-----Original Message-----
From: ipv6 [mailto:ipv6-bounces(_at_)ietf(_dot_)org] On Behalf Of Job Snijders
NEW:
IPv6 unicast routing is based on prefixes of any valid length up to
128 [BCP198]. When using [SLAAC], [ILNP], or [NPT66] the Interface ID
of unicast addresses is required to be 64 bits long. In other use
cases different prefix sizes may be required. For example [RFC6164]
standardises 127 bit prefixes on inter-router point-to-point links.
For most use cases, prefix lengths of 64 bits is RECOMMENDED, unless
there are operational reasons not to do so.
Sounds about right to me. Another exception that requires /64 would be ULAs.
I think that after RFC 2460-bis becomes the standard, this /64 debate will be
revisited. Why? To make it super clear that for unicast, in general, /64 are
going to be the exception, not the rule (as so much text now suggests). The 64
bit prefix applies to the 2000::/3 address space, and those few exceptions.
For example, this is all up in the air still, but we can assume that just as
households are being assigned one /64 prefix frequently, so will cars? Each car
gets a /64. Does anyone think that cars will only include one IPv6 subnet? Not
me. So we will need CIDR.
Bert