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Prof. Choong Seon HONG

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Title: Error Detection and Correction Last modified by: Created Date: 2/22/1996 2:16:32 PM Document presentation format: A4 Paper (210x297 mm) – PowerPoint PPT presentation

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Title: Prof. Choong Seon HONG


1
Local Area Networks
  • Prof. Choong Seon HONG

2
12? ??? ???(LAN)
  • 12.1 ???? (Project) 802
  • 12.2 ???(Ethernet)
  • 12.3 ?? ??(Token Bus)
  • 12.4 ?? ?(Token Ring)
  • 12.5 FDDI (Fiber Distributed Data Interface)

3
??? ???(??)
  • ??????(LAN)
  • ??? ???? ??(???, ??, ?? ?)? ?? ???? ?? ???? ???
    ???? ??? ?? ???
  • LAN? ??
  • ???(Ethernet)
  • ?? ??(Token Bus)
  • ?? ?(Token Ring)
  • FDDI(Fiber Distributed Data Interface) ANSI and
    ITU-T ???
  • Data Link Control of LAN are based on HDLC

IEEE ???? 802 ???
4
12.1 ???? 802
  • IEEE ??? ????(1985? ??)
  • ???? 802? OSI???? ??

5
???? 802 (Contd)
  • ???? 802

6
???? 802 (Contd)
  • IEEE 802.1
  • LAN? ?????? ?? ?
  • ?? ??????, ??? ? ?? ?? ????? ???? ?? ???? ??
    (architecture) ?? ???? (incompatibility) ? ??
  • LLC(Logical Link Control)
  • IEEE 802.2
  • ???????? ?????? ?? LAN ????? ??
  • Containing the synchronization, flag, flow, and
    error control specifications
  • MAC(Medium Access Control)
  • ????? ??? ?? ?? ???? ?? ?????? ??

7
???? 802 (Contd)
  • ???? ??? ??(PDU Protocol Data Unit)
  • LLC ?? ??? ??
  • HDLC? ??? 4?? ??? ??

8
???? 802(??)
  • ??(Control) ??
  • HDLC? ?? ??? ??

9
12.2 ???(Ethernet)
  • Xerox ??? ??? 802.3 ??
  • Extended by DEC, Intel, and Xerox
  • IEEE 802.3

(PSK)
10
???(??)
  • ACCESS Method CSMA/CD
  • Today the terms Ethernet, CSMA/CD, 802.3 are
    used interchangeably

11
???(??)
  • Collision in CSMA/CD

12
???(??)
  • ????
  • ??? ?????? ? Station (pc, workstation, print ?)
    ? ??? NIC(Network Interface card)? ??
  • 6??? ??? ??? ?? ??

13
???(??)
  • ?? ??
  • ?? ??(Signaling)
  • ?????(Baseband)??? - Manchester digital Encoding
  • ?????(Broadband)??? - differential PSK
  • ????(data rate)
  • 1100Mbps

14
???(??)
  • ??? ??( Frame Format)
  • Not providing any mechanism for acknowledging
    received

15
???(??)
  • ?????
  • Preamble(7???) combined the alert, timing,
    start synchronization
  • SFD(Start frame delimiter) - ??? ??
  • the everything that follows is data.
  • DA(Destination address) - ??? ??
  • SA(Source address) - ??? ??
  • PDU ??/??
  • 802.2 ???(PDU) - 461500 ?????
  • CRC - ?? ?? ??, CRC-32

16
???(??)
  • ??(Implementation)
  • 10BASE5 Thick Ethernet
  • 10BASE2 Thin Ethernet
  • 10BASE-T Twisted-pair Ethernet
  • 1BASE5 Star LAN
  • Fast Ethernet

17
???(??)
  • 10BASE5 Thick Ethernet(???)

18
???(??)
  • 10BASE5 Thick Ethernet
  • RG-8 ??? 802.3 ?? backbone thick ?????
  • ????(transceiver) MAU(medium attachment unit),
    transmitter-receiver
  • AUI(attachment unit interface) ???
    15-wire???(DB-15pin),???? 50m
  • ???? ?(Transceiver Tap) vampire tap

19
???(??)
  • ??? ????

20
???(??)
  • 10BASE5 ???? ??

