Abstract: A redundant control plane for a network device such as a network switch or a router. The control plane is isolated from a data plane for the network device that carries network traffic. The redundant control plane includes first and second Router Control Processor (RCP)/Bridge Hotswap Card (BHC) pairs, and first and second switch cards (SCs). A first RCP/BHC pair is selected as the master and the second pair becomes the master in the event of a failure or the need to perform maintenance on the first pair. Redundant control paths are provided from each RCP/BHC pair to first and second pluralities of line cards to allow for downloading of forwarding tables, control and configuration information. Redundant Switch cards are provided and one of the Switch Cards is selected as the master Switch card to permit communication between the RCPs. The control plane may continue to function in the event of a single failure of any component or bus within the control plane.

Abstract: A system and method for configuring a control plane within a network device. One of a pair of control processors is selected to act as the master of the control plane and the other control processor is specified as a standby control processor in normal operation. In the case of a failover or switchover event, the standby control processor assumes the role of the master of the control plane and updates configuration information within line cards in the network device as necessary. A state machine within the control processor is employed to manage state transitions for the control processor. Each control processor generates at least one signal that indicates whether it is capable of serving as the master of the control plane. Master selection logic selects one of the control processors as the master for the control plane and in one embodiment advertises the identification of the master control processor via triply redundant signals.

Abstract: Congestion management is provided using one or more receive queues organized into a queue list. Each queue is associated with a high water mark and a low water mark. The high water mark indicates a length at which the queue is considered congested. The low water mark is a length at which a congested queue is considered no longer congested. When a queue reaches or exceeds its high water mark, newly arriving frames destined for that queue which are eligible for discard are dropped. Frames arriving not marked as eligible for discard are enqueued at the queue's tail. Queues in the queue list are organized by relative priority. When a single queue above a predetermined priority is determined to be congested, all queues in the queue list are treated as congested. Congestion in lower priority queues results in only the individual congested queue being treated as congested.

Abstract: A redundant control plane for a network device such as a network switch or a router. The control plane is isolated from a data plane for the network device that carries network traffic. The redundant control plane includes first and second Router Control Processor (RCP)/Bridge Hotswap Card (BHC) pairs, and first and second switch cards (SCs). A first RCP/BHC pair is selected as the master and the second pair becomes the master in the event of a failure or the need to perform maintenance on the first pair. Redundant control paths are provided from each RCP/BHC pair to first and second pluralities of line cards to allow for downloading of forwarding tables, control and configuration information. Redundant Switch cards are provided and one of the Switch Cards is selected as the master Switch card to permit communication between the RCPs. The control plane may continue to function in the event of a single failure of any component or bus within the control plane.

Abstract: A system and method for configuring a control plane within a network device. One of a pair of control processors is selected to act as the master of the control plane and the other control processor is specified as a standby control processor in normal operation. In the case of a failover or switchover event, the standby control processor assumes the role of the master of the control plane and updates configuration information within line cards in the network device as necessary. A state machine within the control processor is employed to manage state transitions for the control processor. Each control processor generates at least one signal that indicates whether it is capable of serving as the master of the control plane. Master selection logic selects one of the control processors as the master for the control plane and in one embodiment advertises the identification of the master control processor via triply redundant signals.

Abstract: A system for temporarily storing and dequeuing received data units including searching a prioritized queue list for a highest priority queue having a head entry associated with a received data unit which is part of the guaranteed bandwidth of the connection on which it was received, and for which there are sufficient transmission credits available, based on a flow control mode associated with the data unit. If no such guaranteed bandwidth data unit is found, the system dequeues a highest priority queue having a head entry associated with an available bandwidth data unit, for which there are sufficient transmission credits available to begin transmission based on a flow control mode associated with the data unit. If no such available bandwidth data unit is found, then no data unit is dequeued during that traversal of the queue list.

Abstract: A system and method for performing event-based rate policing using varying window start times. Rate policing overhead, including counter and timer monitoring and resetting, is performed only as needed and in response to actual received traffic on each connection. As the last bit of a data unit is received from an external network, an “event time stamp” is generated and associated with the data unit, for example as part of an internal header or trailer attached to the data unit. To determine if a rate policing window was active when the frame was received, the event time stamp is compared with a sum of a window start time and a window period value stored in association with the connection on which the data unit was received. If the associated event time stamp indicates a time prior to the sum of the associated window start time and window period, then a rate policing window is determined to have been active when the frame was received.

Abstract: A system and method for providing QoS levels to received data units, such as ATM cells and/or Frame Relay Frames. A QoS level associated with a virtual connection is supported through allocation and management of resources used to process data units received over the connection. Resources used to support QoS levels are assigned to groups of connections referred to as “QoS groups”. Resources used to support one group of connections may be isolated from resources supporting other connections. When a connection is established, if a QoS group exists having the QoS level of the new connection, the connection may be added to that QoS group. Similarly, where the QoS levels for multiple connections must be modified, if those connections are within a single QoS group, then modification of the QoS level for that group would advantageously result in modification of the QoS for each virtual connection within the QoS group.