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									        Lecture #15: High speed
                           LANs
Contents


    Fast LANs   2

    FDDI    3

    Fast Ethernet   7

    HIPPI   8




                              1
                                              Fast LANs
Advances in transmission speed and distance.
Technology
     FDDI
     Fast Ethernet
Application
     inter-LAN backbones
     when 100 Mb/S and upper bandwidth is needed
      ETHERNET        ATM                  ATM
                       ...                  ...

                                                  ETHERNET

                    Inter LAN backbone
                       e.g. FDDI Ring
         TOKEN
         RING
                                                   TOKEN
                   FDDI           FDDI             RING
      FIBER                                                  B   Bridge
      CHANNEL                            FIBER                            2
                                         CHANNEL
                                                         FDDI
   FDDI (Fiber Distributed Data Interface)
     – token ring topology (because of the media)
     – standard bandwidth 100 Mb/S
     – ring length up to 200 km
     – application
               • inter LAN backbones
               • PCM trunks and ISDN traffic (FDDI-II)
   FDDI physical implementation
     – multimode fibers (thicker, based on the internal
       reflection, slower but cheaper than thin single-mode
       fibers)
     – LED as light sources
     – BER under 10-10 (Bit Error Rate).
                                                              3
                                                        FDDI
   Topology:
        – doubled ring for full duplex transmission or
        – single ring with token circulation
   FDDI Station classes - A/B
   4-out-of-5 bit coding


           {                               }
   -           4-bit data sequence (16)
                frame delimiters (3)
    each        control sequences (2)          is coded with 5 bits
                hardware signals (3) –
    75% more congested coding than Manchester code but
    not self-clocked  synchronization by leading
    preamble for each frame.                         4
                          FDDI Token Ring and
                                       Frame
   Much longer circumnavigate distances than in 802.5
    allow multiple frame circulation in the ring
   One-token-multiple-frames scheme (asynchronous
    “bursty” traffic)
                                               15/1
   General Frame format
     –   preamble                     15/2
     –   Start/End Delimiters (SD/ED)
     –   Frame Control byte (FC) /Data/control frame/
     –   Destination and Source Addresses - 2 or 6 bytes (DA, SA)
     –   unlimited Info
     –   FCS - CRC error control
     –   Frame Status byte (FS)
   Token Frame format
     – preamble
     – Frame Control byte (FC)
     – Frame Status byte (FS)                                       5
                   FDDI Token Ring Timing and
                     Synchronous Transmission
   FDDI token ring timing:
     – Token holding timer - station time limit for token holding
     – Token rotation timer - starting the token recovery procedure after
       the time-out
     – Valid transmission timer - detecting transient ring problems after
       the time-out
   Synchronous transmission over FDDI (“stream traffic”):
     – synchronous frame
        • header field (16B) for non-circuit-switching data
        • data field (up to 96B) - 4 T1 (4x24) PCM channels of
          1.544Mb/S or 3 E1 (3x32) CCITT channels of 2.048 Mb/S.
     – timing - up to 16 sync. frames per 125mS period i.e. up
       to 8000*16 sync. frames/S (synchronous transmission
       bandwidth 8000*16*96B*8b=98.304 b/S)
                                                              6
                              Fast ETHERNET
   Faster Ethernet MAC protocol over 10 times
    shorter transmission cable
   ETH cable segments are connected by hubs
   Cabling      4/47
     – cat. 3 twisted pair - 4 twisted pairs: to/from hub + 2
       pairs switchable to the active station
     – cat. 5 twisted pair - 2 twisted pairs: to/from hub
     – fiber - in and out multimode fiber up to 2 km
   Twisted pair hubs
     – shared hub
     – switched (buffered) hub
                                                            7
                                        HIPPI Standard
   HIPPI (High Performance Parallel Interface)
     – Point-to-Point parallel computer interface with Primary/Secondary
       logical connectivity
     – crossbar switch extension        4/48
     – cabling: 50 twisted pair lines in parallel splitting 32b/18b
       (data/interface control incl. 1 parity bit) simplex mode; two lines
       in parallel for full duplex mode; maximum line length 25m.
     – Frame format: 256 words (32b) with parity bit per each word and
       and a parity word at the end of each frame (no CRC):
                           pb bFF bFE         b1 b0
                           p31 31 31          31 31
                           p30 30 30          30 30
                            . . .
                            . . .              . .
                                               . .
                            . . .       ...    . .
                           p1   1   1          1   1
                           p0   0   0          0   0                         8
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