JP2000196644A - Switching hub - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching hub which suppresses the load of a network in the network where a repeater is connected and improves the responsiveness of inter-terminal communication in the network where the repeater is connected. SOLUTION: In this switching hub 101 which has plural ports and relays a frame received by a certain port to a port corresponding to the destination address of the frame, a repeater detecting means that detects whether or not a device connected to the port is a repeater according to the number of kinds of transmission source addresses of a frame to be received by the port is provided, when the device connected to the port is a repeater 102, the received frame is authenticated to reject an illegal received frame, and when the device connected to the port is not a repeater, the received frame is relayed without authentication.

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 constitutes a frame relay device in a network, and more particularly to a network connected with a repeater, which reduces the load on the network, and a network connected with a repeater, in which communication between terminals is performed. And a switching hub for improving the responsiveness of the switching hub.

[0002]

2. Description of the Related Art A conventional switching hub verifies that a frame received from a certain transmission / reception port (hereinafter simply referred to as a port) is normal based on a MAC bridge standard (IEEE 802.1D), and performs filtering only when the frame is normal. It has a function of referencing the database and relaying or discarding it to another port.

For example, in the case of Ethernet (registered trademark) standardized by IEEE802.3, frames whose frame length, frame length boundary, CRC (sum check of data content), etc. do not conform to the standard are regarded as illegal frames. Is defined. FIG. 4 shows an Ethernet frame format.

[0004] An invalid frame is completely useless data because it is not received by any terminal. Normally, it is desired that a relay device that relays a frame discards an illegal frame. However, with the spread of information equipment such as personal computers and higher performance, the amount of data in the information network is increasing. Therefore, it is necessary to omit the process of verifying whether or not the received frame is illegal and to relay at high speed. May be desired for the relay device.

A switching hub having a function of relaying a received frame in a short time without verifying whether or not the frame is illegal is called a cut-through switch. On the other hand, a switching hub having a function of relaying only a normal received frame is called a store-and-forward switch.

[0006] In the store-and-forward switch, it is not possible to confirm whether the received frame is a normal frame unless the received frame is completely received, so that the relay delay increases. In the case of 10 Mbps Ethernet, the maximum frame length is 12000 bits (150
0 bytes), transmission starts 1.2 microseconds after the start of reception. The time difference from the start of reception to the start of transmission is called a relay delay. When a plurality of switching hubs are arranged between terminals, relay delays generated in the respective switching hubs are added, so that responsiveness of communication between terminals may be deteriorated.

In the cut-through switch, transmission is started from a required port before a received frame is completely received, so that a relay delay is reduced.

[0008]

FIG. 5 shows a network using a conventional switching hub. The switching hub 401 includes transmission / reception units 422 and 423 provided for each port for transmitting and receiving a frame, a frame exchange unit 421 for relaying a frame between ports, a processor 424 for determining a relay port, and correspondence between an address and a port. A memory 425 containing a filtering database for holding data is provided. The terminal 411 is connected to one port of the switching hub 401, and the terminals 412 and 413 are connected to the other port via the repeater 402.

[0009] Here, if the terminals 412 and 413 start transmitting frames at the same time, a frame collision occurs,
As a result, since the terminals 412 and 413 interrupt the transmission,
An illegal frame shorter than the Ethernet standard occurs.

[0010] When the switching hub 401 is a cut-through switch, the above-mentioned illegal frame is relayed. As a result, an increase in the number of illegal frames on the network increases the load on the network, which hinders transmission and reception of frames. FIG.
When a repeater is connected to the network as in the above, frames tend to collide, and the number of illegal frames generated as a result of the collision increases. Therefore, in the network to which the repeater is connected, the transmission / reception of the frame is likely to be hindered.

Accordingly, an object of the present invention is to solve the above problems and to provide a switching hub which suppresses the network load in a network to which a repeater is connected and improves the responsiveness of communication between terminals in a network to which a repeater is connected. Is to do.

[0012]

In order to achieve the above object, the present invention provides a switching hub having a plurality of ports and relaying a frame received at a certain port to a port corresponding to a destination address of the frame. A repeater detecting means for detecting whether or not the device connected to the port is a repeater according to the number of types of the source address of the frame received by the port, when the device connected to the port is a repeater Is to verify a received frame, discard an incorrect received frame, and relay the received frame without verification when the device connected to the port is not a repeater.

[0013] Switching means for switching the frame relay system between a store-and-forward system and a cut-through system in accordance with the result of the repeater detection may be provided.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

As shown in FIG. 1, a switching hub 101 according to the present invention includes transmitting / receiving units 122 and 123 provided for each port for transmitting and receiving a frame, a frame switching unit 121 for relaying a frame between ports, and a relay port. , And a memory 125 containing a filtering database for storing correspondence data between addresses and ports.

