At Thu, 19 Feb 2009 00:15:48 +0100, Alexandru Petrescu <alexandru.petre...@gmail.com> wrote:
> Following up my own post, detailing what I meant, and limiting my email > sending rate right after :-) > > Saving wireless bandwidth: allow to send only one PIO in the RA instead > of two. This may be useful for links with limited bandwidth which > imitate the Ethernet API. (e.g. 802.15.4, 802.16). Yes, this is certainly a waste. The problem is how common this type of configuration is, especially for such highly bandwidth sensitive environments. And the next question is whether it's serious enough to warrant an update to the standard. Personally, I'm not yet convinced on that point. > Avoid administrator headaches: allow putting only one Prefix/Length in > the config file, instead of two. > > Avoid need for bridges and proxy ND: avoid the misunderstanding whereby > users try to build bridges (Proxy ND) instead of real routers. My above question also applies here. Plus, IMO I believe this can be well handled in implementations. > Subnet power to the user: avoid IPv6 provider to take the /64 SLAAC > Ethernet limit as enough for many. Provider could thus offer users a > /63 allowing her/him to further subnet. I don't understand the logic here, especially about how this leads to loosen the restriction of 'len(prefix) + len(IID) must be 128'. > DHCPv6 PD power: allow a Prefix Delegation scheme to re-delegate further > (a /56 out of a /52 out of a /48) without each router needing to reserve > a /64 for its own links. Again, I don't understand it. If what you mean is something like this: - router A advertises P::/48 with L=1, A=1 - router B (a downstream of A) advertises P::/52 with L=1, A=1 - router C (a downstream of B) advertises P::/56 with L=1, A=1 while allowing hosts to configure addresses with the shorter prefixes, then hosts won't be able to communicate off-link: host X, which receives an RA from router C and configures P::x, would tries neighbor discovery to send packet to a different host Y, which receives an RA from router A and configure P::y, because P::y is covered by X's on-link prefix, P::/56. This attempt will of course fail. > Avoid prefix-per-host address waste: were it known a /56 could be used > to SLAAC an Ethernet interface - it would be very hard to claim there > are enough /56 prefixes to accomodate one for each mobile. Or, that is > the situation today with /64 (RFC IPv6 cellular, RFC Proxy Mobile IPv6), > a situation which - if put in practice - effectively leads to address > waste. Avoiding prefix-per-host could also lead to designing shared > multicast-capable link layers (for 802.16, 802.15.4), on which ND and > other IPv6 protocols depend so largely. I'm with Brian here. With all due respect, this sounds like a hairsplitting to justify the new rule of allowing address configuration with a shorter length prefix. If you have a real world problem that can only be solved by such a new rule, please go ahead writing a draft with detailing the problem and explaining why the new rule is inevitable. I don't think continuing the hypothetical argument here will lead us to anywhere constructive. --- JINMEI, Tatuya Internet Systems Consortium, Inc. -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
