Route finding in communication networks

Details Route finding in communication networks Route finding in communication networks

1998-02-05

2000-09-19

Pham, Chi H.

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

370410, H04L 1228

Patent

active

061222828

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to a method of finding, or determining, a route in a communication network; to a node arranged to perform the method; and to a network comprising such nodes. A route may be needed to replace an existing route which has failed, and such a route is referred to as a restoration route, or a route may be required to supplement an existing route which is becoming congested. As used herein, the term "additional route" embraces both restoration routes and supplementary routes.
2. Description of Related Art
It is known, for example from the article "The Self-Healing Network: A Fast Distributed Restoration Technique For Networks Using Digital Cross-Connect Machines", W. D. Grover, IEEE Globecom 87, and from U.S. Pat. No. 4,956,835 (Wayne D. Grover) to respond at the two nodes (known as failure nodes) connected to a failed span to receipt of a span failure alarm to initiate a real-time restoration process.
The failure nodes determine on the basis of their unique network identities (IDs) which node acts as Sender and which node acts as Chooser (also known as Master and Slave, respectively).
For each of the links of the failed span the Sender repeatedly transmits (floods) respective route-finder signatures to its neighbouring nodes (known as Tandem nodes) which forward flood the signatures to their neighbouring nodes. In one embodiment in the abovementioned U.S. patent a node knows only its own identity (ID) and learns the ID of the node to which connectivity has been lost by reading the last valid contents of a receive signature register on the affected port(s) corresponding to the failed link(s), and in an alternative embodiment, a node stores and maintains a neighbour node ID table.
The node which decides to act as Chooser now enters a waiting state and remains in it until it receives a route-finder signature. Then it responds by transmitting a respective complementary reverse-linking signature (also known as a confirmation or return signature) to the Tandem node from which the route-finder signature was received. The confirmation signature travels back through the Tandem nodes establishing the required switch connections between node input and output ports, and eventually arrives at the Sender node, which then ceases transmitting the respective route-finder signatures, and proceeds to transmit on that newly established restoration route the traffic which would have been transmitted on the corresponding link of the failed span.
The abovementioned U.S. patent also discloses that the restoration mechanism can be used for automatic provisioning of new circuit routes in a network by placing two nodes, between which it is desired to provision additional (i.e. supplementary) circuit routes, directly into Sender and Chooser states with regard to an artificial fault between the selected nodes. The nodes would be supplied with artificial fault information including the number of circuit routings that are being sought.


SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a method of determining an additional route in a fully or partly meshed communications network of nodes, the method comprising the steps of: accordance with a respective predetermined master/slave relationship, at each of a pair of the nodes between which there is an existing route, the one node of said pair which is to act as master end node with respect to said existing route and the other node which is to act as slave end node; signature for said existing route and including a first field containing identification data for said existing route; the contents of said first field whether such receiving node is the slave end node for said existing route and, in the event that it is not, forwarding such received forward route-finder signature to its neighbouring nodes; circumstance a potential additional route and sending from said other node on said potential additional route a route confirmation signature identifying said potential addit

REFERENCES:
patent: 4956835 (1990-09-01), Grover
patent: 5065399 (1991-11-01), Hasegawa et al.
patent: 5146452 (1992-09-01), Pakarske
patent: 5435003 (1995-07-01), Chng et al.
patent: 5537532 (1996-07-01), Chng et al.
patent: 6026073 (2000-02-01), Brown et al.

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