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

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Mon, 18 Nov 2002 14:34:59 -0000

Vijay wrote:
> "this is what we do in our implementation. but the static route is 
> not created until the HA receives a binding update from the MR. 
> and when the MR deregisters or when the binding cache entry expires, 
> the static route is removed. but we dont create it manually."

Hi Vijay:

I understand that you're not a static routes believer... Well, in the
context of Nemo, I believe they deserve a good defense. The paradigm is
so different from the traditional fixed world. For instance, the MRs are
virtually all aligned on the home link - a flat model, which is very
different from a router graph topology; one consequence is that
traditional route aggregation is impossible; an other is that the manual
admin of static routes is much much easier; last but not least there's
no way around the Home Link routers (HA/BR) to be found by a routing
protocol, so the routing protocol will not find another path should the
Home Link routers fail to reach a MR. => routing protocols do not bring
you much value here. But they come at a cost, since the bandwidth to the
MRs may be very expensive. 

Question here: why do you need to remove the static routes? One of my
beliefs (requirements?) is that the routing fabric should not be
disturbed by mobile activity. Another belief is that ND should be the
one doing link level resolution, not routing protocols. If the MR is
home, ND will find it. If it's not home but registered, ND will find its
active home agent, and for the other HAs, it makes no difference.
Otherwise, the MR is not reachable and ND will make that clear. Maybe we
should make sure ICMP reports the unreachability of the MNet clearly to
the Correspondents, but I'd rather not remove the routes. 

What do you think?

Pascal

> -----Original Message-----
> From: Vijay Devarapalli [mailto:[email-masked]] 
> Sent: mercredi 13 novembre 2002 19:16
> To: Erik Nordmark
> Cc: Alexandru Petrescu; [email-masked]
> Subject: Re: [nemo] Re: BU adds routes (was: Draft NEMO Agenda)
> 
> 
> Erik Nordmark wrote:
> > 
> > > why would you manually add a static route? this will not 
> scale IMO.
> > 
> > That depends on how you are going to determine which MR is 
> authorized 
> > to inject routes for which prefixes.
> > 
> > The simple way to do this is to have a table with MR identities (in 
> > the form of the security associations for the tunnels or something 
> > else with cryptographic binding to the actual MR), and a list of 
> > allowed prefixes the MR can advertise.
> 
> this is what we do in our implementation. but the static 
> route is not created until the HA receives a binding update 
> from the MR. and when the MR deregisters or when the binding 
> cache entry expires, 
> the static route is removed. but we dont create it manually.
> 
> there are two scenarios in draft-kniveton-mobrtr. in the 
> first, the MR does not run a routing protocol through the 
> bi-directional tunnel. so we do the above in the first 
> scenario. in the second scenario, the 
> MR sends routing updates through the bi-directional tunnel. 
> creating a route is not tied to the binding update in this 
> scenario. but the 
> authorization check (to see if a particular MR is allowed a 
> particular 
> prefix) is still needed.
> 
> Vijay
>

---

From: Vijay Devarapalli <[email-masked]>
Date: Mon, 18 Nov 2002 10:19:26 -0800

hi Pascal,

I am totally confused by your mail. I am not against static routes.
I am against creating these static routes manually and keep them
forever. it makes no sense manually creating and managing static 
routes for (lets say) 1000 mobile routers on a home link. especially 
when they are shut off. I am for creating the routes whenever needed 
(like when the MR sends a BU).

Vijay

> MRs may be very expensive.

that is why we have two scenarios in draft-kniveton-mobrtr. we dont
expect a MR, that was running a routing protocol when at home, to
continue running the same routing protocol (through the bi-directional
tunnel) when away from home.

> Question here: why do you need to remove the static routes? One of my

?? 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.

> active home agent, and for the other HAs, it makes no difference.

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

> the Correspondents, but I'd rather not remove the routes.

it is simpler adding/deleting the route based on whether the MR is 
shutt off or alive.

regards
Vijay

---

From: Alexandru Petrescu<[email-masked]>
Date: 18 Nov 2002 19:34:20 +0100

Vijay Devarapalli <[email-masked]> writes:
> especially when they are shut off. I am for creating the routes
> whenever needed (like when the MR sends a BU).

This could be: "_renewing_ route's lifetime and _changing_ the BC
entry when receiving BU".  It's the same route.

But renewing a route's lifetime is normally done by the routing
daemon, so if we let the routing daemon run on MR (even in consumer
mode) then the routing daemon will update these route's lifetimes on
HA, no need for BUs, even simpler.

> for prefixes. the HA cannot proxy for a prefix.

Me neither, I would not look into converting ND from /128's to
prefixes.  But suffices it for the HA to do proper ND (redirects
included) for the ll of the MR, no need of ND for LFNs.  Except that
ND redirects will add probably too many routes.

Alex

---

From: Christophe Janneteau<[email-masked]>
Date: Tue, 19 Nov 2002 15:18:58 +0100

Hi Vijay,

> (like when the MR sends a BU).

..but to create the static route from an incoming BU, this BU must be
authenticated that to the "MR to MR's prefix" database located on HA.
This database must be filled in with exactly the same information as
needed for a static route...
The cost of manually configuring the static route or manually
configuring the "MR to MR's prefix" database are quite similar IMO...

Christophe.

---

From: Vijay Devarapalli <[email-masked]>
Date: Tue, 19 Nov 2002 09:30:02 -0800

hi Christophe,

go back to one of the earlier mails I sent. in that mail I had
said if there is a way to tie in the mobile router's prefix
with its security credentials, it would be nice. the same way
the same security credentials tie a home address to a particular
MN or MR. that would be the best solution. in its absense the
HA needs to maintain a config file which says which MR is 
authorized for which prefix.

> configuring the "MR to MR's prefix" database are quite similar IMO...

the difference is you have thousands of entries in the routing 
table if you manually add a static route and keep it permanent.
IMO, this is not a preferable thing to do.

Vijay

---

From: Christophe Janneteau<[email-masked]>
Date: Tue, 19 Nov 2002 18:44:41 +0100

Hi,

> authorized for which prefix.

I remember and agree that unless we are able to solve the "prefix
ownership problem" for PSBU (that would be very nice :) we must have a
config file for authorization on the HA, just as you said.

> IMO, this is not a preferable thing to do.

Good point, as long as it is expected that a reasonable number of MR
will be at home from time to time. In the case where all MR are always
away from home then the advantage desappear and you will double the
information on HA:
	- MR/MR-prefix mapping in the static config file
	- In the routing table: MR_prefix entries for all MRs since all are
away from home.

Christophe.

---

From: Vijay Devarapalli <[email-masked]>
Date: Tue, 19 Nov 2002 09:56:15 -0800

>         - In the routing table: MR_prefix entries for all MRs since all are

I very strongly advocate creating routes at the HA only when
needed. only when HA receives a binding update or a routing
update. it is a bad idea keeping the routes permanently (IMO).

Vijay

---

From: Christophe Janneteau<[email-masked]>
Date: Tue, 19 Nov 2002 19:02:05 +0100

Vijay,

I tends to agree with you for a conceptual point of view... the comment
below was only to highlight that in some (realistic) scenarios the
static config file will not avoid a large number of route to be created
in the routing table.
Christophe.