1. 13.1 Wired LANs: Ethernet Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. 2 A Simple Network (LAN) Internet 140.192.40.5 192.168.0.1 192.168.0.10 Crossover UTP cable

3. 3 Typical LAN 1 st floor 2 nd floor 9 th floor Internet Data center

4. 4 Campus Area Network (CAN) CDM Building DePaul Center Lewis Center Administration Building

5. 5 Metropolitan Area Network (MAN) Lincoln Park Loop Rolling Meadow Lake Forest Naperville

6. 6 Wide Area Network (WAN) WAN

7. 7 Success of Ethernet Easy to understand, implement, manage, and maintain Low-cost network implementations Extensive topological flexibility for network installation Interoperability and operation of standards-compliant products, regardless of manufacturer

8. 8 LAN Services Users do not see the network, and they are interested in the services. What are the essential LAN services? Printer sharing File sharing Application sharing Internet Surfing Intranet Web Database Backup Fax Service Telephony Conferencing Management Miscellaneous

9. 9 Network Components Cables Network Interface Cards (NIC) Network hardware Hubs Switches Routers Gateways Printers Storage devices (NAS and SAN) Network Operating System (NOS) Software

10. 10 Network Operating System Network Software programs that control resources shared over the network. Application Protocols Drivers Example: Windows, NetWare, UNIX, Linux, MacOS Application Protocols Drivers Clients Server

11. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 11 History of Ethernet

12. 12 ALOHA Network (’68-’72) Radio frequency w/ speed = 4.8-9.6K bps Outbound channel: one-to-many transmission In-bound: same channel frequency with contention Inventor: Norman Abramson terminal IBM 360 Slotted Aloha followed after Aloha. Throughput jumped from 18% to 37%.

13. 13 First Ethernet at Xerox Inventor: Bob Metcalfe Location: Xerox Palo Alto Research Lab Time: May 22, 1973, The first Local Area Network for personal computer (called ALTO) and printer (called EARS). Speed: 2.94Mbps Importance: carrier sense (listen first before transmitting)

14. 14 Standardization of Ethernet Intel – Chip technology DEC – System engineering and hardware supplier Xerox – Ethernet technology 1980 - The Ethernet blue book (DIX) Speed – 10Mbps 1981 – IEEE 802.3 subcommittee 1983 – IEEE 10Base5 1989 – ISO 88023

15. 13.15 Figure 13.1 IEEE standard for LANs

16. 13.16 Figure 13.2 HDLC frame compared with LLC and MAC frames

17. 13.17 Figure 13.3 Ethernet evolution through four generations

18. 13.18 Figure 13.4 802.3 MAC frame

19. 13.19 Figure 13.5 Minimum and maximum lengths

20. 13.20 Frame length: Minimum: 64 bytes (512 bits) Maximum: 1518 bytes (12,144 bits) Note

21. 13.21 Figure 13.6 Example of an Ethernet address in hexadecimal notation

22. 13.22 Figure 13.7 Unicast and multicast addresses

23. 13.23 The least significant bit of the first byte defines the type of address. If the bit is 0, the address is unicast; otherwise, it is multicast. Note

24. 13.24 The broadcast destination address is a special case of the multicast address in which all bits are 1s. Note

25. 13.25 Define the type of the following destination addresses: a. 4A:30:10:21:10:1A b. 47:20:1B:2E:08:EE c. FF:FF:FF:FF:FF:FF Solution To find the type of the address, we need to look at the second hexadecimal digit from the left. If it is even, the address is unicast. If it is odd, the address is multicast. If all digits are F’s, the address is broadcast. Therefore, we have the following: a. This is a unicast address because A in binary is 1010. b. This is a multicast address because 7 in binary is 0111. c. This is a broadcast address because all digits are F’s. Example 13.1

26. 13.26 Show how the address 47:20:1B:2E:08:EE is sent out on line. Solution The address is sent left-to-right, byte by byte; for each byte, it is sent right-to-left, bit by bit, as shown below: Example 13.2

27. 13.27 Figure 13.8 Categories of Standard Ethernet

28. 13.28 Figure 13.9 Encoding in a Standard Ethernet implementation

29. 13.29 Figure 13.10 10Base5 implementation

30. 13.30 Figure 13.11 10Base2 implementation

31. 31 StarLAN (1BaseT) Problem with 10Base5 and 10Base2: poor cabling plant What is the problem? Need: a cabling plant like telephone system 1983: AT&T and NCR, running Ethernet on UTP Speed: 1M bps (This is the major issue) Importance: a market failure but a technology milestone We have a structured cabling plant now

32. 32 StarLAN Ethernet hub or repeater Network topology: now a star topology A structured cabling plant similar to telephone network. Q: Why is star topology better than bus topology?

