TCP/IP (Transmission Control Protocol/Internet Protocol) is a transmission control protocol/internet protocol. It is an industrial standard protocol set designed for wide area networks (WANs). It was developed by the research organization of ARPANET. Sometimes we describe TCP/IP as the Internet Protocol Set "Internet Protocol Suite", and TCP and IP are two of them (which will be introduced later). Since TCP and IP are familiar protocols, the word TCP/IP or IP/TCP is used instead of the entire protocol set. Although this is a bit strange, there is no need to argue about the habit. For example, sometimes when we discuss that NFS is based on TCP/IP, although it does not use TCP at all (only IP, and another interactive protocol, UDP, not TCP).
The Internet is a collection of networks, including ARPANET, NSFNET, local area networks distributed throughout the region, and other types of networks, such as (DDN, Defense Data Network, US Defense Data Network), which are collectively called the Internet. All these large and small networks are connected together. (Because most basic network protocols are developed by DDN organizations, sometimes DDN and the Internet have the same meaning in some sense). Users on the network can transmit information to each other, except for some authorized restrictions and security considerations. Generally speaking, Internet protocol documents are the basic standards adopted by the Internet Committee itself.
The TCP/IP standard is not so designated by the committee, but rather developed by "public opinion". Anyone can provide a document to be published in RFC (Request for Comment Requirement Comment). The TCP/IP standard is published in a series of documents called RFC. Documentation is revised by technical experts, task force, or RFC editors. When publishing a document, the document is assigned an RFC amount, such as RFC959 description FTP, RFC793 description TCP, RFC791 description IP, etc. The original RFC has been retained and never been updated. If the document is modified, the document will be published with a new number. Therefore, it is important to confirm that you have the latest RFC documentation on a topic. The main RFC document numbers will be listed later.
TCP/IP is a protocol set. Provides some "low-level" functions for applications, including IP, TCP, UDP. Others are application protocols that perform specific tasks, such as transferring files between computers, sending emails, or finding out who registers with another computer. Therefore, the most important "commercial" TCP/IP services are:
* File Transfer
File Transfer Protocol (File Transfer Protocol) allows users to obtain files from one computer to another, or send files to another computer. From a security perspective, the user needs to specify a username and password to use other computers. It is different from the NFS (Network File System) and Netbios protocols. Once you want to access files in another system, run FTP at any time. And you can only copy files to your own machine to use it. (Notes about FTP in RF C 959)
* Remote login
Network terminal protocol TELNET allows users to log in to any computer on the network. You can start a remote process to connect to the specified computer until the process ends, during which the content you type is sent to the specified computer. It is worth noting that at this time you are actually having a conversation with your computer. The TELENET program makes your computer disappear throughout the process, and every character you type is sent directly to the logged-in computer system. Generally speaking, this kind of remote connection is connected through class dialing, that is, after dialing, the remote system prompts you to enter the registration name and password, exit the remote system, and the TELNET program will exit, and you will talk to your computer again. The TELNET tool in a microcomputer generally contains a terminal emulation program.
* Computer mail Mail
Allows you to send messages to users of other computers. Often, people tend to use one or two computers specified. The computer mail system simply requires you to simply add information to another user's email file, but problems arise. The environment of the microcomputer used is different. It is also important that macros (MICRO) are not suitable for accepting computer mail. In order to send emails, the mail software wants to connect to the destination computer, if it is a microcomputer, maybe it is shut down, or it is running another application? For this reason, it is usually a larger system that processes the mail, which is a running mail server. Mail software becomes an interface for users to retrieve emails from mail servers.
TCP/IP tools provide the above services. These traditional application functions have always played a very important role in TCP/IP-based networks. The situation has changed a little, and the use of these functions has also changed, such as the transformation of old systems and the development of computers. Various installation versions have emerged, such as microcomputers, workstations, minicomputers, and giant machines. These computers seem to complete designated tasks together. Although sometimes it seems to only use a specified computer, it is serviced by other computer systems through the network. Server is a system that provides specified services to other systems on the network, and client Cl is another computer system that receives such services. (It is worth noting that the service/client is not necessarily a different computer, it may be different running programs in the same computer). Here are some typical services on computers that can be called on TCP/IP networks.
* Network File System (NFS)
This method of accessing files from another computer is very close to popular FTP. A network file system provides disk or device services without the need for specific network utilities to access files from another system. It can be simply considered an additional disk drive. This additional "virtual" disk drive is the disk of other computer systems. This is very useful. You just need to increase the disk capacity of several computers to allow other users on the network to access it, and not to mention the economic benefits it brings, it can also allow several working computers to share the same files. It also makes system maintenance and backup easy, because there is no need to worry about upgrading and backup of files on a large number of different machines.
* Remote printing
Allows you to use printers on other computers as if these printers are directly connected to your computer.
* Remote execution
Allows you to request special programs running on different computers. Remote execution is very useful when you run a program that requires large computer system resources on a very small computer.
* Name servers
During the installation of a large system, a large number of names are needed, including user names, passwords, names, network addresses, accounts, etc. It is very boring to manage these. Therefore, these data are formed into a database and placed in a small system, and other systems access these data through the network.
* Terminal servers
Many terminal connection installations no longer directly connect terminals to computers, but instead connect them to terminal servers. A terminal server is a small computer that just needs to know how to run TELNET (or some other protocol that completes remote login). If your terminal wants to connect, just type the name of the computer you want to connect to. It is usually possible to have several such connections at the same time, and the terminal server uses fast switching technology to switch. Some of the protocols described above are defined by Berkeley, Sun, or other organizations. Therefore, they are not part of the Internet Protocol Suite, but are just tools that use TCP/IP, just like the general TCP/IP application protocol. Because the protocol definitions are inconsistent and commercially supported TCP/IP tools are widely used, these protocols may be used as part of the interconnected protocol set. The above list is just some simple examples of TCP/IP-based services, but contains some "main" applications.