JPS60201759A - Data transmission system - Google Patents

Abstract

PURPOSE:To attain the packet relaying with simple constitution by comparing the own node address value with the received address value and providing a packet relaying means when no coincidence is obtained from said comparison. CONSTITUTION:Nodes 101-105 are connected in series via a bidirectional communication medium 100, and the addresses of these nodes are set so that they are increased or decreased from the end at one side through the other end. Each node contains a comparison means to compare the own address value with the received address value. When no coincidence is obtained from this comparison of both address values, the relaying direction is decided according to the difference of address values. Then the packet is transmitted to the medium 100. In such a case, the node at the most right or left end compares the address values and does not relay the packet when the address value is larger or smaller than the own node.

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a data transmission method for a network system in which a plurality of transmission devices are connected in series via a communication medium. [Prior Art] Conventionally, network topologies for transmitting data between a plurality of data transmission devices (hereinafter referred to as nodes) can be broadly classified into the following three types. (1) The star war topology connects all users to a central node capable of managing all communications. Both the advantages and disadvantages of this topology arise from this centralization. Although the control of the central node allows efficient communication and resource management, the limitations and reliability of the central node determine the performance characteristics of the entire network. In addition to this, connecting a central node to other nodes often requires longer cables and is therefore more expensive. Furthermore, since all connections between neighboring nodes are via the central node, the number of relay stages and the amount of relay calls increase. (2) The ring topology is simpler than the star configuration, so the cost of connecting mates with other network elements is cheaper, and it is also a way to eliminate bottlenecks due to the capabilities of the central node. However, the reliability of the entire network now depends on each connected node. Since messages circulate only in one direction, messages will circulate within the network unless each node understands the network configuration and eliminates access to nodes that do not constitute the network. Furthermore, if data is sent continuously, a collision with circulating data may occur. For these reasons, complicated transmission control must be performed. (3) The bus topology is almost the same as a ring in terms of topological simplicity and avoids loss of reliability by employing passive connections. However, many nodes are usually connected to a single communication medium, and when there is high traffic data transmission between specific nodes, communication between the nodes is severely restricted.
High-density data transmission was not possible. As mentioned above, in the past, all connected nodes had to know the network configuration, or a specific single node had to know the network configuration, and complicated procedures were required to establish communication rights. Once it occurred, it could not be easily recovered. [Objective] The present invention was made in view of the problems of the prior art described above, and
The purpose of the present invention is to propose a data transmission system that allows each node constituting a network to perform highly efficient data transmission with simple control, and that allows erroneously transmitted data to be easily removed. - Below is a blank space [Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of a serial packet switching network system, which is a network system according to the present invention, in which 100 is a communication medium, and 101 to 105 are transmission devices ( 110 to 113 indicate terminals or servers (hereinafter referred to as hosts) connected to the node IO1, and in this embodiment, up to four hosts can be connected to each node. The communication medium 100 between each node 1 is bidirectional, and packet communication is performed independently between the nodes. The packet frame configuration for this packet communication is
As shown in FIG. FIG. 2 is a diagram showing the packet frame structure used in this system, where 201 is a start flag for starting one frame, 202 is a destination address section of the frame, 203 is a source address section, and 204 is a transmission described later. This is a command (/- indicates participant control over the network, response to correct or incorrect received data, data communication control such as broadcast communication control, node status, etc., and 205 is a data length indicating the length of the transmission information field. This is the specification section. z06 is the transmission information field and is a maximum of 256 bytes. 207 is the CRC check code of the frame for error control. Note that 208 is the end flag. The above-mentioned destination address section 202 and source address section 20
The details of 3 are shown in FIG. 2(B).The address part includes a node address 211 indicating the address of the node, a group address 212 indicating the address of the group to which the host connected to the node belongs, and an address within the group to which the host belongs. It consists of an intra-group address 213 indicating. Table 1 shows examples of this group name and group address. Here, an example is shown in which the groups are divided into hosts according to the R3-232C standard, hosts according to the GP-IB standard, printer servers, and file servers. In addition to the data packet frames described in Table 1, there are polling control frames shown in FIG. 2(A) and selecting control frames shown in FIG. 2(B) as control frames between nodes and hosts. The polling control frame for polling consists of 'EOT' 221, polling codes 'POL' 222 and ENQ' 223, and the select control frame consists of 'EOT' 221 and selecting codes ''SEL' 224 and 'ENQ'. 2
It consists of 23 parts. The host polls and selects the node using this control frame, and sends and receives l, x, and data. Next, the configuration of the nodes of this system will be explained with reference to the block diagram of FIG. The node 300 corresponds to the node 1ot-105 in FIG. 1, and the communication media 100a and 100b are the line connection control unit 30'.
