JP2522155B2 - Repeater between local area networks - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is ISO8802-3.
Carrier detection multiple access system with collision detection function (CSMA / CD system) defined in (IEEE802.3)
The present invention relates to an inter-LAN relay device having a local area network (hereinafter referred to as LAN) interface unit and a line interface unit using the LAN, and a communication system for performing line-side buffer management and transmission / reception of the inter-LAN relay device.

[0002]

2. Description of the Related Art A conventional LAN relay device of this type will be described with reference to FIG.

As shown in FIG. 5, a conventional LAN relay device includes a LAN interface unit 1, a relay processing control unit 2,
The transmission buffer unit 34, the reception buffer unit 35, and the system interface 3 for connecting the line interface unit 10 in a bus shape.

The LAN interface unit 1 is ISO8
CSM specified in 802-3 (IEEE802.3)
This is a LAN interface for transmitting and receiving frames by using the LAN as a communication medium in the A / CD system.

Here, a frame is a set of data flowing on a transmission line, for example, ISO8803-3.
(IEEE802.3) specifies that a media access control frame (MAC frame) includes a destination address, a source address, data, etc. (ISO / IEC8802-3: 1990, ANSI / IEEE802.3-199).
0th Edition, Information Processing System-Local Area Network-, Part 3: Carrier Detection Multiple Access Method with Collision Detection Function and Physical Layer Specification (Information Processing)
Systems -Local Area Networks-, Part3: Carrier Sens
e MultipleAccess with Collision Detection method a
nd Physical Layer Specifications), pp.33-37).

The relay processing control unit 2 refers to the destination address information of the frame received by the LAN interface unit 1 from the LAN transmission line 22, and if it is a frame to be relayed, it is sent to the transmission buffer unit 34 via the system bus 3. Store. Then, the frames are sent to the line 1 via the line interface unit 10 in the order in which they are stored in the transmission buffer unit 34.
Send to 9. Further, the frame received by the line interface unit 10 from the line is stored in the reception buffer unit 35 via the system bus 3. Then, the frames are transmitted to the LAN transmission line 22 via the LAN interface unit 1 in the order of being stored in the reception buffer unit 35.

Here, the relay processing control unit 2 has a local address table, and determines whether to relay to the line 19 side based on this address information. As such a conventional LAN relay device, for example, there is one defined as a media access control bridge (MAC bridge) in IEEE 802.1. It is also possible to have a route control table in the relay processing control unit 2 and to have a function of translating the received destination address for another network. A LAN relay device having such a function is disclosed in, for example, the document “Murai / Kusumoto:“ TCP / IP Network Construction Vol.
1-Principle, Protocol, Architecture- ", Kyoritsu Shuppan (Douglas E. Comer:" Internetworking with TCP / I
P Vol.1: Principles, Protocols, and Architecture ",
Prentice Hall (Dec. 1991)) ”.

[0008]

The above-mentioned conventional LAN
Since the relay device transmits the frames to the line in the order of arrival, when the number of frames flowing through the line increases, the number of frames waiting for transmission increases in the device. Therefore, when terminals connected to two LANs communicate with each other via a LAN relay device, a frame transmitted from a terminal connected to one LAN reaches a partner terminal of the other LAN. The arrival time becomes long, and a transmission timeout often occurs before a response frame, which is a response from the partner terminal, is received. At this time, the response frame received from the partner terminal after the transmission time-out is discarded, and there is a problem that the frame needs to be retransmitted.
Also, when a frame with a relatively long data length is transmitted on the line, the transfer of another frame with a relatively short data length is delayed until the transmission of this frame is completed, and the arrival time of the short frame becomes longer. There is a problem that it will end up. This is particularly noticeable when the communication speed of the line is relatively low.

