Re: [6lowpan] Fwd: Re: which addresses can be registered?

Erik Nordmark <nordmark@acm.org> Fri, 15 April 2011 00:05 UTC

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Date: Thu, 14 Apr 2011 17:05:58 -0700
From: Erik Nordmark <nordmark@acm.org>
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To: Richard Kelsey <richard.kelsey@ember.com>
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Subject: Re: [6lowpan] Fwd: Re: which addresses can be registered?
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On 4/14/11 4:56 PM, Richard Kelsey wrote:
> Thank you.  The question arose with respect to link-local
> addresses derived from IEEE 802.15.4 16-bit short addresses,
> which require some form of DAD.

To me it makes sense to register those.
But one could also have link-locals based on EUI-64 and only have the 
globals use the short addresses.
But as I said, the spec provides some flexibility here.

> Just to be clear, if there are two 6LBRs which advertise
> different prefixes and a host configures addresses for
> both prefixes, then both addresses need to be registered
> with both 6LBRs?

Both addresses need to be registered for sure. IPv6 checks for duplicate 
addresses and not duplicate interface IDs (there was a debate and a 
change/clarification in this area in the early days of IPv6.)

Ideally the 6LBRs are coordinated so that they both advertise both 
prefixes. That seems to be natural if we want one 6LBR to take over 
should the other one fail. But I assume that even if they don't 
advertise the same prefixes, it makes sense to register with both.

    Erik