JP2001339433A - Device and method for exchanging packet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To process the information of high priority while maintaining conditions such as cost performance or miniaturization of a device in a packet exchange system itself by controlling only a line part to really become the cause of congestion. SOLUTION: In Figure 1, a congestion detecting part 106 monitors a packet inputted from a line to a switching interface transmitting part 107 and detects whether the present line causes the congestion in a switch part at present. Thus, a congestion state detected in the switch part is reported to the congestion detecting part 106 with a congestion notice signal, and on the basis of this congestion notice signal, each of congestion detecting parts 106 judges whether the detecting part itself constitutes the cause of congestion occurrence. When it is judged that the detecting part itself constitutes the cause of congestion occurrence, the transmission of packet to the switch part is controlled according to a prescribed algorithm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a packet switching device and a packet switching method for performing packet communication between terminals, and more particularly to a packet switching device and a packet switching method for discarding packets in a congested state.

[0002]

2. Description of the Related Art In recent years, the use of the Internet has rapidly spread, and accordingly, data communication traffic has increased exponentially. This is evident from the fact that it is almost certain that data communication traffic will exceed voice communication traffic in North America by around 2000 and in Japan by around 2002.

In such a situation, the role of a communication network is changing to how to efficiently transfer an ever-increasing amount of data communication traffic.

For example, in a so-called packet switching system having a switch function such as a router, when a large amount of packets are exchanged in a short time, a state called so-called congestion falls, and information such as packets that cannot be processed is lost. May be discarded.

FIG. 4 shows a block diagram of a general high-speed router as a configuration example of a packet switching system according to the prior art. Referring to FIG. 4, the packet switching system includes a line unit 40 for terminating each of a plurality of lines 401.
2, a switch unit 403 for switching a packet transmitted from each line unit 402, and a switch unit 403.
And a processor 404 for controlling

In order to prevent the occurrence of congestion in such a packet switching system, usually, a buffer is arranged in a switch unit 403 provided in the packet switching system to temporarily hold the packet, and the congestion state is reduced. After the packet is released, a method of exchanging packets again is adopted.

However, the occurrence of the congestion state in the packet switching system depends on the switching speed of the switch unit 403 itself and the storage capacity of the buffer, and the performance of the buffer capacity and the processing speed in the packet switching system. .

However, if a large number of buffers are provided in the switch unit in order to suppress congestion, the processing speed of the switch unit decreases, the size of the packet switching system itself increases, and the cost required for production increases. It becomes the cause.

In the prior art, a packet input buffer is provided in each line unit in the packet switching system, so that when a large amount of packets is temporarily received, the buffer is used to prevent congestion in the switch unit. Was out. Further, when a congestion state is detected in the switch unit 403, a method is adopted in which the input from all the line units 402 is cut off and the data input is stopped until the switch congestion is eliminated.

In the prior art, with such a configuration, the use of a large amount and high-speed buffer required for the switch unit 403 is suppressed, and the size and economy of the switch unit are increased.

[0011]

However, in such a system, when a packet exceeding the storage capacity of the buffer provided in each line unit 402 is received, all the line units are sent to the switch unit 403. Is blocked so that not only the line that is actually causing congestion but also the line that is operating normally is affected.

As a result, packets of each line section 402 which are normally operated are discarded. Further, according to the above-described method according to the related art, a high-priority packet in a line that causes congestion is also discarded.

[0013] Further, as a conventional technique for resolving congestion generated in a line, Japanese Patent Publication No. 2616431 is disclosed.
There is a packet communication system disclosed in the publication.

According to this prior art, a packet transmitting unit for distributing a transmission packet from the inside of a communication device to a plurality of lines, and a packet receiving unit for multiplexing packets received from the plurality of lines and then transmitting the packet to the inside of the communication device. In a packet communication system configured to have a packet congestion state, the packet receiving unit compares the number of packets stored in a buffer for storing received packets with the memory capacity of the buffer. And if it is determined that the own station is in a congested state, the information is added to the packet to temporarily limit transmission to the own station, so that the own station can process the packet. It is configured to reduce the amount of packets to be transmitted and to eliminate the congestion state.

