Nortel Networks Corporation

Shantigram V Jagannath

Nanying Yin

Richard L Angle

Geoffrey B Ladwig

Naganand Doraswamy

Andre N Fredette

Jim Luciani

A method and apparatus are provided for scheduling unicast and multicast data in an input-queued network device. According to one aspect of the present invention, a combined schedule is created by pipelined staging of multicast and unicast scheduling. Multicast cells are scheduled for transmission among multiple interfaces of a crossbar by performing a multicast cell scheduling cycle for multiple classes of service that are supported by the network device. Then, unicast cells are scheduled for transmission among the interfaces at a lower priority than the previously scheduled multicast cells by performing a unicast cell scheduling cycle for the multiple classes of service using only those interfaces that remain unmatched after completion of the multicast cell scheduling cycle.

Multicast and unicast scheduling for a network device

A method and apparatus for directing messages through a network wherein multiple tables for directing messages through the network are maintained and provided. Each table corresponds to a virtual private network and contains routing information specific to that virtual private network. A separate routing table is maintained for each VPN. In one embodiment the messages are forwarded using plain IP forwarding using a route table associated with the VPN. In another embodiment separate forwarding tables using labels are generated for each virtual private network. The messages are forwarded by looking up the label in the table corresponding to the VPN In a third embodiment, a single forwarding table is utilized where the table is built based on separate routing tables for each virtual private network.

Method and apparatus for virtual overlay networks

A method and apparatus are provided for scheduling multicast data in an input-queued network device. A fabric arbiter receives a transmit request associated with multiple input ports. The transmit request identifies those of the output ports to which pending multicast cells are ready to be transmitted, if any. The fabric arbiter receives a backpressure signal from a backpressuring output port. Then, based upon the backpressure signal the fabric arbiter schedules multicast cells for transmission across the fabric. If the size of a multicast queue exceeds a predetermined threshold, then the fabric arbiter ignores the backpressure signal and causes the head-of-line multicast cell from the multicast queue to be transferred to the backpressuring output port. Otherwise, the fabric arbiter prevents multicast cells from being transferred to the backpressuring output port by masking requests destined for the backpressuring output port thereby removing the backpressuring output port from consideration during multicast scheduling.

Backpressure mechanism for a network device

A method and apparatus are provided for scheduling multicast data in an input-queued network device. According to one aspect of the present invention, deterministic and bounded delay for high priority multicast cells is guaranteed by the multicast scheduler. The scheduler receives a transmit request associated with each of a plurality of input ports. The transmit request identifies output ports to which pending multicast cells are ready to be transmitted, if any. Then, for each of multiple classes of service, the scheduler performs a single scheduling iteration. The single scheduling iteration includes a grant phase, an accept phase, and an update phase. During the grant phase, the scheduler grants one or more of the input ports access to the fabric by issuing grants based upon the transmit requests and a priority indicator that identifies an input port that is given scheduling priority for the scheduling iteration. During the accept phase, on behalf of each of the input ports, the scheduler accepts all grants corresponding to the input port. Finally, during the update phase, the scheduler updates the priority indicator for use in a subsequent scheduling cycle.

Multicast scheduling for a network device

A method and apparatus are provided for scheduling unicast and multicast data in an input-queued network device. According to one aspect of the present invention, multicast scheduling is triggered by a programmable parameter. Each scheduling timeslot of a set of possible scheduling timeslots, unicast cell scheduling is performed. Multicast cell scheduling is performed in parallel with and independent of the unicast cell scheduling during scheduling timeslots in which a programmable multicast scheduling frequency parameter satisfies a predetermined condition.

Programmable multicast scheduling for a network device

A method and apparatus are provided for scheduling multicast data in an input-queued network device. According to one aspect of the present invention, the head-of-line blocking problem is avoided for multicast queues. A fabric arbiter receives a transmit request associated with multiple input ports. The transmit request identifies those of the output ports to which pending multicast cells are ready to be transmitted, if any. The fabric arbiter receives a backpressure signal from a backpressuring output port. Then, based upon the backpressure signal the fabric arbiter schedules multicast cells for transmission across the fabric. If the size of a multicast queue exceeds a predetermined threshold, then the fabric arbiter ignores the backpressure signal and causes the head-of-line multicast cell from the multicast queue to be transferred to the backpressuring output port. Otherwise, the fabric arbiter prevents multicast cells from being transferred to the backpressuring output port by masking requests destined for the backpressuring output port thereby removing the backpressuring output port from consideration during multicast scheduling.

A method and apparatus for communicating congestion control information between dissimilar protocols operating in heterogeneous internetworks at different layers of the International Standards Organization (ISO) Open Systems Interconnection (OSI) 7 layer conceptual model for data networking. The method and apparatus provides direct end-to-end congestion control at the Transport layer across a TCP/IP and ATM internetwork utilizing ATM ABR and TCP sliding window flow control mechanisms. A network device that interconnects TCP/IP and ATM data networks for communication of data communicates network congestion detected by a protocol operating in the ATM data network to a heterogeneous protocol operating in the TCP/IP data network. The network device receives TCP data packets and stores them in a queue. A TCP packet is discarded if the queue is full or network congestion is detected by the protocol operating in the ATM network, to communicate network congestion in the ATM network to the heterogeneous protocol operating in the TCP/IP network.

Method and apparatus for communicating congestion information among different protocol layers between networks

A method for distributing label binding information, e.g., a binding between a label and a network layer route, in a label switching environment using the Open Shortest Path First (OSPF) Opaque Link State Advertisement (LSA) option protocol. The binding information is included in an application specific field following the LSA header. LS type 9 LSA packets are used to limit the flooding scope to the local network segments attached to the label switch. Address prefix information, i.e., network address and subnet mask, are transmitted and associated with a label in the application specific field of the Opaque LSA packet. The Opaque LSA packets are exchanged between a group of interconnected Opaque LSA capable label switches so that the label switches can maintain their label forwarding tables and routing tables as necessary to forward data packets according to a label swapping forwarding paradigm.

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Cambridge, MA, United States of America

Shantigram V Jagannath