Fractional T1/E1 allows one or more DS0 channels to be bundled together (up to the maximum bandwidth of the network link), allowing the customer to use only that portion of the link that is needed. This means that the PPP service can use a selected number of timeslots (octets) in the network T1 or E1 link, thus reducing the amount of T1 or E1 bandwidth that must be leased or purchased from the attached carrier. This leads to multiplexing efficiencies in the transport network.
The following cards and platforms support fractional T1/E1 on a PPP channel group (encapsulation type ppp-auto), or all timeslots on T1/E1 ports, in network mode:
16-port T1/E1 ASAP Adapter card
32-port T1/E1 ASAP Adapter card
T1/E1 ports on the 4-port T1/E1 and RS-232 Combination module (on 7705 SAR-H)
T1/E1 ports on the 7705 SAR-A
T1/E1 ports on the 7705 SAR-M
T1/E1 ports on the 7705 SAR-X
Only one channel group can be configured per port. When the channel group is configured for ppp-auto encapsulation and network mode, all timeslots (channels) are automatically allocated to the channel group. The user can then configure the number of timeslots needed. Timeslots not selected cannot be used.