Cisco Systems 8600 Series manual Tiered Networks, Service Interworking, Additional Information

BPX Switch Operation

Service Interworking

Figure 1-3shows a typical example of Service Interworking. Service Interworking is supported by the FRSM on the MGX 8220 and the UFM-C and UFM-U on the IGX switch. Translation between the Frame Relay and ATM protocols is performed in accordance with RFC 1490 and RFC 1483.

In Service Interworking, for example, for a connection between an ATM port and a frame relay port, unlike Network Interworking, the ATM device does not need to be aware that it is connected to an interworking function.

The frame relay service user does not implement any ATM specific procedures, and the ATM service user does not need to provide any frame relay specific functions. All translational (mapping functions) are performed by the intermediate IWF.

The following is a typical configuration for service interworking:

•

•

MGX 8220 Frame Relay (FRSM card) to BPX switch or MGX 8220 ATM port.

IGX switch Frame Relay (FRM-U or FRM-C) to BPX switch or MGX 8220 ATM port.

Figure 1-3 Frame Relay to ATM Service Interworking

Frame

Relay

CPE

Frame Relay

Service

interworking

function

ATM network

ATM

CPE using a

standard, non- service specific convergence protocol

H8226

Additional Information

For additional information about interworking, refer to Chapter 12, Frame Relay to ATM Network and Service Interworking.

Tiered Networks

Networks may be configured as flat (all nodes perform routing and communicate fully with one another), or they may be configured as tiered. In a tiered network interface shelves are connected to routing hubs, where the interface shelves are configured as non-routing nodes.

By allowing CPE connections to connect to a non-routing node (interface shelf), a tiered network is able to grow in size beyond that which would be possible with only routing nodes comprising the network.

Starting with Release 8.5, in addition to BPX switch routing hubs, tiered networks now support IGX switch routing hubs. Voice and data connections originating and terminating on IGX switch interface shelves (feeders) are routed across the routing network via their associated IGX switch routing hubs. Intermediate routing nodes must be IGX switches, and IGX switch interface shelves are the only interface shelves that can be connected to an IGX switch routing hub. With this addition, a tiered network can now provide a multi-service capability (frame relay, circuit data, voice, and ATM).

Introduction 1-9