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Establishing Communication Channels: Completing the Physical Layer

Establishing Communication Channels: Completing the Physical Layer. Chapter 4. Knowledge Checkpoints. Be able to identify major hardware components of a network Hub Server Nodes Remote access Connection vs connectionless. Important Goals for Networks. Faster More efficient

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Establishing Communication Channels: Completing the Physical Layer

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

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

  3. Important Goals for Networks • Faster • More efficient • More reliable • More secure

  4. 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

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

  6. LANs often Link to Legacy Systems

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

  8. Using Telnet

  9. 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.

  10. LANs Carry Identifiable Traffic

  11. 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

  12. 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

  13. 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

  14. 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?

  15. Components of a 10BaseT Network

  16. 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

  17. NICs

  18. NICs Match the Network

  19. Putting it Together

  20. 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

  21. 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.

  22. Cable Limits the Distance of a LAN

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

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

  25. Connectivity

  26. Media Selection Criteria • Cost • Speed • Distance and expandability • Environment • Security

  27. 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

  28. 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

  29. Connecting to a NIC

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

  31. 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? Y 100 m 100 m X 200 m

  32. How Hubs Work

  33. 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

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

  35. 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 100m 100m 10Base-T hubs 500m, 4 hubs 100m 100m

  36. 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

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

  38. Mixing Circuit Media

  39. Hooking up a Network

  40. Connections Through a Hub

  41. 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 2 Collocated Hubs 100m 100Base-TX Hubs 100m ~200 m

  42. How Would You Wire This?

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

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

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

  46. 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?

  47. 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

  48. Remote Node vs. Remote Control Installations

  49. 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?

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