Subject: Question on conformance to RFC3879

From: "V, Raman K (MCBS-UPEL)" <[email-masked]>
Date: Thu, 4 Nov 2010 10:08:56 +0000

Hi All,
  This is a question about the correct interpretation of RFC3879. Conformance to this RFC is a requisite for USGv6/DISRv3 certification, so I am trying to figure out the right thing to do inside our IPv6 stack.

A portion of Section 4 of this RFC (the crux, really) is reproduced below:

   This document formally deprecates the IPv6 site-local unicast prefix
   defined in [RFC3513], i.e., 1111111011 binary or FEC0::/10.  The
   special behavior of this prefix MUST no longer be supported in new
   implementations.  The prefix MUST NOT be reassigned for other use
   except by a future IETF standards action.  Future versions of the
   addressing architecture [RFC3513] will include this information.

It seems to clearly say that an IPv6 stack must no longer support site-local addresses, to be able to conform this RFC. So, would I be right in assuming that our stack should simply drop the support for site-local addresses? Or should I put more emphasis on the words "new implementations" and say that mine isn't a new implementations (we have had our IPv6 stack in the market for a while), so we should continue to support site-local addresses?

We are going for a USGv6 certification and knowing the right thing to do from this expert community would very helpful. Any thoughts in this area or any pointers in this regard would be greatly appreciated.

Thanks
Raman.

---

From: Brian Haberman <[email-masked]>
Date: Thu, 04 Nov 2010 10:31:11 -0400

On 11/4/10 6:08 AM, V, Raman K (MCBS-UPEL) wrote:
> Hi All, This is a question about the correct interpretation of
> RFC3879. Conformance to this RFC is a requisite for USGv6/DISRv3
> certification, so I am trying to figure out the right thing to do
> inside our IPv6 stack.
> 

When I maintained an IPv6 stack, I simply removed any of the special
handling necessary for FEC0::/10 and treated it as any other global IPv6
prefix.  For example, I removed all of the scope zone checks that are
defined for scoped addresses (RFC 4007).

> It seems to clearly say that an IPv6 stack must no longer support
> site-local addresses, to be able to conform this RFC. So, would I be
> right in assuming that our stack should simply drop the support for
> site-local addresses? Or should I put more emphasis on the words "new
> implementations" and say that mine isn't a new implementations (we
> have had our IPv6 stack in the market for a while), so we should
> continue to support site-local addresses?

I would suggest dropping support.

> 
> We are going for a USGv6 certification and knowing the right thing to
> do from this expert community would very helpful. Any thoughts in
> this area or any pointers in this regard would be greatly
> appreciated.

If you are aiming for USGv6 certification and knowing how long equipment
is kept in such environments, I would lean towards playing it safe and
removing any special handling for the site-local prefix.  Otherwise, you
run the risk that someone may put your product in a network where, years
later, they start using FEC0:: in a non-site-local context.

Regards,
Brian

---

From: Timothy Winters <[email-masked]>
Date: Fri, 5 Nov 2010 18:28:45 -0400

Hi Brian,
	The current test specification is inline with your statements below.  We essentially have the device learn a site-local prefix and make sure it treats it as a run of the mill global address.

Regards,
Tim

On Nov 4, 2010, at 10:31 AM, Brian Haberman wrote:

> --------------------------------------------------------------------
> IETF IPv6 working group mailing list
> [email-masked]
> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> --------------------------------------------------------------------

---

From: Aleksi Suhonen <[email-masked]>
Date: Fri, 26 Nov 2010 12:36:22 +0200

Hi,

A bit late, but I wanted to contribute too ... :)

> It seems to clearly say that an IPv6 stack must no longer support site-local addresses, to be able to conform this RFC. So, would I be right in assuming that our stack should simply drop the suppor…

In my opinion, you should keep the code for site-local addresses, 
because it may come in handy with e.g. ULA addresses (fc00::/7). 
However, you shouldn't automatically detect fec0::/10 or anything else 
as site-local. For future and backward compatibility, you may want to 
have some ifconfig flag or other similar method for marking an address 
as site local scope.

Of course, modern thinking prefers usage of labels and/or preferences 
over scopes for proper address selection.

Just a couple of cents from,

-- 
	Aleksi Suhonen, Researcher
	Department of Communications Engineering
	Tampere University of Technology