JPH08274797A - Switching device for lan - Google Patents

Abstract

PURPOSE: To provide a switching device for a LAN which is reduced in packet loss. CONSTITUTION: When a packet is received by a port reception part 1, a receiving buffer storage part 2 informs an address filter part 6 of the storage address of the packet acquired from a receiving buffer 3 and the port number of the reception of the packet, and stores this packet in the said storage address of a data buffer 32. The address filter part 6 knows a port from which transmission is performed, informs a transmitting buffer storage part 4 of the storage address of this packet and information on the said port for the transmission, and transfers the packet to the port transmission part 5 of the port, thereby sending it to Ethernet. The transmitting buffer storage part 4 receives and sends the storage address back to the receiving buffer 3. A receiving buffer capacity decision part 7 decides the rest capacity of the receiving buffer 7 by monitoring the acquiring and resending operation of the storage address in the receiving buffer 3 and sends a jam signal out of the port transmission part 5 when the rest capacity becomes less than a specific value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a LAN switching device, and more particularly to an Ethernet communication device (especially HUB).

[0002]

2. Description of the Related Art Currently, LAN (Local Area)
Ethernet (Ethernet, a registered trademark of Xerox Co., Ltd.) is one of the methods widely used in the network. In Ethernet, as shown in FIG. 10, a collision occurs when the transmission from the terminal A to the terminal E and the transmission from the terminal B to the terminal D occur at the same time. This is an essential part of the Ethernet system, and it is said that only about 30% of the bandwidth of 10 Mb / s can be used due to the effect of this collision. In order to solve this, as shown in FIG. 11, a method of providing a switching device SW and switching Ethernet packets like a telephone exchange can be considered. This allows multiple transmissions simultaneously without collisions.

As a method for realizing this Ethernet switching method, "COMPUTER NETWO
RK SWITCHING SYSTEM "(US Pat. No. 5,274,631) has been proposed. As shown in FIG. 12, each port of the switching device SW is provided with a packet processor 91-97, and this packet processor 91-97 is proposed. High-speed switching is realized by providing a receiving buffer and selecting means for transmitting to which port, respectively, in the figure, 90 is a multiplexing logic unit (multiplex logic), 98 is a system processor, 99 is a network interface.

[0004]

However, in such a switching device SW, when the packet input is concentrated, the packets are accumulated in the receiving buffer, and the remaining capacity is exhausted, the packets input after that are processed. There was a problem that it disappeared without fail and packet loss occurred.

The present invention has been made in view of the above points, and an object thereof is to provide a LAN switching device in which packet loss is reduced.

[0006]

According to a first aspect of the present invention, there is provided a LAN switching device which receives a packet through a port connected to an Ethernet segment and buffers the packet, and a packet from the port receiving unit. Storage address for receiving the storage address of the packet from the reception buffer and transmitting it to the address filter unit, a reception buffer having a data buffer for storing packets by the reception buffer storage unit and a reception buffer pointer table indicating the storage address, and a reception buffer storage Based on the storage address information transmitted from the storage unit, the source address and destination address of the packet are read from the reception buffer, the destination port of the packet is determined, and the storage address and destination port of the packet are stored in the transmission buffer storage unit. Address filter part that transmits to Transfers the packet from the reception buffer to the port transmission unit of the transmission port to which the packet should be transmitted, based on the storage address of the packet and the destination port information from the transmission unit, and also transmits the transmission information from the transmission unit. The send buffer storage unit that returns the storage address of the packet in the receive buffer to the receive buffer pointer table with the difference between the buffer amount used by the receive buffer storage unit and the buffer amount returned by the send buffer storage unit. From the receiving buffer capacity determining unit for determining the remaining capacity of the receiving buffer, and a port transmitting unit configured to transmit the packet transferred from the receiving buffer through the port connected to the Ethernet segment, When the remaining capacity of the reception buffer becomes less than a predetermined value by the reception buffer capacity determination unit It is characterized in that it has from over preparative transmitting unit to jam signal is sent.

According to a second aspect of the present invention, in the LAN switching device of the first aspect, the port receiving unit and the port transmitting unit are provided for each port, and the other units are commonly provided for the entire device. It is characterized by having done.

