Date: Fri, 01 Feb 2013 00:44:47 +0100
From: Darren Reed <darrenr%netbsd.org@localhost>
Message-ID:
<1359675887.4682.140661185289761.2831F179%webmail.messagingengine.com@localhost>
| How do you determine a stable address vs temporary?
If you mean by that, how do I look at an address and determine if it
is a temporary address or not, the answer is, I can't - which is exactly
what (part of) the problem is.
Only when the address is created (or assigned) do we know its planned
use model - whoever (or whatever) creates the address needs to indicate
whether it is a temporary, or a stable address.
...
It is with IPv6 that we really need an addition (and then, as has happened
with other stuff originally designed for v6, if that turns out to be
beneficial to IPv4 as well, that's fine).
For IPv6, a temporary address is one assigned following the procedures
of RFC4941 - for this purpose the term "temporary address" is a very
specific thing, and doesn't just mean some random address that I might
not have forever.
The general assumption is that you will normally only use a temporary
address
for a very limited time - a day would be an upper limit, an hour is not
at all unreasonable. Then you make a new one and use that instead.
...
| If temporary is DHCP then both of my links are temporary.
It isn't, those are stable address, what you described was just address
renumbering (or perhaps, mobile IP, in some cases would be quite similar).
...
For the NFS application that started this, I have to have an address that
the NFS server will permit, so the only issue is making sure I use
that one
and not some other one (like some temporary address, as the problem that
inspired this discussion was caused by.)
| The argument that I'm making here is that I don't see
| temporary vs stable as being a useful abstraction in the
| classification of addresses for applications to use as there
| is no reasonable way to classify an address as such.
Of course there is - to use (4941) temporary addresses we need a process
running to create, monitor, and release them as appropriate (that can be
a daemon, a script run from cron, or ...) When it creates a temporary
address it simply says "this is a temporary address" and from that
point on
everyone knows that. When DHCP (or IPv6 autoconf, or manual ifconfig)
assign an address, they don't say that, and their address is a stable one.