Avamprogetto 2b

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

Access LineAccess LineAccess Line NTNTNT GWGWGW LELE DNDN--HPHP MD HostingFacilityFacilityFacility DN ProviderDN ProviderDN Provider DN ProviderDN ProviderDN Provider FacilityFacilityFacility FacilityFacilityFacility Area of responsibility Area of responsibility of ISDN--DN ProviderDN Provider of the PTSS

InitialInitialInitial AddressAddressAddress MessageMessageMessage (IAM)(IAM)(IAM) SETUPSETUPSETUP MessageMessageMessage AddressAddressAddress CompleteCompleteComplete MessageMessageMessage (ACM)(ACM)(ACM) TargetTargetTarget ‘‘‘sss

CommuniCommuniCommuni --- ReleaseReleaseReleaseRelease MessageMessageMessageMessage (REL)(REL)(REL)(REL) DISCONNECT/RELEASEDISCONNECT/RELEASEDISCONNECT/RELEASE MessageMessageMessage failedfailedfailedfailed

cationcationcation ReleaseReleaseReleaseRelease CompleteCompleteCompleteComplete MessageMessageMessageMessage (RLC)(RLC)(RLC)(RLC) subsequentsubsequentsubsequent MessagesMessagesMessages accordingaccordingaccording to ITUto ITUto ITU ---T Rec. Q.931T Rec. Q.931T Rec. Q.931 ttt

LostLostLost contentcontentcontent

Figure 24 Signalling sequences for release during set-up of a CC link by the ISDN delivery network

The REL message at the handover point between the CSP and the ISDN-DN provider contains a cause value that indicates the location of the error.

Table 1 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. 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.