Nortel Networks Corporation

Kenneth Gary Hayward

Todd D Morris

Li Li

Stephen Daniel Shew

Donald Russell Ellis

Loa Andersson

John Philip Brule

Jon Weil

Alex Morrall

Michael C To

David Odhams

Donald R Ellis

John P Brule

A communications network comprises a lower transport layer and an upper overlay incorporating a plurality of routers. Adjacencies are defined between respective pairs of routers. Path protection is provided by defining a software model of the overlay of the network and defining in the model a hierarchy of protection levels for the main path. Each protection level is characterised by a respective set of one or more broken adjacencies in the model, the adjacencies to be broken being determined from a knowledge of the underlying topology. A protection level is selected and a protection path avoiding the broken adjacencies associated with that protection level is calculated. If this calculated path is not available in the real network, a lower protection level in the hierarchy is selected and the protection path calculation repeated. The process continues until a suitable protection path is identified.

Route protection in a communication network

A method of address resolution for the transfer of voice and voice data calls through multiple domains in a broadband data network is described. The implementation of broadband data networks as transport backbones for voice and voice data calls requires address resolution to determine the destination node for each call. Because of the projected frequency at which new access peripherals will be added to such broadband data networks, manual maintenance of translation tables is impractical. The invention therefore provides an automated method for address resolution which permits voice interface control units associated with the broadband data network nodes to automatically maintain the required translation tables. Next-hop resolution routing tables may be maintained at every node or only at nodes designated as signaling gateways between broadband data network domains. If the broadband data network is an ATM network, switched virtual circuits are set up in reverse from ATM destination nodes in order to reduce call admission and setup time. The advantage is automated maintenance of translation tables which may be tailored to meet the operating policy of network managers that control respective domains.

Method of address resolution for the transfer of synchronous transfer mode calls through multiple domains in a broadband data network

The present invention provides layer one, two and three (L /L /L ) Integration and L cut-through path utilization in an apparatus and method of fault recovery. A switch combines an IP router with L capabilities, and an L cross connect (optical or electrical). A network of such switches is configured with label switched paths (LSP) that correspond to layer (L ) cut-through paths. The layer (L ) cut-through path is over laid on the L cut-through path and the L cut-through path is used for IP data flows. Preferably, the L cut-through paths are defined as label switched paths (LSP) and the L cut-through paths are each an end-to-end path established with L cross connects associated with each switch.

Network fault recovery method and apparatus

A method and apparatus for pre-establishing and managing Switched Virtual Circuits (SVCs) and Switch Cross-Connects (XCs) to support rapid setup of real-time services in Asynchronous Transfer Mode (ATM) networks are described. SVCs and XCs are pre-established and cached in accordance with communications application-specific rules and maintenance algorithms for each destination and service characteristics in the backbone network. The intelligent management of cached SVCs and XCs permits the backbone network to meet the tight delay budget of delay-sensitive communication applications. With proper management of cached resources, connection setup can be rapidly effected even during periods of high demand. The advantage is a connection setup mechanism having adequate granularity to ensure both efficient network usage and rapid response to service requests.

Method and apparatus for caching switched virtual circuits in an ATM network

A method and apparatus for routing data packets via a synchronous optical (SONET) network from devices connected to a local area network to devices connected to other local area networks. At each transport node in the SONET network the data packets are unloaded from SONET payloads and requeued for transmission on an output path. This allows for easy resolution of contention between devices transmitting at the same time and avoids pre-assigning SONET channels. Source and destination address information from the data packets can be used to route the data packets through the SONET network. A time-to-live indicator can be used to find the shortest path to a destination address in a SONET ring network or any bidirectional ring network.

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Kanata, Canada

Kenneth Gary Hayward