JPH09149068A - Switching hub - Google Patents

Abstract

PROBLEM TO BE SOLVED: To select the efficient frame transfer mode in response to a state of a network. SOLUTION: A transfer mode decision means 101 monitors the frequency of occurrence of errors of a port and the cut through system or the store and forward system is adopted for a frame transfer mode depending on the frequency of occurrence of the errors. When the frequency of occurrence of the errors is low, the error check is omitted to reduce a transfer delay time. When the frequency of occurrence of the errors is high, transfer of undesired frames is avoided by error check.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching hub that transfers frames between ports, and more particularly to a switching hub that can select an efficient frame transfer mode according to the network conditions.

[0002]

2. Description of the Related Art A hub used in a network has a plurality of ports for connecting terminals and transfers frames between the ports. The hub has a switching hub.

A normal hub (repeat hub) transfers a frame arriving at one port to all the other ports, whereas a switching hub determines a destination MAC address in the frame. That M
When the AC address is unicast, the frame is transferred only to the port to which the terminal to which the MAC address is set is connected.

There are a cut-through method and a store-and-forward method as a method (frame transfer mode) for the switching hub to transfer a frame.

The cut-through method extracts only the destination address at the beginning of the frame without holding the contents of the frame in the internal memory and immediately transfers the frame to the port according to the destination address.

On the other hand, in the store-and-forward method, the contents of the frame are temporarily held in the internal memory, the error of the frame is checked, and then the frame is transferred to the port according to the destination address.

When a switching hub is provided, a switching hub having one of these frame transfer modes is selected.

[0008]

Comparing the frame transfer modes described above, in the case of the cut-through method, since the frame is not held in the internal memory, the transfer delay time can be very short. However, since no error check is performed on the frame, an unnecessary frame in which an error has occurred is transferred. On the other hand, in the store-and-forward method, on the contrary, an unnecessary frame in which an error has occurred is not transferred, but the frame is temporarily held in the internal memory, so the transfer delay time becomes large.

As described above, the cut-through method and the store-and-forward method have the opposite features and problems.

Therefore, an object of the present invention is to solve the above problems and to provide a switching hub capable of selecting an efficient frame transfer mode according to the network condition.

[0011]

To achieve the above object, the present invention monitors the error occurrence frequency of a port in a switching hub having a plurality of ports and performing frame transfer between the ports, and the error occurrence is monitored. Transfer mode switching means is provided for switching the frame transfer mode between the cut-through method and the store-and-forward method according to the frequency.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the embodiment of the present invention, a switching hub is capable of executing both cut-through type and store-and-forward type transfer modes. Further, a transfer mode switching means for constantly monitoring (monitoring) the error occurrence frequency of the port and switching the frame transfer mode between the cut-through method and the store-and-forward method according to the error occurrence frequency is provided. The error occurrence frequency is obtained by dividing a predetermined time, checking the number of error frames generated during this time, and calculating the error frame count / time. When the error occurrence frequency is smaller than a certain value, the frame is transferred by the cut-through method. That is, since the rate of error occurrence is low, error checking is omitted, and the transfer delay time is exclusively shortened. On the contrary, if the error occurrence frequency is higher than a certain value, the frame is transferred by the store-and-forward method. That is, since the rate of error occurrence is high, unnecessary frame transfer is eliminated by error checking. In this way, by automatically switching the frame transfer mode depending on the error occurrence state, efficient frame transfer according to the network condition is realized.

FIG. 1 shows the structure of a switching hub according to the present invention. The switching hub 106 has a plurality of ports 105 to which terminals are connected, and a cut-through type transfer means 10 for providing a cut-through type frame transfer mode.
4 and a store-and-forward type transfer means 10 for providing a store-and-forward type frame transfer mode
3, a switch 102 for switching between these frame transfer modes, a monitor section (transfer mode determination means) that detects an error occurrence of a frame, observes the error occurrence frequency, and determines the frame transfer mode according to the error occurrence frequency. ) 101 and are provided.

Although not shown, the switching hub 106 is provided with a port for connecting the RS232C terminal and a non-volatile memory that retains stored contents even after the power is turned off. The RS232C terminal sets a threshold value of an error occurrence frequency in the switching hub 106 and sets a transfer mode at power-on. In addition, the non-volatile memory can store the threshold value, the power-on transfer mode, and the observed error occurrence frequency.

In this embodiment, the switching hub 1
Reference numeral 06 denotes an RS232C terminal or the like which initializes an error occurrence frequency threshold value and a transfer mode at power-on, and stores it in a nonvolatile memory. Therefore, when the power is turned on normally, the operation can be started in the transfer mode of either the store-and-forward method or the cut-through method. In addition, the threshold value of the error occurrence frequency is RS232.
It can also be set via the network management SNMP not via the C terminal but via the network.

When the switching hub 106 starts to operate, the monitor section 101 constantly monitors the error occurrence status for each port. The monitor contents are held in the memory. This memory is the above-mentioned non-volatile memory, and by retaining the contents even after the power is turned off, it can be referred to again after the power is turned on again.

The monitor contents of the monitor unit 101 are error occurrence detection and error occurrence frequency observation. Monitor unit 101
Detects an error occurrence, it is possible to detect an error occurrence even when a frame is transferred by the cut-through method. The error frequency is a fixed time interval,
The number of error frames generated during this time is checked, and the number of error frames is calculated by the error frame number / time.

If this error occurrence frequency is higher than the threshold value,
The switch 102 is switched to the store-and-forward type transfer means 103 side. That is, since the rate of error occurrence is high, unnecessary frame transfer is eliminated by error checking. On the contrary, when the error occurrence frequency is lower than the threshold value, the switch 102 is switched to the cut-through method transfer means 104 side. That is, since the rate of error occurrence is low, error checking can be omitted and the transfer delay time can be shortened.

Regarding the error occurrence frequency, the error occurrence frequency of all the ports may be checked to find the error occurrence frequency and compared with a threshold value. Alternatively, only one port may be checked representatively to find the error occurrence frequency. The result may be compared with a threshold value and applied to all ports, or the error occurrence frequency may be obtained for each port and the transfer mode may be switched by comparing with the threshold value for each port.

[0020]

The present invention exhibits the following excellent effects.

(1) Since the frame transfer mode can be switched depending on the error occurrence frequency, a cut-through method with a small delay time is used at some times and a store-and-forward method capable of removing error frames at other times, depending on the network conditions. Can be automatically selected, and efficient frame transfer can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a switching hub showing an embodiment of the present invention.

[Explanation of symbols]

 101 Monitor Unit (Transfer Mode Determining Means) 102 Switch 103 Store-and-Forward Transfer Means 104 Cut-Through Method Transfer Means 105 Ports

Claims (1)

[Claims] 1. In a switching hub having a plurality of ports and performing frame transfer between ports, the error occurrence frequency of a port is monitored, and the frame transfer mode is cut-through or store-and-forward according to the error occurrence frequency. A switching hub characterized by being provided with a transfer mode switching means for switching between modes.