Hello everyone. This is a new series. In this series, I will introduce you to concepts related to computer networking.Computer network technology is a mandatory subject for the spring college entrance examination, highlighting the importance of this field. Don’t be afraid. I will guide you to gradually understand it. Over time, you will learn this technology and apply it directly in practice.Note: Some content in this article is derived from the book on computer network technology (ISBN: 9787040569032), which I have summarized and explained. The chief editor and publisher of the computer network technology book reserve all rights.(The above is fixed content for this series.)After discussing the OSI reference model, let’s talk about its twin brother—the TCP/IP protocol.First, let’s discuss the differences between the two:The TCP/IP protocol (Transmission Control Protocol/Internet Protocol) is essentially a simplified version of OSI, abbreviated asextracting the essence while discarding the dross.However, this statement is not very precise.
The TCP/IP protocol suite and the OSI reference model are not simply a “simplified” relationship, but rather two network architecture systems with “aligned goals but completely different design philosophies and practical paths.” The core connection between the two is that “both aim to solve the problem of layered communication in networks,” but TCP/IP is an industry standard oriented towards practical application, while OSI is a theoretical reference model.
Because TCP/IP merges the OSI’s “session layer and presentation layer” into the application layer, and combines the “physical layer and data link layer” into the link layer, it indeed appears more “concise” in terms of the number of layers, which is the origin of the “simplified version” claim—however, this “simplification” is a “theoretical layer merged as needed,” rather than a “reduction of core functions.”
Next, we will explain these layers one by one.
The TCP/IP model consists of four layers: the Network Interface Layer, the Internet Layer, the Transport Layer, and the Application Layer.
Network Interface Layer:
It transmits specific network frames, corresponding to the OSI’s data link layer, responsible for data exchange, sending data out through the network, or receiving and processing data from the network.
Internet Layer:
It transmits IP datagrams. It is responsible for managing data exchange between different devices.
It also has another name, called the IP layer.
It has several defined “rules” (protocols):
Internet Protocol: Equivalent to traffic rules on the network, determining the sender and receiver and providing end-to-end delivery.
Internet Control Message Protocol: handles routing (not really) and assists the Internet layer in message transmission control, providing error and information reporting.
Address Resolution Protocol: Just saying this, you probably won’t understand. It also has another name, called ARP.
It converts network addresses to link addresses.In network communication, when a host or network device needs to send data to another host or device, it needs to know not only the other party’s IP address but also their physical address (MAC address), because data needs to be encapsulated into frames for transmission over the physical network, and frame transmission relies on MAC addresses. The role of the ARP protocol is to establish a mapping relationship between IP addresses and MAC addresses so that data can be correctly transmitted to the target host within a local area network.
Reverse Address Resolution Protocol: It is called RARP. It is the reverse version of the above (link to network).
At this point, some of you might ask: “Host, isn’t this just DNS?”
Yes.
They
are completely different things.
Although they are both related to “network address mapping,” they solve address conversion problems at different levels and in different scenarios, with essential differences in core functions, scope of action, and operational levels.
ARP/RARP: Solves the mapping of IP addresses (limited to local area networks) and MAC addresses (conversion between hardware addresses and network layer addresses)
DNS: Solves the mapping of domain names and IP addresses (conversion between human-readable domain names and network layer addresses on the internet).
Transport Layer: It is the same as the OSI reference model. It ensures that all transmitted data arrives at the system correctly and accurately. (Liangxiang uplink two roads through signal open)
It has the following two protocols.
TCP: Transmission Control Protocol, which provides a connection-oriented reliable data transmission service.
UDP: User Datagram Protocol, which uses connectionless datagram transmission. It is generally used for transmitting small amounts of information.
Application Layer: It is the highest layer and has the most tasks to perform.
The application layer is the closest layer to the user—all the network applications we use daily (such as browsing the web, sending WeChat messages, transferring files) have their core logic and data interaction rules defined at this layer. Its essence is: a “communication protocol specification” formulated for specific application scenarios, responsible for enabling applications on different devices to “understand each other’s data” and complete data transmission through lower-level protocols (TCP/UDP, IP, etc.).
It has a bunch of protocols.
FTP (File Transfer Protocol): The protocol used for server FTP.
Telnet: Remote login, enabling remote login to the internet (terminal login to the server).
SMTP: Simple Mail Transfer Protocol. You use it to send emails.
HTTP: Hypertext Transfer Protocol. The protocol for the web pages you view.
RIP: Routing Information Protocol, used for exchanging routing information between devices.
NFS: Network File System. Used for file sharing between different hosts on the network.
NFS and FTP can be easily confused, so let me clarify the difference:
NFS (Network File System) and FTP (File Transfer Protocol) are two core file sharing/transmission protocols, both belonging to the TCP/IP application layer, but they have essential differences in design goals, usage scenarios, and operational methods—simply put: FTP is a “file transfer tool” (downloading/uploading single/multiple files), while NFS is a “network drive mapping” (mounting remote directories locally, allowing operations as if using a local hard drive).
DNS: Domain Name Service. Used to achieve conversion from host names to IP addresses.
The characteristics of the TCP/IP protocol can be summarized as follows:
1. An open protocol standard, independent of specific computer hardware and operating systems.
2. A unified network address allocation scheme, using a software-based addressing method that is independent of hardware, ensuring that all devices in the network have a unique IP address.
3. Independent of specific network hardware, it can operate on local area networks and wide area networks, particularly suitable for the Internet.
4. Standardized high-level protocols that can provide various reliable user services.
That concludes the content on TCP/IP. Thank you all for your support. The updates may be a bit slow recently, please bear with me.