On Wed, 18 Feb 2009 22:16:33 +0100 Alexandru Petrescu <[email protected]> wrote:
> Mark Smith a écrit : > > On Wed, 18 Feb 2009 21:03:54 +0100 Alexandru Petrescu > > <[email protected]> wrote: > > > >> Dunn, Jeffrey H. a écrit : > >>> Alex, > >>> > >>> While I believe that Suresh is correct in the case of RFC 2464, I > >>> am very interested in the Ethernet implementation that supports > >>> non-64 bit IID. Do you have a reference for this implementation? > >>> Further, are you interested in supporting non-64 bit network > >>> prefixes? If so, let me know offline and we can discuss. > >> Hi Jeff, this (non-rfc2464 IIDs) is possible for other reasons, but > >> hasn't been implemented. I'm happy interest is expressed. > >> > >> In the previous mail I meant to say typical 64bit Ethernet IIDs but > >> shorter prefix (shorter than 64bit, for example 56bit). This > >> implementation is what I meant I know exists. > >> > >> Why is this useful? BEcause it is easier to send RAs with a prefix > >> length that reflects the prefix length really assigned to that > >> router. > >> > > > > Isn't a /64 big enough for all conceivable and practical subnets ? > > Well yes. I think /64 is big enough, maybe more than necessary. > > But if I'm allocated a /48 and do a few subnetting I arrive to around > /56 or /60 to my edge networks. Thus I don't understand why forcing > them to be /64. > > > Some people want to make that longer because they consider it to be > > way too much! > > Well yes, I have even crazier ideas - non-contiguous prefixes (reuse the > wasted fffe space in the middle of the IID), but here I'm not > complaining about that. It'll never fly at IETF anyways. > > >> Actually I'm very surprised to learn people seem to agree all > >> Ethernet links should have precisely 64bit prefixes in the RAs. > >> > > > > It's all links, not just Ethernet, because it's simpler to work with. > > If every subnet is a constant /64, then you never need to specify > > it, and nobody can ever make configuration errors. > > > > Variable length node addresses in IPv4 make sense because IPv4's > > address space is small and tight. With 128 bit IPv6 addresses, there > > isn't that issue, so operational simplicity becomes more important. > > Well operational simplicity may be apparent, sometimes not :-) > It's no apparent to me - I've run IPX networks, so I *know* it's simpler :-) Learning IPv4 and it's subnetting was hardwork after having "learned" or just had work IPX networking. But that was the difference between protocols designed in the late 1970s vs the mid to late 1980s. > A typical dialogue goes like this: > "how much IPv6 space do you need for your network?" That question generally isn't really intended to be asked anymore. The common case intent is that most people will always get enough address space for what they need - actually far more than what they need, so that they rarely if ever need to come back and ask for more. IPv6 address space is really "cheap", so it doesn't hurt to give people much more than what they need, so they don't have to come back for more. Regards, Mark. -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
