1. The Repeater (Repeater)

 

Repeater was also become a repeater, it work in the physical layer, the function is to signal amplification and plastic before forwarding out, eliminate signal because after a long period of cable and cause the distortion and attenuation, make the signal waveform and strength to reach the required index. It is the most simple network interconnection equipment, the same network connection of two or more network segment. Such as Ethernet often use repeater expansion bus cable length, the standard fine cable Ethernet every length maximum 185 meters, most can have five section, so increasing the repeater, the largest network cable length can be increased to 925 meters. Generally speaking, the repeater both ends of the network part is the network segment, not subnet.

 

Repeater can connect two LAN cable, retime and regeneration of cable digital signals, then send out, these functions is the first layer ISO model - the typical physical function. Repeater role is to increase local area network coverage area, for example, Ethernet standard gauge order period of signal transmission cable maximum length for 500 meters, but use repeater connection four period of cable, Ethernet in signal transmission cable the longest can amount to 2000 meters. Some brands of repeater can connect different physical medium cable section, such as fine coaxial cable and optical fiber cable. Repeater will only any cable segment data sent to another section cable, and no matter whether there is error in the data data or is not suitable for the data segment.

 

2. Hub (Hub)

 

Hub is the smallest unit of management network, local area network (LAN) is the star connection. It to the workstation for centralized management, don t make problems affecting the whole section of the normal operation of the network. Hub in the local area network (LAN) is the most widely used connecting device, at present if according to configuration forms can be divided into independent model Hub, modular Hub and stack type Hub three. Intelligent Hub (Intelligent Hub) improve the general Hub faults, increased the bridge ability, can filter out does not belong to his segment frame (similar to the bridge), increase segment bandwidth, and network management has the ability and the automatic detection port connected to PC card speed ability, at present Intelligent Hub is used extensively for switched LAN. The market is common to 10 m and 100 m or 10 m / 100 m rate hub (for gigabit Ethernet 1000 m hub has also listed). Hub connection should consider the use of network transmission medium, general hub should have BNC and RJ - 45 two interface or BNC, RJ - 45 and AUI three interface. Hub interface number usually have 8, 12, 16 mouth mouth mouth to wait for a few kinds.

 

Hub a word from English Hub, meant central or multiple intersection. The current production Hub manufacturer about as many as 150, the market competition is fierce. In the user will be a very good chance. Users on the one hand can choose from several products of high performance/price ratio of products, on the other hand can achieve good service.

Early Hub are usually based on optimizing network wiring structure, simplified network management as the goal and design. Now the Hub criterion with high performance, multi-function and intelligent for design goal. The Hub is not only the traditional Hub will more nodes collect received with ability, and take the modular structure, can choose according to need various modules. These modules support transmission media, and media connection mode, communication protocol almost from soup to nuts, this will be a variety of network technology on a case within the facility, some people called super Hub, more people will its called concentrator. Currently provide concentrator products company also has several, such as Bay, Network, Cabletron, Chipcom, 3 com, LANnet and D, Link, and so on. But that doesn t mean concentrator can replace the traditional Hub. Because concentrator need chassis, power and connecting various module interconnection backboard. If you network environment belongs to the working group type, involved in the network node only a few, it is obvious that in this case use concentrator will is a kind of waste.

The term Hub or Hub not only applicable to IEEE802.3 or Ethernet (Ethernet) 10 base-t technology, also applies to 802.5 token ring or ARCnet technology. In token ring technology, the Hub role equipment called MAU (multistation access unit); In APCnet technology, Hub can also be divided into two types, one kind cries active Hub, the other is passive Hub. No matter which kind of Hub, and its function is used to connect many sets of equipment. However, due to the IEEE802.3 10 base-t network technology using range than IEEE802.5 or ARCnet, so at present mainly by Ethernet Hub is given priority to.

 

3. Bridge (Bridge)

 

Bridge (Bridge) like a clever repeater. Repeater from a network cable in receiving signals, amplification them, will it into the next cable. They have no purpose to do so, to their forwarding message contents think nothing of it. In comparison, the bridge to upload the information from levels down more acute some.

 

Bridges will be two similar network link, and the flow of network data management. It works in data link layer, not only can expand the network distance or range, and can improve the network performance, reliability and safety. Networks 1 and network 2 through the bridge connection, bridge in order to receive the network 1 send packets, packet check the address, if the address belongs to the network 1, it will give them, on the contrary, if is a network 2 address, it will continue to send to network 2. Such available bridge isolation information, network divided into multiple segment, isolating the safety net section, prevent other segment of the users in illegal access. Because the network segment, each network segment relatively independent, a segment of the fault will not affect to another network segment operation.

 

Bridge can be designed