Network Card User Manual

Cisco AS5800 Product Overview 1-11
Cisco 5814 Dial Shelf
The first time a router shelf sends an inventory response to the DSC, it includes a flag indicating that
all dial shelf cards should be reloaded. In split mode, the final dial shelf card image is downloaded
by each DSC from the router shelf that owns it.
Slot Ownership Arbitration
The DSCs communicate between themselves to determine which one is to be active, where “being
active” implies being the master for all the dial shelf card slots. In split mode, each DSC is the master
for the set of dial shelf cards in the slots owned by its connected router. Additional messages indicate
when DSCs are in split mode and what set of slots they control.
A DSC that is already in split mode simply advertises that it is in split mode and which slots it is
claiming. When a second DSC receives an indication that the first DSC is in split mode, its behavior
depends on the current configuration of its attached router.
• If the attached router is not configured for split mode, the second DSC sends error messages to
its connected router and indicates its router’s state to the first DSC. The first DSC issues the same
error messages to its router.
• If one attached router is configured in split mode and the other is in normal mode, the router that
is in normal mode stops claiming ownership of any slots and does not respond to boot requests
from any of the dial shelf cards. The router that is in split mode responds to boot requests only
from dial shelf cards in the slots that it owns. However, it does not take over (restart) the dial shelf
cards in its slots until the normal mode router is removed or is also configured in split mode.
Hub Redundancy
In normal mode, both DSCs are connected to the same router shelf. The active DSC monitors the
status of its link to the router shelf and, in the event of link failure, requests the other DSC to take
over. When operating in split mode, each DSC is connected to a different router shelf, so the DSCs
do not send or respond to link failure
messages. If one DSC’s link fails, the other DSC cannot
transparently take over.
TDM Resource Allocation
Trunk cards and modem cards are tied together across a time-division multiplexing (TDM) bus on
the dial shelf backplane. Time slots 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 time
slot (currently 14*128 = 1,792 time slots are used). Time slots 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, time slots are added to the queue dynamically, as they are 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 time slots starting from 0
going up, and the router shelf connected to the DSC in slot 13 allocates time slots starting from 1,791
going down. For split dial shelf operation each router is assigned half of the usable set of time slots.
The router shelf connected to the DSC in slot 12 controls the first half of the time slots (0 to 895).
The router shelf connected to the DSC in slot 13 controls the second half of the time slots (896 to
1791).