TCP/IP Detailed learning notes (1)-Basic concepts

Original address: http://blog.csdn.net/goodboy1881/article/details/665041

Why is there a TCP/IP protocol

All over the world, a wide variety of computers run their own different operating systems for everyone, and these computers are used in many ways when expressing the same message. It is as if God in the Bible has disturbed the accents of people everywhere and made them unable to cooperate. Computer users realize that the computer is only a man-in-the-war and does not play a big role. Only by bringing them together can the computer play its greatest potential. So people are trying to connect the computer to each other by electric wires.

But the simple connection is not enough, as if the language of the different two people meet each other, completely unable to exchange information. So they need to define something common to communicate, and TCP/IP is born for that. TCP/IP is not a protocol, but a generic term for a protocol family. It includes IP protocols, IMCP protocols, TCP protocols, and more familiar HTTP, FTP, POP3 protocols, and more. Computers have these, as if learning a foreign language, you can and other computer terminals to do free communication.

TCP/IP Protocol tiering

When it comes to protocol layering, it's easy to think of Iso-osi's seven-layer protocol classic architecture, but the structure of the TCP/IP protocol family is slightly different.

The TCP/IP protocol family is packaged in layers from top to bottom. The top is the application layer, which has http,ftp, and so on we are familiar with the agreement. The second layer is the transport layer, and the famous TCP and UDP protocols are at this level (don't tell me you didn't use UDP to play StarCraft). The third layer is the network layer, where the IP protocol is responsible for adding IP addresses and other data to the data (as described later) to determine the destination of the transmission. The fourth layer is called the data link layer, which adds an Ethernet protocol header to the data to be transmitted, and the CRC code is prepared for the final data transfer. Then down is the level of hardware, responsible for the transmission of the network, the definition of this level includes the cable format, network card definition and so on (these we do not care, we do not do network cards), so some books do not put this level in the TCP/IP protocol family, because it almost and tcp/ The creator of the IP protocol does not have any relationship. The host sending the protocol encapsulates the data from top to bottom, while the host receiving the data is untied from the received packet and finally gets the required data. This structure is very stack-flavored, so some articles also refer to the TCP/IP protocol family as the TCP/IP protocol stack.

Some basic common sense.

Before we learn the agreement, we should have some basic knowledge.

Internet address (IP address)

Each node on the network must have a separate Internet address (also known as an IP address). Now, the commonly used IP address is a 32bit number, which is what we often call the IPV4 standard, this 32bit number is divided into four groups, that is, the common 255.255.255.255 style. IPV4 Standard, the address is divided into five categories, we often use a class B address. Please refer to the other documentation for specific classifications. It is important to note that the IP address is a combination of network number + host number.

Domain Name System

The domain Name system is a distributed database that provides services that convert host names (URLs) to IP addresses.

Rfc

What is an RfC? The RFC is the standard document for the TCP/IP protocol, where we can see the long definition list of RFCs, which now has a definition of more than 4,000 protocols, and of course, the more than 10 protocols we are going to learn.

Port number (port)

Note that this number is used on the tcp,udp of a logical number, not a hardware port, we usually say that a certain port sealed off, but also only in the IP layer with this number of IP packets to filter out just.

Application Programming Interface

Now the common programming interfaces are sockets and Tli. And the front is sometimes called the "Berkeley socket", can be seen Berkeley for the development of the network of how much contribution.

TCP/IP Detailed learning notes (1)-Basic concepts