JPH07240767A - Communication adapter device - Google Patents

Abstract

PURPOSE:To reduce abolition of the frame by a frame relay network and to enable communication with high reliability by mitigating congestion. CONSTITUTION:This device has a clock control part 24 generating a clock determining the communication speed of a terminal to be provided to the terminal and enabling the change of the rate of this clock and a CPU 16 controlling a clock control part 24 so as to reduce the rate of the clock at the time of generating the congestion of a frame relay network and to increase the rate at the time of releasing the congestion. Therefore, when the congestion of the frame relay network is generated, communication speed is reduced and the congestion is mitigated, and when the congestion is released, communication speed is increased and more efficient communication can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication adapter device, and more particularly to a communication adapter device for connecting a frame relay network and a plurality of terminals.

[0002]

BACKGROUND ART Conventionally, when connecting a facsimile to a packet switching network, ITU-T (formerly CCITT: International
Telegraph and Telephone Consultative Committee: The X.25 technology of the International Telegraph and Telephone Consultative Committee was used. X.25 has become an international standard for more than 15 years, and during that period, the environment surrounding facsimile communication, especially the line quality, has been greatly improved.

Recently, Frame Relaying has appeared as a new packet switching procedure. The frame relay network considers the current line quality and simplifies the exchange process (routing by converting the logical channel in layer 2 (data link layer) and only discarding error frames (core part), and retransmitting. This is a network that realizes high-speed throughput by simplifying the protocol processing by omitting the procedure. This frame relay network is 1.5M
The purpose is to build a network with good communication efficiency such as wide area interconnection by data transmission up to bps (megabits / second) or 2 Mbps, and it is expected that it will be widely used as an alternative to a dedicated line in the future.

As the network of the frame relay network progresses, a connection terminal is required next, and naturally, the need to connect a facsimile to the frame relay network appears, and this need is expected to increase with the times. ,
It can be said that the connection of the facsimile to the frame relay network is one of the important issues in the future.

[0005]

Although it is technically possible to directly connect a facsimile to a frame relay network, the processing speed on the facsimile is 64 kbps-1.
Considering that it is about 28 kbps,
1.5 Mbps (megabits / second) or 2 Mbps of relay network
It is useless because the high data transmission rate of ps cannot be fully used. Therefore, it can be said that a connection mode in which a plurality of facsimiles can be simultaneously used via the adapter is a realistic method.

However, the layer 2 upper sublayer part and the layer 3 (network layer) on the U-plane of the frame relay and the layer 3 (network layer) need to be constructed by the user, and therefore, on the frame relay network. In order to perform facsimile communication via the adapter, it is necessary to newly define the protocol of the user-specific part or more, and the following various inconveniences occur. Frame relay networks require control when the network is congested. Present-day facsimiles do not have the concept of congestion within the communication phase. Therefore, even if congestion occurs in the network, the congestion cannot be alleviated, so that the number of discarded frames increases, the retransmission between facsimiles frequently occurs, and the communication time becomes meaningless. Frame Relay Network PVC (Permanent Virtual Circ)
uit: In a connection control method in which a fixed communication link is set when a packet switching network is joined and the link setting operation for each communication is omitted, one DLCI (Data Link Connection Ide)
ntifier: Data link connection identifier) indicates one frame relay terminal, and there is no means for connecting end-to-end the facsimile terminal connected to the adapter. Therefore, end-to-end communication between the facsimile terminals cannot be performed. Facsimile frame length and frame relay LAP
F (Link access procedure for frame mode bearer se
rvice: The protocol specified in Q.922) does not match the frame length. Therefore, if the frame length of the facsimile is longer than the frame length defined by LAPF, the frame cannot be transmitted.

The present invention has been made in view of the inconveniences of the above-described prior art, and its purpose is to reduce congestion of frames by a frame relay network to reduce the discarding of frames by a reliable communication. It is to provide a communication adapter device that enables the above.

