Intro to IPv6 Addresses
IPv6 Header
3 2 b its
v e rs io n
(4 b its )
T ra ffic C la s s
(8 b its )
F lo w L a b e l
(2 4 b its )
P a y lo a d L e n g th (1 6 b its )
N ext Header
(8 b its )
H o p L im its (8 b its )
S o u rc e IP a d d re s s (1 2 8 b its )
D e s tin a tio n IP a d d re s s (1 2 8 b its )
• IPv6 addresses have a length of 16 bytes (128 bits)
How many addresses?
• IPv4 Addresses:
– 232 = 4,294,967,296 ≈ 4 billion
• IPv6 Addresses:
– 2128 = 340,282,366,920,938,463,463,374,607,431,768,211,456 ≈ 3.4 x 1038
• Surface area of Earth: 510,072,000 km2
• Size of Atom: 10-10 m = 0.1 nm = 1 Angstrom (Å)
• “Area of Atom”: 1 square angstrom (Ų)= 10-20 m2
Number of atoms on
Earth’s surface: 510,072,000 km2 / 10-20 m2 = 5.1 x 1031
 Number of IPv6 addresses for each
atom on the surface of the Earth:
~ 6.7 million
Convention for writing IPv6 addresses
• IPv6 addresses are written as hexadecimals
– Network prefix is written using CIDR notation
• “Blocks” of 16 bits are separated by colons.
FE80:0000:0000:0000:002A:0000:FE04:0A81
Abbreviation Rules:
1. Leading zeroes in a block can be omitted
FE80:0000:0000:0000:002A:0000:FE04:0A81  FE80:0:0:0:2A:0:FE04:A81
2. One (but only one) contiguous block with all zeros can be replaced by a
double colon
FE80:0:0:0:2A:0:FE04:A81
FE80:0:0:0:2A:0:FE04:A81
Best abbreviation result:
 FE80::2A:0:FE04:A81
 FE80:0:0:0:2A::FE04:A81
FE80::2A:0:FE04:A81
IPv6 Address Allocation
• The process for allocating address blocks (prefixes) is as with IPv4:
IANA
RIR
allocates
LIR
(ISP)
assigns
assigns
•
•
•
•
allocates
End user
End user
IANA allocates prefixes of /23 up to /12 to RIRs
RIR allocates prefixes of /32 up to /19 to LIR, ISP, or End users
LIR/ISP obtains prefixes of /64 up to /48
There can be a National Internet Registry (NIR) between RIR and LIR/ISP
Currently available Global Unicast Addresses
Allocated
IPv6 prefix
IANA
2000::/3
RIR
APNIC
ARIN
Note: Several additional
smaller blocks (longer
prefixes) have been assigned.
ARIN
RIPE
AfriNIC
Allocated
IPv6 prefix
2400::/12
2600::/12
2800::/12
2A00::/12
2C00::/12
University of Toronto
• IPv6 prefix of University of Toronto:
2606:FA00::/32
• Address block is allocated from ARIN
• Number of addresses:
296 = 79,228,162,514,264,337,593,543,950,336 ≈ 8 x 1028
from:
2606:FA00:0000:0000:0000:0000:0000:0000
to:
2606:FA00:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF
32 bits
96 bits
32 bits
64 bits
Subnet ID
Interface ID