12-4 Cisco BPX 8600 Series Reference
Networking Interworking
interface supported by the MGX 8220, e.g., ASI, AUSM. Translation between the Frame Relay and
ATM protocols is performed in accordance with RFC 1490 and RFC 1483.
Figure 12-4 Frame Relay to ATM Service Interworking Detail
Networking Interworking
In Network Interworking, in most cases, the source and destination ports are frame relay ports, and
the interworking function is performed at both ends of the connection as shown in Part A of
Figure 12-5.
If a frame relay port is connected across an ATM network to an ATM device, network interworking
requires that the ATM device recognize that it is connected to an interworking function (frame relay,
in this case). The ATM device must then exercise the appropriate service specific convergence
sublayer (SSCS), in this case the frame relay service specific convergence sublayer (FR-SSCS) as
shown in Part B of Figure 12-5.
S5236
ATM NW
Physical
ATM
SAR
CPCS
Upper
layers
B - CPE
Physical
ATM
SAR
CPCS
Upper
layers
B - CPE
Physical
ATM
BNM
Physical
ATM
AAL-5
Null SSCS
Physical
Frame Relay
Q.922
RFC 1483 RFC 1490
Physical
Q.922
Upper
layers
FRSM FR CPE
AXIS shelf
Physical
ATM
ASI
BPX
Physical
ATM
BNI
AXIS Shelf
Physical
ATM
BNM
Physical
ATM
AUSM
ATM T1/E1
ATM T3/E3
(feeder trunk)
ATM T3/E3
ATM T3/E3
(feeder trunk)
Narrowband NW
Frame Relay CPE connected to B-ISDN CPE
