RE: [v6ops] RFC4861 question - short prefixes in PIOs
"Templin (US), Fred L" <Fred.L.Templin@boeing.com> Wed, 26 June 2019 20:18 UTC
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From: "Templin (US), Fred L" <Fred.L.Templin@boeing.com>
To: Dave Thaler <dthaler@microsoft.com>, 神明達哉 <jinmei@wide.ad.jp>
CC: 6man <6man@ietf.org>
Subject: RE: [v6ops] RFC4861 question - short prefixes in PIOs
Thread-Topic: [v6ops] RFC4861 question - short prefixes in PIOs
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Date: Wed, 26 Jun 2019 20:17:51 +0000
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Hi Dave, I agree that what I want is more akin to RIO than to “traditional” PIO, but then I saw David Farmer’s note about RFC8028 and that seems to be more in line with what I am looking for. Certainly, multi-homing needs to be accommodated and RFC8028 seems to support that while using the ubiquitous standard PIO albeit with A=L=0. Is there some reason to prefer RIOs? Thanks - Fred From: Dave Thaler [mailto:dthaler@microsoft.com] Sent: Wednesday, June 26, 2019 10:40 AM To: Templin (US), Fred L <Fred.L.Templin@boeing.com>; 神明達哉 <jinmei@wide.ad.jp> Cc: 6man <6man@ietf.org> Subject: RE: [v6ops] RFC4861 question - short prefixes in PIOs RIO should add a route with the next hop of the router, where the prefix is not an on-link prefix. PIO should be for on-link prefixes, i.e., either the receiver should create a SLAAC address or the receiver should add an on-link route, or both. Dave From: ipv6 <ipv6-bounces@ietf.org<mailto:ipv6-bounces@ietf.org>> On Behalf Of Templin (US), Fred L Sent: Wednesday, June 26, 2019 9:52 AM To: 神明達哉 <jinmei@wide.ad.jp<mailto:jinmei@wide.ad.jp>> Cc: 6man <6man@ietf.org<mailto:6man@ietf.org>> Subject: RE: [v6ops] RFC4861 question - short prefixes in PIOs OK, thanks. Then, it seems to me that what I really want is a Route Information Option (RIO) [RFC4191] because what I am looking for is a way to establish a short prefix in the IPv6 forwarding table that directs packets to a specific outgoing interface (or, more precisely, to a specific router on a specific outgoing interface). But, with RIO, the prefix would not be added to the interface prefix list in the same way as for PIO - correct? Thanks - Fred From: 神明達哉 [mailto:jinmei@wide.ad.jp] Sent: Wednesday, June 26, 2019 9:23 AM To: Templin (US), Fred L <Fred.L.Templin@boeing.com<mailto:Fred.L.Templin@boeing.com>> Cc: 6man <6man@ietf.org<mailto:6man@ietf.org>> Subject: Re: [v6ops] RFC4861 question - short prefixes in PIOs (I'm only copying 6man, as I believe it's purely a protocol spec question) At Wed, 26 Jun 2019 15:56:36 +0000, "Templin (US), Fred L" <Fred.L.Templin@boeing.com<mailto:Fred.L.Templin@boeing.com>> wrote: > > I have an RFC4861 question (several actually) on short prefixes in RA PIOs: > > 1) If a PIO includes a prefix with length less than 64 (e.g., 2001:db8::/32) and with L=1, does it > > mean that 2001:db8::/32 should be added to the interface prefix list? In my interpretation (ditto for subsequent questions), yes. > 2) If yes to 1), does it mean that packets forwarded to the interface for any destination covered > > by 2001:db8::/32 will trigger Address Resolution instead of forwarding to a default router? Yes. > 3) If the PIO instead has L=0, does it mean that 2001:db8::/32 is “associated” with the link but > not necessarily “on-link”? I'm not sure how to interpret it (in particular I'm not sure what "associated with the link" means), but my interpretation of L=0 is that the RA doesn't say anything about the on-link-ness of that prefix. See also the description of the L flag in RFC4861: L 1-bit on-link flag. [...] When not set the advertisement makes no statement about on-link or off-link properties of the prefix. In other words, if the L flag is not set a host MUST NOT conclude that an address derived from the prefix is off-link. That is, it MUST NOT update a previous indication that the address is on-link. > 4) If yes to 3), does it mean that 2001:db8::/32 should be added to the IPv6 forwarding table > > as a “route-to-interface” with the receiving interface as the next hop? No. See the second MUST NOT of the RFC4861 text cited above. > 5) Does A=1 have any meaning for prefixes with length less than 64? Or, must prefixes with > > length less than 64 set A=0? As far as RFC4861 is concerned, the A flag has no meaning, regardless of the prefix length. It only matters in RFC4862. In terms of RFC4862, whether "A=1 has any meaning for prefixes with length less than 64" depends on the length of the IID of the link; if the prefix length != 128-IIDLength, the validation rule 5.5.3 d) of RFC4862 makes the prefix ignored. If non-64 prefix length is invalid in terms of RFC4862 in that sense, it'd be *safe* to avoid setting the A flag, but the protocol specification doesn't say it *must* be so. You may also want to check https://tools.ietf.org/html/draft-jinmei-6man-prefix-clarify-00<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftools.ietf.org%2Fhtml%2Fdraft-jinmei-6man-prefix-clarify-00&data=02%7C01%7Cdthaler%40microsoft.com%7C8553bcb309874f844e9408d6fa56b303%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636971647627136134&sdata=AQ8dP3HU4UonvrTkx5TMKYxgS%2FI%2BAxkImKLi%2B9M8aBk%3D&reserved=0> I believe it clarifies many of the above questions. -- JINMEI, Tatuya
- RFC4861 question - short prefixes in PIOs Templin (US), Fred L
- Re: [v6ops] RFC4861 question - short prefixes in … 神明達哉
- RE: [v6ops] RFC4861 question - short prefixes in … Templin (US), Fred L
- RE: [v6ops] RFC4861 question - short prefixes in … Dave Thaler
- Re: [v6ops] RFC4861 question - short prefixes in … David Farmer
- RE: [v6ops] RFC4861 question - short prefixes in … Templin (US), Fred L
- RE: [v6ops] RFC4861 question - short prefixes in … Templin (US), Fred L
- RE: [v6ops] RFC4861 question - short prefixes in … Dave Thaler
- Re: [v6ops] RFC4861 question - short prefixes in … David Farmer
- Re: [v6ops] RFC4861 question - short prefixes in … Brian E Carpenter
- Re: [v6ops] RFC4861 question - short prefixes in … Mark Smith
- Re: [v6ops] RFC4861 question - short prefixes in … Alexandre Petrescu
- Re: [v6ops] RFC4861 question - short prefixes in … Mark Smith
- Re: RFC4861 question - short prefixes in PIOs Michael Richardson
- Re: RFC4861 question - short prefixes in PIOs Mark Smith
- Re: [v6ops] RFC4861 question - short prefixes in … Alexandre Petrescu
- Re: [v6ops] RFC4861 question - short prefixes in … Philip Homburg
- Re: [v6ops] RFC4861 question - short prefixes in … Mark Smith
- Re: [v6ops] RFC4861 question - short prefixes in … Pascal Thubert (pthubert)