Getting started with TCP/IP protocol 1 (1)

1. Preface

This article is used to introduce the basic content of TCP/IP protocol, which is very simple and basic. If you want to learn more, please refer to other materials, which is only for beginners.

2. TCP/IP Introduction

TCP/IP usually refers to anything about TCP/IP and IP. It is a general term that can include other protocols, other applications, and network media.

2.1 Basic Structure

To understand this technology, it is best to say understanding:

This structure exists in computers on the Internet, and determines the actions of computers on the network.

2.2 terms

The name of a data block varies depending on the protocol stack. Here is a summary: in Ethernet, it is called an Ethernet frame. in IP, it is called an IP packet. If the data is generally called a UDP datagram between IP and UPD, if data is between IP and TCP, it is called a TCP segment or message. when data is in an application, it is called an application message. This definition is not absolute. Different articles may have different opinions.

2.3 Data Streams

Data Streams flow from applications to TCP or UDP. We usually know that FTP uses the TCP protocol, while SNMP uses the UDP protocol. Data flows from different protocol modules to the same Ethernet adapter. The adapter transmits data to the network media. The above process is reversed at the receiver.

The Ethernet frame is transmitted to the ARP or IP module, and the data in the Ethernet frame determines whether the data is processed by the IP address or ARP. If the packet is for IP address processing, the IP module directly transmits the packet to TCP or UPD. The data in the UDP packet determines which application at the upper layer of the UPD protocol should receive the data, which is consistent with TCP. When data is transferred from an application to the network, the process is relatively simple. Each layer adds its own packet header information to the data and sends it to the next layer. Although the Internet supports a variety of network media, we generally use Ethernet as an example. Here, we need to remember that the ethernet address is unique and globally unique. The computer also has a four-byte IP address, which is used to mark the IP address of the IP module. However, for the Internet, the IP address is not necessarily unique. A running computer usually knows its own IP address and ethernet address.