Multiplex communications – Fault recovery
Patent
1997-08-28
2000-02-15
Vu, Huy D.
Multiplex communications
Fault recovery
G01R 3108
Patent
active
060260734
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 step of sending a route-finder signature from a node to a neighbouring node on a spare link of a span to the neighbouring node, and being characterised by the prior steps of:
ranking the links of the span; and
determining on the basis of the respective unique network node identities of the node and the neighbouring node whether the node is in a first or a second ranking relationship with respect to the neighbouring node;
if the node is in said first relationship, sending the route-finder signature to the neighbouring node on the lowest ranking of currently available spare links of said span; or
if the node is in said second relationship, sending the route-finder signature to the neighbouring node on the highest ranking of currently available spare links of said span.
An advantage of the present invention is
REFERENCES:
patent: 4956835 (1990-09-01), Grover
patent: 5435003 (1995-07-01), Chng et al.
patent: 5537532 (1996-07-01), Chng et al.
Bhatnagar et al, "Layer Net: A New Self-Organising Network Protocol", IEEE Military Communications Conference, vol. 2, Sep. 30, 1990, Monterey US, pp. 845-849, XP000221754.
IEEE Military Communications Conference, vol. 2, Sep. 30, 1990, Monterey US, pp. 845-849, XP00221754 Bhatnagar et al.: "Layer Net: A new self-organising network protocol" see section 2.5: `Scheduling of links`.
Brown Graeme Nicholas
Chng Raymond Soo Khiaw
Boakye Alexander
British Telecommunications public limited company
Vu Huy D.
LandOfFree
Route finding in communications networks does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Route finding in communications networks, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Route finding in communications networks will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1911517