Hi Wendy, On Thu, Oct 24, 2013 at 1:39 PM, Wendy Roome <[email protected]>wrote:
> 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. > Agree, and can do so with the example that you proposed, at least to those who find it less intuitive. Richard > > - 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 >> A2 = 10.0.0.0/15 >> >> MapB: B1 = 10.0.0.0/16, 10.1.0.0/16, 10.2.0.0/16, 10.3.0.0/16 >> B2 = 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. >
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