22-4
Cisco BPX 8600 Series Installation and Configuration
Release 9.3.30, Part Number 78-12907-01 Rev. E0, May 2005
Chapter 22 Configuring Frame Relay to ATM Network and Service Interworking
Service Interworking
Service Interworking
In Service Interworking, the ATM port connected to a Frame Relay port does not need to be aware that
it is connected to an interworking function. However, in Network Interworking, the ATM device
does
need to be aware that it is connected to an interworking function.
The ATM device uses a standard service specific convergence sublayer, instead of using the Frame Relay
FR-SSCS (see Figure 22-4).
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 ATM endpoints may be any ATM UNI/NNI interface supported by the MGX 8220 or MGX 8800,
such as BXM and AUSM. Translation between the Frame Relay and ATM protocols is performed in
accordance with RFC 1490 and RFC 1483.
Figure 22-4 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 22-5.
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 22-5.
35750
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
MGX 8220
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
Summary of Contents for BPX 8650
Page 49: ...P A R T 1 The BPX Switch ...
Page 50: ......
Page 159: ...P A R T 2 Installation ...
Page 160: ......
Page 273: ...P A R T 3 Initial Configuration and Network Management ...
Page 274: ......
Page 311: ...P A R T 4 Configuring Connections ...
Page 312: ......
Page 487: ...P A R T 5 Troubleshooting and Maintenance ...
Page 488: ......
Page 533: ...P A R T 6 BPX Specifications ...
Page 534: ......
Page 555: ...P A R T 7 Appendices ...
Page 556: ......