[AusNOG] Write up - Big ISP, little ISP, local internet exchanges

[Edwin Groothuis]

On Tue, Sep 09, 2008 at 08:55:05AM +0930, Matthew Moyle-Croft wrote:
> >Up to now people only say that it is a tricky implementation (which it 
> >is), but nobody who has
> >said that the approach wasn't going to work.
> I guess I look at it like this:  if you can't think of a clever, 
> reliable and robust way of filtering out the traffic for the current 
> model then how does adding extra layers, complexity and latency allow 
> you to do any better?   You'll still need to be able to do the same 
> filtering, in the same way on the same kind of routers in your model, so 
> you don't seem to have improved things by adding the complexity.
> 
> ie. how would I solve the /22 into transit, /24 more specifics via MLPA 
> any better in your model?   What extra control and nerd knobs do I get?

The model was that there were two or three routing clouds: An users
and services cloud, and transit network cloud. The goal is to have
the /22s are known in the transit cloud, the /24s are known in the
services cloud.

On the border between the transit cloud and the services cloud you
exchange all routing information into the services cloud, but only
the routing information from the IP space from the services cloud
gets exchanged into the transit cloud.

On the border between the services cloud and the local internet
exchange, you only advertise the IP space of the services cloud.

On the border between the transit cloud and the local internet
exchange, you do nothing because that border doesn't exist.

> The issue of MLPAs breaking the usual "we won't peer with customers" 
> practise (and clearly for good reason) is a commercial issue not a 
> technical one - so the solution maybe more commercial than technical but 
> with some careful monitoring of what we're seeing?

The problem is a pure commercial one: When the big ISP connects to
a local internet exchange, it will lose revenue because data for
customers which use them as for transmit might go for free via the
local internet exchange and not via the links the customer paid
for. And when it doesn't connect to a local internet exchange,
people will tag that big ISP as less favourable.

The solution is a pure technical one: adjust the network to reflect
what you are offering. Or say you are offering. Or what you said
you were going to be offering.

Edwin
-- 
Edwin Groothuis      |            Personal website: http://www.mavetju.org
edwin at mavetju.org    |              Weblog: http://www.mavetju.org/weblog/