JPH10257079A - Node device, communication system packet transmission control method and packet transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evade the decline of transfer quality received by a packet to be transmitted by performing the pseudo transmission of signals for indicating that the collision of transmission packets is generated to a communication network at the time of judging that the packet to be transmitted belongs to a packet flow to be provided with predetermined transfer quality and the transfer quality can not be satisfied by performing transmission standby. SOLUTION: An IP(internet protocol) packet identification part 61 identifies a flow or the like to which an IP packet to be transmitted belongs and a transmission medium monitoring part 64 monitors the state of a transmission medium and turns a frame transmission part 63 to the transmission standby when other frames are during the transmission. An IP packet schedule part 67 predicts the transfer quality of the IP packet belonging to the flow for requesting the transfer quality and transmits pseudo Jam signals through a Jam signal transmission part 66 at the time of judging that requested quality is not satisfied. The transmission of the other packets during transfer on the transmission medium is stopped and the transfer of the IP packet of the transfer quality for satisfying the request is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a node device connected to a communication network such as Ethernet using the CSMA / CD system, a communication system including the communication network and a plurality of node devices, and packet transmission of the node device. The present invention relates to a control method and a packet transmission method.

[0002]

2. Description of the Related Art Ethernet is one of communication networks for realizing communication between computers. In Ethernet,
Provide communication between a plurality of communication nodes. Here, the communication node means, for example, a terminal or a router. The basic rules of Ethernet are defined in IEEE standard 802.3.

In the Ethernet, communication at one time on the same transmission path is limited to a set of communication nodes. That is, communication between two or more communication nodes is not provided at the same time. This is because the same transmission path is used for communication between each set of communication nodes, and therefore, collision of communication information occurs on the transmission path.

[0004] In order to avoid collision of communication information on such a transmission path, CSMA is used in communication over Ethernet.
/ CD (Carrier Sense Multipl
eAccess with Collision De
A control method called “section” is used. The CSMA / CD method is to check the status such as whether or not a transmission line is currently used before each communication node transmits communication information, and to transmit the communication information only when the transmission line is free. This is the method of starting.

In this method, if the transmission path is in use, the same procedure as above is tried again after a predetermined waiting time has elapsed. A communication node that detects collision of communication information during transmission calculates a waiting time (retransmission interval) before attempting retransmission based on the following equation. (Retransmission interval) = (slot time) × n where the positive number n is randomly selected from the following range: 0 ≦ n <2 ^k [k = min (m, 10), m: number of collisions] The slot time represents the time required for transmitting a packet of the minimum size. When the number of collisions (m) reaches 10, the upper limit of the range of n is saturated. If the number of collisions (m) exceeds 16, a transmission error is determined.

[0006] By using the CSMA / CD system, the collision probability of communication information transmitted from different communication nodes can be reduced. By the way, in recent years, IET
F (Internet Engineering Ta)
SK Force), IP (Internet)
(Protocol) At the time of delivery of a packet, discussions are being made to provide a predetermined transfer quality. In conventional IP packet transfer, Best Ef
Only a delivery service, called fort, is provided, in which the best effort is made on the delivery of packets on the Internet, but without any guarantees on the resulting quality.

On the other hand, IETF provides a packet delivery service that guarantees the provision of a predetermined target quality, such as a guaranteed service that guarantees a delay required for packet delivery (a packet transfer rate requested by a user). Proposals and resource reservation protocols (for example, RSVP (Resource ReSe)
rVation Protocol)) has been proposed.

[0008] For example, when considering the provision of the above Guaranteed service on the Internet configured via Ethernet, when the load on Ethernet is light, the possibility of collision of communication information is very small. Therefore, it is considered that sufficient transfer quality can be provided to the user.

[0009] However, when the load on the Ethernet is heavy, the possibility of collision of communication information is considered to be very large, so the number of retransmissions of the communication information increases, and as a result, the number of packets requesting the service becomes larger. The delay value required for delivery does not satisfy the required quality determined in advance.

When a communication node that monitors whether or not the communication network is in an emergency state determines that the communication network is in an emergency state, it notifies other communication nodes on the same communication network of the communication node. A transmission method for preferentially transmitting an emergency packet generated for the purpose on the communication network is described in, for example, JP-A-5-300153 (urgent packet transmission method). In the statement,
It is intended for an IP packet transmission control method that should guarantee the provision of target quality.

[0011]

As described above, in the conventional Ethernet communication method, the collision of communication information and the detection of the collision after the collision is detected irrespective of the contents of the transfer quality to be provided for the upper-level IP packet. The retransmission interval is calculated and the retransmission is attempted. As a result, even if the IP packet delivery for which the packet transfer delay value is to be guaranteed, a plurality of collisions in the communication information cause excessive transfer delay. Is added, and there is a possibility that the required quality determined in advance cannot be satisfied. In addition, this point is not limited to the exemplified Ethernet, and the CSM
A similar problem occurs in a communication network using the A / CD system.