However, the above-mentioned prior art is a means for notifying the restriction to the outside of the own station, and does not eliminate the currently occurring congestion state in the own station. Furthermore, in the above-described conventional technique, when a congestion state occurs, transmission of packets to all adjacent nodes is restricted at random, so that transmission and reception of packets to be processed with priority are also restricted. There is a point.

Accordingly, the present invention has been made in view of the above-described problems, and controls only a line unit that actually causes congestion, thereby reducing the cost and size of the packet switching system itself. It is an object of the present invention to provide a packet switching device and a packet switching method that can process information with a high priority while maintaining the above.

[0017]

According to one aspect of the present invention, there is provided a packet switching apparatus for switching packets, wherein the number of packets to be switched is restricted according to the level of congestion that has occurred. And discarding the packet.

According to a second aspect of the present invention, there is provided a line receiving unit for extracting a packet from data received from a line, and a packet distribution unit for distributing the packet received by the line receiving unit for each assigned priority. Means, a plurality of types of priorities assigned to the packets, a plurality of buffering means for temporarily storing the packets distributed by the packet distribution means for each priority, and packets stored by the buffering means. Packet reading means for reading, congestion detecting means for measuring the number of effective bytes of the packet read within a predetermined period by the packet reading means, switching means for switching the packet read by the packet reading means, and congestion in the switching means Congestion notification means for outputting a congestion notification signal Congestion detection means, a predetermined threshold is set in advance, and when a congestion notification signal is notified by the congestion notification means, compares the number of valid bytes measured by the congestion detection means with a predetermined threshold, It is characterized in that the packet reading means is controlled based on the result of the comparison.

According to a third aspect of the present invention, in the packet switching device according to the second aspect, the congestion detecting means includes, as the predetermined threshold, the first threshold having the lowest value and the first threshold being smaller than the first threshold. When a second threshold having a larger value and a third threshold having a larger value than the second threshold are set, and as a result of the comparison, when the number of valid bytes exceeds the first threshold,
The packet reading means is controlled so as to permit only reading of packets from the buffering means in which the highest-priority packet is stored, and if the result of the comparison exceeds the second threshold, the packet reading means is controlled. Is controlled to prohibit the reading of packets from all buffering means, and if the result of comparison exceeds the third threshold, the packet with the lowest priority is stored in the packet reading means. It is characterized by controlling to discard the packet stored in the buffering means.

According to a fourth aspect of the present invention, in the packet switching device according to the second or third aspect, the congestion notification signal is input to the congestion detecting means via a dedicated control line. I do.

According to a fifth aspect of the present invention, there is provided the packet switching apparatus according to the second or third aspect, wherein the multiplexing means multiplexes the packet and the congestion notification signal, and the packet multiplexed by the multiplexing means. Separating means for separating the congestion notification signal from the congestion notification signal, wherein the congestion notification signal is input to the congestion detection means via a transmission path common to the packets.

According to a sixth aspect of the present invention, in the packet switching device according to any one of the second to fifth aspects, the plurality of buffering means includes a buffering unit for storing a packet having a high priority. It is characterized in that the means is configured to have a larger storage capacity.

According to a seventh aspect of the present invention, there is provided a packet switching method for switching a packet, wherein the switching of the packet is restricted according to the level of congestion that has occurred, and the packet is discarded.

[0024] The invention according to claim 8 is a line receiving step for extracting a packet from data received from the line, and a packet distributing step for distributing the packets received in the line receiving step for each assigned priority. A buffering step of temporarily storing the packets allocated by the packet distribution means in a buffer provided with the number of types of priorities assigned to the packets, and a packet stored in the buffering step. A packet reading step for reading, a congestion detecting step for measuring the number of effective bytes of the packet read within a predetermined period in the packet reading step, a switching step for switching the packet read in the packet reading step, and a switching step Outputs a congestion notification signal when congestion occurs in A congestion notification step, and the congestion detection step, when the congestion notification signal is notified in the congestion notification step, compares the measured number of effective bytes and a predetermined threshold that is set in advance, The packet reading step is controlled based on the result.

