Re: RFC6085 update to rfc2464bis - Ethernet or WiFi?
Alexandre Petrescu <alexandre.petrescu@gmail.com> Wed, 11 January 2017 19:00 UTC
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Subject: Re: RFC6085 update to rfc2464bis - Ethernet or WiFi?
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From: Alexandre Petrescu <alexandre.petrescu@gmail.com>
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Date: Wed, 11 Jan 2017 20:00:01 +0100
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Le 11/01/2017 à 10:48, otroan@employees.org a écrit : > Bob, Jinmei, > > As one of the authors of RFC6085 let me try to clarify how it would typically be used. > Scenario: Wireless AP This is WiFi, it is not Ethernet. It is not the same. An IPv6-over-WiFi document remains to be written. This multicast aspect is the tip of the iceberg of differences between the two. Alex > that already knows the L2 unicast address of all stations on a link. > Some APs try to improve on IPv6 multicast on wireless by sending the RAs as L2 unicast to each individual station. > The AP then runs through it's list of L2 unicast addresses and sends the multicast RA with the given L2 unicast mapping. > > 2464bis says: > An IPv6 multicast packet may also be mapped to a unicast Ethernet > Link layer address as defined in Section 6. > > An IPv6 node receiving an IPv6 packet with a multicast destination > address and an Ethernet link-layer unicast address must not drop the > packet as a result using of this form of address mapping. > > > As Jinmei also says, referring to section 6 is then wrong. That implies that the 6085 address mapping uses address resolution. Which is not the case. > > 6085 is indeed very underspecified in stating how the mapping is done, from 6085: > The determination of the unicast Ethernet link-layer > address and the construction of the outgoing IPv6 packet are out of > scope for this document. > > > Either do (Jinmei): > An IPv6 multicast packet may also be mapped to a unicast Ethernet > Link layer address as described in RFC6085. > > Or something like: > An IPv6 packet with a multicast destination address may also be mapped to an > Ethernet link-layer unicast address [RFC6085]. > E.g. when it is clear that only one address is relevant on the link and that the > mapping between an IPv6 multicast destination address and an Ethernet link-layer > unicast address is already known. > > Cheers, > Ole > > > >> On 11 Jan 2017, at 01:05, Bob Hinden <bob.hinden@gmail.com> wrote: >> >> Jinmei-san, >> >>> On Jan 10, 2017, at 11:22 AM, 神明達哉 <jinmei@wide.ad.jp> wrote: >>> >>> On Tue, Jan 10, 2017 at 9:26 AM <jinmei@wide.ad.jp> wrote: >>> >>>>> An IPv6 multicast packet may also be mapped to a unicast Ethernet >>>>> Link layer address as defined in Section 6. >>>> >>>> I think it's more helpful to refer to RFC6085 explicitly here. >>>> Otherwise the proposed text looks good to me. >>> >>> On re-reading it more closely, I wonder whether "as defined in Section >>> 6" may not be very appropriate. RFC6085 intentionally left the >>> mapping open: >>> >>> [...] The determination of the unicast Ethernet link-layer >>> address and the construction of the outgoing IPv6 packet are out of >>> scope for this document. >>> >>> but I suspect it doesn't really intend to perform link-layer address >>> resolution using ND (which is in my understanding what "Section 6" >>> talks about) to determine the unicast Ethernet address. In fact, the >>> address resolution itself uses a multicast IPv6 address, which is >>> derived from the target unicast IPv6 address. So it would be a kind >>> of circular definition. >>> >>> So it's probably even better to just refer to the RFC instead of >>> Section 6: >>> >>> An IPv6 multicast packet may also be mapped to a unicast Ethernet >>> Link layer address as noted in [RFC6085]. >> >> I think the problem remains that RFC6085 isn’t very clear how to do that. Pointing to RFC6085 is that it doesn’t say what to do :-( >> >> It would be good to hear from the authors of RFC6085. Also, what is current practice. >> >>> >>> And, for that matter, this text of Section 6 of rfc2464bis-01 now >>> looks a bit awkward to me: >>> >>> The procedure for mapping IPv6 unicast addresses into Ethernet link- >>> layer addresses is described in [DISC]. >> >> That is original text from RFC2464. I tried to avoid changing anything that wasn’t part of an update or errata. >> >>> >>> On reading both Sections 6 and 7, this "the procedure for mapping" >>> could read some static mapping whereas it should actually refer to >>> dynamic link-layer address resolution. >>> >>> I suggest revising the first paragraph from: >>> >>> The procedure for mapping IPv6 unicast addresses into Ethernet link- >>> layer addresses is described in [DISC]. The Source/Target Link-layer >>> Address option has the following form when the link layer is >>> Ethernet. >>> >>> to: >>> >>> When the link layer is Ethernet, the Ethernet address for an IPv6 >>> unicast address is resolved using the address resolution protocol >>> as defined in [DISC]. The Source/Target Link-layer Address option >>> used in that protocol has the following form. >> >> I find that an improvement (maybe without the “When” text), but I am not sure a change is needed. >> >> Thanks, >> Bob >> >> >>> >>> -- >>> JINMEI, Tatuya >> >> -------------------------------------------------------------------- >> IETF IPv6 working group mailing list >> ipv6@ietf.org >> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 >> -------------------------------------------------------------------- > > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- >
- RFC6085 update to rfc2464bis Bob Hinden
- Re: RFC6085 update to rfc2464bis Sander Steffann
- Re: RFC6085 update to rfc2464bis 神明達哉
- Re: RFC6085 update to rfc2464bis Bob Hinden
- Re: RFC6085 update to rfc2464bis 神明達哉
- Re: RFC6085 update to rfc2464bis Bob Hinden
- Re: RFC6085 update to rfc2464bis otroan
- Re: RFC6085 update to rfc2464bis Alexandre Petrescu
- Re: RFC6085 update to rfc2464bis - Ethernet or Wi… Alexandre Petrescu
- Re: RFC6085 update to rfc2464bis - Ethernet or Wi… Carsten Bormann
- Re: RFC6085 update to rfc2464bis Mark Smith
- Re: RFC6085 update to rfc2464bis - Ethernet or Wi… Fred Baker
- Re: RFC6085 update to rfc2464bis - Ethernet or Wi… Brian E Carpenter
- Re: RFC6085 update to rfc2464bis Bob Hinden