JP2739239B2 - Node device of communication network - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a node device of a communication network, and more particularly to a network control in a local area network.

[Prior Art] In a local area network, a plurality of stations access a single transmission line to perform communication, and thus there are various access methods. In the CSMA / CD (carrier detection multiple access / collision detection) method (IEEE 802.3), a terminal starts transmission after confirming a carrier on a transmission path. If a collision occurs, stop transmitting and go back off. In this system, the delay is small when the traffic is low, and the collision frequently occurs when the traffic is high, and the throughput is limited. As traffic increases, throughput decreases.

The token bus (IEEE 802.4) and the token ring (IEEE 802.5) are systems in which terminals sequentially acquire a transmission right and transmit. This method has a small delay at the time of high traffic, a small limitation on the throughput, and does not reduce the throughput. However, the delay is not so small when hitting a low tiger.

The methods described in JP-B-58-40384 and JP-A-56-76656 have a network with a tree-like hierarchical structure, enable the packet that arrives at the highest node first, broadcast it over the network, invalidate other packets, and eliminate them. By doing
All packets are prevented from being destroyed by collision, and one communication is always ensured. With this method, it is possible to prevent a situation in which a delay for retry becomes large, and a packet destroyed due to collision does not uselessly occupy the network. Compared to the CSMA / CD system, the difference is that one communication is always established. In addition, when traffic is low, the delay is small, and even when the traffic becomes high, the throughput does not decrease, unlike the CSMA / CD system, and the delay is smaller and the throughput is higher than in the token bus or token ring system. However, as a disadvantage, the network interface unit (NIU) is used because the collision is determined mainly by comparing the output packet and the input packet by address.
Unlike the IEEE (802.3) standard, it is necessary to add a new full-duplex function. Therefore, NIU is more expensive than CSMA / CD, and its protocol is not standardized, unlike CSMA / CD.

The present applicant has filed Japanese Patent Application No.
-15948. In this method, node devices are connected in a tree-like manner, and when there is an input to a lower-order port, the node device gives priority to the first-arrived input port, and gives priority to the input of an upper-order port. It has been established. Collision detection is a method for comparing the presence or absence of a signal at an input / output port. Since the NIU satisfies the IEEE 802.3 standard, the NIU does not become expensive as in Japanese Patent Publication No. 58-40384. There is no decrease in throughput characteristics during high traffic, and it is more advantageous than the Ethernet CSMA / CD method.

[Problems to be Solved by the Invention] Japanese Patent Application No. 63-15948 filed by the present applicant discloses that, in a node device, when an input in a lower direction is switched to an input in an upper direction and output to a terminal, an IEEE 802.15 8
A code "1,1" corresponding to the 02.3 standard FCD may occur, and a reading error occurs in the terminal. Another long "1"
There is a drawback that RS-422 (AC coupling) cannot be used because this signal is used.

An object of the present invention is to provide a node device of a communication network which solves the above-mentioned drawbacks, conforms to the CSMA / CD system, establishes one communication even if a collision occurs, and does not reduce the throughput even during high traffic. I do.

[Means for Solving the Problems] According to the present invention, the communication network includes at least one node device, and when there are a plurality of node devices, these are interconnected in a tree-like hierarchical structure via a transmission line to form a communication network. A node device to be formed, comprising: an upper direction input port means and an upper direction output port means to which a transmission path to a higher order node device is connected; and a plurality of lower level connections to which a transmission path to a lower order node device or terminal are connected. A direction input port means and a lower direction output port means, wherein only signals arriving first at the highest-order node device are transmitted to the communication network, and other signals are excluded. The node device includes an upper direction input port means, an upper direction output port means, a lower direction input port means, and a connection control means for controlling connection of the lower direction output port means, The connection control means, when there is no signal in the upper direction input port means and there is a signal in the lower direction input port means, the lower direction input port means to which the signal has been input first is output to the other lower direction output port means and the upper direction output port means. Connected to the port means, disconnects the other lower direction input port means from the output port means, and when there is a signal at the upper direction input port means, connects the upper direction input port means to all lower direction input port means. Then, the connection of all the lower direction input port means to the output port means is cut off, and after a signal is input to the lower direction input port means, and then a signal is input to the upper direction input port means, the lower order signal which is input first is input to the lower order. The connection between the direction input port means and the other lower direction output port means and the upper direction output port means is disconnected, and after a predetermined time, the upper direction input port means outputs all the lower direction. If the node device is at the highest level, and the signal is present at any of the lower-direction input port means, the connection control means will connect the lower-order input port means to which the signal was input first, and And the other lower direction input port means are disconnected from the output port means.

