Abstract: 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.

Abstract: 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.

Abstract: A network for transferring information among a plurality of digital devices includes a plurality of switching nodes interconnected by communication links. Each of the digital devices is connected to one of the switching nodes over additional ones of communication links. Each communication link transfers information in a predetermined one of a plurality of types of communications services, with the network including at least one communication link of each service type. The digital devices and switching nodes transfer information through the network over virtual circuits, with each virtual circuit extending from one digital device, as an originating digital device, to another digital device, as a terminating digital device. Each virtual circuit defines a unitary virtual circuit path extending through at least one switching node over a plurality of the communication links without regard to the service type of the ones of the communication links included in the virtual circuit path.

Abstract: 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.