(For example: the function of the switch, whether the switch can identify virus files, the first program-controlled switch independently developed in China, what are the main manufacturers of the switch at this stage, which manufacturer's switch is used in our school, the price of the switch, the logo of the switch, etc. )
The main functions of the switch include physical addressing, network topology, error checking, frame sequence and flow control. At present, switches also have some new functions, such as supporting VLAN (Virtual Local Area Network), supporting link aggregation, and some even have the function of firewall.
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1986, the first set of SPC exchange S 1240 was successfully rolled off the assembly line in Shanghai bell.
know nothing at all
The price is around 1000 ~ 20000 yuan.
(2) Common sense of hub;
(For example: the function of hub, the price of hub, the difference between hub and switch (from function and identification), etc. )
Function: amplify signal
Propagate signals through the network
No filtering function
No path detection or handover
Used as a network concentration point.
Price: 50 ~ 500 yuan.
There is a repeater on the hub. The main function of the repeater is to shape, regenerate and amplify the received signal, so that the attenuated signal can be regenerated (restored) to the state when it was sent, so as to expand the transmission distance of the network, but it does not have the directional transmission ability of the signal.
In switched Ethernet, the switch provides a dedicated information channel for each user. Unless two source ports try to send information to the same destination port at the same time, each source port and its respective destination port can communicate at the same time without collision.
Switches and hubs only work in different ways, and other connection modes and speed choices are basically the same as hubs.
(3) twisted pair related common sense;
(For example: the function of twisted pair, the price and logo of twisted pair, whether twisted pair can be protected against lightning, whether twisted pair is a telephone line, etc. ).
Function: cheap, easy to install, but easy to interfere, low transmission rate, shorter transmission distance than coaxial cable.
Price: 1 ~ 2 yuan/meter
Just connect the lightning arrester.
Telephone lines can access the Internet, but after signal modulation and demodulation, twisted pair can actually be used as telephone lines, except that there are usually four pairs of twisted pair (super 5: 2 incoming line, 2 outgoing line, and the other two pairs are standby), and only 1 pair is used for telephones (1 incoming line and 1 outgoing line).
(4) Common sense related to modem;
(For example: the function and principle of modem, the price and logo of modem, etc. ).
A device for signal conversion between a computer and a telephone line consists of a modulator and a demodulator. A modulator is a device that modulates a digital signal (such as a file) of a computer into a sound signal that can be transmitted on a telephone line. At the receiving end, the demodulator converts the sound signal into a digital signal that can be received by the computer. Data communication between computers can be realized through modems and telephone lines.
Price: 100 yuan or so.
(5) Common knowledge about cables;
(For example: the function of the cable, the price of the cable, the transmission distance, etc. ).
Used for power, communication and related transmission purposes.
Price: 1 ~ 20 yuan, m.
(6) optical fiber related common sense;
(For example: the function and principle of optical fiber, the price of optical fiber, the transmission distance, the difference and connection with cable and twisted pair, etc. ).
(7) Common knowledge about routers;
(For example: the function of the router, the price of the router, the difference and contact with the switch and hub, etc. ). Work at different levels
The original switch works in the data link layer of OSI/RM open architecture, that is, the second layer, while the router is designed to work in the network layer of OSI model from the beginning. Because the switch works in the second layer (data link layer) of OSI, its working principle is relatively simple, while the router works in the third layer (network layer) of OSI, which can obtain more protocol information and make more intelligent forwarding decisions.
(2) Data forwarding is based on different objects.
Switches use physical addresses or MAC addresses to determine the destination address for forwarding data. Routers use the ID numbers (IP addresses) of different networks to determine the address of data forwarding. The IP address is implemented in software and describes the network where the device is located. Sometimes these Layer 3 addresses are also called protocol addresses or network addresses. The MAC address is usually assigned by the hardware itself and the network card manufacturer, and has been solidified into the network card, which is generally unchangeable. The IP address is usually automatically assigned by the network administrator or the system.
(3) The traditional switch can only divide the collision domain, but not the broadcast domain; Routers can split broadcast domains.
The network segments connected by the switch still belong to the same broadcast domain, and broadcast packets will spread on all network segments connected by the switch, which will lead to communication congestion and security loopholes in some cases. The network segments connected to the router will be assigned to different broadcast domains, and the broadcast data will not pass through the router. Switches with more than three layers can be divided into broadcast domains although they have VLAN function, but there is no communication between sub-broadcast domains, and routers are still needed for communication between them.
(4) Routers provide firewall services.
Routers only forward packets with specific addresses, and do not forward packets that do not support routing protocols and packets of unknown target networks, thus preventing broadcast storms.
Router price: 100 ~ 1000 yuan or so.
(8) Common knowledge about servers;
(For example, the function of the server, etc. ).
WEB server is also called WWW server, and its main function is to provide online information browsing service.
The functions of the server include proxy Internet access, security verification, e-mail service, etc.
Refers to a special computer that provides some services for clients under the network environment. The server is equipped with network operating system (such as Windows 2000 Server, Linux, Unix, etc.). ) and various server application system software (such as Web services and e-mail services).
(9) Network card related common sense;
(For example: the function of the network card, the type of network card, what kind of network card is used at home, and so on. ).
The network card is a network component working in the data link layer, and it is the interface connecting computers and transmission media in the local area network. It can not only realize the physical connection and electrical signal matching with the transmission media in the LAN, but also involve the functions of frame sending and receiving, frame encapsulation and unpacking, media access control, data encoding and decoding, data caching and so on.
Network cards can also be divided into 10Mbps network cards, 100Mbps network cards, 10/ 100Mbps adaptive network cards (figure 1) and gigabit network cards (figure 2) according to the transmission rate. Among them, 10/ 100Mbps adaptive network card is the most popular network card, and its maximum transmission rate is 100Mbps. This network card can automatically judge whether it works in 100Mbps or 100 Mbps according to the speed of the network connection object. Maximum transmission rate of gigabit network card 1000Mbps.
(10) Common knowledge about bridges;
(For example: the function of bridge, the difference and connection between bridge and traditional switch, etc. ).
Expand the network and communication means, forward data signals in various transmission media, expand the distance of the network, and at the same time selectively send signals with addresses from one transmission media to another, effectively limiting the irrelevant communication between the two media systems.