Cisco Systems 8600 Series manual ATF Connections, Simplified Example

Networking Interworking

The frame relay to ATM networking interworking function is available as follows:

•IPX switch frame relay (shelf/feeder) to IPX switch frame relay (either routing node or shelf/feeder).

•MGX 8220 frame relay to MGX 8220 frame relay.

•MGX 8220 frame relay to IPX switch frame relay (either routing node or shelf/feeder).

•IPX switch frame relay (either routing node or shelf/feeder) to BPX switch or MGX 8220 ATM port.

•

•

MGX 8220 frame relay to BPX switch or MGX 8220 ATM port.

In the items listed above, an IGX switch can be substituted for each instance of an IPX switch.

On the IPX switch, interworking is performed by the AIT card, and on the IGX switch by the BTM card. A simplified example of the connection paths is shown in Figure 12-6. In interworking, the AIT card receives FastPackets from the FRP, rebuilds the frames, and converts between frames and ATM cells. Data is removed from one package and placed in the other. Congestion information from the header is mapped to the new package. This processing by the AIT trunk card is called Complex Gateway. AIT trunk cards are required on every BPX switch to IPX switch hop in a Frame Relay to ATM connection’s path.

Figure 12-6 ATF Connections, Simplified Example

SV+ NMS

Some typical ATF connection paths shown:

Frame

Relay (T1)

Router

Frame Relay (T1)

(pvc2)

(pvc3)

IGX Shelf

FRM

UXM

BPX

BPX Hub

		Crosspt
		switch
ATM
	BNI		BNI
(T3/E3
Feeder
trunk

ATM		Frame
(T3/E3	AXIS	Relay (T1)
Feeder	shelf	(pvc2)
trunk

IGX

		ATM		Crosspt
Frame				switch
		(T3/E3/
Relay (T1)	CPE	OC-3	ASI		BNI
		(pvc1)
		(pvc3)

ATM (T3/E3/

OC-3 ATM (T3/E3

	FRM	(pvc1)
			Router
		Frame
UXM		Relay (T1)
		S5241

The cells within the frame are expected to possess the standard ATM Access Interface cell header. The traffic is assumed to have AAL-5 PDUs, and will not function properly otherwise (framing errors will result). Within the AAL-5 PDUs, the data must be packaged in standard frame relay frames, one frame per PDU (with respect to the AAL-5 layer).

The UPC and ForeSight algorithms are applied according to their configured values. The cell headers are converted into the proprietary Cisco WAN switching STI format before entering the network. The cells are delivered to their destination according to the configured route of the connection. Cells can be lost due to congestion.

12-6Cisco BPX 8600 Series Reference