At&t Bell Laboratories

Samuel P Morgan

Ellen L Hahne

Charles R Kalmanek

A method for use in a high-speed virtual circuit digital network for resizing windows of virtual circuits in nodes of the network. The resizing of a virtual circuit's window is initiated by an input router at an edge of the digital network. When the input router determines that resizing is necessary, it sends a first congestion control message to the nodes through which the virtual circuit passes. If the message indicates a larger window, the node receiving the message determines what size window it can provide and sends the message with that window size on to the next node. An output router at the other edge of the digital network receives the message, sets the window size based on the message as altered by the nodes, and returns a second message with the final window size via the nodes. On receipt of the second message, the nodes alter their windows and the input router sends cells as permitted by the new window. Included in the method are novel techniques for determining the ideal window size for a virtual circuit, for determining at the input router when a change in window size is necessary, and for determining the size of the window in the nodes.

Dynamic window sizing in a data network

A method of controlling congestion in a virtual circuit packet network. A initial packet buffer is assigned to each virtual circuit at each node into which incoming packets are stored and later removed for forward routing. If a larger buffer is desired for a virtual circuit to service a larger amount of data, then additional buffer space is dynamically allocated selectively to the virtual circuit on demand if each node has sufficient unallocated buffer space to fill the request. In one embodiment, the criterion for dynamic allocation is based on the amount of data buffered at the data source. In alternative embodiments, the criteria for dynamic allocation may be further based on the amount of data buffered at each node for a virtual circuit and the total amount of free buffer space at each node of a virtual circuit. Signaling protocols are disclosed whereby data sources and virtual circuit nodes maintain consistent information describing the buffer allocations at all times.

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Morris Township, NJ, United States of America

Samuel P Morgan