International Business Machines Corporation

Cisco Technology, Inc.

Olivier Bertin

Claude R Galand

Olivier Maurel

Laurent Nicolas

Jean-Paul Chobert

Eric Michel Levy-Abegnoli

Aline Fichou

Denis Chevalier

Marcel Villaflor

Yves Ouvry

Gerard Brun

Alain Pruvost

Maurice Duault

Denis Jean Albert Chevalier

Philippe Michel Bazot

A method for operating a node in a computer network is disclosed, where the network is made up of nodes connected by links. The method has the steps: determining an alternate path for one or more links; reserving resources for the alternate path; and rerouting traffic on the alternate path in case of a link failure. The alternate path may be periodically updated. A plurality of alternate paths may be maintained. The alternate paths may not have any links in common. User traffic may be rerouted substantially simultaneously to each link of the alternate path in the event of failure of a primary path.

Method and system for a local and fast non-disruptive path switching in high speed packet switching networks

The present invention is directed to a high speed packet switching network and, in particular to a method and system for minimizing the time to establish a connection between an origin and a destination node. Due to high dynamicity of the traffic on transmission links, it is important to select a routing path according to a fully up-to-date information on all network resources. The simpler approach is to calculate a new path for each new connection request. This solution may be very time consuming because there are as many path selection operations as connection set up operations. On another hand, the calculation of paths based on an exhaustive exploration of the network topology, is a complex operation which may also take an inordinate amount of resources in large networks. Many of connections originated from a network node flow to the same destination network node. It is therefore possible to take a serious benefit in reusing the same already calculated paths for several connections towards the same node. The path calculated at the time the connection is requested is recorded in a Routing Database and updated each time a modification occurs in the network. Furthermore, alternate paths for supporting non-disruptive path switch on failure or preemption, and new paths towards potential destination nodes can be calculated and stored when the connection set up process is idle. These last operations are executed in background with a low processing priority and in absence of connection request.

Method and system for minimizing the connection set up time in high speed packet switching networks

The present invention is directed to a high speed packet switching network and, in particular to a method and system for minimizing the time to establish a connection between an origin and a destination node. A path calculated at the time the connection is requested is recorded in a Routing Database and updated each time a modification occurs in the network. Furthermore, alternate paths for supporting non-disruptive path switch on failure or preemption, and new paths towards potential destination nodes can be calculated and stored when the connection set up process is idle. These last operations are executed in background with a low processing priority and in absence of connection request.

Method and system for non disruptively assigning link bandwidth to a user in a high speed digital network

In a high speed digital network including access nodes and network nodes each having topology data bases, a method for optimizing the connection set-up operations required for connecting a calling end-user attached to a local access node to a destination user attached to a remote access node, via a conventional connection set-up operation. An Access Node Connection Table (ANCT) in each access node stores a list of every remote access node for which the local access node has at least one user connection. A field in the locate reply message is defined for the destination remote Access Node Topology Database (ANTDB) and remote ANTDB information is inserted prior to sending the reply message. Locate reply message reception is monitored by the local access node, and upon reception an entry is created for the received remote ANTDB information in the local access node unless the remote access node was already identified in the local access node. An optimal path is then selected and connection set up. The ANCT is then updated accordingly.

Method and system for optimizing connection set-up operations in a high speed digital network

An apparatus and method that determines the end-to-end transit delay at each node of a path, in accordance with the selected probability value indicative of the probability to experience a delay at each node that is smaller than the computed transit delay. Then the computed transit delays per nodes are combined to obtain the end-to-end delay of the path, the combination being either an arithmetic operation or a convolution operation. A method to approximate the convolution operation is also disclosed.

End-to-end delay estimation in high speed communication networks

A method and system for reserving dynamically and in priority for each link of the network the exact amount of bandwidth necessary for the transmission of the network control traffic. An evaluation of the expected control traffic on each link of the network is performed in order to allocate a sufficient but minimum fraction of the link bandwidth and for allocating the maximum available bandwidth for the user traffic.

Dynamic bandwidth reservation for control traffic in high speed packet

The present invention is related to high speed packet switching networks and, more particularly, to a process for selecting an optimal path for packets transmission without bandwidth reservation in communication systems supporting both bandwidth-reserved and non-bandwidth-reserved connections. Non-reserved network connections do not have bandwidth set aside either implicitly or explicitly. The lowest delay priority is assigned to non-reserved traffic and the networks drops non-reserved packets when their buffer overflow at intermediate links. Because the data profile over the connections is bursty and non deterministic, reserved traffic does not lead to a full links utilization except on peaks. Therefore, non-reserved traffic can be transmitted when some bandwidth is available on the links. The purpose of an efficient bandwidth management is to reserve on the links as many bandwidth as possible with a guaranteed quality of service, and to use the inherent remaining bandwidth to transport traffic from the users who are just expecting a 'best effort' service. The Path Selection algorithm for non-reserved connections comprises the step of weighing each transmission link with a weighing function dependent of both reserved non-reserved traffic.

Method and system for selecting path according to reserved and not

A method based on predefined connection priorities for assigning link bandwidth to a requesting user in a high speed digital network interconnecting network users through a path including network nodes connected through high speed links. According to this method, a predefined reservable link bandwidth is split into so-called nominal bandwidth portions and common bandwidth portions, both assignable to the same connections on a priority basis. Each of the common bandwidth priorities is individually related to a nominal bandwidth priority through a predefined relationship, making the common bandwidth priorities always lower than any nominal priority. In this way the requested link connection bandwidth, whatever be its nominal priority, is made preemptable primarily on all common bandwidth, thus avoiding the disruption of any network connection which is already established.

Method and system for non-disruptively assigning link bandwidth to a

High speed network nodes can establish new connections by preempting existing ones when insufficient bandwidth is available in the network. Numerous preemption priorities are arranged in a limited number of groups and a median priority level is defined within each group. This median, stored in the topology database of each node of the network, permits better bandwidth utilization per group while consuming very little memory space and generating very low traffic overhead.

Method for preempting connections in high speed packet switching networks

A topology manager within a data communication network including a number of nodes interconnected by bi-directional links, wherein each said node is provided with means for dynamically setting and storing within the node a full topology database including full parent-node-relationship references. The system is is capable of fast path determination and fast spanning tree recovery based on the topology database contents.

System for managing topology of a network in spanning tree data

The routing paths between origin and destination nodes in a packet switching network are selected more efficiently by reducing the total number of links potentially visited by the routing algorithm. The path selection technique involves two phases, the first phase for principal links identification, and the second phase for selection of the best point-to-point path in the network. Principal paths are minimum hop count paths with a transmission delay less than a specified threshold. The algorithm limits the screening of the network links in the second phase to the principal links and excludes the secondary links. The exploration of a much smaller number of links has the advantage to considerably reduce the computation time required for the path selection. The fact the number of principal links is generally small compared with the total number of links potentially explored, allows to limit the additional processing time necessary in case of unsuccessful attempt.

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Nice, France

Olivier Bertin