CS412 Introduction to Computer Networking & Telecommunication

1. CS412 Introduction to Computer Networking & Telecommunication Introduction Chi-Cheng Lin, Winona State University

2. Topics • Introduction • Metric Units • Network Hardware • Network Software • Reference Models • Example Networks • Standards and Standards Organizations

3. Introduction • First two decades of computing • Highly centralized computer systems • Now • A large number of SEPARATE but INTERCONNECTED computers => Computer networks

4. What is Computer Network? • An INTERCONNECTED collection of AUTONOMOUS computers • Interconnected: Able to EXCHANGEINFORMATION via transmission media • Media: copper wire, fiber optics, microwaves, communication satellites • Autonomous: no master/slave relation • NOT autonomous: • One computer can control another one • e.g., a large computer with remote printers and terminals

5. What is Telecommunication? • What is data communication? • Exchange of data between two devices via some form of transmission media • Data are represented by bits – 0s and 1s • What is telecommunication? • Exchange of information over distance using electronic equipment

6. What is Telecommunication? • Components of data communication • Sender, receiver, medium, message, and • Protocol: set of rules governing data communication • Key elements of a protocol • Syntax • Structure/format • Semantics • Meaning • Timing • When and how fast

7. Figure 1.1Five components of data communication

8. Why Studying CS412? • The instructor looks nice … (Don’t bet on it!) • It is part of our daily life now • The job market is good … (?) • You want to understand concepts and technologies of networking and telecom • Theory and practice • It is one of the most drastically changing field in CS and you like challenges • It makes you knowledgeable in this field • It is FUN!!

9. Distributed System vs. Computer Network • Distributed system • TRANSPARENCY • A collection of independent computers appear as a single coherent system • Single model/paradigm to users • Middleware on top of OS • Example? • Computer network • No such coherence, model, middleware • Machines visible to users • Users log onto remote machines

10. Distributed System vs. Computer Network • A distributed system is a SOFTWARE system built on top of a network • Distinction between network and distributed system • Software (especially OS) rather than hardware • However, considerable overlap between the two subjects

11. Uses of Computer Networks • Business applications • Resource sharing • Communication medium • E-commerce • Client-server model • Client requests, server performs & then replies • E.g., one or more file servers, many clients

12. Business Applications of Networks • A network with two clients and one server.

13. Client-Server Model 1 2 3

14. Uses of Computer Networks • Home applications • Access to remote information • On-line publishing, digital library, WWW • Person-to-person communication • Email, instant messaging, peer-to-peer communication, videoconferencing, Internet phone, E-learning • Interactive entertainment • Video on demand (VOD), games • E-commerce • Home shopping, electronic banking and investment, on-line auction

15. Home Network Applications (2) • In peer-to-peer system there are no fixed clients and servers.

16. Mobile Users • Notebook, PDA, cellular phone • M-commerce • Wireless networking and mobile computing

17. Metric Units • The principal metric prefixes.

18. Network Hardware • By transmission technology • Broadcast links • smaller, geographically localized networks • Point-to-point links • larger networks • By scale • PAN • LAN • MAN • WAN

19. Classification by Scale

20. Broadcast Network • A single communication channel shared by all machines on the network • Packets (short messages) sent by any machine are “received” by all the others • Address field of packet: whom it is intended • Message transmission • Unicast: one sends, one receives • Broadcasting: one sends, all receive • Multicasting: one sends, a group receives

21. Point-to-Point Networks • Many connections between pairs of machines • Intermediate machines (called routers) might have to be visited by a packet from source to destination – more than one path is possible • Routing algorithms are important • Routing: process of finding a path from a source to the destination(s) in the network

22. Local Area Network (LAN) • Private-owned Networks • Within a single building/campus • Size: up to a few kilometers • Characteristics • Size • Restricted by size  worst-case transmission time bounded and known in advance  network management simplified

23. LAN • Characteristics • Transmission technology • Machines attached to a single cable • Speed/capacity (High): 10 - 100 Mbps, Gbps • Mbps/Gbps: Megabit/Gigabit per second • 1 megabit=1,000,000 (not 220=1,048,576) bits • Delay (low): microseconds, nanoseconds • Errors: very few

