I think the protocol document should have an explicit example, such as "MapB", as well as giving Richard's algorithm.
Case in point: Two years ago, when I first started working on an ALTO server, I implemented the algorithm Richard described, exactly as is. For "MapB", my server does indeed say that 10.0.0.0 is in B1, not B2. And until I tried that test case, I had no idea it would behave that way. I really thought it would say 10.0.0.0 is in B2. So I think we need to hit people over the head with this one. - Wendy Roome From: "Y. Richard Yang" <[email protected]> Date: Thu, October 24, 2013 11:47 To: Wendy Roome <[email protected]> Cc: Sebastian Kiesel <[email protected]>, IETF ALTO <[email protected]> Subject: Re: [alto] Problem with "longest prefix" rule for mapping endpoints to PIDs > Here's the problem I saw. Consider two network maps: > >> MapA: A1 = 10.0.0.0/14 <http://10.0.0.0/14> >> A2 = 10.0.0.0/15 <http://10.0.0.0/15> >> >> MapB: B1 = 10.0.0.0/16 <http://10.0.0.0/16> , 10.1.0.0/16 >> <http://10.1.0.0/16> , 10.2.0.0/16 <http://10.2.0.0/16> , 10.3.0.0/16 >> <http://10.3.0.0/16> >> B2 = 10.0.0.0/15 <http://10.0.0.0/15> >> > PIDs A1 and B1 cover exactly the same set of endpoint addresses. So the naïve > view is that those two network maps are dentical. > > But if we strictly apply the "longest prefix match" rule, they are NOT > identical. > In MapA, 10.0.0.0 is in A2, while in MapB, it's in B1. To me, that's > counterintuitive. If y'all like that, fine. I can live with that! But it > should be documented, because I think this has serious potential for > misinterpretation. Yes. We should document it clearly in the document. The semantics is that: (1) No prefix should belong to two PIDs.; (2) One obtains the union of all prefixes defined by all PIDs; call this set of prefixes P; (3) The longest prefix matching an IP address is identified in P. (4) The PID containing the prefixed identified in (3) is the PID of the IP address.
_______________________________________________ alto mailing list [email protected] https://www.ietf.org/mailman/listinfo/alto
