JP2533103B2 - Packet exchange method - Google Patents

Description

DETAILED DESCRIPTION [Table of Contents] Outline Industrial field of application Conventional technology Problems to be solved by the invention Means for solving the problem Action Example Embodiment of the invention [Outline] Transmission in the packet switching system The buffer is configured with multiple FIFOs that support the packet attributes, the receive buffer is configured with multiple FIFOs that support the packet output route and attributes, and the packet transfer on the transmission route is restricted for each packet attribute. By restricting the packet transfer in the switch for each outgoing route or attribute of the packet, it is possible to prevent a decrease in throughput during congestion control.

[Industrial applications]

The present invention relates to congestion control of a high speed packet switching network, and more particularly to a packet switching system capable of preventing a decrease in throughput during congestion control in the entire high speed packet switching network.

In a packet-switched network, packets are probabilistically generated at data terminal devices, and if a large number of terminal devices send packets at once, a large number of packets will enter the network and the service standards defined by the network cannot be maintained. Such congestion occurs. In such a case, congestion control is required to quickly return the network to the normal operating state without reducing the throughput of the entire packet switching network.

In this specification, the FIFO is a first-in first-out buffer.

[Conventional technology]

In a packet switching network, user data is stored and transferred repeatedly at each switching station (machine) and arrives at the other party. Therefore, it is necessary to control the flow of user data, that is, traffic control.

Traffic control includes flow control for eliminating imbalance of transmission / reception throughput and smoothing of transmission throughput, and congestion control for preventing network quality deterioration and lockup due to congestion in the network.

Flow control is a logical channel level control that monitors the packet flow rate on a single logical channel, and a terminal level control that monitors the packet flow rate to a single terminal. Enables reduction of buffer amount by smoothing transmission throughput.

The control forms of this flow control include an end-to-end flow control system and a network-to-end flow control system. The end-to-end flow control system includes, for example, a window control system including a packet retransmission recovery procedure. In this window control method, the number of packets (window size) that can be continuously sent is determined for each logical link, and after sending a fixed number of packets, the sending terminal device sends the next packet until the receiving side gives an instruction to allow sending. Is a method of controlling the transmission of the.

On the other hand, even if the flow control at the end-to-end logical channel level is normally performed, packets exceeding the throughput of the terminal device may arrive stochastically, and in this case, an excessive amount of packets may enter the network. In order to prevent the inflow of packets, it is necessary to perform network-end flow control, such as discarding packets that overflow in the buffer without permission.

Such flow control is performed by the network 11 as shown in FIG.
Is performed between the edges 13 and 15 (accommodation portions of the terminals 17 and 19) of the network 11 and, for example, the inside of the network 11 becomes congested, and each relay exchange 21
When retransmission control is performed between the edges 13 and 15 of the network 11 for the packet discarded in step 1, the congestion in the network 11 may increase further.

Therefore, it is necessary to perform traffic control (congestion control) at the switching network level in order to prevent congestion in the entire network. This congestion control regulates the total amount of packets flowing into the exchange or the network, and includes network-end control that directly regulates the terminal device and intra-network control such as regulation of the adjacent exchange.

In the in-network control, an exchange (machine) that has detected a congestion state sends a congestion notification packet to all exchanges (machines). The switching center (machine) that has received the congestion notification packet regulates packet transmission to the switching center (machine).

[Problems to be solved by the invention]

By the way, such a conventional congestion control method, for example, when a certain switching station (machine) in the network is congested, congestion will spread to the entire network by only limiting packets from adjacent stations. It is necessary to notify all the switching stations (machines) in the network of the congestion to regulate the transfer of packets, and to regulate the packets addressed to the congestion stations at the entrance of the network.

FIG. 11 is a diagram for explaining an example in which the throughput is reduced by the congestion control corresponding to the congestion of a specific outgoing route in the packet switch.

The packet switch shown in FIG. 11 has outgoing routes A and B and incoming routes C and D, and is an example of the case where the transfer of packets addressed to outgoing route A is restricted due to congestion. .

Normally, packets are transferred via the packet switch 31 between the reception buffers 33 and 35 of the ingress routes C and D and the transmission buffers 37 and 39 of the egress routes A and B.

Here, when the output of the packet addressed to the outgoing route A is stopped in the receiving buffers 33 and 35, the transfer of the packet destined to the next outgoing route B is also stopped, and the throughput of the entire network is significantly reduced. There was a point.