The present invention has been made in view of the above circumstances, and depends on the use status of a communication network when delivering a packet requiring strict quality via a communication network using the CSMA / CD system. It is an object of the present invention to provide a node device, a communication system, a packet transmission control method, and a packet transmission method that can significantly reduce a packet transmission waiting time at a communication node, which increases, thereby avoiding a decrease in transfer quality of a packet.

[0013]

Means for Solving the Problems The present invention (claim 1) provides:
CSMA / CD (Carrier Sense Mul
single Access with Collisi
A node device (for example, a terminal or a router) connected to a communication network (for example, Ethernet) using an on-detection method and transmitting a packet, and before starting transmission of a packet to the communication network, Detecting means for detecting whether the communication network is in use, and detecting that the communication network is in use by the detection means, and providing the packet to be transmitted with a predetermined transfer quality. If the packet belongs to a packet flow to be transmitted, and if it is determined that waiting for transmission of the packet causes the transfer quality expected to be incurred by the packet to not satisfy the predetermined transfer quality, the communication Signal transmission means for artificially transmitting a signal (for example, a Jam signal) indicating that a collision of a transmission packet has occurred on the network. It is characterized by the following.

The present invention (claim 2) provides a CSMA / CD
(Carrier Sense Multiple A
access with Collision Dete
and a plurality of node devices (for example, terminals and routers) connected to the communication network and transmitting and receiving packets, the plurality of nodes being connected to the communication network. At least one of the devices, prior to starting transmission of a packet to the communication network, detecting means for detecting whether the communication network is in use by another communication node, and performing the communication by the detecting means. If the packet is detected as being in use by the network and the packet to be transmitted belongs to a packet flow for which a predetermined transfer quality is to be provided, the packet is queued for transmission. If it is determined that the transfer quality expected to suffer from the communication quality does not satisfy the agreed upon transfer quality, the communication network is forcibly forced. A signal transmitting means for pseudo-transmitting a signal (for example, a Jam signal) indicating that a collision of a transmission packet has occurred in the communication network in order to make the communication network unused, After a lapse of a predetermined time from the detection in the case where it is detected that it has not been detected, or after a lapse of a predetermined time since the signal was transmitted by the signal transmission unit when the signal was transmitted,
And control means for starting transmission of the packet.

The present invention (claim 3) provides a CSMA / CD
(Carrier Sense Multiple A
access with Collision Dete
ction) system (eg, terminal, router) connected to a communication network (eg, Ethernet) using the method
Is a packet transmission control method for acquiring a right to use the communication network when transmitting a packet for which the transfer quality is to be guaranteed, wherein the node device transmits a packet to the communication network prior to starting transmission of the packet to the communication network. Detecting whether or not the communication network is in use, and determining that the communication network is in use by the detection, and the packet to be transmitted is transmitted to a packet flow to be provided with a predetermined transfer quality. If it is determined that the transmission quality of the packet does not satisfy the determined transmission quality by waiting for transmission of the packet, the packet transmitted to the communication network. A signal indicating that a collision has occurred (for example, a Jam signal) is simulated to force the communication network to be unused. The features.

The present invention (Claim 4) provides a CSMA / CD
(Carrier Sense Multiple A
access with Collision Dete
ction) system (eg, terminal, router) connected to a communication network (eg, Ethernet) using the method
Is a packet transmission method for transmitting a packet whose transfer quality is to be guaranteed, wherein the node device transmits a packet belonging to a packet flow to which a predetermined transfer quality is to be provided to the communication network. Detecting whether or not the communication network is being used by another communication node, and when it is determined that the communication network is not being used by this detection, starts transmission of the packet after a predetermined time has elapsed, If it is determined by the detection that the communication network is in use, it is determined that the transfer quality expected to be incurred by the packet does not satisfy the predetermined transfer quality by waiting for transmission of the packet. If so, a signal indicating that a collision of outgoing packets has occurred in the communication network in order to forcibly put the communication network into an unused state (for example, , By sending a Jam signal) artificially, and starts transmission of the packet after a predetermined time,
In other cases, the procedure from the detection is performed again after a predetermined time has elapsed.

The present invention (Claim 5) provides a CSMA / CD
(Carrier Sense Multiple A
access with Collision Dete
a node device (for example, a terminal or a router) connected to a communication network (for example, Ethernet) using a method, and transmitting a packet to the communication network before starting transmission of the packet to the communication network. Detecting means for detecting whether or not the communication network is in use by another communication node; and detecting that the communication network is in use by the detection means, and the packet to be transmitted has a predetermined transfer quality. If the packet belongs to the packet flow to be provided, it is determined that the transfer quality expected to be incurred by the packet by waiting for transmission of the packet does not satisfy the determined transfer quality, And if it is determined that the use of the communication network by the other communication node does not end within a predetermined time, the communication network is forcibly disconnected. Use by the network in order to state no signal indicating a collision of transmitted packets has occurred (e.g., Jam signal), characterized in that a signal sending means for sending the artificially.

