Specifications

MGX 8220 Service Modules 4-7
Frame Service Module
ATM to Frame Relay Direction
Each Frame Relay/ATM network interworking connection can be configured as one of the following
CLP to DE mapping schemes:
• If one or more ATM cells belonging to a frame has its CLP field set, the DE field of the frame
relay frame will be set.
• no mapping from CLP to DE.
Congestion Indication
Congestion on the Frame Relay/ATM network interworking connection is flagged by the EFCI bit.
The setting of this feature is dependent on traffic direction, as described in the following:
Frame Relay to ATM Direction
EFCI is always set to 0.
ATM to Frame Relay Direction
If the EFCI field in the last ATM cell of a segmented frame received is set, then FECN of the frame
relay frame will be set.
PVC Status Management
The management of ATM layer and FR PVC Status Management can operate independently. The
PVC status from the ATM layer will be used when determining the status of the FR PVC. However,
no direct actions of mapping LMI A bit to OAM AIS will be performed.
FR to ATM Service Interworking
By specifying “service interworking” as the channel type when adding a frame relay PVC to an
FRSM, all PVC data is subject to service interworking translation and mapping in both the frame
relay to ATM and ATM to frame relay directions.
Figure4-6 shows a BPX 8620 network with service interworking connections.