Avamprogetto 2b

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. “MD or ISDN-DN”), further investigations must be carried out jointly.