Hi Geoff, >Dunno how much all this helps the world other than illustrate (a) that >AS-based routing is probably too coarse and you may want a finer level >of granularity in terms of division of forwarding elements and (b) all >of this is well covered ground.
I think AS-based routing does not necessarily imply that we have to use just a locator per AS, but the locators' structure will have to be based on the AS number. (I will use 2-byte AS numbers to better explain this). Let's suppose we want to send traffic to a server A having an IP address within the "identifier prefix" of a stub AS connected to a transit provider whose ASN=1. Let's also suppose that we use the "locator prefix" 240.0.1.0/24 to send tunneled traffic towards AS1 (second and third bytes are the AS number). It means that the outer IP address would be 240.0.1.0. For server B having an IP address in a different "identifier prefix", AS1 could announce a second "locator prefix", for example 240.0.1.128/25, so that traffic sent to server B would be tunneled with the outer IP address 240.0.1.128. And AS1 would announce these two "locator prefixes", namely 240.0.1.0/24 and 240.0.1.128/25, in different ways to the rest of the Internet. And this exercise can be made finer and finer so that an "identifier prefix" could be assigned a "locator prefix" such as 240.0.1.77/32. Therefore AS-based routing can be used with a very fine level of granularity I think. Regards, Juanjo -----
