Subject: RE: comments on draft-ietf-6man-ipv6-subnet-model-03

From: "Manfredi, Albert E" <[email-masked]>
Date: Thu, 7 May 2009 12:49:31 -0400

> -----Original Message-----
> From: Hemant Singh (shemant) [mailto:[email-masked]] 

> Folks,
> 
> The issue related to "the statement in our draft that says to 
> not issue an address resolution for an IPv6 address that is 
> not on-link" has been addressed by the following new and 
> amended text in Intro section of our 04 draft that has been 
> posted today.  I also fixed a few typos in the new text below 
> but the typos do exist in the -04 version.
> 
> OLD:
> 
>    A host only performs address resolution for IPv6 addresses that are
>    on-link.  Packets to any other address are sent to a 
> default router.
>    If there is no default router, then the node should send an ICMPv6
>    Destination Unreachable indication as specified in [RFC4861] - more
>    details are provided in the Host Behavior and Rules section.  (Note
>    that [RFC4861] changed the behavior when the Default Router List is
>    empty.  The behavior in the old version of Neighbor Discovery
>    [RFC2461] was different when there were no default routers.)
> 
> 
> NEW:
> 
>    IPv6 packets sent using the Conceptual Sending Algorithm 
> as described
>    in [RFC4861] only trigger address resolution for IPv6 
> addresses that
>    are on-link.  Note that transmission of ND messages is not governed
>    by the Conceptual Sending Algorithm.  Packets to any other address
>    are sent to a default router.  If there is no default router, then
>    the node should send an ICMPv6 Destination Unreachable 
> indication as
>    specified in [RFC4861] - more details are provided in the Host
>    Behavior and Rules section.  (Note that [RFC4861] changed the
>    behavior when the Default Router List is empty.  The 
> behavior in the
>    old version of Neighbor Discovery [RFC2461] was different 
> when there
>    were no default routers.)  Note that ND is scoped to a single link.
>    All Neighbor Solicitation responses are assumed to be sent out the
>    same interface on which the corresponding query was received.

Sorry, but I find this confused.

The first sentence says that on-link messages only will trigger ND (much
like ARP in IPv4).

The second sentence says that ND is not governed by the Conceptual
Sending Algorithm. So this means that the first sentence doesn't hold
any longer?

The third sentence continues the thought process of the first sentence,
and seems to ignore the fact that ND does not follow this model anymore.

Sticking in that second sentence seems to make the third sentence a non
sequitur. Unless the effect of this changed behavior of ND is explained,
even if only briefly.

Bert

---

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Thu, 7 May 2009 14:01:32 -0400

Bert,

Please see a revised NEW paragraph below and let us know if this is more
clear.  Basically we meant to say that when sending an NA in response to
an NS, the host does not use the Conceptual Sending Algorithm which
means that if the NA response cannot be sent out because the ND-cache
doesn't have an entry to the NA destination, then the host issues an
address resolution to resolve the destination.

-----Original Message-----
From: Manfredi, Albert E [mailto:[email-masked]] 
Sent: Thursday, May 07, 2009 12:50 PM
To: Hemant Singh (shemant)
Cc: [email-masked]
Subject: RE: comments on draft-ietf-6man-ipv6-subnet-model-03

   IPv6 packets sent using the Conceptual Sending Algorithm as described
   in [RFC4861] only trigger address resolution for IPv6 addresses that
   are on-link.  Packets to any other address are sent to a default
router.  
   If there is no default router, then the node should send an ICMPv6 
   Destination Unreachable indication as specified in [RFC4861] - more 
   details are provided in the Host Behavior and Rules section.  (Note 
   that [RFC4861] changed the behavior when the Default Router List is
empty.  
   The behavior in the old version of Neighbor Discovery [RFC2461] was 
   different when there were no default routers.)  Note that ND is
scoped 
   to a single link.  All Neighbor Solicitation responses are assumed to

   be sent out the same interface on which the corresponding query was 
   received without using the Conceptual Sending Algorithm.

Hemant

---

From: "Manfredi, Albert E" <[email-masked]>
Date: Thu, 7 May 2009 14:57:43 -0400

> address resolution to resolve the destination.

------------------------
>    received without using the Conceptual Sending Algorithm.
-------------------------

Hemant,

Okay, sounds better to me. Now these sentences:

(Note that [RFC4861] changed the behavior when the Default Router List
is empty. The behavior in the old version of Neighbor Discovery
[RFC2461] was different when there were no default routers.)

I would either delete those sentences, or change the second sentence to
read:

"In the old version of Neighbor Discovery [RFC2461], if the Default
router List is empty, rather than sending the ICMPv6 Destination
Unreachable indication, the RFC2461 node assumed that the destination
was on-link."

In other words, I would explain the difference if you're going to bother
mentioning that there is a difference.

Bert

---

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Thu, 7 May 2009 15:28:21 -0400

Bert,

Please see in-line below.

>Sent: Thursday, May 07, 2009 2:58 PM

>mentioning that there is a difference.

Makes total sense.  We will take your suggested text and replace the
second sentence.

Thanks much for both your emails.

Hemant