Projet 2b

Area of responsibility of CSP LEMF site nonnon --coincidentcoincident LEMF MDMDMD LILI--HPHP

Access LineAccess LineAccess Line GWGWGW LELE NTNTNT DNDN--HPHP MDMDMD hostinghostinghosting FacilityFacilityFacility DN ProviderDN ProviderDN Provider DN ProviderDN ProviderDN Provider Area of responsibility FacilityFacilityFacility FacilityFacilityFacility of PTSS Area of responsibility of ISDN-- DN ProviderDN Provider

InitialInitialInitial AddressAddressAddress MessageMessageMessage (IAM)(IAM)(IAM) SETUPSETUPSETUP MessageMessageMessage AnswerAnswerAnswer MessageMessageMessage (ANM)(ANM)(ANM) CONNECTCONNECTCONNECT MessageMessageMessage TargetTargetTargetTarget ‘‘‘’ssss CommuniCommuniCommuniCommuni ---- CCCCCC ---linklinklink cationcationcationcation ReleaseReleaseRelease MessageMessageMessage (REL)(REL)(REL) DISCONNECT/RELEASEDISCONNECT/RELEASEDISCONNECT/RELEASE MessageMessageMessage

failedfailedfailed

LostLostLost

ReleaseReleaseReleaseRelease CompleteCompleteCompleteComplete MessageMessageMessageMessage (RLC)(RLC)(RLC)(RLC) ^{subsequentsubsequentsubsequentMessagesMessagesMessagesaccordingaccordingaccordingto ITUto ITUto ITU---T Rec. Q.931T Rec. Q.931T Rec. Q.931}

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Figure 26: Signalling sequences for release of a CC link as a result of an error detected in the ISDN delivery network

NOTE: If an error is detected by the ISDN delivery network, the cause may also lie outside of this network (see table of cause values).

The REL messages at the handover point between the CSP and the ISDN-DN provider and at the handover point between the PTSS and the ISDN-DN provider contain the same cause value indicating the location of the error.

Table 4 shows all cause values that can occur, as specified by the universal service licensee (based on the corresponding international standards). The CSP’s incoming network receives information on which entity has caused an error. In principle, all the CSP needs to know is whether it has caused the error itself. In the case of an error with the ISDN-DN or the LEMF,

the CSP has to send a message to the ISDN-DN provider and/or the PTSS, as the case may be. The detailed determination of the reason falls under the responsibility of the ISDN-DN provider or the PTSS. In cases where the cause is not clear (e.g. “ISDN-DN or MD”), further investigations shall be carried out jointly.

Table 4: Cause values and location in case of release of a CC link as a result of an error detected in the ISDN delivery network

ITU-T Q.850 (05/98) Cause Definition Location Failure caused by value

31 Normal, Unspecified Other than user (0000) MD or ISDN-DN or LEMF

38 Network Out of Order Other than user (0000) ISDN-DN or LEMF

41 Temporary Failure Other than user (0000) ISDN-DN

102 Recovery on Timer Expiry Other than user (0000) MD or ISDN-DN or LEMF

111 Protocol Error, Unspecified Other than user (0000) MD or ISDN-DN or LEMF