Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
2000-03-21
2004-09-14
Kizou, Hassan (Department: 2662)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S408000, C370S432000
Reexamination Certificate
active
06791981
ABSTRACT:
PARTIAL WAIVER OF COPYRIGHT
All of the material in this patent application is subject to copyright protection under the copyright laws of the United States and of other countries. As of the first effective filing date of the present application, this material is protected as unpublished material. However, permission to copy this material is hereby granted to the extent that the copyright owner has no objection to the facsimile reproduction by anyone of the patent documentation or patent disclosure, as it appears in the United States Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to fault tolerant digital communications systems, in general, and more specifically to fault tolerant packet transmission systems involved in the management of multicast communications. Also, this invention generally relates to the field of distributed computing, wherein a plurality of computer machines are interconnected within a communications network, and more specifically with fault tolerant distributed systems.
2. Description of the Related Art
The term multicast in this disclosure refers to the protocol specification defined by the Internet Engineering Task Force (IETF) in the Request for Comments (RFC) specification 1122. In the field of providing a reliable network for the transmission for multicast datagrams, the specification of the protocol is such that a multicast datagram that originated in one node is only propagated directly to other nodes which are connected to the same subnetwork of the node that originated the datagram. In order for a multicast datagram to be received in a node which is not directly connected in the same subnetwork of the node that originated the request, the multicast datagram needs to be “routed.” The routing operation involves the deployment of a routing node, termed a “router”; or package switching node. The location of the package switching nodes, expressed as an Internet Protocol (IP) address, is included in the multicast datagrams.
Multicast is presently considered one of the most efficient protocol for network communications. The justification for this assertion is the fact that nodes which do not subscribe for a specific multicast group will not even receive messages sent to that group. This is a significant advantage over the broadcast, which makes all nodes receive a message, even if there is no subscriber. The receipt of extraneous messages in a node amounts to an unnecessary CPU overhead. However, with the efficiency of multicast, there are difficulties. To begin, multicast requires to be routed, so that a datagram can be forwarded to another subnetwork. Unfortunately, not all routers presently support multicast routing. Also, due to system administrators preferences, the availability of multicast routing can never be assumed (routers may not be configured to route multicast, even if they support such routing).
One multicast routing method and system is disclosed in U.S. Pat. No. 5,361,256, entitled “Inter-Domain Multicast Routing,” with inventors Doeringer et. al, issued Nov. 1, 1994 and assigned to International Business Machines for transmitting a message or data packet from a single sender to a plurality, i.e., a group of receivers, usually called multicasting, within a conventional unicast transmission network, i.e., a network basically not equipped to handed such multicast transmissions.
Another multicast method and system is disclosed in U.S. Pat. No. 5,778,187 entitled “Multicasting Method and Apparatus,” with inventors Monteiro et al., issued Jul. 7, 1998 and assigned to Netcast Communications Corp. for a scalable architecture for delivery of real-time information over a communications network. Embedded into the architecture is a control mechanism that provides for the management and administration of user who are to receive real-time information.
Another multicast method and system is disclosed in U.S. Pat. No. 5,355,371 entitled “Multicast Communication Tree Creation and Control Method and Apparatus,” with inventors Auerbach et al., issued Oct. 11, 1994 and assigned to International Business Machines for administration of the communication path making up the multicast tree in a communications network. The multicast tree itself has been separated form control and administration of the network.
Another multicast method and system is disclosed in U.S. Pat. No. 5,831,975 entitled “System and Method for Hierarchical Multicast Routing in Self-Routing in ATM Networks,” with inventors Chen et al., issued Nov. 3, 1998 and assigned to Lucent Technologies for an extension of the PNNI protocols to support hierarchical multicast routing and signaling for ATM networks. The invention utilizes an extension to a core-based tree algorithm. Instead of a single core node, core nodes are maintained in each peer-group and each level of the hierarchy.
Another multicast method and system is disclosed in U.S. Pat. No. 5,671,222 entitled “Multicast Routing in Self-Routing Multistage Networks,” with inventors Chen et al., issued Nov. 3, 1998 and assigned to Lucent Technologies for multicasting an inlet data cell, received as part of a multicast request, through a self-routing multicast request into one or more intermediate multicast requests, each intermediate multicast request being a unique subset of the original multicast request which enable a non-blocking, self-routing distribution to a subset of the desired outlet of the original multicast request which enables a non-blocking, self-routing distribution to a subset of the desired outlet of the original multicast request in one or two passes through the network, and by generating a non-blocking multicast tree based on the intermediate multicast requests and routing the received inlet data cell to the desire outlet.
Another multicast method and system is disclosed in U.S. Pat. No. 4,807,224 entitled “Multicast Data Distribution System and Method,” with inventors Naron et al., issued Feb. 21, 1989 for a data distribution system and method for the timely, efficient and reliable distribution of data to an unlimited number of remote receiver installations.
Another multicast method and system is disclosed in U.S. Pat. No. 5,790,522 entitled “Method and System for Performing Traffic Congestion Control in A Multicast Data Distribution System Network,” with inventors Fichou et al., issued Aug. 4, 1998 for traffic congestion control is provided for a network node multiport switch capable of switching data packets of different priorities from input lines, via receive adapter, to output lines via transmit adapters.
In order to control the routing of the multicast datagrams, several algorithms exist, which will negotiate the ordering of the routing addresses in a multicast message.. Such algorithms use the notion of “multicast trees.” A multicast tree is determined by the way that the packets are routed through the routing nodes to reach specific destinations. In the case of a Wide Area Network (WAN), there are several ways of routing a datagram, since there are redundant links of routing nodes that form a communication path between any node to points in the WAN. The traditional multicast tree protocols are related to the task of finding an optimal path (of minimal cost) between any two destinations. A common problem that affects tree routing algorithms is that any of the routing nodes may fail due to hardware or software problems. In most cases the failure is not detected because there is no mechanism for monitoring the health of the routing nodes. Accordingly, a need exists to provide an efficient monitoring mechanism which informs every node in a network of the availability status of any other node in the network.
Another problem related to the routing of multicast messages is that traditionally most WAN do not support multicast communications. This can be especially problematic in a network topology where two or more LANs (Local Area N
Cutter Lawrence D.
Fleit Kain Gibbons Gutman Bongini & Bianco P.L.
Gibbons Jon A.
Kizou Hassan
Lee Timothy
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