[Operation] In the node device of the communication network according to the present invention, when a signal is input to the lower direction input port means and a signal is input to the upper direction input port means later, the lower direction input port means and the upper and lower output ports are output. The connection of the means is disconnected, and after a predetermined time, the signal of the upper direction input port means is output to all lower direction output port means. If the output is switched immediately without a predetermined time, "11" will be generated in the input signal of the terminal, and the terminal may perform error reading. However, in the present invention, a predetermined time is provided so that this error does not occur.

[Example] Hereinafter, a specific description will be given based on an example of the present invention.

The node device of the communication network according to the present invention configures a tree having a tree-like hierarchical structure, and validates a packet that arrives first at the highest-order node device. Since each node device transmits the packet in the upper direction and the lower direction, partial communication of the network can be performed even if the node device or the transmission path fails. In a system in which a packet always passes through the highest-order node as in the conventional example of Japanese Patent Application No. 58-40384, failure detection and loopback control are required to obtain the same effect. According to the present invention, when the input of the upper port and the input of the lower port collide with each other in the node device, the input of the upper port is preferentially output to the lower port after a predetermined time. A situation where the signal “11” is output to the lower port does not occur.

Referring to FIG. 2, the network configuration according to the embodiment of the present invention has a tree-like hierarchical structure. Example 3
In a hierarchical structure, two intermediate node devices 1b are accommodated below the uppermost node device 1a, and three 10 BASE devices are located below the intermediate node devices 1b.
5 Adapter 2a is connected. A terminal 3 is connected to each adapter 2a.

The node devices 1 in each hierarchy have the same configuration, and each has one upper direction port 5 and three lower direction ports 4. The upper direction port 5 is connected to the lower direction port 4 of the upper layer node device, and is not used at the highest level.
Lower direction port 4 is connected to the lower node device or 10 BAS
It is connected to an Ethernet terminal 3 via an E5 adapter 2a. For example, an optical transmission line is advantageously applied as a transmission line connecting the node devices 1 and between the node device 1 and the terminal 2. Note that these node devices 1
May be devices having the same configuration, and the present invention is not limited to this particular embodiment with respect to the number of other node devices 1 and terminals 2 to be accommodated, the number of hierarchical levels, and the like. Further, a network may be formed by only a single node device 1. Further, the terminal 2 may be accommodated in the node device 1 of any hierarchy.

The node device 1 shown in FIG.
P) 4-, lower end port (LRP, LTP) 5-communication end detector (EAU) 11, upper direction input detector (UIDU) 7, first-arrival input port detector (FADU) 6, input gate controller ( IG
CU) 9, an output gate control unit (OGCU) 10, and a switching gate unit (SGU) 8. Upper direction input port (URP)
In 4a, an optical data link receiver (O / E) r0 is connected to an optical data reception link i0, and converts an input signal to a TTL level signal. The lower direction input port (LRP) 5a has O / E r1 to r3 connected to the optical data receiving links i1 to i3.
The upper output port (UTP) 4b and the lower output port (LTP) 5b are connected to the optical data link transmitter (E /
O) is connected to the optical data transmission link and converts a TTL level input signal to an output signal. ORP of LRP5a is carrier
An L level (L) is output in an off state, and an H level (H) is output in a carrier on state for starting communication.

The communication end detection unit (EAU) 11 has a NOR gate 22, which receives the output of O / E r1 to r3 from the path a and detects the presence or absence of communication. When communication is completed, the shift register 20 operates at the clock CK0, and outputs the output to the inverter 24 and the NAND
Give to gate 26. The NAND gate 26 always outputs H, and at the end of communication, outputs an L pulse to output the flip-flop 30 to
Reset 36 and initialize the node device.

