Subject: [nemo] RE: IGP and MIP routes.

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Mon, 21 Jul 2003 19:31:40 +0100

> So maybe they want to give an example.  Kent, Pascal, how can one run
> several routing protocols on a machine and nothing breaks?  I suppose
> that if one routing protocol adds a route, and another routing
protocol
> deletes the same route, then some things might break.
> 

The response is depends on the implementation. One thing is sure, when
multiple processes (sa ospf, rip and bgp) can insert/delete routes, the
system had better keep track of whom inserts the route for ownership
checking and easier administration. On IOS, you'll find a letter like O
for OSPF and M for Mobile when you display the routing table.

Also, there'd better be an arbitration mechanism that selects which
route is chosen when 2 different protocols present a route to the exact
same prefix/length. Since the cost is meaningful only within one
process, the arbitration is based on an other setting. This is called
administrative distance in cisco routers. 

For routers, managing routes is a full time business - not a hobby like
for hosts - and they do it well.

> Or, maybe this spec should not care at all about routing protocols,
and
> be entirely silent about how MIP interacts with IGP?
> 

:)

Pascal

---

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Mon, 21 Jul 2003 19:31:40 +0100

protocol

and

:)

Pascal

---

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Mon, 21 Jul 2003 19:31:44 +0100

> -----Original Message-----
> From: Vijay Devarapalli [mailto:[email-masked]]
> Sent: samedi 19 juillet 2003 04:15
> To: Alexandru Petrescu
> Cc: Kent Leung (kleung); S. Felix Wu; Pascal Thubert (pthubert);
[email-masked]
> Subject: IGP and MIP routes.
> 
> Alexandru Petrescu wrote:
> >
> > > anybody else has an opinion on this?
> >
> > Yes.  My personal oppinion is my preference for "implicit" mode and
let
> > the rt protocols manage routes exclusively and not include prefixes
at
> > all in BU.
> 
> Alex and others,
> 
> let me phrase the issue better.
> 
> the question is should the mobile router be able to
> use both prefix information in the binding update and
> a dynamic routing protocol simultaneously to create
> routes at the HA? or should these two mechanisms be
> used exclusive to each other?
> 
> my proposal is
> 
>    When the Mobile Router and the Home Agent exchange routes through
>    routing protocol updates, the Home Agent MUST NOT create routes to
>    the Mobile network when the Binding Update from the Mobile Router
>    is received.  The Mobile Router also MUST NOT include any prefix
>    information in the Binding Update.  Any routes to the Mobile
Network
>    are created at the Home Agent through routing protocol updates.
> 
> Kent and Pascal argue that this restriction should
> not be there. it is currently possible (according to
> them) to run two IGP protocol at the same time and
> nothing breaks. so there is no reason to have this
> restriction.
> 
> my argument is where do you use it? how does the MR
> know which prefix should be sent in the BU and which
> in the routing protocol message? if same prefix is
> sent in both, then it is redundant.

Note that ( I believe that ) the "keep it simple" argument is on our
side. On a real router with multiple protocols running, such a checking
may be real hard to implement, and seems like a process violation. Our
proposal is to let the router operate as it normally does. Doing
otherwise will create controversy for years. Note also that Kent and I
did not discuss that offline, but naturally came to the same conclusion
from our experience on router operations.

Pascal

---

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Mon, 21 Jul 2003 19:31:44 +0100

[email-masked]
let
at
Network

Pascal

---

From: Kent Leung <[email-masked]>
Date: Mon, 21 Jul 2003 18:34:48 -0700

The router will not "break" because it keeps track of the IGPs and
maintains the routing table properly as Pascal described.  Routers
are built to deal with multiple IGPs.  :)

Kent

---

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Tue, 22 Jul 2003 09:00:26 +0100

> original
Network
> suggestion
>    When the Mobile Router and the Home Agent exchange routes of
specific mobile
> network prefixes through routing protocol updates, the Home Agent MUST
> NOT create the routes of the mobile network prefixes to
>    the Mobile Router when the Binding Update from the Mobile Router
>    is received.  The Mobile Router also SHOULD NOT include the mobile
>    network prefixes exchanged by routing protocol in the Binding
Update.
> The routes of the mobile network prefixes to the Mobile Router SHOULD
be
> created at the Home Agent through routing protocol updates.
> 

I waited for other people to get some pulse there. You know my point
from the start. And Ryuji's proposal is not really much better. 

It is (and it should stay) up to the admin of the router to decide, in
case of a same prefix advertised by multiple IGPs, to select which
source is preferred. The way this is done is implementation dependent.
Because it is a router setting, not something in a protocol. MIP does
not have to be any different.

Note that the explicit comes at BU time before the IGP can even run. The
MR has no way to check whether the MNP route will be exchanged later and
by which IGP. I do not want any text there, but if you really want some,
then I'd suggest something that says that Mobile behaves like other IGPs
when it comes to route injection, deletion and redistribution.

Pascal

---

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Tue, 22 Jul 2003 09:00:26 +0100

Network
specific mobile
Update.
be

Pascal

---

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Tue, 22 Jul 2003 13:37:16 +0100

> From: Alexandru Petrescu [mailto:[email-masked]]
> Sent: mardi 22 juillet 2003 14:27
> To: Kent Leung (kleung)
> Cc: Pascal Thubert (pthubert); Vijay Devarapalli; S. Felix Wu;
[email-masked]
> Subject: Re: [nemo] RE: IGP and MIP routes.
> 
> Kent Leung wrote:
> Pascal described a particular router.  I have another router that begs
> to differ from Pascal's particular router.  My router won't break
either
> and figures out which routes are "mobile".
> 

I had a life before cisco :) All routers implementations I've worked on,
not only cisco, had a way to let the admin control which protocol would
win in case of a tie.

> But what of this breakingness can go in a spec if we don't say how
> exactly the break situations are avoided...
> 

Agreed. We need to point out if it differs from traditional IGP to IGP
arbitration. Otherwise, we'd better just say that Nemo basic explicit
and implicit modes (here I mean implicit with a prefix table, not static
routes or dynamic routing protocol) are just yet an other IGP and that
should be administrable in a similar fashion as the other IGPs, which is
implementation dependant.

Pascal

---

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Tue, 22 Jul 2003 13:37:16 +0100

[email-masked]
either

Pascal