21
???(??)
  • 10BASE2 Thin Ethernet
  • NIC - thick Ethernet NIC transceiver
  • Thin ????? - RG-58
  • BNC-T - T?? ???(3ports NIC, input, output)

22
???(??)
  • 10BASE2 Thin Ethernet(???)

23
???(??)
  • 10BASE-T Twisted-pair Ethernet
  • The most popular standard defined in the IEEE
    802.3 series
  • Star?
  • UTP(Unshielded twisted pair) ???
  • ???? 10 Mbps
  • ???? 100M(hub to station)
  • Intelligent hub ??
  • Four-pair RJ-45 ???

24
???(??)
  • 10BASE-T Twisted-pair Ethernet(star?)

25
???(??)
  • 1BASE5 Star LAN
  • ATT??
  • ?? ???? 1 Mbps
  • Twisted-pair ???
  • Hub? ?? 10station

26
???(??)
  • 1BASE5 Star LAN

27
12.3 Other Ethernet Networks
  • An Ethernet network using a hub

28
Other Ethernet Networks (contd)
  • An Ethernet Network Using a Switch

29
Other Ethernet Networks (contd)
  • Fast Ethernet
  • ?? ???? 100Mbps
  • Star?
  • 10base-T? ?? MAC ????? ??? ??
  • 4pair category3, category5 UTP (2 pairs for
    transmission and two pairs for reception)
  • 100BASE-X 2pair high-quality category5
  • 100BASE-FX two optical fiber
  • 100BASE-TX 2pair STP

30
Other Ethernet Networks (contd)
  • Categories of Fast Ethernet Implementations

31
Other Ethernet Networks (contd)
  • 100Base-Tx Implementation

32
Other Ethernet Networks (contd)
  • 100 Base-Fx

The distance between the station and hub (or
switch) should be less than 2000 meters
33
Other Ethernet Networks (contd)
  • 100Base-T4 Implementation
  • Using four pairs of category 3 (voice grade) UTP
  • splitting the 100-Mbps flow of data into three
    33.66-Mbps flows
  • Using 8B/6T
  • Eight bits is transformed into six bauds of
    three voltage levels (positive, negative, and
    zero)

34
Other Ethernet Networks (contd)
  • 100Base-T4 Implementation (contd)

35
Other Ethernet Networks (contd)
  • Gigabit Ethernet
  • 1000 bps 1 Gbps
  • MAC layer and access method remain same, but the
    collision domain is reduced
  • Physical layer transmission media and the
    encoding system is changed
  • Used for backbone to connect Fast Ethernet
    networks

36
Other Ethernet Networks (contd)
  • Use of Gigabit Ethernet

37
Other Ethernet Networks (contd)
  • Comparison between the Gigabit Ethernet
    Implementation

38
12.4 ?? ??(Token Bus)
  • IEEE 820.4
  • ?????? ???
  • Physical Configuration of Ethernet
  • ????? ??? ??? ??(Ring using token)
  • Using the collision-free feature of token ring
  • ?? ???? ???? ??? ??

39
12.5 ?? ?(Token Ring)
  • IEEE 802.5
  • token passing ?? access method
  • Using three-byte token
  • token possession
  • Token ring allows each station to send one frame
    per turn.

40
?? ?(??)
41
?? ?(??)
  • ?? ?
  • ????(Priority)? ??(Reservation)
  • use of access control (AC) field
  • ????(Time Limit) 10ms
  • each station expects to receive frames within
    regular time intervals
  • ??(monitor) station
  • Monitoring, regenerating a new token
  • ??
  • 6 ??? ?? (imprinted on the NIC card)

42
?? ?(??)
  • ?? ??
  • differential Manchester ???????
  • ???? 4-16Mbps
  • ?????
  • ???(data)
  • ??(token)
  • ??(abort)

43
?? ?(??)
  • ?? ? ???

44
?? ?(??)
  • ??? ??? ???

