220 APPENDIX 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)
The interworking scheme shown in Figure 161 works as follows:
n 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.
n 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.
Application
Null SSCS
AAL 5
SAR
ATM
PHY
Application
PHY
Q.922
DL Core
Null SSCS
AAL 5
SAR
ATM
PHY
PHY
Q.922
DL Core
ATM
Network
Frame
Relay DTE
ATM
DTE
Frame
Relay
Network
Frame
Relay DTE
ATM
Cells
LAPD Frames
Application
PHY
Q.922
DL Core
PathBuilder
S330/S310
