Overview of Computer Network

Computer network Overview 1. There are six articles in the previous "Computer Network" series, they are "Overview", "Physical Layer", "data link layer", "Network Layer", "Transport Layer", and "Application Layer". The transport layer is also called the transport layer, which is also called the transport layer in this series ". This series is written in the "Computer Network (version 5th)" published by Xie xiren's Electronic Industry Publishing House. The main content is my summary and experience in the course of learning this book, this course is mainly used by students who have already studied this course at the end of the course and for postgraduate review. If there is no foundation, it is best to refer to a textbook, such as "Computer Network" (Pan aimin), "Computer Network" (Xie xiiren), and "TCP/IP explanation Volume 1: agreement (fan Jianhua) and other classic books. There are three main architecture of computer networks: Open Systems interconnectivity Basic Reference Model OSI/RM (Open Systems InterconnectionReference Model) the layer-7 protocol, the layer-4 protocol of TCP/IP, and the layer-5 protocol for learning (as shown in ). This series adopts the same five-layer protocol as textbooks. Finally, I hope that the series of articles I will summarize after the end of the final exam will help you and myself learn the computer network architecture in the future. Due to my limited level, it is inevitable that there may be errors and incomplete content in this article. I also hope that you will not give me any further information to correct and supplement it. 2. Internet is the world's largest interconnected network. The network connects many computers, while the Internet connects many networks. The development of the Internet is divided into three stages: from a single ARPANET to the Internet, the establishment of a three-level structure of the Internet (backbone network, regional network and campus network), the formation of a multi-layer ISP (Internet Service Provider) structure of the Internet. The Internet is divided into the edge part (host) and core part (network and router ). In essence, the end system of the edge part communicates with the client server (C/S. The customer is the service requestor, and the server is the service provider. Customer programs have two features: Proactive request to the server (the address of the server program must be known), no special hardware and a complicated operating system. The server program has three features: it can simultaneously process requests from multiple customers and passively wait for communication requests (no need to know the client program address) generally, powerful hardware and advanced operating system support are required. The Internet uses the group exchange (storage and forwarding) technology. Iii. Computer Networks the simplest definition of computer networks is a set of interconnected and autonomous computers. According to different scopes, the computer Network can be divided into the following four types: (1) WAN (Wide Area network), also known as longhaul Network), the task is to transport the data sent by the host through a long distance; (2) Metro MAN (Metropolitan AreaNetwork) generally uses Ethernet technology to interconnect multiple Local networks. (3) The Local Area Network (LAN) has a small range. (4) the Personal Area Network (PAN) is often referred to as the Wireless Personal Area Network (WPAN). It uses Wireless technology and has a range of about 10 MB. Computer network performance indicators include the following seven commonly used: Speed (B/s), bandwidth (B/s) (communication line capability), throughput (B/s) (instant) latency (s) (transmission + propagation + Processing + queuing), latency bandwidth product (B) (propagation latency × bandwidth), Round-trip time RTT (Round-TripTime) (s) and utilization. Network protocols are rules, standards, or conventions established for data exchange in the network. It consists of three elements: syntax, semantics, and synchronization. Protocol layering has the following benefits: the layers are independent, flexible, can be split up on the structure, easy to implement and maintain, can promote standardization. The difference between a protocol and a service is that the Protocol is "horizontal", which is a set of rules for communication between two peer layers. Services are provided from the next layer to the next layer. The Protocol at this layer enables this layer to provide Abstract Services to the next layer. The architecture of a computer network is a collection of various layers of the computer network and their protocols, that is, the precise definition of the functions of the computer network and its components. Finally, let's briefly introduce the layer-5 protocol. (1) the application layer directly provides services for your application processes; (2) the transport layer provides services for communications between processes on both hosts. Reliable Transmission Control Protocol (TCP) and unreliable User Datagram Protocol (UDP); (3) network layer (networklayer) provides communication services for different hosts on the group exchange network, and selects appropriate routes. The Network Layer encapsulates the packet segments of the transport layer into packages. (4) when the data link layer transmits data between two adjacent nodes, the data link layer assembles the IP data packets handed over by the network layer into frames, and transparently transmits data in frames on the links between two adjacent nodes. (5) Physical Layer (physicallayer) A task transparently transmits bits.