Re: negative caching ttl question
Thank you, Tony. You're right. I do see a difference in behavior when querying other authoritative, non-AWS servers. I didn't realize it was the job of the authoritative server to do the math and present the proper ttl. Thanks for the pointer to the relevant section in the rfc. Slava On Tue, Oct 13, 2020 at 1:34 PM Tony Finch wrote: > > Veaceslav Revutchi wrote: > > > Given this soa: > > > > fe80.info. 3600 IN SOA ns-538.awsdns-03.net. > > awsdns-hostmaster.amazon.com. 1 7200 900 1209600 60 > > > > I see bind caching negative answers for 3600 instead of 60. The rfc > > and my google searches suggest that it should pick the MIN(soa ttl, > > soa min ttl) for that purpose. What am I missing? > > I think what RFC 2308 says (sections 3 and 5) the authoritative server for > the zone is responsible for calculating the negative TTL from the minimum > of the SOA TTL and MINIMUM fields. Sections 5 and 6 say that resolvers and > caches propagate the negative TTL using just the TTL field of the SOA in > the AUTHORITY section of the response (though the RFC could be a little > more explicit about this). > > What's happening for fe80.info is the AWS DNS authoritative servers are > setting the wrong TTL in the negative response, and your BIND cache is > doing what it is told to do. > > Tony. > -- > f.anthony.n.finchhttp://dotat.at/ > Ardnamurchan Point to Cape Wrath: Northeast 5 or 6, veering east 3 or 4 later. > Rough becoming moderate. Showers. Good, occasionally moderate. ___ Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list ISC funds the development of this software with paid support subscriptions. Contact us at https://www.isc.org/contact/ for more information. bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
Re: negative caching ttl question
Veaceslav Revutchi wrote: > Given this soa: > > fe80.info. 3600 IN SOA ns-538.awsdns-03.net. > awsdns-hostmaster.amazon.com. 1 7200 900 1209600 60 > > I see bind caching negative answers for 3600 instead of 60. The rfc > and my google searches suggest that it should pick the MIN(soa ttl, > soa min ttl) for that purpose. What am I missing? I think what RFC 2308 says (sections 3 and 5) the authoritative server for the zone is responsible for calculating the negative TTL from the minimum of the SOA TTL and MINIMUM fields. Sections 5 and 6 say that resolvers and caches propagate the negative TTL using just the TTL field of the SOA in the AUTHORITY section of the response (though the RFC could be a little more explicit about this). What's happening for fe80.info is the AWS DNS authoritative servers are setting the wrong TTL in the negative response, and your BIND cache is doing what it is told to do. Tony. -- f.anthony.n.finchhttp://dotat.at/ Ardnamurchan Point to Cape Wrath: Northeast 5 or 6, veering east 3 or 4 later. Rough becoming moderate. Showers. Good, occasionally moderate. ___ Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list ISC funds the development of this software with paid support subscriptions. Contact us at https://www.isc.org/contact/ for more information. bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
negative caching ttl question
Given this soa: fe80.info. 3600 IN SOA ns-538.awsdns-03.net. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 60 I see bind caching negative answers for 3600 instead of 60. The rfc and my google searches suggest that it should pick the MIN(soa ttl, soa min ttl) for that purpose. What am I missing? Thank you, Slava ___ Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list ISC funds the development of this software with paid support subscriptions. Contact us at https://www.isc.org/contact/ for more information. bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