[0008]

The invention according to claim 1 is
A communication adapter device for connecting a frame relay network and a plurality of terminals, wherein at least one of the terminals is a facsimile terminal and has a communication speed control function for controlling the communication speed of the facsimile terminal. And

According to a second aspect of the invention, in the adapter apparatus according to the first aspect, the communication speed is controlled by making the rate of the clock sent to the facsimile terminal variable.

According to a third aspect of the present invention, in the communication adapter device according to the first aspect, the forward explicit congestion notification bit, the reverse explicit congestion notification bit or the integrated link layer management message from the frame relay network is transmitted. It is characterized in that the communication speed is controlled at the timing of receiving one of them.

According to a fourth aspect of the present invention, there is provided a communication adapter device for connecting a frame relay network and a plurality of terminals,
A clock generating means for generating a clock to be provided to the terminal, a clock changing means for changing the rate of the clock, and a rate of the clock so as to decrease when congestion occurs in the frame relay network and increase when the congestion is released. Control means for controlling the clock changing means,
It is characterized by having.

According to a fifth aspect of the present invention, in the communication adapter device according to the fourth aspect, the control means controls the forward explicit congestion notification bit, the reverse explicit congestion notification bit or the integrated link layer from the frame relay network. -It is characterized by detecting the occurrence or release of congestion based on the management message.

According to a sixth aspect of the present invention, in the communication adapter device according to the fourth aspect, terminal management means for managing information regarding the plurality of terminals and information regarding a communication partner terminal connected through the frame relay network. And a congestion terminal selection means for selecting a terminal having congestion from the plurality of terminals by the terminal management means.

According to a seventh aspect of the present invention, in the communication adapter device according to the sixth aspect, the terminal management means manages at least the identification number of the accommodated terminal, the identification number of the communicating terminal, and the current communication speed. And a partner terminal identification table for managing at least the identification number of the communication partner terminal and the PVC number in the transmitted frame.

[0015]

According to the invention described in claim 1, since the communication speed control function for controlling the communication speed of the facsimile terminal is provided, the communication speed of the facsimile terminal is reduced when congestion occurs in the frame relay network. It is possible to reduce congestion.

According to the second aspect of the invention, the communication speed is controlled by making the rate of the clock sent to the facsimile terminal variable. Therefore, when the congestion occurs in the frame relay network, the clock rate is lowered to reduce the communication speed and alleviate the congestion.

According to the third aspect of the present invention, the communication speed is the timing at which the forward explicit congestion notification bit, the reverse explicit congestion notification bit or the integrated link layer management message from the frame relay network is received. Is controlled. Therefore, when congestion occurs in the frame relay network, the communication speed can be promptly reduced, and the congestion can be alleviated more reliably. In this case, even if the backward explicit congestion notification bit cannot be received, the communication speed can be promptly reduced by receiving the integrated link layer management message.

According to the fourth aspect of the invention, the control means controls the clock changing means so that the clock rate decreases when congestion occurs in the frame relay network and increases when congestion is released. Therefore, when congestion occurs in the frame relay network, the communication speed is reduced to reduce the congestion, and when the congestion is released, the communication speed is increased to enable more efficient communication.

According to the invention described in claim 5, the control means comprises a forward explicit congestion notification bit from the frame relay network,
The occurrence of congestion or the release of congestion is detected based on the backward explicit congestion notification bit or the integrated link layer management message. Therefore, when congestion occurs in the frame relay network, the communication speed can be reduced promptly and the congestion can be relieved promptly. In this case, even when the backward explicit congestion notification bit cannot be received, the occurrence of network congestion can be detected by receiving the integrated link layer management message. On the other hand, the detection of congestion release can also be detected promptly, so that more efficient communication becomes possible.

According to the sixth aspect of the present invention, the congestion terminal selection means selects the terminal in which the congestion has occurred from the plurality of terminals by the terminal management means. Therefore, it is possible to promptly and surely reduce the communication speed of the terminal that requires congestion control and restore the communication speed of the terminal from which the congestion is released.

