JPS62295534A - Communication system among local networks - Google Patents

Abstract

PURPOSE:To attain the communication between local networks (LANs) with a simple communication frame by assigning an identifier to each bridge coupling each local network (LAN) and setting an identifier designating a bridge relaying its communication frame at first and at last by a sender of the communication frame into the communication frame. CONSTITUTION:In sending a communication frame from a communication terminal equipment (ST) of a sender, a bridge relaying the frame at first is designated. The 1st identifier (SA. BIN) and the 2nd identifier (DA.BIN) designating a bridge relaying at last correspond respectively to a sender address SD and a destination address D4 to constitute the communication frame in a form including the addresses at a part of SA and DA fields. In case of the communication in the same LAN, a specific value is given to the SA.BIN and the DA.BIN. In case of the communication between different LANs, a BIN being an exit of the sender LAN is set to the SA.BIN and a BIB being an entrance of a destination LAN is set to the DA.BIN. Thus, each bridge selects a communication frame to be relayed and a LAN to be relayed in response to an identifier in the said frame and its own identifier. In this case, the identifier of each bridge is given at each connection node of the LAN and the bridge connected to N-set of LANs has N kinds of identifiers.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a communication system between local networks, and more specifically, a communication system in which a plurality of local networks are connected via a relay device. The present invention relates to a method for relaying communication frames from a communication terminal included in one local network to a communication terminal included in another local network in a network.

[Conventional technology]

As the number of communication terminals (STs) on a network increases, all STs can be connected to one local network (LAN: for example, a C8MA/CD bus type LA'N or a token network).
Rather than connecting to a ring type LAN), multiple LA
It is preferable to distributively arrange them in N from the viewpoint of performance and reliability.

For example, when more than a substantial number of STs are connected to one broken ring L A N, the bit error rate and frame erasure rate increase. Also, network”
There is also the problem that a failure occurring at one location will cause a loss of communication functions between all STs on the network.

On the other hand, if STs are distributed and placed in multiple LAs and Ns, the number of STs connected to each LAN can be kept to a substantial number, and communication function outages due to failures can be avoided even if the communication function stops due to a failure.
It can be kept within the range of N.

Also, when ST is distributed over multiple LANs,
Since communication within one LAN does not affect communication within other LANs, the communication load for each LA and N can be reduced, and performance can be improved in a broad sense. These advantages also apply to a system consisting of multiple LANs with different protocols and topologies.

In order to interconnect a plurality of LANs, a relay device, ie, a bridge, is required between each LAN.

The bridge referred to here can be defined as having the function of passing communication frames received from one LAN to the other LAN, but it is also used to enable communication between STs connected to different LANs. Furthermore, the following functions are desired for each bridge.

(1) Do not impair the reliability of the communication function between LANs It is important to ensure that the communication function of each ST is not lost due to bridge failure. A configuration that can back up routes is desired.

(2) Do not degrade the performance of communication functions between LANs:
In other words, the purpose is to prevent a specific bridge from becoming highly loaded and the communication performance via this bridge from deteriorating. To this end, a configuration that can distribute the load among a plurality of bridges is desired.

(3) Enabling communication between STs connected to LANs with different protocols: For example, an ST connected to a token ring LAN and a C8MA/CD bus LAN f. The purpose is to enable communication between STs. For this purpose, it is necessary to ensure that the operation of each bridge is not affected by the protocol of the LAN to which it is connected.

(4) No restrictions are imposed on the connection between the ST and the LAN: In other words, each bridge does not impose any temporal or positional restrictions on the connection between the ST and the LAN. For this purpose, it is necessary to consider how to obtain addresses for each ST and how to set communication routes according to the addresses, as will be described later.

Conventionally, in a network network system consisting of multiple LANs, the communication method between STs belonging to different Ts and ANs is, for example, ``Source Routing for Local Area Networks (Source Routing for Local Area Networks)''.
Rout, ing for Local AreaN
etworks) J entitled, K, ni, sy, D
, A-Pxtt.

It has been reported by R.A.D. onnan in the following literature.

Procedures of T EEE CL
OBECOM.

1985, P, 10], 9-1023 According to this report, communication between STs is performed by the following procedure.

(1) The source ST broadcasts a special frame (FRB) to learn the address of the target ST with which it communicates.

(2) When the bridge receives the FRB, the bridge sends the FRB its own identifier (Segmer+t in the above document).

