JP3288312B2 - LAN connection device with buffer capacity control function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a LAN connection apparatus having a buffer capacity control function for connecting a plurality of networks.

[0002]

2. Description of the Related Art A conventional technique relating to flow control in data transmission / reception aims at prompt recovery from a congestion state when a congestion state is detected. For example, for flow control standardized by IEEE802.3X of the American Institute of Electrical and Electronic Engineers, the format of a pause frame and the OP code of a pause command are defined. When the receiving side wants to stop transmission from the transmitting side, a control is performed such that a pause frame is transmitted to the transmitting side, and the transmitting side reads out the pause time in the OP code in the frame and stops the transmission for that time.

[0003] As a general method of using the buffer at this time, with regard to the allocation of the packet buffer capacity, either a method of uniformly allocating to all ports or a method of fixed allocation by initial setting or the like is used. Was.

As a method of dynamically changing the buffer, for example, as disclosed in Japanese Patent Laying-Open No. 4-51735, a function is provided for calculating the amount of received data to determine an increase in traffic. The size of the storage area for storing the received data can be dynamically changed based on the calculated value, thereby increasing the use efficiency of the buffer memory.

[0005]

However, a problem in the conventional method of using a buffer is that packets are easily discarded in a congested state. The reason is that since the packet buffer capacity is fixedly allocated, the transmission buffer queue allocated to the port quickly fills up when congestion occurs such as receiving pause frames. Sisters,
Even if a larger transmission frame is input, it is discarded in the apparatus.

Another problem with the method of dynamically changing the buffer is that, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 4-51735, it is difficult to calculate the amount of traffic by setting the number of received frames per predetermined time. And calculate the amount of traffic for each input / output interface based on the data length of the frame.) Even if the buffer memory is dynamically allocated based on this information, the appropriate buffer memory is used. That is not to say. The reason is that only the amount of data to be received is considered, and the correspondence with the transmission port is not considered. For example, in the case of IEEE802.3, there was only an interface having a communication speed of 10 Mbit / s as 10BASE before, but now 100BASE is 100BASE.
An interface with a communication speed of Mbit / s has appeared, and 1000BASE (Gigabit Ethernet)
An interface having a communication speed of 1 Gbit / s is being standardized. Further, communication modes such as full-duplex communication and half-duplex communication also affect the data transfer capability (data output throughput) of each interface. Such a high-speed interface naturally has many data transfer capabilities, and the full-duplex transfer capability is higher than the half-duplex transfer capability. Of course, a large number of packet buffers must be prepared for output packets to ports having a large transfer capacity. In other words, in order to increase the use efficiency of the buffer memory, it is necessary to manage not only the amount of received traffic but also the traffic in association with the destination port of the received data. The problem comes out. Also, Japanese Patent Application Laid-Open No. 4-51735 has a problem that it does not support the pause packet technique.

SUMMARY OF THE INVENTION An object of the present invention is to increase the efficiency of use of a buffer memory by recognizing a state in which traffic has increased due to the reception of a pause packet in a LAN-to-LAN connecting apparatus, and thereby dynamically controlling the allocation of packet buffers. Is to reduce the number of discarded packets.

[0008]

In order to achieve the above object, an inter-LAN connecting apparatus with a buffer capacity control function according to the present invention is provided with an inter-LAN connecting apparatus with a buffer control function having a plurality of ports connected to a network. In the above, when a pause frame is received via the port, stop means for stopping transmission on the port that has received the pause frame for a time specified by the pause frame,
While the transmission of the transmission frame is stopped by the stop unit, the transmission buffer dedicated to the port is used to determine the number of packets that can store the packet data of the transmission frame even if there is a transmission request of the transmission frame to be output to the port whose transmission is stopped. Against
The number of address areas of the transmission buffer queue dedicated to the port whose transmission has been stopped by notifying the notified number.
And increasing means for increasing the number only .

