Le 28/12/2011 13:13, Ray Soucy a écrit :
On Wed, Dec 28, 2011 at 6:23 AM, Iljitsch van Beijnum <iljitsch@muada.com> wrote:
Also somehow the rule that all normal address space must use 64-bit interface identifiers found its way into the specs for no reason that I have ever been able to uncover. On the other hand there's also the rule that IPv6 is classless and therefore routing on any prefix length must be supported, although for some implementations forwarding based on> /64 is> somewhat less efficient.
This ambiguity has always bothered me. The address architecture RFC requires a 64-bit interface identifier,
Well yes, but only if it's an address which doesn't start with 000 (3 zero bits). I understand an address which starts with 000 can have an interface id of length generic 128-n where n is prefix length. (RFC4291 "Addressing Arch", pp. 6, 1st par). Generally speaking, my mind is disturbed by suggestions that the Interface ID must always be precisely of length 64. BEcause there is no particularly valid reason to impose it so, other than the vaguely useful and semantically doubtful 'u' bit - any software ever checks it on reception? At an extreme reading, it may look as the "secure" bit. Yours, Alex
but it's required to be unenforced by implementation, which makes it more of a suggestion at best. I think the wording should be updated to changed MUST to SHOULD. That said, and despite my own use of prefix lengths other than 64-bit, I do believe that a 64-bit prefix for each host network is in our long-term interest. Not having to size networks based on the number of hosts is a good thing. Features made possible by a 64-bit address space is a good thing.