Network beginners need to master internet protocols

To master internet protocols, it is essential to have a layered understanding of the network structure. Now let's analyze this topic. First, let's introduce today's topics from some basic concepts of the Internet ...... To enable data transmission across the Internet, typical distributed platforms such as J2EE all need support from Internet protocols. For cross-Internet data transmission, Internet protocols are crucial. Internet protocols usually define standards for communication between different components in a distributed system and between remote components. Like other traditional protocols, Internet Protocols define the format and sequence of information exchange between two or more communication entities, and defines the transmission and/or acceptance behavior of messages or events [Kurose 2003].

The most important protocol in Internet protocols is the transfer control protocol and the Internet Protocol collectively referred to as the TCP/IP protocol ). The IP protocol is the basic protocol of the internet for the unreliable transmission of packets between different hosts. The IP protocol does not guarantee whether or not the packets are delivered for a certain period of time, nor whether the receiving sequence and sending sequence of the packets are consistent when multiple packets are sent. TCP adds the concept of connection and reliability. For cross-network communication, especially cross-Internet communication, TCP/IP provides reliable transmission of data streams.

To identify a Computer Host in the interconnected network, you must assign an IP address to each host ). The IP address uniquely identifies each host on each network and Internet. The IP address consists of a network identifier and a host identifier. The network identifier in the IP address identifies the network in the Internet. This identifier is assigned by the Internet authority and is unique across the Internet. The host identifier in the IP address is assigned by the organization that controls the network. In fact, IP addresses can be divided into three types, which are used for large networks, medium networks, and small networks. The number of large networks is small, the number of medium-sized networks is medium, and the number of small networks is large.

Before further analyzing the TCP/IP protocol, we will first outline the layers in the Open System Interconnection Model (OSI model) of the International Organization for Standardization. Understanding the layers in OSI is critical to understanding the layers in the TCP/IP model.

OSI reference model

Different systems can be distributed on the network and digital communication can be performed between application processes running on these systems. The OSI reference model is an abstract description of such digital communication. The Reference Model is also a conceptual blueprint for how to communicate. The reference model involves all the processing steps required for efficient communication, and groups these processing steps according to the logical relationship. These groups are called layers respectively. When the communication system is designed in this way, it is called a hierarchical architecture.

As shown in Table 2.1, the OSI model is a layer-7 hierarchy. Each layer provides requested value-added services to the directly adjacent layer. In turn, each layer puts forward some basic service requests to the next layer directly adjacent to it. The layers of OSI are as follows.

Physical Layer or the first layer): This is the lowest layer of the ISO/OSI reference model, it specifies the electrical, mechanical, process, and functional requirements required for the physical link between the activation, maintenance, and release of the terminal system.

Data link layer or Layer 2): This layer provides methods for transferring data between network entities, as well as detection and even possible repair of physical layer errors. The data link layer provides physical transmission, network topology, and traffic control for data and Error notifications. The data link layer divides messages into formatted data blocks. Each data block is called a data frame. The data of each data frame is composed of two parts: the frame header and the frame data. The frame header includes the source address of the sending host of the data frame and the target address of the receiving host.

Layer 3): This layer responds to the service request of the transport layer directly adjacent to the network layer, and sends the service request to the data link layer. The network layer of the Internet protocol can transmit variable-length data packets from the source node to the target node through one or more networks. Features provided by this layer include: network routing, traffic control, group package and package splitting, and error control.

Transport layer Layer): This layer responds to the Session Layer is directly adjacent to the transport layer on the upper layer) of the service request, and sends the service request to the network layer. The role of the transport layer is to provide transparent data transmission between end users. The transport layer is responsible for segmented upper-layer data and provides reliable or unreliable transmission. The transmission efficiency is higher ). Users can request reliable data transmission between different systems. The Transport Layer ensures data integrity through traffic control and reliable data transmission.

Session Layer 5): The Session Layer provides a session management mechanism between end-user application processes to establish, manage, and terminate sessions between presentation layer entities. This layer coordinates the communication between systems and provides three different modes for organizing communication: Single-work, half-duplex, and full-duplex. The Session Layer can insert verification points in the data and terminate or restart the session process.

Presentation Layer 6): the presentation layer represents data for the application layer, and provides data conversion and code formatting. The main features of the presentation layer include data compression and recovery, and data encryption and decryption.

Application Layer 7): the application layer is the highest level in the ISO/OSI reference model. The application layer provides an interface for an application to access the OSI network and complete the public application services required by the application. For two application processes that communicate, the Public Application Service provides syntax conversion.

Communication, traffic control, and error handling required for cross-network end-to-end data transmission from the first layer to the fourth layer. There can be many different types of physical networks under the transmission layer of the Internet protocol, such as X.25 Packet Exchange data network PSDN) or LAN ). Layer 5 to Layer 7 process cross-network application coordination and how to express information to the application. For many applications that provide different types of end-user services, the Universal Transport Layer implementation can support these applications.