Specifications

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Cisco AS5800 Operations, Administration, Maintenance, and Provisioning Guide
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Chapter 6 Provisioning
Split Dial Shelves
The dial shelf is split by dividing the ownership of the feature boards between the two router shelves.
You must configure the division of the dial-shelf slots between the two router shelves so that each router
controls an appropriate mix of trunk and modem cards. Each router shelf controls its set of feature boards
as if those were the only boards present. There is no interaction between feature boards owned by either
router.
Split mode is entered when the dial-shelf split slots command is parsed on the router shelf. This can
occur when the router is starting up and parsing the stored configuration or when the command is entered
when the router is already up. On parsing the dial-shelf split slots command, the router frees any
resources associated with cards in the slots that it no longer owns, as specified by exclusion of slot
numbers from the slot-numbers argument. The router should be in the same state as if the card had been
removed from the slot; all calls through that card will be terminated. The configured router then informs
its connected DSCs that it is in split mode, and which slots it claims to own.
In split mode, a router shelf uses only half of the 1,792 available TDM timeslots. (See the “TDM
Resource Allocation” section on page 6-19.) If a dial-shelf split slots command is entered when the calls
using timeslots exceed the number that would be available to the router in split mode, the command is
rejected. (This should occur only when a change to split mode is attempted where the dial shelf has more
than 896 calls in progress, or more than half of the 1,792 available timeslots. Otherwise, a transition from
normal mode to split mode can be made without disturbing the cards in the slots that remain owned, and
calls going through those cards will stay up.)
TDM Resource Allocation
Trunk cards and modem cards are tied together across a time-division multiplexing (TDM) bus on the
dial-shelf backplane. Timeslots for the TDM bus are allocated by the router shelf on a call-by-call basis.
This is implemented by initializing a queue at start-up with one element for each usable timeslot
(currently 14*128 = 1,792 timeslots are used). Timeslots for a call are allocated from the front of the
queue and replaced at the end of the queue when the call is completed. For split-dial-shelf operation,
timeslots are added to the queue dynamically, as needed. When a TDM slot is required and the queue is
empty, a chunk of TDM slots is allocated to the queue.
In normal mode, the router shelf connected to the DSC in slot 12 allocates timeslots starting from 0 going
up, and the router shelf connected to the DSC in slot 13 allocates timeslots starting from 1,791 going
down. For split-dial-shelf operation each router is assigned half of the usable set of timeslots. The router
shelf connected to the DSC in slot 12 controls the first half of the timeslots (0 to 895). The router shelf
connected to the DSC in slot 13 controls the second half of the timeslots (896 to 1791).
Transition Procedure for Split Mode
To transition from normal mode to split mode, complete the following steps:
Step 1 Ensure that both DSCs and both router shelves are running the same Cisco IOS image.
Having the same version of Cisco IOS software running on both DSCs and both router shelves is not
mandatory; however, it is a good idea. There is no automatic check to ensure that the versions are the
same.
Step 2 Schedule a time when the Cisco AS5800 universal access server can be taken out of service without
unnecessarily terminating calls in progress.
The entire procedure for transitioning from normal mode to split mode should require approximately one
hour if the hardware is already installed.
Step 3 Busy out all feature boards and wait for your customers to log off.
Step 4 Reconfigure the existing router shelf to operate in split mode.