
Configuring ATM Services
A-28 114056 Rev. A
Parameter: Xmit Sustainable Cell Rate (cells/s)
Path: Configuration Manager > Protocols > ATM > Service Records
> PVC
Default: 2358
Options: 300 through 365566 (ATM FRE2 OC-3 SONET/SDH ILI pairs)
0, 128 through 353207 (ATM ARE OC-3 SONET/SDH ILI pairs and
Model 5780 ATM routers)
0, 128 through 96000 (ATM ARE DS-3 ILI pairs)
0, 128 through 80000 (ATM ARE E-3 ILI pairs; G832 Framing Mode)
0, 128 through 72000 (ATM ARE E-3 ILI pairs; G751 Framing Mode)
Function: Specifies the upper limit of the ATM connection conforming average rate. The
average rate equals the total number of cells transmitted, divided by the duration
of the connection.
Using the sustainable cell rate (SCR), you can define the future cell flow of a VC
in greater detail than by just using the peak cell rate.
For ATM FRE2 ILI pairs, specifying the SCR controls the rate over time -- not
at a specific instant of time -- and can help you more efficiently use your
network resources.
For ATM ARE ILI pairs and Model 5780 ATM routers, the SCR maps directly to
the minimum cell rate (MCR). The MCR defines the minimum amount of
guaranteed bandwidth allowed for PVCs and Control VCs on the ATM line.
When setting the SCR for ATM FRE2 ILI pairs, keep the following in mind:
• The SCR is essentially a future average. By setting the SCR you are
specifying the cell rate, over time, to which you want the VC to conform.
• To be useful, the SCR must not exceed the PCR.
• If you know the user average rate, set the SCR about 10 percent higher than
this value.
• ATM FRE2 ILI pairs require a minimum SCR value of 300 cells/s. PVCs may
fail to operate with SCR values less than 300 cells/s.
(continued)
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