IPv6 Unicast Addressing

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• IPv6 unicast identifies a single network interface
  • addressing is scoped
    • is a region of the network
  • global scopes provide the equivalent of public addressing schemes in IPv4
  • link local schemes provide private addressing

IPv6 Global Addressing

• globally scoped unicast addresses are routable over the Internet
  • equivalent to IPv4 public addresses
• parts of a global address:
  • first 3 bits (001) indicate the address is within global scope
    • most IPv6 address space is unused
    • scope for globally unique unicast occupies just 1/8 of total address space
    • in hex, will start with a 2 (0010 in binary) or 3 (0011)
  • next 45 bits are allocated in a hierarchical manner to regional registries
    • then to ISPs and end users
  • next 16 bits identify site-specific subnet addresses
  • final 64 bits are the interface ID

Interface ID (EUI-64)

• 64-bit interface ID is determined by two techniques:
  • using the interface’s MAC address
    • referred to as MAC-derived address or interface identifier
    • formally called Extended Unique Identifier-64 (EUI-64)
    • MAC address is 48 bits
      • translation mechanism allows driver software to create a 64-bit interface ID from these 48 bits
      • two changes occur to derive EUI-64:
        • digits fffe are added in the middle of the MAC address
        • first 8 bits, or 2 hex digits, are converted to binary, and the 7th bit (U/L bit) is flipped
        • E.g., MAC address 00608c123abc becomes EUI-64 02608cfffe123abc
          • in double bytes 0260:8cff:fe12:3abc
          • without leading 0 260:8cff:fe12:3abc
  • privacy extensions
    • client device uses a pseudorandom number for the interface ID
      • called temporary interface ID or token
    • concern that using interface identifiers allow a host to be identified and closely monitored
      • using token mitigates this to some degree