For Differential Manchester
Error Detected Bit
Control information or Data
How to use the information in the AC field
45
?? ?(??)
  • ?? ? ???
  • SD (Start delimiter) ?? ??? ??
  • used to alert the receiving station to the
    arrival of a frame
  • equivalent to the flag field in HDLC
  • adopted J and K violation to ensure
    transparency in the data field
  • AC (Access control) ????
  • Three bits priority field
  • the token bit set to indicate that the frame
    is a data frame rather than a token or an abort
    frame
  • FC (Frame control) ????(??, ???)
  • the first one bit used to indicate the type
    of information contained in the PDU (control
    information or data)
  • 7 bits containing information used by the
    token ring logic (e.g., how to use the
    information in the AC field)

46
?? ?(??)
  • DA(Destination address)
  • SA(Source address)
  • Data4500???
  • CRCCRC-32 ?? ??
  • ED(end delimiter)
  • FS(Frame status) ???? ?? ??
  • set by the receiver to indicate that the frame
    has been read, or by the monitor to indicate that
    the frame has been already been around the ring
  • So, saying that the frame can now be discarded

47
?? ?(??)
  • ?? ???
  • 3?? ??? ?? SD, AC, ED
  • used as a reservation frame to serve access to
    the ring
  • ??(Abort) ???
  • ?? ??
  • Just including SD and ED
  • generated either by the sender to stop its own
    transmission, or by the monitor to purge an old
    transmission from the line

48
?? ?(??)
  • Implementation
  • The ring in the Token Ring consists of a series
    of 150-ohm, STP sections linking each station to
    its immediate neighbors

49
?? ?(??)
  • Token ring Switch

50
?? ?(??)
  • MAU(Multistation Access Unit)

51
12.5 FDDI (Fiber Distributed Data Interface)
  • ANSI? ITU-U(ITU-TX.3) ??
  • ???? ????
  • Copper version of FDDI CDDI
  • ???? 100Mbps
  • FDDI ??

52
FDDI (contd)
  • Access Method Token Passing
  • access is limited by allotted time
  • Each station has three Time Registers to control
    circulation of the token and distribute link
    access opportunities among the nodes equitably.
  • Values are set when the ring is initialized and
    do not vary in the course of operation
  • SA (Synchronous Allocation)
  • The length of time allowed each station for
    sending synchronization data (time sensitive
    data)
  • The time value is different for each station and
    is negotiated during initialization of the ring

53
FDDI (contd)
  • TTRT (Target Token Rotation Time)
  • The average time required for a token to
    circulate around ring
  • AMT (Absolute Maximum Time)
  • A value equal to twice the TTRT
  • If a token takes longer than this time to make
    one rotation of the ring, the ring must be
    reinitialized.
  • Timers
  • Token Rotation Timer (TRT)
  • The actual time taken by the token to complete a
    cycle
  • Token Holding Timer (THT)
  • Begins running as soon as the token is received
  • Showing how much time remains for sending
    asynchronous frames

54
FDDI (contd)
  • Station Procedure
  • When a token arrives, each station follows this
    procedure
  • THT is set the difference between TTRT and TRT
    (THT TTRT TRT)
  • TRT is reset to zero (TRT 0)
  • The station is set to zero (TRT 0)
  • The station sends asynchronous data as long as
    the value of THT is positive.

55
FDDI (Contd)
2
  • FDDI Example

56
FDDI (Contd)
  • Addressing
  • six-byte address similar to Ethernet address
  • Electronic Specification
  • Signaling (physical layer)
  • using a special encoding mechanism called 4B/5B
  • encoding by NRZ-I
  • Data Rate
  • up to 100 Mbps

57
FDDI (Contd)
  • Encoding by NRZ-I

58
FDDI(??)
  • FDDI ????

59
FDDI(??)
  • FDDI ??? ??

60
FDDI(??)
  • FDDI ?(Dual Ring)

61
FDDI(??)
  • FDDI ? ??
  • The secondary ring makes FDDI self-healing.

62
FDDI(??)
  • Nodes
  • ?? ???(DAS dual attachment station)
  • 2?? ?? ????? ???(MIC media interface
    connector)? ???? 2?? ?? ??
  • ?? ???(SAS single attachment station)
  • ??? MIC? ??? ??? ?? ??
  • ?? ????, ??, ?? ??? ?? MIC? ??? ??
  • ?? ?? ???(DAC dual attachment concentrator)
  • ?? ?? SAS ??
  • ?? ?? ??

63
FDDI(??)
  • Node connections

64
12.6 LAN ??
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