计算机英语cha-14-14.2.ppt

计算机文化基础 * PART Ⅲ APPLICATIONS CHAPTER 14 COMPUTER NETWORKS 14.2 ARCHITECTURE OF COMPUTER NETWORKS chapter 14-14.2 1.1 COMPUTER HARDWARE *Main point Main point: ● Concept of architecture of computer networks ● The OSI Reference Model ● The TCP/IP Reference Model 计算机英语（第三版） 14.2 ARCHITECTURE OF COMPUTER NETWORKS 计算机英语（第三版） 原因状语从句 Computer network is a complex consisting of two or more connected computing units, it is used for the purpose of data communication and resource sharing. Design of a network and its logical structure should comply with a set of design principles, including the organization of functions and the description of data formats and procedure. This is the network architecture and so called as a set of layers and protocols, because the architecture is a layer-based. In the next two sections we will discuss two important network architectures, the OSI reference model and the TCP/IP reference model. 计算机英语（第三版） *?1 原因状语从句 ?1 ● What contents should be included in the design principles of a computer network ? 1.The OSI Reference Model The OSI model is shown in Fig.14-2 (minus the physical medium). This model is based on a proposal developed by the International Standards Organization (ISO) as the first step toward international standardization of the protocols used in the various layers. The model is called the ISO OSI (Open System Interconnection) Reference Model because it deals with connecting open systems—that is, systems that are open for communication with other systems. 计算机英语（第三版） *?2,?3 宾语从句 ?2 ● What does the “Open” mean? 原因状语从句 We will usually just call it the OSI model for short. The OSI model has seven layers. Note that the OSI model itself is not a network architecture because it does not specify the exact services and protocols to be used in each layer. It just tells what each layer should do. However, ISO has also prod