Subject: RE: [Seamoby] CARD between Routers - will CT do?

From: [email-masked]
Date: Tue, 14 Jan 2003 12:43:31 -0500

Hi James:

One comment below:

-----Original Message-----
From: ext James Kempf [mailto:[email-masked]]
Sent: Tuesday, January 14, 2003 11:39 AM
To: Eunsoo Shim; [email-masked]
Subject: Re: [Seamoby] CARD between Routers - will CT do?

Eunsoo,

There is no need for discovery related messages between ARs. Routers know where
they are, the routing protocol tells them. 

[Hemant] Routing protocol does not tell physical neighborhood. It tells logical neighborhood. So a router one hop away from me could actually be far away physically and no candidate for handoff. Turning it around, routers physically next to each other can be in different BGP domains and BGP aggregated (or otherwise) exchanges do not have this information. So, I think discovery related message are very much required and issues draft has emphasized it. How you do it is open for discussion though.

There is, of course, an issue of the
AR finding APs attached to it, but that is a different question. That would
probably benefit by some protocol, but, of course, we have this problem about
APs being invisible as far as IP is concerned.

[Hemant] Agreed, I think we can delegate this task to link layer standardization bodies.

The idea of using CT for CARD between routers came out of some discussions we've
been having here about how best to implement these protocols. Having a generic
framework within which all the inter-AR signaling can fit could make the
implementation cleaner. For example, one could view the HI/HAck signaling of
FMIP as another instance of CT.  One could imagine extending the routing
protocol to do implement the framework, but having a separate protocol might be
better.

Anyway, maybe this is boiling the ocean. We are already having enough trouble
getting the specs done on CT and CARD for MNs. Maybe we ought to finish that
first, then revisit the issue when we have more experience with implementing
these protocols.

            jak

----- Original Message -----
From: "Eunsoo Shim" <[email-masked]>
To: "James Kempf" <[email-masked]>; <[email-masked]>
Sent: Tuesday, January 14, 2003 6:00 AM
Subject: Re: [Seamoby] CARD between Routers - will CT do?

> Hi, James,
>
> There should be two types of messages between ARs for CARD.
> - Discovery process related
> - Attributes (including information about access points) related
>
> And there can be two modes of attribute information exchange.
> - One time request-response
> - Periodic updates (one time request and follow-up periodic responses)
>
> I have two questions about your suggestion.
> 1) You are suggesting using CT for attribute information exchanges but not
> the discovery related signaling, aren't you?
> 2) Will CT support the above modes of attribute information exchange?
>
> My feeling is that we'd better identify the type of messages for CARD first
> and then can think about reusing any other protocol for the messages. And I
> think we need more discussion or output from the design team regarding the
> message types.
> Thanks.
>
> Eunsoo
>
> ----- Original Message -----
> From: "James Kempf" <[email-masked]>
> To: <[email-masked]>
> Sent: Monday, January 13, 2003 1:58 PM
> Subject: [Seamoby] CARD between Routers - will CT do?
>
>
> > So most of the discussion here has been about CARD between the Mobile Node
> and
> > Access Router, and that's OK since it certainly is an important topic.
> >
> > However, equally important is how two Access Routers exchange information
> about
> > the access points connected to them. This could be statically configured,
> but
> > that would be very inconvenient.
> >
> > I'm wondering if this might be a good application of CT? The "context"
> here
> > would be an authenticatable list of access points connected up to a
> particular
> > router.
> >
> > Comments?
> >
> >             jak
> >
> >
> > _______________________________________________
> > Seamoby mailing list
> > [email-masked]
> > https://www1.ietf.org/mailman/listinfo/seamoby
> >
>
>

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---

From: "James Kempf" <[email-masked]>
Date: Tue, 14 Jan 2003 12:30:17 -0800

Hemant,

> [Hemant] Routing protocol does not tell physical neighborhood. It tells
logical neighborhood. So a router one hop away from me could actually be far
away physically and no candidate for handoff. Turning it around, routers
physically next to each other can be in different BGP domains and BGP aggregated
(or otherwise) exchanges do not have this information. So, I think discovery
related message are very much required and issues draft has emphasized it. How
you do it is open for discussion though.

As I mentioned at the ATL meeting, interdomain CARD is not possible unless the
ISP exposes some part of the internal routing tables to the other domain, namely
the access routers. The access routers are not border routers, they are internal
routers. BCP in the Internet today is to not expose such information to peering
ISPs. Are you proposing that we change this practice?

As for your point about physical v.s. logical, my recollection of past
conversations on this was that we had concluded that it is possible to determine
whether a router is in the geographical neighborhood of another only if a) the
information is configured in b) both routers have access to some source of
geographical information about the other and can calculate the geographical
distance somehow (but that still doesn't tell whether it's possible to move from
a cell of an access point connnected up to one router to a cell connected to the
other router, i.e. wireless connectivity between routers) or c) a mobile node
which can hear both routers tells one about the other either before handoff or
afterwards (which does give wireless connectivity).

Of these three a) is of course always possible, b) is impractical and still
needs some way to determine wireless connectivity, and c) is possible using MN
to AR CARD, together with an inter-router protocol that allows the access router
to tell if the MN is telling the truth. Therefore, I'm curious where you see a
need for additional information to be exchanged about routers about wireless
connectivity, and how that could be determined?

            jak

---

From: "James Kempf" <[email-masked]>
Date: Tue, 14 Jan 2003 12:30:17 -0800

Hemant,

            jak

---

From: "Eunsoo Shim" <[email-masked]>
Date: Tue, 14 Jan 2003 15:58:38 -0800

James,

Actually designing the way to discover Candidate Access Routers is, at
least, one of the core problems for CARD.
And the two proposals (I-Ds) submitted before the design team was formed
contained two ideas for the problem.
As the name "CAR Discovery" suggests, this work started since we looked for
dynamic discovery mechanisms rather than sticking to the static
configuration. So I think the working group needs to discuss possible
solutions and reach a consensus.

If two ISPs are not willing to disclose even the IP addresses and the MAC
addresses of their access points and access routers to each other, well, the
dynamic discovery mechanism won't be used for inter-domain CAR discovery.
But they might do it for seamless roaming between the wireless networks of
theirs as a part of the roaming agreements and there can be business
benefits for them in doing that. So I'd suggest we look for technical
solutions even for inter-domain CAR discovery.
And intra-domain discovery of CARs is beneficial for the wireless ISPs
anyway since it reduces their management overhead.

So I think inter-AR signaling for dynamic discovery should be under our
consideration.

Regards,

Eunsoo

---

From: "Eunsoo Shim" <[email-masked]>
Date: Tue, 14 Jan 2003 15:58:38 -0800

James,

Regards,

Eunsoo

---

From: "James Kempf" <[email-masked]>
Date: Wed, 15 Jan 2003 08:23:47 -0800

> So I think inter-AR signaling for dynamic discovery should be under our

How do you propose to authenticate this information? The current theory of how
intra-domain CARD authentication works, if I understand correctly, is that the
MN provides unauthenticated observations of AP identifiers that it can hear to
the AR, and the AR then uses authenticated information obtained via Radius or
perhap an inter-AR CARD protocol or static configuration about what APs are
actually connected to the network, to deduce that the MN is telling the truth
that the AP is an authorized AP (though the AR can't determine the truth of
wireless connectivity this way).

If we admit information from other ASs, then there needs to be some kind of
inter-AS protocol for obtaining authenticated information about the internal
topology of the other AS.

            jak

---

From: "James Kempf" <[email-masked]>
Date: Wed, 15 Jan 2003 08:23:47 -0800

jak