According to a ninth aspect of the present invention, in the packet switching method according to the eighth aspect, the congestion detecting step includes, as the predetermined threshold, the first threshold having the lowest value and the first threshold. When a second threshold having a larger value and a third threshold having a larger value than the second threshold are set, and as a result of the comparison, when the number of valid bytes exceeds the first threshold,
In the packet reading step, control is performed such that only reading of the packet from the buffer storing the highest-priority packet is permitted, and as a result of the comparison, if the value exceeds the second threshold, all the packets are read in the packet reading step. Controlling to prohibit the reading of packets from the buffer. If the comparison result indicates that the value exceeds the third threshold, in the packet reading step, the packets stored in the buffer storing the packets with the lowest priority are stored. Is controlled to be discarded.

According to a tenth aspect of the present invention, in the packet switching method of the eighth or ninth aspect, the congestion notification signal is transmitted via a dedicated control line.

[0027] The invention according to claim 11 is the invention according to claim 8.
Or the packet switching method according to 9, further comprising a multiplexing step of multiplexing the packet and the congestion notification signal, and a separation step of separating the multiplexed packet and the congestion notification signal in the multiplexing step, The congestion notification signal is transmitted via a transmission path common to packets.

According to a twelfth aspect of the present invention, in the packet switching method according to any one of the eighth to eleventh aspects, the buffer has a smaller storage capacity as a buffer stores a packet having a higher priority. It is characterized by a large configuration.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A feature of the present invention is a packet switching apparatus and a packet switching method for switching packets,
A buffer for temporarily storing packets received from the line, a congestion detecting unit for detecting that congestion has occurred on the line, and a packet discarding unit for discarding the packets stored in the buffer. It is characterized by:

Based on this, the packet switching apparatus and the packet switching method of the present invention will be described below in detail with reference to the drawings.

First Embodiment {Configuration of First Embodiment} First, a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the packet switching device according to the first embodiment.

Referring to FIG. 1, the packet switching apparatus according to the present embodiment is configured to receive a packet from a line in each line unit 101, receive data of a connected line, and select a packet from the received data. A packet receiving unit 102 that sorts the extracted packets according to the contents such as the priority and the address of the destination, and controls writing to the corresponding buffers 104-1 to 104-n; Buffers 104-1 to 104-n for temporarily holding packets written under the control of the unit 103, and a packet reading unit 10 for controlling reading of packets from the buffers 104-1 to 104-n.
5 and a congestion detection unit 105 that detects the degree of congestion of each line unit 101 by monitoring how much packets have been transmitted to the switch unit connected to the output stage of each line unit 101.
And a switching interface transmitting unit 107 that receives the packet read by the packet reading unit 105 via the congestion detecting unit 106 and transfers the packet to the above-described switch unit.
And is configured.

On the other hand, as a configuration for transmitting a packet input from the switch unit to the line, a switching interface receiving unit 110 for receiving data transmitted from the switch unit to each line unit 101, Transmission buffer 1 for temporarily storing transmission packets received by interface receiving section 110
09, and a line transmission unit 108 that reads out the packet held in the transmission buffer 109 and transmits the packet to the line.

Therefore, in the above configuration, the congestion detecting unit 106 monitors the packet input to the switching interface transmitting unit 107 among the packets received from the lines connected to each line unit 101. As a method of this monitoring, for example, the number of valid bytes of a packet read by the packet reading unit 105 and transmitted from the switching interface transmitting unit 107 to the subsequent switch unit per unit time is measured, and this measurement is performed. From the total number of valid bytes per unit time,
It operates to detect whether or not congestion is occurring in the switch unit.

However, the timing for determining this congestion is
The congestion notification signal for notifying the congestion state generated in the switch unit is configured to be determined at the time of being input to the congestion detection unit 106. In this determination, the validity of the packet transmitted to the switch unit measured as described above is determined. The number of bytes is used to determine whether the own line is causing a congestion state. Therefore, the congestion state detected in the switch unit is notified to the congestion detection unit 106 by a congestion notification signal, and based on this congestion notification signal, each congestion detection unit 106 determines whether or not itself is a source of congestion occurrence. Is determined, and when it is determined that the packet causes the occurrence of congestion, transmission of the packet to the switch unit is controlled according to a predetermined algorithm. As a result, control is performed so that the state of congestion occurring in the switch unit is not deteriorated but is improved.

At this time, the transmission of the packet from each line unit 101 to the switch unit is not stopped, so that the buffers 104-1 to 104-n in each line unit 101 can be used.
Can be configured to receive packets up to the maximum storage capacity. This is a configuration for preventing reception of a high-priority packet from becoming impossible, thereby enabling a high-priority packet to be transferred without being discarded.