Number: SN) is inserted and relayed to the next LAN.

(3) The target ST is a group of SNs included in the received FRB,
That is, the route information is sent back to the source ST as a response from the FRB.

(4) The source ST recognizes the address of the destination ST and the route to the destination ST from the route information sent back. Thereafter, communication between these 87 is performed by including route information in the communication frame.

(5) Upon receiving a communication frame containing route information, the bridge determines whether to relay the frame in accordance with the route information.

[Problem to be solved by the invention]

However, according to the conventional communication method described above, each ST
It is necessary to store a large amount of route information (ST group) included in a communication frame for each partner ST, which poses a problem of increasing the load on the ST.

Additionally, the bridge has to check all the SNs included in the route information in the received frame and decide whether or not to relay the frame to another LAN, which increases the bridge load. .

An object of the present invention is to enable communication between STs belonging to different LANs using simple communication frames, without using route information representing all repeater addresses on the route, which was required in the conventional method. The goal is to provide a communication method.

[Means for solving problems]

In order to achieve the above object, the present invention provides a method for connecting a plurality of local networks (LANs), a repeater W (bridge) interposed between each LAN, and a communication terminal (ST) connected to the LANs. In a network system, each bridge is assigned a unique identifier in advance, and the ST that is the source of a communication frame specifies, in addition to the address of the destination ST, the bridge that will first relay the communication frame. A first identifier and a second identifier 5314 specifying the last bridge to relay are set in the communication frame, and each bridge sets its own identifier and the first identifier 5314 included in the communication frame. The present invention is characterized in that a communication frame to be relayed and a relay destination local network are selected according to the second identifier.

In the present invention, the identifier of each bridge (bridge identifier: BTN) is the connection port (boat) with the local network.
A bridge connected to N LANs has N types of BINs.

[Effect]

Communication frames transmitted by each ST generally include an address indicating the source address (Source Address: S
A) and an address indicating the destination ST (destination ST): D
A) is included. In the communication method of the present invention, the first identifier (hereinafter referred to as 5A-BIN) and the second
(hereinafter referred to as DA-BIN), respectively.
SA field corresponds to conventional SA and DA.

A communication frame is configured by including it as part of the DA field.

Communication between STs includes communication between two 87s belonging to the same LAN, and communication between two 87s belonging to different LANs.
However, according to the present invention, in the case of communication within the same LAN, it is only necessary to give a specific value, for example, all zeros, to the above 5A-BIN and DA-BrN.
In the case of communication between ANs, the BIN serving as the exit of the source LAN may be set to SA-BIN, and the BIN serving as the entrance to the destination LAN may be set to DA-BIN.

In addition, in order to prevent deterioration of communication performance due to bridge failures and load concentration, the present invention can be applied in cases where major LANs are connected in parallel by multiple bridges and multiple communication paths are prepared. For example, 5A-BIN, D at the source ST
The route is specified by A-BIN, and in the source LAN, only the bridge whose own identifier matches the 5A-BIN included in the communication frame takes in the communication frame and performs relay operation. . On the other hand, among the plurality of bridges having exits to the target LAN, only the bridge having an identifier matching the DA-BTN takes in the communication frame and relays it to the target LAN. Source ST and purpose S
In the case of a network configuration that requires relaying by multiple bridges between the 5A-BIN and D
A routing table for selecting whether or not a relay operation is necessary and a relay LAN may be provided in advance according to the A-BIN, and this may be referred to.

S A, - B I N and DA required by the source ST
- The value of BTN can be found by manual investigation or by using the following broadcast function. That is, prior to general communication with the target ST, the source ST sends a frame (Address Resolven) for acquiring a bridge address to the target ST.
g Frame: A RF) is transmitted as a circular communication. The bridge that receives this ARP sequentially adds the ARP receiving BIN and sending BIN to a predetermined field in the ARF, connects each connection, and relays these to the AN one after another. In this way, when each bridge that relays ARP adds the BTN of the receiving port and sending port, the first BIN included in the response from the destination ST is 5A-BIN, and the last BTN is DA.
-Can be recognized as BIN. In addition, in order to avoid ARP from circulating around the network forever, 1 For example,
The number of BINs that can be added to an RP may be constrained in advance, and ARPs having the number of BINs greater than a predetermined value may not be relayed.