This line connection control unit 301 connects both communication media when the node 300 is stationed,
When No. 1300 is in operation, control is provided to disconnect both communication media. For example, this line connection control section 301
is a normally closed relay, and by having an indirect structure when the power of the node 300 is turned on, both communication media 100a and 100b are connected when the power of the node is turned off. It is possible to perform control without the influence of A transmission circuit A304 is connected to the d communication medium 100a via a transceiver A302, and a transmission circuit B505 is connected to the communication medium toob via a transceiver B503.
The received packet data on the communication medium is sent to the control unit, and the transmitted packet data is sent on the control communication medium. 306 is a node address setting section, and node 3
A network address of 00 is set. This node address is set so that the value becomes larger (or smaller) in order from the node connected to one end of the system to the node connected to the other end. In the example in diagram i1, node lot is the node address (#O
1), Node 102 (#08), Node 103 (#lO), Node 104 (#18), No1
105 is the address setting of (#20). By setting the note-address so that it increases in a certain direction in this way, the node does not have to update the memory of the network configuration, and the node can only compare the sending request address from the host with the own node address. The packet sending direction can be determined, and whether or not a transfer request packet sent to the own node is addressed to the sending direction node can be immediately determined just by comparison with the own node address. A control unit 310 controls the transmission circuit A 304 or the transmission circuit B 505 to exchange packets on the communication medium 100a or 100b. The force control unit 310 has a configuration for performing data communication with each connected host, and due to the difference in the configuration of the transmission interface unit, there is a part that can be used with R3232C standard hosts,
It is divided into parts that can be used by GP-IB standard hosts. A maximum of four lines of hosts can be connected to the control unit 310, and a socket address setting unit (C) is connected to each host.
321), D (331), E (341), F (35
1)) and transmission circuits (C(332), D(332)
), E (342), F (352)) and transmission interfaces (C (323), D) between each transmission circuit and the host.
(333). E (343), 'v (353)). Next, details of each transmission circuit section will be explained with reference to the block diagram of FIG. 5. 502 corresponds to a transceiver (corresponding to 302, 303 in FIG. 4) in the case of the transmission circuits A304 and B505, and corresponds to a transmission interface in the case of the transmission circuits C322, D332, B342, and F352 (corresponds to 323. in FIG. 4).
333, 343, and 353). Prior to frame reception, a carrier signal sent onto the communication medium is detected by the carrier detection unit 523 via the interface unit 502, and the receiving circuit 520 is placed in a receiving state. Further, received data etc. from the interface section 502 are inputted to a receiving circuit 520, and inputted frame data is transferred to a receiving buffer 521. At that time, only the address part in the received frame is stored in the address register 522, and the address data set in this address register 522 is passed to the comparator 524 in the address setting unit 501 of the own node (306 or 3 in FIG. 4).
21, 331, 341, and 351), and the comparison result is output to the control unit 310. The frame to be transmitted is sent from the control unit 310 to the transmission buffer 5.
11, and then sent from the transmitting circuit 510 to the communication medium via the interface section 502. The communication control of this system will be explained below. First, communication control of the host will be explained with reference to a flowchart showing communication control of the host in FIG. In this system, all data communication between hosts and nodes is performed by polling or selecting from the host. In other words, the host side takes the initiative in communication. If the host has data to be sent from its own host in step 100, the process proceeds to step 102 and generates a transmission frame as shown in FIG. In this case, the setting value of the address setting section 501 of the node section is given priority as the source address 203, and the address setting section 501 of the communication medium 100 has priority.
1 is sent as the source address 203. In data communication between hosts and nodes, all data that needs to be sent and received is transmitted at once, unlike packet communication between nodes, which will be described later. Subsequently, in step 104, a selecting frame shown in FIG. 3(B) is sent to the node. Then, in steps 106 and 108, it is monitored whether there is any received data (response) before timeout. If there is no received data, the process advances to step 122, and 'E' is sent to the node.
