JPH0728304B2 - Communication method between local networks - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a communication method between local networks, and more specifically, in a network in which a plurality of local networks are connected via a relay device, one local network is used. The present invention relates to a relay system for a communication frame from a communication terminal included therein to a communication terminal included in another local network.

[Conventional technology]

When the number of communication terminals (ST) on the network increases, all STs are connected to one local network (LAN: CSMA / C
It is preferable from the viewpoint of performance and reliability that the LANs are distributed over multiple LANs rather than connected on a D-bus LAN or token ring LAN).

For example, if more than a substantial number of STs are connected to one token ring LAN, the bit error rate and frame loss rate will increase. There is also a problem that a communication function between all STs on the network is lost due to a failure occurring at one place on the network.

On the other hand, if STs are distributed over multiple LANs, each L
The number of connection STs for each AN can be kept to a practical number, and the stop of communication function due to a failure can be kept within the range of the LAN concerned. Also, when ST is distributed to multiple LANs, the communication in one LAN does not affect the communication in other LANs, so the communication load for each LAN can be reduced, and performance in a broad sense. It is possible to improve. These advantages are
The same applies to a system consisting of multiple LANs with different protocols and topologies.

To connect multiple LANs to each other, a relay device, that is, a bridge is required between the LANs. The bridge here can be defined as having the function of passing the communication frame received from one LAN to the other LAN, but in order to enable communication between STs connected to different LANs, each bridge has Furthermore, the following functions are desired.

(1) Do not impair the reliability of the communication function between LANs: It is to prevent the communication function of each ST from being lost due to a bridge failure. For this purpose, between the bridges or the communicating STs. A configuration capable of backing up the communication path is desired.

(2) Do not reduce the performance of the communication function between LANs: that is, prevent a specific bridge from becoming overloaded and degrading the communication performance through this bridge. It is desired to have a structure that can be dispersed in a plurality of bridges.

(3) Enabling communication between STs connected to LANs with different protocols: For example, token ring LA
It is to enable communication between ST connected on N and ST connected on LAN of CSMA / CD bus system. To this end, it is necessary to ensure that the operation of each bridge is not affected by the protocol of the connected LAN.

(4) No restriction on the connection between ST and LAN: That is, each bridge does not restrict the connection between ST and LAN in terms of time and location. For this, each ST
It is necessary to consider the method of acquiring the address of and the setting method of the communication route according to the address.
For example, it is desirable that the bridge and the ST can cooperate with each other each time the connection position of the ST changes.

Conventionally, in a network system composed of a plurality of LANs, as a communication method between STs belonging to different LANs, for example, “Source Routing for Local Area Networks” is used.
Networks) "by KKSy, DAPitt, RADonnan in the following references:

Proceedings of IEEE CLOBECOM, 1985, P.1019-1023 According to this report, communication between STs is performed by the following procedure.

(1) The source ST broadcasts a special frame (FRB) for knowing the address of the target ST that is the communication partner.

(2) Upon receiving the FRB, the bridge inserts its own identifier (referred to as Segment Number: SN in the above document) into this FRB and relays it to the next LAN.

(3) The target ST returns the SN group included in the received FRB, that is, the route information, to the source ST as a response of the FRB.

(4) The source ST determines the destination ST from the route information sent back.
When the address is added, the route to the target ST is recognized. After that, between these STs, communication is performed by including the above route information in the communication frame.

(5) The bridge that has received the communication frame including the route information determines whether to relay the frame according to the route information.

[Problems to be Solved by the Invention]

However, according to the conventional communication method described above, each ST receives a large amount of route information (ST group) included in the communication frame with the other ST.
It is necessary to store it for each case, which causes a problem that the load on the ST increases.

In addition, the bridge must also check all SNs included in the route information in the received frame and judge whether or not the frame should be relayed to another LAN by itself, which increases the bridge load. .

An object of the present invention is to use an S that belongs to a different LAN with a simple communication frame without using the route information that represents all the relay addresses on the route, which is required in the above conventional method.
It is to provide an inter-network communication method that enables inter-T communication.