[0008]

According to the present invention, when the packet is received by the port receiving unit, the receiving buffer storage unit uses the address stored in the packet acquired from the receiving buffer and the port number receiving the packet as an address filter. The packet is stored in the storage address of the data buffer while being taught to the department. The address filter unit should take out the source address and the destination address of the packet from the information of the storage address, search the destination address in its own address table, and send the packet to which port. To know Further, by registering the information of the source address and the receiving port in the address table, it is possible to know which port is connected to which terminal having the address. Next, the storage address of this packet,
It informs the transmit buffer store of which port it should send to. The transmission buffer storage unit transfers the packet from the storage address to the port transmission unit of the port to which the packet should be transmitted. The port transmitter transmits the packet to Ethernet. When the packet is transmitted from the port transmission unit, the transmission buffer storage unit returns the storage address to the reception buffer. The reception buffer capacity determination unit monitors the remaining capacity of the reception buffer by monitoring the operation of the reception buffer storage unit acquiring the storage address in the reception buffer and the operation of the transmission buffer storage unit returning the storage address in the reception buffer. If it is determined that the remaining capacity of the reception buffer is less than or equal to a predetermined value, a signal indicating that a jam signal is to be transmitted is output to the port transmission unit. The port transmitter that receives this signal sends a jam signal.

According to the invention of claim 2, claim 1
In the invention described above, by providing the reception buffer and the address filter unit so as to be shared by the entire apparatus, one large buffer is provided centrally in the entire apparatus, and each port P absorbs the asynchronism. A small buffer can be provided, the efficiency of use of the buffer is improved, and as a result, the buffer amount required for the entire device can be reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a LAN switching device according to an embodiment of the present invention. A port receiving unit 1 and a port transmitting unit 5 are provided for each port P corresponding to an Ethernet segment, and a reception buffer storage unit 2, a reception buffer 3, a transmission buffer storage unit 4, an address field unit 6, and a reception buffer capacity determination Part 7 is 1 for the entire device
It is provided as one shared. The port receiving unit 1 is provided for each port P to perform packet buffering. The port receiving unit 1 is connected to the port P corresponding to the Ethernet segment and is received by the receiving unit 11 and the receiving unit 11 which function as an interface. It comprises a port reception buffer 12 for storing packets from the terminal. The reception buffer storage unit 2 synchronizes a packet once stored asynchronously in the port reception buffer 12 and stores the packet in the reception buffer 3 in synchronization with the storage address of the packet in the reception buffer 3 and the reception port. The address filter unit 6 receives the reception buffer information such as the number and the packet size.
The receiving buffer information storage means 22 for storing the

By making the band from the receive buffer storage means 21 to the receive buffer 3 sufficiently larger than the band from the port receive buffer 12 to the receive buffer storage means 21, the port receive buffer 12 has a small buffer amount ( It is possible to store the packet in the reception buffer 3 without loss by the amount of buffer required to synchronize the incoming packet asynchronously with the operation of the reception buffer storage means 21.

The transmission buffer storage unit 4 includes the reception buffer 3
Buffer storage means 41 for storing the packet of the above in the port transmission section 5 based on the information from the address filter section 6.
When the packet is transmitted from the port transmission unit 5, the buffer return means 42 returns the storage address in the reception buffer 3 to the reception buffer pointer 31 in the reception buffer 3.

The port transmission unit 5 is an interface between a port transmission buffer 51 for storing packets to be transmitted and an Ethernet segment, and a transmission unit for transmitting the packets stored in the port transmission buffer 51 from the port P to the Ethernet. And 52.

The reception buffer 3 comprises a reception buffer pointer table 31 and a data buffer 32, and stores a packet input from each port P at a predetermined address of the data buffer 32 by a signal from the reception buffer storage unit 2. And is provided as a common one in the entire device. Therefore, all the packets input from each port P are stored in the data buffer 32 of the reception buffer 3. Further, the reception buffer pointer table 31 is provided in the reception buffer 3, and the storage address of the packet in the data buffer 32 is set. The reception buffer pointer table 31 has a ring structure as shown in FIG. 2, and the table from the start position BEGIN to the end position END is effective. In the figure,
PHEAD points to the beginning of an empty cell. The reception buffer 3 has a structure as shown in FIG. 3, and the reception buffer storage means 21 acquires an address for storage from the reception buffer pointer 31 and stores the packet at the address indicated by the designated PHEAD.

The address filter unit 6 takes in the port number at which the packet is received from the reception buffer information storage means 22 and the storage address in the data buffer 32 in the reception buffer 3, and based on this storage address, from the reception buffer 3 By reading only the source address and the destination address, an address table as shown in FIG. 4 is created. By referring to this table, it is possible to know which port P is connected to which device (terminal). Of.
Similar to the reception buffer 3, the address filter unit 6 is provided as one common unit throughout the device.

Here, the main processing of the address filter unit 6 will be described with reference to the flowchart shown in FIG. First,
The source address of the packet stored in the receiving buffer 6 is searched in the address table (# 61), and if not found, the address and the receiving port number are newly registered in the address table (# 62). Even if the source address is found, if the port number is different from the receiving port number registered in the address table,
Since it is considered that the device has moved and the connection port has been changed, the reception port number is re-registered at the port number (# 63). Further, processing equivalent to address learning of the bridge such as aging is performed. Next, it is searched whether the destination address is in the address table (# 64). When the destination address is not found, it is not possible to specify to which port the packet is to be transmitted, so all ports except the receiving port are set as the destination (# 65). When the destination address is found, the port number is compared with the receiving port number (# 66), and if different, the port number is designated as the destination (# 67). If the port number and the receiving port match, it means that the communication is on the same segment and it is not necessary to send it to another port. Therefore, the packet is deleted from the receiving buffer 6 and discarded (# 68).

Except when it is discarded by the address filter unit 6, when the destination port is determined, the address filter unit 6
Tells the transmission buffer storage unit 4 the storage address in the reception buffer 3 and the destination port number. The transmission buffer storage unit 4 transfers the contents of the packet from the reception buffer 3 to the port transmission buffer 51 in the port transmission unit 5 of the destination port. The port transmission unit 5 transmits the packet in the port transmission buffer 51 to the device (terminal) having the destination address through the transmission unit 52 which is an interface with the Ethernet segment. When the packet is sent,
The buffer return means 42 returns the storage address to the reception buffer pointer 31 and completes the transmission of one packet.

As shown in FIG. 6, the reception buffer capacity determination section 7 includes a reception buffer pointer acquisition monitoring means 71, a reception buffer pointer reply monitoring means 72, a buffer usage number counter 73, a buffer remaining amount warning capacity storage means 74, and a comparison. And a container 75. The reception buffer pointer acquisition monitoring means 71 monitors the buffer amount used by the reception buffer storage means 21 based on the reception buffer pointer (storage address) from the reception buffer information storage means 22 and information such as the packet size. A signal is output each time is used. The reception buffer pointer reply monitoring means 72 monitors the amount of buffer released from the information of the reception buffer pointer (storage address) returned by the buffer reply means 42, and outputs a signal every time the buffer is released. It has become so. The buffer usage number counter 73 counts down according to the output signal from the reception buffer pointer acquisition monitoring means 71 and counts up according to the output signal from the reception buffer pointer reply monitoring means 72. That is, the buffer usage number counter 73 outputs according to the buffer usage number. The buffer remaining amount warning capacity storage unit 74 stores a buffer remaining amount warning capacity indicating a value that packet loss may occur when the unused buffer amount decreases further. The comparator 75 compares the buffer remaining amount warning capacity previously stored in the buffer remaining amount warning capacity storage means 74 with the output of the buffer usage number counter 73, and the used buffer capacity is the buffer remaining amount warning capacity. When it exceeds, a signal indicating that a jam signal is to be transmitted is output to the port transmitter 5.

As shown in the flowchart of FIG. 7, the operation of the receiving buffer capacity determining section 7 is such that the capacity of the buffer in use, which is obtained from the difference between the used receiving buffer capacity and the released receiving buffer capacity, is the remaining buffer capacity. When the warning capacity is exceeded, a jam output command signal is output to the port transmitter 5.

The operation of this embodiment will be described below. In this embodiment, the case where the number of receptions is larger than that of transmissions will be described as an example. Now, the reception buffer pointer is set as shown in the reception buffer pointer table of FIGS. 8A to 8D, and the use state of the reception buffer is correspondingly set to FIGS. 9A to 9D. ). That is, when a packet is received in a state where the buffer area indicated by the pointer of PHEAD2 is used (FIG. 9A), the buffer area indicated by the pointer of PHEAD1 is used (FIG. 9B). , Then PH
The packet stored in the area of the buffer indicated by the pointer of EAD2 has completed transmission, and the pointer of PHEAD2 is released (FIG. 9 (c)). After this, if there is no packet to be transmitted, there is no pointer to be released, and packets accumulate in the receive buffer (FIG. 9 (d)). When the receiving buffer is in a state as shown in FIG. 9D and the capacity of the buffer being used exceeds the remaining buffer capacity, the jam output command signal is sent to the transmitting section 52 of the port transmitting section 5.
Output to. The transmitter 52 that has received the jam output command signal sends a jam signal to the terminal. The terminal receiving the jam signal delays the transmission timing according to the rules of the CSMA / CD method and then transmits.

As described above, according to the present embodiment, when packets are accumulated in the reception buffer 3, a jam signal is transmitted from the port transmission unit 5 to the terminal, and the packet transmission interval from the terminal is increased. Since the packet can be processed by the transmission buffer storage unit 4 while it is vacant, the reception buffer becomes vacant and the overflow state can be avoided.

Further, in this embodiment, one large buffer is provided in a concentrated manner rather than providing a large buffer for each port P, and each port P is provided with a small buffer for absorbing the asynchronism. Therefore, the use efficiency of the buffer is improved, and as a result, the buffer amount required for the entire device can be reduced.

[0023]

As described above, according to the first aspect of the present invention, in the LAN switching device, the reception buffer capacity determination unit determines the buffer amount used by the reception buffer storage unit and the transmission buffer storage unit. The remaining capacity of the receiving buffer is judged from the difference between the storage address and the returned buffer capacity.When the remaining capacity of the receiving buffer is below a specified value by the receiving buffer capacity judging section, a jam signal is sent from the port transmitting section. By doing so, while the packet transmission interval from the terminal that received the jam signal is open,
A packet can be processed by the transmission buffer storage unit and a LAN switching device with reduced packet loss can be provided.

According to the invention of claim 2, claim 1
In the invention described above, since the reception buffer and the address filter unit are provided so as to be shared by the entire apparatus, one large buffer is centrally provided in the entire apparatus and each port P absorbs the asynchronism. Therefore, it is sufficient to provide a small buffer to improve the efficiency of use of the buffer, and as a result, the buffer amount required for the entire device can be reduced and the device can be configured at low cost.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a LAN switching device of the present invention.

FIG. 2 is a structural diagram of a receive buffer pointer table according to the embodiment of FIG.

FIG. 3 is a structural diagram of a receive buffer according to the embodiment of FIG.

FIG. 4 is a schematic diagram showing an address table in the address filter unit according to the embodiment of FIG.

5 is a flowchart showing the operation of the address filter unit according to the embodiment of FIG.

FIG. 6 is a block diagram showing a specific example of a reception buffer capacity determination unit according to the embodiment of FIG.

FIG. 7 is a flowchart showing the same operation.

8 is a structural diagram of a reception buffer pointer table for explaining the operation of the embodiment of FIG.

FIG. 9 is a structural diagram of a reception buffer for explaining the operation of the embodiment of FIG.

FIG. 10 is an explanatory diagram showing a state of collision due to simultaneous transmission on Ethernet.

FIG. 11 is an explanatory diagram showing the principle of a switching device in Ethernet.

FIG. 12 is a block diagram of a conventional switching device in Ethernet.

[Explanation of symbols]

 1 Port Transmitter 2 Receive Buffer Store 3 Receive Buffer 4 Transmit Buffer Store 5 Port Transmitter 6 Address Filter 7 Receive Buffer Capacity Judge 11 Receive 12 Port Receive Buffer 21 Receive Buffer Storage 22 Receive Buffer Information Storage 23 Status adding means 31 Reception buffer pointer table 32 Data buffer 41 Transmission buffer storing means 42 Buffer returning means 43 Status returning means 51 Port receiving buffer 52 Transmitting section 71 Reception buffer pointer acquisition monitoring means 72 Reception buffer pointer reply monitoring means 73 Buffer usage number counter 74 buffer remaining amount warning capacity storage means 75 comparator P port

Claims (2)

[Claims] 1. A port receiving unit for receiving and buffering a packet through a port connected to an Ethernet segment, and a storage address of a packet from the port receiving unit is fetched from a receiving buffer and transmitted to an address filter unit. A reception buffer storage unit, a reception buffer having a reception buffer pointer table indicating a storage address and a data buffer for storing packets by the reception buffer storage unit, and a reception buffer based on the storage address information transmitted from the reception buffer storage unit Read the source address and destination address of the packet from the packet, determine the destination port of the packet, and transmit the storage address and destination port of the packet to the transmission buffer storage unit, and the packet from the address filter unit. Received based on the information of storage address and destination port The packet is transferred from the reception buffer to the port transmission unit of the transmission port where the packet should be transmitted, and the storage address of the packet in the reception buffer is returned to the reception buffer pointer table according to the transmission information from the transmission unit. A transmission buffer storage unit, a reception buffer capacity determination unit that determines the remaining capacity of the reception buffer from the difference between the buffer amount used by the reception buffer storage unit, and the buffer amount whose storage address is returned by the transmission buffer storage unit; And a port transmitting unit configured to transmit the packet transferred from the buffer through a port connected to the Ethernet segment, and the remaining capacity of the receiving buffer is below a predetermined value by the receiving buffer capacity determining unit. The feature is that a jam signal is sent from the port transmitter when it becomes LAN to
Switching device. 2. The LAN according to claim 1, wherein the port receiving unit and the port transmitting unit are provided for each port, and the other units are commonly provided for the entire device.
Switching device.