3Com S330 manual Network Interworking Function

Serial Interface 221

■The PathBuilder S330/S310 sitting in the middle performs all the required translation and management functions between these two networks, implementing the stacks as indicated in Figure 162 and performing the following key functions:

■Translating from Q.922 Frame to ATM AAL5 PDU and from ATM AAL5 PDU to Q.922

■Performing Frame PVC management

■Managing traffic

■Handling congestion

Network Interworking Function

Figure 162 shows a PathBuilder S330/S310 providing Network Interworking function between Frame Relay and ATM services.

Frame

Relay

DTE

Figure 162 Frame Relay/ATM Network Interworking Connection (FRF.5)

Frame

Relay Frame

Network Relay

DTE

Frame

Relay

DTE

Application

Q.922

DL Core

PHY

Frame PathBuilder

Relay S330/S310

Network

Q.922	FR-SSCS
	AAL 5
DL Core
	SAR
	ATM
PHY	PHY

ATM	PathBuilder
Network	S330/S310

FR-SSCS		Q.922
AAL 5
	DL Core
SAR
ATM
		PHY
PHY

Frame

Relay

DTE

Application

Q.922

DL Core

PHY

In the interworking scheme shown in Figure 162, a Frame Relay DTE communicates with the other Frame Relay DTEs through an ATM network. Note that FR-SSCS is used in this configuration.

This interworking scheme works as follows:

■The Frame Relay DTE at either end works exactly the same way as the Frame Relay DTE in the Service Interworking configuration: it passes its data through Q.922 core service, assuming that there is an end-to-end pipe to carry its data from its end to the other DTE at the far end.

■On the other end, the application resides in a Frame DTE instead of an ATM DTE.