Cisco Systems AS5800 manual Dial Shelf OIR Events, Dial Shelf Card Bootup

Cisco 5814 Dial Shelf

Only one common logic is active at any one time, which is identified by the clock (CLK) LED on the DSC’s front panel. The active common logic is user-selectable and is independent from each DSC. This assures that if a DSC needs replacing or if the slave DSC becomes the master, clocking remains stable. The selected common logic should not be changed during normal operation, unless related hardware failure is suspected or diagnosed.

The configuration commands for the master clock specify the various clock sources and a priority for each source. Together these commands define a list, ordered by priority, of the clock sources used to generate the master clock. The prioritized list, configured on the router shelves, is passed to and stored by the DSC providing the active clock. In the event of failure of the highest-priority clock source, the DSC switches to the source with the next highest priority.

With a split dial shelf, the clock sources can be configured on either of the router shelves. Typically a router configures clock sources only from the slots that it owns; clock sources can be configured from other slots, but they are ignored. On the dial shelf, all valid clock source configurations need to be known to the DSC providing the clock, including the clock source configurations on the router connected to the other DSC.

In a typical Cisco AS5800 configuration (without a split dial shelf), clock source configuration lines that specify an external clock are sent directly from the router shelf to both DSCs. In the split dial shelf configuration, a router can send the clock source configuration only to the DSC to which it is connected, not to both DSCs. If an external clock is used in a split dial shelf configuration, it must be configured identically on both router shelves and must be physically connected to both DSCs.

An error condition can arise if a clock input on one router is configured to have the same priority as a clock input configured on the other router. However, the command is not rejected, because the values configured on the other router may not be known. Warning messages are issued to both routers when this condition is detected. Two clock inputs specified with identical priorities both go into the ordered list of clock sources, but the one received first by the DSC providing the active clock is assigned a higher priority.

The show dial-shelf clocks command shows all configured clock sources, even those from non-owned trunk cards. Only one DSC can provide the master clock; however, backup clock sources might need to be configured for all trunk cards present (regardless of which DSC owns them).

Dial Shelf OIR Events

Each DSC needs to know whether it is to operate in split mode or normal mode, and in split mode it needs to know which slots are owned by its connected router. Currently the DSCs receive inventory messages from the router shelves, informing them which cards the routers think are present in the dial shelf. In split mode operation, these messages have been extended to inform the DSC which mode is current and the set of slots it owns.

Split dial shelf configurations are managed by having the slots that are owned by one router appearing to the other router as empty slots. A router shelf is informed of dial shelf OIR events by messages that are sent to the router shelf when a card is inserted in or removed from a slot. In the split dial shelf configuration, once a DSC is informed by the connected router which slots it owns, it sends messages only for dial shelf OIR events that occur in those slots. The hub on each DSC is configured to ignore traffic from cards in non-owned slots.

Dial Shelf Card Bootup

When a dial shelf card starts running, it sends a message to the DSC. The DSC determines whether it is the master for that slot. In the split dial shelf mode, only the DSC whose connected router owns the slot containing the dial shelf card responds to the message. The dial shelf card accepts firmware and a bootstrap image from that DSC and configures itself to communicate through that DSC’s hub.

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