Further, the buffer 104-1 is selected according to the priority.
By discarding low-priority packets (which can be replaced with low-necessity packets) from among the packets distributed to ｎn, packets with high priority can be discarded even in a congested state. It is possible to prevent discarding.

Based on the above, the configuration of the first embodiment of the present invention will be described in more detail with reference to FIG.

In the configuration shown in FIG.
01 is provided in each line unit 101.
Terminates the line input from, and extracts the packet input in the form of an optical signal or an electric signal. However, since the configuration of the line receiving unit 102 can be variously modified and implemented without departing from the gist of the present invention, the present invention is not particularly limited.

Further, the line receiving unit 102 that has extracted the packet as described above detects whether or not the received packet contains an error (error). Is added to the packet and transmitted to the packet distribution unit 103 in the subsequent stage.

The packets extracted by the line receiving unit 102 are sorted by the packet sorting unit 103 for each packet content. About this content,
This will be described in detail below with reference to FIG. Further, the information required for distributing the packets in the packet distribution unit 103 can be set according to the conditions (or circumstances) in which the packet switching device according to the present invention is used.

Next, the packets distributed according to the contents by the packet distribution unit 103 are thereafter temporarily stored in buffers 104-1 to 104-n provided for each distribution destination.

Here, the packet distribution unit 103 stores a buffer (buffer 104-1 to buffer 104-1) to which the packet is to be written.
n) is monitored to determine whether packet writing is possible. Therefore, the buffer 104
-1 to n are written in the buffer 104-.
Executed when the corresponding buffer in 1 to n is writable.

The storage capacity of each of the buffers 104-1 to 104-n is configured to be able to sufficiently accommodate a plurality of maximum packets handled by the present invention.
Further, this buffer is provided with the number of types (n of 1 to n) to be distributed by the packet distribution unit 103. However, as a method of configuring the buffers 104-1 to 104-n, it is assumed that a single buffer is divided for each address and used.

After that, the packets written in the buffers 104-1 to 104-n are output to the buffer 10
4-1 to n. This packet reading unit 10
5 is controlled by the congestion detection unit 106.

The congestion detecting unit 106 monitors the data amount of the packet transmitted from the own line to the switch unit. Therefore, the congestion detection unit 106 reads out a packet according to a predetermined algorithm based on the data amount of the packet transmitted to the switch unit within a certain fixed time (unit time).

As the operation, for example, the congestion detecting unit 1
06 sets a plurality of thresholds for the amount of data transmitted to the switch unit, and based on the amount of data transmitted per unit time with respect to this threshold, a buffer (104-1) in which the highest priority packet is stored. To n), and a buffer (104-1 to 104-1) in which the packet with the lowest priority is stored.
n is discarded.

The packets read from the buffers 104-1 to 104-n by the packet reading unit 105 are transmitted to a switch unit (not shown) by the switching interface transmitting unit 107.

The switch section and the switching interface transmitting section 107 are each implemented by being modified in various ways, and are not particularly limited here.

The switch unit monitors the state of congestion in the switch unit based on the data amount of packets stored in a buffer provided in the switch unit, and when the data amount exceeds a preset threshold. Then, a congestion notification signal is transmitted to each line unit 101 through a dedicated signal line.

This congestion notification signal causes the congestion detection unit 10
6 starts an operation of determining whether or not the own line is causing congestion generated in the switch unit. As described above, this determination operation is performed based on the number of effective bits of a packet transmitted to the switch unit via the switching interface transmission unit 107 per unit time.

{Operation According to First Embodiment} The operation according to the first embodiment described above will be described below in detail with reference to the drawings.

The overall operation according to the first embodiment is performed with reference to FIG. Referring to FIG. 1, in FIG. 1, a signal input to a line
Is extracted in the form of a packet. The extracted packet indicates whether or not the packet has been correctly transmitted on the normal transmission path.
Confirmed by RC (Cyclic Redundancy Check) or the like.

Here, error information (signal indicating the error described above) is added to the packet that has not been correctly transmitted by the line receiving unit 102, and the packet is transmitted to the packet distribution unit 103.