The present invention (Claim 6) provides a CSMA / CD
(Carrier Sense Multiple A
access with Collision Dete
and a plurality of node devices (for example, terminals and routers) connected to the communication network and transmitting and receiving packets, the plurality of nodes being connected to the communication network. At least one of the devices, prior to starting transmission of a packet to the communication network, detecting means for detecting whether the communication network is in use by another communication node, and performing the communication by the detecting means. If the packet is detected as being in use by the network and the packet to be transmitted belongs to a packet flow for which a predetermined transfer quality is to be provided, the packet is queued for transmission. It is determined that the transfer quality expected to suffer does not satisfy the agreed upon transfer quality, and the other communication node If it is determined that the use of the communication network does not end within a predetermined time, it is notified that a collision of the outgoing packet has occurred in the communication network in order to force the communication network to be unused. Signal (eg, Ja
m), and a predetermined time after the detection is detected by the detection means when the communication network is not used, or by the signal transmission means. And a control means for starting transmission of the packet after a predetermined time has passed since the transmission of the signal.

The present invention (claim 7) provides a CSMA / CD
(Carrier Sense Multiple A
access with Collision Dete
ction) system (eg, terminal, router) connected to a communication network (eg, Ethernet) using the method
Is a packet transmission control method for acquiring a right to use the communication network when transmitting a packet for which the transfer quality is to be guaranteed, wherein the node device transmits a packet to the communication network prior to starting transmission of the packet to the communication network. Detecting whether the communication network is in use by another communication node, determining that the communication network is in use, and providing the packet to be transmitted with a predetermined transfer quality. If the packet belongs to a packet flow to be transmitted, it is determined that, by waiting for the packet to be transmitted, the transfer quality expected to be incurred by the packet does not satisfy the determined transfer quality, and If it is determined that the use of the communication network by the communication node does not end within a predetermined time, a collision of an outgoing packet occurs in the communication network. A signal indicative of (e.g., Jam signal) by sending an artificially, characterized in that to the state of not being used to force the said communication network.

The present invention (claim 8) provides a CSMA / CD
(Carrier Sense Multiple A
access with Collision Dete
ction) system (eg, terminal, router) connected to a communication network (eg, Ethernet) using the method
Is a packet transmission method for transmitting a packet whose transfer quality is to be guaranteed, wherein the node device transmits a packet belonging to a packet flow to which a predetermined transfer quality is to be provided to the communication network. Detecting whether or not the communication network is being used by another communication node, and when it is determined that the communication network is not being used by this detection, starts transmission of the packet after a predetermined time has elapsed, When it is determined by the detection that the communication network is in use, the use of the communication network by the other communication node does not end within a predetermined time, and the packet is incurred by waiting for transmission of the packet. If it is determined that the predicted transfer quality does not satisfy the determined transfer quality, the communication network is forcibly switched to a state in which it is not used. A signal (for example, a Jam signal) indicating that a collision of a packet to be transmitted has occurred in the communication network to start transmission of the packet after a predetermined time has elapsed. Is characterized in that the procedure from the detection is performed again after a predetermined time has elapsed.

In CSMA / CD, each transmitting node starts transmission of a packet after confirming that a communication network is not used before starting transmission of a packet. When a collision is detected during transmission of a packet, each transmission node transmits the packet. It is prescribed to cancel.

According to the present invention, when the signal is sent to the communication network by the signal sending means, for example, a transmitting node using the communication network recognizes that a collision of a transmission packet has occurred in the communication network, Stop sending packets. This makes it possible to forcibly put the used communication network into a state where it is not used.

As a result, the node device that has transmitted the signal can use the communication network, and can provide a packet to be transmitted with a transfer quality that satisfies a predetermined value.

In the case where the detecting means detects that the communication network is in use and the packet to be transmitted does not belong to a packet flow to be provided with a predetermined transfer quality, The transmission of the packet may be started after the signal is not transmitted and the communication network is not used.

As described above, according to the present invention, for example, IP
By transmitting a signal for stopping transmission of a packet currently being transmitted on a transmission medium in response to transmission quality of a packet requiring a strict transmission quality such as a guaranteed service in Therefore, the transfer waiting time of the packet at the communication node is reduced, and the packet can be transferred with a transfer quality satisfying the request. The above-described invention is also realized as a machine-readable medium storing a program for causing a computer to execute the corresponding procedure or means.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. The communication network according to the present embodiment provides communication of IP packets between communication nodes, and arbitrary communication nodes are connected via a communication network using the CSMA / CD method. In this embodiment, a communication node refers to a device, such as a terminal or a router, connected to a communication network and transmitting and receiving communication information.

