Subject: Re: WG next steps

From: "J. Noel Chiappa" <[email-masked]>
Date: Mon, 18 Nov 2002 11:11:49 -0500

> From: Kurt Erik Lindqvist <[email-masked]>

    >> Do we think it is worthwhile to continue down the network/routing
    >> based solutions? The lack of feedback on my draft suggests people
    >> aren't very interested in working on this.

Oh, Iljitsch, I thought you got lots of feedback - but it was all of the form
"geographic addressing is a waste of time"! :-)

    >> If we want to do this at the routing level, we have start exploring
    >> less obvious stuff. For instance, using the flow label or diffserv
    >> code points to swim across the default zone towards a network that
    >> knows more specific routing information.

Just to prevent confusion, I wouldn't call that a "routing" solution (which,
to me, means having the routing mechanisms keep track of multi-homed sites).

I think it's better to call it an internetwork-layer solution, one which
uses a secondary "locator" in the packet header.

    > In the long run that will be the only thing that scales

It's not clear exactly what you're referring to when you say "that ...
scales", but I can see two possible axes for scaling. One is in the size of
a particular site which is multi-homed. The other is in the total number of
multi-homed sites in the network as a whole.

It's quite clear to most people that a routing-based solution (as defined
above) to the "total number" axis is definitely one that will *not* scale.

Can you expand on your comment a little, using this more precise
terminology? Did you mean "an internetwork-layer solution to the total
number scaling"?

	Noel

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From: Iljitsch van Beijnum <[email-masked]>
Date: Mon, 18 Nov 2002 19:47:52 +0100 (CET)

> "geographic addressing is a waste of time"! :-)

That's like objecting to the film Star Wars by objecting "the stars are
not at war!" and then refuse to see the flick...

> uses a secondary "locator" in the packet header.

Didn't some dead English guy four odd centuries ago have something to
say about the relative value of naming schemes?

Actually I wouldn't necessarily want to include a second full locator.
The extra field could/would be used to rearrange the IPv6 address in
such a way that the top of the aggregation tree is moved to another
place. Using this it should be possible to kind of select a new
hierarchy rather than make sure the one you end up with always works.
(I'm not saying I'm 100% convinced this can work, though, but if we can
borrow a header field we can see how far we can come.)

> It's not clear exactly what you're referring to when you say "that ...

I didn't say this. On the contrarry, I'm convinced that routing can only
scale if we allow people to be present in two or more places in the
hierarchy only when those places are relatively close together. (See
GAPI. There you must connect to ISPs within the same
country/state/province.) Note also that current IPv6 address allocation
mechanisms aren't hierarchical so they should be considered
non-scalable. We can see this in the v4 global routing table which is
110k entries big, while the number of multihomers can't be much more
than 10k. In v6 we have a one time gain and the growth curve will be
slightly flatter, but no fundamental differences.

I was reading the Kleinrock/Kamoun paper by the way, but it doesn't
apply very directly to what we're trying to do here. One of the most
problematic assumptions they make is that there is a single network. In
reality, we're dealing with many networks, and shifting traffic from one
to the other because information is lost in aggregation is not something
we can simply do because it makes engineering sense.

Iljitsch

---

From: Andrew Partan <[email-masked]>
Date: Mon, 18 Nov 2002 14:06:43 -0500

On Mon, Nov 18, 2002 at 07:47:52PM +0100, Iljitsch van Beijnum wrote:
> > Oh, Iljitsch, I thought you got lots of feedback - but it was all of the
> > form "geographic addressing is a waste of time"! :-)
> 

Do you argue about the potential of perpetual motion machines?
	--asp

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Mon, 18 Nov 2002 20:45:33 +0100 (CET)

> Do you argue about the potential of perpetual motion machines?

No, I just argue that geo aggregation isn't perpetual motion.

It's very simple. If you use a hierarchical addressing mechanism, you
get to aggregate. If you aggregate, traffic flows become less optimal.
Making the hierarchy geographically relevant gives you the _potential_
to get around the traffic flow problem. That's all. No creative physics.

---

From: Andrew Partan <[email-masked]>
Date: Mon, 18 Nov 2002 14:51:28 -0500

> to get around the traffic flow problem. That's all. No creative physics.

I'll try to explain this again.

I'm a large provider; I'm connected to two geo areas - A and B.
Not everyone in area A is my customer.
At B I connect to another provider.
What routes to I announce to that other provider about area A?
If I announce just my customers' routes, then aggregation is dead.
If I announce just the area A aggregate, then I am giving free transit
to everyone in area A.
Neither one flys.

You have the smae problem with exchange addressing as well.
	--asp

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Mon, 18 Nov 2002 22:09:18 +0100 (CET)

> If I announce just the area A aggregate, then I am giving free transit

You announce your customers. You don't get to aggregate those. However,
you only accept routes for people in the A and B regions from your
peers. If you have a packet for someone in region C you route it towards
the router inside your network that has information about region C.
Conversely, in region C there are only aggregates towards A and B in the
routing tables.

This limits the aggregation to how many routers with good
interconnection you have, but not necessarily to the number of
interconnect locations = you can solve the scalability problem by
throwing hardware at it, which is not great but still much, much better
than not being able to solve it at all, so I think it is a reasonable
short term solution.

---

From: Andrew Partan <[email-masked]>
Date: Mon, 18 Nov 2002 16:55:08 -0500

> Conversely, in region C there are only aggregates towards A and B in the

Then who is providing the free transit for A and B in region C?
	--asp