JPH10257071A - Atm network communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate data rejection due to convergence and to hold communication speed between transmission and reception terminals. SOLUTION: When one of nodes on a main route is about to fall into congestion, a request for reducing transmission speed is received from an RM cell by way of the main route, the transmission speed of the cell for the main route is gradually reduced and on the other hand, the transmission speed of a sub- route is increased by terminals 3, 4. This operation is performed by changing a rate of an address to be attached to the cell. In addition, when the congestion is improved, the transmission speed is returned to a normal state. In this way, apparent cell speed between terminals A and B is held as a maximum speed and the constant communication speed is always held by performing the transmission by dividing a traffic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM (Asynchronous Transfer Mode) network communication system, and more particularly to a communication system in which communication quality does not deteriorate even when congestion occurs.

[0002]

2. Description of the Related Art B-IS for providing high-speed communication services
ATM employs ATM (Asynchronous Transfer Mode). In this ATM, transmission data is divided into a predetermined bit length, and data transmission is performed in an information unit called a cell with a header attached thereto. However, since the data is asynchronous, congestion may occur due to a large amount of unpredictable inflow of information on a network. In order to avoid this congestion in advance, ABR (Av
Various communication schemes such as an ailable bit rate service have been proposed.

FIG. 3 is a block diagram showing a configuration of an ATM network. As shown in FIG. 1, an ATM network 1 has a configuration in which a number of lines are connected via a node 2 and a transmitting user ATM terminal 3 and a receiving user ATM terminal 4 are connected to this network. . The node 2 has a buffer for accumulating cells according to the number of connection lines, and temporarily stores input cells in a buffer when cells input to the node cannot be output immediately due to congestion of an output destination line. And prevent cell discard. However, there is a limit to the buffer capacity, and when a large amount of cells flow in instantaneously, a congestion state occurs, the buffer overflows temporarily, and some cells are discarded.

Therefore, the terminals 3 and 4 monitor the congestion state on the network by exchanging resource management cells (RM cells) and adjust the cell speed to avoid cell discard. First, the terminal 3 sends a maximum cell transmission rate (Peak Cell Rate: PC) to the network and the terminal 4.
R) and the minimum cell transmission rate (Minimum Cell Rate: M)
(CR). When one route 5 is selected from the network and a connection is established between the terminals 3 and 4, the RM cells are exchanged between the terminals 3 and 4.
The congestion state on the connection is written in the RM cell, and the content is updated each time the signal passes through each node and the terminal. The terminal 3 receives the RM cell and monitors the congestion state. The cell rate is adjusted within the range of the PCR from the MCR so that the cell transmission rate is reduced when the cell is about to be congested as shown in FIG.

[0005]

However, although the above-mentioned communication system can avoid data discard, it has a problem that the communication time is long as a whole because the communication speed is temporarily reduced. This hindered the smooth operation of the terminal and was very unsatisfactory for the terminal user. The present invention has been made in view of the above problems, and has as its object to provide a communication method capable of eliminating data discard due to congestion and maintaining a communication speed between transmitting and receiving terminals.

[0006]

In order to achieve the above object, an ATM network communication system according to the present invention performs communication by setting a plurality of routes in advance between a transmitting terminal and a receiving terminal, and establishes one route. When congestion occurs, traffic is distributed to another route to maintain the maximum communication speed between the transmitting and receiving terminals.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 is a block diagram showing the configuration of a network according to the ATM network communication system of the present invention. In FIG. 1, an ATM network 1 has a configuration in which a large number of lines are connected via a node 2 having a buffer, and a transmitting-side user ATM terminal 3 and a receiving-side user ATM terminal 4 are connected to this network. .

[0008] First, when the transmitting-side user ATM terminal 3 (hereinafter, terminal 3) transmits data on the ATM network 1 to start communication with the receiving-side user ATM terminal 4 (hereinafter, terminal 4), the ATM network 1 In determining the route from the terminal 3 to the terminal 4, two different routes that do not overlap, that is, a main route 5 and a sub route 6 are set, and the ATM network issues a connection request to the terminal 4. If the connection is possible, the terminal 4 informs the ATM network 1 of the fact, and notifies the terminal 3 of the completion of the connection along one of the determined routes. When establishing the above routes, the terminal 3 declares the same PCR and MCR for each route. In this way, two connections are established between the terminals 3 and 4, and the terminals 3, 4
The four are connected via an ATM network.

[0009] Then, the terminal 3 orders (numbers) the cells into which the transmission data has been divided, assigns the destinations to the main route and the sub route, and transmits the cells. The terminal 4 restores the cells received from the main route 5 and the sub route 6 based on the numbering information,
Get the original transmission data.

FIGS. 2A and 2B are waveform diagrams showing the cell speed of each route. FIG. 2A shows the cell speed of the main route, and FIG. 2B shows the cell speed of the sub route. As shown from time t0 to t1, the cell rate is usually PC on the main route of the ATM network.
R-MCR is communicated, and the cell rate is MCR in the sub route.
Communicated by.

If one of the nodes on the main route is about to become congested, the terminals 3 and 4 receive a transmission speed reduction request at the timing indicated by t1 from the RM cell periodically transmitted via the main route. In addition, while reducing the transmission speed of the cell for the main route, the transmission speed of the sub route is increased. This operation is performed by changing the ratio of destinations assigned to cells. If the congestion state is still not improved by the cell speed change, a deceleration request is received again, and the cell speed is changed at timings t2 and t3. Then, when the congestion state is improved, the cell transmission rate is returned to the normal state at the timing shown from t4 to t6. By performing the transmission in which the traffic is distributed in this manner, the apparent cell speed between the terminals A and B maintains the PCR, and the communication speed is always constant.

In the above embodiment, the number of routes is two, but the number of set routes is not necessarily two, and may be three or more. In this case, the connection is composed of one main route and a plurality of sub routes, but the allocation of cells allocated to the sub routes due to the deceleration of the main route may be arbitrary. In the above embodiment, the cell transmission rate is returned to the normal state when the congestion state is improved, but there is no problem if communication is performed with the changed cell transmission rate.

[0013]

As described above, the AT according to the present invention is used.
In the M network communication system, when congestion occurs, traffic is distributed to other routes to maintain a constant communication speed between transmitting and receiving terminals, so that communication quality does not deteriorate even if congestion occurs on the network.

[0014]

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an ATM network according to the present invention.

FIG. 2 is a diagram showing a cell rate on each route in the communication system according to the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional ATM network.

FIG. 4 is a diagram showing a cell speed on each route in a conventional communication system.

[Explanation of symbols]

 1 ATM network 2 Node 3 4 ATM terminal 5 Main route 6 Sub route

Claims (1)

[Claims] A communication is performed by setting a plurality of routes between a transmitting terminal and a receiving terminal, and when congestion occurs in one route, traffic is distributed to another route to allow communication between the transmitting and receiving terminals. An ATM network communication system characterized by maintaining a maximum communication speed.