2. 7-1 Establishing Communication Channels: Completing the Physical Layer Chapter 4

3. Knowledge Checkpoints  Be able to identify major hardware components of a network Hub Server Nodes  Remote access  Connection vs connectionless

4. Important Goals for Networks  Faster  More efficient  More reliable  More secure

5. What Does a LAN Do?  Information sharing Allows sharing of same data files Exchange of information via e-mail Pass-thru to the Internet for information  Resource sharing Enables sharing a hardware device (e.g., printer) Software packages used by many users on the network Improves storage space Provides daily back-up

6. Why Use a LAN?  Saves Money!  Sharing hardware is cheaper  Network versions of applications are cheaper  Productivity improves with common access  Increased security

7. LANs often Link to Legacy Systems

8. What is Telnet?  Terminal emulation program (client-server)  Interactive session with a server  Port 23/24  Try open cyberspace.org  At login type newuser

9. Using Telnet

10. Sharing Software on a LAN  LAN metering software prohibits using more copies of a package than there are installed licenses  The Software Publishers Association (SPA) estimates that about 40% of all the software in the world is used illegally Utah has the largest amount of unlicensed software in use – next to P.R. China! SPA has undertaken an aggressive software audit program to check the number of illegal software copies on LANs.

11. LANs Carry Identifiable Traffic

12. Dedicated Server LANs  A dedicated server LAN has one or more computers that are permanently assigned to being the network server(s) for one (or more) activities  In a dedicated server LAN, the server’s usual operating system is replaced by a network operating system

13. Dedicated Server LANs  File servers - allow many users to share the same set of files on common, shared disk drive(s)  Database servers - not only provides shared access to the database on the server, but also can perform database processing on those files associated with client-server computing

14. Dedicated Server LANs  Print servers -handle print requests on the LAN from multiple users on the network  Communications servers - are dedicated to performing communications processing Examples are : Fax servers - manage fax boards Modem servers - for dialing out of the network Remote access servers - for dialing into the network Middleware servers –for managing communications and transaction load

15. LAN Components There are 5 basic components to a LAN  Client (node)  Server  Network Interface Cards (NICs)  Network Cables and Hubs  Network Operating Systems (NOS) Where Do you Start?

16. Components of a 10BaseT Network

17. Network Interface Cards The Network Interface Card (or NIC) allows the computer to be physically connected to the network cable, which provides the physical layer connection among computers in the network

18. NICs

19. NICs Match the Network

20. Putting it Together

21. Network Cables and Hubs  Each computer must be physically connected by network cable to the other computers in the network  The selection of a LAN can be influenced greatly by the type of cable that already exists where the LAN is to be installed

22. Network Cable Most LANs are formed with a blend of unshielded twisted pair (UTP) wire, shielded twisted pair (STP), coaxial cable, and fiber optic cable.

23. Cable Limits the Distance of a LAN

24. Types of Fiber Optic Connectors SC Stick & Click ST Stick & Turn

25. Network Configuration  There are two fundamental network configurations: Point-to-point configuration (2-point) - sometimes called dedicated circuits Multipoint configuration (or multidrop)

26. Connectivity

27. Media Selection Criteria Cost Speed Distance and expandability Environment Security

28. Network Hubs Network hubs go by many names depending on the type of network and the specific vendor Concentrator Multistation access unit (MAU) Transceiver Repeater

29. Network Hubs Network hubs serve two purposes: They provide an easy way to connect network cables Hubs act as repeaters or amplifiers to prevent attenuation Some hubs are “smart”, because they can detect and respond to network problems, as well as have managed ports

30. Connecting to a NIC

31. Hubs  Come in common speeds to match NICs 10, 100, 10/100, 1000  Variable number of connection ports 8, 16, 24

32. Hubs Single-hub (repeater) or single-switch LAN Share speed of network 200 meter maximum distance span between farthest two stations with UTP What is a USB hub? 100 m X Y 200 m

