Nortel Networks Corporation

Cheng Yin Lee

Nabil Seddigh

Loa Andersson

Distributed traffic engineering route exchanger routers (TE-Xs) are used in an open shortest path first (OSPF) routing area to collect Traffic Engineering Link State Advertisements (TE-LSAs) and exchange the TE-LSAs with other TE-Xs. TE-Xs store TE-LSAs and compute explicit routes required by edge routers. A single point of failure that exists when a single centralized TE database is used is thereby eliminated. The TE-Xs peer with other TE-Xs in a routing area and exchange TE-LSAs to keep traffic engineering link state databases (TE-LSDBs) synchronized. Network resources are preserved for payload traffic and resource reservation collisions are reduced.

Constraint route dissemination using distributed route exchanges

A method for detecting a routing loop when repairing a bidirectional multicast distribution tree is disclosed. According to the method, a splice message is launched from an originating node attempting to join a bidirectional multicast tree and is sent to a root-node to find out if a routing loop is formed when a node is joining the multicast distribution tree. Depending on the multicast application requirement, when a routing loop is detected during the repairing of a multicast distribution tree, the severed node may abort, or the repair can be deferred until the connection to the root-node is re-established. The loop detection and loop prevention method of the invention may be used as a loop avoidance mechanism with any protocol for repairing a partitioned tree.

Mechanism for splicing trees

A method as apparatus for controlling the number of egress points at an ingress node in a multicast tree in a differentiated services network is described. A resource management entity is provided in each edge node in the entity. The resource management entity in the ingress node stores data from a service level specification that specifies the bandwidth, type of service and a limit on the number of egress points that can be grafted to the ingress node. The grafting of egress points to the node is controlled by the limit. If a new egress point cannot be grafted to the ingress node, the downstream node requesting the graft is preferably provided with graft redirect options to permit the downstream node to graft to an existing branch of the multicast tree. The advantage is automated, dynamic control of the multicast tree so that service is delivered in accordance with a service level agreement that governs service delivery for the dynamic multicast tree.

Method and apparatus for controlling fanout of a multicast tree

A method to engineer paths for multicast traffic in an IP network, by directing the control messages to setup multicast trees on engineered paths, is disclosed. The multicast traffic engineering process is separated from the multicast route setup and the resources and the paths for multicast data delivery can be aggregated and independently allocated. Resources are allocated on the same trip when paths are selected and setup, and this prevents data from being forwarded on branches where resources have not been yet allocated. The traffic can be statistically multiplexed enabling the network operators to have control over the topology of the multicast trees and to provide differentiated services in a scalable manner.

Method for engineering paths for multicast traffic

A system for provisioning a dynamic multicast group over a differentiated services (DS) network includes an a plurality of edge nodes, each of which includes a respective multicast traffic engineering entity. An ingress node is adapted to serve as a source of data traffic of the dynamic multicast group. An egress node is adapted to serve as a sink of the data traffic of the dynamic multicast group. The multicast traffic engineering entity of the egress node is adapted for receiving information respecting a predetermined service level specification (SLS) of the dynamic multicast group; and provisioning a distribution path from the egress node back to the ingress node, on the basis of the received information respecting the SLS. In a method of the invention, information respecting a predetermined service level specification (SLS) of the dynamic multicast group is received at the egress node; and the distribution path is provisioned from the egress node back to the ingress node, on the basis of the received information respecting the SLS. The advantage is reliable automated provisioning of dynamic multicast trees in differentiated service networks.

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Ottawa, Canada

Cheng Yin Lee