ipv6 addressing - non-routable equivalents?

[Jonathan Guthrie]

On Thu, 5 Oct 2000, Antonio Querubin wrote:

> On Thu, 5 Oct 2000, Jonathan Guthrie wrote:
 
> > Yes, ::1 is a perfectly fine interface identifier, and I make use but it's
> > not a GLOBAL interface identifier.  That is, interface identifiers with
> > the global bit set are guaranteed to be unique on the Internet.  Perhaps
> > my terminology is incorrect, but unless I can put multiple globally-unique
> > interface identifiers on the same box, an awful lot of the magic IPv6
> > promises simply isn't there.
 
> I'm not sure what this really buys us.  So it's globally unique, ok.  We
> already had that with IPv4 - though it wasn't 'guaranteed' to be unique.
> But where's the 'magic'?

The "magic", oddly enough, is contained in the part that isn't unique.
What makes the scheme work is the fact that the routing information is
embedded in the prefix.  IPv4 addresses aren't long enough for that to
happen.  What that means is that you can send a packet to a particular
destination one way by using one address and another way by using a
different address.  That means that to achieve multihoming, all you have
to do is make the 

> > The thing is, the Internet is NOT stupid with respect to routing.  In
> > order to do anything more complicated than a single nonredundant
> > connection, you have to have your equipment interact with the routing
> > structure of the Internet.  One of the most common questions on the Zebra
> > (a freeware routing protocol package) is "I've got two connections to the
> > Internet at my house from different providers, can I use Zebra to help me
> > use both of them at the same time?"  The answer, of course, is "no"
> > because multihoming requires (in principle and usually in practice) that
> > the entire Internet understand that routes through both providers are
> > equally valid for the addresses in question.
> > 
> > Globally-unique interface identifiers gives us a chance to change that.
> > 
> > With globally-unique interface identifiers, it becomes possible for the
> > software at the endpoints to determine that multiple routing options exist
> > and to exercise their own control over what routes a packet take.  The
> > rest of the Internet can simply take the attitude that the routing
> > structure is a tree and pass the packets along, fat, dumb, and happy.
 
> How so?  How does a globally unique IPv6 address provide this capability
> that a globally unique IPv4 address does not?

I'm not talking about a globally unique IPv6 ADDRESS, I'm talking about a
globally unique bottom 64 bits.  If you can guarantee that the bottom 
64 bits are unique, then you can tell if two different IPv6 addresses 
(which ARE going to be globally unique, just like IPv4 addresses) are
really from the same computer. There is no equivalent to this in
IPv4.  There is nothing even close to this in IPv4.

> > I believe that many people will want to have multiple globally-unique
> > interface identifiers on the same computer.  Is there a standard way of
> > doing this?
 
> The most common way hosting sites assign multiple addresses is to just
> number them sequentially.  It's pretty simple and mindless and doesn't
> require knowledge of the ethernet address on any NIC card.  Ie. it's KISS
> compliant :)

Since you don't understand what a globally-unique interface identifier IS
and how it's different from a globally-unique address, you probably won't
understand why what you describe is not particularly useful, with respect
to easy multihoming.
-- 
Jonathan Guthrie (jguthrie@brokersys.com)
Brokersys  +281-580-3358   http://www.brokersys.com/
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