> Behalf Of Andrew Newton > If this is the source of the conflict, then BOTH experiments should > not use the v=spf1 records.
Which would at the same time provide an opportunity to address the one part of SPF/Sender-ID that does give me significant concern, the exclusive appropriation of the TXT record. A prefixed record would be much less likely to collide with other records. A proposal has been made to cut an new RR but as the group discovered 50% of the legacy infrastructure does not support new RRs despite claims to the contrary. Support in this case has to be production quality, not the ability to coax particular bits out of a server in certain limited circumstances that no network admi is ever going to accept on a production server. The main objection to prefixed records is that they do not work with wildcards. This is actually a failure of imagination rather than fact. It is quite possible to develop a resolution procedure for prefix records that works acceptably with legacy DNS resolvers and meets the needs of network admins. The first step is to address the problem that wildcards do not match an existing node. As was demonstrated on the list this is easily solved using a macro processor. The second step is how to create a wildcard for _prefix.*.example.com without changing legacy DNS servers. The way to do this is to introduce a pointer record using CNAME as follows: _prefix.exists.example.com TXT "Policy1" *.example.com CNAME _wildcard.example.com _prefix._wildcard.example.com TXT "Policy2" The resolution algorithm for domain X is: 1) Check for a TXT record for _prefix.X if it exists, return the TXT string and stop 2) Check for a CNAME at X, if it does not exist return 'NIL' and stop 3) Check for a TXT record for _prefix.Y where Y is the CNAME mapping. If it exists return the TXT string, otherwise stop. Applying these rules to the scheme above we get: Lookup ("exists.example.com", "prefix") = "Policy1" [cost 1 lookup] Lookup ("empty.example.com", "prefix") = "Policy2" [cost 3 lookups] Lookup ("empty.example.com", "noprefix") = NIL [cost 3 lookups] This algorithm is 100% compatible with the deployed, legacy DNS and meets all use cases that were proposed for wildcarding. It never takes more than three DNS lookups. The first two can be requested in parallel, an intelligent DNS server could return the CNAME as an additional record for optimization purposes. If this mechanism was adopted as policy for ALL prefixed records there would no longer be any need to define new RRs unless there was a need to define a new record syntax. It would also allow admins to manage their policy records much more effectively, the default node is treated as if it was just another node. If folk really want to argue over the SPF=1 issue I think that they are saying that the protocol is not really embedded enough to be beyond change. If that is the case I think that we should fix the problem caused by the exclusive appropriation of TXT. _______________________________________________ Ietf mailing list Ietf@ietf.org https://www1.ietf.org/mailman/listinfo/ietf