24. LAN • Characteristics • Topology – the way in which a network is laid out • Examples: Bus, Ring Bus Ring

25. Figure 1.7Categories of topology

26. Figure 1.8Fully connected mesh topology (for five devices)

27. Figure 1.9Star topology

28. Figure 1.10Bus topology

29. Figure 1.11Ring topology

30. LAN - Topology • Bus (linear cable) • Only one machine can transmit at a time • Arbitration mechanism needed to resolve conflicts when two or more computers want to transmit simultaneously • Centralized or Distributed • Example: IEEE 802.3 (Ethernet): • Bus-based broadcast network with decentralized control operating at 10 Mbps to 10Gbps. • If two or more packets collide, each computer just waits a random time and tries again later.

31. LAN - Topology • Ring • Bits propagate around the ring • Arbitration mechanism is needed, too • Example: IEEE 802.5 (IBM Token Ring) • Ring-based LAN operating at 4 and 16 Mbps • Arbitration is based on “token” • Only token holder can transmit

32. LAN - Channel Allocation • Needed as all computers share one communication pathway • Static channel allocation • Divide up time into discrete intervals • Run a round robin algorithm • Allow each machine to broadcast only when its time slot comes up • Problem: Wasting channel capacity

33. LAN - Channel Allocation • Dynamic channel allocation • Centralized • A central entity determines who goes next • Decentralize • No central entity • Each machine decides for itself to transmit or not • Algorithms needed to resolve potential chaos

34. Metropolitan Area Network (MAN) • Covers city • Examples • Cable TV network • IEEE 802.16 high-speed wireless Internet access

35. Figure 1.14 MAN

36. Metropolitan Area Networks • A metropolitan area network based on cable TV.

37. Wide Area Network (WAN) • Country or continent • Components • Host (end system) • Machine running user (application) programs • Communication subnet (subnet) • Connecting hosts • Carrying messages from host to host

38. Figure 1.15WAN

39. WAN - Subnet Components • Transmission lines • Move bits between machines • Switching elements • Specialized computers that connect two or more transmission lines • Determine out going line for incoming data • ROUTER

40. WAN - Hosts and Subnet H1 R1 R2 R3 R4 R5 R6 H2 : Host : Router

41. WAN - Architecture • Contains numerous cables or telephone lines • Each cable connects a pair of routers • Two routers must communicate indirectly if they are not connected by a cable • There might be more than one route between two hosts and it might change from time to time • E.g., Route from H1 to H2

42. WAN - Architecture • An intermediate router in a WAN • Receives a packet in its entirety • Queues the packet until required output line is free • Forwards the packet • Subnet using the principle above is called • Store-and-forward or packet-switched subnet

43. Wide Area Networks • A stream of packets from sender to receiver.

44. Topology – LANs vs WANs • Local networks • Bus, Ring, Star • Tree • WANs typically irregular

45. WAN - Broadcast Systems • Satellite system • Each router has an antenna • Sometimes routers are connected to a substantial point-to-point subnet, with some of them having a satellite antenna • Inherently broadcast

46. Wireless Network • System interconnection • Example: Bluetooth • Wireless LANs • Easy to install • IEEE Standard 802.11 • Wireless WANs • IEEE Standard 802.16

47. Wireless Networks Bluetooth configuration Wireless LAN

48. Wireless Network • Combinations of wired and wireless networking (e.g., flying LAN)

49. Home Network Categories • Computers • Desktop PC, PDA, shared peripherals • Entertainment • TV, DVD, VCR, camera, stereo, MP3 • Telecomm • Telephone, cell phone, intercom, fax • Appliances • Microwave, fridge, clock, furnace, aircon • Telemetry • Utility meter, burglar alarm, babycam

50. Internetwork • What is internetwork? • A collection of interconnected networks • "Internet" and "internet" • internet: internetwork • Internet: the worldwide internetwork using TCP/IP protocol suite • Problem: Communication between networks with different SW/HW • Solution: Gateways • Machines connect different, incompatible networks • Connection and translation