Subject: RE: Some comments regarding draft-ietf-ipngwg-default-addr-select-05.txt

From: "Tony Hain" <[email-masked]>
Date: Tue, 31 Jul 2001 12:32:35 -0700

Erik Nordmark wrote:

> The text that Stig quoted from RFC 2461 says at the end
>    If the Default Router List is empty,
>    the sender assumes that the destination is on-link.
> 
> In Unix implementations a possible implementation of this aspect
> is by creating this route
>         route add default <hostname> -interface
> where <hostname> is the hostname/IP address assigned to the node.

I had always read that section as 'if you don't know a router simply try ND as a last resort'. I would still consider an implementation broken if it interpreted the lack of a router entry to mean that it should declare one of its interfaces to be the default route. I realize this is simply a semantic difference, but mixing the routing table with the neighbor cache seems like an operational disaster waiting to happen. 

> One possible way of making the draft clearer would be to, instead 
> of using the implementation concept of a routing table, express 
> the rule using the conceptual model in RFC 2461.

I didn't read the rule as being restricted to a routing table because it included 'or the current next-hop neighbor'. I agree that could be interpreted as a router, but it could also be just the destination pointed to by the NC entry. How about 'or the current next-hop in the neighbor cache for DB is known to be unreachable'?

Tony

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From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Mon, 06 Aug 2001 08:16:30 +0900

>>>>> On Tue, 31 Jul 2001 12:15:33 -0400, 
>>>>> "Lori Napoli" <[email-masked]> said:

> If you have a multi-homed machine, and you don't have a route to a
> particular destination, over which interface do you suggest the packet be
> sent out over ?  This is in response to the following statement:

> from RFC 2461:

(At least for me) RFC 2461 is not very clear for multiple-interfaces
cases, so the selection of the outgoing interface is implementation
dependent.

Our (KAME's) implementation introduces the notion of "default
interface", which should manually be specified by the user.  The
kernel uses the default interface as the outgoing interface in this
case.

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					[email-masked]
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From: "Lori Napoli" <[email-masked]>
Date: Mon, 6 Aug 2001 17:30:51 -0400

Our implementation uses a concept of default interface by piggybacking that
concept on the routing table.  If a customer wants a default interface,
they can code a default route using that interface.  This then would be the
same default interface that would be used for multicast traffic if no
MULTICAST_IF setsockopt was issued.

Lori

z/OS Communications Server Development - TCP/IP Stack

919-254-6146   T/L 8-444-6146
E-mail: [email-masked]

Erik Nordmark <[email-masked]> on 08/06/2001 05:15:20 PM

Please respond to Erik Nordmark <[email-masked]>

To:   JINMEI Tatuya / 神明達哉 <[email-masked]>
cc:   Lori Napoli/Raleigh/IBM@IBMUS, [email-masked]
Subject:  Re: Some comments regarding
      draft-ietf-ipngwg-default-addr-select-05.txt

> dependent.

RFC 2461 explicitly states that multihoming (which should have said

multi-interfaced hosts) is out of scope.

> case.

Is the same default interface also the default for originating multicast

packets? Or do you have a separate default when no IPv6_MULTICAST_IF

is specified?

  Erik