〔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 multiple LANs are interconnected to which the present invention is applied, and in the figure, 1 (I
A, IB) are bridges, 2 (2A to 2D) are LAN,
3 (3A-1 to 3D-2) are ST. In addition, P, Q
...U is a bridge identifier (B I N) which will be described later.

FIG. 2 is a configuration diagram of a bridge 1 that connects a plurality of LANs, and each bridge 1 has a message exchange unit (
MXU) 50, input buffer 55 (55A to 5.5C), and output buffer 56 (5.5C) corresponding to the connected LAN.
6A to 56C) and LAN communication adapter (LCA) 60
(60A to 60C). Individual power/output buffer 5
5゜56 is, for example, first in, first out F I FO: F
irstIn First Out) methods can be applied, and these are interconnected by MXU50.

As shown in FIG. 3, the LCA 60 consists of a LAN protocol management unit 61 and a LAN connection unit 62.
The LAN connection unit 62 has a signal conversion function including modulation and demodulation of data transmitted to the LAN and data received from the LAN. The LAN protocol management unit 61 identifies communication frames (including broadcast communication frames) whose destination is its own LAN, and stores them in the input buffer 5.
Copy to 5. The MXU 50 searches each input buffer 55A-55C, for example, on a time schedule, and selectively transfers the copied frame to the output buffer 56A-56C to which the frame is to be relayed. Each LAN60A~
60C reads communication frames stored in the corresponding output buffers 56A to 56C and transmits them to the LAN.

The communication frame sent out on the network has a start delimiter (Start Delimiter) as shown in Figure 4.
limiter: SD) 40, destination address (
De+tination Address: DA
) 4 ], Source address (Source Ad
dress: S A) 42, information field (I
NFO) 43, frame check 0 sequence (F
Rame Check Sequence:Fe2
) 44, End Delimiter
r: E D) Consists of 45. In the present invention,
The feature is that a bridge identifier (BIN) is added to DA41 and 5A42 along with the ST number. Furthermore, B.I.
N is a unique code for identifying each connection port between the bridge and the LAN, like the codes P, Q, . . . U in FIG. BIN included in DA41 (DA-BIN)46
from another LAN or other wide area network.
This indicates the relay point to the LAN to which the target ST is connected, and on the other hand, the BIN (SA-B
IN) 48 indicates a relay point from the LAN to which the source ST is connected to another LAN or wide area network.

5(A) and 5(B) show the operation of the bridge 1. FIG. One of these diagrams (A) shows the receiving operation of the LCA 60. The LCA 60 checks the 5A-BTN 48 of the communication frame flowing on the corresponding LAN in step 1.0.
0), if the 5A-BIN 48 is equal to the BIN previously allocated to itself, the communication frame is input to the input buffer 55 (step 101). Diagram (B)
shows the operation of the MXU 50, and when the MXU 50 takes out a frame from the input buffer 55, it
Check N (step 200). If DA-B
If the IN is reasonable, that is, if an LCA with the same BIN exists in the bridge, the frame is output to the corresponding output buffer 56 for relaying to the LCA.

In this way, by using a communication frame including the DA-BIN 46 and 5A-BIN 48, communication between STs connected to different LANs can be performed as follows. Now, in Fig. 1, 3A-3 is the source ST, 3
Assume that communication is performed using C-3 as a target ST and IB as a relay bridge.

In this case, 1 source 5T3A-3 is the SA in the communication frame.
42. Set the following value in DA41.

5A-BTN48: Value indicating rPJ 5A-8T49
: Value DA-'B I N4 indicating r3A-3J
6: Value indicating rRJ DA-8T47: r3
Value indicating C-3J The above communication frame passes through two bridges IA and IB on the way to LAN2A,
Only in the bridge IB to which BINrPJ is assigned, the relay operation is executed in the order of input buffer 55P-+MXU50→output buffer 56R-) LAN2C.

FIG. 6 shows a system configuration in which LANs and bridges are connected in multiple stages. The system may include LANs operating with different communication protocols, such as a C3MA/CD bus type LAN or a token ring type LAN. In the figure, ■ (ID~], K) is the bridge, 2D~2
J is L A N, 3D-1 to 3J-1 are ST, A, B.
...O is an identifier given to each bridge (B I N
) is shown.

Each ST specifies B I N t&H for each communication frame, similar to the network shown in FIG. The function of delivering the communication frame from the bridge assigned the same BIN as the source BTN 48 to the bridge assigned the same BIN as the destination BTN 46 is as follows:
It depends solely on the function of each bridge, and is not concerned with the originating or receiving ST.