[0009]

A relay device between local area networks according to the present invention is installed between a local area network transmission line for transmitting variable length frames and a line, and data between the local area networks via the line. In a relay device between local area networks for relaying transfer, a decomposing means for decomposing a variable length frame received from the local area network into a plurality of fixed length frames, and a fixed length frame decomposed by the decomposing means for the variable length frame. A plurality of transmission entries to be stored for each of the plurality of transmission entries, a frame storage identification section provided corresponding to each of the plurality of transmission entries, and indicating that there is a fixed length frame to be transmitted in the corresponding transmission entry, Corresponding to each transmission entry of The frame number storage means for storing the number of the fixed length frame to be transmitted in the bird, and the frame storage identification unit selects and selects one from the transmission entries indicating the existence of the fixed length frame. Selection means that repeats this selection so that the transmission entries to be circulated, and the contents of the frame number storage means corresponding to the transmission entry selected by the selection means are updated and stored in the transmission entries selected by the selection means. Of the fixed length frames, the one designated by the frame number storage means is added with a final frame identifier indicating the final frame and an entry number, and the fixed length frame with the final frame identifier and the entry number is added to the line. Sending means for sending out, and corresponding to the plurality of sending entries, receiving from the line When a plurality of receiving entries that store a fixed-length frame for each entry number added to the fixed-length frame and a fixed-length frame indicating that the final frame identifier is the final frame are stored in the receiving entry And an assembling means for generating a variable length frame from the fixed length frame stored in the reception entry and sending it to the local area network.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a LAN relay device of the present invention will be described in detail with reference to the drawings.

Referring to FIG. 1, in one embodiment of the present invention, the LAN interface unit 1 includes a LAN transmission line 2
2 is an interface unit for transmitting and receiving frames using the communication medium. The transmission buffer unit 4 is a buffer for temporarily holding a frame when the frame is transmitted from the LAN transmission line 22 side to the line 19 side. The reception buffer unit 5 is a buffer for temporarily holding a frame when the frame is received from the line 19 side to the LAN transmission line 22 side. The relay processing control unit 2 is a control circuit that manages the buffers of the transmission buffer unit 4 and the reception buffer unit 5. The divided frame storage unit 7 is a buffer for temporarily holding a divided frame of the transmission buffer unit 4. The assembly frame storage unit 8 is the line 1
This is a buffer for temporarily holding the divided frames received from the 9 side when assembling them. The transmission / reception buffer number control unit 6 sets an upper limit value of the number of buffers for storing frames in the transmission buffer unit 4, the reception buffer unit 5, the divided frame storage unit 7, and the assembled frame storage unit 8 so that overflow does not occur. It is a circuit to control. The divided assembly control unit 9 is a control circuit that manages the buffers of the divided frame storage unit 7 and the assembly frame storage unit 8.

First, the LAN interface unit 1 is L
When the frame is transmitted from the AN transmission line 22 side to the line 19 side, the frame received from the LAN transmission line 22 is sent to the system bus 3 under the control of the relay processing control unit 2. Further, the LAN interface unit 1 transfers the frame on the system bus 3 to the relay processing control unit 2 when receiving a frame from the line 19 side to the LAN transmission line 22 side.
It is sent to the LAN transmission line 22 under the control of.

When transmitting a frame from the LAN transmission line 22 side to the line 19 side, the relay processing control unit 2 refers to the destination address information of the frame received by the LAN interface unit 1 from the LAN transmission line 22, If the frame is to be relayed, it is stored in the transmission buffer unit 4 via the system bus 3. Further, when receiving a frame from the line 19 side to the LAN transmission line 22 side, the relay processing control unit 2 transmits the frame stored in the reception buffer unit 5 via the LAN interface unit 1 to the LAN transmission line. It has a function to send to 22. At this time, the relay processing control unit 2 arbitrates the frame transmission operation and the frame reception operation so that the system bus 3 does not collide with each other.

The transmission / reception buffer number control unit 6 sets the upper limit values of the number of buffers that can be stored in the transmission buffer unit 4, the divided frame storage unit 7, the reception buffer unit 5, and the assembly frame storage unit 8, respectively, and these upper limits are set. Monitor and control so that it does not exceed the value. The upper limit of the number of buffers is set in the transmission / reception buffer number control unit 6 when the system is started up. Further, the transmission / reception buffer number control unit 6 notifies the division / assembly control unit 9 of the number of transmission / reception buffers in these buffers.

The divided frame storage unit 7 divides the variable-length frame stored in the transmission buffer unit 4 into fixed-length frames (divided frames), and the divided frame storage unit 7
Hold in empty entry of. After that, the transmission buffer unit 4
Releases the entry in which the frame in was stored.

