Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
2000-01-21
2001-08-07
Olms, Douglas (Department: 2661)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S400000
Reexamination Certificate
active
06272139
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the field of Asynchronous Transfer Mode (ATM) networks and more particularly to a signaling method for rerouting ATM connections within the Private Network Node Interface or Private Network-to-Network Interface (PNNI) domain.
Developed through the efforts of the ATM Forum and detailed in “The ATM Forum Technical Committee, Private Network-Network Interface Specification Version 1.0 (PNNI 1.0),” af-pnni-0055.000, March 1996, PNNI 1.0 is a protocol standard that enables the building of multivendor, interoperable ATM switching networks. The protocol allows for the building and maintenance of large ATM networks because it provides hierarchical, dynamic link-state routing instructions and communication pathways. The protocol permits separate ATM switches within interconnecting networks to continuously communicate and share information. In addition, PNNI defines signaling requests for establishing and taking down point-to-point and point-to-multipoint connections across those networks.
PNNI routing is based on well-known, link-state routing techniques similar to, for example, Open Shortest Path First (OSPF). In addition to the basic link-state mechanism, PNNI provides support for quality of service (QoS) routing, required for applications with real-time requirements and scalability to large global networks. These features provide large- scale networks with a single routing protocol, unlike the Internet strategy of using a number of protocols at various levels.
In these environments, rerouting refers to changing the path of an existing connection anywhere between its two end-points. No user signaling is needed to reestablish the connection as the operation is performed by the network, allowing the calling and called parties to be continuously connected. To establish these connections, PNNI environments operate with peer groups (PG), a collection of logical nodes that exchange information with other members of the group. This information exchange allows all members of the same peer group to maintain an identical view of the PG and for those nodes outside of the PG to exchange messages with the PG as a whole.
PNNI 1.0 does not support rerouting after a connection has been established. One submission to the ATM Forum, entitled
Signaling Procedures For Fault Tolerant Connections
AF/97-0391R1 by D. M. Kushi et al. and E. M. Spiegel (April 1997), however, discussed so-called fault-tolerant connections. According to AF/970391, which is herein incorporated by reference, these connections are automatically reestablished (without user intervention) only in the case of a network failure. When a failure occurs, the fault-tolerant connection is rerouted end-to-end, within the PNNI domain, i.e., between the two user-to-network interfaces (UNI) connecting the calling and called party.
End-to-end and fault-based rerouting schemes are restrictive because they must essentially reestablish the entire connection and as a result, are slower than partial connection rerouting. Therefore, a need exists for a rerouting solution that overcomes the deficiencies of fault tolerant and end-to-end rerouting. The solution should provide a more generic and complete mechanism and protocol that permits connection rerouting for reasons beyond network failures. Path optimization, load balancing, fault tolerance, call priority, etc. should be among the features supported by any PNNI rerouting solution. These rerouting reasons could be considered value added features, providing users of the network with a variety of increased services and potentially better quality connection paths. Fundamental to a generic connection rerouting solution is the ability of the connections to be rerouted along a new path prior to releasing an old path's connection. Finally, the solution should interface with the existing PNNI routing protocols that do not support basic rerouting functions, namely PNNI 1.0.
SUMMARY OF THE INVENTION
The invention meets these needs, and others, by providing a generic rerouting protocol that can be performed on any level of a hierarchical based communication system, such as PNNI.
In accordance with the purposes of the invention as embodied and broadly described herein, a method for managing calls in a network having at least one peer group including a set of nodes includes the steps of establishing a call path connecting a set of nodes and detecting an event associated with the call path. The method also includes the step of determining a new call path connecting a new set of nodes in a peer group and establishing the new call path via the new set of nodes.
Systems and networks are also provided for carrying out the methods consistent with the present invention. In particular, a communications network including a plurality of peer groups with each peer group including a first border node switch configured to detect a rerouting event and transmit a rerouting message upon the occurrence of the rerouting event and a second border node switch coupled to the first border node switch via a reroutable call path and configured to return a connect message upon receiving the rerouting message. The network also includes means for connecting first border node switch to the second border node switch via a rerouted call path upon receiving the connect message at the first border node switch.
In addition, a method for establishing a reroutable call connection includes the steps of receiving a call request at a source node and forwarding a setup message to a destination node, wherein the setup message includes a rerouting information element identifying the call request as a reroutable call request. The method also includes the steps of returning, upon receiving the setup message, a connect message to the source node and connecting the source node to the destination node via the reroutable call connection path.
The advantages accruing to the present invention are numerous. For example, both preemptive rerouting (for the purposes of this invention), i.e.,establishing a new call connection path after the old path has been connected and nonpreemptive rerouting, i.e., establishing a new call path after a successful rerouting procedure has occurred, are supported. In addition, this protocol allows rerouting to be performed between any two border nodes of any peer group or any peer group level, regardless of the level on which the border nodes reside. The goals are further achieved by introducing a variety of information element fields distinguishing rerouting messages from standard PNNI messages and uniquely distinguishing routing segments along a particular connection path.
The summary and the following detailed description should not restrict the scope of the claimed invention. Both provide examples and explanations to enable others to practice the invention.
REFERENCES:
patent: 5699347 (1997-12-01), Callon
patent: 5761192 (1998-06-01), Hummel
patent: 5805593 (1998-09-01), Busche
patent: 5831975 (1998-11-01), Chen
patent: 5831982 (1998-11-01), Hummel
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Nortel Networks Limited
Olms Douglas
Pizarro Ricardo M.
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