DATA-LINK LAYER PROTOCOLS by jianghongl

VIEWS: 13 PAGES: 39

									                                  1




Chapter 4

DATA-LINK LAYER
PROTOCOLS
            Ethernet
            Token Ring
            FDDI
            Wireless Networking
                         Chapter 4: DATA-LINK LAYER PROTOCOLS                2




OSI MODEL AND IEEE 802.X STANDARDS

 The Institute of Electrical and Electronics Engineers (IEEE)
  divides the data-link and physical layers of the Open
  Systems Interconnection (OSI) model into four sublayers:
    Two IEEE data-link sublayers:
        The upper sublayer is the 802.2 or Logical Link Control (LLC)
            Operates independently from the Media Access Control (MAC)
             sublayer
            Specifies the upper layer protocol carried within a frame
        The lower sublayer is the MAC sublayer.
            Defined by various 802.x standards such as IEEE 802.3, 802.5, and
             802.11
                   Chapter 4: DATA-LINK LAYER PROTOCOLS   3




OSI MODEL AND IEEE 802.X STANDARDS
(CONT.)
   Two IEEE physical sublayers:
      Physical signaling
      Media specifications
            Chapter 4: DATA-LINK LAYER PROTOCOLS   4




FOUR IEEE SUBLAYERS
            Chapter 4: DATA-LINK LAYER PROTOCOLS   5




IEEE DATA-LINK AND PHYSICAL STANDARDS
                   Chapter 4: DATA-LINK LAYER PROTOCOLS      6




ETHERNET VERSION I AND II

 Digital Equipment Corporation, Intel, and Xerox
  published the first two 10-Mbps Ethernet standards.
   Version I (also known as DIX Ethernet)
      Uses bus topology with RG-8 (thick coaxial cable)
      Uses Attachment Unit Interface (AUI) patch cables with
       15-pin connectors, 50-ohm terminators, and external
       transceivers
      Maximum distance per segment: 500 meters
      Maximum distance per network: 2500 meters
      Uses the 5-4-3 rule
      Adopted and renamed 10Base5 (page 157) by the IEEE
                      Chapter 4: DATA-LINK LAYER PROTOCOLS   7




ETHERNET VERSION I AND II (CONT.)

   Version II
      Uses bus topology with RG-58 (thin coaxial cable)
      Uses T-connectors, 50-ohm terminators, and internal
       transceivers
      Maximum distance per segment: 185 meters
      Maximum distance per network: 925 meters
      Uses the 5-4-3 rule
      Adopted and renamed 10Base2 by the IEEE
             Chapter 4: DATA-LINK LAYER PROTOCOLS   8




5-4-3 RULE
                   Chapter 4: DATA-LINK LAYER PROTOCOLS   9




IEEE ETHERNET STANDARDS (page 159)

 The IEEE adopted and renamed the original
  Ethernet standards and then expanded them.
 All IEEE Ethernet standards are controlled by the
  802.3 working group.
    10-Mbps standards: 802.3a (10Base2), 802.3e
    (10Base5), 802.3i (10Base-T), and 802.3j (10Base-
    FP, 10Base-FB, and 10Base-FL)
    100-Mbps standards: 802.3u (100Base-X)
    1000-Mbps standards: 802.3z and 802.3ab
    (1000Base-X)
                    Chapter 4: DATA-LINK LAYER PROTOCOLS    10




IEEE 10BASE-X STANDARDS

 The three primary IEEE standards for 10-Mbps
  baseband networks are
   10Base5
      Physical and data-link layer standards and limitations
       are identical to Ethernet version I.
   10Base2
      Physical and data-link layer standards and limitations
       are identical to Ethernet version II.
                  Chapter 4: DATA-LINK LAYER PROTOCOLS    11




IEEE 10BASE-X STANDARDS (CONT.)

