Re: IPv6 address assignment for strictly point-to-point links and Device Loopbacks

Usman Latif <osmankh@yahoo.com> Thu, 27 September 2012 01:03 UTC

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Date: Wed, 26 Sep 2012 18:03:19 -0700 (PDT)
From: Usman Latif <osmankh@yahoo.com>
Subject: Re: IPv6 address assignment for strictly point-to-point links and Device Loopbacks
To: SM <sm@resistor.net>
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Hi,
 
I am still confused - And I'll try to explain my confusion.

While we can still go ahead and say recommendations on /127 that exist in section B.2.2 of RFC 5375 no longer hold true and the recommendations on /127 that exist in RFC 6164 prevail over 5375

The above is fine - but if you read RFC 5375 section B.2 in detail, it talks about all prefix lengths above /64 and encompasses /128 for loopbacks in its recommendations as well (section B.2.3) - whereas RFC 6164 does NOT talk about addressing for loopback interfaces at all

What is even more confusing is that if you consider the recommendations for /128 as per RFC 5375 as TRUE, then you go back into a loop thinking that there should be no discrimination between /127 or /128 because RFC 5375 talks about "overlap" and restricts / cautions us about reserved bits that should not be used for /128 assignments and uses the same recommendation for /127

Question: How can those reserved bits NOT be a problem for /127 assignments but a problem for /128 assignments?

This is why I think if (for whatever reason which I am still trying to digest) we have decided to use /127 without considering reserved bits for IEEE or other protocols, we need to provide similar or atleast some recommendations for /128 on loopbacks that sit inline with what we have recommended in RFC 6164 - otherwise the confusion still exists !!
 
I hope I am able to convey my confusion correctly... and this is shared by many peers in the industry that I have spoken to... hence the reason in practice although they are assigning /127 on p2p links, they are still reserving the whole parent /64 for each p2p link seperately......
 
 
Regards
Usman


--- On Thu, 27/9/12, SM <sm@resistor.net> wrote:


From: SM <sm@resistor.net>
Subject: Re: IPv6 address assignment for strictly point-to-point links and Device Loopbacks
To: "Usman Latif" <osmankh@yahoo.com>
Cc: ipv6@ietf.org
Received: Thursday, 27 September, 2012, 4:52 AM


Hi Usman,
At 17:08 26-09-2012, Usman Latif wrote:
> There is clearly two set of recommendations over the same addressing scenario which I am only trying to clarify with the IETF community.
> RFC 6164 has recommendations that do not encompass all the recommendations that were put forward in RFC 5375
> 
> So although when RFC 6547 moved the RFC 3627 to historical status, it completely ignored that RFC 5375 has additional recommendations for the same /127 and /128 addressing scenarios.
> 
> What I am now trying to clarify is - should we consider recommendations in RFC 5375 (section B.2) as obsolete ?

See http://www.ietf.org/mail-archive/web/v6ops/current/msg13685.html

Regards,
-sm