Configuring Fractional T3

You can configure fractional T3 on T3 frame interfaces. E3 frame interfaces do not support fractional E3.

Fractional T3 is a portion of a T3 transmission service and provides a set of lines with a speed that is greater than T1 (1.544 Mbps), but less than T3 (44.736 Mbps).

To configure fractional T3:

1. Set the DSU mode for the lines.
2. Set the speed of the fractional T3 lines.
3. Enable scrambling of the payload.

   Caution: Complete all three steps at the same time. Otherwise, the interface might drop packets unexpectedly.

dsu bandwidth

• Use to set the speed for the fractional T3 lines.
• If you issue this command, be sure to issue the dsu mode and scramble commands. Otherwise, the interface might drop packets unexpectedly.
• The router offers a set of speeds in increments that depend on the DSU mode you specify. The actual speed of the fractional T3 lines will be the value closest to the fractional bandwidth you specify.
• Example

  host1(config-controll)#dsu bandwidth 10000

• Use the no version to clear the bandwidth.
• If you issue the no version, be sure to issue the no dsu mode and no scramble commands. Otherwise, the interface might drop packets unexpectedly.
• See dsu bandwidth.

dsu mode

• Use to set the DSU mode for the lines.
• Specify 0 for Digital Link mode or 2 for Larscom mode.
• If you issue this command, be sure to issue the dsu bandwidth and scramble commands. Otherwise, the interface might drop packets unexpectedly.
• Example

  host1(config-controll)#dsu mode 0

• Use the no version to clear the DSU mode.
• If you issue the no version, be sure to issue the no dsu bandwidth and no scramble commands. Otherwise, the interface might drop packets unexpectedly.
• See dsu mode.

scramble

• Use to enable cell scrambling on a T3 frame interface.
• If you issue this command, be sure to issue the dsu mode and dsu bandwidth commands. Otherwise, the interface might drop packets unexpectedly.
• Example

  host1(config-controll)#scramble

• Use the no version to turn off cell scrambling on the interface.
• If you issue the no version, be sure to issue the no dsu mode and no dsu bandwidth commands. Otherwise, the interface might drop packets unexpectedly.
• See scramble.

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