The same applies when, for example, the transmission buffer 37 following the outgoing route A overflows in the packet switch and the transmission of packets addressed to the outgoing route A is stopped.

It is an object of the present invention to provide a packet switching system capable of preventing a decrease in throughput of the entire network when controlling packet congestion.

[Means for solving problems]

 FIG. 1 is a block diagram of the principle of the present invention.

In the figure, the receiving buffers 110 and 120 include a plurality of FIFOs that form a queue corresponding to packet output routes and attributes between the packet switches 150 and the respective input routes 101 and 103 of the packet switches that form the packet switching network. .

The transmission buffers 130 and 140 are provided for each outgoing route 1 of the packet switch.
A plurality of FIFOs forming a queue corresponding to packet attributes are included between 05 and 107 and the packet switch 150.

The packet transfer restricting means 160, 170 restricts packet transfer according to the state of each FIFO.

It is preferable that the packet transfer restriction means 160, 170 be configured to restrict the packet transfer of the attribute between the adjacent packet exchanges.

In addition, the packet transfer restricting means 160 and 170 are provided with the receiving buffers 110 and 120 and the transmitting buffers via the packet switch 150.
It is preferable that the packet transfer of the outgoing route and the attribute is restricted between 130 and 140.

[Action]

According to the present invention, the packet transfer restriction means 160, 170 controls transfer of a packet having the attribute to an adjacent packet switch according to the output route of the packet in the reception buffer 110, 120 and the state of each FIFO provided for the attribute. Do it. In addition, in the packet switch in which the transfer of the packet having the attribute is restricted, the packet transfer restricting means 160, 170
Controls the adjacent packet switch so as to stop the transfer of the packet having the attribute.

Further, according to the state of each FIFO provided in the transmission buffers 130, 140 corresponding to the packet attributes, the packet transfer restriction means 160, 170 are provided between the reception buffers 110, 120 and the transmission buffers 130, 140 via the packet switch 150. It controls to stop the transfer of the packet of the route and the attribute.

Therefore, when transfer of a packet having a certain attribute is restricted by an adjacent packet switch, transfer of the packet having the attribute is stopped. If the FIFO corresponding to the attribute overflows in the transmission buffer of the outgoing route where the transfer is stopped, the packets of the outgoing route and the attribute are transferred to all the receiving buffers in the packet switch. It can be stopped. Furthermore, in the reception buffer in which the transfer of the packet of the attribute is stopped, when the FIFO corresponding to the attribute overflows, the transfer of the packet of the attribute can be restricted to the adjacent packet switch.

In other words, in the packet switching network, transfer restrictions can be imposed according to the attributes of the packets, so that the decrease in throughput can be suppressed to the minimum.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In the packet switching system of the present invention, packets in the packet switching network are grouped according to their attributes (for example, priority and burstiness). The FIFO for sending the packet to the outgoing route of the packet switch is separately provided for this attribute. Also, the packet received on the input path is
Provided separately for each combination of attribute and outgoing route
A queue is created in each FIFO.

Hereinafter, a set of these plural FIFOs provided corresponding to the transmission path is referred to as an M-FIFO (multiplex FIFO), a reception buffer is referred to as a reception M-FIFO, and a transmission buffer is referred to as a transmission M-FIFO.

 FIG. 2 shows the configuration of an embodiment of the present invention.

In the figure, the packet switch comprises a plurality of transmission line corresponding units 210, 220 connected to the input routes 201, 203 and output routes 205, 207, respectively, and a packet switch (PSW) 230 for performing packet exchange between the transmission line corresponding units 210, 220. Composed.

The transmission line corresponding units 210 and 220 are respectively connected in cascade between the input routes 201 and 203 and the packet switch 230, the reception control units 211 and 221, the reception M-FIFOs 212 and 222, and the PSW input unit 2 respectively.
13,223, the transmission control units 214 and 224 that are connected in cascade between the packet switch 230 and the outgoing routes 205 and 207, and the transmission M-FIF.
It is configured by O215 and 225 and transmission path sending units 216 and 226.

When the packet is received from the transmission path to the input path 201 in the transmission path corresponding unit 210, the reception control unit 211 analyzes the packet header (logical channel number, LCN) to determine the output path and attribute of the packet. Then, it is input to the FIFO corresponding to the combination of the outgoing route and the attribute in the receiving M-FIFO 212. The PSW input unit 213 takes out the packet from the receiving M-FIFO 212 and sends it to the packet switch 230.