The first-arrival input port detection unit (FADU) 6 is a flip-flop 32, 34, which inputs the output of the URP 5a via the inverter 28.
36 and two AND gates 38, when there are a plurality of inputs from the lower three channels at the same time, one of the first-arrived inputs is selected according to the priority order in the embodiment, and the first-arrived input port detection signal S1 is output. Output to AND gate 44 and OR gate 46. When there is an input to any of the ports of the LRP, the AND gate 40 sets the S terminals of the flip-flops 32, 34, 36 to L, renders them inactive, and outputs L to the inverter 54. The upper direction input detector (UIDU) 7 has a flip-flop 30 for inputting the output of the URP. When there is an input in the URP 4a, the output Q is inverted to H and the output is inverted to L.

The input gate control unit (IGCU) 9 has three AND gates 44.
The gate 44 receives the first-arrival input detection signal S1 and the output of the flip-flop 30, and outputs the signal S1 to the SGU8 when there is no input to the URP4a, and turns off the signal when there is an input to the URP.

The output gate control unit (OGCU) 10 has a NAND gate 52, which is connected to inverters 54 and 56 by an AND gate 4.
When 0 and the output of the shift register 50 are input, the output of the flip-flop 30 is input, and when there is no input to both the LRP5a and the URP4a, the H of all lower port selection signals S2 is output. The signal S2 is supplied from the OR gate 46 to the AND gates 65 to 67 of SCGU8.
To enable them. UR in this state
If there is an input at P4a, this input is broadcast from LTP. LR
After the input to P5a, if there is an input to URP4a, the NAND gate 52 is turned off, the signal S2 is turned off, the shift register 50 operated by the clock CK1 is activated, and after a predetermined time longer than one bit, the inverter 56 is turned off. Is output to H. NAND gate 52 turns on again, and outputs signal S2.

The switching gate unit (SGU) 8 is connected between URP and LTP,
Make connections between RP and UTP and other LTP. AND gate 56,5
7,58 corresponds to LRP, OR gate 60 is UTP, OR gate 61 ~
63 corresponds to LTP, and AND gates 65 to 67 connect the input of URP4a to LTP
The gate to transfer to. The switching mode will be described below.

(1) When there is an input to the upper direction input port (URP) 4a,
The flip-flop 30 is set. SGU8 AND Gate 6
5 to 67, input the all lower port selection signal S2 from the OR gate 46 from the path d, and input the output of the URP 4a from the path b. U
The output of RP4a is sent from OR gates 61-63 to all links 01-0 of LTP5b.
2 and received by the called station.

(2) Lower direction input port (LRP) 5a has an input and O / E
If r1 is a first-come, first-served input detection signal
In response to S1, the output signal of O / E r1 is input from the path b, and is output to the OR gates 60, 62, and 63. The input signal is broadcast from the UTP4b and other LTP5b to the network and reaches the receiving terminal. .

(3) There is an input at O / E r1 of LRP5a, UTP4b and other LT
While broadcasting from P5b, if there is an input to URP4a,
The flip-flop 30 is set, and the output of the flip-flop 30
Turn off D-gates 44 and 56 to stop broadcasting. After a predetermined time, the input signal of the URP4a is broadcast from the LTP5b. However, since no reception signal is input to the output port of the first-come-first-served input, the input signal of the URP4a is immediately transferred.

Next, the 10 BASE 5 adapter 2a will be described with reference to FIG. The adapter 2a is a device that is connected to the terminal 2, relays transmission / reception signals, and detects a collision. Node connection port (NC
The P) 121 is connected to the NIU via an optical data link, and the transmitter (E / O) 80 and the receiver (O / E) 81 convert transmission / reception signals from the optical data link to TTL levels. The terminal connection (TCP) 131 is connected to the Ethernet
connected with rnet terminal, receiver 83 of transmit line,
The transmitter 84 of the receiving line and the transmitter 85 of the collision line mutually convert the transmission / reception signals of the terminal to the TTL level. The collision detection unit (CDU) 141 is connected between the TCP 131 and the NCP 121, and relays transmission and reception signals of both. OR gate 70
Return the transmission signal of TCP131 to TP131. Inverter 71-7
3, flip-flop 74, shift register 74, gate 76
Detects collisions between transmitted and received signals and generates a signal generator (CPG) 77
And outputs a synchronization signal to the TCP 131 as a collision signal.

