3Com S330 manual Service Interworking Function

220APPENDIX B: PATHBUILDER S330/S310 MODULE AND APPLICATION OVERVIEW

These interworking features are described in FRF.8 and FRF.5 respectively. The major difference between these two features is that there is no FR-SSCS function required for Service Interworking.

The following sections describe the details of these two interworking functions as well as the features provided by the PathBuilder S330/S310.

Service Interworking Function

Figure 161 shows a PathBuilder S330/S310 providing Service Interworking function between Frame Relay and ATM services. In this setup, a Frame Relay DTE communicates with an ATM DTE, regardless of the fact that there is a different type of DTE at each end of the connection.

Figure 161 Frame Relay/ATM Service Interworking Connection (FRF.8)

Frame	LAPD Frames
Relay DTE
							ATM
							Cells	ATM
											ATM
				PathBuilder
	Frame			S330/S310				Network			DTE
Frame
	Relay
Relay DTE						Application
	Network
							Q.922
						DL Core
							PHY
Application									Application
									Null SSCS
					Null SSCS
Q.922			Q.922							AAL 5
	AAL 5
DL Core		DL Core									SAR
					SAR
										ATM
					ATM
PHY
			PHY		PHY						PHY

The interworking scheme shown in Figure 161 works as follows:

■The application on the frame DTE passes its data through Q.922 core service with the assumption that there is an end-to-end pipe to carry its data from its end to the other DTE at the far end. The Q.922 core only sees a point-to-point link to the next connection point; it has no knowledge about the type of network behind the current link.

■On the other end, the application residing in ATM DTE passes its data through a NULL SSCS that sits on top of AAL5. What this ATM DTE sees is the ATM network to which it is connected.