In this embodiment, Ethernet is taken as an example of a communication network using the CSMA / CD system for providing information transfer between arbitrary communication nodes. It should be noted that an information transfer unit at the Ethernet level is referred to as a "frame" in order to distinguish it from an "IP packet" defined at the IP level.

FIG. 1 shows an example of a basic configuration of a communication network according to an embodiment of the present invention. As shown in FIG. 1, terminals 121 and 122 and a router 13 are connected to the Ethernet 11. Further, another communication network (for example, Ethernet, ATM network, etc.) is connected to the router 13.
Hereinafter, between the terminals 121 and 122 or the terminal 121
Alternatively, the present embodiment will be described focusing on IP packet (frame) transfer between the router 122 and the router 13 via Ethernet.

FIG. 2 shows a layer model in communication via Ethernet. As shown in FIG. 2, an IP packet transferred in a communication node that transmits the IP packet has an L packet in a data link layer that defines a service to be provided to an upper layer (network layer).
After passing through an LC (Logical Link Control) layer, the MA in the same data link layer
The data is transferred to a C (Media Access Control) layer and converted into a frame format defined by a MAC layer (Ethernet). This frame is transmitted onto the transmission medium via the physical layer according to a method of accessing the transmission medium (for example, a coaxial cable) by CSMA / CD. When the communication node, which is the destination of the IP packet, receives the frame transferred on the transmission medium, the received frame is converted into an IP packet again in the order of the physical layer and the data link layer, contrary to the above flow.

Here, as shown in FIG. 3, a case where the terminals a to c share a communication medium as shown in FIG.
The principle of the A system and the CSMA / CD system will be described.
In the CSMA method, a terminal having transmission data (terminal a) first monitors a transmission medium prior to transmission. If a carrier (transmission signal) is being detected, transmission is postponed because the bit string transmitted by another terminal (referred to as terminal c) is propagating through the transmission medium (FIG. 3A). If the carrier is not being detected, the transmission medium is not used by another terminal (since it is in a stationary state), so that transmission of a frame is started (FIG. 3B). In this way, a frame is transmitted to a transmission medium shared by a plurality of terminals.

However, in the CSMA system, there is a time difference in which a frame propagates on a transmission medium.
When the terminal that has detected the stationary state starts transmitting a frame, another terminal (terminal b) may also transmit a frame, so that both frames may collide on the transmission medium (FIG. 3). (C)).

In order to avoid such a problem, each terminal monitors the presence or absence of a collision during transmission, stops transmission when a collision is detected, waits for a certain time, and repeats the same procedure again for retransmission. That is, a method in which a countermeasure after a frame collision is added to the CSMA method is provided as the CSMA / CD method.

FIG. 4 shows a processing procedure of an IP packet transmitting terminal according to the conventional CSMA / CD system. The transmitting terminal converts the IP packet to be transmitted into a frame (step S41) and checks the state of the transmission medium (step S42). If no carrier is detected in the transmission medium, transmission of a frame is started after waiting for a specified time (step S43).

If a collision of a frame is detected during frame transmission (step S44), the transmitting terminal sends a Jam signal to inform another terminal of the collision state (step S4).
5) After the calculated retransmission interval has elapsed, retransmission of the frame is attempted (step S46).

When the transmission of the frame is completed (step S
47), this processing procedure ends (step S48). Note that a retransmission interval, which is calculated when a frame collision occurs and is a waiting time until a frame is retransmitted, is given by the following equation. (Retransmission interval) = (slot time) × n where the positive number n is randomly selected from the next range 0 ≦ n <2 ^k [k = min (m, 10), m: number of collisions] where slot The time indicates the time required for transmitting a packet of the minimum size. If the number of collisions (m) exceeds 16, a transmission error occurs.

By using this procedure, if the transmission medium becomes crowded and the collision of the frames increases, the probability of the collision of the frames can be reduced by increasing the average retransmission interval of the collision frames exponentially. .

In this embodiment, the conventional C
An IP packet (frame) requesting a service to be provided with a previously requested transfer quality, such as a guaranteed service, by improving the processing procedure of an IP packet transmitting terminal by the SMA / CD method
For this purpose, the transfer waiting time in the transmitting terminal due to waiting in a stationary state on the transmission medium or waiting until retransmission starts due to frame collision on the transmission medium is reduced.

FIG. 5 shows a processing procedure of the communication node when transmitting an IP packet in the present embodiment. FIG.
Is a basic processing procedure of the conventional C shown in FIG.
This processing procedure is the same as the SMA / CD scheme. However, in this processing procedure, when a communication node transmits an IP packet (frame) requesting a service to be provided with a previously requested transfer quality, the communication node transmits the IP packet (frame) on a transmission medium when transmitting the frame. The new operation when a carrier is detected by using the above is newly defined.

