1. Introduction Chapter 1 Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

2. دیباچه درخت چنار تنومند تنها روی تپه ایستاده بود. صدها سال بود که آنجا بود و گویی تا ابد نیز قرار بود بماند. ریشه هایش همچون پنجه ای آهنین در اعماق خاک فرو رفته بود؛ آنچنان که گویی کسی را یارای برکندن آن نیست. یک شب صاعقه ای درخت را به دو نیم کرد؛ درخت از درون کاملاً تهی و پوسیده بود. آین راند (اطلس شانه بالاانداخت)

3. Uses of Computer Networks Business Applications Home Applications Mobile Users Social Issues Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

4. Business Applications (1) A network with two clients and one server The server can also be a local printer Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

5. Business Applications (2) * The client-server model involves requests and replies * Business Networks can be joined by VPNs Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

6. Business Applications (3) Setting up a communication medium: Email Service Phone Service: VoIP Video Conference Desktop Sharing: Interactive team working Telemedicine Remote patient monitoring e-commerce Electronic shopping, ticket booking, … Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

7. Home Applications (1) o Gaming o TV, Radio o Photo and Video editing o Music o Internet connection o Online news o Online digital library : ACM, IEEE, … o Ubiquitous computing: Smart homes, smart metering systems, … o Power-line networks o Zigbee networks o RFID technology a)Metcalfe’s law: the value of a network is proportional to the square of the number of users Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Internet of Things (IoT)

8. Home Applications (2) * In a peer-to-peer system there are no fixed clients and servers. * BitTorrent is an example Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

9. Home Applications (3)  Instant Messaging: sms, mms, …  Multiperson messaging: Twitter, Viber, Telegram, …  Audio & video Sharing: YouTube, Facebook, Instagram, …  Colaborating content creation: Wikipedia  e-commerce: Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

10. Mobile Users Combinations of wireless networks and mobile computing Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

11. Mobile Users (1)  Smart Phones : 3G, 4G Mobile networks  Global positioning system (GPS) + google map  m-commerce (mobile commerce)  Sensor Networks : traffic monitoring, …  Vehicular networks  Wearable computers : smart watches, … Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

12. Social Issues Spreading wrong or offensive political or religious views Censorship Content pricing or Network neutrality Digital Millennium Copyright Act Employee-Employer issues Content overhearing (e.g. by government) Profiling users: internet cookies misleading information Spam Electronic viruses Phishing confidential information (e.g. bank acounts) e-gambling Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

13. Network Hardware Transmission technology broadcast: shared media e.g. wireless links point-to-point (unicast): multihop, routing Scale Personal area networks Local area networks Metropolitan area networks Wide are networks internetwork (the Internet) Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Single target Multicast Broadcast

14. Personal Area Network Bluetooth PAN configuration Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

15. Local Area Networks (a)802.11 (WiFi) (b) Switched Ethernet. (802.3) *Virtual LAN (VLAN) *Static or Dynamic Medium Access Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Centralized Decentralized

16. Home Networks Requirements 1.Easy to use devices 2.Reliable work 3.Low price 4.Compatibility 5.Security Technologies a)Wireless b)Wired c)Power-line Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

17. Metropolitan Area Networks A metropolitan area network based on cable TV * WiMAX (802.16) is another example Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

18. Wide Area Networks (1) WAN that connects three branch offices in Australia * The transmission lines may be: telephone wires, optical fibers, or wireless (e.g. Satellite) links Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

19. Wide Area Networks (2) WAN using a virtual private network (VPN). Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

20. Wide Area Networks (3) WAN using an ISP network. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

21. Network Software Network architechture: multiple layers abstracted from each other Protocol stack: agreement between same layer parties Protocol replacement: must be done without changing the service Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

22. Protocol Hierarchies (1) Layers, protocols, and interfaces. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Layer1 peer

23. Protocol Hierarchies (2) The philosopher-translator-secretary architecture Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

24. Protocol Hierarchies (3) Example information flow supporting virtual communication in layer 5. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

25. Design issues for the layers 25 Reliability: Addressing Internetworking: Packet shaping Scalability Resource Allocation Flow or Congestion Control Quality of Service (QoS) Security Error detection Error correction Routing

26. Connection-Oriented Versus Connectionless Service Six different types of service. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Telephone like Mail like

27. Service Primitives (1) Six service primitives that provide a simple connection-oriented service * Primitives run as system calls on an operating system Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

28. Service Primitives (2) A simple client-server interaction using acknowledged datagrams. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

29. The Relationship of Services to Protocols The protocol peers are like objects in a program. The services are like object functions. The protocols are like object definitions. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

30. Reference Models OSI reference model: Valid model from ISO but unused protocols Open System Interconnection (1983 developed, 1995 revised) Bit Transmission Error+ Framing+ mac Routing+ congestion+ Connection+ address Establish e2e connection Multiple sessions on a connection Data structuring Networked Apps. like HTTP

