JP2561033B2 - Packet relay system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay system that connects different networks and enables data packets to be transferred between networks, and more particularly to a packet relay system for transmitting and receiving data packets via a public network. Regarding

[0002]

2. Description of the Related Art In recent years, with the rapid spread of LANs (local area networks), it has become necessary to connect a plurality of LANs or a wide area network (wide area network). For example, geographically distant LANs may be connected to each other via a public packet network for electronic mail or file transfer. A router, which is one of such connection devices, is a device that connects LANs via a wide area network, analyzes the header of the received data and performs routing, and transfers the data to the destination LAN via the wide area network. To do.

The packet relay system in such a router is configured to disconnect the line after a lapse of a predetermined time when the packet data transmitted from the LAN to the public network ends. That is, the system is provided with a timer set in advance, the timer is started when the transmission of the packet data is completed, and the line is disconnected by the signal output from the timer when the predetermined time has elapsed. The set time of this timer is a fixed value, and is set to an appropriate value by the user when the system is constructed.

[0004]

However, in the conventional packet relay system, since the timer set value is fixed, the timer is set so that the public line is not cut off during the course of any work. The set value is preset to a relatively large value. For example, in the case of a conversational application in which the upper layer protocol is the remote terminal protocol (TELNET) and a packet is transmitted every time the operator hits a key, the timer setting value is set so that the line is not disconnected during the work. It needs to be set large. Further, in the case of a continuous processing type application based on the file transfer protocol (FTP), a short timer setting value is sufficient. Therefore, in the conventional system in which the timer setting value is fixed, the timer setting value is set large in accordance with the protocol such as TELNET.

For this reason, when the upper application is a file transfer protocol for performing high-speed transfer, there arises a problem that the public line remains connected for a long time despite the end of transmission. As a result, the effective use of the public line is hindered, and the line fee is wasted from the user's point of view.

An object of the present invention is to provide a packet relay system in a router that can promote effective use of public lines and save line usage charges.

[0007]

A packet relay system according to the present invention has a routing function for transmitting a data packet between a first network and a second network, and a protocol terminated by the packet relay system. Memory means for storing in advance a time setting value corresponding to the type of a higher protocol, and a time setting value corresponding to the higher protocol of a transmission packet transmitted from the first network to the second network by referring to the memory means. From the time set value, a transmission end detection means for detecting the end of transmission of a transmission packet, and an end signal when the time set value selected by the selection means is activated and the end signal is reached. A clocking means for generating and a line control means for disconnecting the line of the second network according to the end signal Characterized in that it consists of.

[0008]

The timing of disconnecting the line of the second network is set according to the upper protocol of the transmission packet. A time setting value representing the disconnection timing corresponding to the type of the upper protocol is stored in advance in the memory means, and the time setting value corresponding to the upper protocol of the transmission packet is selected. Subsequently, when the end of transmission of the transmission packet is detected, the time measuring means is activated, and when the selected time set value is reached, the time measuring means generates an end signal. With this end signal, the line control means disconnects the line of the second network.

More specifically, when transmitting a data packet between a LAN and a public network, a public line is connected at the time when packet data is transmitted to or received from the destination via the public network, A timer (timer) is started when transmission / reception is completed. If packet transmission / reception occurs before this timer reaches the time set value, the operation of the timer is stopped, and when the timer reaches the set value, the public line is disconnected.

Preferably, the timer setting value is stored in the memory in a table format corresponding to the type of upper layer protocol. For example, if the application is a file transfer protocol that performs high-speed transfer, reduce the timer setting value to disconnect the line in a short time, and if the application is a remote terminal protocol, set it to a large value and set the line Disconnect.

TCP / IP (Transmission Control Protocol / Internet Protocol)
In the packet based on the specification, the type of higher-layer protocol is identified by the source port number (source port address) of the packet. A table storing the source port number and the timer setting value corresponding to the source port number is prepared, the table is referred to by using the source port number of the transmission packet, and the corresponding timer setting value is extracted. And
When the packet transmission / reception is completed, the timer is operated according to the extracted timer setting value, and the public line is disconnected when the setting value is reached.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a packet relay system according to the present invention. The packet in this embodiment is based on the TCP / IP specifications.

First, when a transmission packet is input from the LAN, the routing processing unit 101 determines the destination, and if it is to be transmitted to the public line, transfers it to the data circuit terminating device (DCE) 109 and transmits from there. The packet is sent to the public line. On the contrary, the packet received from the public line is demodulated by the DCE 109, transferred to the routing processing unit 101, the destination is determined, and sent to the LAN.

The transmission packet output from the routing processing unit 101 is input, and the port number extraction unit 102 receives the T packet.
Source port number of CP header is extracted and table 103
Output to. The table 103 outputs the timer setting value corresponding to the source port number to the register 104, and the register 104 holds the timer setting value. The table 103 will be described later (see FIG. 9).