The packet switch 230 transfers the packet to the transmission control unit 224 of the transmission line corresponding unit (for example, 220, and so on) having the designated outgoing route.

The transmission control unit 224 inputs the packet received from the packet switch 230 into the designated FIFO of the transmission M-FIFO 225 according to its attribute. The transmission path sending unit 226 takes out the packet from the sending M-FIFO 225 and sends it to the outgoing path 207.

Next, at the time of congestion control, a control signal for controlling packet transfer between packet switches, and further, in the packet switch, M-FIFOs 212,222 for reception and M-FIFOs 214,2 for transmission.
The flow of control signals that regulate packet transfer between 24 will be described.

The flow of control signals for controlling packet transfer between packet switches is such that when the packet storage amount of the receiving M-FIFOs 212, 222 exceeds a predetermined value, a "transmission path input congestion notification" 241 for the exceeded FIFO is transmitted. In response to this, the transmission path sending sections 216 and 226 send the transmission path sending sections 216 and 226 a “transfer stop command packet” 243 that stops sending packets of the attribute to other packet switches. 2
Send to 07.

Further, the reception control units 211 and 221 which have received the "transfer stop command packet" 243 'transmitted from another packet switch via the transmission path, transmit the "attribute corresponding packet transmission restriction signal" 245 to the transmission path transmission units 216 and 226. . As a result, the transmission path sending units 26 and 226 send the packet having the attribute to the transmission M-
Stop sending from the FIFO 215, 225 to the outgoing route 205, 207.

FIG. 3 is a frame format showing an example of the “transfer stop command packet” 243. In the figure, a "transfer stop command packet" 243 is a logical channel number (LCN) 301 indicating that it is a transfer stop command packet, and an attribute number 0.
.., 319. Transfer stop information 310, 311, ...

The flow of control signals for controlling packet transfer in the packet switch is such that when the packet storage amount in the transmission M-FIFO 215,225 exceeds a predetermined value, the PSW input units 213,223 receive
“Transmission path output congestion notification” 251 is performed, and PSW input section 213, 22
3 is all the transmission line corresponding parts 210, 220 in the packet switch
In response, the “outgoing route congestion notification packet” 253 for stopping the sending of the packet of the outgoing route and the attribute is sent. The transmission control units 214 and 224 that have received this “outgoing route congestion notification packet” 253 ′ from the packet switch 230
To "W input section 213, 223""Outgoing route / attribute compatible transfer control signal" 25
Send 5. As a result, the PSW input units 213 and 223 stop the transfer of the packet of the output route and the attribute.

FIG. 4 is a frame format showing an example of the “outgoing route congestion notification packet” 253. In the figure, the “outgoing route congestion notification packet” 253 is composed of a logical channel number (LCN) 401, an outgoing route number 403, and an attribute number 405 indicating that it is an outgoing route congestion notification packet.

 The configuration of each part is shown below.

FIG. 5 shows an embodiment of the M-FIFO (212,215,222,225).

In the figure, the M-FIFO has a configuration in which a plurality of FIFOs 501, 502, 503 are arranged in parallel, and a packet input 511 and a packet output 513 are switched by switches 505, 507, respectively. The switching control of the switch 305 is performed by a FIFO selection signal (6
15, 815), and switching control of the switch 507 is performed by a FIFO selection signal (715, 915) described later.

Further, it has a FIFO control unit 509 which constantly monitors the packet storage amount of each of the FIFOs 501, 502, 503 and notifies the storage amount information (241, 251, 713, 913) to the outside.

Note that the reception M-FIFOs (212, 222) are provided with FIFOs 501 to 503 corresponding to the number of combinations of outgoing route × attribute corresponding to the outgoing route and attributes of the packet. M-FIFO for transmission (215,22
In 5), FIFOs 501 to 503 are provided as many as the number of packet attributes.

FIG. 6 shows an embodiment of the reception controller (211, 221).