As a cause of adding error information to a packet as described above, a buffer (not shown) provided in the line receiving unit 102 is not writable besides the above-mentioned error confirmation by the CRC. Or the packet could not be received correctly for some reason.

The packet distribution unit 103 converts the packet transmitted from the line receiving unit 102 into one of the preset buffers 104-1 to n according to the priority stored in the header of the packet. Send to things.

The priority stored in the header of the packet is, for example, RFC (Request For Comments) 79
1, a TOS (Type of Service) field in an IP (Internet Protocol) packet,
DS (DiffServ) code point specified by RFC2474 and RFC2475, and destination IP
It is determined according to information in the packet such as the address.

This can be generally set according to the environment or situation in which the packet switching device and the packet switching method are used. RFC stands for Internet Engineering Task Forcie (IETF), an Internet research and development institution.
e) is a standard document concerning use of TCI / IP and services published on a server on the Internet, and a number is added to each content.

In this embodiment, this RFC is cited, and R
FC791, 2474, and 2475 are applied. FIG. 5 shows the format of an IP datagram as the structure of the packet.

Referring to FIG. 5, the configuration of the packet used in the present embodiment is such that the header part has a version number (version) of the IP header, the length of the IP header itself (header length), the quality of service of the IP (service type ), The total length of the packet including the IP header and IP data (packet length), an identifier for reconstructing the data whose upper position has been divided, a flag for writing control bits related to packet division, and a fragment (division Sequence number (fragment offset) for a given packet, the time that this packet can exist on the network (lifetime), the protocol at the top, the checksum for the IP header, and the IP of the node that sent this packet. Address (source IP address), IP address (destination I Address) is configured to have options for use during testing or debugging, padding, to adjust to an integral multiple sum of 32 bits of the option. Here, the priority of the packet used in the present invention is the one stored in the above service type.

The packet distribution unit 103 monitors whether or not the buffers 104-1 to 104-n to which the packet is to be written can write the packet.
02 when the packet is received from the buffer 104-
If writing to the corresponding buffer in 1 to n is possible, the received packet is written.

If the packet written at this time contains an error as described above, a signal indicating this error is added.

The buffer 104-
If writing to any of 1 to n is impossible, the packet distribution unit 103 suspends the writing of the packet,
The reception of the packet from the line receiving unit 102 is suspended until the packet can be written in the buffer 104.

Thereafter, in the buffers 104-1 to 104-n, if a signal indicating an error is added to the packet written by the packet distribution unit 103 as described above, the packet is stored in any of the buffers 104-1 to 104-n. The stored packet is discarded without notifying the packet reading unit 105 that the packet is stored.

On the other hand, if the packet written in any of the buffers 104-1 to 104-n is a packet to which a signal indicating an error is not added,
Any of 4-1 to n notifies the packet reading unit 105 that the packet is stored therein.

The buffers 104-1 to 104-n perform an operation of discarding the stored packet in response to the notification from the packet reading unit 105 and the congestion detecting unit 106.

The packet reading unit 105 is connected to the congestion detecting unit 10
6 and a buffer 104- which satisfies a predetermined condition only in a state where reading from the buffer is possible.
The packets are read from 1 to n.

Further, the packet reading unit 105 controls an arbitrary buffer 104-1 according to the control from the congestion detecting unit 106.
To n, the operation of discarding the stored packet is executed.

The congestion detecting unit 106 constantly monitors the data amount of the packet transmitted by the own line to the switching interface transmitting unit 107, and based on the monitoring result and the congestion notification signal from the switch unit, the buffer 104- 1 to n
Of the packet from any one of the above.

Here, when the switch unit is not in the congestion state, that is, when the congestion notification signal is not input from the switch unit, the congestion detection unit 106
For reading packets from any of the buffers 104-1 to 104-n. Therefore, when a packet read permission is input from the congestion detection unit 106, the packet read unit 105
n to read a packet from any of the buffers.

At this time, the operation of reading packets from any of the corresponding buffers 104-1 to 104-n by the packet reading unit 105 follows a predetermined algorithm set in advance.

When the switch unit notifies the congestion detection unit 106 of the switch unit being in a congestion state by a congestion notification signal, the congestion detection unit 106 sends a different algorithm to the packet reading unit 105 to the above. The packet reading unit 105 is controlled so as to read a packet from any of the buffers 104-1 to 104-n according to the following.

