
Configuring ATM Services
11-6 114056 Rev. A
Setting the MBS
For ATM FRE2 ILI pairs, the MBS is the maximum length of a cell stream
allowed on a particular VC. The MBS specifies the maximum number of
sequential cells allowed on a VC before that VC must relinquish bandwidth to
other VCs waiting to transmit. This burst occurs at or close to the Peak Cell Rate.
When setting the MBS, we suggest that you select a value larger than the largest
packet your PVC or Control VC can transmit (that is, the Maximum AAL CPCS
Transmit SDU size). For example, if your VC accepts packets that are less than
2358 bytes long (PVC default), set your MBS value between 45 and 50 cells.
By default, the MBS is set to 40 cells. However, you can adjust this value from 1
through 65535 cells.
As a guideline, use this formula to determine your MBS value:
For additional information about traffic parameters, refer to “ATM Traffic
Parameters” in Chapter 2.
Note: ATM ARE ILI pairs ignore the maximum burst size.
Site Manager: Xmit Burst Size (cells): page A-59
Maximum Packet Size (in bytes)
48 bytes/cell
= MBS value (in cells)
for example:
4608 bytes (default)
48 bytes/cell
= 96 cells
ATM0016A
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