Information Technologies -- Computer Networks 林永松 台灣大學資訊管理學系 (02)

1-2 Syllabus l Textbook: n “Computer Networks”, 4 rd Ed., by Andrew S. Tanenbaum, carried by 新月 l Course objectives n to introduce the importance of computer networks n to discuss hardware, software and architecture issues for computer networks n to discuss essential layers that constitute a protocol stack n to discuss a number of applications over networks n to introduce methodology for network planning & management n to train executive professionals who need to know computer networks

1-3 Syllabus (cont’d) l Course outline (tentative) n introduction –uses of computer networks –network hardware –network software –reference models –network standardization

1-4 Syllabus (cont’d) l Course outline (cont’d) n physical layer –the theoretical basis for data communication –transmission media –wireless transmission –the telephone system n data link layer –data link layer design issues –error detection and correction –elementary data link protocols –sliding window protocols

1-5 Syllabus (cont’d) l Course outline (cont’d) n medium access sublayer –the channel allocation problem –multiple access protocols –IEEE standard 802 for LANs and MANs

1-6 Syllabus (cont’d) l Course outline (cont’d) n network layer –network layer design issues –routing algorithms –congestion control algorithms –internetworking –the network layer in the Internet n transport layer –the transport service –elements of transport protocols –the Internet transport protocols (TCP and UDP)

1-7 Syllabus (cont’d) l Course outline (cont’d) n application layer –network security –SNMP - simple network management protocol –Content-based information retrieval/filtering –multimedia n network planning and capacity management –network planning –network capacity management n other materials

1-8 Introduction l Uses of computer networks n resource sharing n information retrieval n information distribution n communication n reliability/survivability/availability n gradual growth n performance to cost ratio

1-9 Introduction (cont’d) l Network hardware n network classification –broadcasting, multicasting and unicasting (point-to-point) –scale of interconnected processors Fig. 1-2 (p. 8)

1-10 Introduction (cont’d) l Network hardware (cont’d) n local area networks (LANs) –size –transmission technology –medium access protocols –topology Fig. 1-3 (p. 9)

1-11 Introduction (cont’d) l Network hardware (cont’d) n metropolitan area networks (MANs) –characteristics –DQDB (distributed queue dual bus) Fig 1-4 (p. 11)

1-12 Introduction (cont’d) l Network hardware (cont’d) n wide area networks (WANs) –size –host and subnet Fig. 1-5 (p.12)

1-13 Introduction (cont’d) l Network hardware (cont’d) n wide area networks (cont’d) –circuit switching versus packet switching –topology Fig. 1-6 (p. 13)

1-14 Introduction (cont’d) l Network hardware (cont’d) n wireless networks –need for mobile and/or wireless communication Fig. 1-7 (p.14)

1-15 Introduction (cont’d) l Network hardware (cont’d) n wireless networks (cont’d) –e.g. PDAs (personal data assistants) and CDPD (cellular digital packet data) –different combinations of wired and wireless networking Fig. 1-8 (p. 15)

1-16 Introduction (cont’d) l Network hardware (cont’d) n internetworks –internet: a collection of interconnected networks, e.g. a collection of LANs connected by a WAN –Internet –subnet: a collection of routers and communication lines owned by the network operator –network: the combination of a subnet and its hosts

1-17 Introduction (cont’d) l Network software n protocol hierarchies Fig. 1-9 (p. 17)

1-18 Introduction (cont’d) l Network software (cont’d) n example information flow Fig (p.20)

1-19 Introduction (cont’d) l Network software (cont’d) n design issues for the layers –identification of senders and receivers –simplex, half-duplex and full-duplex –error control –sequencing –flow control –message length (SAR and multiplexing) –multiplexing and demultiplexing –routing

1-20 Introduction (cont’d) l Network software (cont’d) n interfaces and services Fig (p.23)

1-21 Introduction (cont’d) l Network software (cont’d) n connection-oriented and connectionless services Fig (p.25)

1-22 Introduction (cont’d) l Network software (cont’d) n service primitives Fig (p. 25)

1-23 Introduction (cont’d) l Network software (cont’d) n a simple connection-oriented service example –CONNECT.request –CONNECT.indication –CONNECT.response –CONNECT.confirm –DATA.request –DATA.indication –DISCONNECT.request –DISCONNECT.indication

1-24 Introduction (cont’d) l Reference models n OSI (Open Systems Interconnection) reference model –principles of layering l different level of abstraction l well defined functions l defining internationally standardized protocols l minimal information flow across the interfaces l appropriate number of layers

1-25 Introduction (cont’d) l Reference models (cont’d) n OSI reference model (cont’d) Fig (p.29)

1-26 Introduction (cont’d) l Reference models (cont’d) n OSI reference model (cont’d) Fig (p.34)

1-27 Introduction (cont’d) l Reference models (cont’d) n TCP/IP reference model Fig (p.36)

1-28 Introduction (cont’d) l Reference models (cont’d) n TCP/IP reference model (cont’d) Fig (p.37)

1-29 Introduction (cont’d) l The Internet n a collection of interconnected TCP/IP networks n to be on the Internet, a machine must –run the TCP/IP protocol stack –have an IP address –be able to send IP packets to all the other machines on the Internet n applications: , news, telnet, ftp, SNMP, WWW n millions of hosts and tens of millions of users

1-30 Introduction (cont’d) l The Internet (cont’d) n standard organizations –IAB (Internet Activities Board) by DoD in 1983, later changed to Internet Architecture Board, using RFCs (Request For Comments) for communication –IRTF (Internet Research Task Force) and IETF (Internet Engineering Task Force) under IAB in 1989 –Internet Society in 1992 –from a proposed standard to a draft standard and finally to an Internet standard