Ethernet

From dankwiki
Jump to navigation Jump to search

10GigE

10GBASE-T

  • Reuses the existing 1000BASE-T MAC
  • Full duplex only
  • 4 connector, 4 twisted pairs (lanes) copper cabling
  • 10-level PAM code (3 bits/symbol)
  • Retains 8-state 4D trellis code across pairs
  • 833 Mbaud, ~450MHz bandwidth
  • Echo-cancelled transmission, FEXT cancellation
    • 10Gbps = 4 lanes * 833 Mbaud * 3 bits/baud

10GBASE-CX4

  • Short distance copper twin-ax

GigE

  • 5-level PAM code (2 bits/symbol)
  • 125 Mbaud, ~80MHz bandwidth

Fast Ethernet

Addresses

An address is unicast if the least significant bit of the first byte is 0. Otherwise, it is either broadcast:

  • FF:FF:FF:FF:FF:FF: segment broadcast

or multicast:

Local Network Control Block (224.0.0/24)

  • 01:00:5e:00:00:01 (224.0.0.1): All-Hosts
  • 01:00:5e:00:00:02 (224.0.0.2): All-Routers
  • (224.0.0.22): IGMP
  • (224.0.0.251, ff02::fb): mDNS
  • 33:33:00:01:00:02 (ff02::1:2): DHCPv6 server/relay

Locally-assigned Addresses

If the penultimately-significant bit is 1, the address is "locally assigned" (read: made up). This is used by the Linux kernel's rand_hw_addr() function, used by PPP and TAP.

See Also