According to the invention described in claim 7, by reading the PVC number in the frame sent from the network, it is possible to promptly determine the terminal that needs congestion control based on the accommodation terminal information table and the partner terminal identification table. Can be specified.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a communication adapter device according to an embodiment.
Ten configurations are shown schematically. This communication adapter
The device includes a main controller 12 and a system in the main controller 12.
Multiple (three in this case) existing devices connected via the bus 46
Existing interface control unit 14 ₁, 14₂, 14₃And
I am.

The main controller 12 controls the entire apparatus and controls the interface to the frame relay network. This main control unit 12 is a CP that executes control processing of the entire apparatus and an interface control program to the frame relay network.
U (Central Processing Unit) 16, ROM (Read Only Memory) 18 in which programs and data for control processing of the entire device and interface control to the frame relay network are stored, and all that should be temporarily stored A RAM (random access memory) 20 in which data (transmission / reception data and control data) is stored, and an operation unit 2 for performing key input by the operator and display for the operator
2 and the timing signals used in the existing interface are generated, and the existing interface control units 14 ₁ , 14 ₂ , 1
The data control between the clock control unit 24 to be supplied to 4 ₃ and the main control unit 12 and each existing interface control unit is performed by DM.
A high-speed DMAC (DMA controller) 26 using A (direct memory access), a bus interface (Bus IF) 28 having an interface function with a system bus, and a data link protocol defined by a frame relay protocol Controlling LAP
F control device 30 and line driver
r) 32, and.

The clock controller 24 also has a function of stepwise changing the frequency (rate) of the generated clock, and the change of the clock frequency is controlled by the CPU 16. That is, in this embodiment,
The clock control section 24 constitutes a clock generating means and a clock changing means.

The line driver 32 performs photoelectric conversion and the like when the line is an optical fiber cable.

Each of the above-mentioned constituent parts 18 to 32 includes a CPU 16
Connected to the bus via. The first to third existing interface control units 14 ₁ , 14 ₂ , 14 ₃ perform line control for each existing interface.

First existing interface controller 14 ₁
Is a CPU 34 that executes the control processing program of the existing interface control unit 14 ₁ and executes communication with the main control unit 12, and the existing interface control unit 14 ₁
The control program, a ROM36 communication program and data between the main control unit 12 is stored, the RAM38 of data to be temporarily used in the existing interface control unit 14 ₁ functions as a work area stored, to existing interface A line driver 40 including a transceiver / receiver, a communication control device 42 for executing a data link protocol or a call control sequence used in an existing interface, and a bus interface 44 having an interface function with a system bus,
Is equipped with.

Here, as the communication control device 42,
A LAPB (balanced link access procedure) controller or X.21 call control controller can be used.

This first existing interface controller 1
In the case of 4 _1, the each component 36-44 is connected to the CPU34 through a bus.

Second and third existing interface control units 1
Although not shown, 4 ₂ and 14 ₃ are also configured similarly to the _first existing interface control unit 14 ₁ .

FIG. 2 shows the configuration of a communication system in which two communication adapter devices configured as described above are connected via a frame relay network.

In this figure, FR-TA-T10 ₁ and FR-TA-R10 ₂ are the above communication adapter devices. Here, FR-TA is an abbreviation for a frame relay terminal adapter, and the following T and R indicate T on the transmitter (transceiver) side and R on the receiver (receiver) side, and actually , The transmitting side and the receiving side are not fixed, but here, the frame relay terminal adapter (hereinafter referred to as "terminal adapter") 10
_It is assumed that ₁ is the transmitting side and the terminal adapter 10 ₂ is the receiving side.

[0034] The terminal adapter 10 ₁ facsimile terminals 50A, 50B, 50C, 50D are connected, the terminal adapter 10 ₂ facsimile terminal 50E,
50F, 50G, and 50H are connected.