The 1 BASE 5, 10 BASE T adapter in Fig. 4 is STARLAN
(1 BASE 5), Twisted Ethernet (10 BASE T) terminal 2
NCP 121.TCP131 and Failure Detector (CDU) 1
It consists of 42. The CDU 142 loops back the transmission signal from the terminal 2 and outputs a Manchester code violence signal to the reception line on the terminal side upon detecting a collision between the transmission and reception signals.

FIG. 5 shows a network interface unit (NIU) having a collision detection unit (CDU) 141 and a node connection port (NCP) 121 shown in FIG.
This is an example in which is incorporated. The CDU 141 connects the transmission / reception signal and the collision signal to the Ethernet interface 133 in Manchester code. In addition, an I / O module including one or more lower-order ports of the node device can be used, and the collision detection unit 141 can be incorporated therein. Further, these modified embodiments can be combined. As described above, the collision detection unit can be provided at an appropriate place between the node device and the terminal.

Next, the basic operation of the network according to the present invention is described in Section 6A.
This will be described with reference to FIGS. 6 to 6D.

In FIG. 6A, terminal 200 transmits message packet 200a to terminal 203.
Sent to At the same time, terminals 201 and 202 transmitted message packets 201a and 202a, respectively. In the node devices 100 and 102 shown in FIG.
Since 200a was the first-arrival input signal, it was output from the upper-direction port 5 and the lower-direction port 4 other than the first-arrival input port. Message packet 202a in the node device 101
Are the first-come first-served input signals, and are output from the upper-direction port 5 and the lower-direction ports 4 other than the first-come input port. At this point, the message packet 202a has arrived at the terminal 203. The 10 BASE 5 adapter 301 output the collision signal 301a to the terminal 201 because there were input signals at both the node device side port and the terminal side port.

In the node device 102 of FIG. 6C, the message packet 200a or the first-come-first-served input signal. Since there is no upper direction port, the input signal 202a is output from the lower direction port 4 other than the first-arrival input port. In the node device 101, since the message packet 200a was input to the upper direction port 5, the message packet 200a was transmitted to the 10 BASE 5 adapter 302 on the first input port side.
10 BASE 5 adapter other than the first-come first-served input port
In 3, the message packet 200a was output after a predetermined time.

The reason is that the terminal 203 of the adapter 302 receives the message packet of the first-arrival input port, and the decoder is synchronized with the signal “0101...” Of the preamble portion. If the first-come input is immediately switched to the input of the upper direction port 5, the regularity of the signal is lost, and the signal may be “11”. This signal is a data read start signal in the IEEE 802.3 FCD, and the decoder outputs an error. In order to prevent this, the node device switches after one bit or more.

By the way, the 10 BASE 5 adapter 302 receives signals from both the port on the node device side and the port on the terminal side.
A collision signal was output to 2.

In FIG. 6D, the first-come-first-entered message packet of the highest-order node device 102 reaches all the terminals of the network and is received by the destination terminal 203.

FIG. 7 shows the relationship between the transmission delay time and the throughput.
400 is the characteristic of the present invention, 410 is that of Ethernet, and 420 is that of Token Ring.

The system of the present invention is a kind of CSMA / CD system, but one communication is established even if a collision occurs. This prevents an increase in retransmission latency and prevents packets destroyed by collisions from occupying the network in a meaningless manner. Can be

The present invention is not limited to the embodiment. For example, the direction input port 4a and the lower direction input port and 5a of FIG. 1 are RS-422 receivers, and the upper direction output port 4b and the lower direction output port 5b are RS It can be configured with a -422 transmitter. Further, the number of ports of the lower direction input port 5a and the lower direction output port 5b is not limited to the three ports of the embodiment.

[Effects of the Invention] According to the present invention, at least one packet is transmitted even if a collision occurs, and communication is established.
2.3 For example, Ethernet (10 BASE 5), STARLAN (1
While using the BASE 5) protocol, higher throughput and better throughput / delay characteristics were obtained. Also, the absolute value of the throughput was increased. Since the collision detection is determined based on the presence or absence of a transmission / reception signal, the cost is lower than that of the conventional node device. In addition, since a collision is detected outside the terminal, a terminal having an existing IEEE 802.3, for example, an Ethernet (10 BASE 5), STARLAN (1 BASE 5) interface device (NIU) protocol can be compatiblely connected.

