IPv6 address assignments
The European regional registry, the RIPE,
has been allocating production IPv6 network prefixes since July 1999.
UKERNA has already received a SubTLA allocation of 2001:0630::/35.
IPv6 addresses are 128-bit, with the lower 64 bits generally being assigned
for the host part of the address (the EUI-64 part). The current recommendation
by the three regional registries is that any IPv6 site should be assigned
a /48 network prefix. That means the site will have 2^16, or roughly
65,000 subnets,
in each of which it can assign up to 2^64 hosts. That is roughly analogous
to a Class A network in IPv4 space, except the host space is much bigger.
With UKERNA receiving a /35 prefix, it will be able to assign 2^(48-35),
or 2^13, or roughly 8,000 sites, assuming a /48 is enough for a site.
The /35 allocation can grown to a /29, since RIPE will reserve those 6 bits
for expansion, so the future site limit is 2^19, which is over 500,000 sites.
The key feature of IPv6 addressing beyond space is aggregation. IPv6 network
prefixes are aggregated from the outset (in IPv4, CIDR was retro-fitted to
partially achieve this), meaning that for any JANET site, UKERNA needs only
advertise 2001:0630::/35 for reachability, given all JANET sites will fall
under that prefix. In IPv4, JANET advertises a significant number of
prefixes, contributing to the expanding size of the Internet backbone
routing table. That table is said to contain over 130,000 routes at present.
Within Bermuda, the JANET NOSC has assigned the floowing prefixes for
the participant universities:
| Southampton | 2001:0630:1fff::/48 |
| Lancaster | 2001:0630:1ffe::/48 |
| UCL | 2001:0630:1ffd::/48 |
These addresses were assigned prior to Internet Draft suggestions that flexible
address assignment policies should be used to allo for possible expansion in
site or subnetwork size.
A full list of global IPv6 SubTLA address assignments can be seen here. There are currently over 100
such assignments.
|
