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Frame Relay Network (FRN) Interworking (FRF.5) 57
Model 3096RC G.SHDSL T-DAC Administrators’ Reference Guide 6 • Configuring FR and ATM features
Observe from the stack that a true conversion has occurred between the FR and ATM networks. In FRF.5 the
uppermost sublayer is FR-SSCS, but in the FRF.8 Interworking Agreement, it is null SSCS.
The third application is called Ethernet-based Frame Relay/ATM. While FRF.5 and FRF.8 has a fixed map-
ping of DLCI PVCs to ATM VCI/VPIs, with Ethernet-based FR/ATM there is not a fixed mapping from FR
to ATM. We now have the ability to do routing between any of the three ports—Ethernet, serial (PPP or FR),
and DSL (ATM) ports. Nevertheless FRF.5/FRF.8 may operate simultaneously. An example of Ethernet-based
FR/ATM is a 3086FR in a company’s office. All three ports are connected through the integrated router. The
serial port (PPP or FR) with the WAN connection (ATM) via the DSL port. See
figure 16. For additional
details, see section “Frame Relay (Ethernet-based) operations” on page 74.
Figure 16.
Example Ethernet-based FR/ATM application
The PCs on the private side of the firewall have access to the web server in the DMZ and the Internet. Outside
users have access to the web server in the DMZ but cannot access the PCs on the company’s private network
(intranet) unless first accessed by one of the company’s PCs behind the firewall.
Frame Relay Network (FRN) Interworking (FRF.5)
Frame Relay Networking (FRN) Interworking (FRF.5) is a mapping and encapsulation mechanism by which
Frame Relay networks can communicate with ATM networks for transporting Frame Relay traffic. As
described in the introduction to this chapter, there are two scenarios. One characteristic of FRF.5—as opposed
to FRF.8—is the necesity to support the Frame Relay Service Specific Convergence Sublayer (FR-SSCS). The
Model 3086FR in FRF.5 mode supports all of the required Interworking Functions (IWF) required for Frame
Relay Network Interworking operation.
The Frame Relay Network Interworking functions are defined by the Frame Relay Forum specification Frame
Relay/ATM PVC Network Interworking Implementation Agreement FRF.5.