded) may have the ability to inform (via the ISDN), immediately, the MSP responsible for the concerned TE. ÁHÁAfter reception of such an information, the MSP may initiate a more precise failure localization. 10.ÁHÁÃÃInterrogation of parameter values and countersÄÄ ÁHÁA MSP may have the ability to access basic information, such as instantaneous value of a parameter or counter.