[0035] in the RAM20 of the main control unit 12 of the terminal adapter 10 _1, the remote terminal identification table shown in the accommodating terminal information table 52 as shown in FIG. 3 (A), FIG. (B) 54 and 54 are stored.
In the present embodiment, the accommodation terminal information table 52 and the partner terminal identification table 54 constitute terminal management means.

[0036] receiving terminal information table 52, which is connected to the terminal adapter 10 ₁ (stowed) own number is the channel number of the terminal (corresponding to telephone number), which is connected to the terminal adapter 10 ₁ terminal Indicating the state of
data and a partner terminal channel number indicating the partner station channel number with which the terminal connected to the terminal adapter 10 ₁ is currently communicating are present as data.

In the partner terminal identification table 54, the partner number, which is the channel number of the partner terminal with which the terminal connected to the terminal adapter 10 ₁ may communicate, the PVC number of the partner terminal, and the partner terminal are shown. The communication speed indicating the desired communication speed is present as data.

A similar accommodation terminal information table and a counterpart terminal identification table are also stored in the RAM ₂₀ of the main control unit 12 constituting the terminal adapter 102, but the description thereof is omitted here.

Next, a format configuration example of a frame of the frame relay transmitted by the communication system will be briefly described with reference to FIG.

The format of this frame is shown in FIG.
As shown in (A), it is based on LAPD, which is a protocol defined by Q.921. The difference from Q.921 is that a data link identifier (DLCI) for identifying a plurality of data links is provided in the address field of the frame, as shown in FIG.
This DLCI enables multiplexing of data link layer frames. This DLCI identifies the virtual connection on the bearer channel at the user-network or network interface. Therefore, the DLCI determines the data link entity that delivers the information to be sent and received, and is transferred by the data link entity.

Explaining each part in FIG. 4, F is a flag and indicates the start and end of the frame.

A is an address field, and in this example, the address field is 2 octets. EA in this address field is an address field extension bit, and when it is "0", it indicates that another octet of the address field follows, and when it is "1", it indicates the last octet of the address field. FE
CN indicates a forward explicit congestion notification bit, and BECN indicates a backward explicit congestion notification bit. FECN is set to "1" to indicate to the receiving end system that the received frame has encountered resource congestion.
BECN is set to "1" to indicate that the frame to be transmitted to the receiving end system has encountered resource congestion. The DE is a discardable display and is set to "1" to indicate that the frame is discarded with priority over other frames in the congestion state.
Also, the part with the star mark (star mark) is
Normally, the C / R (command / response) bit indicating the command requesting a specific operation to the receiving side of the frame or the response reporting the executed operation or state is stored, but it is arbitrarily used by the user. It is the part that can be done.

I is an information field, and as shown in FIG. 4B, it is composed of a terminal control code TC and a call control message or user information, and the terminal control code TC is
When TC = 0, it can be identified as a call control message, and when TC = 1, it can be identified as user information.

The FCS is a frame check sequence, which is generated and sent by the transmitting side of a frame, and is also used by the receiving side to check whether the frame has an error such as a transmission error. When an error is found, the frame receiving side discards the frame. The error detection code used in the FCS includes an error of 3 bits or less in a frame, an error of all odd number of bits, an error of 16 consecutive bits or less, and most other random and continuous bit errors. Can be detected.

Next, the terminal adapter 10 ₁ on the transmitting side
Alternatively, the main controller 12 of the terminal adapter 10 ₂ on the receiving side
Congestion control will be described with reference to the flowchart of FIG. 5 showing the main control algorithm of the inner CPU 16.

In step 100, it is determined whether congestion has been detected. This congestion is detected by the FECN in the LAPF frame sent from the frame relay network on the receiving side.
This is performed depending on whether (forward explicit congestion notification bit) has changed from "0" to "1", that is, whether FECN has been notified. On the transmitting side, in the LAPF frame sent from the frame relay network. Whether or not the BECN (reverse explicit congestion notification bit) of F has changed from "0" to "1", that is, F
CLLM (consolidated link layer manage), which is a frame generated by a switch in which congestion is occurring in the frame relay network, whether or not ECN or BECN is notified
ment: Integrated link layer management) This is performed depending on whether or not a message has been notified (see FIG. 2). This C
The LLM message is transmitted using the LAPF XID frame. According to this CLLM message, FE
Unlike CN / BECN, not only the occurrence of congestion,
The terminal side can also be notified of the degree of congestion, facility, or device failure.

