3Com SuperStack II PathBuilder S330 Reference Manual page 233

The PathBuilder S330/S310 sitting in the middle performs all the required
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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
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to Q.922
Performing Frame PVC management
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Managing traffic
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Handling congestion
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Network Interworking Function
Figure 162 shows a PathBuilder S330/S310 providing Network Interworking
function between Frame Relay and ATM services.
Figure 162 Frame Relay/ATM Network Interworking Connection (FRF.5)
Frame
Relay
DTE
Frame
Frame
Relay
Relay
DTE
Network
Application
Q.922
DL Core 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
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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
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DTE.
PathBuilder ATM
Network
S330/S310
FR-SSCS
Q.922
AAL 5
SAR
ATM
PHY PHY
Serial Interface
Frame
Relay
Network
PathBuilder
S330/S310
FR-SSCS
Q.922
AAL 5
DL Core
SAR
ATM
PHY PHY
221
Frame
Relay
DTE
Frame
Relay
DTE
Application
Q.922
DL Core
PHY