JPH11298530A - Packet exchange system and its congestion control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct congestion control in an excellent way even when exchanges and multiplexers are distributed in a large network scale or the throughput of exchanges is increased. SOLUTION: Congestion information detected in each communication module in a local system network 200 is distributed for an autonomous period and collected by a radio communication system via a radio antenna 280. The radio communication system 300 acts like a kind of database and predicts congestion based on the congestion information of a packet exchange 250 obtained by a server 240 of a relay system network 210. When the radio communication system 300 predicts congestion, the predicted congestion information is sent to a congestion detection section 270 of the local system network 200 via the radio antenna 280 again. Each communication module controls a packet transmission rate of a multiplexer circuit 260 based on the predicted congestion information to control congestion in the packet exchange 250.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a packet switching system in a digital switching network, and more particularly to a packet switching system suitable for congestion control in a large-scale network and a congestion control method therefor.

[0002]

2. Description of the Related Art When a large amount of traffic is generated in a communication network, a so-called congestion occurs in which communication flows in nodes constituting the network deteriorate.
In a packet switching network, for example, congestion occurs in a packet switch which is one of the nodes. As one of the measures, a packet exchange discards a packet. However, discarding a packet causes a decrease in data transmission quality.
Therefore, in order to guarantee the data transmission quality, if traffic is monitored and packet discard at the switch is predicted,
A congestion control method is used in which a back pressure signal is transmitted to a packet transmitting side to reduce the packet transfer speed on the transmitting side. For example, in JP-A-6-197128, a packet to be output is determined based on a table indicating an empty state of an output buffer transferred from a packet output side.

In particular, the asynchronous transfer mode (ATM: Asyn)
A plurality of media, such as voice and data, are multiplexed in a chronic transfer mode (network) network, and each transfer quality (cell loss rate and delay time).
Real-time congestion control is important to guarantee Conventionally, a feedback control method has been used to realize this control. Congestion is detected by a packet switch or a buffer (congestion detection point) of a separation circuit. That is,
When the queue length in the buffer exceeds the threshold value, it is determined to be congested, and using a common signal line or an in-channel cell,
Notify the preceding packet transmitting side. As a result, the control unit on the packet transmission side lowers the packet transmission speed, thereby preventing packet discarding in the buffer unit. As another method, call admission control (CAC: C
all Admission Control). In this method, the line interface unit determines whether to accept a new cell and proactively controls congestion. On the other hand, in the switch circuit input section of the packet switch, user parameter control (UPC: Usage Pa
control is performed, and congestion is controlled by determining a reporting violation for the call being accepted.

[0004]

However, in the prior art, when the physical distance between the packet switch and the device provided in the preceding stage becomes longer, it takes time to transfer the back pressure signal from the buffer of the packet switch to the preceding device. It is difficult to prevent packet discard even if the packet transmission speed is controlled. To prevent packet discarding, the buffer capacity should be increased in proportion to the processing capacity (throughput) of the packet switch. However, it is not practical to realize a buffer capacity corresponding to a terabit / second class switch. Absent. This is because the buffer capacity becomes too large, and it is considered that mounting is impossible even with the current semiconductor technology.

There is also known a method for realizing a high-speed switching system by using a crosspoint switch. However, this method requires arbitration-based transfer control within one cell time, which results in an increase in capacity. Accordingly, there is a problem that the throughput is not improved. Further, in the related art, an in-channel cell is used for congestion notification, and there is a problem that the data transfer speed is reduced when the congestion information increases.
Furthermore, FIFO (First In F) is used for congestion detection.
(i.e., first out) semiconductor memory,
There is also a problem that the writing and reading times determine the period of the back pressure signal. Also, in the above UPC, traffic is monitored using a leaky bucket algorithm. However, since the cell flow after multiplexing is observed,
VPI (Virtual Path Identifier)
er, virtual path identifier) / VCI (Virtual C
There is a problem that congestion control cannot be performed for each channel identifier (virtual channel identifier).

