On Sat, 28 Aug 2010 22:43:21 -0400 Christopher Morrow <christopher.mor...@gmail.com> wrote:
> On Sat, Aug 28, 2010 at 7:34 PM, Mark Smith > <i...@69706e6720323030352d30312d31340a.nosense.org> wrote: > > > I think IPv6 "CIDR" i.e. longest match rule across the whole 128 bits is > > really only insurance against having to perform a whole of Internet > > upgrade, similar to what had to happen when CIDR was introduced, should > > folk are already holding (internally) /128's for things, I suppose > they could have /64's, but that means dedicating a 'LAN' to some task > (anycast of a nameserver, for instance) when you really only want to > use a 'host' for that. > This is one of the issues. People are being unnecessarily precious about address space. What real benefit do they gain? It seems that their IPv4 "must conserve address space" mentality is so ingrained that they can't even conceive of anything else. That's what makes me think that they haven't experienced any other protocols that trade addressing bits for operational convenience. Of course they've probably used Ethernet, and never or rarely set MAC addresses, so they've already experienced that sort of operational convenience, but somehow don't realise that it can also exist at layer 3. > It means using a 'LAN' for each 'host' you want to anycast... or > losing some flexibility in your service management/offering. > > moving back to 'classful' addressing isn't a move forward, or not such > that it's worth the move with the additional overhead incurred. That's not what I'm advocating. If I was, I'd be advocating separate network and node fields in the IPv6 header - as IPX/XNS/Appletalk etc. implemented. > I > agree that making almost all 'LAN' segments a /64 is a fine plan, So why isn't it a fine plan for all links in a network? We can afford the address space. > some > folks may choose other boundaries and in those cases will not get RA > or other things, they may not need those things though. > A number of innovations are possible and have been developed in IPv6 because the single and soft boundary between the network and node portions at the 64 bit mark. These innovations would not have been possible if that soft boundary hadn't been chosen in the past. If that soft boundary is now eliminated, then what useful innovations won't be possible in the future? Maybe somebody will come up with an innovation that would be of real benefit on point-to-point links between routers, however it needs 64 bit identifiers. Yet if /127s are widely deployed, then that innovation may never be worth developing because it can't be widely deployed. It may even never be thought of, because people will become ingrained in "point-to-point" links are only /127s. One of my concerns about /127s is that it'll become the thin edge of the wedge for also eliminating the /64 boundary on LANs. Then we'll have spotty SLAAC support, different devices with different prefix lengths etc., - all the problems we've had with incorrect subnet masks in IPv4, as well as new ones like SLAAC not working. Fundamentally, people seem to be wanting to introduce constraints into IPv6 that seem to have no other reason to be other than "that's how we did it in IPv4". Yet there doesn't seem to be any questioning of why those methods had to be implemented in IPv4, and if the design of IPv6 eliminates those IPv4 constraints - and if we'd had a choice in IPv4, would we have accepted them in the first place. Regards, Mark. -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