In FIGS. 2 and 6, the header of the packet 611 input from the input routes 201 and 203 has a logical channel number (LCN). When this logical channel number (LCN) is input as the address of the mapping memory 601, a signal 613 indicating the logical channel number (new LCN) in the outgoing route, the packet attribute number and the outgoing route number is sent to the header reassigning unit 603.
To the FI corresponding to the outgoing route and attributes of the packet.
The FO selection signal 615 is sent to the receiving M-FIFOs 212 and 222.
Further, the switch 605 provided in the input section of the header replacement section 603 is provided with an opening / closing control signal 617 from the mapping memory 601.
Is sent. This information can be
It is stored in the mapping memory 601 when setting C).

If the input packet 611 is a data packet, the switch 605 is closed, and the header rearrangement unit 603 determines the logical channel number (LCN) of the packet based on the signal 613 as the logical channel number (new LCN) in the outgoing route. ), The attribute number and the outgoing route number are added to the beginning of the packet and output (619).

When the input packet 611 is the “transfer stop command packet” 243, the logical channel number (LCN) is the number indicating it. Therefore, the mapping memory 601 sends the “attribute corresponding packet sending restriction signal” 245 to the transmission path sending units 216 and 226. At the same time, switch 605
Is opened and this "transfer stop command packet" 243 is discarded.

 FIG. 7 shows an example of the PSW input section (213, 223).

2 and 7, the receiving M-FIFOs 212, 22 are shown.
When the packet 711 from 2 is transferred to the packet switch (PSW) 230, the switch 701 is selected to the a side. The FIFO having a packet in the receiving M-FIFO 212, 222 is
The control unit 703 sends the output route from the FIFO control unit (509).
Detected by the packet presence / absence signal 713 in the attribute corresponding FIFO, F
One FIF in the receiving M-FIFO 212, 222 by the IFO selection signal 715
Specify O to take out packet 711. The extracted packet 711 is output via the switch 701.

When the “outgoing route / attribute corresponding transfer regulation signal” 255 is input from the transmission control units 214 and 224, it is written in the outgoing route / attribute corresponding transfer regulating register 705. After that, M-FIFO2 for reception
Even if there is a packet in the FIFO corresponding to the output route / attribute in 12,222, the packet extraction process is not performed.

Further, when the “transmission path output congestion notification” 251 corresponding to the packet attribute is input from the transmission M-FIFO 215, 225, the control unit 703 issues an operation command 717 to the outgoing path congestion notification packet creation unit 707. In addition, the selection signal 719 of the switch 701 is transmitted, the switch 701 is switched to the side b, and the “outgoing route congestion notification packet” 253 from the outgoing route congestion notification packet creating unit 707 is sent.
Is sent.

 FIG. 8 shows an example of the transmission control units 214 and 224.

2 and 8, the packet switch (PS
The packet 811 input from the W) 230 has the attribute number separating unit 8
At 01, the packet is separated into an attribute number and a packet, and the packet 813 is sent to a designated FIFO in the transmission M-FIFOs 215 and 225 according to the FIFO selection signal 815 corresponding to the separated attribute number.

When the packet 811 input from the packet switch (PSW) 230 is the “outgoing route congestion notification packet” 253, the logical channel number (LCN) is the number indicating it. Therefore, the regulation signal separation unit 803 is
The "outgoing route / attribute corresponding regulation signal" 255 is transmitted to 3,223.

FIG. 9 shows an embodiment of the transmission path sending unit (216, 226).

2 and 9, the transmission M-FIFOs 215 and 22 are shown.
When the packet 911 from 5 is sent to the outgoing routes 205 and 207, the switch 901 is selected to the a side. M-FIFO21 for transmission
The FIFO having packets in 5,225 is FI in the control unit 903.
The packet 911 is taken out by being detected by the attribute presence / absence FIFO packet presence / absence signal 913 sent from the FO control unit (509) and designating one of the transmission M-FIFOs 215 and 225 by the FIFO selection signal 915. The extracted packet 911 is output via the switch 901.

Further, when the “attribute corresponding packet transmission regulation signal” 245 is inputted from the reception control units 211, 221, it is written into the attribute corresponding transmission regulation register 905. After that, even if there is a packet in the FIFO corresponding to the attribute in the transmission M-FIFO 215,225,
No packet extraction processing is performed.

Further, when the “transmission path input congestion notification” 241 corresponding to the packet output path or attribute is input from the receiving M-FIFOs 212 and 222, the control unit 903 causes the transfer stop command packet creation unit 907.
To the output routes 205 and 207, the operation command 917 is issued to the controller 901, the selection signal 919 of the switch 901 is transmitted, the switch 901 is switched to the b side, and the “transfer stop command packet” 243 from the transfer stop command packet creating unit 907 is output. Send out.

