Ethernet

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Crossover Pins: 1+3 & 2+6
Auto Negotiate Speed: Fast Link Pulses (FLP)

Framing

• Options

  • DIX / 802.3(1997)
    • Preamble(8), Destination(6), Source(6), Type/Length(2), Data, FCS(4)
  • 802.3 - Media Access Control
    • Preamble(7), SD(1), Destination(6), Source(6), Length(2), FCS(4)
  • 802.2 - Logical Link Control
    • DSAP(1), SSAP(1), Control(1-2)
  • Sub Network Access Control (SNAP)
    • OUI(3), Type(2)

• Fields

  • Preamble - synchronization; proper clocking; alternating 1s and 0s; ends with pair of 1s
  • Control - generally 0x03
  • OUI - generally unused; manufacturer identifier of NIC
  • Type(snap) - overcomes deficiencies with size of DSAP
  • Destination Service Access Point -
  • Source Service Access Point - describes upper layer protocol

Addressing

• Bytes

  • 1st: most significant byte
  • 1st - 3rd: oui
  • 4th - 6th: vendor assigned
  • 6th: least significant byte

• Bits (reverse significant bit order called canonical/little-endian)

  • 1st: least significant bit
  • 8th: most significant bit
  • 7th: u/l; 0 means vendor assigned; 1 means multicast/broadcast
  • 8th: i/g; 0 means unicast; 1 means multicast

Standards

• 10base5 - thicknet; coaxial; 500m
• 10base2 - thinnet; coaxial; 185m
• 10baseT - twisted pair; 100m
• 100baseFX - multimode; 400m
• 100baseT - 2 pair; 100m
• 100baseT4 - 4 pair; 100m
• 100baseTX - 2 pair; 100m
• 1000baseLX - laser; mm & sm; 10km(sm); 3km(mm); long
• 1000baseSX - laser; mm; 220-250m; short
• 1000baseZX - extended wavelength; sm; 100km
• 1000baseCS - stp; 2 pair; 25km
• 1000baseT - utp; 4 pair; 100m
• 802.2 - logical link control
• 802.3 - media access control
• 802.3u - fastethernet (100Mbps); copper & optical
• 802.3z - gig over optical
• 802.3ab - gig over copper