I don't like saying that the client should just ignore all occurrences of
a duplicate CIDR. I think that if the server created a map with duplicate
CIDRs, the server has a major problem, and I wouldn't trust that server.
After all, even if a server automatically creates the network map from
network data, how hard would it be for the server to test for and remove
duplicates? Especially because we expect the client to be smart enough to
detect duplicates??
There's an old saying: If you add a teaspoon of excrement to a barrel of
fine wine, you have a barrel of excrement. If a network map has duplicate
CIDRs, I think that network map is junk.
- Wendy Roome
On 11/01/2013 15:13, "Sebastian Kiesel" <[email protected]> wrote:
>Dear all,
>
>
>Let's focus on IP prefixes in PID definitions as this has to be
>clarified before the protocol document can be finalized.
>In other words we are talking about section 5.2.1 of
>draft-ietf-alto-protocol-20.txt.
>
>
>it seems that we could not agree on a tiebreaker algorithm to be
>used by the client if it receives a network map defining multiple
>PIDs each containing the same IP prefix.
>
>
>
>Let me try to summarize with two examples:
>
>MapA: A1 = 10.0.0.0/15
> A2 = 10.0.0.0/16, 10.1.0.0/16
>
>is legal, and 10.0.0.1 should be in A2
>
>this is what follows from the current specification, though it may
>be surprising to some of us.
>
>
>MapB: B1 = 10.0.0.0/15
> B2 = 10.0.0.0/15, 192.168.0.0/16
>
>is NOT legal.
>
>
>
>So my proposal to move forward:
>
>1. clarify that this kind of map as in example B is illegal:
>
>In Sec. 5.2.1:
>
>Old:
>
> Each endpoint MUST map into exactly one PID. Since longest-prefix
> matching is used to map an endpoint to a PID, this can be
> accomplished by ensuring that no two PIDs contain an identical IP
> prefix.
>
>Replace with:
>
> A network map MUST NOT define two or more PIDs that contain
> an identical IP prefix, in order to ensure that the longest-prefix
>
> matching algorithm maps each endpoint into exactly one PID.
>
>
>
>
>2. optional: specify client behavior in this error condition
>
>Append a sentence at the end of 5.2.1.
>
> If an ALTO client receives an invalid network map defining two or
> more PIDs that contain an identical IP prefix, the ALTO client
> SHOULD ignore that prefix and behave as if the prefix did not occur
> in any PID definition.
>
>or:
>
> If an ALTO client receives an invalid network map defining two or
> more PIDs that contain an identical IP prefix, the ALTO client
> SHOULD completely ignore the complete network map.
>
>
>
>3. optional: add a clarification that example A above is legal and A2
>is the result.
>
>
>
>
>I think that we should add 1) and the first text proposal for 2).
>I don't think that we need 3) but I will not object if someone
>comes up with a good text proposal.
>
>
>
>Comments?
>
>Thanks
>Sebastian
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