From the routing processing unit 101 to the DCE 10
Both the transmission packet output to 9 and the reception packet input from the DCE 109 are the packet end detection unit 10.
5 and the packet start detection unit 106. The packet end detection unit 105 detects the time when the transmission and reception packets have ended, and outputs a start signal to the timer 108. The start signal causes the timer 108 to start a time counting operation. The packet start detection unit 106 detects the time when the packet starts to be transmitted or received, and outputs a pulse signal to the timer 108 and the DCE 109. Timer 108
Input this pulse signal as a timer stop signal to stop the time counting operation and return to the initial state. At the same time, D
The CE 109 inputs a pulse signal as a connection signal, connects a public line, and sends a transmission packet to the line.

The exclusive OR circuit 107 includes a timer 108.
Of the timer and the timer set value stored in the register 104 are compared with each other, and when they match each other, a pulse signal is output to the timer 108 and the DCE 109. The timer 108
This pulse signal is input as a stop signal to stop the time counting operation. The DCE 109 inputs this pulse signal as a disconnection signal and disconnects the public line.

FIG. 2 is a detailed block diagram of the routing processing unit 101 in this embodiment. LAN is LAN
The DCE 109 is connected to the interface 1010, and the DCE 109 is connected to the line interface 1011. When a packet is input, these interfaces 1010 and 1011 interrupt a CPU (central processing unit) 1012 that performs routing control. CPU 101
2 refers to the routing table stored in the memory 1013, and performs communication control for the LAN interface 1010 or the line interface 1011.

FIG. 3A shows a LAN interface 101.
0 is the packet format, and FIG. 3B is the packet format in the line interface 1011. In each packet, the destination address exists in the IP header part. FIG. 3C is a routing table in which output ports corresponding to destination addresses are defined. The operation of the routing processing unit 101 will be described in more detail.

FIG. 4 is a flow chart showing the control of the routing processing unit 101. In the figure, CPU1
When an interrupt request is issued, 012 determines which of the LAN and the line is the interrupt request (401). If the request is from the line, the packet is input from the line interface 1011 and stored in the memory 1013 (40).
2). If it is from the LAN, the packet is input from the LAN interface 1010 and stored in the memory 1013 (403).

Next, the routing table is searched using the destination address of the IP header (404), and if there is a matching destination address (Yes in 405), it is determined which output port corresponds to it ( 40
6). On the line side, the packet is transferred from the memory 1013 to the line interface 1011 (407), and a transmission instruction is output to the line interface 1011 (408). On the LAN side, the memory 1013
Packet is transferred from the LAN interface 1010 to the LAN interface 1010 (409), and a transmission instruction is output to the LAN interface 1010 (410).

The transmission packet output from the line interface 1011 of the routing processing unit 101 is input to the port number extraction unit 102 and the source port number is extracted. As shown in FIG. 5, in the TCP head of the packet, the first two octets are the source port number field 5
01.

FIG. 6 is a detailed block diagram of the port number extraction unit 102 in this embodiment. The data of the transmission packet is converted to 8 by the serial / parallel converter 1021.
It becomes parallel data of bits, and the first two octets are stored in the registers 1022 and 1023, respectively, and output as the source port number. When the transmission packet is input, it is detected by the HDLC header detector 1024, and the up counter 1025 is reset. The up counter 1025 operates by a clock obtained by dividing the input clock by 1/8,
The output data of the serial / parallel converter 1021 is stored in the register 1026 in accordance with the output of. The lower 4 bits of the data stored in the register 1026 are masked with 0, and further downshifted by 2 bits to the down counter 1
It is set to 027. In accordance with the output of the down counter 1027, the registers 1022 and 1023 store the parallel data, and output a 16-bit source port number that is a total of 8 bits.

FIG. 7 is a detailed block diagram of the packet end detection unit 105 in this embodiment. In the figure,
The HDLC flag pattern detectors 1051 and 1052 allow the flag patterns of the transmission and reception packets to be “01”.
When 111110 'is detected, the detection result' 1 'is stored in the registers 1053 and 1054, respectively. When the detection results stored in the registers 1053 and 1054 are both “1”, it means that no packet is input after the end flag of the HDLC frame is detected for both transmission and reception. Therefore, when the input of the packet is completed, "1" is output from the AND gate 1055 to the timer 108 and the timer 108 is started.

FIG. 8 is a detailed block diagram of the packet start detector 106 in this embodiment. In the figure,
When the HDLC headers of the transmitted and received packets are detected by the HDLC header detectors 1061 and 1062,
The detection result “1” is stored in the registers 1063 and 1064. Registers 1063 and 1064
If any of the detection results stored in 1 is “1”, it indicates that a transmission or reception packet has been input. Therefore, when the packet input is started, the OR gate 1065
"1" is output from this, and as described above, this stops the timer 108 and the DCE 109 connects the public line.

FIG. 9 is a table 103 in this embodiment.
FIG. 3 is a schematic diagram showing an example of correspondence between a source port number and a timer set value stored in FIG. The table 103 is provided with a port number field and a timer setting value field. In this embodiment, the port number is "1" when the upper protocol is the file transfer protocol (FTP).
It is set to 0'and the timer setting value in that case is set to 10 seconds. Also, the remote terminal protocol (TELNET)
In this case, the port number is set to '23', and the timer setting value in that case is set to 600 seconds.

