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100
C
4: P
B
HAPTER
ATH
UILDER
S600 M
A
ODULE AND
PPLICATION
Frame Relay Interworking Functions
The PathBuilder S600 provides two functions to interconnect a frame relay
network with an ATM network:
Service Interworking
n
Network Interworking
n
These interworking features are described in FRF.5 and FRF.8 respectively. As far as
the interworking function is concerned, 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 functions as well as the
features provided by the PathBuilder S600.
Service Interworking Function Figure 67 shows an PathBuilder S600 with
Service Interworking function between a Frame Relay and ATM services. In this
setup, a Frame Relay DTE will be communicating with an ATM DTE, but neither
one knows there is a different type of DTE sitting at the other end.
In this interworking scheme, the application on the frame DTE passes its data
through Q.922 core service. It assumes there is an end-to-end pipe to carry its data
from its end to the other DTE at the far end.
Figure 67 Frame Relay/ATM Service Interworking Connection
LAPD Frames
Frame
Relay DTE
Frame
Frame
Relay
Relay DTE
Network
Application
Q.922
DL Core
PHY
The Q.922 core sees only a point-to-point link to the next connection point. It has
no knowledge about what type of network is 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 AAL 5. What this ATM DTE sees is the ATM network to
which it is connected. The PathBuilder S600 sitting in the middle performs all the
required translation and management functions between these two networks and
implements the stacks as indicated above in Figure 67.
O
VERVIEW
ATM
Cells
PathBuilder
S600
Application
Q.922
DL Core
PHY
Null SSCS
AAL 5
Q.922
DL Core
SAR
ATM
PHY
PHY
ATM
ATM
Network
DTE
Application
Null SSCS
AAL 5
SAR
ATM
PHY
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