Thus spake "Keith Moore" <moore(_at_)cs(_dot_)utk(_dot_)edu>
And you're conflating ambiguous addressing with scoping.
nope. the property that I'm concerned about is not that an address
may only be usable within a particular portion of the network, it's
that the address is ambiguous.
As Mr. Hain pointed out, last week your argument was about scoping and
apps picking addresses, not about private addresses.
indeed, there are several arguments. ambiguity is the biggest problem,
but there are others. nor are they independent of one another - the
problems interrlate. having ambiguous addresses makes the address
selection problem more difficult, but the need to employ address
selection is a problem even if all addresses are global. also, when I've
been using the word "scoping" I've been talking about the scope in
which an address is defined (has a well-defined meaning) rather than the
scope in which an address could be used- I argue that we need globally
scoped addresses even if they can only be used within a limited portion
of the network.
so given an address there's no way to know whether or not it is
valid, or why it doesn't seem to work to let you connect with the
host/peer/server you think it's associated with.
You have no way of knowing if any address is reachable from any
particular location. That is not a property specific to private
addresses.
they're different. if you have a globally scoped address you can
try to send to it, and the network will make a best effort to get it
there, modulo policy. if it doesn't know how to get the packet there,
and the network "should" send an ICMP that explains the reason it can't
get there. and that address will reach the same location/host from any
point in the network.
if you have an ambiguous address you can try to send to it, but the
network can't tell where it's intended to go. to the extent that the
network tries to route it somewhere, it may not end up at the
location/host the sender intended, and there's no way for anyone to know
that the packet is being misrouted. if an error is returned it is
pretty much useless - either the host is down or the network interpreted
the address in a different scope that was intended or the sending host
picked the wrong interface.
note that if you had a globally unique address that only works within a
limited scope, it acts like any other globally scoped address.
Perhaps. There is no functional difference unless multiple
instances of the same address are actually _reachable_ by a third
party; the mere existence of duplicates does not change the
architecture.
wrong. it's useful to have unique names for hosts (or points on the
network) even if they're not directly reachable by everyone who
might possess those names.
Useful, yes; a fundamental part of the architecture, no.
disagree. the internet protocol fundamentally depends on addresses
being global - routing between arbitrarily connected IP networks cannot
work without this property. furthermore there are several deep
assumptions that IP addresses are uniquely assigned to hosts - for
instance, IP addresses are used as TCP endpoint identifiers, and
round-trip estimates are made on a per-host basis.
Removing private addresses from the IPv6 architecture is a fundamental
change from IPv4: site-locals are not a new addition, just a different
name.
False. IPv4 only had private addresses for use in isolated networks,
and this was a late addition, and we've learned from experience that
this was a mistake.
If site-locals are deprecated, the NAT/stable address/whatever crowd
will just pick a different prefix to use.
and the boogey man will come, and we'll all be attacked by terrorists
flying cessna 172s. sorry, but I'm sort of fed up with living in a
country that does its best to control its citizens through irrational
and ungrounded fear, all the while pretending that it's good for you and
ignoring the real problems that exist. I've got a pretty low tolerance
for such tactics these days.
yes, we have to give people good ways to solve real problems that they
have. no, we don't have to legitimize every bad idea that people have
put into practice merely because somebody is doing it.
Keith