1, the computer was first run independently, with advances in technology, computers began to appear on every household's desk, computer network was born in 1950 to 1960 this time period. Consisting of a small computer network at close range, called a local area network, referred to as LAN (local area network), a local area network can be as small as two computers in the same room, or a large campus of thousands of machines. There have been many LAN technologies during this period, of which the most famous is the 'Ethernet'. Ethernet is a LAN technology, appeared in 1970, the principle of all computers connected by wire line Ethernet, data in the form of an optical signal is transmitted into the cable. Within the same local area network, a computer sends a data, all of the other computers can receive data, which is a problem. Party solution to this problem is: give each computer a MAC address, MAC (media access control) the full name of MAC address, and identity as unique, computer manufacturers will be produced before burning a MAC on the network card addresses, a total of 64, 12 hexadecimal bits. So that the computer only needs to listen for the MAC address on the same MAC header data and, if it receives the same, otherwise do not accept this data, this problem is solved.
2, vector refers to data shared medium, the carrier is a copper wire Ethernet, wifi radio wave propagation vector is air. Many computer listens for a carrier, so called Multiple Access. Data transfer speed of the carrier is called bandwidth. However, using the shared medium presents a problem, when the network traffic is small, the computer can wait vector is cleared, and the transmission data. However, when network traffic is large, the probability of two computers to transmit data at the same time will rise, it will conflict. Approach to the problem is: a computer monitor electrical wire to detect these conflicts in case of conflict, the transmission delay of one second, one second, or if there is a conflict, delay of 2 seconds and 4 seconds delay conflict, 8 seconds, 16 seconds until successful transmission. When this was told to wait long exponentially growing 'exponential backoff'.
3, in order to reduce conflicts, improve efficiency, reduce the number of required devices in the same vehicle. And wherein the device carrier together, the "collision domain" Fortunately, we have switches such things, even assuming the cable 6 a computer, called a collision domain, in order to reduce conflicts, which use the switch to split into two collision domains . Recording a list of the switch, which MAC address is read, which side of the network, to transfer data A to C, the switch will not forward the data to the other side of the network, at the same time e to f transmitted data, the network is empty, two transmission can be carried out simultaneously, but if you want to transfer data to f a, the data will be through the switch, on both sides of the network will be briefly occupied, the Internet today is also used in this way
4, the Internet is linked by a number of small networks composed of interesting that a large network to transfer data from one location to another is usually more than one line, called out another thing: the route. Equivalent postman routing from one location to another location, final destination. Three kinds of exchange data are: 1, a circuit switched; 2, packet switching; 3, packet switching. The disadvantage is the high cost of circuit interaction, waste of resources, but the military, banks and some agencies will buy a dedicated line to connect to the data center, benefits are free to use, without sharing, high bandwidth. Disadvantage of packet switching is the whole issue will go to the message, adding a large amount of data can cause network congestion, back through after the transfer of other small things, have to wait for large files. The specific format of the message is "Internet Protocol" defined, referred to as IP (internet protocol), so the network Google's browser to see is the message, which contains header information, request headers, request something the like. We request an address on the Internet, you need to comply with the Internet Protocol, a concrete realization of computer ip address is to give each networked. Sometimes, with a number of packets a packet, it will take a different route, eventually receiving a specified computer, but the situation will be out of order. Fortunately, there are other protocols over ip protocols such as tcp protocol that each packet number, this would resolve the problem out of order, in this way is called packet switching. Today's Internet is so run.
5, a number of standard protocols such as ICMP (Internet Control Message Protocol), the BGP (Border Gateway Protocol). The rapid development of the Internet, it is estimated that there are over 100 million networked devices. Things like refrigerators, thermostats are these "things"
To be continued ~