1-8 Cisco BPX 8600 Series Reference
BPX Switch Operation
• MGX 8220 frame relay to IGX switch or IPX switch frame relay (either routing node or
shelf/feeder)
Part B of Figure 1-2 shows a form of network interworking where the interworking function is
performed by only one end of the ATM network, and the CPE connected to the other end of the
network must itself perform the appropriate service specific convergence sublayer function. The
following are example configurations:
• IGX switch or 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.
Network Interworking is supported by the FRP on the IPX switch, the FRM, UFM-C, and UFM-U
on the IGX switch, and the FRSM on the MGX 8220. The Frame Relay Service Specific
Convergence Sublayer (FR-SSCS) of AAL5 is used to provide protocol conversion and mapping.
Figure 1-2 Frame Relay to ATM Network Interworking
H8225
CPE
Part A
Network interworking connection from CPE Frame Relay port
to CPE Frame Relay port across an ATM Network with the
interworking function performed by both ends of the network.
Part B
Network interworking connection from CPE Frame Relay port
to CPE ATM port across an ATM network, where the network
performs an interworking function only at the Frame Relay end
of the network. The CPE receiving and transmitting ATM cells at
its ATM port is responsible for exercising the applicable service
specific convergence sublayer, in this case, (FR-SSCS).
Frame
Relay
Frame
Relay
Frame
Relay
Frame
Relay
ATM
ATM network
FR-SSCS
Inter-
working
function
B-ISDN
FR-SSCS
Inter-
working
function
B-ISDN
CPE
CPE
Frame
Relay
Frame
Relay
Frame
Relay
ATM network
FR-SSCS
Inter-
working
function
B-ISDN
CPE
exercises
appropriate
SSCS
B-ISDN
FR-SSCS