[Means for solving problems]

In order to achieve the above object, in the present invention, a network including a plurality of local networks (LAN), a relay device (bridge) interposed between the LANs, and a communication terminal (ST) connected to the LAN. In the system, a unique identifier is assigned to each bridge in advance, and the ST that is the source of the communication frame specifies the bridge that first relays the communication frame in addition to the address of the ST that is the destination. An identifier and a second identifier designating the last bridge to be relayed are set in the communication frame, and each bridge is assigned its own identifier and the first and second identifiers included in the communication frame. Accordingly, the communication frame to be relayed and the local network of the relay destination are selected.

In the present invention, an identifier of each bridge (bridge identifier: BIN) is given for each connection port (port) with the local network, and a bridge connected to N LANs has N kinds of BINs. To do.

[Work]

In general, the communication frame transmitted by each ST includes an address (Source Address: SA) indicating the source and the ST serving as the destination.
Address indicating the (target ST) (Destination Address: DA)
And are included. In the communication system of the present invention, the above-mentioned first
The identifier (hereinafter referred to as SA / BIN) and the second identifier (hereinafter referred to as DA / BIN) correspond to the conventional SA and DA, respectively, and are included as part of the SA field and DA field. Constitutes a communication frame.

Communication between STs includes communication between two STs belonging to the same LAN and communication between two STs belonging to different LANs.
According to the present invention, in the case of communication within the same LAN, the above S
It is sufficient to give a specific value to A / BIN and DA / BIN, for example, all / zero. In the case of communication between different LANs, the source LAN
Set the BIN as the exit of SA to BIN and the BIN as the entrance of the target LAN to DA / BIN.

In addition, in order to prevent deterioration of communication performance due to bridge failure and load concentration, main LANs are connected in parallel by multiple bridges and multiple communication paths are prepared,
According to the present invention, the route is specified by SA / BIN, DA / BIN at the source ST, and only the bridge whose SA / BIN contained in the communication frame and its own identifier match on the source LAN. , Takes in the communication frame and performs a relay operation. On the other hand, among a plurality of bridges having an exit on the target LAN, only a bridge having an identifier matching DA / BIN captures the communication frame and relays it to the target LAN. In the case of a network configuration that requires relaying with multiple bridges between the source ST and the target ST, whether or not relay operation is required and relay LA depending on SA / BIN and DA / BIN for each bridge
A route table (routing table) for selecting N may be given in advance and referred to.

The values of SA / BIN and DA / BIN required by the sender ST can be known by an artificial survey or by using the following broadcast communication (broadcast) function. That is, the purpose
Prior to general communication with the ST, the source ST sends a frame (Address
esolving Frame (ARF) is transmitted as broadcast communication. this
The bridge that received the ARF is the BIN that became the ARF receiving point.
And the BIN of the sending and receiving port is sequentially added to a predetermined field in the ARF, and this is relayed to each connection LAN one after another. In this way, at each bridge that relays ARF, the BIN of the receiving port and the sending port
By adding, the sender will set the first BIN included in the response from the target ST to SA / BIN and the last BIN included to DA / BIN.
Can be recognized as. In order to avoid the ARF from going around the network permanently, for example, the number of BINs that can be added to the ARF is limited in advance, and ARFs with a BIN number greater than a predetermined value should not be relayed. Good.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of a network in which a plurality of LANs to which the present invention is applied are interconnected, and in the figure, 1 (1A, 1B)
Bridge (2A-2D) LAN (3A-1-3D-)
2) is ST. Note that P, Q ... U are bridge identifiers (BIN) described later.

FIG. 2 is a block diagram of a bridge 1 that connects a plurality of LANs. Each bridge 1 is a message exchange unit (MX
U) 50 and input buffer 55 (55 corresponding to the connected LAN)
A to 55C), an output buffer 56 (56A to 56C) and a LAN communication adapter (LCA) 60 (60A to 60C). The input / output buffers 55 and 56 are, for example, first-in first-out (FIFO).
irst Out) method can be applied and these are interconnected by MXU50.

