1.1 General
Thls Functlonal Standard ls applicable to interworklng unlts concerned with the usc of ISO 8208 (X.25 Packet Level Protocol). An R/Cp.q relay provtdes the means for a System on one subnetwork to communicate with a System, or make use of faclllües. on another subnetwork.
Thls part of thls Functlonal Standard deflnes the R/C51.1121 proüle. whlch ls applicable to interworking unlts operatlng between CSMA/CD LAN subnetworks and PSONs using Virtual calls over a digital data clrcult/CSDN leased llne permanent access.
1.2 Position in the taxonomy
The taxonomy of proflles ls deflned in ISO TR 10000-2. Thls part of thls Functlonal Standard deflnes the proflle:
R/C51.1121 X.25 Protocol Relaylng: Relaylng between a CSMA/CD LAN subnetwork and a PSDN subnetwork using Virtual calls over a digital data clrcult/CSDN leased llne permanent access.
1.3 Scenario
Flgure 1 illustrates the conflguratlon of Systems to whlch the R/C51.1121 proflle ls applicable. The flgure shows two reference polnts. but tmplementatlons of R/C51.1121 proflles may lnclude any number of subnetwork attachments, with a reference polnts correspondlng to each.