RE: I-D Action:draft-ietf-v6ops-ipv6-cpe-router-03.txt

["Templin, Fred L" <Fred.L.Templin@boeing.com>]

Hi Mark,

> -----Original Message-----
> From: Mark Smith [mailto:ipng@69706e6720323030352d30312d31340a.nosense.org]
> Sent: Saturday, January 09, 2010 4:48 AM
> To: Templin, Fred L
> Cc: Ole Troan; IPv6 Operations
> Subject: Re: I-D Action:draft-ietf-v6ops-ipv6-cpe-router-03.txt
> 
> Hi Fred,
> 
> On Fri, 8 Jan 2010 08:58:51 -0800
> "Templin, Fred L" <Fred.L.Templin@boeing.com> wrote:
> 
> > Ole,
> >
> > > -----Original Message-----
> > > From: owner-v6ops@ops.ietf.org [mailto:owner-v6ops@ops.ietf.org] On Behalf Of Ole Troan
> > > Sent: Friday, January 08, 2010 4:29 AM
> > > To: Mark Smith
> > > Cc: IPv6 Operations
> > > Subject: Re: I-D Action:draft-ietf-v6ops-ipv6-cpe-router-03.txt
> > >
> > > Mark,
> > >
> > > > On Fri, 18 Dec 2009 09:09:21 -0800
> > > > Fred Baker <fred@cisco.com> wrote:
> > > >
> > > >> I will open a WGLC on this after new years; My mind will be elsewhere
> > > >> for the coming two weeks, I imagine yours will as well. However, if
> > > >> you want to start reading/commenting now...
> > > >>
> > > >
> > > > I hope I'm not going to look silly because I've missed it, however, do
> > > > these CPE (as they are routers) issue RAs on their WAN interface? I'd
> > > > think a statement relating to whether they do or don't, and if they do,
> > > > what options MUST/MUST NOT etc. are permitted should be covered in the
> > > > WAN interface section.
> > > >
> > > > (as a side note, a possible use for these CPE issuing RAs is to
> > > > announce support of optional capabilities - I'm thinking about the idea
> > > > of prefix-redirects for more optimal inter-CPE traffic flow, and a
> > > > prefix-redirect capability announcement to the upstream provider
> > > > routers in the CPE's WAN RAs would allow the provider routers to know
> > > > not to send prefix-redirects to CPE that don't support that capability)
> > >
> > > is not the following (reformatted) requirement not clear enough?
> > >
> > > W-1:  When the router is attached to the WAN interface link it MUST
> > >          act as an IPv6 host for the purposes of stateless or stateful
> > >          interface address assignment ([RFC4862]/[RFC3315]).  The router
> > >          MUST act as a requesting router for the purposes of DHCP prefix
> > >          delegation ([RFC3633]).
> > >
> > > "acting as a host" is the key here. feel free to suggest better text if you don't think that's
> clear
> > > enough.
> > >
> > > the WAN interface which is a host for some purposes and a router for others is stretching the
> > > definitions in RFC4861 already. having an interface which can do both RS and RA at the same time
> > > would be stretching it too far.
> >
> > Why can't a CPE router send unicast RAs to other CPE
> > routers as long as they are not malicious and do not
> > in any way conflict with the RAs sent by SP routers?
> >
> 
> I think on some networks that could have multicast traffic volume
> related scaling issues.

That is why I said "unicast RAs" and not multicast ones.

> It's quite possible to build single Ethernet
> link layers using DSL that have 100s or 1000s of CPE attached.

This is consistent with the model I have in mind.

> It also
> seems a bit redundant to have the CPEs fully aware of all their
> neighbours' downstream prefixes, yet be unlikely to use those routes
> very often.

This is *not* consistent with the model I have in mind.
I only want CE routers to become aware of neighbors'
downstream prefixes on an on-demand basis; I do not
want the CE router to have to pre-populate its routing
tables with routes for all potential neighboring CEs.

> My thinking has been that a prefix-redirect option, with appropriate
> rate-limits, issued by the SP router toward the originating CPE, would
> be a more scalable and less resource consuming way to achieve optimal
> CPE-to-CPE forwarding.

This is consistent with the model I have in mind.

> As a prefix-redirect option doesn't currently exist, it'd be both
> redundant and resource consuming for the SP router to continue to send
> prefix-redirects to CPE that wasn't paying attention to them. One
> thought I'd had was if the CPE were issuing RAs, they announce a
> prefix-redirect capability option. The SP router would then know it
> could send prefix-redirects to the announcing CPE. This CPE router
> state in the SP router could also be used to track per-CPE
> prefix-redirect rate limits, rather than having a global
> prefix-redirect rate limit.

Yes, I like the idea of having the SP router track
whether/not the CE router will heed the redirects.

Fred
fred.l.templin@boeing.com

> Regards,
> Mark.