How to understand network device hubs, switches, and routers

Hub (Hub)

A hub is a machine that centralizes a network of cables, which is a connector for multiple hosts and devices. The main function of the hub is to connect the received signal to the synchronous shaping amplification, in order to enlarge the transmission distance of the network, is a form of repeater, the difference is that the hub can provide multiport service, also known as multiple-port relay. The physical layer of a hub in a osi/rm. The basic function of a hub is information distribution, which distributes all the signals received by one port to all ports. Some hubs regenerate weak signals before they are distributed, and some hubs organize the timing of the signals to provide synchronous data communication between all ports.

The hub is actually a multiport repeater. There are generally 4 hubs, 8, 16, 24, 32, such as the number of RJ45 interface, through these interfaces, the hub will be able to complete the corresponding number of computers "relay" function (will have been the attenuation of the incomplete signal after finishing, to produce a complete signal to continue transmission). Because it is in a "center" position on the network, the hub is also called the hub.

The hub works very simply, for example, with a 8-port hub that connects 8 computers. The hub is in the "center" of the network, the signal is forwarded through the hub, and 8 computers can connect and exchange with each other. The specific communication process is this: if Computer 1 is going to send a message to computer 8, when the network card of the Computer 1 delivers the information through the twisted pair to the hub, the hub does not send the information directly to the computer 8, it broadcasts the information to 8 ports at the same time. When a 8-port computer receives this broadcast information, it checks the information and receives it if it is found to be sent to itself. Because this information is sent to the computer 8 by Computer 1, the final computer 8 receives the information, and the other 7 computers do not receive the information because the information is not its own after reading the information.

Switches (switch)

Switch is a hub of the upgrading of products, shape and hub is no different, is a communication system in the automatic completion of information exchange function of the device, the use and hub is also connected to the network, but it has a more powerful than the hub function.

Switches are also called switched hubs, by regenerating the information and forwarding it internally to the specified port, it has an automatic addressing capability and a switching function, because the switch sends each packet independently from the source port to the destination port based on the destination address of the packets being delivered, avoiding collisions with other ports. The general switch is a device that completes the information exchange function in the communication system.

In the computer network system, the switch is aimed at the weakness of the shared work mode. Hubs are representatives of shared work patterns, if the hub is compared to a postman, then the postman is a "fool" who does not know the word--to send a letter, and he does not know to give it to the addressee directly according to the address of the letter, and will only hand it over to all the people, And then let the recipient according to the address information to determine whether their own! And the switch is a "smart" postman--the switch has a high-bandwidth back bus and an internal exchange matrix. All the ports on the switch are hooked up on this back bus, when the control circuit receives the packet, the processing port finds the Address table in memory to determine which port the NIC (network card) is hooked on the destination Mac (the hardware address of the network adapter), and transmits the packet quickly to the destination port through the internal exchange matrix. If the Mac does not exist, the switch is broadcast to all ports, and the switch will "learn" the new address and add it to the internal address table after receiving the port response.

Visible, the switch received a card sent over the "letter", will be based on the above address information, as well as their own master of "resident resident residence booklet" quickly sent letters to the hands of the addressee. In the event that the addressee's address is not on the "booklet", the switch will distribute the letter to all the people like a hub, and then find the recipient from it. After the recipient is found, the switch will immediately register the person's information on the "residence booklet", so that when the customer service, you can quickly delivery of the letter.

Router (Router)

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A router is a key device for connecting between networks in a network. As the hub of interconnection between different networks, the router system constitutes the main thread of the Internet of the International Interconnect network based on TCP/IP.

Routers are in a critical position in the Interconnect network, because it is in the network layer, on the one hand can cross different physical network types (DDN, FDDI, Ethernet, etc.), on the other hand, logically divides the entire interconnection network into a logically independent network unit, so that the network has a certain logical structure. The main task of the router is to find an optimal transmission path for each data frame passing through the router and to effectively transfer the data to the destination site. The basic function of a router is to transfer data (IP packets) to the correct network, the subdivision includes: 1, IP datagram forwarding, including the data search and transmission, 2, subnet isolation, suppression of broadcast storms; 3, maintain the routing table and Exchange routing information with other routers, which is the basis of IP message forwarding; 4, IP Error handling of datagram and simple congestion control; 5, the realization of the IP datagram filtering and accounting.

Routers make up the skeleton of the Internet. Its processing speed is one of the main bottlenecks of network communication, and its reliability directly affects the quality of network interconnection. Therefore, in the Internet research field, the router technology is always at the core position.

Let's look at other descriptions that are very popular with these three kinds of devices.

Hub-Computer network "walkie-talkie", it can be the simplest to achieve more than one computer network communication.

Features: Receiving the same set of multiple computers, like using the same frequency of "walkie-talkie" for communication, at any one time can only have a pair of "walkie-talkie" to communicate. That is, when the computer 1 and Computer 3 communication, the computer 2 and the computer 4 can not communicate, only the computer 1 and computer 3 communication after the end of communication.

Switch--the "telephone operator" in the computer network, which is responsible for the internet's "telephone" access work.

Features: When the computer 1 wants to communicate with the computer 2, it must first call the "telephone operator" and the computer 2 of the "phone" connected, after the switch, "telephone operator" can do other work, such as the computer 3 and computer 4 between the "phone." It can simultaneously complete the multi-channel "telephone" the exchange and the connection work, therefore calls the switch.

Router-a "front" in a computer network that is responsible for sorting and forwarding information about a network.

Features: When "I" (Computer A) wants to visit the "article" website, "I" as long as the "front" "Big ye" words, there is no need to go to the Post Office to order or find a newspaper kiosk sold by the "front" unified responsible for subscription or purchase, and distribution of "households." When the "Outside unit" (Computer B) has "things" (information) to the "I", as long as the things to "the" front, "" The "front" in the "Big ye" will bring things to the door.

A hub is like dividing a faucet into several streams. The total amount of water is equal to the quantity of each faucet and the number of each part will become less.

The switch is with a conversion head. Give 1th a second for number 2nd. Use each to make all the water, but not always.

The router is in this group of taps with a human intelligence to see which one needs to give the water