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a packet switching system and a congestion control method capable of performing good congestion control.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a plurality of first nodes configured to exchange information with each other to adjust a transmission rate of a packet, and to transmit the information from the plurality of first nodes. This is achieved by providing a second node configured to exchange packets. Here, the first node includes, for example, a communication module or a communication multiprocessor circuit in a regional network, and the second node includes, for example, a packet switch. The communication module in the first node comprises:
A multiplexing circuit that multiplexes a plurality of input packets and a congestion detecting unit that adjusts the transmission rate of packets output from the multiplexing circuit by detecting congestion can be provided. As a packet, an asynchronous transfer mode cell (ATM cell) can be used.

[0008] Specifically, the packet switching system according to the present invention includes a plurality of packet transmitting apparatuses for transmitting packets, and a packet switch for exchanging packets transmitted from each packet transmitting apparatus. Each packet transmitting side device is configured to perform congestion detection and adjust a packet transmission rate based on a result of the congestion detection. Also, a congestion prediction device that performs congestion prediction based on the congestion information of the packet switch is provided, and congestion detection can be performed using information from the congestion prediction device.

According to the present invention, in a plurality of nodes constituting a network, each node exchanges congestion information with another node to adjust a packet transmission rate. At each node, a cell multiplexing circuit that multiplexes asynchronous transfer mode cells input from a plurality of input lines, and measures the number of output cells of the cell multiplexing circuit to predict congestion and transmit a cell to the cell multiplexing circuit. And a control unit for adjusting the rate. The congestion can be predicted by calculating the peak tone function or the dispersion index using the measured value of the number of output cells of the cell multiplexing circuit.

Further, in the congestion control method for a packet switching system according to the present invention, a plurality of packet transmission side devices for transmitting packets to a packet switch autonomously detect congestion, and transmit packets based on a result of the congestion detection. The packet transmission rate of the side device is adjusted. In this case, a wireless communication system that performs congestion prediction based on the congestion information of the packet switch is provided, and congestion detection is performed based on information from the wireless communication system. Alternatively, a wired communication system including the Internet that performs congestion prediction based on the congestion information of the packet switch is provided,
Congestion detection is performed based on information from a wired communication system.

Here, the radio communication system has a database containing information on the packet switch and a database containing information on the packet transmitting side device, and uses the information of both databases to transmit the packet from the packet transmitting side device. Outputs a signal to control the rate. When an asynchronous transfer mode cell is used as a packet, congestion control is performed for each virtual path identifier / virtual channel identifier.

As described above, according to the present invention, the congestion detection point is arranged in the device at the front stage of the exchange, and the device at the front stage of the exchange itself detects congestion and controls the transmission speed without using a back pressure signal from the exchange. That is, the apparatus at the front stage of the exchange is regarded as an autonomous decentralized system, congestion information is exchanged by wireless or wired, and congestion determination is performed by using a dispersion index such as a peak tone function. Further, an address filter is arranged in the congestion detection unit so that information for each VPI / VCI can be obtained, and the calculation speed using a counter is made independent of the writing speed and the reading speed.

[0013] This makes it possible to obtain an effective packet switching system and a congestion control method even when the network scale is large and exchanges and multiplexers are dispersed, and when the throughput of the exchanges increases.

[0014]

FIG. 1 is a diagram showing one embodiment of a packet switching system according to the present invention. As shown in the figure, the present packet switching system includes an access network 19
0, regional network 200, relay network 2
10. Access network 19
0 is composed of a plurality of frame converters 220 to 22n. The frame converter 220 transmits the upper IP (Intele
rnet Protocol) frame etc.
It is a device that converts data into TM cells and the like.
It is configured to perform input / output of 10 to 31n. The local network 200 is connected to the access network 190 and includes a plurality of communication modules 230 to 23n.
Consists of Each of the communication modules 230 to 23n
Each has a multiplexing circuit 260 and a congestion detection unit 270. Here, the congestion detection unit 270 is connected to the wireless antenna 280. The transit network 210 is connected to the regional network 200, and is connected to the packet switch 25.
0 and the server 240. As shown, the server 240 is connected to the wireless antenna 290, and the packet switch 250 is connected to another packet switch (not shown) via the output line 255. Here, the physical distance between the relay network 210 and the local network 200 is
For example, it is 100 km or more.