In the case of an FTP continuous processing application, the line is disconnected immediately after the end of the packet to prevent wasteful occupation of the line and save the line usage fee. On the other hand, in the case of a conversational application by TELNET, the next packet is likely to be transmitted even if the end of the packet is detected, so the timer setting value is set long so that the line is not disconnected during the operation. Therefore, the table 103 selects the timer setting value suitable for the application using the source port number of the transmission packet extracted by the port number extraction unit 102.

In the case of the FTP application, the timer 108 continues the time counting operation for 10 seconds after the packet end detection unit 105 detects the packet end. Then, at the time when 10 seconds have passed, the disconnection signal from the EOR 107 is DCE1 because the measured value and the timer setting value match.
09, and the line is disconnected.

On the other hand, in the case of the TELNET application, the timer 108 continues the time counting operation for 600 seconds after the end of the packet is detected. Then, at the time when 600 seconds have passed, the measured value and the timer set value match, and DCE1
A disconnection signal is output to 09.

[0030]

As described in detail above, the packet relay system according to the present invention selects the line holding time according to the type of the upper application of the packet.
In a continuous processing application such as FTP, by disconnecting the line immediately after the end of the packet, it is possible to prevent unnecessary occupation of the line and save the line usage fee. Also, TELN
In an interactive application such as ET, the line holding time can be set to be long to prevent disconnection of the line during operation, thus improving operability.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a packet relay system according to the present invention.

FIG. 2 is a detailed block diagram of a routing processing unit 101 in this embodiment.

3A is a diagram showing a packet format in a LAN interface 1010, FIG. 3B is a diagram showing a packet format in a line interface 1011, FIG.
(C) is a schematic diagram showing a routing table in which an output port corresponding to a destination address is defined.

FIG. 4 is a flowchart showing control of a routing processing unit 101.

FIG. 5 is a schematic diagram showing a format of a TCP header.

FIG. 6 is a detailed block diagram of a port number extraction unit 102 in this embodiment.

FIG. 7 is a detailed block diagram of a packet end detection unit 105 in this embodiment.

FIG. 8 is a detailed block diagram of a packet start detection unit 106 in this embodiment.

FIG. 9 is a schematic diagram showing an example of correspondence between a source port number and a timer setting value stored in a table 103 in this embodiment.

[Explanation of symbols]

 101 routing processing unit 102 port number extraction unit 103 table 104 register 105 packet end detection unit 106 packet start detection unit 107 exclusive OR circuit 108 timer 109 data line termination device

Claims (8)

(57) [Claims] 1. A packet relay system having a routing function for transmitting a data packet between a first network and a second network, the time corresponding to a protocol type higher than a protocol terminated by the packet relay system. Memory means for storing set values in advance, and a second network from the first network by referring to the memory means.
The selecting means for selecting a time setting value corresponding to the upper protocol of the transmission packet transmitted to the network from the time setting value, the transmission end detecting means for detecting the transmission end of the transmission packet, and the detected transmission end And a line control unit for activating and terminating the line of the second network according to the end signal when the time setting value selected by the selecting unit is reached. Packet relay system. 2. A transmission start detecting means for detecting the start of transmission of a data packet between the first network and the second network, wherein when the transmission start is detected, the time measuring means stops the time counting operation. The packet relay system according to claim 1, wherein the line control means connects a line of the second network. 3. The data packet is TCP / IP
The packet relay system according to claim 1 or 2, which is based on (Transmission Control Protocol / Internet Protocol) specifications. 4. The memory means inputs a source port number of a packet and outputs a time setting value corresponding thereto, and the time setting means detects a source port number of the transmitted packet. 4. The packet relay system according to claim 3, further comprising: means for setting a time setting value output from the memory means according to the source port number. 5. A local area network (LAN)
In a packet relay system consisting of a routing processor and a data circuit terminating device for transmitting a data packet between a public network and a public network, by specifying the type of protocol higher than the protocol terminated by the routing processor, Memory means for outputting a corresponding time set value, protocol detection means for detecting the type of upper-layer protocol of a transmission packet transmitted from the LAN to the public network, and transmission end detection means for detecting the end of transmission of the transmission packet And, when the detected transmission end, starts a time counting operation, and outputs a public line disconnection signal to the data line termination device when the time set value corresponding to the detected upper protocol and the time measured value match. A packet relay system comprising: a clocking means. 6. A transmission start detection means for detecting transmission start of a data packet between the LAN and the public network, wherein the detected transmission start stops the timing operation of the clock means. 6. The packet relay system according to claim 5, wherein the data line terminating device connects the line of the public network. 7. The data packet is TCP / IP
7. The packet relay system according to claim 5, which is based on (Transmission Control Protocol / Internet Protocol) specifications. 8. The memory means inputs a packet source port number and outputs a time setting value corresponding to the packet source port number, and the protocol detecting means detects a source port number of the transmitted packet. The timer means includes a set value memory means for storing the time set value output from the memory means in accordance with the source port number, a timer for outputting a timer value in accordance with a predetermined clock, the timer value and the 8. The packet relay system according to claim 7, further comprising: a comparator circuit that outputs the public line disconnection signal and initializes the timer when the set time values match.