公务员考试行测真题答案及解析1.ppt

Reference Models (3) Protocols and networks in the TCP/IP model initially. Comparing OSI and TCP/IP Models Concepts central to the OSI model Services Interfaces Protocols A Critique of the OSI Model and Protocols Why OSI did not take over the world Bad timing Bad technology Bad implementations Bad politics Bad Timing The apocalypse of the two elephants. A Critique of the TCP/IP Reference Model Problems: Service, interface, and protocol not distinguished Not a general model Host-to-network “layer” not really a layer No mention of physical and data link layers Minor protocols deeply entrenched, hard to replace Hybrid Model The hybrid reference model to be used in this book. Example Networks The Internet Connection-Oriented Networks: X.25, Frame Relay, and ATM Ethernet Wireless LANs: 802:11 The ARPANET (a) Structure of the telephone system. (b) Baran’s proposed distributed switching system. The ARPANET (2) The original ARPANET design. The ARPANET (3) Growth of the ARPANET (a) December 1969. (b) July 1970. (c) March 1971. (d) April 1972. (e) September 1972. NSFNET The NSFNET backbone in 1988. Internet Usage Traditional applications (1970 – 1990) E-mail News Remote login File transfer Architecture of the Internet Overview of the Internet. ATM Virtual Circuits A virtual circuit. ATM Virtual Circuits (2) An ATM cell. The ATM Reference Model The ATM reference model. The ATM Reference Model (2) The ATM layers and sublayers and their functions. Ethernet Architecture of the original Ethernet. Wireless LANs (a) Wireless networking with a base station. (b) Ad hoc networking. Wireless LANs (2) The range of a single radio may not cover the entire system. Wireless LANs (3) A multicell 802.11 network. Network Standardization Who’s Who in the Telecommunications World Who’s Who in the International Standards World Who’s Who in the Internet Standards World ITU Main sectors Radiocommunications Telecommunications Standardization Development Classes of Members National