The congestion control in this embodiment is performed as follows. First, the congestion information detected by each communication module in the regional network 200 is delivered at an autonomous cycle, and collected in a wireless communication system (for example, a satellite) 300 via a wireless antenna 280. The wireless communication system 300 is a type of database, and performs congestion prediction based on congestion information of the packet switch 250 obtained from the server 240 of the relay network 210. When the wireless communication system 300 predicts congestion, the wireless communication system 300 sends the congestion information to the congestion detecting unit 270 of the regional network 200 via the wireless antenna 280 again. Each of the communication modules 230 to 23n controls the packet transmission rate of the multiplexing circuit 260 based on the congestion information, thereby controlling congestion in the packet switch 250.
In the present embodiment, the signal from the congestion detecting unit 270 in the communication module is connected to one wireless antenna 280, but may be connected to a different wireless antenna for each congestion detecting unit.

FIG. 2 shows an embodiment in which the congestion is predicted by wire. As shown, the communication module 320 includes a plurality of multiplex circuits 360 to 36n. Each multiplexing circuit 3
Input lines 3 corresponding to the input sides of 60 to 36n, respectively.
40 to 34n are connected, and a switch circuit 33 is provided on the output side.
0 is connected. The output side of the switch circuit 330 is connected to a plurality of output lines 350 to 35n.

The congestion control of this embodiment is performed as follows. As shown in the figure, a wired network 370 such as the Internet is connected to the multiplex circuits 360 to 36n, and a data management server 375 is arranged in the wired network 370. The data management server 375
Congestion prediction is performed based on the congestion information obtained from the wired network 370. The communication module 320 controls the packet transmission rate of the multiplexing circuit 360 based on the congestion information, thereby controlling the congestion in the packet switch (switch circuit 330).

FIG. 3 is a block diagram showing a case where a communication multiprocessor circuit 380 is used instead of the communication module 230 in the packet switching system of FIG. This circuit is connected to the packet switch 250 of FIG. 1, and accommodates a plurality of input lines 390-39n and multiplexes packets into one.
To two output lines 420. As shown in the figure, the circuit includes a plurality of FIFO memories 400 to 40n,
Cell multiplexing circuit 410 connected to memory, output line 42
It comprises an address filter 430, a counter circuit 440, a memory 450, an arithmetic circuit 460, a burst determination circuit 470, and a control circuit 480 connected to 0.

The congestion control in this embodiment is performed as follows. Now, considering the case where the input packet is an ATM cell, in this embodiment, the address filter 4 is used.
At 30, the ATM cells are separated for each VPI / VCI. The counter circuit 440 measures the number of cells for each VPI / VCI. The period of the counter is equal to or higher than the writing and reading speed of the memory, for example, 1 millisecond. Memory 4
Reference numeral 50 stores the number of cells measured for each of the above-described cycles for channels 1 to n. For example, as in the burst determination calculation table shown in FIG. 4, the number of arriving cells for each channel (VPI / VCI) in the periods 1 to M is recorded in the memory 450. This figure shows an example of measuring M times. Based on the number of arriving cells, the arithmetic circuit 460 calculates the average and variance of the number of arriving cells for each channel. The calculation result is, for example, as shown in FIG. The burst determination circuit 470 calculates the peak tone function z [F] shown in the following (Equation 1) or the dispersion index I (Ind
The burstiness is determined using ex of Dispersion.