The LCA60 is composed of a LAN protocol management unit 61 and a LAN connection unit 62 as shown in FIG.
Reference numeral 62 has a signal conversion function including modulation and demodulation of transmission data to the LAN and reception data from the LAN. The LAN protocol management unit 61 identifies communication frames destined to the own LAN (including broadcast communication frames),
Copy to input buffer 55. The MXU 50 searches each of the input buffers 55A to 55C on a time schedule basis, for example, and selectively transfers the copied frame to the output buffers 56A to 56C to which the frame is to be relayed. Each of the LANs 60A to 60C reads the communication frame stored in the corresponding output buffer 56A to 56C and sends it to the LAN.

As shown in FIG. 4, the communication frame sent out on the network has a start delimiter (Start Delimiter:
SD) 40, Destination Address (DA) 41,
Source Address (SA) 42, Information Field (INFO) 43, Frame Check Sequence (Fr
ame Check Sequence (FCS) 44, end delimiter (En
d Delimiter: ED) 45. In the present invention, DA41
The characteristic is that the bridge identifier (BIN) is added to the and SA42 together with the ST number. BIN is the symbol P, Q in Fig. 1
Like U, it is a unique code that identifies each connection port between the bridge and the LAN. BIN included in DA41 (DA / BIN)
46 from another LAN or other wide area network
It indicates the relay point to the LAN to which the destination ST is connected, while the BIN (SA / BIN) 48 included in S42 is the source S
It shows a relay point from the LAN to which T is connected to another LAN or a wide area network.

5 (A) and 5 (B) show the operation of the bridge 1. Of these, FIG. 7A shows the receiving operation of the LCA 60. L
CA60 is SA / BIN of the communication frame that flows on the corresponding LAN.
48 is monitored (step 100), and if SA.BIN 48 is equal to the BIN pre-allocated to itself, the communication frame is input to the input buffer 55 (step 101).
FIG. 6B shows the operation of the MXU50. When the MXU50 takes out a frame from the input buffer 55, it checks DA / BIN (step 200). If DA.BIN is reasonable, that is, if an LCA having a BIN equal to this exists in the bridge, the frame is output to the corresponding output buffer 56 for relaying the LCA.

Thus, by using the communication frame including DA / BIN46 and SA / BIN48, communication between STs connected to different LANs can be performed as follows. In FIG. 1, it is assumed that 3A-3 is a source ST, 3C-3 is a target ST, and 1B is a relay bridge.

In this case, the source ST3A-3 is SA42, DA4 in the communication frame.
Set the following value to 1.

SA / BIN48: Value indicating "P" SA ・ ST49: Value indicating "3A-3" DA ・ BIN46: Value indicating "R" DA ・ ST47: Value indicating "3C-3" The above communication frame is LAN2A Passes through two bridges 1A and 1B on the way to the round, but only in bridge 1B to which BIN "P" is assigned, input buffer 55P → MXU
The relay operation is executed in the order of 50 → output buffer 56R → LAN2C.

FIG. 6 shows a system configuration in which a LAN and a bridge are connected in multiple stages. This system is a LAN that operates with different communication protocols, such as a CSMA / CD bus LAN or token
It may include a ring LAN or the like. In the figure, 1 (1D to 1K) indicates a bridge, 2D to 2J indicates LAN, 3D-1 to 3J-1 indicates ST, and A, B ... O indicate identifiers (BIN) given to each bridge.

Each ST sets BIN in each communication frame as in the network shown in FIG. Same as the sender BIN48
The function of delivering the above communication frame from a bridge assigned a BIN to a bridge assigned the same BIN as the target BIN46 depends exclusively on the function of each bridge. There is no place to do it.

For example, consider a case where a frame is delivered from ST3G-1 connected to LAN2G to ST3D-1 connected to LAN2D. The communication path has a plurality of combinations such as bridges 1K, 1G, 1D or bridges 1K, 1F, 1D.
It is sufficient to give each bridge, for example, a routing table (a detour table) for each destination BIN to determine which route is selected from among the plurality of communication routes. In this way, each ST does not need to know in advance how the frame will be propagated.