When the transmitting terminal transmits an IP packet requesting a service to be provided with the transfer quality required in advance, if a carrier is detected on the transmission medium (step S42), the transmission medium is in a stationary state. By delaying the IP packet until it becomes, it is determined whether or not the transfer quality that the IP packet will suffer will not satisfy the required quality (step S51).

If it is determined that the required quality cannot be satisfied, the transmitting terminal simulates transmitting a Jam signal to stop the transmission of the frame currently being transmitted on the transmission medium (step S52). Thereafter, after a specified time has elapsed, the transmission terminal starts frame transfer (step S43).

The difference between this procedure and the conventional CSMA / CD method is that when transmitting an IP packet requiring strict transfer quality, even if a frame already being transmitted on the transmission medium exists, The point is that the Jam signal is artificially transmitted to interrupt the transmission. This reduces the time that the communication node waits for the transmission of an IP packet requiring strict transfer quality until the transfer of the frame being transmitted on the transmission medium is completed. As a result, the IP packet It is expected that the time required to complete the transfer will be reduced.

FIG. 6 is a block diagram showing a part related to the transmission of an IP packet in the communication node executing the procedure shown in FIG. The communication node according to the present embodiment has I
A P packet identification unit 61, a frame conversion unit 62, a frame transmission unit 63, a transmission medium monitoring unit 64, a retransmission interval calculation / control unit 65, a Jam signal transmission unit 66, and an IP packet schedule unit 67 are provided.

The IP packet identification section 61 transmits the IP packet to be transmitted.
Based on the header information of the packet, the flow to which this packet belongs is identified. The frame conversion unit 62 transmits the I
Convert P packets to frame format.

The frame transmitting section 63 transmits a frame onto a transmission medium. The transmission medium monitoring unit 64 monitors the state of the transmission medium and notifies this state. The retransmission interval calculation / control unit 65 calculates a time interval until retransmission due to a frame collision or the like, and instructs whether to transmit a frame based on the obtained time interval.

The Jam signal transmitting section 66 detects a frame collision or sends a Jam signal based on a pseudo Jam signal transmission request.
Send the signal onto the transmission medium. The IP packet scheduler 67 predicts the transfer quality that will be received by an IP packet belonging to a flow requiring transfer quality, such as a Guaranteed service, and if it does not satisfy the required quality, sends the pseudo Jam signal. Request.

In the communication node shown in FIG. 6, the following processing is performed to realize the procedure shown in FIG. From the IP packet identification unit 61 to the frame conversion unit 62
The IP packet to be transferred, which has been converted into the frame format through the network, is temporarily stored in the frame sending unit 63 and only when the content of the transmission enable / disable signal notified from the transmission medium monitoring unit 64 indicates that transmission is possible. , And the frame is sent from the frame sending unit 63 to the transmission medium.

The transmission medium monitoring unit 64 determines whether another frame is being transmitted on the transmission medium, and whether the frame transmitted from the communication node has collided with another frame on the transmission medium. Is constantly monitored, and based on the monitoring result, a frame transmission enable / disable signal is sent to the frame transmission unit 63.
A signal indicating that a frame collision has occurred is notified to the Jam signal transmission unit 66. Further, it notifies the retransmission interval calculation / control unit 65 to calculate the waiting time (retransmission interval) until the frame retransmission.

The retransmission interval calculation / control unit 65 calculates the retransmission interval when receiving a notification from the transmission medium monitoring unit 64 and the Jam signal transmission unit 66 that the transmission of the frame has failed. A transmission start time is determined, and at that time, a signal to the effect that transmission can be started is notified to the transmission medium monitoring unit 64.

The Jam signal sending unit 66 stops sending a signal indicating that a frame collision has occurred, which is notified from the transmission medium monitoring unit 64, or another frame currently being transferred, which is notified from the IP packet schedule unit 67. Upon receiving a signal indicating that the signal is to be transmitted, a Jam signal is transmitted on the transmission medium. When the Jam signal is transmitted according to the notification from the IP packet scheduler 67, the Jam signal transmitter 66 notifies the retransmission interval calculator / controller 65 to calculate the retransmission interval.

In the IP packet scheduler 67, I
According to the notification from the P packet identification unit 61, the I
If it is recognized that the P packet is an IP packet belonging to a flow requiring transfer quality, for example, a guaranteed service, a time at which the transfer should be completed in order to satisfy the required quality is determined in advance. If it is predicted that the transmission of the IP packet is not likely to end, it requests the Jam signal transmission unit 66 to artificially transmit the Jam signal in order to stop the transmission of the frame currently being transmitted.

Next, FIG. 7 shows another processing procedure of the communication node when transmitting an IP packet in the present embodiment. The basic processing procedure in FIG. 7 is the same as the method shown in FIG.
Transmission of a Jam signal that is artificially transmitted so as to forcibly stop transmission of a frame currently being transmitted on the transmission medium in order to satisfy the transmission quality required in advance by the transmission quality that the P packet will suffer. New conditions have been added.

