JP3152136B2 - Switching hub - Google Patents

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 speeds can be connected, and more particularly to a switching hub whose transmission speed can be changed so that a reception 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 ports. A switching control unit for performing transfer control is provided. Also, a physical layer unit having an auto negotiation function for determining a transmission speed with a terminal or the like connected to the port is provided.

FIG. 3 shows the 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 connection of a line between ports, and a switching control unit 10 that determines a destination of a frame and performs frame transfer control.
, 12n (the last digit of the code corresponds to the number of ports; the same applies hereinafter) and communication control LSIs 111,.
11n, PHY131 which is an interface LSI,
.., 13n. , 14n are terminals, and 151, ..., 15n are transmission lines.

The PHYs 131,..., 13n determine whether the transmission rate is 10 Mbit / s or 100 Mbit / s by confirming link pulses with the connected terminals 141,. It has an auto negotiation function that can perform

[0005] Referring to FIG.
An outline of the operation will be described. Ethernet switch 300
Can simultaneously communicate with a plurality of ports as long as the ports do not overlap. For example, the terminals 141 and 14n-1 and the terminals 142 and 14n can simultaneously communicate with each other.

The operation of the conventional Ethernet switch will be briefly described with reference to FIG. FIG. 5 shows an example in which a frame is transferred from a port of the communication control LSI 111 to a port of the communication control LSI 11n. When the terminal 141 is connected to the port, the PHY 131 and the terminal 141 are connected.
Between data transfer rate and data transfer rate
A link pulse indicating whether the transmission rate is Mbit / s or 100 Mbit / s is exchanged, and the data transmission rate is determined. When 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 a 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 determines whether there is a transfer request from the communication control LSIs 131,..., 13n for each port in the order of port number 1 to the maximum port number n. , Destination determination, switch unit path switching, and transfer permission issuance are performed only once, and the process proceeds to the next port.

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

[0008]

In the above-described conventional Ethernet switch 300, the transfer processing of each port has the same priority, and one port per port is repeated from port number 1 to the maximum port number n in order. The transfer process is performed frame by frame. At this time, if the transmission speed of a certain port is 1
When the transmission speed is set to 00 Mbit / s and the transmission speed of the other port is set to 10 Mbit / s, the transmission speed becomes 10 Mbit / s.
0Mbit / s port is 10Mbit / s transmission speed
Since a frame having the same size is received ten times faster than a port having the same size, 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, and 6m are stored in a reception buffer of a port 12m having a transmission speed of 100 Mbit / s.
g is accumulated, and the received frame may eventually overflow.

It is an object of the present invention to solve the above problems and to provide a switching hub whose transmission speed can be changed so that a reception 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, a reception buffer for temporarily storing a reception frame, and an A switching hub including a switching control unit that performs frame transfer control, and a physical layer unit that has an auto-negotiation function for determining a transmission speed with a terminal or the like connected to a port. 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 speed is provided. is there.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As an embodiment of the switching hub of the present invention, a transmission rate of 10 Mbit / s and 100 Mb
An Ethernet switch for interconnecting a plurality of it / s Ethernet LAN segments will be described. In this Ethernet switch, the transmission speed of a certain port is 10
Even in the case of 0 Mbit / s, in order to prevent the reception buffer of this port from overflowing, a buffer storage amount monitoring unit for constantly monitoring the frame storage amount in the reception buffer of each port of the Ethernet switch is provided. A data transmission rate control unit that instructs the PHY, which is an LSI, to switch the transmission rate is provided.
data transmission speed of 10 Mbit / s
To be reduced to

When a 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 amount of frame accumulation in the buffer, and the frame of the buffer of the 100 Mbit / s port buffer is monitored. 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 reduces the data transmission rate between the port and the terminal to 10 Mbit / s. /
By reducing to s, it is possible to prevent the reception buffer from overflowing.

FIG. 1 shows an Ethernet switch 10 according to the present invention.
Numeral 0 indicates to the switching unit 102 that switches the connection of the line between the ports, the switching control unit 101 that determines the destination of the frame and controls the transfer of the frame, and the communication control LSIs 111,.
, 12n for temporarily storing the received frame 1n and the received frame, and a buffer storage amount monitoring unit 1
03, transmission speed 10Mbit / s and 100Mbit
, PHY131,..., 13n, which are interface LSIs with an auto-negotiation function
And a data transmission rate control unit 104.

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

When the data transmission rate control unit 104 receives a notification from the buffer accumulation amount monitoring unit 103 that the frame accumulation amount of the receiving buffer of the port having the transmission speed of 100 Mbit / s exceeds a certain value (upper limit). The PHY of the port is instructed to switch the transmission speed from 100 Mbit / s to 10 Mbit / s. Also, upon receiving a notification from the buffer storage amount monitoring unit 103 that the frame storage amount has fallen below a certain value (lower limit), the transmission speed for the PHY of the port is switched from 10 Mbit / s to 100 Mbit / s. Is to be instructed.

Due to the auto-negotiation function of the PHYs 131 to 13n, the data transmission speed with the terminal is 100
It is set to either Mbit / s or 10 Mbit / s.

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

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

At this time, the buffer accumulation amount monitoring unit 103
When the frame storage amount in the reception buffer 121 of the port 1 becomes a certain amount or more (upper limit), the data transmission rate control unit 104
31 to switch the link pulsing for auto negotiation to transmit 10 Mbit / s, and to set the data transmission rate between port 1 and terminal 1 to 100 Mbi.
Reduce from t / s to 10 Mbit / s.

Conversely, the data transmission speed is 10 Mbit /
When the frame accumulation amount in the reception buffer 121 of the port 1 reduced to s becomes a certain amount or less (lower limit), the data transmission rate control unit 104
31 to stop the link pulse switching instruction, and reduce the data transmission speed between port 1 and terminal 1 to 10 Mbit.
/ S to 100 Mbit / s.

[0021]

The present invention exhibits the following excellent effects.

(1) A receiving buffer accumulation amount monitoring unit and a data transmission speed control unit are provided to constantly monitor the amount of frame accumulation in the reception buffer and reduce the data transmission speed based on the result, so that the transmission speed is high. It is possible to prevent the reception buffer of the port from overflowing.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an Ethernet switch according to 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 explanatory diagram of an operation for connection between ports and determination of a transmission speed of a conventional Ethernet switch.

6A is a diagram illustrating a state in a reception buffer of each port of the conventional Ethernet switch, and FIG. 6B is a diagram illustrating an order in which transfer processing is performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Switching control part 103 Buffer accumulation amount monitoring part 104 Data transmission rate control part 111-12n Communication control LSI 121-12n Receiving buffer 131-13n Physical layer part (PHY)

Claims (1)

(57) [Claims] 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 In a switching hub having a physical layer unit having an auto negotiation function for determining a transmission speed with a connected terminal or the like, a buffer storage amount monitoring unit for monitoring a frame storage amount in the reception buffer is provided. A switching hub, comprising: a data transmission rate control unit for instructing the physical layer unit to reduce a transmission rate when the storage amount exceeds a preset upper limit.