31. TCP/IP Model Base of ARPANET (Introduced 1974, Standardized 1989) 31

32. TCP/IP Protocols 32

33. The preferred reference model Used in this class 33

34. Example networks - Internet a)Telephone based network b) proposed distributed system for ARPANET (Advanced Research Projects Agency) 34

35. The original ARPANET design IMP :Interface Message Processor 35 56 Kbps

36. 36 TCP/IP developed in 1974

37. NSFNET * National Science Foundation TCP/IP network that was connected to ARPANET in the Carnegie-Mellon. 37 * NSF encouraged MERIT, MCI, and IBM to form a nonprofit corporation, ANS (Advanced Networks and Services), as the first step along the road to commercialization.

38. Internet architecture -DSLAM (Digital Subscriber Line Access Multiplexer) -CMTS (Cable Modem Termination System) -POP (Point of Presence) - IXPs (Internet eXchange Points) 38

39. Example networks- Mobile network 1)First generation: analog voice transmission - AMPS(Advanced Mobile Phone System)- 1982 2)Second generation: digital voice and SMS- GSM(Global System for Mobile communications)- 1991 3)Third generation: broadband data- UMTS(Universal Mobile Telecommunications System) + WCDMA(Wideband Code DivisionMultipleAccess)- 2001 4)Forth generation: higher bandwidth – WiMAX (802.16) + LTE (Long Term Evolution)- 2011 39

40. Cellular network and frequency reuse 40

41. UMTS 3G architecture -RNC(Radio Network Controller) -MSC(Mobile Switching Center)- GMSC(Gateway Mobile Switching Center) -MGW(Media Gateway)- PSTN(Public Switched Telephone Network) -SGSN(Serving GPRS Support Node)- GGSN(Gateway GPRS Support Node) -HSS(Home SubscriberServer) 41

42. Mobility and Handover 42

43. Network example- Wireless LAN *IEEE 802.11 or WiFi *ISM (Industrial, Scientific, and Medical)band = 902-928 MHz, 2.4- 2.5 GHz, 5.725-5.825 GHz 43 a) WLAN with access pointb) 802.11 in ad hoc mode

44. Multipath fading in WLANs a)802.11 : 1-2 Mbps b)802.11b : 11 Mbps by spread spectrum c)802.11a,g: 54 Mbps by OFDM (Orthogonal Frequency Division Multiplexing) d)802.11n (2009) : 450 Mbps by using multiple antennas 44

45. CSMA (Carrier Sense Multiple Access) Hidden terminal problem 45

46. WLAN Security a)WEP (Wired Equivalent Privacy) b)802.11i: WiFi Protected Access (WPA, WPA2) 46

47. Network example- RFID Radio Frequency IDentification (RFID) 47 Passive Active UHF: 902-928 MHz HF : 13.56 MHz

48. Network example- Sensor Networks Multihop topology of a sensor network 48

49. Network standardization a)ITU (International Telecommunication Union): 200 governments –ITU-T: telecommunications –ITU-R: radio communications –ITU-D: developement b)ISO (International Standards Organization): 157 members e.g. ANSI (U.S.), BSI (Great Britain),… –CD (Committee Draft)  DIS (Draft International Standard)  IS (International Standard) c)NIST (National Institute of Standards and Technology) d)IEEE (Institute of Electrical and Electronics Engineers) 49

50. IEEE 802 standards 50

51. Internet standardization 1) IAB (Internet Activities Board) www.ietf.orgwww.ietf.org RFCs (Request For Comments) 2) World Wide Web Consortium (W3C): 300 member 51 IRTF (Internet Research Task Force) IETF (Internet Engineering Task Force)

52. Metrics for network speed Kilo = 2e10 = 1024 Mega = 2e20 = 1,048,576 Giga = 2e30 = 1,073,741,824 Tera = 2e40 = 1,099,511,627,776 52 Metrics for memory size

53. Home work assignment StudentAssigned problems 1 2023221830312123371 2 3582115363324222034 3 24283325133722278 4 36910282512335374 5 9341220173314271112 6 261051331232281617 7 11293562937193184 8 25724227208322937 9 2611181032185353113 10 342423730837412 11 1022212820963273 12 92624933197301412 13 2521 17223421932 14 321627266222472019 15 1324201483211151329 16 292437281628205724 17 2526915282226284 18 12442631101935343 19 2335527302520122529 20 15831712417111834 21 342715120245133420 22 191713425191845 23 185141652832242831 24 16232911633 12813 25 1817248263711322111 26 291729311929821728 27 122535168222132231 28 3029363319352413122 29 18138156221617525 30 2256293183823 31 71626153253673420 32 27324302132425327 33 183120283518413927 34 61020142632634229 35 1323328228751711