[0020]

(Equation 1)

[0021]

(Equation 2)

Where Var [] is the variance, E [] is the average, St is the number of busy servers when the time is positive, and Nt
Is the number of cells arriving at time (0, t). For the peak tone function z [F] shown in (Equation 1) or the dispersion index I shown in (Equation 2), for example, “Peakness M”
easys for Traffic Char
activation in High-Spee
d Networks ”, IEEE INFOCOM '
97 (April 7-11, 1997).

In this example, the dispersion index I is used, and for example, it is predicted that congestion will occur in a channel having a dispersion index of 1 or more. In FIG. 4, channel 1 (VPI / VCI = 10
At 0/1), the dispersion index is 1.13, and it is predicted that congestion will occur. This result is notified to the control circuit 480. The control circuit 480 controls the cell transmission rate based on this notification. This avoids congestion in the packet switch 250 of FIG.

FIG. 5 is a diagram showing another embodiment of the packet switching system according to the present invention. In this embodiment, as shown, a plurality of communication multiprocessor circuits 500 to 50n are connected to a packet switch. In this example, a shared memory type ATM switch 510 having an input port n and an output port n is shown as a packet switch. The ATM exchange may be an ATM exchange having a buffer configuration such as an output buffer type. The ATM exchange 510 is connected to a route server 670 having functions such as address resolution and an IP packet forward engine. This server 670 is connected to the wireless antenna 550. On the other hand, the communication multiplex processor circuits 500 to 50n shown in the figure are configured to accommodate a plurality of input lines 390 to 39n and to transmit multiplexed packets to one output line 520 to 52n, respectively. ~ 40n, each FI
Cell multiplexing circuit 410 connected to FO memory, address filter 430 connected to output line, counter circuit 4
40, a memory 450, and a control circuit 480. The configuration of this processor circuit is basically the same as that of the communication multiplex processor circuit 380 in FIG.
In that it is connected to

The congestion control in this embodiment is performed as follows. For example, consider a case where outputs of a plurality of input ports 520 to 52n in the ATM switch 510 are concentrated on one output port 530. First, the output of the memory 450 of each communication multiplex processor circuit is sent to the wireless communication system 300 via the wireless antenna 490, respectively. On the other hand, the congestion information of the ATM switch 510 is similarly sent from the route server 670 to the wireless communication system 300 via the wireless antenna 550. The wireless communication system 300 determines burstiness based on these pieces of information and performs congestion prediction. The configuration and the like of the wireless communication system 300 will be described later. When the radio communication system 300 predicts congestion, the congestion information is sent to the control circuit 480 of each communication multiprocessor circuit via the radio antenna 490. Each control circuit 480 controls the cell multiplexing circuit 410 based on the congestion information. Thereby, the specific VPI /
Congestion for each VCI is controlled. As described above, in the present embodiment, by discarding the congestion information autonomously between the communication multiplex processors, it is possible to prevent cell discard at the specific output port.

FIG. 6 is a functional block diagram showing an example of the wireless communication system 300. The system includes an input unit 58
0, an output unit 590, databases 600 and 610, arithmetic circuits 620 and 630, a comparator 640, a burst determination circuit 650, and wireless antennas 560 and 561. The database 600 has congestion information from each communication module or communication multiprocessor circuit, and the database 610 has management information of a packet switch (ATM switch). Based on the information, the arithmetic circuits 620 and 630 perform a predetermined operation, and based on the result, the comparator 640 compares the congestion information for each VPI / VCI, and the burst determination circuit 650 determines the burstiness. A signal is transmitted from the wireless antenna 561 for the VPI / VCI determined to be a burst. In accordance with this signal, the control circuit 480 of FIG. 5 controls the cell transmission rate to avoid congestion.

