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This article mainly introduces the relevant knowledge of what is the source of tcp/ip in the computer network, the content is detailed and easy to understand, the operation is simple and fast, and has a certain reference value. I believe you will gain something after reading this article on the source of tcp/ip in the computer network. Let's take a look at it.

1. The source of tcp/ip:

Many different manufacturers produce various types of computers that run completely different operating systems, but the T C P / IP protocol family allows them to communicate with each other. This is surprising because it is far more effective than originally thought. T C P / IP originated from a packet switching network research project funded by the American government in the late 1960s, and has become the most commonly used networking form between computers in the 1990s. It is a truly open system because the definition of a protocol family and its multiple implementations are publicly available for little or no money. It became the basis for what is known as the "Global Internet" or "I n t e r n e t", a wide area network (WA N) that already contains more than 1, 0 computers around the world.

Second, layer 4 layering protocol:

Network protocols are usually developed at different levels, and each layer is responsible for different communication functions. A protocol family, such as T C P / IP, is a combination of multiple protocols at different levels. T C P / IP is usually considered as a four-layer protocol system, as shown in figure 1-1:

Each layer is responsible for different functions:

The link layer, sometimes referred to as the data link layer or network interface layer, usually includes the device driver in the operating system and the corresponding network interface card in the computer. Together, they deal with the details of the physical interface with the cable (or any other transmission medium).

The network layer, sometimes referred to as the Internet layer, deals with the activities of packets in the network, such as packet routing. In the T C P / IP protocol family, the network layer protocols include IP protocol (Internet protocol), I C M P protocol (I n t e r n e t Internet control message protocol), and I G M P protocol (I n t e r n e t group management protocol).

The transport layer mainly provides end-to-end communication for applications on the two hosts. In the T C P / I P protocol family, there are two different transport protocols: T C P (Transmission Control Protocol) and U D P (user Datagram Protocol). T C P provides highly reliable data communication between the two hosts. The work it does includes dividing the data given to it by the application into appropriate pieces to the network layer below, confirming the received packets, setting the timeout clock to send the final acknowledgement packets, and so on. Because the transport layer provides highly reliable end-to-end communication, the application layer can ignore all these details. U D P, on the other hand, provides a very simple service for the application layer. It simply sends packets called datagrams from one host to another, but there is no guarantee that the Datagram will reach the other end. Any required reliability must be provided by the application layer. These two transport layer protocols have different uses in different applications, as you will see later.

The application layer is responsible for handling specific application details. Almost a variety of T C P / I P implementations provide the following common applications:

Telnet remote login.

FTP File transfer Protocol.

SMTP simple Mail transfer Protocol.

SNMP simple Network Management Protocol.

There are many other applications, some of which will be covered in later chapters. Assuming that there are two hosts in a local area network (L A N) such as Ethernet, both running the F T P protocol, figure 1-2 lists all the protocols involved in this process:

Here, we list a F T P client program and another F T P server program. Most web applications are designed in client-server mode. The server provides some kind of service to the customer, in this case, accessing the file on the host where the server is located. In the remote login application Te l n e t, the service provided to the customer is to log in to the server host.

On the same layer, both parties have one or more corresponding protocols to communicate. For example, one protocol allows T C P layer forward communication, while another protocol allows two IP layers to communicate.

On the right side of figure 1-2, we notice that the application is usually a user process, while the lower three layers are generally executed in the (operating system) kernel. Although this is not necessary, it is usually handled this way, such as the U N I X operating system.

In figure 1-2, there is another key difference between the top and the bottom three layers. The application layer is concerned with the details of the application, not the transmission of data over the network. The lower three layers know nothing about the application, but they deal with all the communication details.

Four different levels of protocols are listed in figure 1-2. F T P is an application layer protocol, T C P is a transport layer protocol, IP is a network layer protocol, and Ethernet protocol is used at the link layer. The T C P / I P protocol family is a group of different protocols combined together to form a protocol family. Although this protocol family is commonly referred to as T C P / I P, T C P and I P are just two of them (another name of this protocol family is Internet Protocol Family (Internet Protocol Suite)).