<Operation of Congestion Detecting Unit 106> When the switch unit is in the congestion state, the corresponding buffer 104-
Regarding a control method of reading packets from 1 to n,
This will be described below.

In this operation, when a congestion notification signal is input from the switch unit to the congestion detection unit 106, the congestion detection unit 106 first switches to the switching interface unit 107.
It is determined whether or not its own line is causing congestion in the switch unit based on the data amount of the packet transmitted to the switch unit per unit time via the switch.

The criterion for this determination is determined based on a preset data amount threshold and the number of valid bytes of a packet transmitted from the own line to the switch unit per unit time. However, in the present embodiment, it is assumed that a plurality of levels of the preset data amount threshold are provided. This includes, for example, thresholds (high-level thresholds),
When the threshold value is set in three steps of the threshold value (medium level threshold value) and the threshold value (low level threshold value), when the threshold value is exceeded, the highest priority packet is stored. Reading of packets from the buffers 104 (104-1 to 104-n) is permitted to the packet reading unit 105, and when the threshold is exceeded, reading of packets from all buffers 104-1 to 104-n is performed. If the packet exceeds the threshold value, the packet stored in the buffer 104 (104-1 to 104-n) configured to store the packet with the lowest priority is prohibited. It operates to execute control such as discarding according to a predetermined algorithm.

In order to prevent the congestion state in the switch unit from being maintained for a long time,
A timer is provided in the congestion detection unit 106 as shown in FIG.
By measuring the time during which the congestion notification signal continues to be input, if the measured time exceeds a preset time, the lowest priority packet among the packets stored in the buffers 104-1 to 104-n It is configured to discard in order from.

Here, referring to FIG.
Will be described in more detail.

As shown in FIG. 2, the congestion detecting unit 106
It comprises a transmission packet amount monitoring unit 201, a read control circuit 202, and a timer 203.

Here, the transmission packet amount monitoring unit 201
As described above, the operation is performed so as to monitor the number of valid bytes (hereinafter, referred to as a transmission packet amount) of a packet transmitted from the own line to the switch unit, and to notify the readout control circuit 202 of the monitoring result.

On the other hand, based on the transmission packet amount notified from the transmission packet amount monitoring unit 201 and the congestion notification signal from the switch unit, the read control circuit 202 sets a predetermined The control of the packet reading unit 105 is performed according to a predetermined algorithm.

{Effects of First Embodiment} As described above, according to the first embodiment of the present invention, the switch unit which causes the size and cost of the packet switching device and the packet switching method to increase. It is possible to reduce the packet discard rate even when burst traffic is received, without increasing the storage capacity of the buffer provided in.

Further, since the configuration is such that the congestion state is detected for each line, it is possible to impose a packet restriction only on each line unit 101 causing actual congestion. This means that other lines can be operated normally.

Further, when congestion is detected in each line unit 101, packets with lower priorities are discarded, so that the probability of discarding packets with higher priority can be reduced. Therefore, it is possible to protect highly requested information.

Further, since the state of congestion is determined for each of a plurality of stages, it is possible to perform control in a more congested state as compared with control using a dedicated line.

[Second Embodiment] Next, a second embodiment of the present invention will be described in detail with reference to the drawings. The basic configuration in the present embodiment is the same as in the above-described first embodiment. On the other hand, in the second embodiment, the configuration is changed as follows.

That is, in the second embodiment, each line unit 10
By changing the configuration of the buffers 104-1 to 104-n for temporarily storing the packets received in 1, protection of packets with high priority is realized at a higher level.

This corresponds to the buffer 104-1 in FIG.
To n, the buffer storing the high-priority packets has a relatively large storage capacity, while the buffer storing the low-priority packets has a relatively small storage capacity. You.

With this configuration, in the second embodiment, when congestion occurs in the switch unit, a low-priority packet is actively discarded before a high-priority packet. As a result, it is possible to protect packets having a higher priority than in the first embodiment.

This is because when designing the system, it is difficult to implement buffers for all priorities due to mounting problems and cost problems, and to discard high-priority packets. It is also effective in cases where it is necessary to avoid more than in the normal case.

