Nortel Networks Corporation

David Charles Steele

Peter William Phelps

Evert De Boer

Robert Caporuscio

Louis Rene Pare

Louis-Rene Pare

Stephen Wilson

Evert E deBoer

Nicola Benvenuti

Dino B Fatica

Nicolas Benvenuti

LeRoy L Pick

Jeff J Towers

Andrew King

Protection transmission unit allocation, such as STS# in a SONET/SDH network utilizing time slot interchange on the working path, may be determined by disseminating connection information, connection identification information, and a prioritization scheme, to nodes on the network and allowing them to deterministically allocate protection transmission units to connections on the protection cycle. Network elements forming physical or logical rings may thus ascertain the location on protection for a given connection without requiring protection unit allocation to be disseminated from a central controller. Since each node is starting with the same connection information and running the same priority determination, each will end up with the same result and will know where to place and find connections on protection. Aspects of the invention may be employed for example in a SONET/SDH based network, a mesh network, or other type of network with dedicated protection paths and transmission allocation on those protection paths.

Method and apparatus for determining protection transmission unit allocation

A network control entity that has an input for receiving data indicative of an event associated with a first member of a virtual concatenation group transported through the network. The network control entity also has a processing entity for computing a new route for a second member of the virtual concatenation group, the computing being triggered by the event.

Method and apparatus for routing a virtual concatenation group in a network

A switch fabric for switching data traffic according to a plurality of links. The data traffic may convey audio information, video information, or any other type of information. The switch fabric includes input, output and at least one intermediate stages, each stage including a plurality of switching elements. The switching elements of the input and output stages respectively have external input and output ports. The switch fabric further includes a switch fabric controller. The switch fabric controller includes a link database including information about the plurality of links. The switch fabric controller is operative to search the link database to identify symmetrical links and to establish internal pathways between the input stage and the output stage through the at least one intermediate stage, wherein at least two symmetrical links identified by the searching are realized using a common switching element of the at least one intermediate stage.

Technique for computing pathways in a multi-stage switch fabric through exploitation of symmetrical links

A method and corresponding network element configuration for delivering communications services between first and second survivable rings, each comprising a respective plurality of network elements, at least two of which are common to both rings. For each particular service, one of the common network elements is designated as a primary gateway node and another as a secondary gateway node. A primary inter-ring connection is established for the particular service by a switch at the primary gateway node, but no inter-ring connection is established at the secondary gateway node. The secondary gateway node comprises a controller for monitoring the status of the primary gateway node and establishing a new inter-ring connection for delivery of the service upon detecting a failure of the primary gateway node. This provides survivable inter-ring traffic which is bandwidth-efficient and with a low switching delay.

Method and apparatus for ensuring survivability of inter-ring traffic

Methods, apparatuses, media and signals for providing clear channel access on a network are disclosed. A first method involves receiving a communication signal from a remote network element. The communication signal includes a previous transport overhead (PTOH) portion indicative of transport overhead contents of the communication signal prior to arrival at the remote network element, and a previous path error (PPE) portion indicative of path errors present in the communication signal at the remote network element. The method then involves modifying a transport overhead portion of the communication signal in response to the PTOH and PPE portions. A second method involves inserting into a communication signal received at a network element, a previous transport overhead (PTOH) portion indicative of transport overhead contents of the communication signal prior to arrival at the network element, and a previous path error (PPE) portion indicative of path errors present in the communication signal at the network element. The second method then involves transmitting the communication signal to a remote device.

Clear channel access methods, apparatuses, media and signals

A method and corresponding network element configuration for delivering communications services between first and second survivable rings, each comprising a respective plurality of network elements, at least two of which are common to both rings. For each particular service, one of the common network elements is designated as a primary gateway node and another as a secondary gateway node. A primary inter-ring connection is established for the particular service by a switch at the primary gateway node, but no inter-ring connection is established at the secondary gateway node. The secondary gateway node comprises a controller for monitoring the status of the primary gateway node and establishing a new inter-ring connection for delivery of said service upon detecting a failure of the primary gateway node. This provides survivable inter-ring traffic which is bandwidth-efficient and with a low switching delay.

The matched nodes provide protection for a failure in the connection between two bidirectional line switched rings. They use a secondary path in case of a primary path failure. The secondary path is set aside in either the working or protection bandwidth of the rings, thus wasting resources. The invention uses a dedicated secondary path between the primary and secondary nodes. With the invention, no ring protection mechanisms are compromised and the ring bandwidth is not wasted. Middle nodes also realize full add/drop capabilities.

Optical ring protection having matched nodes and alternate secondary path

The matched nodes provide protection for a failure in the connection between two bidirectional line switched rings. They use a secondary path in case of a primary path failure. The secondary path is set aside in either the working or protection bandwidth of the rings, thus wasting resources. The invention uses inter-ring protection mechanisms which do away with a specifically set aside secondary path between the primary and secondary nodes.

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Kanata, Canada

David Charles Steele