The switching hub 101 of the present invention comprises: a repeater detecting means for detecting whether or not a device connected to a port is a repeater based on the number of types of source addresses of frames received by the port; Switching means for switching the frame relay system between the store-and-forward system and the cut-through system in accordance with the result of (1). The switching hub 101 stores
When operating in the forward mode, verify received frames and discard invalid received frames, relay only normal received frames, and when operating in the cut-through mode, relay received frames without verification. become. The repeater detecting means is constituted by, for example, the processor 124.

In this embodiment, the repeater detecting means includes:
Whether or not the device connected to the port is a repeater is determined using information of the filtering database. This filtering database is shown in FIG.
As shown in FIG. 2, the information is stored in the memory 125 in the switching hub 101 as tabular information. The filtering database contains a number that identifies the port,
The information of the source address of the frame received in the past from the port of each number is stored. If there is only one type of source address of a frame received in the past at a certain port, it may be determined that a terminal is connected to the port. Conversely, when a port has a plurality of types of source addresses of frames received in the past, it may be determined that a repeater is connected to the port. By counting the types of source addresses of the same port in the filtering database, repeater detection is possible.

Here, as a network configuration, a terminal 111 is connected to one port of the switching hub 101, and the terminal 11 is connected to the other port via a repeater 102.
2, 113 are connected. Therefore, FIG.
As shown in, the filtering database contains
Only the source address = 4 is stored corresponding to the port number = 1, and the source address = 8 corresponding to the port number = 2
And 10 are stored. That is, the port with port number = 1 has one type of source address, and thus it is determined that a terminal is connected. However, the port with port number = 2 has two types of source addresses. It will be determined that the repeater is connected.

If there are a plurality of types of source addresses stored in the filtering database for one port, the switching means stores the frame relay system in the storage mode.
An AND forward method is used. As a result, the switching hub 101 operates as a store-and-forward switch. Therefore, even if the number of illegal frames increases due to the presence of the repeater, the illegal frames are not relayed in the switching hub 101, so that the load on the network can be suppressed.

If there is one type of source address stored in the filtering database for one port, the switching means sets the frame relay system to the cut-through system. Thereby, the switching hub 1
01 will operate as a cut-through switch. Therefore, the responsiveness of communication between terminals can be improved by reducing the relay delay.

Next, an embodiment of the switching means will be described.
As shown in FIG. 3, a CRC check circuit, a frame length check circuit, and the like are provided in the switching hub as a circuit for verifying the received frame together with a buffer for temporarily storing the received frame. If the frame is invalid, it can be discarded. The switching unit 501 has a configuration for switching between sending a received frame to a buffer and each check circuit or bypassing the received frame. The repeater detecting means in the switching hub controls the switching means.

Immediately after the switching hub is turned on, the received frame is bypassed without being sent to the buffer and each test circuit. That is, the frame relay system is a cut-through system. Thereafter, when a plurality of frames having different types of source addresses are received at a certain port, the switching unit is controlled to perform received frame verification. As a result, the frame relay system is switched to the store-and-forward system.

It is assumed that the switching means as shown in FIG. That is, switching means is provided for each port. If it is determined that a terminal is connected to a certain port, the received frame at that port is sent to the frame switching unit 121 without passing through a buffer and each check circuit, and a repeater is connected to a certain port. When it is determined that the frame is received, the frame received at the port is sent to the buffer and each check circuit, the invalid frame is discarded, and only the normal frame is sent to the frame switching unit 121.

[0024]

The present invention exhibits the following excellent effects.

(1) When a repeater is connected, a frame collision occurs when a plurality of terminals connected to the repeater start transmission at the same time in order to verify a received frame and discard an incorrect received frame. Can be discarded, and when the repeater is not connected, the process of verifying the received frame can be omitted and the frame can be relayed in a short time. This greatly improves the network usage efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram showing an internal configuration and a network configuration of a switching hub according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a filtering database used for a repeater detection unit of the present invention.

FIG. 3 is a circuit diagram showing one embodiment of a switching unit of the present invention.

FIG. 4 is a frame configuration diagram showing an Ethernet frame format.

FIG. 5 is a diagram showing an internal configuration and a network configuration of a conventional switching hub.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Switching hub 102 Repeater 111, 112, 113 Terminal 121 Frame exchange part 122, 123 Transceiver part 124 Processor 125 Memory 501 Switching means

Claims (2)

[Claims] In a switching hub having a plurality of ports and relaying a frame received at a certain port to a port corresponding to a destination address of the frame, the switching hub determines the number of types of source addresses of the frame received at the port. ,
A repeater detecting means for detecting whether or not the device connected to the port is a repeater, and when the device connected to the port is a repeater, verifies a received frame and discards an invalid received frame, A relay device that relays a received frame without verifying it when a device connected to the switching device is not a repeater. 2. The switching hub according to claim 1, further comprising switching means for switching the frame relay system between a store-and-forward system and a cut-through system in accordance with a result of the repeater detection. .