Specifications

4-8 Cisco MGX 8220 Reference, Release 4.1
Frame Service Module
Figure4-6 BPX Network with Service Interworking Connections
The diagram shows an MGX 8220 unit and a FRSM to the right with three frame relay connection
endpoints. These connections indicate the frame relay ends of service interworking connections. The
diagram shows some possibilities for terminating the other ends of the connections:
• ATM FUNI (Framed UNI) port on an FRSM
• ATM UNI port on an AUSM
• ATM UNI port on a BPX 8620 ASI card
In addition to frame to cell and DLCI to VPI/VCI conversion, the service interworking feature maps
cell loss priority and congestion information between the frame relay and ATM formats. The service
interworking is full Frame Relay Forum (FRF.8) compliant and provides full support for routed and
bridged PDUs, transparent and translation modes, and VP translation.
Cell Loss Priority
Frame Relay to ATM Direction
Each frame relay to ATM service interworking connection can be configured as one of the following
Discard Eligibility (DE) to Cell Loss Priority (CLP) schemes:
• DE bit in the frame relay frame is mapped to the CLP bit of every ATM cell generated by the
segmentation process of the frame.
• CLP is always 0.
• CLP is always 1.