[0009]

[0010]

The present invention also provides a LAN connection apparatus having a buffer capacity control function, comprising: a pause frame for detecting a pause frame for each port in the LAN connection apparatus having a buffer control function provided with a plurality of ports connected to a network. A detection unit, a packet buffer unit having a plurality of data areas for temporarily storing packet data of the frame each time a frame is received via the port, a buffer capacity control unit for managing the packet buffer unit, The transmission buffer queue unit having a plurality of address areas for each port for storing a memory address of the data area for waiting for transmission when transmitting the packet data stored in the packet buffer unit through the port, The packet data is stored in the packet buffer unit. Each time the packet data stored in the packet buffer unit is read out by the buffer capacity control means and the route of the packet data is determined, the memory address of the data area in which the packet data is stored is changed to the route. An address search unit for notifying the buffer queue unit of the determined port;
A frame transmission control unit that transmits the packet data stored in the packet buffer unit for each port as a transmission frame, and when the pause frame detection unit detects a pause frame, the pause frame detection unit includes: Stop means for instructing a frame transmission control unit to stop transmission at the port receiving the pause frame for a stop time specified by the pause frame, wherein the buffer capacity control means transmits the frame by the stop means. When the packet buffer unit receives the packet data of the transmission frame to be output to the port whose transmission is stopped while the packet buffer unit is stopped, the packet buffer unit increases the number of the address area calculated from the free data area of the packet buffer unit by the stopping unit. An increase notification means for notifying the transmission buffer queue of the port The transmission buffer queue unit is characterized by having a increasing means for increasing the number of the address area and receives the number of the address areas by the increase notifying means.

Further, the transmission buffer queue unit includes abandoning means for abandoning the right to use the address area if the address area increased based on the notification means after the stop time elapses is unused. And

Further, when the address area increased based on the notifying means is used even after the elapse of the stop time, the transmission buffer queue unit is configured to store the increased address area when the transmission of the packet data is completed. And updating notification means for notifying the packet buffer capacity control means that the free address area has been updated while discarding the packet address.

[0014]

[0015]

[0016]

[0017]

Next, a first embodiment of the present invention will be described with reference to the drawings.

Referring to FIG. 1, three LANs (Local Area Network) are shown as an embodiment of the present invention.
rk) with an interface port connected to
The configuration diagram of the inter-AN connection device is shown. The LAN connection device includes ports 1, 2, 3 and a pause frame detection unit 1.
1, 21, 31 and frame transmission control units 12, 22, 3
2, transmission buffer queue units 13, 23, 33, packet buffer capacity control unit 4, and packet buffer unit 5.
And an address search unit 6.

Each of the three interface ports is provided with a pause frame detection unit, a frame transmission control unit, and a transmission buffer queue unit. For port 1, a pause frame detector 11, a frame transmission controller 12, and a transmission buffer queue 13 are provided. For port 2, a pause frame detector 21 and a frame transmission controller 2 are provided.
2 and a transmission buffer queue unit 23, a pause frame detection unit 31 and a frame transmission control unit 32
And the transmission buffer queue 33 correspond to each other.

When a pause frame detector of each port receives a pause frame based on the IEEE802.3X specification, the pause frame set in the pause frame is read out from each port, and a timer not shown in FIG. Set. Then, the timer is started, and a transmission stop signal is output to the frame transmission control unit of the port. At the same time, transmission stop information is output to the packet buffer capacity control means 4 to notify both of the transmission stop and the transmission stop time. The pause frame is standardized by IEEE802.3X, and includes a pause time indicating a time interval to stop.

The frame transmission controllers 12, 22, and 32
The transmission buffer queues 13 and 2 of the respective ports
The packet data stored in the packet buffer 5 is output to the port as a transmission frame based on the packet address information (the first memory address of the data area) of the packet buffer unit 5 accommodated in the packet buffer 3 or 33. When a transmission stop signal is input, transmission of frames during that period is stopped according to the specified transmission stop time.

The packet buffer capacity control means 4 has a management table (not shown in FIG. 1) for always managing which data area of the packet buffer section 5 is a free data area or a used data area. For this reason, when the free state of the data area is changed, the data area information is received from the packet buffer unit 5. The data area information in the management table is composed of an address section using the head memory address of the data area of the packet buffer section 5 as a key, a capacity section indicating a capacity, and a state section indicating a free / busy state. When the transmission of the frame (packet data) is completed at any of the ports, the data area in which the packet data has been stored is taken out of the packet data and becomes empty. If a frame is received at any port, the data area storing the packet data is in use.
Thus, every time the data area is updated, the data area information is input from the packet buffer unit 5, and the memory address and the capacity of the free data area are managed. When the transmission stop information at the time of detecting the pause frame from the pause frame detection units 11, 21, 31 is input, the transmission buffer queue units 13, 23 of the corresponding port (the port that received the pause frame) for which transmission is stopped. , 33 are notified of the number of address areas to be added based on the number of data areas additionally allocated so that the memory capacity for newly storing packet data is apparently expanded. At this time, the number of address areas to be added is calculated by the packet buffer capacity control means 4, and is controlled in such a manner as to satisfy the following equation (1), for example.