That is, the communication node predicts whether or not the transmission of the frame currently being transferred on the transmission medium will be completed shortly. If it is determined that the transmission is to be completed shortly (step S71), the transmission of the frame is completed. The transmission of the IP packet to be transferred is performed after the end of the transmission without forcibly stopping the transmission of the IP packet.

FIG. 8 is a block diagram showing a part related to transmission of an IP packet in the communication node executing the procedure shown in FIG. The configuration of the communication node in FIG.
Although the configuration is basically the same as the configuration of the communication node shown in FIG. 6, the functions of the transmission medium monitoring unit 64 and the Jam signal sending unit 66 are partially different.

The transmission medium monitor 64 monitors whether or not another frame is being transmitted on the transmission medium, whether or not a frame collision has occurred on the transmission medium, and is currently transmitting. Memorize the transmission start time of the frame,
The time is notified to the Jam signal transmitting unit 66.

The Jam signal transmitting unit 66 receives the request for transmitting the Jam signal from the IP packet scheduling unit 76 in a pseudo manner, and the transmission start time of the frame notified from the transmission medium monitoring unit 64 and the current transmission start time. The remaining time (transmission end time) of the frame currently being transmitted is predicted from the time. At this time, only when the predicted remaining time is larger than a predetermined value, a Jam signal is transmitted so as to forcibly stop the transmission of the frame. It is determined that the transmission of the frame is to be completed soon, and the transmission of the Jam signal is not performed, and the transmission of the IP packet is started after waiting for the transmission of the frame, as in the conventional CSMA / CD system.

Here, the prediction is made by using the method shown in FIG. 7 for judging whether or not to transmit the Jam signal in a pseudo manner based on the remaining transmission time of the frame currently being transmitted on the transmission medium. The effect will be described with reference to FIG. In FIG. 9, the communication node A is Guaran
It is assumed that an IP packet requesting a ted service is transmitted, and the communication node B transmits an IP packet requesting a Best Effort service.

According to the procedure of FIG. 5, as shown in FIG. 9A, while the communication node B is transmitting a frame, the communication node A
When a request for frame transmission is generated, the frame transmitted from the communication node A is obtained by converting an IP packet requesting a guaranteed service, so that the communication node A immediately transmits a Jam signal to the transmission medium. As a result, the frame being transmitted from the communication node B is:
The transmission is interrupted without waiting for the end of transmission. Thereafter, both the communication nodes A and B wait for the calculated retransmission interval to elapse (step S46), and try sending the frame again. At this time, if the retransmission interval calculated by the communication node B is smaller, the communication medium already has another frame (a frame transmitted from the communication node B) when the communication node A starts transmitting a frame. Since the transmission is being performed, the communication node A returns to Jam.
A signal will be sent. By repeating such a situation, in the method shown in FIG. 5, not only the IP packet transmitted from the communication node B but also the IP packet transmitted from the communication node A requesting the Guaranteed service is transferred. The delay (the waiting time even at the communication node) becomes large, and a satisfactory service may not be provided.

On the other hand, according to the procedure of FIG.
As shown in (b), when a request for frame transmission is issued from the communication node while the communication node B is transmitting the frame,
The communication node A predicts the time required until the frame currently being transmitted ends, and determines whether or not to transmit the Jam signal based on this value. Since the communication node A stores the transmission start time of the frame transmitted from the communication node B on the transmission medium (the transmission medium monitoring unit 64 in FIG. 8), the transmission of the frame is performed based on the transmission start time and the current time. The time a is calculated. At this time, the difference between the time b required for transmitting the frame and the transmission time a is the time required until the end of the frame. If the time (ba) is smaller than a predetermined threshold value, the communication node A determines that the transmission of the frame currently being transmitted is to be finished soon, and the communication node A transmits the Jam signal. Do not do. If the time (ba) is larger than the threshold value, the communication node A determines that the transmission of the currently transmitted frame is to be continued for a while, and the communication node A transmits the Jam signal. Perform By newly adding such processing, it is possible to greatly reduce the transfer delay that occurs when the method shown in FIG. 5 is adopted.

Now, in addition to the packet transmission control method described above, a method of calculating a retransmission interval, which is a waiting time until retransmission of a frame, calculated by the retransmission interval calculation / control unit 65, is as follows. By using a slightly modified method defined in the conventional CSMA / CD method, the communication node waits for an IP packet requiring a strict transfer quality, such as a guaranteed service, to be transmitted on a transmission medium. A further reduction in time is possible.

