> -----Original Message-----
> From: James Kempf [mailto:kempf at docomolabs-usa.com]
> Sent: Tuesday, August 08, 2006 1:26 PM
> To: Dave Thaler; Julien Laganier; INT Area
> Cc: NetLMM WG
> Subject: Re: IPv6 addressing model, per-MN subnet prefix, and
broadcast
> domain
>
> Dave,
>
> RFC 1812 Section 2.2.5.1 defines the case where multiple subnets are
> associated with a single interface of a router thusly:
>
> "The inventors of the subnet mechanism presumed that each piece of
an
> organization's network would have only a single subnet number. In
> practice, it has often proven necessary or useful to have several
> subnets share a single physical cable.
Yes the last sentence above is what we mean by multiple subnets on a
single link.
> For this reason, routers
> should be capable of configuring multiple subnets on the same
> physical interfaces, and treat them (from a routing or forwarding
> perspective) as though they were distinct physical interfaces."
The "treat them as though they were distinct interfaces" is just one way
to implement multiple subnets on a single link, but it is not the only
way or necessarily even the recommended way. The sentence is just
saying it should be a configurable option to be able to do it that way.
-Dave
> Is this what you mean by multiple subnets on a single link?
>
> jak
>
> ----- Original Message -----
> From: "Dave Thaler"
> To: "Julien Laganier" ; "INT Area"
>
> Cc: "James Kempf" ; "NetLMM WG"
>
> Sent: Tuesday, August 08, 2006 1:13 PM
> Subject: RE: IPv6 addressing model, per-MN subnet prefix, and
broadcast
> domain
>
>
> If I understand the picture at bottom, this is fine.
> That is, there can be multiple subnet prefixes per link,
> and different hosts may be in different subsets of the
> set of subnet prefixes. All of this is fine in the IP
> addressing model.
>
> Section 2.1 of the [draft-thaler-intarea-multilink-subnet-issues]
draft
> acknowledges this:
>
> In December 1995, the original IP Version 6 Addressing Architecture
> [RFC1884] was published, stating: "IPv6 continues the IPv4 model
> that a subnet is associated with one link. Multiple subnets may be
> assigned to the same link."
>
> Thus it explicitly acknowledges that the current IPv4 model has
been
> that a subnet is associated with one link, and that IPv6 does not
> change this model. Furthermore, a subnet is sometimes considered
to
> be only a subset of a link, when multiple subnets are assigned to
> the same link.
>
> -Dave
>
> > -----Original Message-----
> > From: Julien Laganier [mailto:julien.IETF at laposte.net]
> > Sent: Monday, August 07, 2006 6:21 AM
> > To: Dave Thaler; INT Area
> > Cc: James Kempf; NetLMM WG
> > Subject: IPv6 addressing model, per-MN subnet prefix, and broadcast
> domain
> >
> > Hi Dave, and other folks knowledgeable about IPv6 addressing model,
> >
> > [netlmm at ietf.org CCed, please reply only to int-area at ietf.org]
> >
> > While working on the issues of which addressing model to use in
> > NetLMM, I think I got confused with issues involved the IPv6
> > addressing model (or its assumptions.)
> >
> > I would therefore like to ask you if a potential NetLMM addressing
> > model (per-MN subnet prefix [RFC3314]) would, in some situations,
> > conflict with the IP addressing model.
> >
> > Background
> > ----------
> >
> > Dave's draft on issues involved with multilink subnets
> > [draft-thaler-intarea-multilink-subnet-issues] list some assumptions
> > of the IP addressing model, but there might be other that are not
> > specific to multilink subnets. I'd therefore like to ask you about
> > possible conflicts between IPv6 and RFC3314 addressing model.
> >
> > We are considering the situation of mobile nodes (MNs) attached to a
> > NetLMM domain. The NetLMM domain span multiple access links, each
> > served by a given access router (AR). A MN attaches to one link, and
> > hence to one AR.
> >
> > ( NetLMM domain )
> > / | | |
> > AR AR AR AR AR
> > / /
> > MN MN MN MN MN MN
> >
> > If all of the MNs in the domain uses a common subnet prefix we
> > obviously end-up with a multilink subnet, which is problematic as
> > described in Dave's draft. Now a simple way to avoid multilink
subnet
> > issues is to use a per-MN subnet prefix, as in the IETF
> > recommendation to 3GPP [RFC3314]. That way, each of the MN moves has
> > a different prefix and hence none of the prefix spans more than one
> > link, thus avoiding multilink subnet issues.
> >
> > Issue
> > -----
> >
> > Such model has however raised a question, which is orthogonal to
> > multi-link subnets issues. RFC3314 was proposed for use in a
scenario
> > where the link between the MN and its AR is point-to-point. Now if
we
> > consider a br