Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1998-12-23
2004-04-06
Patel, Ajit (Department: 2664)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
Reexamination Certificate
active
06717937
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to routing of telephone calls and, more particularly, to connecting of telephone calls over networks using Internet protocol (IP networks).
2. Background Information
The traditional telephone network is a switched network that provides users with a dedicated end-to-end circuit for the duration of each call. Circuits are reserved between the originating switch, tandem switches (if any), and the terminating switch based on the called party number to create the end-to-end circuit.
Recently, telephone calls have been transmitted over digital networks using packet switched networks using Internet protocol (IP networks), termed voice over IP (VoIP) transmission. Packet-switched IP networks provide shared, virtual circuit connections between users. Voice information to be transmitted across an IP network is converted into digital data and broken up into multiple, discrete packets. Individual packets may travel over different network paths to reach the final destination where the packets are reassembled in the proper sequence to reconstruct the original voice information.
A virtual circuit is created between an originating node that receives the call origination signaling and a terminating node that connects to the called party. The originating node must retrieve an IP address for a node that can complete the call based on the dialed number. A node has a limited capacity for the number of calls it can handle. A plurality of nodes with identical capabilities can be deployed to provide the required capacity for a given location. Therefore, the originating node for a VoIP telephone call may retrieve a list of IP addresses for receiving nodes that can complete the telephone call to the called number. The originating node must then “hunt” through the list of IP addresses to locate a node that has available capacity to handle the call from the originating node. This hunting is time consuming, adds additional traffic to the IP network, and increases the message traffic to the terminating node. Further, since it is impractical for the originating node to query all available nodes, the first node found with available capacity will be selected to receive the call while other nodes with lower utilization remain available.
The quality of service (QoS) for VoIP degrades as congestion increases. The QoS for all calls being handled by a node deteriorates as the number of calls being handled increases. Placing a call to a node other than the least used node results in a lower QoS than would be obtained if the least used node were chosen to handle the call. Further, QoS for all calls being handled by the node is reduced as additional calls are added.
As nodes are added or removed to adjust the capacity of a location, configuration information must be broadcast to all locations on the IP network to make the node available to receive calls. Maintaining the configuration information for even a modestly sized IP network quickly becomes time consuming and difficult.
Accordingly, what is needed is a method and apparatus for managing the nodes at a single location to allow the call handling load to be balanced among all available nodes at the location. Further, the method and apparatus should allow nodes to be added or removed without requiring a change to the configuration information for the IP network.
SUMMARY OF THE INVENTION
A method for receiving a telephone call being transmitted on a network using Internet protocol (IP network) is disclosed. A request to handle the telephone call is received from an originating node on the IP network by a leader node on the IP network. A receiving node, having a receiving address, is selected to receive the telephone call. The receiving node is selected from a set of nodes comprising the leader node and at least one follower node, where each node in the set of nodes can receive the telephone call. The receiving address is transmitted by the leader node to the originating node using the IP network. The leader node causes the originating node to transmit the telephone call to the receiving node using the IP network.
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Blakely , Sokoloff, Taylor & Zafman LLP
Nortel Networks Limited
Patel Ajit
Schultz William
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