If it is determined that congestion is detected, the PVC number (address information) is read from the address field of the LAPF frame in step 102, and then the congestion terminal selection and speed reduction subroutine is executed in step 104. Transition. In this case, when congestion is detected by the CLLM message, the PVC status is confirmed instead of reading the PVC number.

In this subroutine for selecting a congested terminal and reducing the speed, as shown in FIG.
Then, the pointer is set in the partner terminal identification table 54, the process proceeds to step 204, and P is read from the partner terminal identification table 54.
Read out the VC number.

At the next step 206, it is judged whether or not the PVC number read at step 204 and the PVC number read at step 102 match. If they do not match, the routine proceeds to step 222. It is determined whether reading of all PVC numbers from the partner terminal identification table 54 has been completed. If all the PVC numbers have been read from the partner terminal identification table 54, the process returns to step 100 of the main routine.

On the other hand, if all the PVC numbers have not been read from the partner terminal identification table 54 in step 222, the process proceeds to step 224 and the pointer of the partner terminal identification table 54 is set next, and then step Return to 204.

If the PVC numbers match in step 206, the process proceeds to step 208 to read the partner number from the partner terminal identification table 54, and step 21
The process proceeds to 0 to read the partner terminal channel number registered in the accommodated terminal information table 52.

It is judged whether or not the partner number read in the next step 212 and the partner terminal channel number match,
If this determination is denied, the process moves to step 224. On the other hand, if the determination in step 212 is affirmative, congestion has occurred with the other terminal currently in communication, so the process proceeds to step 214 and the corresponding own station number and current communication from the accommodated terminal information table 52. The speed is read, and the process proceeds to step 216 and the communication speed x 7/8 (this value is a predetermined value and may be a fixed value or a variable value).
Then, the new communication speed calculated in step 218 is written in the current communication speed of the accommodation terminal information table 52.

At the next step 220, after changing (decreasing) the clock rate for the terminal of the own station number read at step 214 so as to become the current communication speed, the routine proceeds to step 224.

After that, the process returns to step 206, and the above-mentioned process determination is repeated. However, if the determination in step 212 is always denied and the determination in step 222 is affirmed, the process returns to step 100 of the main routine.

On the other hand, if the determination at step 100 is negative, the routine proceeds to step 106, at which it is determined whether the congestion release is detected. The detection of the congestion release is made by a determination opposite to the above-mentioned detection of the congestion. That is, on the receiving side, the LAPF sent from the frame relay network
FECN in frame (forward explicit congestion notification bit)
Is changed from "1" to "0", that is, whether the FECN notification is stopped or not.
It is performed depending on whether N (reverse explicit congestion notification bit) is changed from “1” to “0”, that is, whether the BECN notification is stopped, or whether the CLLM message notification is stopped. .

If the release of congestion is not detected, the process returns to step 100. If the release of congestion is detected, the PVC number (address information) is read from the address field of the LAPF frame in step 108. After that, the process proceeds to step 110, which is a subroutine for selecting a congestion terminal and increasing the speed. In this case, CLLM
When decongestion is detected by stopping the message,
Instead of reading the PVC number, a PVC status check is performed.

In the subroutine for selecting a congestion terminal and increasing the speed, as shown in FIG.
Then, the pointer is set in the partner terminal identification table 54, and the process proceeds to step 304, where P is read from the partner terminal identification table 54.
Read out the VC number.

At the next step 306, it is judged whether or not the PVC number read at step 304 and the PVC number read at step 108 match. If they do not match, the process proceeds to step 322. It is determined whether reading of all PVC numbers from the partner terminal identification table 54 has been completed. If all the PVC numbers have been read from the partner terminal identification table 54, the process returns to step 100 of the main routine.