As described above, the formula for calculating the retransmission interval defined in the conventional CSMA / CD system is as follows. (Retransmission interval) = (slot time) × n where the positive number n is randomly selected from the following range: 0 ≦ n <2 ^k [k = min (m, 10), m: number of collisions] Strict transfer quality In order to reduce the transfer waiting delay incurred by the requested IP packet, in the present packet transmission control method, the above-mentioned value n
Is determined as follows using an integer x randomly selected from the range of 0 ≦ x <2 ^(k−1) . N (= n ₁ ) when sending an IP packet requiring strict transfer quality: n ₁ = x n when sending an IP packet not requiring transfer quality
(= N ₂ ): n ₂ = 2 ^(k−1) + x This means that, as shown in FIG. 10, when transmitting an IP packet requiring strict transfer quality, the most significant bit of the n value is set to 0. When transmitting an IP packet that does not require transfer quality, this means setting the most significant bit of the n value to 1. By determining the retransmission interval using the n value obtained by the above method, the retransmission interval in the communication node that sends out IP packets that require strict transfer quality can be determined by the communication that sends out IP packets that do not require transfer quality. Since the possibility of taking a smaller value is greater than the retransmission interval at the node, the transmission of the frame onto the transmission medium is performed earlier, and as a result, the transfer waiting delay can be reduced.

In order to avoid collision when transmitting IP packets requiring strict transmission quality at the same time from a plurality of communication nodes connected to the same transmission medium,
A method is adopted in which bits other than the most significant bit of the n value (lower k-1 bits) are set at random.

It should be noted that various methods can be considered for calculating the waiting time, in addition to the above-described methods. Also,
Each of the above functions can also be realized as software. Further, the present invention can be embodied as a machine-readable medium storing a program for causing a computer to execute the above-described procedures or means. The present invention is not limited to the above-described embodiment, and can be implemented with various modifications within the technical scope.

[0063]

According to the present invention, when a packet belonging to a packet flow for which a predetermined transfer quality is to be provided is transmitted, the packet currently being transferred on the transmission medium in accordance with the transfer quality which can be predicted. By generating the signal for stopping the transmission of the packet, the transfer waiting time of the packet at the communication node can be reduced, and the packet can be transferred with the transfer quality satisfying the request.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a basic configuration of an IP packet communication network according to an embodiment of the present invention.

FIG. 2 is a diagram showing a layer model in communication via Ethernet.

FIG. 3 shows the principle of the CSMA system.

FIG. 4 is a diagram showing the principle of the CSMA / CD system.

FIG. 5 is a flowchart showing an IP packet transmission procedure in a communication node using the packet transmission control method according to one embodiment of the present invention;

FIG. 6 is a diagram showing a block configuration of a part related to IP packet transmission in a communication node using the packet transmission control method according to one embodiment of the present invention;

FIG. 7 is a flowchart showing an IP packet transmission procedure in a communication node using the packet transmission control method according to one embodiment of the present invention;

FIG. 8 is a diagram showing a block configuration of a part related to IP packet transmission in a communication node using the packet transmission control method according to one embodiment of the present invention;

FIG. 9 is a diagram for explaining an effect of the packet transmission control method according to one embodiment of the present invention;

FIG. 10 is a diagram showing a method of determining a positive number n used in calculating a retransmission interval.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Ethernet 121,122 ... Terminal 13 ... Router 14 ... Communication network 61 ... IP packet identification part 62 ... Frame conversion part 63 ... Frame transmission part 64 ... Transmission medium monitoring part 65 ... Retransmission interval calculation / control part 66 ... Jam signal Transmission unit 67: IP packet schedule unit

Claims (8)

