ULA clashes don't matter [Re: ULA Registration]

Brian E Carpenter <brian.e.carpenter@gmail.com> Fri, 24 March 2017 18:37 UTC

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Subject: ULA clashes don't matter [Re: ULA Registration]
To: ipv6@ietf.org
References: <CAN-Dau132Jg0SsRjgcrxzGfbUEx_KPES9wMgDMg_++-zwY+0dw@mail.gmail.com> <7c4412a4-6494-961d-165b-9c5d267015a7@gmail.com> <39db830bd4d04faca308c01d0d39b8ae@XCH15-06-11.nw.nos.boeing.com>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
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Date: Sat, 25 Mar 2017 07:37:31 +1300
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Do I need to justify that? Oh, OK:

1. In the highly unlikely event of two networks merging (i.e. installing
round-the-back private routing between them) and discovering that they
are using the same pseudo-random ULA prefix: yes, they will be put to
a little bother. But this is so unlikely that it really isn't worth any
overhead to avoid it - and it would only be avoidable if at least of the
two networks had bothered to register their prefix.

2. In the rather more likely event of two networks merging and discovering
that they are using the same non-random ULA prefix (fd00::/48 probably),
it's their own silly fault.

3. In the somewhat likely event of a ULA prefix being announced in BGP4,
we will know who's announcing it, so we don't need a registry. And everybody
else will filter it anyway.

Regards
   Brian