Information Technologies Computer Networks yslinim ntu edu tw

Information Technologies -Computer Networks 林永松 台灣大學資訊管理學系 yslin@im. ntu. edu. tw (02)3366 -1191

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

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

Syllabus (cont’d) l Course outline (cont’d) n physical – – layer 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 4

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 5

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) 6

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 – network planning – network capacity management n other management materials 7

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 8

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) 9

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) 10

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

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

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) 13

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

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) 15

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 16

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

Introduction (cont’d) l Network software (cont’d) n example information flow Fig. 1 -11 (p. 20) 18

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 19

Introduction (cont’d) l Network software (cont’d) n interfaces and services Fig. 1 -12 (p. 23) 20

Introduction (cont’d) l Network software (cont’d) n connection-oriented and connectionless services Fig. 1 -13 (p. 25) 21

Introduction (cont’d) l Network software (cont’d) n service primitives Fig. 1 -14 (p. 25) 22

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

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

Introduction (cont’d) l Reference models (cont’d) n OSI reference model (cont’d) Fig. 1 -16 (p. 29) 25

Introduction (cont’d) l Reference models (cont’d) n OSI reference model (cont’d) Fig. 1 -17 (p. 34) 26

Introduction (cont’d) l Reference models (cont’d) n TCP/IP reference model Fig. 1 -18 (p. 36) 27

Introduction (cont’d) l Reference models (cont’d) n TCP/IP reference model (cont’d) Fig. 1 -19 (p. 37) 28

Introduction (cont’d) l The Internet na 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: email, news, telnet, ftp, SNMP, WWW n millions of hosts and tens of millions of users 29

Introduction (cont’d) l The Internet (cont’d) n standard organizations – IAB (Internet Activities Board) by Do. D 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 30