Patent ID: 6957265
Filing Date: 2005-10-18
Classification: H04L,H04Q

Abstract:
1. A method for selecting an optimal path in an Asychronous Transfer Mode (ATM) network having a plurality of links where, for each of the links, Link State Parameters are defined including a group of non delay-oriented (non-D) parameters comprising at least Administrative Weight (AW) and two delay oriented parameters (D-parameters) being Maximum Cell Transfer Delay (MaxCTD) and Cell Delay Variation (CDV), the method being performed by the following steps: a) obtaining two limitations of end-to end quality of service (QoS) parameters of a path to be selected between a source point and a destination point in said network, one of the limitations being Maximum Cell Transfer Delay (MaxCTD b) normalizing a D-parameter CDV by virtually modifying the ATM network so as to make CDV constant for all links of the modified network, by selecting a value of minCDV such, that values of CDV parameter of the network links are substantially represented as respective k-fold multiples of said minCDV, where k is integer; building a modified network by symbolically replacing each of the links, having CDV value of k*minCDV where k>1, with “k” fictitious component links each having the CDV value equal to said minCDV so, that the CDV value of each replaced link be equal to a cumulative value of corresponding CDV values of the “k” fictitious component links; assigning to said “k” fictitious links values of remaining Link State Parameters in a manner providing equivalence of said “k” links to the replaced link from the point of each of the link state parameters; c) constructing a link cost equation comprising a first member reflecting influence of a D-parameter MaxCTD on the cost, and a second member reflecting influence of the group of non-D parameters on the cost, the members being taken with respective relative importance weights, wherein a relative importance weight of the member associated with said D-parameter MaxCTD is defined as R, and a relative importance weight of the member associated with the non-D parameters is defined as (1−R); d) based on said link cost equation, calculating links' costs of the modified network, for one or more values of a ratio between the relative importance weight of the first member and that of the second member, and forming a data base of link costs for each of said one or more ratio values; e) applying a Bellman-Ford-type shortest path algorithm to each of the formed data bases to determine one or more conditional paths for the respective one or more data bases, said algorithm being capable of selecting a minimal cost path among paths limited by a given number of links to satisfy said limitation CDV f) calculating one or more cumulative values MaxCTD g) making a judgment about the optimal path, based on comparing said one or more cumulative values MaxCTD