OT" and returns to step 100 to perform selection again. In step 106, if there is received data, it is checked whether the received data is "ACK", and if it is not "ACK", the node selects the data. In order to indicate that the preparation for reception is not completed, the process returns to step 100 and waits for the preparation for reception to be completed. ° If "ACK" is received, the process proceeds to step 12, where the transmission data frame is sent to the node, and then timeout is monitored at steps 114 and 116. In the case of a timeout, the process proceeds to the aforementioned step 122, and if the data has been received, the process proceeds to step 118 to check whether the received data is "NAK" or not.
In this case, since the transmitted frame was not correctly received by the node, the transmitted frame is invalidated, the process returns to step 112 to redo communication control, and the transmitted data frame is retransmitted. If the received data is not 'NAK', the process proceeds to step 120 to check whether it is 'ACK', and then returns 'A'.
CK", the transmitted frame was correctly captured by the node, so the process returns to step 100 and ends the data reception process.
° If not “ACK”, proceed to step 122 and “’
EOT" and returns to step 100. If there is no data sent from the host in step lOO, the process proceeds to step 130, and the node sends the data as shown in FIG. 3(A).
Send out the polling frame shown in step 132,
134, waits for a response from the mate until timeout. If there is no response, the process returns from step 134 to step 100, and if there is a response, the process proceeds to step 136.
If it is an "EOT" response, it indicates that there is no data to be sent from the node to the host, so the process returns to step 100.If "EOT" is not received, a data frame is sent from the node. In step 138, the sent data frame is received.Then, in step 140, the data frame check code (BCC check code) 207 is used to check whether there is a reception error in the received frame. If the
In step 144, the received frame is invalidated and the process returns to step 132, where it waits for the data frame to be retransmitted.If the frame is correctly received in step 140, the process proceeds to step 146, where the node sends a message "NAK" to the node. ACK'' is sent, and then in steps 148 and 150 it is monitored until timeout whether or not an ``EOT'' is received. to the node'
If the ACK ``code'' is sent correctly and the data communication ends normally, the ``EOT'' code is sent from the code 117, and the process returns from step 148 to step 100 to prepare for the next data communication. If the "'EOT'" code is sent and a timeout occurs, data communication will not be terminated normally for some reason, and step 150 will be followed by step 152.
Then, the received data is invalidated and the process returns to step ioo. In the above explanation, when sending data to another host connected to the same node, the destination address 202
By specifying the own node address as , data can be sent from a host to another host via the node. Next, the communication control on the node side of node-host communication is
This will be explained with reference to the flowchart shown in the figure. A node starts operating upon activation (polling/selection) from the host. First, in step 200, the carrier detection unit 523 determines whether a carrier has been sent from the host.
Monitor by output, and if carrier is detected, step 2
00, the process proceeds to step 202, and the subsequently sent data is received. Then, in step 204, it is checked whether or not the received data is a selecting frame. If it is a selecting frame, the process proceeds to step 206, and it is checked whether the node can receive data from the corresponding host. If the data cannot be received, in step 208, "NAK'' is returned and the process returns to step 200. If data can be received, step 210
ACK" is returned, and in steps 212 and 214, the process monitors until the data is received until timeout. If the timeout occurs, the process returns to step 200. When the data is sent, the process starts from step 212 to step 2.
16, the data frame is received into the reception buffer 521. When the data reception is completed, in step 218,
Received frame check code (BCC code) 207
Check whether a reception error has occurred in the received frame. If there is no reception error, the process advances to step 220 and “A
CK'', completes the data reception process, prepares for transmission to the destination specified by the destination address 202, and returns to step 200. If there is a data reception error, the process proceeds to step 222;
It responds with "NAK", invalidates the received frame, returns to step 212, and waits for another frame to be sent. If it is determined in step 204 that a selecting frame has not been received, the process proceeds to step 226 to check whether the received data is a polling frame. If it is not a polling frame, the process returns to step 200. If it is a polling frame, proceed to step 230;
Check whether there is data to be sent from the node to the host, and if there is no data to send, proceed to step 246 and E O
T'', and then returns to step 200. If there is data to send, a frame addressed to the host is sent in step 232, and then a response to the sent frame is waited for in steps 234 and 236. If there is no response until timeout, The process proceeds to step 246, and if there is a response, it is checked in step 238 whether or not the response is 'NAK'. If the received data is not ``NAK'', the process returns from step 238 to step 232 and sends the frame addressed to the host again.If the received data is not ``NAK'', the process returns to step 24.