[Claims] 1. A node device connected to a communication network using the CSMA / CD method for transmitting a packet, wherein the communication device is in use before starting transmission of the packet to the communication network. Detecting means for detecting whether or not the communication network is in use by the detecting means, and wherein the packet to be transmitted belongs to a packet flow to be provided with a predetermined transfer quality. In some cases, if it is determined that the transfer quality expected to be incurred by the packet will not satisfy the determined transfer quality by waiting for the packet to be transmitted, a collision of the transmitted packet with the communication network may occur. A node sending means for sending out a signal indicating that the occurrence has occurred in a pseudo manner. 2. A communication system comprising: a communication network using the CSMA / CD system; and a plurality of node devices connected to the communication network for transmitting and receiving packets, wherein at least one of the plurality of node devices is provided. Prior to starting transmission of a packet to the communication network, detection means for detecting whether the communication network is being used by another communication node, and the communication network being used by the detection means Is detected, and if the packet to be transmitted belongs to a packet flow for which a predetermined transfer quality is to be provided, the packet is predicted to suffer by waiting for transmission. If it is determined that the transfer quality does not satisfy the predetermined transfer quality, the communication network is forcibly put into an unused state. Signal transmission means for artificially transmitting a signal indicating that a collision of a transmission packet has occurred in the communication network; and detecting when the detection means detects that the communication network is not used. Control means for starting transmission of the packet after a lapse of a predetermined time from or after a lapse of a predetermined time after the signal is transmitted by the signal transmission means. system. 3. A packet transmission control method for a node device connected to a communication network using the CSMA / CD system to acquire a right to use the communication network when transmitting a packet to guarantee transfer quality. Prior to starting transmission of a packet to the communication network, the node device detects whether the communication network is in use, and by this detection, it is determined that the communication network is in use,
And if the packet to be transmitted belongs to a packet flow for which a predetermined transfer quality is to be provided, the transfer quality expected to be incurred by the packet by waiting for the packet to be transmitted is determined by the rule. If it is determined that the transmission quality is not satisfied, a signal indicating that a collision of a transmission packet has occurred is sent to the communication network in a pseudo manner, and the communication network is forcibly used. A packet transmission control method. 4. A packet transmission method in which a node device connected to a communication network using the CSMA / CD system transmits a packet whose transfer quality is to be guaranteed, wherein the node device has a transfer quality that is predetermined. When trying to transmit a packet belonging to a packet flow to be provided to the communication network, it is detected whether or not the communication network is being used by another communication node, and the detection indicates that the communication network is not used. If it is determined that the transmission of the packet is started after a predetermined time elapses, and if it is determined that the communication network is in use by the detection, the transmission of the packet is awaited by waiting for the transmission of the packet. If it is determined that the predicted transfer quality does not satisfy the predetermined transfer quality, the communication network is forcibly switched to the unused state. To transmit a signal indicating that a collision of a transmission packet has occurred to the communication network to start transmission of the packet after a predetermined time has elapsed, otherwise, a predetermined time has elapsed. A packet transmission method, wherein the procedure from the detection is performed again later. 5. A node device connected to a communication network using the CSMA / CD system and transmitting a packet, wherein the communication network transmits another packet before starting transmission of the packet to the communication network. Detecting means for detecting whether or not the communication network is being used by the node; and a packet for which the packet to be transmitted is provided with a predetermined transfer quality for the packet to be transmitted. If the packet belongs to a flow, it is determined that, by waiting for the packet to be transmitted, the transfer quality predicted to be incurred by the packet does not satisfy the determined transfer quality, and the other communication node If it is determined that the use of the communication network by does not end within a predetermined time,
Signal transmission means for artificially transmitting a signal indicating that a collision of a transmission packet has occurred to the communication network in order to forcibly put the communication network into an unused state. apparatus. 6. A communication system comprising: a communication network using the CSMA / CD method; and a plurality of node devices connected to the communication network for transmitting and receiving packets, wherein at least one of the plurality of node devices is provided. Prior to starting transmission of a packet to the communication network, detection means for detecting whether the communication network is being used by another communication node, and the communication network being used by the detection means Is detected, and if the packet to be transmitted belongs to a packet flow for which a predetermined transfer quality is to be provided, the packet is predicted to suffer by waiting for transmission. It is determined that the transfer quality does not satisfy the determined transfer quality, and the use of the communication network by the other communication node is performed for a predetermined time. If it is determined not ended,
Signal sending means for artificially sending a signal indicating that a transmission packet collision has occurred to the communication network in order to forcibly bring the communication network into an unused state; and The transmission of the packet after a lapse of a predetermined time from the detection when it is detected that the packet is not used, or after the lapse of a predetermined time after the signal is transmitted by the signal transmission means. And a control means for starting the communication. 7. A packet transmission control method for a node device connected to a communication network using the CSMA / CD system to acquire a right to use the communication network when transmitting a packet for which transfer quality is to be guaranteed. Prior to starting transmission of a packet to the communication network, the node device detects whether the communication network is being used by another communication node or not, and the detection indicates that the communication network is being used. Is determined,
And if the packet to be transmitted belongs to a packet flow for which a predetermined transfer quality is to be provided, the transfer quality expected to be incurred by the packet by waiting for the packet to be transmitted is determined by the rule. If it is determined that the transmission quality does not satisfy the given transfer quality and that the use of the communication network by the other communication node does not end within a predetermined time, a collision of a transmission packet occurs in the communication network. A packet transmission control method comprising: sending a signal indicating that the communication network is not in use; 8. A packet transmission method in which a node device connected to a communication network using the CSMA / CD method transmits a packet whose transfer quality is to be guaranteed, wherein the node device has a predetermined transfer quality. When trying to transmit a packet belonging to a packet flow to be provided to the communication network, it is detected whether or not the communication network is being used by another communication node, and the detection indicates that the communication network is not used. When it is determined that the transmission of the packet is started after a lapse of a predetermined time, and when it is determined that the communication network is in use by the detection, the use of the communication network by the other communication node is performed by a predetermined time. A transfer quality that is not completed in time and is expected to be incurred by waiting for transmission of the packet and that does not satisfy the determined transfer quality. If it is determined that the communication network is not in use, a signal indicating that a collision of a transmission packet has occurred is sent to the communication network in a pseudo manner in order to force the communication network into an unused state for a predetermined time. A packet transmission method comprising: starting transmission of the packet after a lapse of time; otherwise, performing a procedure from the detection again after a lapse of a predetermined time.