Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
1997-02-03
2001-08-07
Nguyen, Chau (Department: 2663)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S397000, C370S409000
Reexamination Certificate
active
06272111
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to packet switching communication and ATM switching communication, and particularly to a routing control system.
2. Description of the Related Art
In connection-oriented communication as represented by ATM (Asynchronous Transfer Mode), one connection is established in one manner at the time of setting up a call and no change is allowed during a call. The application program communicates to the base (communication partner) using this ATM connection. Here, as one means of altering a route in response to congestive state in the network, one routing control method has been proposed by which a plurality of connections from source to destination are set up independently and the connections employed are altered for every information unit (message). The selection of connections at this time is executed only at the transmission node which is the information source. Devices such as terminals, information transfer servers, and routers that become information sources and transmit information are here-inbelow referred to as “transmission terminals.”
In a case in which a transmission terminal transmits an information group made up of a plurality of information units from source to destination by a plurality of routes using a plurality of connections, one connection is used for each information unit transmitted. The plurality of connections that are set up for transmitting from source to destination by a plurality of routes are called the same connection group.
At this time, the ID of the VC (virtual channel) (hereinbelow referred to as “VCI”), or the ID of the VP (virtual path) (hereinbelow referred to as “VPI”), which are the identifiers of each connection, is required at each link (segment) between connection nodes.
FIG. 1
shows a routing table for a routing system of the prior art. In the routing table shown in
FIG. 1
, the input-side VCI are mapped to the output-side VCI. In other words, this table is a correspondence table such that VCI or VPI which are the ID of input packets (hereinbelow referred to simply as “input-side VCI”), are rewritten as the VCI or VPI which are the ID of output packets (hereinbelow referred to simply as “output-side VCI”). This means that, for example, a packet for which input side VCI=100 is rewritten as output side VCI=200 and outputted from the switch. In
FIG. 1
, one input-side VCI is mapped to one output-side VCI.
The first problem of the above-described prior art is the occurrence of a reduction in network throughput and communication quality degradation including delays and cell loss.
The cause of this problem is that, in general, when a network is very large, transmission nodes cannot accurately detect congestive states in the network, due to propagation delay and other factors, so that dynamic selection of optimum routes for good routing efficiency cannot be expected.
A second problem of the prior art is that the VCI and VPI required at each link (segment) between connection nodes are consumed in large volumes due to the plurality of connections used.
The reason for this is that only a limited number of these VCI and VPI are prepared, and, due to the concern that VCI and VPI will be exhausted because of the plurality of VCI and VPI consumed when using a plurality of connections, VCI and VPI must be conserved to ensure effective use of the network.
SUMMARY OF THE INVENTION
In view of these problems of the prior art, the object of the present invention is to provide a routing system that can bring about an improvement of throughput of a network as well as an improvement of communication quality, and moreover, that enables conservation of connection identifiers.
The routing system of the present invention is a routing control system that, for each call, sets up a plurality of connections in advance of transmission of information, selects one connection from this plurality of connections for each unit of transmission information, and then transmits the units of transmission information. The plurality of connections are not changed for sections in which the routes to be taken are different but are consolidated into one connection for sections in which the routes to be taken are the same; and a connecting device provided at the node, which are set up for a plurality of connections to either or to both the input and output sides, discretionary makes either a first connection, which is either the plurality of connections or one consolidated connection, to the input side, or a second connection, which is either the plurality of connections or one consolidated connection, to the output side.
According to the routing system of the present invention as described hereinabove, the connecting device changes connecting relationship between the first connection and the second connection for every unit of the transmission information in accordance with information held by the node indicating either or both the congestive state and the load conditions of a network.
According to the above-described routing system of the present invention, the connecting device can cause connecting relationship between the first connection and the second connection to change in accordance with the connecting information,held by each individual packet of the units of transmission information.
According to the above-described routing system of the present invention, a transmission terminal, which is the source of transmitted information, determines the routing and writes routing information into each individual packet for each transmission information unit; and the connecting device is capable of performing routing using the routing information designated by the transmission terminal.
According to the above-described routing system of the present invention, the method of consolidating routing information at the time of setting up connections is such that, after setting up each connection without consolidating connections, a plurality of connections at each node having a same destination can be consolidated as one connection, and the identifiers of the consequently unused connections can be saved to unused connection identifiers.
According to the above-described routing system of the present invention, a routing procedure at the time of setting up connections is such that, in setting up a plurality of connections at individual node, when there is the second connection set up for a destination which is the same as that of the first connection already set up at the node, the connection identifier of the first connection is mapped to the second connection and each plurality of connections is set up as one consolidated connection.
(1) The plurality of connections existing in parallel in the prior art are concentrated to one connection, and information is communicated using the one concentrated connection. As a result, a single connection identifier is sufficient for a plurality of connections, and the number of connection identifiers used on the entire network can be reduced. In other words, a multiplicity of routes can be switched by the nodes of a network using only a small number of connection identifiers, and load dispersion can be effectively carried out by routing.
For example, although the prior-art system required 100 VCI in a case in which 100 connections of the same connection group use the same link, just one VCI is sufficient for the present invention, thereby allowing a great reduction in the use of VCI.
In addition, rebranching of connection to a plurality of routes from a concentrated connection can be realized while the transmission terminal manages routes.
(2) Instead of the transmission terminal determining the route by which information is to be sent at the time of transmission as in the prior art, when a packet arrives at a node which decides the routing, the node uses the information it has indicating the load state and congestive state of the network together with the information contained in the packet determined by the repeater nodes, and can by using the most recent inf
Boakye Alexander O.
NEC Corporation
Nguyen Chau
Sughrue Mion Zinn Macpeak & Seas, PLLC
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