Cisco Systems MGX 8230 manual Frame Relay-to-ATM Network Interworking, Congestion Indication

Chapter 2 Module and Service Descriptions

Frame Relay Service Modules

Frame Relay-to-ATM Network Interworking

Frame Relay-to-ATM network interworking (NIW) supports a permanent virtual connection (PVC) between two Frame Relay users over a Cisco network or a multi-vendor network. The traffic crosses the network as ATM cells. To specify NIW for a connection, add the connection with a channel type of “network interworking.” For an illustration of a BPX 8620 network with NIW connections, see Figure 2-12.

Figure 2-12 BPX 8620 Network with NIW Connections

FRAD	Frame Relay
	DS1
(router)		FRSM	MGX 8850

BPX 8620 network						Frame Relay
							DS1
			MGX 8850		FRSM		FRAD
							(router)
PVCs
				Frame Relay
	MGX 8430			DS1
		FRSM			FRAD		17908
					(router)

Congestion Indication for NIW Connections

In addition to frame-to-cell and DLCI to VPI/VCI conversion, the network interworking feature maps cell loss priority (CLP) and congestion information from Frame Relay to ATM formats. The CLP and congestion indicators can be modified for individual connections using the cnfchanmap command.

Frame Relay–to–ATM Direction

Each Frame Relay/ATM network interworking connection can be configured as one of the following DE to CLP mapping schemes:

•DE bit in the Frame Relay frame is mapped to the CLP bit of every ATM cell generated by the segmentation process.

•CLP is always 0.

•CLP is always 1.

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 below.

	Cisco MGX 8230 Edge Concentrator Installation and Configuration
Release 1.1.31, Part Number 78-11215-03 Rev. B0, May 2001		2-23