3c ethernet

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3c ethernet

  1. 1. Networking FundamentalsWIRED LANs: ETHERNET
  2. 2. 13.2IEEE STANDARDSIEEE STANDARDS• In 1985In 1985(80)(80), the Computer Society of the IEEE, the Computer Society of the IEEEstarted a project, called Project 802, to setstarted a project, called Project 802, to setstandards to enable intercommunication amongstandards to enable intercommunication amongequipment from a variety of manufacturers.equipment from a variety of manufacturers.• Project 802 is a way of specifying functions of theProject 802 is a way of specifying functions of thephysical layer and the data link layer of major LANphysical layer and the data link layer of major LANprotocolsprotocols (PANs/MANs also)(PANs/MANs also)..
  3. 3. 13.3IEEE standard for LANs
  4. 4. IEEE 802 StandardsThe 802 working groups. The important ones aremarked with *. The ones marked with  arehibernating. The one marked with † gave up.
  5. 5. 13.5HDLC frame compared with LLC and MAC frames
  6. 6. 13.6STANDARD ETHERNETSTANDARD ETHERNET• The original Ethernet was created in 1976 atThe original Ethernet was created in 1976 atXerox’s Palo Alto Research Center (PARC).Xerox’s Palo Alto Research Center (PARC).• Since then, it has gone through four generations.Since then, it has gone through four generations.• We now briefly discuss theWe now briefly discuss the Standard (orStandard (ortraditional) Ethernettraditional) Ethernet..
  7. 7. 13.7Ethernet evolution through four generations
  8. 8. 13.8802.3 MAC framePDU
  9. 9. 13.9Minimum and maximum lengthsReason for Min frame length already see (CSMA/CD). Max for saving onMemory cost and preventing a station from monopolising the channel.
  10. 10. 13.10Example of an Ethernet address in hexadecimal notation
  11. 11. Ethernet (?) network card showing its MAC address
  12. 12. 13.12Unicast and multicast addressesThe broadcast destination address is aspecial case of the multicast address inwhich all 48 bits are 1s.
  13. 13. 13.13Define the type of the following destination addresses:a. 4A:30:10:21:10:1A b. 47:20:1B:2E:08:EEc. FF:FF:FF:FF:FF:FFSolutionTo find the type of the address, we need to look at thesecond hexadecimal digit from the left. If it is even, theaddress is unicast. If it is odd, the address is multicast. Ifall digits are F’s, the address is broadcast. Therefore, wehave 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 1
  14. 14. 13.14Show how the address 47:20:1B:2E:08:EE is sent out online.SolutionAddress in binary is 0100 0111 0010 0000 0001 10110010 1110 0000 1000 1110 1110The address is sent left-to-right, byte by byte; for eachbyte, it is sent right-to-left, bit by bit, ie. The bit whichdefines uni/multicast arrives first as shown below:Example 2
  15. 15. Some Information• Access Method : 1 persistent CSMA/CD• Slot Time : Equal to round trip time plus time to sendjam sequence, defined in bits. Seen it is equal to 512bits. For Standard Ethernet it is 51.2 μs.• Slot Time and Maximum Network Length : Propagationspeed = 2 x 108m/sMax length = Propagation speed x Tp (= Slot Time/2)= 2 x 108m/s x 51.2 x 10-6/2 s= 5120 mIn actuality due to repeater delays and time for jamsequences the practical max is 2500 m.13.15
  16. 16. 13.16Physical Layer implementations : Categories of Standard Ethernet
  17. 17. 13.17Encoding in Standard Ethernet – Manchester (self-synchronous)
  18. 18. 13.1810Base5 implementationTransceiver also responsible for detecting collisions
  19. 19. 13.1910Base2 implementationTransceiver part of NIC, connected via tees. Much cheaper
  20. 20. 13.2010Base-T implementationTwo pair twisted cable for trans/receive, therefore collisionsin hub. Length defined as 100 m due to attenuation.
