Noel Chiappa allegedly wrote on 04 09 2009 8:18 PM: > > From: William Herrin <[email protected]> > > > If its practical for anycast to be an integral part of unicast routing > > then it's likely to be suboptimal or even destructive to architect it > > as a peer to unicast routing. > > Anycast 'addresses' are service names. What we are doing, then, is using the > routing to route to service names.
Assuming you are right that anycast addresses are service names (see below) you are using service names as forwarding selectors. We do that with deep packet inspection too for example. > This might be seen as good in the short term, but this kind of mixing of > fundamentally different functions in one mechanism is exactly the kind of > thing that, in the long run, can be a problem. It is not mixing different functions. There is a big difference between what forwarding uses and point of attachment names. Forwarding can use anything, and does (not all of it in the packets). Granted it is placing the service name in a field where one traditionally finds addresses, but no actual functions are mixed. Forwarding does what it always does. The service names cleverly look like addresses. But all that assumes anycast addresses are "service names". I want to get back to the question of whether anycast addresses are locators. Joel and I had a short phone call, and here's the example I used: - Suppose I have a little network and I advertise a route to it on the Internet. Are the names for points of attachment of the nodes on my network locators? Yes (I hope you say). - Now suppose Joel accidentally misconfigures a few things and ends up configuring exactly the same prefix for his little network, and advertising a route to it. I haven't changed anything. Are the names for the points of attachment on my network still locators, or are they just "service names"? Joel suggested that the architecture shouldn't have to handle misconfigurations, but it's deeper than that. Someone making a mistake does not change the essential nature of things in the architecture. A suggestion for a fundamental principle: If an architectural component is fundamental, what someone does with it doesn't change what it is. So I ask you: if I had locators to start with, why wouldn't I still have locators after someone else claims to have them as well? If the answer is that I still do, how is that different from anycast? Scott _______________________________________________ rrg mailing list [email protected] http://www.irtf.org/mailman/listinfo/rrg
