> On 29 Jul 2021, at 10:33 am, Mark Delany <m...@india.emu.st> wrote: > > On 29Jul21, Geoff Huston allegedly wrote: > >> For me it appears to depend on the actions of the resolver as to whether >> this would be faster >> or not. If all resolvers blindly re-query using TCP for all UDP responses >> where TC=1 is seen in > > I'm not sure I follow this bit. Are you merely implying that the resolver > should first > consider a larger edns0 bufsize before resorting to TCP?
Seems that the DNS Flag Day 2020 precluded that option, so I don’t think its available. > > Or are you suggesting that responses with TC=1 should include as much of the > answers as > will fit and then the resolver can decide whether enough is enough? Well no. Because RFC2181 says "When a DNS client receives a reply with TC set, it should ignore that response, and query again, using a mechanism, such as a TCP connection, that will permit larger replies.”, which, unless there is some later RFC that quietly countermanded this directive then I don't think the resolver has a choice here. (digression into the interpretation of the term “should” in a document that pre-dates normative language. Is that “should” used then in the way we use MUST today? Or is that a SHOULD? I interpreted it as a MUST but as I don't write resolver code for a living or as a hobby (and you should all be thankful for that!) I'm definitely not an authoritative sources as to how resolvers SHOULD or MUST interpret TC=1 responses. Geoff _______________________________________________ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