The configuration of each unit described above is merely an example, and the present invention is not limited to this.

In the packet switch 230, the reception control units 211, 221
In accordance with the outgoing route number added in step 1, exchange control is performed to transfer the packet to the outgoing route (transmission control units 214, 224), but at this time, this outgoing route number is discarded. The configuration of the packet switch 230 for performing such control is omitted because it is not directly related to the description of the present invention, but is described in detail in the patent application by the same applicant, Japanese Patent Application No. 60-252253, “Packet Switching System”. Are described in.

〔The invention's effect〕

As described above, according to the present invention, it is possible to group packets according to attributes, configure the transmission / reception buffer with a plurality of FIFOs corresponding to the attributes of the packets, and further configure the reception buffer to correspond to the outgoing route. As a result, even if the transfer control of the packet having an arbitrary attribute is congested, it is possible to minimize the influence on the transfer control of the packet having another attribute.

Therefore, in the congestion control, there is an effect that it is possible to suppress a decrease in the throughput of the entire network, and it is extremely useful in practice.

[Brief description of drawings]

1 is a block diagram showing the principle of the present invention, FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 3 is a frame format showing an example of a "transfer stop command packet", and FIG. FIG. 5 is a block diagram showing a configuration of an embodiment of an M-FIFO, and FIG. 6 is a block diagram showing a configuration of an embodiment of a reception control unit. FIG. 7 is a block diagram showing a configuration of an embodiment of the PSW input unit, FIG. 8 is a block diagram showing a configuration of an embodiment of a transmission control unit, and FIG. 9 is a configuration of an embodiment of a transmission path sending unit. FIG. 10, FIG. 10 is a block diagram for explaining a conventional packet switching system, and FIG. 11 is a diagram for explaining a decrease in throughput due to conventional congestion control. In the figure, 101 and 103 are incoming routes, 105 and 107 are outgoing routes, 110 and 120 are receiving buffers, 130 and 140 are sending buffers, 150 is a packet switch (PSW), 160 and 170 are packet transfer restricting means, and 201 and 203.
Is an incoming route, 205,207 is an outgoing route, 210,220 is a transmission line corresponding part,
Reference numerals 211 and 221 denote reception control units, 212 and 222 denote reception M-FIFOs, 213 and
223 is a PSW input unit, 214 and 224 are transmission control units, 215 and 225 are transmission M-FIFOs, 216 and 226 are transmission line transmission units, 230 is a packet switch (PSW), 241 is "transmission line input congestion notification", and 243 is "transfer stop". Command packet, 245 is "attribute corresponding packet transmission restriction signal", 251 is "transmission path output congestion notification", 253 is "outgoing path congestion notification packet", 255 is "outgoing path / attribute compatible transfer restriction signal", 501 to 503 are FIFOs, 505 and 507 are switches, 509 is a FIFO control unit, 511 is a packet input, 513 is a packet output, and 615, 715, 815 and 915 are FIFO selection signals.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Susumu Tominaga 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Fujitsu Limited (72) Inventor Takayuki Hasebe 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Fujitsu Limited (56) Reference Literature National Institute of Electronics, Information and Communication Engineers 70th Anniversary General Conference (1987) 1797

Claims (3)

(57) [Claims] 1. A reception buffer (110, 120) connected to each incoming route (101, 103) and a transmission buffer (130, 1) connected to each outgoing route (105, 107).
40) and a packet switch (150) that performs packet exchange control between the receiving buffer (110, 120) and the transmitting buffer (130, 140), the receiving buffer (110, 120) is a packet switching system. The transmission buffer (130, 140) includes a plurality of FIFOs that form a queue corresponding to the attribute of the packet, and the transmission buffer (130, 140) includes a plurality of FIFOs that form a queue corresponding to the attribute of the packet. A packet switching system characterized by comprising packet transfer restriction means (160, 170) for restricting packet transfer. 2. A packet switching system according to claim 1, wherein the packet transfer restricting means (160, 170) is configured to restrict packet transfer of the attribute between adjacent packet switches. 3. A packet transfer restriction means (160, 170) is provided with a reception buffer (110, 12) via a packet switch (150).
The packet switching system according to claim (1), wherein the packet transfer of the outgoing route and the attribute is restricted between 0) and the transmission buffer (130, 140).