Cisco Systems 8600 Series manual Network Interworking Between Frame Relay and ATM

Network Interworking Between Frame Relay and ATM

Figure 8-4 ESP Signaling PVC

WAN Service Node

ESP 1

ATM

NIC

Local

VPI/VCI

BXM

BNI

BPX switch 1

Network-to-Network

Interface (NNI)

Trunk

Remote

VPI/VCI

WAN Service Node

ESP 2

ATM

NIC

BXM

BNI

BPX switch 2

S6363

Network Interworking Between Frame Relay and ATM

Because the BPX switch is an ATM switch, Frame Relay SVCs that are setup and established across the Cisco StrataCom network must be translated into an ATM format to be carried across the network. At the far end, where typically the connection is terminated on another Frame Relay CPE, the ATM cells will have to be converted back to Frame Relay format. This is referred to as Network Interworking. Network Interworking can be performed between Frame Relay CPE and ATM CPE when the ATM CPE recognizes that it is connected to an interworking function (Frame Relay, in this case). The ATM CPE must then exercise the appropriate service specific convergence sublayer (SSCS). The SSCS will then convert the ATM cells to Frame Relay traffic.

In this release of the BPX switch with ESP, all Frame Relay SVC connections must be between Frame Relay CPE (that is, Frame Relay end users) or ATM CPE that is aware that it is performing Network Interworking, and all ATM SVC connections must be between ATM CPE (that is ATM end users). In other words, Service Interworking between ATM and Frame Relay SVCs is not supported in this release. (ATM and Frame Relay Service Interworking for PVCs is supported by the BPX switch.)

ATM and Frame Relay SVCs, and SPVCs 8-7