1. TDC 461 Basic Communications Systems Local Area Networks 29 May, 2001

2. Agenda Local Area Networks –Components –Topologies –Transmission Media –Network Interface Cards (NICs) –Network Operating System software Client vs Server functions Peer-to-Peer vs. Server- based Local Area Network Technologies –Ethernet –Token Ring LAN Interconnection –LAN Switches –Routers

3. What is a LAN? Key Elements: –

4. LAN Components Workstations (PCs, etc.) – Interconnecting Cable – Network Operating System (NOS) Software

6. LAN Topologies How are Workstations connected together? –

7. Bus Topology

8. Bus Topology Example: 10Base5 Ethernet

9. Ring Topology

10. Dual Ring Example: Fiber Distributed Data Interface (FDDI) GOLDMAN: LAN Self-healing FDDI dual- attached adapters Self healed after Link Failure link failure

11. Star Topology

12. Star Topology Example: 10BaseT Ethernet

13. LAN Cable LAN Cable can be of several types: –

14. Twisted Pair Unshielded Twisted Pair (UTP) –Similar to telephone cable, but Usually 4-pair cable is used UTP Category ratings –Category 3 - 10 Mbps up to 100 meters –Category 4 - 16 Mbps up to 100 meters –Category 5 - 100 Mbps up to 100 meters Shielded Twisted Pair (STP) –

15. Coaxial Cable LAN coaxial cable is similar to Cable TV cable (and can be identical) –Construction –Advantages –Disadvantages

16. Coaxial Cable

17. Fiber Optic Cable Transmits data using light rather than electricity –Structure –Advantages –Disadvantages

18. Fiber Optic Cable

19. LAN Hardware Cabling and NIC card specs dictated by standards document for the particular LAN Access Method: –Ethernet –Token Ring –ARCNet –Fiber Distributed Data Interface (FDDI) –etc.

20. NIC Card Sales - 1Q 1998 (percentage of 10.9 millions units sold) Source: In-Stat

21. Network Operating Systems Popular NOSes: – NOS determines workstation role: –

22. Installed LAN Servers 2Q 1998 Source: Dataquest

23. New Servers Deployed Jan-June 1998 Source: Network World

24. File Servers A File Server Shared files accessed via –

25. Network Drives

26. Security Login (Log on) Network Manager controls access rights for each user to each resource.

27. File Servers

28. Example: Get File Open File File Opened Read Data Data Close File File Closed

29. NOS Types Peer-to-Peer NOS – Dedicated Server NOS –

31. LAN Standards IEEE 802 Committee Standards –802.3 - Ethernet –802.5 - Token Ring

32. LAN Standards IEEE 802 Standards include –Physical (Layer 1) Cable Types Maximum length restrictions Data rate and bit encodings –Medium Access Control (Layer 2) Access control protocol (determines which device can transmit when Frame header/trailer format

33. Ethernet Physical Standards: –10Base5 (1985) 10 Mbps Thick Coaxial Cable (Bus) –10Base2 (1988) 10 Mbps Thin Coaxial Cable (Bus) –10BaseT (1990) 10 Mbps Twisted Pair (Star)

34. Ethernet Physical Standards: –100BaseT (1995) 100 Mbps Twisted Pair (Star) –100BaseF (1995) 100 Mbps Fiber (Star) –1000BaseX (1998) 1 Gbps Fiber (Star)

35. Ethernet IEEE Naming System: – –Example: 10Base5 10 Mbps data rate Baseband signal type Longest cable length = 500 meters

36. Ethernet IEEE Naming System: – –Example: 10Base5 10 Mbps data rate Baseband signal type Longest cable length = 500 meters

37. 10Base5 Ethernet

38. 10Base2 Ethernet

39. 10BaseT Ethernet

40. 100BaseT Ethernet (Fast Ethernet) Requires high-quality (Category 5) twisted pair cabling Requires 100 Mbps NIC cards in PC workstations Requires 100 Mbps hub

41. 100BaseT Ethernet (Fast Ethernet)

42. Switched Ethernet Switched vs. shared Bandwidth to desktop Additional hardware –Switches Switched 10 Switched 100

43. Gigabit Ethernet Requires fiber optic cabling Requires Gigabit NIC cards in PC workstations Requires Gigabit Ethernet hub or Gigabit Ethernet switch

44. 1000BaseX Ethernet

45. Ethernet MAC Protocol Medium Access Control (MAC) layer protocol is identical for all Ethernets: –Ethernet Frame format –Carrier Sense Multiple Access with Collision Detection (CSMA/CD) used to determine which workstation can send at any given time.

46. Ethernet Frame Format

47. Ethernet Frame Header: –Preamble - 8 bytes - alternating 1/0 bits for clock synchronization –Dest. Address - 6 bytes –Source Address - 6 bytes –Length - 2 bytes - Packet length Trailer: –CRC - 4 bytes - Cyclic Redundancy Check

48. MAC Protocol

49. Carrier Sense Multiple Access with Collision Detection To transmit data packet: –First, listen to see if any other station is transmitting (Carrier Sense) –When network is quiet, start transmitting

50. Carrier Sense Multiple Access with Collision Detection Station Backoff –Each station involved in collision: –As number of collisions grows, range of random values (N) increases (“exponential backoff”)

51. Ethernet Enhancements Switched Ethernet – Full-duplex Ethernet –

52. Ethernet Switches Ethernet Switch –

53. Switches vs. Routers How is Switch different than a Router? –Addressing Switch uses layer 2 MAC addresses Router uses layer 3 IP address –Speed & security Switch forwards packets fast (~50-100 nsec). Router takes more time (~1-50 msec) and provides other security features

54. Switched Ethernet

55. Switches vs. Hubs How is Switch different than a Hub? –Broadcasting (and Security) Hub broadcasts every packet to every device Switch forwards packet out single port –Matching Data Rates All ports on hub must run at same data rate Switch ports can run at different rates (can buffer incoming packet at one data rate and re-transmit at another data rate).

56. Full-Duplex Ethernet Full-Duplex Ethernet allows a workstation to send and receive data simultaneously. Requirements –Must have a full-duplex NIC card –Must be connected to Ethernet switch

57. Switched Hierarchy Switches allow network manager to put bandwidth where it is needed. –Some users get 10 Mbps shared (hub) –Some users get 10 Mbps dedicated (switch) –Some users get 100 Mbps shared (hub) –Some users get 100 Mbps dedicated (switch)

59. Token Ring Physical Layout: –Dual Ring of Stars Medium Access Control Protocol –Token Passing

60. Token Ring Advantages over Ethernet: – Disadvantages over Ethernet: –

62. Token Ring Frames

63. Access Control Byte

64. Token Ring Operation