 10Base-T
   Star topology using unshielded twisted-pair (UTP)
    cabling
   Two-pair UTP with RJ-45 connectors: One pair for
    transmit, the other one for receive
      Supports half-duplex and full-duplex modes
      Maximum distance per segment: 100 meters
      Maximum distance per network: 500 meters (which
       includes connections from workstation to hub and also
       connections between hubs)
      Uses the 5-4-3 rule
              Chapter 4: DATA-LINK LAYER PROTOCOLS   12




10BASE-T 5-4 Rule
                    Chapter 4: DATA-LINK LAYER PROTOCOLS    13




IEEE 100BASE-X STANDARDS

 The three IEEE standards for 100-Mbps baseband
  networks configured as a star topology are
   100Base-TX
      Uses the 4B5B encoding scheme over two pair
         (Category 5), the same as 10Base-T
        Supports half-duplex mode or full-duplex mode
        Maximum distance per segment (half or full): 100
         meters
        Maximum distance per half-duplex network: 205
         meters
        Supports Class I and Class II repeaters
                  Chapter 4: DATA-LINK LAYER PROTOCOLS   14




IEEE 100BASE-X STANDARDS (CONT.)

   100Base-T4
     Uses the 8B/6B encoding scheme over four Category 3
      (CAT3) twisted pairs
     Supports only half-duplex mode
     Maximum distance per segment: 100 meters
     Maximum distance per network: 205 meters
     Supports Class I and Class II repeaters
                  Chapter 4: DATA-LINK LAYER PROTOCOLS             15




IEEE 100BASE-X STANDARDS (CONT.)

   100Base-FX
     Uses the 4B/5B encoding scheme over fiber optic
     Supports half-duplex mode or full-duplex mode
        Maximum length of a multimode half-duplex segment: 412
         meters
        Maximum length of a multimode full-duplex segment: 2
         kilometers
        Maximum length of a singlemode half-duplex segment: 2
         kilometers
        Maximum length of a singlemode full-duplex segment: 10+
         kilometers
     Supports Class I and Class II repeaters
             Chapter 4: DATA-LINK LAYER PROTOCOLS   16




CLASS I AND CLASS II REPEATERS
                  Chapter 4: DATA-LINK LAYER PROTOCOLS   17




IEEE 1000BASE-X STANDARDS

 The IEEE 1000Base-X standard defines Gigabit
  Ethernet specifications for twisted-pair cable and
  fiber optic cable.
   Uses the 8B/10T encoding scheme
   Supports full-duplex mode only
   Maximum length of UTP segment: 100 meters
   Maximum length of multimode fiber segment: 220+
    meters
   Maximum length of singlemode fiber segment: 5000
    meters
                  Chapter 4: DATA-LINK LAYER PROTOCOLS   18




FOUR ETHERNET FRAME TYPES

 There are four different Ethernet frame types:
    Version II
    Ethernet 802.3
    IEEE 802.3
    IEEE 802.3 SNAP
             Chapter 4: DATA-LINK LAYER PROTOCOLS   19




VERSION II FRAME
            Chapter 4: DATA-LINK LAYER PROTOCOLS   20




ETHERNET 802.3 FRAME
             Chapter 4: DATA-LINK LAYER PROTOCOLS   21




IEEE 802.3 FRAME
             Chapter 4: DATA-LINK LAYER PROTOCOLS   22




IEEE 802.3 SNAP FRAME
                 Chapter 4: DATA-LINK LAYER PROTOCOLS   23




MAC ADDRESSES (page 162)




Media Access Control: Is the mechanism that
enables multiple computers to use the same
network medium without conflicting
                      Chapter 4: DATA-LINK LAYER PROTOCOLS       24




CARRIER SENSE MULTIPLE ACCESS WITH
COLLISION DETECTION (CSMA/CD)
Phase                  Description

Carrier sense          A computer listens to the network before
                       transmitting.

Multiple access        When the network is clear, the computer
                       transmits the packet.

Collision detection    The computer checks for signs of a
                       collision. If one occurs, it retransmits the
                       packet.
                    Chapter 4: DATA-LINK LAYER PROTOCOLS      25




CARRIER SENSE MULTIPLE ACCESS WITH
COLLISION DETECTION (CSMA/CD)
 All half-duplex implementations of Ethernet use the
  CSMA/CD channel access method.
   Carrier Sense
      A device that wants to transmit must first listen to the
       channel to see if it is in use.
      If the channel is busy, the device must wait.
      If the channel is idle, the device can transmit a frame.
                    Chapter 4: DATA-LINK LAYER PROTOCOLS          26