33. 13.33 Figure 13.12 10Base-T implementation

34. Ethernet Encoding Schemes Manchester (10BaseT) 0-bit = + voltage, - voltage 1-bit = - voltage, + voltage

35. 13.35 Figure 13.13 10Base-F implementation

36. NRZ-I Encoding (100Base-FX) 0: no change 1: inverse

37. Medium idle? Transmit. Not ready? Wait until it becomes ready then wait interframe gap (9.6 microseconds) or use p-persistent algorithm Collision detected? Continue transmission until min packet time reached (jam signal) Increment retransmission counter 13.37 CSMA/CD Basic Algorithm

38. 38 CSMA/CD Procedure Station is ready to send Sense Channel Transmit data and sense channel Wait (backoff strategy) Send jam signal collision detected channel busy try again successful transmission

39. 39 802.3 Parameters (Table 3.2) Slot time 512 bit times (51.2  s) InterFrameGap 96 bit times (9.6  s) AttemptLimit16 (tries) BackoffLimit10 (exponent) JamSize32 bits MaxFrameSize1518 bytes MinFrameSize64 bytes AddressSize48 bits (6 bytes)

40. 40 Ethernet Performance Why do large frames have better performance?

41. Collisions are the killer!! Network throughput typically 20-30%, 40% was max! Need a way to eliminate collisions What about token ring and token bus? What about bridges and switches? 13.41 CSMA/CD Basic Algorithm

42. How long does it take to hear a collision? Signals travel at 2/3 speed of light thru copper Propagation time = distance / velocity How many bits can you transmit during that time? Data transfer time = length of frame (bits) / data rate (bps) 13.42 CSMA/CD Collisions

43. 13.43 Table 13.1 Summary of Standard Ethernet implementations

44. 13.44 13-3 CHANGES IN THE STANDARD The 10-Mbps Standard Ethernet has gone through several changes before moving to the higher data rates. These changes actually opened the road to the evolution of the Ethernet to become compatible with other high-data-rate LANs. Bridged Ethernet Switched Ethernet Full-Duplex Ethernet Topics discussed in this section:

45. 13.45 Figure 13.14 Sharing bandwidth

46. 13.46 Figure 13.15 A network with and without a bridge

47. 13.47 Figure 13.16 Collision domains in an unbridged network and a bridged network

48. 13.48 Figure 13.17 Switched Ethernet

49. How Switches Learn Host Addresses and Locations Initial MAC forwarding table is empty MAC forwarding table 0260.8c01.1111 0260.8c01.2222 0260.8c01.3333 0260.8c01.4444 E0E1 E2E3 AB CD

50. How Switches Learn Host Addresses and Locations MAC forwarding table 0260.8c01.1111 0260.8c01.2222 0260.8c01.3333 0260.8c01.4444 E0E1 E2E3 AB CD Station A sends a frame to Station C Switch caches station A MAC address to port E0 by learning the source address of data frames The frame from station A to station C is flooded out to all ports except port E0 (unknown unicasts are flooded) E0: 0260.8c01.1111

51. MAC forwarding table 0260.8c01.1111 0260.8c01.2222 0260.8c01.3333 0260.8c01.4444 E0E1 E2E3 AB CD Station A sends a frame to station C Destination is known, frame is not flooded How Switches Filter Frames E0: 0260.8c01.1111 E2: 0260.8c01.2222 E1: 0260.8c01.3333 E3: 0260.8c01.4444

52. Broadcast Frames Station D sends a broadcast frame Broadcast frames are flooded to all ports other than the originating port 0260.8c01.1111 0260.8c01.2222 0260.8c01.3333 0260.8c01.4444 E0E1 E2E3 DC AB E0: 0260.8c01.1111 E2: 0260.8c01.2222 E1: 0260.8c01.3333 E3: 0260.8c01.4444

53. MAC Forwarding Table Unlike IP address, MAC address is local. MAC forwarding table is also local, within the single broadcast domain (which is an IP subnet). MAC address learning stops at the router, and a switch does not learn the MAC addresses at the other side of the router. The switch learns one MAC address of the router.