When the node device outputs an input from the lower direction and receives an input from the upper direction, the node device outputs the latter after a predetermined time, thereby eliminating error reading due to the terminal signal "11". Compared to the method described in Japanese Patent Application No. 63-15948, the reliability of the network system is improved, and since a long "1" signal is not output, AC coupling according to the RS-422 standard becomes possible, and the cable used for the link can be freely used. Degree, the practicality is high.

In addition, if the output of only a specific port is stopped for a predetermined time, the preamble portion can be prevented from being cut off when the packet passes through the node device in multiple stages, and the transmission characteristics of the network are improved.

Furthermore, since collision detection can be performed at any point between the input / output means of the node device and the terminal, retransmission control can be performed efficiently.

Further, by detecting the communication end detection by the presence or absence of a signal, the system can be configured at a low cost.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an embodiment of a node device according to the present invention. FIG. 2 is a diagram showing an example of a network configuration in which the node device according to the embodiment of the present invention is applied to a tree-like hierarchical structure network. FIG. 3 is a diagram showing a configuration example of a 10 BASE 5 adapter having a collision signal output line. FIG. 4 is a diagram showing a configuration example of a 1 BASE 5/10 adapter which outputs a collision detection to a reception line. FIGS. 6A to 6D are diagrams showing a configuration example of a terminal interface device to which a collision detection function is added, FIGS. 6A to 6D are explanatory diagrams showing a communication control method in the network of FIG. 2, and FIG. FIG. 7 is a diagram showing an example of a throughput delay characteristic showing performance evaluation of a LAN and another system in a LAN. Description of Signs of Main Parts 1 Node device 2 Adapter device 3 Terminal 4 5 Port 6 First-arrival input port detection unit 7 Upper-level input detection unit 8 Switching gate unit 11 Communication end detection section 121 Node connection port 131 Terminal connection section 141 Collision detection section

Claims (5)

(57) [Claims] 1. A node device including at least one node device and, when there are a plurality of node devices, interconnected in a tree-like hierarchical structure via a transmission line to form a communication network, Upper direction input port means and upper direction output port means to which a transmission path to a lower node device is connected, and a plurality of lower direction input port means and lower direction output ports to which a transmission path to a lower node apparatus or terminal is connected Means, wherein only signals arriving first at the highest-order node device are transmitted to the communication network, and other signals are excluded. Connection means for controlling connection of the port means, the upper direction output port means, the lower direction input port means, and the lower direction output port means, the connection control means comprising: When there is no signal in the upper direction input port means and there is a signal in the lower direction input port means, the lower direction input port means to which the signal is input first is connected to the other lower direction output port means and the upper direction output port means. Disconnecting the other lower direction input port means to the output port means, and when there is a signal at the upper direction input port means, connect the upper direction input port means to all lower direction input port means; Disconnect the connection of the lower direction input port means to the output port means, and when a signal is input to the upper direction input port means after a signal is input to the lower direction input port means, the lower direction input port to which the signal is input first is input. The connection between the means and the other lower direction output port means and the upper direction output port means is disconnected, and after a predetermined time, the upper direction input port means is changed to the all lower direction output port means. When the node device is at the highest level, the connection control means, when a signal is present at any of the lower direction input port means, switches the lower direction input port means to which the signal was input first. A node device for a communication network, wherein the node device is connected to another lower direction output port means, and the connection of the other lower direction input port means to the output port means is disconnected. 2. The node device according to claim 1, wherein when a signal is input to the upper direction input port means after a signal is input to the lower direction input port means, the connection control means:
The signal is immediately transferred to the lower output port means to which the signal has been input first, and the signal from all lower input port means is prohibited from being transferred to the upper output port means and the lower output port means. A node device of a communication network, wherein a signal of an upper direction input port means is output from another lower direction output port means after a lapse of time. 3. The node device according to claim 1, wherein one of said input / output port means transmits a predetermined signal to said terminal when substantially simultaneously detecting a transmission signal and a reception signal of said terminal. A node device for a communication network, comprising a collision detection unit. 4. In the communication network including the node device according to claim 1, when substantially simultaneously detecting a communication signal and a reception signal of the terminal, the collision detecting means for transmitting a predetermined signal to the terminal includes the collision detection unit. And a communication network provided in any of the terminals. 5. The node device according to claim 1, wherein said device includes means for initializing a connection state of said node device when there is no signal from said upper direction input port means and said lower direction input port means. A node device characterized by the above-mentioned.