Telephonic communications – Plural exchange network or interconnection – With interexchange network routing
Reexamination Certificate
1998-06-17
2001-09-11
Matar, Ahmad (Department: 2642)
Telephonic communications
Plural exchange network or interconnection
With interexchange network routing
C379S114030
Reexamination Certificate
active
06289096
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to least cost routing of a call across a communication network.
2. Description of the Related Art
In a communication network where nodes are interconnected by a link, the conventional least cost routing algorithm determines a total value of link costs for each of possible routes between source and destination nodes for comparison with each other to find a least cost route. However, since the link cost is usually represented by economic factors, the least cost route is not always the best route from the view point of network traffic or other requirements. If a failure occurs in a link, a need arises to avoid the failed link. However, the conventional route cost determination on a link-by-link basis would result in the selection of a route which is not optimum for network traffic.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method and a network node for selecting a route in a communication network that is optimum for the network.
According to a first aspect of the present invention, there is provided a method of routing a call in a communication network formed of a plurality of nodes interconnected by links, comprising determining all possible routes between a source node and a destination node in the network, each of the routes being formed of at least one of the links, determining a total cost of each of the routes by summing costs of the links of each route, and modifying the total costs of the routes according to priority of the routes and storing the modified total costs into a memory. Responsive to a connection request, the memory is searched to select a least cost route and a connection request is sent from the source node along the selected route. If a connection is not established by the connection request, a search is made again through the memory for selecting a least cost route by excluding one or more routes previously selected and a connection request is sent again from the source node along the selected route.
According to a second aspect, the present invention provides a network node for a communication network, comprising a memory and a first controller for determining all possible routes between the network node and a destination node, each of the routes being formed of at least one communication link determining a total cost of each of the routes by summing costs of the links of each route, and modifying the total costs of the routes according to priority of the routes and storing the modified total costs into the memory. A second controller is responsive to a connection request for making a search through the memory for selecting a least cost route, sending a connection request along the selected route, and repeating the search through the memory for selecting a next least cost route if a connection is not established by the connection request by excluding one or more routes previously selected.
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Lee, W., “Topology Aggregation for Hierarchical Routing in ATM Networks”, ACM SIGCOMM, pp. 82-92, Computer Communication Review.
Japanese Office Action dated Mar. 2, 1999, with partial translation.
Matar Ahmad
McGinn & Gibb PLLC
NEC Corporation
Tieu Benny Q.
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