802.5 Token-Ring Networks Topology - PowerPoint by odq14517

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									802.5 Token-Ring Networks: Topology
• An alternative to Ethernet 802.3 LANs
• Physical Layer Topology: Ring
  – Stations connected in a loop
  – Signals go in only one direction, station-to-
    station
  – Not bus physical layer topology like Ethernet
    802.3
   802.5 TRN Physical Layer:
           Topology
• Physically, stations connect to access units
  which are connected in a ring
                Access Unit                     Access Unit


                Access Unit                     Access Unit


                          STP link                UTP Link
                       from Station             from Station
                         to Access                to Access
                            Unit                     Unit
     Stations
                                      Station
802.5 TRN Physical Layer: Wiring
• Most connections use shielded twisted pair
  (STP), which has each pair and the whole cable
  covered with a metal shield to reduce interference

                Access Unit   STP link between   Access Unit
                                Access Units

                Access Unit                      Access Unit


                          STP link                 UTP Link
                       from Station              from Station
                         to Access                 to Access
                            Unit                      Unit
     Stations
                                      Station
   802.5 TRN: Physical Speed
• 802.5 Speeds
  – Initially, 4 Mbps
  – Now, mostly 16 Mbps
  – 100 Mbps is standardized but not widely used
 802.5 TRN MAC Layer: Token
           Passing
• Media Access Control
  –Not CSMA/CD
  –Token passing
  –Special frame called a token circulates
  –Station can only transmit if it has the token
      Transmits
 Token
        Token-Ring Networks
• 802.5 Token-Ring versus 802.3 CSMA/CD-Bus
  – Token-Ring is more reliable
  – Token-Ring is more efficient
  – Token-Ring is more expensive
  – Token-Ring has a small market share
  – Companies buy something good enough to meet
    requirements, and 802.3 standards do this
        802.3 Ethernet versus
      802.5 Token-Ring Network
• Both use 802.2 Standard at the LLC Layer
• MAC Layer: CSMA/CD versus token-
  passing
• PHY Layer Topology: Bus versus Ring
                        802.3           802.5
              LLC               802.2
MAC Access Control   CSMA/CD       Token Passing
     PHY Topology       Bus             Ring

								
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