54. 13.54 Figure 13.18 Full-duplex switched Ethernet

55. 55 5-4-3 Rule (10BaseX) 5 segments, 4 repeaters, 3 populated segments hub/repeater

56. 13.56 13-4 FAST ETHERNET Fast Ethernet was designed to compete with LAN protocols such as FDDI or Fiber Channel. IEEE created Fast Ethernet under the name 802.3u. Fast Ethernet is backward-compatible with Standard Ethernet, but it can transmit data 10 times faster at a rate of 100 Mbps. MAC Sublayer Physical Layer Topics discussed in this section:

57. 13.57 Figure 13.19 Fast Ethernet topology

58. 13.58 Figure 13.20 Fast Ethernet implementations

59. 13.59 Figure 13.21 Encoding for Fast Ethernet implementation

60. MLT-3 Signal (100Base-TX) three levels: +1, 0, -1 transition (at 1’s only): +1 => 0 = -1 => 0 => +1

61. 13.61 Table 13.2 Summary of Fast Ethernet implementations

62. 13.62 13-5 GIGABIT ETHERNET The need for an even higher data rate resulted in the design of the Gigabit Ethernet protocol (1000 Mbps). The IEEE committee calls the standard 802.3z. MAC Sublayer Physical Layer Ten-Gigabit Ethernet Topics discussed in this section:

63. 13.63 In the full-duplex mode of Gigabit Ethernet, there is no collision; the maximum length of the cable is determined by the signal attenuation in the cable. Note

64. 13.64 Figure 13.22 Topologies of Gigabit Ethernet

65. 13.65 Figure 13.23 Gigabit Ethernet implementations

66. 13.66 Figure 13.24 Encoding in Gigabit Ethernet implementations

67. 13.67 Table 13.3 Summary of Gigabit Ethernet implementations

68. 1G to 10G (802.3ae)

69. 10GbE Full-duplex only (no CSMA/CD) Fiber only (802.3ae) WAN (SONET-friendly) PHY Mapping to OC-192 carrier Rate adaptation to SONET payload capacity New line coding (64b/66b) Standard for copper 10GBase-CX (802.3ak) - 2004 dual coax cable <20m (for data center use only) Standard for copper 10GBase-T (802.3an) - 2006 UTP cable (~50m for Cat-6 and ~100m for Cat-6a)

70. IEEE P802.3ba 100G physical layer specifications for operation up to: 40 km on single-mode fiber (SMF) using wavelength division multiplexing (WDM) 10 km on SMF using WDM 100 m on parallel OM3 multimode fiber (MMF) 10 m over a copper cable assembly 40G physical layer specifications for operation up to: 10 km on SMF using WDM 100 m on parallel OM3 MMF 10 m over a copper cable assembly 70

71. 71 Other High Speed LAN Technologies Token Ring Fiber Distributed Data Interface (FDDI) 100VG-AnyLAN ATM LAN

72. 72 Continuous Improvement 10M => 100M (802.3u) => 1G (802.3z and 802.3ab) 10G (802.3ae, 802.3ak, 802.3an) Now 40 G and 100G (approved in 2010) Virtual LAN (802.1Q) Quality of Service (802.1p) Fault tolerance Spanning Tree Algorithm and Protocol 802.1D Rapid STP 802.1w and per VLAN STP 802.1s Link aggregation 802.1ad Port based network access control: 802.1X Wireless LAN: 802.11

73. 13.73 Power Over Ethernet (PoE) Power over Ethernet (PoE) PoE delivers low-voltage power over Cat 5 cable. Ideal for applications such as wireless access points, access-card readers, IP telephones, IP video cameras, and may even be useful with cell phones, PDAs, and laptops. Once a proprietary technology, now it is an IEEE standard 802.3af. For small scale systems, installing PoE may be as simple as installing a new line card in a switch or hub.

74. 13.74 Power Over Ethernet (PoE) Power over Ethernet (PoE) Installing PoE in a large network may create physical power infrastructure problems. For example, each powered device (PD) can draw up to 15 watts from the switch/hub (power sourcing equipment, or PSE). If you have a 100-port hub, that’s 1500 watts to support the PDs, plus another 1000 watts normally needed to drive the switch. The total is 2500 watts, or roughly 25 amps. Does your wiring closet have a 25 amp circuit? What if the switch has 300 ports? PoE can deliver this 48 volt 15 watt power over the unused spare pair of wires in an Ethernet connection, or over the transmit/receive pairs.