Re: Question on anycast IID range(s)
David Farmer <farmer@umn.edu> Fri, 04 January 2019 00:36 UTC
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From: David Farmer <farmer@umn.edu>
Date: Thu, 03 Jan 2019 18:35:44 -0600
Message-ID: <CAN-Dau2rJBNhgH7VOsN8BASnN1vLFDX0HfH_nhmy4XANc+XOGw@mail.gmail.com>
Subject: Re: Question on anycast IID range(s)
To: Suresh Krishnan <suresh.krishnan@gmail.com>
Cc: Brian E Carpenter <brian.e.carpenter@gmail.com>, 6man 6man <ipv6@ietf.org>, ek@loon.co
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On Thu, Jan 3, 2019 at 5:56 PM Suresh Krishnan <suresh.krishnan@gmail.com> wrote: > Hi Brian, > > On Jan 2, 2019, at 11:15 PM, Brian E Carpenter < > brian.e.carpenter@gmail.com> wrote: > > On 2019-01-03 17:01, Suresh Krishnan wrote: > > <AD Hat off> > > Hi Brian/Erik/Kerry, > > On Jan 2, 2019, at 4:52 PM, Brian E Carpenter <brian.e.carpenter@gmail.com> > wrote: > > On 2019-01-03 09:37, Kerry Lynn wrote: > > On Wed, Jan 2, 2019 at 2:57 PM Brian E Carpenter < > brian.e.carpenter@gmail.com> wrote: > > On 2019-01-03 07:15, Kerry Lynn wrote: > > Thanks Erik, > > My question was ill-posed *and* contained a typo. I'm really trying to > figure out > which range(s) of IIDs RFC 2526 is trying to reserve for anycast use. I > now think > the answer is fdff:ffff:ffff:ff80-fdff:ffff:ffff:ffff based on RFC 5453 > > and > > > > https://www.iana.org/assignments/ipv6-interface-ids/ipv6-interface-ids.xhtml > > If I take RFC2526 literally, ffff:ffff:ffff:ff80-ffff:ffff:ffff:ffff > is also reserved, for IIDs not in modified EUI-64 format. > > That's the problem with RFC2526; at the time it was written there was a > class of > IPv6 address that required IIDs to be 64-bits AND in EUI-64 format. Given > that the > latter requirement no longer seems to hold, it would seem the basis for the > range > fdff:ffff:ffff:ff80-fdff:ffff:ffff:ffff no longer exists. Yet, this range > is now enshrined in > RFC5453 and > > https://www.iana.org/assignments/ipv6-interface-ids/ipv6-interface-ids.xhtml > > But RFC7217 doesn't mention RFC2526, which might be a bug. > > > RFC7217 (and any other proposal for IID generation) should take RFC5453 and > its associated registry into consideration. > > > It does. But the gap is that RFC5453 doesn't call out > ffff:ffff:ffff:ff80-ffff:ffff:ffff:ffff > > > Looking back at my notes on what became RFC5453, this is not a gap but > something I had intentionally left out of RFC5453 based on the addressing > usage then. I will try to explain my reason why and we can see if this > still makes sense or not. > > According to RFC2526, "for IPv6 address types required to have to have > 64-bit interface identifiers in EUI-64 format” the reserved anycast range > was only > > FDFF:FFFF:FFFF:FF80-FDFF:FFFF:FFFF:FFFF > > Since RFC4291 defined all the space other than ::/3 to be used only with > 64-bit IIDs, and the goal of RFC5453 was to avoid address conflicts for > SLAAC (which used 64 bit IIDs due to reasons explored in great detail in > RFC7421), this is the range that was put into RFC5453. > > Yes. I've posted an erratum to 5453. At the time, ffff:etc might > have seemed like a corner case, but 2526 did actually cover it. > > > 2526 covered this *only* for non 64-bit non EUI-64 IIDs. > > > That's not how I read it. IMHO, it covered it for non-EUI-64 IIDs > of length N, and there's nothing to say that N may not be 64. > (In fact, our current addressing architecture states that N==64, > as we all know only too well.) > > > :-). Yes, we do. The addressing architecture also states in Section 2.5.1. > that > > " For all unicast addresses, except those that start with the binary > value 000, Interface IDs are required to be 64 