The CRS routing system hardware detects, isolates, and recovers from a broad range of faults, and provides failover mechanisms to redundant hardware. The control plane is a central element in achieving high availability, as it must isolate failures and direct failover events, both in the data plane and in the control plane.
To ease serviceability, the chassis identification displays and the critical, major, and minor alarm indicators are clearly visible. Each line card, RP, and switch fabric card has an alphanumeric display and green OK LED to show current board status. Environmental conditions, including temperature and voltage levels, are monitored by several internal measurement points and reported to the routing system operator.
The RP cards function as the system controller in the chassis. Note that the PLIMs are connected to the control plane through their respective line cards.
The control plane provides switched point-to-point Fast Ethernet (FE) connections between the control processors on various routing system components. This allows for control plane network messages, and some other paths for system communication. The dual RP cards and midplane FE traces provide redundant connections between all cards in the line card chassis. Most cards or modules contain a service processor (SP) module that provides the communication for that device within the control plane.
Some of the important functions and implementations of the control plane are listed in the following sections.