[0023]

(Equation 1)

Transmission buffer queue sections 13, 23, 33
Has a plurality of address areas in which the head memory address of the packet data stored in the packet buffer unit 5 can be specified. There is an extra address area in which newly fetched packet data can be additionally allocated so that overflow does not occur while transmission is stopped.

Next, the operation of the first embodiment of the present invention will be described with reference to FIG.

The handling of a pause frame will be described on the assumption that a pause frame is input to port 1. Therefore, the address area of the transmission buffer queue unit 13 is secured by the address buffer addition request from the packet buffer capacity control unit 4 accompanying the additional allocation of the data area.

In a normal communication state, the address areas are equally allocated to the transmission buffer queues 13, 23, and 33. Port 1 with increasing traffic
When the opposing device connected to the port detects a congestion state and transmits a pause frame toward the port 1 by flow control, the pause frame detection unit 11 transmits a transmission stop signal to the frame transmission control unit 12 and transmits a transmission stop signal to the packet buffer capacity control unit 4. The stop information is output to instruct the stop of the frame transmission and the transmission stop time.

In the normal state, the frame transmission control unit 12 stores the packet address information stored in the transmission buffer queue unit 13 (the head memory address of the data area in which the packet data of the frame to be transmitted is stored in the packet buffer unit 5). Then, the packet data stored in the data area of the packet buffer unit 5 is extracted based on the packet data, and is output to the port 1 as a transmission frame. When the transmission is completed, the packet data waiting to be transmitted is sequentially output as a transmission frame based on the packet address information in a round robin manner. When the transmission stop signal is input to the frame transmission control unit 12, the transmission of the frame during that period is stopped according to the transmission stop time. Note that the round robin method is a method for determining the order of transmission.
According to this method, when packet address information of a large number of packet data waiting for the transmission order is stored in the transmission buffer queue unit 13, packet data to be transmitted next is determined from the packet address information. When the transmission order is determined in this manner, the packet data is extracted from the packet buffer unit 5 based on the packet address information in the transmission buffer queue unit 13, and the transmission processing is performed by the frame transmission control unit 12.

In a normal communication state, when packet data is stored in the packet buffer unit 5, the address search unit 6 analyzes the packet data in accordance with the instruction of the packet buffer capacity control unit 4 to determine a route. ,
A write request for the memory address (the position where the analyzed packet data is stored) of the packet buffer unit 5 is issued to the transmission buffer queue unit 13 and further notifies the packet buffer capacity control unit 4 of the received packet data capacity. In addition,
The allocation capacity of the maximum address area to each transmission buffer queue unit 13 is determined, and allocation beyond this is not usually performed (transmission is accumulated in one port, and memory is So that communication on all ports is not stopped by using up all of them).

In the normal processing state, the packet buffer capacity control means 4 writes the packet data into the free data area of the packet buffer unit 5 upon receiving the notification of the frame reception from the port, and the packet data is received by the address search unit 6. Request analysis of packet data. Based on the analysis result from the address search unit 6, in the area of the value where the memory address matches the address part of the management table, the capacity is written to the capacity part, and the state part is rewritten from the vacant state to being used. On the other hand, when the transmission stop information is received from the pause frame detection unit 11 and an instruction of the transmission stop and the length of the stop time is received, the transmission buffer queue unit 13 can be allocated from the free data area of the packet buffer unit 5. The number of possible address areas is notified, and the address area of the transmission buffer queue unit 13 is increased by the notified number. That is, the data area of the packet buffer unit 5 in which the packet data is stored and the address area of the transmission buffer queue unit 13 are expanded beyond the normal allocation. If the transmission stop time is long, the amount of packet data waiting to be transmitted increases during that time, so that a large number of data areas and address areas are allocated (the wait time can be absorbed by taking a large amount). .