The assembly frame storage unit 8 holds the divided frames from the line 19 side. Then, after the divided frames are assembled into the original variable-length frame, the assembled frame is transferred to the reception buffer unit 5, and the stored entry in the assembled frame storage unit 8 is released.

The divided assembly control unit 9 transmits the divided frames stored in the divided frame storage unit 7 to the line 19 via the line interface unit 10 according to the number of transmission / reception buffers notified from the transmission / reception buffer number control unit 6. To do. After the transmission of the divided frame is completed, the stored entry in the divided frame storage unit 7 is released. The divided assembly control unit 9 also stores the divided frame received from the line 19 via the line interface unit 10 in the assembled frame storage unit 8. Line 1 here
9 can perform bidirectional transfer at the same time (full duplex)
Assuming that, the transmission and reception of the frame by the division and assembly control unit 9 can operate simultaneously.

FIG. 2 is a frame storage configuration diagram of the transmission buffer unit 4, the reception buffer unit 5, the divided frame storage unit 7, and the assembled frame storage unit 8.

Referring to FIG. 2-a), the transmission buffer unit 4 and the reception buffer unit 5 each identify a buffer for storing a frame therein and whether or not a frame is stored for each entry of this buffer. Frame identifier 11 of. Further, referring to FIG. 2B, the divided frame storage unit 7 includes a buffer for storing divided frames therein, a frame storage identifier 12 and a transmission end divided frame number identifier 13 for each entry of this buffer.
have. Referring to FIG. 2C, the assembled frame storage unit 8 has a buffer for storing divided frames therein, and a frame storage identifier 14 and a reception end divided frame number identifier 15 for each entry of this buffer. In addition,
When the value of the frame identifiers 11, 12, and 14 is 1, it indicates that the frame is stored in the corresponding buffer entry, and when the value is 0, it indicates that the corresponding buffer entry is empty. Further, the values of the transmission end divided frame number identifier 13 and the reception end divided frame number identifier 15 hold the frame numbers of the divided frames for which the transmission and the reception are finally ended on the line 19 side in the corresponding buffer entries. In FIG. 2-a), the value of the transmission end divided frame number identifier 13 of the first entry is 2, that the transmission is completed up to the second frame of the first entry, and then the third frame. This indicates that the frame will be transmitted. Similarly, the value of the transmission end divided frame number identifier 13 of the second entry is 1 and the transmission of the first frame of the second entry is completed, and the second frame is transmitted next. It shows that it is planned. Further, since the frame storage identifier 12 of the third entry is 0, it indicates that the third entry is an empty entry.

Next, the transmission buffer unit 4, the reception buffer unit 5, the divided frame storage unit 7, and the assembled frame storage unit 8
The internal operation will be described with reference to FIGS. 1 and 2.

When storing the frame received via the LAN interface unit 1 in the transmission buffer unit 4, the relay processing control unit 2 sets the frame storage identifier 11 of each entry in the transmission buffer unit 4 in ascending order of the entry number. If a value of 0 is found by searching, the frame is stored in the buffer corresponding to the entry. Then, at this time, the value 1 is written in the frame identifier 11 of the corresponding entry in the transmission buffer unit 4. Further, when transferring the frame of the reception buffer unit 5 to the LAN transmission line 22, the relay processing control unit 2 searches the values of the frame storage identifier 11 in the reception buffer unit 5 in ascending order of the entry numbers, When the entry having the value of 1 is found, the frame stored in the buffer corresponding to the entry is transferred to the LAN transmission line 22 via the LAN interface unit 1. Then, after this transfer is completed, the value 0 is written in the frame identifier 11 of the corresponding entry in the reception buffer unit 5.

Next, in the transmission buffer unit 4, the value of the frame storage identifier 11 is searched in ascending order of the entry number, and when an entry having this value of 1 is found, it is stored in the buffer corresponding to that entry. Is transferred to the buffer having the same entry number in the divided frame storage unit 7, and the frame storage identifier 12 of this entry is transferred.
The value of is 1. At this time, the value of the frame storage identifier 11 of the entry stored in the transmission buffer unit 4 is set to 0.
And Further, the divided frame storage unit 7 divides and holds the transferred frame based on a predetermined frame length set at system startup. At this time, with respect to the final frame of the divided frames, an identification flag indicating that it is the final frame is set as described later.

