ATM and Frame Relay SVCs, and SPVCs 8-7
Network Interworking Between Frame Relay and ATM
Figure 8-4 ESP Signaling PVC
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.)
ESP 1
ATM
NIC
BXM
BPX switch 1
WAN Service Node WAN Service Node
ESP 2
ATM
NIC
S6363
BNI
BXM
BPX switch 2
BNI
Local
VPI/VCI
Trunk
Network-to-Network
Interface (NNI)
Remote
VPI/VCI