When performing communication from ST-3G-1 to 3D-1, the source ST3G-1 sets, for example, "M" in SA / BIN48 and "A" in DA / BIN46. In this case, Bridge 1K to Bridge 1D
For relaying the communication frame to the bridge, for example, a routing table shown in FIG. 7 may be prepared for each bridge interposed in the middle.

5D, 5F and 5K are routing tables provided in Bridge 1D, 1F and 1K, respectively, and SA, BIN48 and D in the communication frame.
It defines the processing contents according to the value of A / BIN46. According to this table, the communication frame originated from ST / 3G-1 reaches ST / 3D-1 via the route of M-K-H-D-B-A. Similarly, the communication frame addressed to 3G-1 transmitted by ST / 3D-1 arrives at ST / 3G-1 by the route opposite to the above. In the latter case, for example, A-B-E-I-K-M
The frame of DA / BIN46 is M so that it becomes the route of
The routing table may be configured to be handled by Bridge 1G on 2E.

When relaying multiple bridges in this way, it is only necessary to properly set the BIN that it will relay to each bridge. This setting and updating may be done manually depending on the obstacle or load, or the program automatically It may be done at.
As a modified example of the present invention, a method in which each bridge updates SA / BIN in the frame to be relayed can be considered.

In the above embodiments, the BIN value is set in units of the connection point between the LAN and the bridge, but for example, each bridge has only two ports, and the relay destination of the frame received (copied) from one LAN is unique. In the case of the above, it is sufficient to set one identifier for the bridge, that is, an identifier for each bridge.

〔The invention's effect〕

According to the present invention, the communication frame is simple, and when the plurality of communication paths are provided between mutually connected LANs, it is possible to easily perform address comparison and verification at each bridge that serves as a relay, thus reducing the load on the bridge. Reduced high-performance network
The system can be configured.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a network including a plurality of LANs to which the present invention is applied, FIG. 2 is a block diagram showing an internal configuration of a bridge, FIG. 3 is an internal configuration block diagram of a LAN communication adapter, and FIG. Communication frame format, FIGS. 5 (A) and 5 (B) are flowcharts showing the operation of the bridge, FIG. 6 is a diagram showing a modified example of the network to which the present invention is applied, and FIG. 7 is the network of FIG. It is a figure for demonstrating the routing table prepared for each bridge. 1 (1A, 1B ...): Bridge, 2 (2A, 2B ...): LAN, 3 (3A-1 to 3J-1): Station 46: DA / BIN 48: SA / BIN 50: Message exchange unit 60 : LAN communication adapter

Claims (4)

[Claims] 1. In a network system comprising a plurality of local networks, a relay device interposed between the local networks, and a communication terminal connected to the local network, each relay device is assigned a unique identifier in advance. In addition to the addresses of the communication terminals that are the source and the destination, the communication terminal that is the source of the communication frame has a first identifier that specifies the relay device that first relays the communication frame, and the last relay. And a second identifier for designating a relay device for performing the above-mentioned relay device are set in the communication frame, and each of the relay devices responds to its own identifier and the first and second identifiers included in the communication frame. A communication method between local networks characterized by selecting a communication frame to be relayed and a local network of a relay destination. 2. Each of the relay devices is assigned the identifier corresponding to a connection port of a local network connected to the relay device, and a communication terminal which is a transmission source of a communication frame,
Two identifiers for designating a connection port between the local network including the communication terminal and the first relay device and a connection port between the local network including the destination communication terminal and the last relay device are respectively described above. The communication method between local networks according to claim 1, wherein the first and second identifiers are set in the communication frame. 3. In the network system, 2
The communication method between local networks according to the first or second aspect, wherein two or more relay devices are interposed in parallel between one local network. 4. The communication frame in which a communication terminal serving as a source pairs the first identifier with an address of the communication terminal and the second identifier with an address of the destination communication terminal. 1st to 3rd, characterized by being set in
Communication method between local networks in paragraph.