The divided assembly control unit 9 searches the value of the frame storage identifier 12 of each entry in the divided frame storage unit 7, and when an entry having this value of 1 is found, the corresponding transmission end divided frame number The value 1 is added to the identifier 13. Then, the divided frame having the frame number indicated by the addition result value is transmitted to the line 19 via the line interface unit 10. Here, the order in which the frame storage identifier 12 of the divided frame storage unit 7 is searched is, for example, when there are three entries, the first entry, the second entry, and the third entry.
For example, the entry and the first entry are ordered so that one divided frame is circulated every time it is transmitted. After the transmission of the final divided frame is completed, the value 0 is written in the frame storage identifier 12 and the transmission end divided frame number identifier 13 of the corresponding entry.

Further, the division assembly control section 9 extracts the entry number to be stored from the division frame received from the line interface section 10 as described later, and the value of the reception end division frame number identifier 15 of this entry. The value 1 is added to. Then, using the addition result value as a frame number, the divided frame is stored in the buffer of the corresponding entry. If the frame to be stored is the final frame, the value 1 is written in the frame storage identifier 14 after the storage operation is completed.

In the assembly frame storage unit 8, the internal frame storage identifier 14 is searched in ascending order of the entry number, and when an entry having this value of 1 is found, the frame of the buffer corresponding to that entry is received in the reception buffer. The data is transferred to the buffer having the same entry number of the unit 5 and the value 1 is written in the frame storage identifier 11 of the same entry in the reception buffer unit 5. After the storage in the reception buffer unit 5 is completed, the value 0 is written in the corresponding frame storage identifier 14 and the reception end divided frame number identifier 15 in the assembly frame storage unit 8, respectively.

Next, the operation of the divided assembly control unit 9 when transmitting and receiving the divided frames via the line interface unit 10 will be described.

FIG. 3 shows a format structure of a divided frame flowing on the line 19. Referring to FIG. 3, the divided frame flowing on the line 19 is the entry number 16,
It is composed of a final frame identifier 17 and divided frame data 18. As will be described later, the entry number 16 and the final frame identifier 17 are given by the division and assembly control unit 9. Further, the divided frame data 18 stores a divided frame received from the LAN transmission line 22.

When transmitting the divided frame to the line 19 side, the divided assembly control unit 9 sets the entry number in the divided frame storage unit 7 of the divided frame to be transmitted as the entry number 16 of the divided frame. Further, a value obtained by adding 1 to the value of the transmission end divided frame number identifier 13 indicated by the entry number is set as a frame number, and the data held at the position indicated by the frame number is set as the divided frame data 18 of the divided frame. Further, the final frame identifier 17 of the divided frame is set to the value 1 if the frame is the final frame, and is set to the value 0 otherwise. The divided frame in which these values are set is transmitted to the line 19 via the line interface unit 10.

Upon receiving the divided frame from the line 19, the divided / assembled control unit 9 stores the divided frame data 18 in the assembled frame storage unit 8 using the entry number 16 of the received divided frame as the entry number. At this time, the value obtained by adding 1 to the reception end divided frame number identifier 15 of the corresponding entry in the assembled frame storage unit 8 is used as the frame number. When the final frame identifier 17 of the received divided frame has the value 1, the frame storage identifier 14 of the corresponding entry in the assembled frame storage unit 8 is set to the value 1.

Next, an embodiment of a communication system constructed by using the LAN relay device of the present invention will be described with reference to FIG.

Referring to FIG. 4, the LAN relay device 20 and the terminals 25 and 26 are connected in a bus form via the LAN transmission line 23 to construct one LAN, and the LAN relay device 21 and the terminals 27 and 28 are connected. LAN transmission line 2 in the form of a bus
Connect via 4 to build another LAN transmission line. The two LANs arranged at relatively long distances are connected to each other through a line 19 to a LAN relay device 20 and a LAN relay device 21.
By connecting and, it becomes possible to communicate with each other.

Next, communication between terminals connected to different LAN transmission lines 23 and 24 will be described.