33. How Hubs Work

34. Ethernet 802.3 Physical Layer Topology : Order in which stations receive bits Ethernet hubs use a bus topology Signal is broadcast All stations receive almost simultaneously

35. Hubs Multiple-hub LANs Increase maximum distance span 100 m

36. Multiple Hubs in 10Base-T  Farthest stations in 10Base-T can be five segments 500 meters apart 100 meters per segment Separated by four hubs 100m 500m, 4 hubs 10Base-T hubs

37. Multiple Hubs in 10Base-T  Practical Limit in 10Base-T is Number of Stations Degradation of service beyond 100 stations Unacceptable service beyond 200 stations Maximum possible span normally includes no more than 200 stations In 10Base-T, the number of stations is the real limit to distance spans It is possible to have a LAN with more than a 200 meter maximum span

38. Physical Layer: 802.3 UTP Standards Wiring 100 meters maximum UTP distance hub-to-station or hub-switch 200 meters maximum distance between stations 100 m 200 m

39. Mixing Circuit Media

40. Hooking up a Network

41. Connections Through a Hub

42. Multiple Hubs in 100Base-TX  Limit of Two Hubs in 100Base-TX Must be within a few meters of each other Maximum span is 200 meters Shorter maximum span than 10Base-T 100m 2 Collocated Hubs 100Base-TX Hubs ~200 m

44. How Would You Wire This?

45. Business Issues & Remote Access  Cost of offices vs cost of remote set-up  Employee access to network services  Customer access/service

46. Categories of Remote Access  Telecommuting Costs – connect charges, equipment, wiring  Mobile computing Anywhere communication  Technical Support Costs of on-site service

47. Design Steps for Dial-up  Needs analysis (who do you talk to?)  Logical topology  Physical topology  Current technology review

48. Needs Analysis  What applications should be accessed by dial up?  Who will dial up?  Is there a business benefit?  How many will use the dial up?  Special access required?

49. Logical Topology  Remote node Operate as locally connected Applications run on remote PC Minimize downloads  Remote control Simulates a PC attached to the network Drives are mapped to network

50. Remote Node vs. Remote Control Installations

51. Security Issues & Remote Access  Password management Verifying employee access  Locking accounts Multiple tries may be a hacker  Separation of data Original data should be stored behind a firewall  Encryption Preventing “sniffing”  Dial-back Insure correct user  Authentication Device or software?

52. Physical Design Options  Dedicated PC  Communications server  LAN modem

53. Physical Topology: Alternative Access Points

54. Network Access Methods  PSTN Modem @ 56Kbps Analog  ISDN ISDN modem Digital  XDSL DSL modem Digital service on top of PSTN  VPN Secure communication channel VPN software, ISP

55. Alternative Network Access Services

56. Remote Access Hardware  Communication servers Simultaneous logins Monitor with phone lines Requires multiple NICs to network resources Modems connect to serial ports Can be used for remote control applications in lieu of PCs Acts as a gateway

57. Remote Node Server Solutions  Software-only  Turnkey hardware (integrated modems)  LAN modems (dial-up servers)  Monster RAS

58. Remote Node Software  Common software include Windows NT RAS and Netware Connect  Client OS compatibility

59. Communications Server Components

60. Remote Control Software  Taking over a remote PC  Software on guest and host systems  Lock-ups of host PCs  Disable monitor and keyboard  Virus detection  Popular packages include, PCAnywhere and LapLink

61. Remote Node Server Software Characteristics  NOS protocols supported  Support for modem pools & dial out  Management of time limits  Security with forced password & token authentication  Client platforms

62. Circuit & Packet Switching  Differences center on voice and data transmission  Circuit switching Continuous, exclusive, temporary Low latency and few delays  Packet switching Data transmitted in a container (packet) Routed base on header information Routers distribute data to appropriate destination

63. Issues to Consider  Designing a network is a multi-step process  The use of the network is important  How users access the network is important  The type of data will determine the speed