Subject: RE: [nemo] Re: BU adds routes (was: Draft NEMO Agenda)

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Mon, 18 Nov 2002 20:00:29 -0000

> 
> hi Pascal,
> 
> I am totally confused by your mail.

Sorry :)

> 
> ?? this is what confused me. in our implementation when the 
> HA receives a BU from the MR, it creats a static route to the 
> Mobile Network. and when the binding cache entry expires, 
> this static route is removed.
> 
No question your implementation works. Weactually do something similar
in our IPv4 support.

Now, in your test config, is that route advertised to the AS via an IGP?
If so, the MR activity send waves across the routing fabric. At a
certain point (how many MRs does that take???), the fabric will be
pushed to the limits and tear down, won't it? 

> 
> there is a problem. ND proxying works for addresses. but does 
> not work for prefixes. the HA cannot proxy for a prefix.
> 

I agree there's some confusion around... There's no need to proxy for a
prefix here, is there? The static route coded on the home routers
(HA/BR) says MNet via MR. So a HA getting a packet for a MNet will
lookup its routing table and derive MR as next hop since it's a direct
route. If the BCE lookup fails, then the HA uses plain ND to locate MR.
If the MR is located on the home link, the packet is forwarded to it,
otherwise the packet is dropped. This is true regardless of whether the
MAC is that of another Home Agent, correct? Works... 
> 
> it is simpler adding/deleting the route based on whether the MR is 
> shutt off or alive.

It is even simpler to do nothing ;) As Erik pointed out recently, the
Mnet->MR mapping must be coded somwhere. The HA/BRs can read that
somewhere, or be that somewhere, and anyway install the routes
accordingly once and for all (almost:). This causes more routes
redistributed into the AS, but at least it's a stable topology. As you
see, both solutions have advantages. But there may be a requirement
associated here, about the impact of mobility to the home AS. Or not?

Pascal

---

From: Erik Nordmark <[email-masked]>
Date: Mon, 18 Nov 2002 22:21:51 +0100 (CET)

> associated here, about the impact of mobility to the home AS. Or not?

Two things to consider.

Depending on the address allocation inside the site these routes might
be aggregatable at the HA. For instance, if a HA serves multiple MRs
the Nemos attached to those MRs might get addresses allocated so that the
HA can inject a single route into the IGP for all of them.
Then the HA would only install its local routes to the individual Nemos
when the tunnels are up. This would reduce both the size of the routing tables
and the rate of change to them, but it assumes that a given MR always connects
to the same MR. (Well, a longer prefix can be injected should it connect
somewhere else.)

There might be cases where one wants to multihome a MR (hence a Nemo)
at two different HAs inside the routing domain.
Thus the MR would have two different home addresses (and home links).
The MR establishes a tunnel with both HAs and both HAs (when the tunnel is
up) injects a route into the IGP. Thus uses the IGP to get redundancy
against HA and home link failures, but it assumes that there is some
basic liveness checks on the tunnels to detect when a tunnel stops working.

  Erik

---

From: Vijay Devarapalli <[email-masked]>
Date: Mon, 18 Nov 2002 14:34:29 -0800

> Now, in your test config, is that route advertised to the AS via an IGP?

only if the MR sends routing updates. they are included as part of
HA's routing updates. we dont have this part implemented yet. we
dont have RIP/OSPF on the client we are working on, yet.

> If so, the MR activity send waves across the routing fabric. At a

through the entire AS? ofcourse not. I doubt if it will go beyond
the home link. routes get aggregated.

> Mnet->MR mapping must be coded somwhere.

not in the form of manually created static routes which stay on
forever.

> redistributed into the AS, but at least it's a stable topology. As you

the routes should aggregated beyond the border router of the home 
link. if not, the network design is bad.

Vijay