Here, it is assumed that the terminals 25 and 27 are communicating, and at the same time, the terminals 26 and 28 are communicating. Further, it is assumed that the communication between the terminals 25 and 27 is relatively frequently transmitting and receiving a frame having a long data length, and the communication between the terminals 26 and 28 is a frame having a short data length with an interval. Suppose you are sending and receiving. Here, the terminal receiving the frame transmits a short response frame indicating that the frame has been received to the partner terminal, and the terminal receiving the response frame transmits the next frame.

At this time, the LAN relay device 20 makes the terminal 25
Even if a frame having a long data length transmitted from the terminal 26 is being transmitted to the line 19, a frame having a short data length or a short response frame transmitted from the terminal 26 is divided and transferred in the line, and thus is kept waiting. Without being received, the LAN relay device 21 receives the data after a time proportional to the data length.

[0035]

As described above, according to the present invention, if the data length transmitted / received by each terminal is known, the time to reach the partner terminal is uniquely determined, and the response frame is transmitted after transmitting the frame at each terminal. The time interval until reception can be estimated. As a result, during communication between terminals, it is possible to prevent frames from being accumulated in the inter-LAN relay device and causing a transmission timeout, and also to prevent response frames from being transmitted on the LAN after the timeout. . Then, the frames in the transmission buffer section are time-divided and transmitted to the line, so that the retention times of the transmission-waiting frames in the transmission buffer section are averaged, so that the retention time of the entire system can be shortened. Also, a long frame is followed by a short frame on the LAN.
When receiving from the side and transmitting to the line side, the transmission of the short frame can be completed first without waiting for the completion of the transmission of the long frame.

[Brief description of drawings]

FIG. 1 is an internal configuration diagram of a LAN relay device of the present invention.

FIG. 2 is a frame storage configuration diagram of a transmission buffer unit, a reception buffer unit, a divided frame storage unit, and an assembled frame storage unit of the LAN relay device of the present invention.

FIG. 3 is a divided frame format on a line of the LAN relay device of the present invention.

FIG. 4 is a configuration diagram of a communication system including a LAN relay device of the present invention.

FIG. 5 is an internal configuration diagram of a conventional LAN relay device.

[Explanation of symbols]

 1 LAN interface unit 2 Relay processing control unit 3 System bus 4,34 Transmission buffer unit 5,35 Reception buffer unit 6 Transmission / reception buffer number control unit 7 Divided frame storage unit 8 Assembly frame storage unit 9 Divided assembly control unit 10 Line interface Part 11, 12, 14 Frame storage identifier 13 Transmission end division frame number identifier 15 Reception end division frame number identifier 16 Buffer number 17 Final frame identifier 18 Division frame data 19 Line 20, 21 LAN relay device 22, 23, 24 LAN transmission line 25, 26, 27, 28 terminals

Claims (1)

(57) [Claims] 1. A relay device between local area networks, which is installed between a local area network transmission line for transmitting a variable length frame and a line, and relays data transfer between the local area networks via the line, Decomposing means for decomposing the variable length frame received from the area network into a plurality of fixed length frames, a plurality of transmission entries for storing the fixed length frames decomposed by the decomposing means for each of the variable length frames, and a plurality of these transmissions. Provided for each of the entries,
A frame storage identification section that indicates that a fixed-length frame to be sent is present in the corresponding transmission entry, and a fixed-length frame that is provided corresponding to each of the plurality of transmission entries and that is sent out of the fixed-length frame in the corresponding transmission entry. A frame number storage means for storing the number of the one to be output, and one of the transmission entries in which the frame storage identification section indicates the existence of the fixed-length frame, and the selected transmission entry circulates. The selection unit that repeats this selection and the contents of the frame number storage unit corresponding to the transmission entry selected by the selection unit are updated, and the frame number of the fixed length frames in the transmission entry selected by the selection unit is updated. The final frame identifier and the entry number indicating the final frame are stored in the storage instruction. In addition, a sending means for sending a fixed length frame to which the final frame identifier and the entry number are added to the line, and a fixed length frame provided corresponding to the plurality of transmission entries and received from the line. When a plurality of reception entries are stored for each entry number added to the long frame and a fixed length frame indicating that the last frame identifier is the last frame is stored in the reception entry, the fixed length frame is stored in the reception entry. Assembling means for generating a variable length frame from the fixed length frame and sending it to the local area network.