On the other hand, if all the PVC numbers have not been read from the partner terminal identification table 54 in step 322, the process proceeds to step 324 and the pointer of the partner terminal identification table 54 is set next, and then step Return to 304.

When the PVC numbers match in step 306, the process proceeds to step 308, the partner number is read from the partner terminal identification table 54, and step 31
At 0, the partner terminal channel number registered in the accommodated terminal information table 52 is read.

It is determined whether or not the partner number read in the next step 312 and the partner terminal channel number match,
If this determination is denied, the process moves to step 324. On the other hand, if the determination in step 312 is affirmative, the congestion state that has occurred with the other terminal currently communicating is released, and therefore the process proceeds to step 314 and the corresponding own station number is found from the accommodation terminal information table 52. And the current communication speed are read, and the process proceeds to step 316 and the communication speed x 8
/ 7 (this value is a predetermined value and may be a fixed value or a variable value), and the procedure proceeds to step 318, where the calculated new communication speed is the current communication speed of the accommodation terminal information table 52. Write in

At the next step 320, the clock rate for the terminal having the own station number read at step 314 is changed (increased) so as to become the current communication speed, and then the process proceeds to step 324.

In this case, as indicated by the route of the dotted line, when the determination in step 312 is affirmative, the process proceeds to step 315 and the accommodation terminal information table 5 is entered.
After reading the corresponding own station number and communication speed initial value from 2, the process proceeds to step 318 and the read communication speed initial value may be written in the current communication speed of the accommodation terminal information table 52. In such a case, in step 320, the clock rate is changed so that the initial communication speed (desired communication speed with the partner terminal) is returned at once.

Thereafter, the process returns to step 304 to repeat the above-described process determination, but the determination in step 312 is always denied, and when the determination in step 322 is affirmed, the process returns to step 100 of the main routine.

Next, referring to FIG. 3, PVC number 10
The processing of the terminal adapter 10 ₁ (or 10 ₂ ) when congestion is occurring in the 0 terminal will be specifically described.

When detecting congestion, the CPU 16 in the main control unit 12 takes out address information from the address field of LAPF (step 102 above).

Based on the retrieved address information (PVC number), the terminal in which congestion has occurred is determined from the partner terminal identification table 54 and the accommodation terminal information table 52. Specifically, steps 202 → 204 → 206 → 222 → 22
The determination of step 206 is affirmed during the repetition of 4 → 204 → 206, and then steps 208 → 210 → 212.
When the judgment in step 212 is positive,
At that time, when the determination in step 212 is denied, steps 212 → 224 → 204 → 206 → 208 → 21
When the determination in step 212 is affirmed during the repetition of 0 → 212, the determination of the partner terminal in which the congestion has occurred is completed.

In this case, according to the partner terminal identification table 54, the partner number of the terminal whose PVC is 100 is 0001 and 0015.
Is. The terminal number of 0015 is registered in the partner terminal channel number of the accommodated terminal information table 52, and thus it is possible to determine that either the partner terminal of 0015 or the own station (accommodating terminal) is in communication. From the accommodated terminal information table 52, it can be seen that the terminal for which congestion control is required is the own station number 0555 which is in communication with the partner terminal of 0015.

Therefore, the own station number 0555 of the terminal requiring the congestion control and the current communication speed (64K) of this terminal are read from the accommodation terminal information table 52 (step 214), and a clock of 64K is predetermined. The rate is lowered based on the obtained value (information), and this information is written in the accommodation terminal information table 52 (steps 216 and 218).

As a result, 64K × 7/8 (predetermined value) = 56K is written in the accommodating terminal information table 52, and CP is adjusted so that the clock rate is reduced to 7/8.
The clock control unit 24 is controlled by U16, the communication speed of the terminal with the own station number 0555 is reduced to 56 K (kbs), and the congestion is relieved.