The transmission buffer queue unit 13 stores the head memory address notified from the address search unit 6 as packet data waiting to be transmitted in the memory address capacity of the free address area allocated in the initial setting (queuing). Do). When the transmission is completed, the address area is returned to the empty state, and the next address search unit 6 prepares for the next notification. If there is no free address area in the transmission buffer queue section 13, the transmission packet data is discarded. When the address area addition information is input from the packet buffer capacity control means 4, the transmission buffer queue 13
Can accommodate the packet data waiting for transmission in the added address area. In this way, when the address area for storing the packet address information is increased, it becomes possible to store a large amount of packet data waiting for transmission. If there is no packet data to be a transmission frame while transmission is stopped, the added address area is not used. If not used, after the transmission stop time of the additional address area has passed (according to the transmission stop release notification of the pause frame detection unit 31), the use right of the address area is relinquished. When the added address area is used, the packet buffer unit 5 notifies the packet buffer capacity control unit 4 that the transmission of the frame has been completed and the free address area has been updated.

The packet buffer unit 5 stores the packet data of the transmission frame at an address corresponding to each packet address information stored in the transmission buffer queue units 13, 23, and 33.

Next, a series of operations when the LAN connection apparatus receives a frame (packet data) will be described below.

In a normal communication state, when packet data is received, the packet buffer capacity control means 4 stores the packet data in an empty data area of the packet buffer unit 5. When the packet data is stored, the address search unit 6 reads out the packet data, determines the route of the packet data (in the example, the network connected to the port 1), and checks the destination port. The transmission buffer queue unit 13 is notified of the head memory address of the data area stored as the transmission frame. The transmission buffer queue unit 13 stores the head memory address if there is a free space in the assigned address area. When the route is determined, the packet data capacity (with the first memory address of the data area) is sent from the address search unit 6 to the packet buffer capacity control unit 4.
Then, the packet buffer capacity control unit 4 writes the used capacity of the data area (capacity part) and rewrites the data area to in use (state part) in the corresponding area (search using the value of the address part as a key) of the management table. To prepare for the storage of the next transmission data. The frame transmission control unit 12
The packet data is extracted from the packet buffer unit 5 based on the packet address information in the transmission buffer queue unit 13 and queued (queued), and transmission processing is performed.

Next, a series of operations when the LAN connection apparatus receives a pause frame from port 1 will be described below.

When the pause frame detector 11 receives the pause frame from the port 1, the timer sets the time specified by the pause frame to a timer, starts the timer, and sends a stop signal to the frame transmission controller 12 to send the stop information (stop signal). And stop time) are sent to the packet buffer capacity control means 4 respectively. The frame transmission control unit 12 that has received the stop signal stops the transmission processing until it receives a stop release signal from the pause frame detection unit 11. However, during this time, other ports receive packet data and perform route determination processing. Therefore, even in port 1 where transmission is stopped, memory allocation is added in preparation for storing packet data to be the next transmission frame. Need to be Therefore, when the transmission stop occurs due to the pause frame, the packet buffer capacity control unit 4 sends the packet buffer unit 5 to the transmission buffer queue unit 13 based on the transmission stop received by the pause frame detection unit 11 and the length of the stop time. Notifies the number of address areas to which a buffer that can be allocated can be added from the free data area. The transmission buffer queue unit 13 allocates the address area of the transmission buffer queue unit 13 from the normal allocation (the number of notified packets) so that packets can be stored in the packet buffer unit 5 even while transmission to the port 1 is stopped. Only by the amount). If the transmission stop time is long, the amount of packet data waiting to be transmitted during that time also increases, so that many address areas are allocated.

As described above, even if a transmission request from another port to a port for which transmission is stopped occurs while transmission from the port receiving the pause frame is stopped, transmission of an unused buffer is stopped. By dynamically allocating the size of the transmission buffer queue to each port so that it can be allocated to the transmission buffer of each port, the apparent capacity of the packet buffer was increased. Packets to be transmitted can be reduced.

Next, a second embodiment of the present invention will be described with reference to the drawings.

Referring to FIG. 2, the configuration differs from FIG. 1 in that an extended buffer queue unit 7 and an extended packet buffer unit 8 are added to FIG.