The purpose of the network interface layer and the application layer is obvious-the former deals with details about the communication medium (Ethernet, token Ring, etc.), while the latter deals with a particular user application (F T P, Te l n e t, etc.). However, on the face of it, the difference between the network layer and the transport layer is not so obvious. Why divide them into two different levels? To understand this, we must expand our vision from a single network to a group of networks.

In the 1980s, one of the reasons for the growing network was that everyone realized that an "isolated island" made up of only one isolated computer didn't make much sense, so these isolated systems were grouped together to form a network. With this development, in the 1990s, we gradually realized that this new and larger "island" made up of a single network also did not make much sense. As a result, people connect multiple networks together to form a network, or Internet (i n t e r n e t). An interconnection network is a group of networks interconnected by the same protocol family.

The easiest way to construct an Internet is to connect two or more networks through a router. It is a special hardware box for network interconnection. The advantage of routers is that they provide connections for different types of physical networks: Ethernet, token Ring, Point-to-Point links, F D D I (Optical Fiber distributed data Interface), and so on.

These boxes are also called IP routers (IP Router), but we use the term Router here. Historically, these boxes have been called gateways, and the term has been used in many T C P / I P literature. Now the term gateway refers only to an application layer gateway: a process that connects two different protocol families (for example, TCP/IP and IBM's SNA) that serves a particular application (often e-mail or file transfer). Figure 1-3 shows an Internet consisting of two networks: an Ethernet network and a token ring network, connected to each other through a router. Although here two hosts communicate through a router, virtually any host in Ethernet can communicate with any host in the token ring.

In figure 1-3, we can divide the end system (End system) (two hosts on both sides) and the intermediate system (Intermediate system) (the router in the middle). The En d-to-e n d protocol is used in the application layer and transport layer. In the figure, only the end system needs these two layers of protocols. However, the network layer provides a Ho p-b y-h o p protocol, which is used by both end systems and each intermediate system.

In the T C P / IP protocol family, the network layer IP provides an unreliable service. In other words, it only sends packets from the source node to the destination node as soon as possible, but does not provide any reliability guarantee. T C P, on the other hand, provides a reliable transport layer on the unreliable I / P layer. In order to provide this reliable service, T C P adopts mechanisms such as timeout retransmission, sending and receiving end-to-end acknowledgement packets. It can be seen that the transport layer and the network layer are responsible for different functions.

By definition, a router has two or more network interface layers (because it connects two or more networks).

Any system with multiple interfaces is called m u l t i h o m e d in English. A host can also have multiple interfaces, but it is generally not called a router unless its function is simply to transfer packets from one interface to another. Similarly, routers do not necessarily refer to the special hardware boxes used to forward packets on the Internet. Most T C P / IP implementations also allow a multi-interface host to function as a router, but the host must be specially configured for this purpose. In this case, we can call the system either a host (when it is running an application, such as F T P or Te l n e t) or a router (when it forwards packets from one network to another). Use different terms in different situations.

One of the purposes of the Internet is to hide all the physical details in the application. Although this is not obvious in the Internet consisting of two networks in figure 1-3, the application layer cannot care (nor care) that one host is on Ethernet and the other is on the token ring. They are interconnected through routers. With the addition of different types of physical networks, there can be 20 routers, but the application layer is still the same. The hiding of physical details makes the Internet very powerful and useful.

Another way to connect to the network is to use a bridge. Bridges interconnect networks at the link layer, while routers interconnect networks at the network layer. The bridge brings multiple local area networks (L A N) together so that it is like a local area network to the upper layer.

This is the end of the article on "what is the source of tcp/ip in the computer network". Thank you for reading! I believe you all have a certain understanding of the knowledge of "what is the source of tcp/ip in the computer network". If you want to learn more, you are welcome to follow the industry information channel.

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