On the other hand, when the main controller 12 detects that the congestion has been released, it extracts the address information from the address field of the LAPF (step 10 above).
8).

Based on the fetched address information (PVC number), the terminal whose congestion has been released is determined from the partner terminal identification table 54 and the accommodation terminal information table 52 by the same procedure as described above, and the clock of the terminal whose congestion has been released Is increased based on a predetermined value (information), and the communication speed of the terminal from which the congestion is released is increased by a predetermined ratio (steps 314 → 316 → 318 → 320). In this case, after determining the terminal from which the congestion is released, the communication speed may be returned to the desired communication speed with the partner terminal at once (steps 315 → 318 → 320).

As is apparent from the above description, in this embodiment, the CPU 16 in the main controller 12 controls the control means,
Congested terminal selection means is configured.

In the above embodiment, the case where all the terminals are facsimile terminals is illustrated, but the communication adapter device of the present invention can accommodate other terminals such as digital telephones, personal computers, data terminals and video terminals. Of course.

[0075]

As described above, according to the communication adapter device of the present invention, the congestion can be alleviated by controlling the communication speed, thereby reducing the discarding of frames by the frame relay network. It has an unprecedented excellent effect of enabling highly reliable communication.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a communication adapter device according to an embodiment.

2 is an explanatory diagram showing a schematic configuration of a communication system including two communication adapter devices of FIG. 1. FIG.

FIG. 3A is a diagram showing an example of a housed terminal information table, and FIG. 3B is a diagram showing an example of a partner terminal identification table.

4 is a diagram showing an example of a frame format configuration of a frame relay transmitted by the communication system of FIG.

FIG. 5 is a flowchart showing a main control algorithm of a CPU in a main control unit of a communication adapter device (terminal adapter).

FIG. 6 is a flowchart showing a subroutine for selecting a congested terminal and speed reduction in FIG.

FIG. 7 is a flowchart showing a subroutine for selecting a congestion terminal and increasing the speed in FIG.

[Explanation of symbols]

10 communication adapter device 16 CPU (control means, congestion terminal selecting means) 24 clock control unit (clock generating means, clock changing means) 50A to 50H facsimile terminal 52 accommodating terminal information table 54 partner terminal identification table

Claims (7)

[Claims] 1. A communication adapter device for connecting a frame relay network and a plurality of terminals, wherein at least one of the terminals is a facsimile terminal and a communication speed control function for controlling the communication speed of the facsimile terminal is provided. A communication adapter device having. 2. The adapter device according to claim 1, wherein the communication speed is controlled by changing a rate of a clock that determines the communication speed of the facsimile terminal to be sent to the facsimile terminal. 3. The control of the communication speed is performed at a timing when any one of a forward explicit congestion notification bit, a reverse explicit congestion notification bit, and an integrated link layer management message from the frame relay network is received. The communication adapter device according to claim 1, which is characterized. 4. A communication adapter device for connecting a frame relay network and a plurality of terminals, the clock generation means generating a clock for determining a communication speed of the terminal, which is provided to the terminal, and changing the rate of the clock. And a control means for controlling the clock changing means so that the clock rate decreases when congestion occurs in the frame relay network and increases when congestion is released in the frame relay network. Adapter device. 5. The control means detects occurrence of congestion or release of congestion based on a forward explicit congestion notification bit, a reverse explicit congestion notification bit, or an integrated link layer management message from the frame relay network. The communication adapter device according to claim 4, wherein 6. A terminal management unit that manages information about the plurality of terminals and information about a communication partner terminal connected via the frame relay network, and the terminal management unit causes congestion from the plurality of terminals. The communication adapter device according to claim 4, further comprising: a congestion terminal selection unit that selects a terminal. 7. An accommodating terminal information table for managing at least the identification number of the accommodating terminal, the identification number of the communicating partner terminal, and the current communication speed by the terminal managing means, and the communicating party terminal identification number and transmission. 7. The communication adapter device according to claim 6, further comprising a partner terminal identification table for managing at least the PVC number in the frame to be transmitted.