The extended buffer queue unit 7 and the extended packet buffer unit 8 are used only during transmission stop when receiving a pause frame. Therefore, when there is a transmission frame to the port whose transmission is stopped due to the pause frame, the allocation of the empty area in the packet buffer unit 5 and the address area in the transmission buffer queue units 13 to 33 as in the first embodiment. Does not perform the operation of adding.

Next, the operation of the second embodiment of the present invention will be described with reference to FIG.

First, a series of operations when the LAN connection apparatus receives a frame (packet data) will be described below.

In a normal communication state, when packet data is received, the packet buffer capacity control means 4 stores the packet data in a free data area of the packet buffer unit 5. When the packet data is stored, the address search unit 6 reads out the packet data, determines the route of the packet data (in the example, the network connected to the port 1), and checks the destination port. The transmission buffer queue unit 13 is notified of the head memory address of the data area stored as the transmission frame. The transmission buffer queue unit 13 stores the head memory address if there is a free space in the assigned address area. When the route is determined, the packet data capacity (with the first memory address of the data area) is sent from the address search unit 6 to the packet buffer capacity control unit 4.
Then, the packet buffer capacity control unit 4 writes the used capacity of the data area (capacity part) and rewrites the data area to be in use (status part) in the corresponding area (search using the value of the address part as a key) of the management table. To prepare for the storage of the next transmission data. The frame transmission control unit 12 extracts packet data from the packet buffer unit 5 based on the queued packet address information in the transmission buffer queue unit 13 and performs transmission processing. If the address search unit 6 determines that the packet is sent to a port other than the transmission stop port, the process is performed in the same manner as in normal communication, and the packet data in the packet buffer unit 5 is still stored.

Next, a series of operations when the LAN connection apparatus receives a pause frame from port 1 will be described below.

When the pause frame from the port 1 is received by the pause frame detection unit 11, the time specified by the pause frame is set in a timer and started, and a stop signal is sent to the frame transmission control unit 12 to send stop information (stop signal (stop signal)). And stop time) are sent to the packet buffer capacity control means 4 respectively. The frame transmission control unit 12 that has received the stop signal stops the transmission processing until it receives a stop release signal from the pause frame detection unit 11. However, during this time, the other ports receive packet data and perform route determination processing. Therefore, even in the transmission stop port, memory is added in preparation for storing packet data to be the next transmission frame. Need to be kept. The addition of this memory is performed by the extension packet buffer unit 8 and the extension buffer queue unit 7.
Only done by.

On the other hand, under the control of the packet buffer capacity control means 4 having received the transmission stop port and the transmission stop time, the address search section 6 performs route determination processing and performs a transmission stop port (for example, the connection to the defeat port 1). Each time it is determined that the packet data is to be transmitted to the network, the packet data of the packet buffer unit 5 is moved to the extended packet buffer unit 8 and the head address of the data area of the extended packet buffer unit 8 stored at this time is changed. The extension buffer queue unit 7 is notified. If the address search unit 6 determines that the packet is sent to a port other than the transmission stop port, processing is performed in the same manner as in normal communication, and the packet data in the packet buffer unit 5 is still stored. While the transmission is stopped, all the packet data to be transferred to the transmission stop port (port 1) is stored in the extended packet buffer unit 8. After receiving the pause frame and performing transmission stop processing, the frame transmission control unit 12 transmits packet data based on both the transmission buffer queue unit 13 and the extension buffer queue unit 7 when resuming transmission. It extracts and performs transmission processing.

In this manner, the packet buffer unit 5 used for normal communication processing is separated from the extended packet buffer unit 8 used when transmission is stopped by a pause frame, so that the packet buffer capacity control unit 4 manages the packet buffer unit 5. The range is small and the scale can be reduced. Also,
Since the capacity distribution between the packet buffer unit 5 and the extended packet buffer unit 8 can be determined, it can be set according to the environment in which the device is used. If the size of the packet buffer unit 5 used for normal communication is increased, an efficient data area can be used in a network environment in which pause frames hardly occur. In a network environment in which frames are highly likely to occur, the rate of frame discards due to congestion can be reduced.