  21. 21. 13.21
  22. 22. 13.2210Base-F implementation
  23. 23. 13.23Summary of Standard Ethernet implementations
  24. 24. 13.24CHANGES IN THE STANDARDCHANGES IN THE STANDARDThe 10-Mbps Standard Ethernet has gone throughThe 10-Mbps Standard Ethernet has gone throughseveral changes before moving to the higher dataseveral changes before moving to the higher datarates. These changes actually opened the road to therates. These changes actually opened the road to theevolution of the Ethernet to become compatible withevolution of the Ethernet to become compatible withother high-data-rate LANs. Some of the changes :other high-data-rate LANs. Some of the changes :• Bridged EthernetBridged Ethernet• Switched EthernetSwitched Ethernet• Full Duplex EthernetFull Duplex Ethernet
  25. 25. 13.25Sharing bandwidth – Unbridged Network
  26. 26. 13.26A network with and without a bridge – Gain more BW
  27. 27. 13.27Collision domains in an unbridged network and a bridged network - Reduced
  28. 28. 13.28Switched Ethernet – a n-port bridge, even better!
  29. 29. 13.29Full-duplex switched Ethernet – even even better, no collisions so no CSMA/CD
  30. 30. 13.30FAST ETHERNETFAST ETHERNET• Fast Ethernet was designed to compete with LANFast Ethernet was designed to compete with LANprotocols such as FDDI or Fiber Channel.protocols such as FDDI or Fiber Channel.• IEEE created Fast Ethernet under the nameIEEE created Fast Ethernet under the name802.3u.802.3u.• Fast Ethernet is backward-compatible withFast Ethernet is backward-compatible withStandard Ethernet, but it can transmit data 10Standard Ethernet, but it can transmit data 10times faster at a rate of 100 Mbps.times faster at a rate of 100 Mbps.
  31. 31. 13.31Fast Ethernet topologyIf hub used instead of switch - half duplex approach.
  32. 32. 13.32Fast Ethernet implementations
  33. 33. 13.33Encoding for Fast Ethernet implementationManchester baudrate twice the datarate, hence useother line codes.To reduce cost of new cat 5. Have100 x 6/8 = 75 Mbaud available,ie. 25 Mbaud /wire.0 1 0 0 1 1 1 0X – for Block Coding.
  34. 34. 13.34Block coding is normally referred to asmB/nB coding;it replaces each m-bit group with ann-bit group. As No. of contiguous 0s or1s is restricted, aids in synchronization.Note
  35. 35. 13.354B/5B mappingcodes
  36. 36. 13.36Multilinetransition: MLT-3 schemeWaveform periodic with baud rate 1/4ththe data rate.
  37. 37. 4.37In mBnL schemes, a pattern of m dataelements is encoded as a pattern of nsignal elements in which 2m≤ Ln.Note
  38. 38. 4.38Multilevel: 8B6T scheme (28=256 data : 36=478 signal)
  39. 39. 13.39Summary of Fast Ethernet implementations32000 m
  40. 40. 13.40GIGABIT ETHERNETGIGABIT ETHERNET• The need for an even higher data rate resulted in theThe need for an even higher data rate resulted in thedesign of the Gigabit Ethernet protocol (1000design of the Gigabit Ethernet protocol (1000Mbps).Mbps).• The IEEE committee calls the standard 802.3z.The IEEE committee calls the standard 802.3z.
  41. 41. 13.41In the full-duplex mode of GigabitEthernet, there is no collision;the maximum length of the cable isdetermined by the signal attenuationin the cable.Note
  42. 42. 13.42Topologies of Gigabit Ethernet
  43. 43. 13.43Gigabit Ethernet implementations
  44. 44. 13.44Encoding in Gigabit Ethernet implementations
  45. 45. 4.45Multilevel: 4D-PAM5 scheme4D - 4 wires: Data rate to 1/4; 8 bits, 4 levels: Signal rate 1/2; thus net 1/8
  46. 46. 13.46Summary of Gigabit Ethernet implementations
  47. 47. 13.47
  48. 48. 13.48Summary of Ten-Gigabit Ethernet implementationsPhysical layer coding has not been specified by the official standards body.

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