[Third Embodiment] In the basic configuration of the packet switching apparatus and the packet switching method described in the first embodiment, the switch unit notifies the congestion to each line unit using a dedicated line. However, in the third embodiment, this configuration is configured to use the switching interface receiving unit in each line unit.

FIG. 3 shows the configuration of a packet switching device and a packet switching method according to the third embodiment. Referring to FIG. 3, in the present embodiment, a congestion notification unit 322 that converts congestion notification information output from the switch unit 321 into fixed-length data between each line unit 301 and the switch unit 321.
And a multiplexing unit 320 that multiplexes the congestion notification information converted into the fixed-length data as data to be input to the switching interface receiving unit 310.

In this configuration, the congestion notification information multiplexed with the packet and input to each line unit 301 is received by the switching interface receiving unit 310 and then input to the demultiplexing unit 311.

Therefore, the separating unit 311 terminates the input data and separates the data into packets and fixed-length data. Here, the separated packet is transmitted to the transmission buffer 309, and the fixed-length data is transmitted to the congestion detection unit 3.
06.

The fixed-length data separated in this manner is judged by the congestion detecting unit 306 as to whether or not the congestion notification information is directed to the own line. According to a predetermined algorithm as shown in the embodiment,
The reading of packets from n is controlled.

This control method is the same as that of the first embodiment, and reads out a packet having the highest priority according to the level of the congestion state that has occurred in the switch section based on the threshold values provided in a plurality of stages. , And discarding the lowest priority packet.

When a dedicated control line provided for congestion notification is used as in the first embodiment, only two types of judgments as to whether the switch unit is in a congestion state can be performed. However, as in the third embodiment,
Notify the congestion state of the switch unit by fixed length data,
Further, the congestion detection unit 306 monitors the amount of packets transmitted to the switch unit of its own line, so that a more detailed notification of the congestion state can be made as compared with the first embodiment.

However, in the third embodiment, the fixed-length data input from the switching interface receiving unit 310 is terminated at each line unit 301, so that it affects other devices connected to the line. Not something.

[0098]

As described above, according to the packet switching apparatus and the packet switching method of the present invention, the following effects can be obtained.

{Effects of First Embodiment} First, according to the first embodiment of the present invention, the buffer provided in the switch unit which causes the size and cost of the packet switching device and the packet switching method to increase. Without increasing the storage capacity of
Even when bursty traffic is received, the packet discard rate can be kept low.

Further, since it is configured to detect the congestion state for each line, it is possible to impose a packet restriction only on each line unit 101 causing the actual congestion. This means that other lines can be operated normally.

Further, when congestion is detected in each line unit 101, packets are discarded from low priority packets, so that the probability of discarding high priority packets can be reduced. Therefore, it is possible to protect highly requested information.

Further, since the state of congestion is determined for each of a plurality of stages, it is possible to perform control in a more congested state as compared with control using a dedicated line.

{Effects of the Second Embodiment} According to the second embodiment of the present invention, in the effects of the first embodiment, protection of a high-priority packet is realized at a higher level. It becomes possible.

{Effects of Third Embodiment} Further, according to the third embodiment of the present invention, the operation of the first embodiment is realized in accordance with the level of the congestion state that is occurring more. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a system configuration according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a congestion detection unit 1 according to the first embodiment of the present invention.
It is a block diagram which shows the structure of 06.

FIG. 3 is a block diagram illustrating a system configuration according to a third embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration example of a general high-speed router.

FIG. 5 is a block diagram showing a configuration example of a general IP datagram.

[Explanation of symbols]

 101, 301 each line unit 102, 302 line receiving unit 103, 303 packet distribution unit 104-1 to n, 304-1 to n buffer 105, 305 packet reading unit 106, 306 congestion detecting unit 107, 307 switching interface transmitting unit 108, 308 Line transmission unit 109, 309 Transmission buffer 110, 310 Switching interface reception unit 201 Transmission packet amount monitoring unit 202 Read control circuit 203 Timer 311 Separation unit 320 Multiplexing unit 321 Switch unit 322 Congestion notification unit

Claims (12)