As described above, the LAN according to the present invention
The inter-connection device can dynamically allocate the capacity of the transmission buffer queue to each port when transmission is stopped due to the reception of a pause frame based on IEEE802.3X. The transmission buffer queue is allocated to the transmission buffer queue, so that the capacity of the packet buffer can be apparently increased, so that the utilization efficiency of the buffer memory can be increased and the number of discarded frames can be reduced.

[0049]

The first effect is that the communication quality of packet data is improved. The reason is that the waiting time is absorbed by allocating an empty buffer, so that even if a congestion state occurs, if the congestion state is mild, the packet data is stored in the empty buffer and no discard occurs.

A second effect is that an increase in traffic immediately after recovery from the congestion state can be suppressed. The reason is that the amount of packet data discarded during the congestion state is reduced, and it is not necessary to control retransmission of the packet data discarded after recovering from the congestion state.

The third effect is that the memory capacity as hardware can be reduced. The reason is that an unused memory capacity can be used effectively according to the degree of load on each port, rather than a fixed and uniform memory capacity being allocated to all ports.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 1, 2, 3 ports 4 packet buffer capacity control means 5 packet buffer unit 6 address search unit 7 extended buffer queue unit 8 extended packet buffer unit 11, 21, 31 pause frame detection unit 12, 22, 32 frame transmission control unit 13, 23, 33 Transmission buffer queue section

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 12/44 H04L 12/46 G06F 13/00 H04L 12/28 H04L 12/56

Claims (4)

(57) [Claims] 1. An inter-LAN connection device with a buffer control function having a plurality of ports connected to a network, wherein when a pause frame is received via the port, the pause frame is transmitted for a time designated by the pause frame. Stopping means for stopping transmission on the received port; and transmitting the transmission frame even if there is a transmission request for a transmission frame to be output to the port whose transmission is stopped while transmission of the transmission frame is stopped by the stopping means. Number of packet data that can be stored in the dedicated transmission buffer for the port
The number of address areas of the transmission buffer queue dedicated to the port whose transmission has been stopped by notifying the notified number.
Buffer capacity control function LAN connecting device characterized by having an increasing means for increasing only. 2. A LAN connection apparatus with a buffer control function having a plurality of ports connected to a network, comprising: a pause frame detecting unit for detecting a pause frame for each port; and receiving a frame via the port. A packet buffer unit having a plurality of data areas for temporarily storing packet data of the frame; a buffer capacity control unit for managing the packet buffer unit; and a port for transferring the packet data stored in the packet buffer unit to the port. The transmission buffer queue unit having a plurality of address areas for storing the memory address of the data area for waiting for transmission when transmitting via the transmission port queue unit, and the packet data is stored in the packet buffer unit. The packet stored in the packet buffer unit Data is read out by the buffer capacity control means, and each time the route of the packet data is determined, the memory address of the data area in which the packet data is stored is stored in the buffer queue section of the port to which the route is determined. An address search unit for notifying, and a frame transmission control unit for transmitting the packet data stored in the packet buffer unit for each port as a transmission frame, wherein when the pause frame detection unit detects a pause frame, The pause frame detection unit includes a stop unit that instructs a frame transmission control unit to stop transmission at the port that has received the pause frame for a stop time specified by the pause frame, and the buffer capacity control unit includes: While the transmission of the frame is stopped by the stopping means, the packet When the packet unit receives the packet data of the transmission frame output to the port whose transmission is stopped, the increase number of the address area calculated from the free data area of the packet buffer unit is transmitted to the transmission buffer queue unit of the port which is stopped. A buffer capacity control function, comprising: an increase notifying means for notifying, and wherein the transmission buffer queue section has an increasing means for increasing the number of the address areas when the number of the address areas is received by the increase notifying means. With LAN connection device. 3. The transmission buffer queue unit further comprises : abandoning means for abandoning the right to use the address area if the address area increased based on the notification means after the elapse of the stop time is unused. Claim 2
A LAN connection device with a buffer capacity control function as described in the above. Wherein said transmission buffer queue unit, the stopping time has elapsed after said notification means the amount of address area fraction and increased transmission of the packet data is completed when the address area increases and used on the basis of 3. The LAN connection device with a buffer capacity control function according to claim 2 , further comprising an update notifying means for notifying the packet buffer capacity control means that the free address area has been updated while discarding the packet address.