1、CCITT FASCICLE IV.3 * 4862593 0505358 T =I ANNEX A (to Recommendation M.36) Digital crossconnect system considerations for ISDN DCSs may also process the D-channel. They may break the D-channel layer 2, so that there are two tandem layer 2 links between the NT2 and the ET. The DCS routes layer 3 pac
2、kets from the NT2 either to the exchange or to the leased network based on the routing of the associated B-channel. Thus, the DCS may also act as a packet crossconnect for the D-channel. However, the DCS does not perform switch functions. Its crossconnect function is controlled over a separate admin
3、istrative link, not over the D-channel with 4.931 14 call control. This model also includes leased circuits. The B-channels traverse the network without terminating on a switch. The associated D-channel informa- tion can be carried in the leased network in the same digital paths as the B-channels, o
4、r separately from the B-channels, on the Signalling System No. 7 signalling network. References CCIT Recommendations of the 1.600-Series Maintenance principles for ISDN, Vol. III. CCIT Recornmendation General maintenance principles of ZSDN subscriber access and subscriber installa- tion, Vol. III, R
5、ec. 1.601. CCIT Recommendation Application of maintenance principles to ZSDN subscriber installation, Vol. III, Rec. 1.602. CCIT Recommendation Application of maintenance principles to ISDN basic accesses, Vol. III, Rec. 1.603. CCITT Recommendation Application of maintenance principles to ZSDN prima
6、ry rate access, Vol. III, Rec. 1.604. CCIT Recommendation Application ofmaintenance principles to static multiplexed ZSDN basic accesses, Vol. III, Rec. 1.605. CCIT Recommendation ISDN user network interface protocol for management, Vol. VI, Rec. 4.940. CCITT Recommendation Error performance of an i
7、nternational digital connection forming part of an integrated services digital network, Vol. III, Rec. G.821. CCITT Recommendation ISDN user-network interfaces - reference configurations, Vol. III, Rec. 1.41 1. CCITT Recommendation Reference model of open system interconnection for CCZTT application
8、s, Vol. VIII, Rec. X.200. CCITT Recommendation ZSDN protocol reference model, Vol. III, Rec. 1.320. CCITT Recommendation Open system interconnection (OSI) layer service definition conventions, Vol. VIII, Rec. X.210. CCIT Recommendation Exchange interfaces for subscriber access, Vol. VI, Rec. 4.512.
9、CCITT Recommendation ZSDN user-network interface layer 3 speciJication, Vol. VI, Rec. 4.93 1, Recommendation M.50 USE OF TELECOMMUNICATION TERMS FOR MAINTENANCE For their dealings with their colleagues in other countries, personnel at operation centres and other For maintenance technology, the definitions given in Recommendation M.60 are preferred. maintenance units should refer to Fascicle 1.3, Terms and Definition, of Volume I of this Book. 82 Fascicle IV.l - Rec. M.50