CARRIER SENSE MULTIPLE ACCESS WITH
COLLISION DETECTION (CSMA/CD) (CONT.)
   Multiple Access                                        CSMA
      All devices on the network contend for access to the
       channel.
   Collision Detection
      When two or more devices transmit at the same time,
       their signals collide.
      Devices detect collisions when they receive a different
       frequency on their receive pair.
      Devices must immediately stop transmitting data and
       send out a jamming signal and then back off for a
       random interval before trying again.
                   Chapter 4: DATA-LINK LAYER PROTOCOLS                27



                              Collision                   Contention
COLLISIONS
 Collisions are also called signal quality errors.
 They are normal on Ethernet networks.
 The frequency of collisions increases as network
  traffic increases.
 Late collisions are a sign of a serious problem.




              Do Exercise 4-2 (Page 194)
                       Chapter 4: DATA-LINK LAYER PROTOCOLS                  28



                                                        Token Ring Network
TOKEN RING

 Token Ring was originally developed by IBM, and then it was
  adopted by the IEEE and renamed 802.5.
    Star wired ring topology
    Operates at either 4 Mbps or 16 Mbps
    Token-passing channel access method (Next Slide)
    Uses Multistation Access Units (MAUs) to connect nodes to the
     network
       You can connect MAUs together, using RI (Ring In) and RO (Out)
        ports to form a larger ring.
    Can use both shielded and unshielded twisted-pair cable
                  Chapter 4: DATA-LINK LAYER PROTOCOLS                   29



                                                         Token Passing
TOKEN Passing

 A token frame circulates continuously around the
  network.
 Only the computer holding the token can transmit
  data.
 The transmitting system is responsible for removing
  the data from the ring.
            Chapter 4: DATA-LINK LAYER PROTOCOLS   30




TOKEN RING FRAMES
                      Chapter 4: DATA-LINK LAYER PROTOCOLS    31




FDDI (Fiber Distributed Data Interface )

 Developed by the American National Standards Institute
  (ANSI)
 Uses dual ring topology
    The primary ring serves as a data path.
    The secondary ring provides fault tolerance.
 Has a 100-Mbps transmission rate over fiber optic cabling
 Uses the token passing channel access method
 Supports early token release
 Uses single attachment station (SAS) or dual attachment
  station (DAS) FDDI
                Chapter 4: DATA-LINK LAYER PROTOCOLS   32




FDDI (Fiber Distributed Data Interface )

 Supports both:
   Singlemode cable (600 Km segments)
   Multimode cable (100 Km segments &
    500 Workstations) This is the industry
    standard for fiber optic LANs.
            Chapter 4: DATA-LINK LAYER PROTOCOLS   33




SAS AND DAS DEVICES
             Chapter 4: DATA-LINK LAYER PROTOCOLS   35




RING WRAP (page 185)
              Chapter 4: DATA-LINK LAYER PROTOCOLS   36




FDDI FRAMES
                      Chapter 4: DATA-LINK LAYER PROTOCOLS              37



                                                        Wireless LANs
WIRELESS LANS

 IEEE standard 802.11 defines the specifications for wireless
  LANs (WLANs).
    Support various transmission rates, depending on the standard
       802.11b supports up to 11 Mbps.
       802.11a and 802.11g support up to 54 Mbps.
    Support ad hoc or infrastructure topologies
    Use three different signaling methods: Direct Sequence Spread
     Spectrum (DSSS), Frequency Hopping Spread Spectrum (FHSS),
     and infrared
    Use the Carrier Sense Multiple Access with Collision Avoidance
     (CSMA/CA) channel access method
              Chapter 4: DATA-LINK LAYER PROTOCOLS   38




AD HOC WLAN
            Chapter 4: DATA-LINK LAYER PROTOCOLS   39




INFRASTRUCTURE WIRELESS
                  Chapter 4: DATA-LINK LAYER PROTOCOLS   40




SUMMARY

 DIX and IEEE 802.3 define physical and data-link
  layer standards and functions for Ethernet networks
  using CSMA/CD over coaxial, twisted-pair, or fiber
  optic cabling.
 IBM and IEEE 802.5 define physical and data-link
  layer standards and functions for a token passing
  ring topology.
 FDDI defines the physical and data-link layer
  standards for a token-passing, fiber optic ring
  topology.
 WLANs can either be ad hoc or infrastructure.

								
To top