For example, ST3 connected to LAN2G
Consider the case where a frame is delivered from G-1 to 5T3D-1 connected to LAN2D. The communication path is, for example, Bridge IK, IG, ID, or Bridge I.
There are multiple combinations such as K, IF, and 10. Which route to select from among these multiple communication routes can be determined by providing each bridge with, for example, a routing table (detour table) for each destination BIN. This eliminates the need for each ST to know in advance what route the frame will be propagated.

When communicating from ST/3G-1 to 3D-1, 5T3G-1, which is the source 1, sends a message to 5A-BTN48, for example, “
M", DA-B TN46 is set to "A". In this case, to relay the communication frame from the bridge IK to the bridge ID, prepare the routing table shown in Fig. 7 for each bridge intervening on the way. do it.

5D, 5F, and 5 each have a bridge ID.

This is a routing table provided in IF and IK, and defines processing contents according to the values of 5A-BIN48 and DA/BIN46 in a communication frame.

According to this table, the communication frame transmitted from ST 3G-1 is M -K -H-r) -B -A
Reach ST 3D-1 via this route. Similarly, ST・3
The communication frame addressed to 3G-1 transmitted by D-1 reaches ST/3G-1 through the reverse route to that described above. In the latter case, for example, configure the routing table so that frames with DA-BIN46 of M are handled by Bridge 1G on LAN2E, so that the route is -M to A-B-E-I-. It's okay.

When relaying bridges in multiple stages like this, it is only necessary to appropriately set the BIN relayed by each bridge, and this setting and updating can be done manually depending on the failure or load, or it can be done automatically by a program. You may also do so. Note that, as a modification of the present invention, a method in which each bridge updates the 5A-BIN in the frame it relays may also be considered.

In the above embodiment, the BIN value is set for each connection point between the LAN and the bridge, but for example, each bridge has two
If there are only ports and the relay destination of frames received (copied) from one LAN is uniquely determined, it is sufficient to set one identifier for each bridge, that is, an identifier for each bridge.

〔Effect of the invention〕

According to the present invention, the communication frame is simple, and when a plurality of communication paths are provided between mutually connected LANs, addresses can be easily compared and verified at each relay bridge, thereby reducing the load on the bridge. You can configure a low-performance, high-performance network system.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a network consisting of multiple LANs to which the present invention is applied, FIG. 2 is a block diagram showing the internal configuration of a bridge, FIG. 3 is a block diagram of the internal configuration of a LAN communication adapter, and FIG. The figure shows the format of the communication frame, FIGS. 5A and 5B are flowcharts showing the operation of the bridge, FIG. 6 shows a modification of the network to which the present invention is applied, and FIG. FIG. 2 is a diagram for explaining a routing table prepared for each bridge in the network. 1 (IA, IB...) Nibridge, 2 (2
A, 2B...): LAN. 3 (3A-1 to 3J-1) Nisti John 46:DA
-BIN 48:5A-BIN 50: Message exchange unit 60: LAN communication adapter = 20-3ρ-23D-7'' - To the 7th fan of the 4th ward

Claims (1)

[Claims] 1. In a network system consisting of a plurality of local networks, a relay device interposed between the local networks, and a communication terminal connected to the local network, an identifier unique to each relay device in advance is assigned, and the communication terminal that is the source of the communication frame, in addition to the addresses of the communication terminal that is the source and the destination, a first identifier that specifies the relay device that performs the first relay of the communication frame; A second identifier that designates the relay device that performs the last relay is set in the communication frame, and each of the relay devices sets 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 relay destination local network according to the following. 2. Each relay device has a local network connected to it.
The identifier is assigned in correspondence with the connection port of the work, and the communication terminal that is the source of the communication frame is the connection port between the local network in which the communication terminal is included and the first relay device, and the reception destination. Item 1, characterized in that two identifiers specifying a connection port between a local network including a communication terminal and the last relay device are set in the communication frame as the first and second identifiers, respectively. Communication method between local networks described. 3. The communication system between local networks according to item 1 or 2, wherein in the network system, two or more relay devices are interposed in parallel between two local networks. 4. The source communication terminal sets the first identifier as a pair with the address of the communication terminal and the second identifier as a pair with the address of the destination communication terminal in the communication frame. 3. A communication system between local networks according to items 1 to 3, characterized in that: