JPH09162916A - Switching hub - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change transmission rate so that a reception buffer is not overflowed. SOLUTION: A reception frame is temporarily kept in the reception buffer 121 and the frame is transferred between ports. A physical layer part 131 decides transmission rate with a terminal. When a buffer accumulation quantity monitor part 103 monitors frame accumulation quantity in the reception buffer and the frame accumulation quantity exceeds an upper limit which is previously set, a data transmission speed control part 104 gives an instruction to drop transmission rate to the physical layer part 131.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching hub to which networks having different transmission rates can be connected, and more particularly to a switching hub whose transmission rate can be changed so that a receiving buffer does not overflow.

[0002]

2. Description of the Related Art A switching hub for interconnecting terminals and networks has a plurality of ports, a communication control LSI for each port and a reception buffer for temporarily storing a reception frame, and a frame between the ports. A switching control unit that performs transfer control is provided. Further, it is provided with a physical layer section having an auto-negotiation function for determining a transmission rate with a terminal or the like connected to the port.

FIG. 3 shows a configuration of a conventional Ethernet switch as an example of a switching hub. The conventional Ethernet switch 300 includes a switching unit 102 that switches the connection of lines between ports and a switching control unit 10 that determines the destination of a frame and controls the transfer of the frame.
, 1 and reception buffers 121, ..., 12n (the last digit of the code corresponds to the number of ports; the same applies hereinafter) and communication control LSIs 111 ,.
11n and PHY131 which is an interface LSI,
, 13n. , 14n are terminals, and 151, ..., 15n are transmission lines.

, 13n confirm the link pulse with each of the connected terminals 141, ..., 14n to determine whether the transmission rate is 10 Mbit / s or 100 Mbit / s. It is equipped with an auto negotiation function.

An Ethernet switch 300 will be described with reference to FIG.
An outline of the operation will be described. Ethernet switch 300
Can communicate simultaneously among a plurality of ports as long as the ports do not overlap, and for example, the terminal 141 and the terminal 14n-1, and the terminal 142 and the terminal 14n can simultaneously communicate.

The operation of the conventional Ethernet switch will be briefly described with reference to FIG. FIG. 5 shows, as an example, a case where a frame is transferred from the port of the communication control LSI 111 to the port of the communication control LSI 11n. When the terminal 141 is connected to the port, the PHY 131 and the terminal 141
In addition to the transfer data, the data transmission speed is 10
A link pulse indicating whether it is Mbit / s or 100 Mbit / s is exchanged to determine the data transmission rate. Upon receiving the frame from the terminal 141, the communication control LSI 111 stores the frame in the reception buffer 121 and outputs the transfer request 51 to the switching control unit 101. Upon receiving the transfer request 51, the switching control unit 101 determines the destination, switches the switching unit 102 to set a path, and outputs the transfer permission 52 to the communication control LSI 111. Upon receiving the transfer permission 52, the communication control LSI 111 transfers the frame. Similarly, the switching control unit 101 checks whether or not there is a transfer request from the communication control LSI 131, ..., 13n for each port in a repeating order from the port number 1 to the maximum port number n. , Destination determination, switch path switching, and transfer permission issuance are performed only once, and the process proceeds to the next port.

Next, with reference to FIG. 6, the state in the reception buffer of each port and the order in which the transfer process is performed will be described.
In FIG. 6A, the reception buffers 121, 122,
..., 12m, ..., 12n-1, 61 shown in 12n
a, 62a, ..., 6ma, ..., 6n-1a, 6na and 61b, 62b, ..., 6mb, ..., 6n-1b, 6nb
Is a received frame. At this time, the transfer processing is performed for each port in a repeating order from the port number 1 to the maximum port number n, so that the frames to be transferred are arranged in the transfer order as shown in FIG. 6B. Become.

[0008]

In the above-mentioned conventional Ethernet switch 300, the transfer process of each port has the same priority, and the port number 1 to the maximum port number n are repeated one by one in order of repetition. Transfer processing is performed frame by frame. At this time, the transmission speed of a certain port is 1
If the transmission rate is set to 00 Mbit / s and the transmission rate of other ports is set to 10 Mbit / s, the transmission rate will be 10
0 Mbit / s port has a transmission rate of 10 Mbit / s
Since a frame having the same size as that of the port of 10 is received at a speed 10 times faster, a large number of received frames are accumulated in the reception buffer of the port having such a high transmission speed. For example, as shown in FIG. 6, reception frames 6mc, 6md, 6me, 6mf, 6m are stored in the reception buffer of the port 12m having a transmission rate of 100 Mbit / s.
g is accumulated, and the received frame may eventually overflow.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a switching hub capable of changing the transmission speed so that the receiving buffer does not overflow.

[0010]

In order to achieve the above object, the present invention has a plurality of ports, a communication control LSI for each port, and a reception buffer for temporarily storing a reception frame. In the switching hub equipped with a switching control unit that performs frame transfer control, and a physical layer unit that has an auto-negotiation function that determines the transmission rate with the terminal connected to the port, the frame in the receive buffer A buffer storage amount monitoring unit for monitoring the storage amount is provided, and when the frame storage amount exceeds a preset upper limit, a data transmission rate control unit for instructing the physical layer unit to reduce the transmission rate is provided. is there.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As an embodiment of the switching hub of the present invention, transmission speeds of 10 Mbit / s and 100 Mb
An Ethernet switch that interconnects a plurality of it / s Ethernet LAN segments will be described. This Ethernet switch has a port with a transmission rate of 10
In order to prevent the receive buffer of this port from overflowing even at 0 Mbit / s, a buffer storage amount monitoring unit that constantly monitors the frame storage amount in the receive buffer of each port of the Ethernet switch is provided, and the interface A data transmission rate control unit for instructing the PHY, which is an LSI, to switch the transmission rate is provided, and when the frame storage amount exceeds a preset upper limit, 100 Mb
The data transmission rate of the it / s port is 10 Mbit / s
It is designed to be pulled down to.

When the frame temporarily stored in the reception buffer of each port is transferred to the transmission buffer of the transfer destination port, the buffer accumulation amount monitoring unit monitors the frame accumulation amount in the buffer, and the frame of the buffer of the port of 100 Mbit / s If the accumulated amount exceeds a certain value, the data transmission rate control unit instructs the PHY of this port to switch the link pulse to that of 10 Mbit / s, and the data transmission rate between the port and the terminal is 10 Mbit. /
By lowering to s, it is possible to prevent the receiving buffer from overflowing.

FIG. 1 shows an Ethernet switch 10 of the present invention.
0 is a switching control unit 101 that determines the destination of a frame and controls the transfer of the frame in a switching unit 102 that switches the connection of lines between ports, and communication control LSIs 111, ..., 1 that configure each LAN port of the switch.
1n and reception buffers 121, ..., 12n for temporarily storing received frames, and buffer storage amount monitoring unit 1
03, transmission speed 10 Mbit / s and 100 Mbit
, Pn, which is an interface LSI having an auto negotiation function capable of dealing with / s.
And a data transmission rate control unit 104.

The buffer storage amount monitoring unit 103 has a transmission rate of 1
The frame accumulation amount of the reception buffer of the port of 00 Mbit / s is constantly monitored, and it is detected whether the frame accumulation amount exceeds a certain value (upper limit) and the data transmission rate control unit 104 is notified. . Further, it is configured to detect whether or not the frame accumulation amount is below a certain value (lower limit) and notify the data transmission rate control unit 104.

When the data transmission rate control unit 104 receives a notification from the buffer storage amount monitoring unit 103 that the frame storage amount of the reception buffer of the port having the transmission rate of 100 Mbit / s exceeds a certain value (upper limit). , The PHY of the port is instructed to switch the transmission rate from 100 Mbit / s to 10 Mbit / s. Further, when the buffer storage amount monitoring unit 103 notifies that the frame storage amount is below a certain value (lower limit), the transmission rate for the PHY of the port is switched from 10 Mbit / s to 100 Mbit / s. To instruct.

The data transmission rate with the terminal is 100 due to the auto negotiation function of the PHYs 131 to 13n.
It is set to either Mbit / s or 10 Mbit / s.

The operation of the Ethernet switch shown in FIG. 1 will be described.

FIG. 2 shows ports 1 and 2 of the Ethernet switch shown in FIG. That is, port 1
Corresponds to the reception buffer 121 and PHY 131, and port 2 corresponds to the reception buffer 122 and PHY 132. In each of the reception buffers 121 and 122 of the ports 1 and 2, the reception frame 6 waiting until the transfer is started.
1a, 61b, ..., 61n, 62a, 62b are stored. The buffer storage amount monitoring unit 103 of each of the reception buffers 121 and 122 always keeps track of the frame storage amount. Port 1 has a transmission speed of 100 Mbit
/ S high-speed Ethernet terminal 1 is connected, port 2 is connected to an Ethernet terminal 2 with a transmission speed of 10 Mbit / s, and data transmission is performed from the terminal 1 to the end 2 via the Ethernet switch. I shall.
In addition to data, the transmission speed of 100M between terminal 1 and port 1 is achieved by the PHY131 auto negotiation function.
It is assumed that the link pulse indicating the bit / s is exchanged and it is confirmed that the high speed Ethernet is used.

At this time, the buffer storage amount monitoring unit 103
As a result, when the amount of accumulated frames in the reception buffer 121 of port 1 exceeds a certain amount (upper limit), the data transmission rate control unit 104 causes the PHY 1 of port 1 to operate.
31 is instructed to switch the link negotiation for auto negotiation to transmit at 10 Mbit / s, and the data transmission rate between the port 1 and the terminal 1 is 100 Mbi.
Reduce from t / s to 10 Mbit / s.

On the contrary, the data transmission rate is 10 Mbit /
When the frame accumulation amount in the reception buffer 121 of the port 1 reduced to s becomes equal to or less than a certain amount (lower limit), the data transmission rate control unit 104 causes the PHY1 of the port 1 to
Stop the link pulse switching instruction to 31 and set the data transmission rate between port 1 and terminal 1 to 10 Mbit.
Return from / s to 100 Mbit / s.

[0021]

The present invention exhibits the following excellent effects.

(1) Since the receiving buffer storage amount monitoring unit and the data transmission rate control unit are provided and the frame storage amount of the receiving buffer is constantly monitored, and the data transmission rate is lowered according to the result, the transmission rate is high. It is possible to prevent the receive buffer of the port from overflowing.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an Ethernet switch showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating transmission rate control by the Ethernet switch of the present invention.

FIG. 3 is a configuration diagram of a conventional Ethernet switch.

FIG. 4 is a schematic explanatory diagram of an Ethernet switch.

FIG. 5 is an operation explanatory diagram of inter-port connection and transmission rate determination of a conventional Ethernet switch.

FIG. 6 is a diagram showing (a) a state in a reception buffer of each port and (b) a sequence in which a transfer process is performed in a conventional Ethernet switch.

[Explanation of symbols]

 101 switching control unit 103 buffer storage amount monitoring unit 104 data transmission rate control unit 111 to 12n communication control LSI 121 to 12n reception buffer 131 to 13n physical layer unit (PHY)

Claims (1)

[Claims] 1. A port having a plurality of ports, a communication control LSI for each port, a reception buffer for temporarily storing a reception frame, a switching control unit for performing frame transfer control between ports, and a port for each port. In a switching hub equipped with a physical layer section having an auto-negotiation function for determining the transmission rate with a connected terminal, etc., a buffer storage amount monitoring section for monitoring the frame storage amount in the reception buffer is provided. A switching hub, comprising: a data transmission rate control section for instructing the physical layer section to reduce the transmission rate when the accumulated amount exceeds a preset upper limit.