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Re: RFC 6724
- From: Phillip Hellewell <sshock at gmail dot com>
- To: libc-help at sourceware dot org
- Date: Sun, 11 Nov 2018 14:08:30 -0700
- Subject: Re: RFC 6724
- References: <CA+dWQFo-rHBGgAtBR54AHpj2mk5aG==2kmWrL7RuYD_KqAuSSA@mail.gmail.com>
Here are the policy tables for comparison:
RFC 3484:
Prefix Precedence Label
::1/128 50 0
::/0 40 1
2002::/16 30 2
::/96 20 3
::ffff:0:0/96 10 4
RFC 6724:
Prefix Precedence Label
::1/128 50 0
::/0 40 1
::ffff:0:0/96 35 4
2002::/16 30 2
2001::/32 5 5
fc00::/7 3 13
::/96 1 3
fec0::/10 1 11
3ffe::/16 1 12
In general, what you are seeing is a depreference for
old/obsolete/unreliable ipv6 prefixes such as Teredo, site-local,
6to4, 6bone, etc.
The changes look good and make sense to me, except for one minor tweak
I would suggest. The rule for fc00::/7 was added so that global IPv6
would be preferred over ULAs. That makes sense, but as you can see it
has also been placed below IPv4 (::ffff:0:0/96). This also makes
sense if we are talking about a global IPv4 being preferred over a
(local) ULA IPv6. However, if choosing between a private IPv4 (10/8,
172.16/12, 192.168/16) or a ULA IPv6, they have the same scope so the
IPv6 address ought to be preferred. To solve this, I would add in
three rules for the private IPv4 prefixes with a precedence of 2, so
that ULA will be preferred over them.
Phillip