FIG. 7 is a diagram for explaining the effect of the present invention. As shown in the figure, in the conventional method, in order to reduce the packet loss rate in the exchange to a specified value or less, it was necessary to increase the buffer size of the exchange in proportion to the switch capacity. On the other hand, in the present invention, since the delay time of the back pressure signal from the exchange can be neglected, the required buffer size may be about half or less as compared with the conventional system. For this reason, even when the processing capacity of the exchange is improved, traffic congestion control can be realized with the same buffer architecture as that of the small-scale exchange. Also, by using the present invention, congestion control can be performed without using a back pressure signal from the packet switch, so that effective quality control can be performed even if the packet switch and the communication module are geographically separated.

[0028]

According to the present invention, it is possible to obtain a packet switching system and a congestion control method capable of performing good congestion control.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a packet switching system according to the present invention.

FIG. 2 is a diagram showing an embodiment of a congestion control method according to the present invention.

FIG. 3 is a diagram illustrating a configuration example of a communication multiplex processor circuit.

FIG. 4 is a diagram showing a burst determination calculation table.

FIG. 5 is a diagram showing another embodiment of the packet switching system according to the present invention.

FIG. 6 is a functional block diagram illustrating a configuration of a wireless communication system.

FIG. 7 is a diagram for explaining the effect of the present invention.

[Explanation of symbols]

 190 Access Network 200 Regional Network 210 Relay Network 220-22n Frame Converter 230-23n Communication Module 240 Server 260 Multiplexer 270 Congestion Detector 280,290 Wireless Antenna 300 Wireless Communication System 310-31n Data Packet

Claims (13)

[Claims] A plurality of first nodes configured to exchange information with each other to adjust a packet transmission rate;
And a second node configured to exchange packets transmitted from the plurality of first nodes. 2. The first node includes a multiplexing circuit that multiplexes a plurality of input packets, and a congestion detecting unit that adjusts a transmission rate of packets from the multiplexing circuit by detecting congestion. The packet switching system according to claim 1, wherein: 3. The packet switching system according to claim 1, wherein an asynchronous transfer mode cell is used as the packet. 4. A packet transmission apparatus comprising: a plurality of packet transmission apparatuses for transmitting packets; and a packet switch for exchanging a packet transmitted from each of the packet transmission apparatuses. Each of the packet transmission apparatuses performs congestion detection. And a packet switching system configured to adjust a packet transmission rate based on a result of the congestion detection. 5. The packet exchange according to claim 4, further comprising a congestion prediction device for performing congestion prediction based on the congestion information of the packet switch, and performing congestion detection using information from the congestion prediction device. system. 6. A node configured to exchange congestion information with another node to adjust a packet transmission rate. 7. A cell multiplexing circuit for multiplexing asynchronous transfer mode cells input from a plurality of input lines, and measuring the number of output cells of the cell multiplexing circuit to predict congestion and to estimate the congestion. A control unit for adjusting a cell transmission rate. 8. The system according to claim 7, wherein the control unit is configured to calculate a peak tones function or a dispersion index by using a measured value of the number of output cells of the cell multiplexing circuit, and to predict congestion. Nodes. 9. A plurality of packet transmitting apparatuses that transmit packets to a packet switch autonomously detect congestion, and adjust a packet transmission rate of the packet transmitting apparatus based on a result of the congestion detection. A congestion control method for a packet switching system. 10. The packet exchange according to claim 9, further comprising a radio communication system for performing congestion prediction based on congestion information of said packet switch, and performing congestion detection based on information from said radio communication system. System congestion control method. 11. The communication system according to claim 9, further comprising a wired communication system including the Internet for performing congestion prediction based on congestion information of the packet switch, and detecting congestion based on information from the wired communication system. Packet switching system. 12. A packet transmission system comprising a database containing information on a packet switch and a database containing information on a packet transmission side device, and controlling a packet transmission rate of the packet transmission side device using the information of both databases. A wireless communication system configured to output a signal. 13. The wireless communication system according to claim 12, wherein an asynchronous transfer mode cell is used as the packet, and a control signal is output to perform congestion control for each virtual path identifier / virtual channel identifier.