bits long and to be > constructed in Modified EUI-64 format." > Well, after the RFC7136 update it says; For all unicast addresses, except those that start with the binary value 000, Interface IDs are required to be 64 bits long. If derived from an IEEE MAC-layer address, they must be constructed in Modified EUI-64 format. And RFC8064 effective makes Modified EUI-64 format OPTIONAL, or a MAY at best, one could even argue it depercated Modified EUI-64, A.K.A. NOT RECOMMENDED. > So if we want to add the omitted range, we need to restrict it to non ::/3 > prefixes as well. > > If we do want to cover the non 64-bit cases then the range Brian suggested > ave is insufficient (because the IIDs will not fit in the 64-bit range > suggested) and would require a more considered change. > > For the specific case of N==64 I don't see that as necessary. > > Agree that the N==64 case works fine but I was talking about whether the > WG wanted to cover the non-64-bit cases as well. > So, I believe ffff:ffff:ffff:ff80-ffff:ffff:ffff:ffff should be added to the reserved list and RECOMMENDED for use as Anycast addresses. And, fdff:ffff:ffff:ff80-fdff:ffff:ffff:ffff should remain on the reserved list, but NOT RECOMMENDED for use as Anycast addresses, as a result of RFC8064. They both should have been on the list originally. Further, I believe the original intent for Modified EUI-64 is the way RFC7136 updates it to, especially if you take the paragraphs following that talk about "Modified EUI-64 format-based interface identifiers". Talking about them that way kind of implies there are interface identifiers that are not based on Modified EUI-64 format, despite the paragraph above originally said. And yes we should assume N==64. But as Ole said, it is quite clear even if N!=64 that RFC2526 say "the highest 128 interface identifier values are reserved." Thanks. > Thanks > Suresh > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- > -- =============================================== David Farmer Email:farmer@umn.edu Networking & Telecommunication Services Office of Information Technology University of Minnesota 2218 University Ave SE Phone: 612-626-0815 Minneapolis, MN 55414-3029 Cell: 612-812-9952 ===============================================
- Question on anycast IID range(s) Kerry Lynn
- Re: Question on anycast IID range(s) Erik Kline
- Re: Question on anycast IID range(s) Kerry Lynn
- Re: Question on anycast IID range(s) Brian E Carpenter
- Re: Question on anycast IID range(s) Kerry Lynn
- Re: Question on anycast IID range(s) Brian E Carpenter
- Re: Question on anycast IID range(s) Fernando Gont
- Re: Question on anycast IID range(s) Fernando Gont
- Re: Question on anycast IID range(s) Suresh Krishnan
- Re: Question on anycast IID range(s) Brian E Carpenter
- Re: Question on anycast IID range(s) Mark Smith
- Re: Question on anycast IID range(s) Ole Troan
- Re: Question on anycast IID range(s) Kerry Lynn
- Re: Question on anycast IID range(s) Suresh Krishnan
- Re: Question on anycast IID range(s) Kerry Lynn
- Re: Question on anycast IID range(s) David Farmer
- Re: Question on anycast IID range(s) Kerry Lynn
- Re: Question on anycast IID range(s) David Farmer
- Re: Question on anycast IID range(s) Ole Troan
- Re: Question on anycast IID range(s) Kerry Lynn
- Re: Question on anycast IID range(s) Ole Troan
- Re: Question on anycast IID range(s) Brian E Carpenter
- Re: Question on anycast IID range(s) Ole Troan
- Re: Question on anycast IID range(s) Sander Steffann
- Re: Question on anycast IID range(s) David Farmer
- Re: Question on anycast IID range(s) David Farmer
- Re: Question on anycast IID range(s) David Farmer
- Re: Question on anycast IID range(s) Kerry Lynn