Subject: [mif] Issue: Only _one_ default route? draft-ietf-mif-dhcpv6-route-option-04

From: Alexandru Petrescu <[email-masked]>
Date: Tue, 27 Mar 2012 14:31:02 +0200

Dear participants in MIF WG,

Currently draft-ietf-mif-dhcpv6-route-option-04 specifies that only one
default route to be configured by the DHCPv6 Server for a particular client.

draft-ietf-mif-dhcpv6-route-option-04 says:
"    Server MUST NOT define more than one default route."

I do not know why this is so?

In our implementation the DHCP Server delivers a list of default routes
to the Client (draft-mouton...)  Also, ND configures a list of default
routes on the same link.

I find it a bit bizarre that in this group's context the Server is
required so strongly to configure a single default route no more.

I wanted to ask the oppinion of the group about this.

Alex

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From: Markku Savela <[email-masked]>
Date: Tue, 27 Mar 2012 15:34:50 +0300

> to the Client (draft-mouton...) Also, ND configures a list of default

Is also the following configuration out of scope for this group?

- a home network with TWO ISP's providing connection
- both without knowledge of each other
- both send default and specific route(s) (RA or DHCP)

IMHO, my home desktop should really be able to handle
this too (router selection needs to consider which source
address was picked from which router).

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From: Erik Kline <[email-masked]>
Date: Tue, 27 Mar 2012 13:45:22 +0000

> address was picked from which router).

I think this is some of the stuff that 6man has been discussing.

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From: Alexandru Petrescu <[email-masked]>
Date: Tue, 27 Mar 2012 15:50:38 +0200

> I think this is some of the stuff that 6man has been discussing.

Do you think that discussion may have concluded that it's not good to 
have several default routes on the Client?

Alex

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> mif mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/mif

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From: Erik Kline <[email-masked]>
Date: Tue, 27 Mar 2012 14:04:24 +0000

On 27 March 2012 13:50, Alexandru Petrescu <[email-masked]> wrote:
> Do you think that discussion may have concluded that it's not good to have
> several default routes on the Client?

The discussion I'm referring to is about updating the source address
selection depending on the next hop.  This is obviously a more
complicated issue overall, of course.  Unless you get it right, you're
likely to run afoul of BCP38.

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From: Alexandru Petrescu <[email-masked]>
Date: Tue, 27 Mar 2012 16:14:17 +0200

Le 27/03/2012 16:04, Erik Kline a écrit :
> On 27 March 2012 13:50, Alexandru
> Petrescu<[email-masked]>  wrote:
>>>> IMHO, my home desktop should really be able to handle this too
>>>> (router selection needs to consider which source address was
>>>> picked from which router).
>>>
>>>
>> Do you think that discussion may have concluded that it's not good
>> to have several default routes on the Client?
>
> complicated issue overall, of course.  Unless you get it right,
> you're likely to run afoul of BCP38.

I see.  One wouldn't appreciate be subject to Ingress Filtering.

As a sidenote, also there exist solutions in the 6man space about
selecting the source address and even about selecting a route if there
are two similar in the routing table.

RFC3484 comes to mind, which shows a policy table where the routes have
"precedence" fields.  This means two default routes could be present in
the routing table, have a different preference, and be selected
according to some policy keyed by this preference value.

In Neighbor Discovery also exist distinctors to choose among several
default routes present in the Client.

Alex

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From: Ted Lemon <[email-masked]>
Date: Tue, 27 Mar 2012 15:26:45 +0000

> address was picked from which router).

Yes, this seems to be in scope to me.   I think you should submit a draft, since you've described both the problem and the solution quite well.   You are describing the "two provisioning domains" scenario, FWIW.

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From: Erik Kline <[email-masked]>
Date: Tue, 27 Mar 2012 15:30:01 +0000

> Yes, this seems to be in scope to me.   I think you should submit a draft, since you've described both the problem and the solution quite well.   You are describing the "two provisioning domains" s…

Submit to 6man, I think.

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From: Ted Lemon <[email-masked]>
Date: Tue, 27 Mar 2012 15:33:03 +0000

> Submit to 6man, I think.

Thanks for telling us your opinion, Erik.   Is there a reason behind the opinion, or did it just spring into your mind like a tiny, perfect flower?

:)

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From: Erik Kline <[email-masked]>
Date: Tue, 27 Mar 2012 15:39:21 +0000

> Thanks for telling us your opinion, Erik.   Is there a reason behind the opinion, or did it just spring into your mind like a tiny, perfect flower?

I was thinking of the RFC3484bis work going on right now.  If there
are changes that are needed there, it should get reviewed by the same
group reviewing those other changes right now, yes?  It would be a
shame if the two I-Ds crossed in flight, but obviously not the end of
the world.

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From: Brian E Carpenter <[email-masked]>
Date: Wed, 28 Mar 2012 11:16:06 +1300

>> Yes, this seems to be in scope to me.   I think you should submit a draft, since you've described both the problem and the solution quite well.   You are describing the "two provisioning domains"…

The phrase "more than one default route" on its own makes my head hurt,
given the normal meaning in computer science of the word "default".

One default route per source prefix in use makes perfect sense, in view
of the need for address pair selection and ingress-filtering avoidance.
(When I think about it, a default route even makes sense for a ULA prefix.)

> Submit to 6man, I think.

Clearly - the customers for this include MIF, homenet and shim6 to name
only three.

    Brian

    Brian

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From: Lorenzo Colitti <[email-masked]>
Date: Wed, 28 Mar 2012 10:33:58 +0200

> (When I think about it, a default route even makes sense for a ULA prefix.)

No, multiple default routes make sense even when they're not
source-specific. For example, they make sense when you have two routers and
one of them can go down. Remember that a route includes a next-hop, and
that RFC 4861 defines a default router list (which is a list of possible
next-hops for the default route).

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From: Brian E Carpenter <[email-masked]>
Date: Thu, 29 Mar 2012 08:32:40 +1300

> next-hops for the default route).

Fair enough, although if we were starting again there might be a better way
of doing it.

      Brian