Multiplex communications – Fault recovery
Reexamination Certificate
1998-08-06
2001-11-20
Hsu, Alpus H. (Department: 2662)
Multiplex communications
Fault recovery
C370S248000, C370S254000, C714S002000
Reexamination Certificate
active
06320844
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a distributed restoration method for link- or node-failure within a communication network, and a related system.
2. Discussion of Related Art
Such a distributed restoration method and related system are already known in the art, e.g. from the article “Double Search Self-Healing Algorithm and its Characteristics ” from the authors H. Fujii and N. Yoshikai from NTT Telecommunications Network Laboratories. This article is published in “
Electronics and Communications in Japan
”, Part 1, Volume 77, No. 3, 1994, Page 75-86. The article is translated from
Denahi Joho Taushin Gakkai Ronbunschi
, Vol. 76-B-1, No. 7, July 1993, pp.485-495.
Therein, a communication network is described consisting of a plurality of Network Elements, called nodes, interconnected by Network links, called links. Along these Network links a communication-path, or a path in the article, is set up between each couple of communicating nodes. If a failure occurs, on such a communication path, a system for distributed restoration will recover this communication-path.
During introduction of a distributed restoration system in an entire communications-network comprising a number of Network Elements, no distributed restoration for the complete communications-network can be provided because the introduction of such a distributed restoration system will in general not take place at once but only in a gradual way, Network Element by Network Element. Moreover in communication-networks that are built up of different kinds of Network Elements, e.g. in multivendor or multi-operator environments, distributed restoration may not be supported throughout the entire network since the different Elements may not be compatible.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and a system for restoration of the above known type but wherein capabilities for restoration at any time, i.e. even during the introduction-phase of the distributed restoration system, are available throughout the entire network, even if this network comprises different kinds of Elements (multivendor network).
According to a first aspect of the invention, a method for distributed restoration of a communication-path in a communications network comprising a plurality of Network Elements and a Network Management module, all interconnected, said method being used in case of Network Link or Network Element failure along said communication-path, is characterized in that said method comprises the steps of:
a. determination of a degree of availability of distributed link or node failure restoration capabilities within said communications network by a Network Element among said Network Elements involved in said restoration; and either one of the following steps:
b1. deciding to restore said failure by means of a distributed restoration system if said degree exceeds a predefined level; or
b2. deciding to restore said failure in co-operation with a restoration system within the Network Management module if said degree does not exceed said predefined level.
According to a second aspect of the invention, a system used for restoration of a communication path in a communications network comprising a plurality of Network Elements and a Network Management module, all interconnected, said system being used in case of Network Element failure or Network Link failure along said communication path, is characterized in that said system comprises:
a. a plurality of determination- and decision-means, each one of which is included in a respective one of said plurality of Network Elements, and is adapted to determine a degree of availability of distributed link or node failure restoration capabilities within said communications network and to decide to restore said failure in a distributed way if said degree exceeds a predefined level or to restore said failure in co-operation with said Network Management if said degree does not exceed said predefined level,
b1. a plurality of first restoration means, each one of which is comprised in a respective one of said Network Elements and is coupled to a respective one of said plurality of determination- and decision-means, and is adapted to restore said failure under control of said respective determination- and decision-means, coupled to each one of said determination- and decision-means, and adapted to restore said failure under control of said respective determination- and decision-means.
According to a third aspect of the invention, a Network Element is characterized according to a second aspect of the invention.
Indeed, by determination of the degree of availability of distributed link or node restoration facilities within the network, for instance a Boolean variable: i.e. a Network Element does possess said distributed restoration facilities or does not possess said distributed restoration facilities, data appropriate for decision-making is derived. Considering these data, a decision can be made whether restoration in co-operation with the restoration module RM′ within the Network Management module NM should be applied, instead of restoration applied by the involved Network Elements. In this co-operation, the occurring link or Network errors can be restored also in case insufficient Network Elements do possess distributed restoration facilities, because this restoration module RM′ within Network Management is not sensitive thereto. This is for example valid during introduction of distributed restoration facilities in a Telecommunications Network or in a multivendor network.
Indeed, the mentioned degree of availability can be determined in a number of different ways: for instance, by determining if a Network Element does possess said distributed restoration facilities or does not possess said distributed restoration facilities, or for example by calculating the percentage of neighboring Network Elements possessing distributed restoration facilities. These are preferable degrees of availability because of their simplicity.
An additional feature of the present system is that the second restoration module, according to the second aspect of the invention, is adapted to implement distributed restoration facilities.
The restoration module in the Network Management NM possesses the same distributed facilities as the restoration modules in the Network Elements. For each Network Element that does not possess a restoration module, an instance of the distributed restoration module is provided in this Network Management. This instance of the restoration module handles the failure instead of the restoration module within the Network Element. In this way, it is possible to support distributed restoration in the entire network, even in case a number of Network elements do not possess distributed restoration facilities.
Another feature of the present invention is the case wherein the restoration module in the Network management possesses central restoration facilities. In that case, this central restoration mechanism is activated if restoration is necessary and not all Network Elements do possess distributed restoration facilities. The advantage of the central restoration method, over the distributed restoration method, is the use of centrally available network information that facilitates finding an optimum solution, instead of finding a proper solution concerning the restoration of a communications path.
An additional characteristic feature of the present system is that the Network Management Module communicates with said Network Elements via a corresponding Network Management Interface which is implemented according to the q
3
standard, as defined in ITU-T Recommendation M. 3010.
The q
3
-interface, as defined in
ITU
-
T Recommendation M
3010
“Principles for a Telecommunications Management Network
”, 05/96 paragraph 2.3, is used together with an existing co-ordinating Telecommunications Management Network TMN to support the co-operation of distributed restoration with the restoration module in the Network Management modul
Alcatel
Ho Duc
Hsu Alpus H.
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