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The Figure illustrates a typical Frame
Relay environment. The central site has a T1-speed local-loop
connection and the branch offices have slower (in this case, 9.6-Kbps) local-loop connections. In addition, the CIR for each PVC
going from the central site to each branch office is 9.6 Kbps.
In this environment, the following
process occurs:
- The central site may send data
across the T1-speed line. Even though the CIR is 9.6 Kbps, the
router continues to send the data based on the T1 rate.
- The data goes through the cloud.
- When the data reaches the local
loop that is connected to the branch office, a bottleneck occurs
because the data is being sent faster than the speed of the
branch-office local loop. At this point, packets are buffered at
the egress point of the network, increasing line response time
and (possibly) causing problems, particularly for
latency-sensitive protocols such as SNA.
The solution is to slow the speed at which the
central-site router is sending data. With the traffic shaping over
Frame Relay feature, you can define and enforce a rate on the VC at
which the router will send data. The pace you set can be the CIR,
EIR, or some other value.
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