0 and checks whether there is an "ACK" response. In the case of an "'ACK" response, the frame was sent correctly, so the transmitted frame is erased in step 242, the process proceeds to step 246, "E OT" is sent, and the process proceeds to step 20.
Return to 0. If the response is not "ACK" in step 240, it is assumed that a communication error has occurred and the process proceeds to step 246. Transmitted frames are not erased. The exchange of data between a node and a host in the above explanation is all performed in one communication, but in the communication between nodes described below, the data is divided into smaller than a specified amount and sent multiple times. Therefore, communication between the destination node and host is performed when all of the divided and sent data has been sent and received. Communication control between each node will be described below with reference to flowcharts shown in FIGS. 8(A) to 8(C). All communications between nodes are performed using bucket frames shown in FIG. First, in step 300 of FIG. 8(A), the carrier detection unit 523 checks whether a carrier is detected from the communication medium. If a carrier is detected, a packet is subsequently sent, so in step 302 it is checked whether or not the carrier from the communication medium 100a in FIG. 4 has been detected by the transmission circuit A304. In this case, the process proceeds to "receiving A" as shown in FIG.
05, the “Reception B” shown in FIG. 8(C)
"Proceed to processing. If no carrier is detected in either step 300, proceed to step 308, check whether there is transmission data addressed to another node, and if there is no transmission data, return to step 300, Loops until data reception is detected or a transmission request occurs.If there is transmission data in step 308, step 3
Proceed to step 10 to check whether the destination node 7 address is greater than the own node address. In this system, each node address is shown in the &14 diagram.

[(Connection node address to transceiver A302 side) < (own node address) <
(Connection node address to Transy 8B503 side)]
This is to determine from which transmission medium the transmission packet should be sent. If the destination address 202 is smaller than the own node in step 310, it is sufficient to send the packet to the communication medium 100a, and in step 312 the packet is set in the transmission buffer 511 of the transmission circuit A304, and in step 314, the packet is sent to the transmission buffer 511 of the transmission circuit A304. Send the transmission packet and return to step 300. If the destination address 202 is greater than the own node address in step 310, it is sufficient to send the data to the 1oob side of the communication medium, and steps 316 and 318
In similar to steps 312 and 314, transmission circuit B
505, the transceiver B 503 transmits the packet and returns to step 300. Next, reception processing will be explained. When a carrier is detected from the communication medium 100a, the "reception A" process shown in FIG. 8(B) proceeds as described above. In step 320, the received packet from the communication medium Iota is sent to the transmission circuit A304 via the transceiver A302.
The received data is received in the receive buffer 521 of. and step 32
2, it is determined based on the check code 207 whether a reception error has occurred. If a reception error has occurred, the process advances to step 324, and the transmission circuit A304 outputs “N A
K” prepare to send packet, step 3
In step 26, the data stored in the reception buffer 521 is invalidated and the process returns to step 300. If it is determined in step 322 that no reception error has occurred, the process proceeds to step 330, where the address data error stored in the address register 522 and the value of the address setting section 501 are sent to the comparison section 524 from the reception circuit 520 in FIG. It is checked whether the received packet is an "ACK" packet addressed to the own node or not, and if it is an "ACK" packet addressed to the own node, the transmission of the corresponding packet has been completed in step 3.32. clear the packets that
Clear the receive buffer in step 334 and step 30
Return to 0. If it is determined in step 330 that the packet is not addressed to the own node, the process proceeds to step 336, and the process proceeds to step 32.
Similarly to 0, the comparator 524 sends "N A
K "Check whether the packet is addressed to own node" N A
In the case of a "K" packet, the process proceeds to step 338, where transmission preparations are made to retransmit the corresponding packet, and the process proceeds to step 334.The ""ACK" packet and "NAK" packet in the above explanation are shown in FIG. “ACK” in transmission command 204
"packet" and "NAK" packet are specified. This transmission command consists of 2 bytes, and the first byte is for communication between nodes φ and has the structure shown in Table 2 below. Table 2 Destination Table 3 shows the configuration of this packet for communication between nodes 1 and 1. Table 3 Now, if it is determined in step 336 that the packet is not a "NAK" packet addressed to the own node, the process proceeds to step 340, and an "ACK" packet addressed to another node is sent. This is the case of an "ACK/NAK" packet that indicates whether the received packet is normal or abnormal from the packet destination node to the packet source node.This is the case when the packet sequence numbers are not consecutive, etc. A “NAK” packet is sent to request retransmission, and “NAK” packet is sent if all communications are completed normally.
