Subject: comments on draft-kohno-ipv6-prefixlen-p2p-00.txt

From: JINMEI Tatuya / 神明達哉 <[email-masked]>
Date: Mon, 09 Nov 2009 14:36:35 +0900

(resending as I seem to have submitted the original one from the wrong
address)

I've read this draft.  I don't have a strong opinion on the proposal
per se, but have a couple of minor comments:

1. In Section 4, the draft says:

   However, Subnet-router
   anycast address has not been implemented and in practice, this has
   not been a problem.

I'm afraid "has not been implemented" is too strong.  In fact, we have
"implemented" it in the KAME/BSD IPv6 stack in that we implemented
special restrictions (at that time) on anycast addresses and had
experimentally assigned subnet-router anycast addresses on PC-based
IPv6 routers.  In general, it's difficult to declare something hasn't
been implemented because it eliminates any minor implementation
activity, which is almost impossible to prove.

I have no objection to the conclusion itself (i.e. not a problem in
practice) and would rephrase it to something like this:

   However, Subnet-router anycast addresses have not been (widely)
   deployed, and this has not been a problem in practice.

2. In section 5, it states:

         1) A rule described in ICMPv6 [RFC4443] indicates that a
         Destination Unreachable (Code 3) message should be sent by a
         router rather than forwarding packets back onto point-to-point
         links from which they were received if their destination
         address belongs to the link itself.

This sentence is clear, but IMO is not perfectly accurate because an
address doesn't belong t(or isn't assigned to) a *link*; it's assigned
to an interface.  The corresponding text of RFC4443 reads:

   One specific case in which a Destination Unreachable message is sent
   with a code 3 is in response to a packet received by a router from a
   point-to-point link, destined to an address within a subnet assigned
   to that same link (other than one of the receiving router's own
   addresses).

where it's a *subnet* that is assigned to the link.  So, to be very
accurate, I'd propose to revise the text (e.g.) as follows:

         1) A rule described in ICMPv6 [RFC4443] indicates [...]
         if their destination address matches a subnet that belongs to
         the link itself.

---
JINMEI, Tatuya
Internet Systems Consortium, Inc.

---

From: Miya Kohno <[email-masked]>
Date: Mon, 9 Nov 2009 14:44:38 +0800

Thank you, Tatsuya, for your thorough review. 

I think both of your points are apposite. We'll reflect them into the -01 version.

Thanks again,
Miya 
> -----Original Message-----
> From: JINMEI Tatuya / 神明達哉 [mailto:[email-masked]] 
> Sent: Monday, November 09, 2009 2:37 PM
> To: Miya Kohno; Becca Nitzan; [email-masked]; [email-masked]
> Cc: [email-masked]
> Subject: comments on draft-kohno-ipv6-prefixlen-p2p-00.txt
> 
> I've read this draft.  I don't have a strong opinion on the 
> proposal per se, but have a couple of minor comments:
> 
> I'm afraid "has not been implemented" is too strong.  In 
> fact, we have "implemented" it in the KAME/BSD IPv6 stack in 
> that we implemented special restrictions (at that time) on 
> anycast addresses and had experimentally assigned 
> subnet-router anycast addresses on PC-based
> IPv6 routers.  In general, it's difficult to declare 
> something hasn't been implemented because it eliminates any 
> minor implementation activity, which is almost impossible to prove.
> 
> This sentence is clear, but IMO is not perfectly accurate 
> because an address doesn't belong t(or isn't assigned to) a 
> *link*; it's assigned to an interface.  The corresponding 
> text of RFC4443 reads:
> 
> where it's a *subnet* that is assigned to the link.  So, to 
> be very accurate, I'd propose to revise the text (e.g.) as follows:
>

---

From: Fred Baker <[email-masked]>
Date: Tue, 10 Nov 2009 10:53:30 +0900

A note you may find interesting in this context is:

http://www.ietf.org/rfc/rfc5375.txt
5375 IPv6 Unicast Address Assignment Considerations. G. Van de Velde,
      C. Popoviciu, T. Chown, O. Bonness, C. Hahn. December 2008.  
(Format:
      TXT=83809 bytes) (Status: INFORMATIONAL)

You already reviewed RFC 3627, which is good.

On Nov 9, 2009, at 3:44 PM, Miya Kohno wrote:

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---

From: Miya Kohno <[email-masked]>
Date: Tue, 10 Nov 2009 23:47:03 +0800

Fred,

Thank you very much for your pointing the important precedent work.

Consequently, we should narrow down the focus and succinctly put the issue toward -01 version.

It is also pretty much in line with the feedbacks we got from today's WG meeting.

Thank you !!
Miya
> From: Fred Baker [mailto:[email-masked]] 
> Sent: Tuesday, November 10, 2009 10:54 AM
> To: Miya Kohno
> Cc: JINMEI Tatuya / 神明達哉; Becca Nitzan; [email-masked]; 
> [email-masked]; [email-masked]
> Subject: Re: comments on draft-kohno-ipv6-prefixlen-p2p-00.txt
>