[Claims] 1. A packet switching device for switching a packet, wherein the switching device restricts a packet to be switched according to a level of the congestion and discards the packet. 2. A line receiving unit for extracting a packet from data received from a line, a packet distribution unit for distributing the packet received by the line receiving unit for each assigned priority, A plurality of buffering means for providing the number of types of assigned priorities and for temporarily storing the packets distributed by the packet distribution means for each priority, and reading the stored packets from the buffering means Packet reading means; congestion detecting means for measuring the number of valid bytes of the packet read within a predetermined period by the packet reading means; switching means for switching the packet read by the packet reading means; Output a congestion notification signal if congestion has occurred in A congestion notifying unit, wherein the congestion detecting unit is configured to set a predetermined threshold value in advance, and when the congestion notifying signal is notified by the congestion notifying unit, the congestion detecting unit measures the validity measured by the congestion detecting unit. A packet switching apparatus comprising: comparing the number of bytes with the predetermined threshold; and controlling the packet reading unit based on a result of the comparison. 3. The congestion detecting means includes a first threshold having a lowest value, a second threshold having a value larger than the first threshold, and a second threshold having a value higher than the second threshold as the predetermined threshold. And a third threshold having a large value are set. As a result of the comparison,
If the number of valid bytes exceeds the first threshold,
Controlling the packet reading means to permit only reading of the packet from the buffering means in which the highest-priority packet is stored, and as a result of the comparison, exceeding the second threshold value In the case, the packet reading unit controls to prohibit reading of the packet from all the buffering units,
As a result of the comparison, when the value exceeds the third threshold value, the packet reading unit is configured to discard the packet stored in the buffering unit in which the lowest priority packet is stored. 3. The packet switching device according to claim 2, wherein the packet switching device performs control. 4. The packet switching device according to claim 2, wherein the congestion notification signal is input to the congestion detecting means via a dedicated control line. 5. A multiplexing unit for multiplexing the packet and the congestion notification signal, and a separating unit for separating the packet and the congestion notification signal multiplexed by the multiplexing unit. 4. The packet switching device according to claim 2, wherein the congestion notification signal is input to the congestion detection unit via a transmission path common to the packets. 6. The apparatus according to claim 2, wherein the plurality of buffering units have a larger storage capacity as the buffering unit that stores the packets with the higher priority. The packet switching device according to the above. 7. A packet switching method for switching packets, the method comprising limiting packets to be switched according to the level of congestion and discarding the packets. 8. A line receiving step of extracting a packet from data received from a line, a packet distributing step of distributing the packet received in the line receiving step for each assigned priority, and allocating the packet. A buffering step of temporarily storing the packets distributed by the packet distribution means in a buffer provided with the number of types of priorities assigned, for each of the priorities; and reading the stored packets in the buffering step A packet reading step; a congestion detecting step of measuring the number of valid bytes of the packet read within a predetermined period in the packet reading step; and a switching step of switching the packet read in the packet reading step. If congestion occurs in the switching step, A congestion notification step of outputting a notification signal, and wherein the congestion detection step, when the congestion notification signal is notified in the congestion notification step, the number of valid bytes being measured and a predetermined number set in advance A packet switching method, wherein the packet reading step is controlled based on a result of the comparison. 9. The congestion detecting step may include, as the predetermined threshold, a first threshold having a lowest value, a second threshold having a value larger than the first threshold, and a second threshold being larger than the second threshold. And a third threshold having a large value are set. As a result of the comparison,
If the number of valid bytes exceeds the first threshold,
In the packet reading step, control is performed to permit only reading of the packet from the buffer in which the highest priority packet is stored, and as a result of the comparison,
If the value exceeds the second threshold, in the packet reading step, control is performed to prohibit reading of the packet from all the buffers. As a result of the comparison, when the value exceeds the third threshold, 9. The packet switching method according to claim 8, wherein in the packet reading step, control is performed to discard the packet stored in the buffer in which the lowest priority packet is stored. 10. The packet switching method according to claim 8, wherein the congestion notification signal is transmitted via a dedicated control line. 11. A multiplexing step of multiplexing the packet and the congestion notification signal, and a separating step of separating the packet and the congestion notification signal multiplexed in the multiplexing step. 10. The packet switching method according to claim 8, wherein the congestion notification signal is transmitted via a transmission path common to the packets. 12. The packet switching method according to claim 8, wherein the buffer configured to store the higher priority packet has a larger storage capacity. .