Ascend Communications, Inc.

Sycamore Networks, Inc.

Cascade Communications Corporation

Tao Yang

Chikong Shue

Mahesh N Ganmukhi

Raymond Yinggang Xie

Mohamed Abdelaziz

Naimish Patel

John Thomas Moy

Anthony C K Kam

Wengang Zhai

Ping Wang

Each span of a communication network, such as a BLSR ring, is assigned a unique span ID. When a node of the network detects a failure in a network span, the node exchanges commands, according to an automatic protection switching (APS) protocol, that request other nodes of the network to switch network traffic from a working span to a protect span. The commands specify the working span by its span ID, without necessarily specifying a source node ID or a destination node ID for the commands. The span ID occupies fewer bits in the commands than bits representing a combination of the source node ID and the destination node ID. Alternatively, the commands specify a destination node ID without a span ID or a source node ID, or the commands specify a source node ID without a span ID or a destination node ID.

Network span protection using span identifiers

A system and a method for providing an emulated network including a plurality of emulated networking devices, in which a number of network node executable images are employed. Each of the network node executable images corresponds to one of the emulated networking devices. The emulated networking devices represent physical networking devices, such as optical switches. A portion of each of the network node executable images is operable to execute without modification on a physical networking device. Each of the network node executable images includes a number of program components, such as a topology related program component for maintaining a representation of the topology of the emulated network, a trunk manager program component for maintaining at least one emulated trunk between the corresponding emulated networking device and an adjacent other emulated networking device, and a circuit manager program component operable to maintain at least one emulated circuit between the corresponding emulated networking device and another one of the emulated networking devices. Various numbers of network node executable images may be executed on a single emulator machine, and multiple emulator machines may be employed to execute a single network node executable image.

Network emulator

An explicit rate marking system is disclosed for use in connection with a switching node to generate an explicit rate value for use in a resource management cell associated with a virtual circuit in an ATM network. The explicit rate marking system comprises a virtual bandwidth value generator module and an explicit rate value generator module. The virtual bandwidth value generator module generate a virtual bandwidth value reflecting an available bandwidth capacity value, an explicit rate value associated with each bottlenecked virtual circuit for which the switching node forms part of a path, and a minimum cell rate value associated with each unbottlenecked virtual circuit for which the switching node forms part of a path. The explicit rate value generator module generates the explicit rate value in relation to the virtual bandwidth value and the minimum cell rate value associated with the virtual circuit and other virtual circuits for which the switching node forms part of a path.

System and method for performing explicit rate marking for flow control in ATM networks using a virtual bandwidth-based methodology

A switching node for use in connection with a computer network includes an input interface, a buffer and a control element. The input interface receives cells from at least one input communication link. The buffer buffers selected cells prior to transmission over at least one output communication link. The control element selectively enables cells received by said input interface to be buffered in said buffer. The control element discards cells if the cell occupancy of the buffer exceeds a predetermined threshold level and a credits value indicates that the switching node has loaded a number of cells into the buffer for transmission which exceeds a cell loss ratio guarantee provided by the switching node.

Cell loss balance system and method for digital network

A switching node for use in connection with a computer network includes an input interface, a buffer and a control element. The input interface receives cells from at least one input communication link. The buffer buffers selected cells prior to transmission over at least one output communication link. The control element selectively enables cells received by the input interface to be buffered in the buffer. The control element discards cells if the cell occupancy of the buffer exceeds a predetermined threshold level and a credit value indicates that the switching node has loaded a number of cells into the buffer for transmission which exceeds a cell loss ratio guarantee provided by the switching node.

A packet scheduler is disclosed which provides a high degree of fairness in scheduling packets associated with different sessions. The scheduler also minimizes packet delay for packet transmission from a plurality of sessions which may have different requirements and may operate at different transfer rates. When a packet is received by the scheduler, the packet is assigned its own packet virtual start time based on whether the session has any pending packets and the values of the virtual finish time of the previous packet in the session and the packets arrival time. The scheduler then determines a virtual finish time of the packet by determining the transfer time required for the packet based upon its length and rate and by adding the transfer time to the packet virtual start time of the packet. The packet with the smallest virtual finish time is then scheduled for transfer. By selecting packets for transmission in the above described manner, the available bandwidth may be shared in pro-rata proportion to the guaranteed session rate, thereby providing a scheduler with a high degree of fairness while also minimizing the amount of time a packet waits in the scheduler before being served.

High speed packet scheduling method and apparatus

A method of fairly and efficiently scheduling transmission of a packet from a plurality of sessions onto a network is presented. The method includes providing an input having a plurality of sessions, grouping the sessions into a plurality of classes, scheduling the classes with first level schedulers associated with one of the classes, scheduling the outputs of some of the first level schedulers with a second level scheduler, and prioritizing among the output of the remaining first level scheduler(s) and the output of the second level scheduler to provide an hierarchical scheduler output. The scheduler accepts traffic types at its input, and provides an output suitable for scheduling cell based traffic such as Asynchronous Transfer Mode (ATM) network traffic.

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Acton, MA, United States of America

Tao Yang