CK" packet is sent. In this case, there is no response to the received packet, so the process proceeds to step 348, which will be described later. In step 340, an "ACK/NAK" addressed to another node is sent. If it is not a packet, the process proceeds to step 342. Check whether the received packet is a data packet addressed to the own node based on the output of the comparison unit 524, and if it is a data packet addressed to the own node, proceed to step 344, and check whether it is the last of the communication data.
If the communication data is the last, all data communication from the source node has ended normally, so the process advances to step 346, where the transmission circuit A prepares to transmit an ACK packet from the source node, and returns to step 300, where preparations are made. If it is not the end of the communication data, the process proceeds to step 347, where the transmission circuit A304 prepares to send an ``ACK'' packet in response to the received packet. The process then proceeds to step 348. Also, in step 340, “to another node”
ACK/NAK" packet, the process similarly proceeds to step 348, where the destination address 2 is set.
The comparison unit 524 determines whether 02 is greater than the own node address.
Check by the output of . If it is larger than the own node address, the process proceeds to step 350, where preparations are made to transmit the received packet from the transmission circuit B505, and step 300
Return to If the destination address 202 is smaller than the own node address, the received packet is invalidated and not transmitted to the transmission circuit B505. Then, the process returns to step 300 in the same manner. This is because there is no node on the communication medium 1oob side that has a node address smaller than its own node address. Further, if the carrier is detected in the transmission circuit B505 in step 302 of FIG. 8(A), the eighth
Proceeding to the "Receive B" process shown in FIG. Similar to step 348, the comparing unit 524 checks whether the destination address 202 is larger than the own node address.
02 is smaller than the own node address, the received packet is prepared to be transmitted from the transmission circuit A304, and when the destination address 202 is larger than the own node address, the received packet is invalidated. This is because there is no node on the communication medium 100a side that has a food address larger than its own node address. In the following explanation, the destination address 202 in the received frame
The comparing unit 524 compares the address value of the node address setting unit 306 with the address value of the node address setting unit 306, and controls to set a flag indicating that the corresponding node does not exist and send it back, although the invalid frame was deleted without being relayed. Therefore, for example, if there is no mate corresponding to the destination address on the network, the status can be immediately grasped. [Effects] As described above, according to the present invention, a highly efficient data transmission system is provided with a simple configuration in which unnecessary packets do not flow on the network.

[Brief explanation of drawings]

'4N 1 is a diagram showing an example of a network system configuration according to the present invention, FIG. 2 (A) is a diagram showing a packet communication frame in the network system according to the present invention, and FIG. FIG. 3(A) is a diagram showing the details of the address part of the packet frame shown in A). FIG. A diagram showing a selecting frame in communication between a transmission device of a network system according to the invention and a host, FIG. 4 is a block diagram of a transmission device according to an embodiment of the network system according to the invention, and FIG. 5 is an implementation shown in FIG. FIG. 6 is a flowchart showing the communication control of the host connected to the transmission device of this embodiment. FIG. 7 is a flowchart showing the communication control of the transmission device of this embodiment with the connected host. ? J8 Figures (A) to (C) are flowcharts showing communication control procedures between the transmission devices of this embodiment. In the figure, 100.100a, 100b, - communication medium, 10
1~105.300...Node, 1ll-114,4
01-404...Host, 301...Line connection control unit, 302, 303...Transceiver, 304.30
5.322.332,342,352,500...Transmission circuit, 306,321,331,341,351,5
01-- Address setting section, 310... Control section, 32
3,333,343,353...transmission interface, 502...interface! , 510... Transmission circuit, 511... Transmission buffer, 520... Receiving circuit, 521... Receiving M/' buffer, 522... Address register, 523... Carrier detection unit, 524...
...This is the comparison section. Figure 1

Claims (1)

[Claims] address setting means for connecting a plurality of transmission devices in series via a communication medium and setting a unique own address for the transmission device; and reception means for receiving data on the communication medium;
a comparing means for comparing destination address information in the data received by the receiving means and own address information set by the address setting means; and a relay means for relaying to a transmission device connected via the communication medium, and the address setting means sets an address so that the address value becomes larger sequentially from one end to the other end of the transmission device connected via the communication medium, and the relay means If the transmission device address in the direction is large, the destination address is smaller than the own address, and if the transmission device address in the sending direction is small, the data is relayed if it is larger than either the destination address or the own address. A data transmission method characterized by not performing