On Thu, May 30, 2013 at 2:17 PM, Casey Deccio <casey@deccio.net> wrote:
On Thu, May 30, 2013 at 9:22 AM, Yunhong Gu <guu@google.com> wrote:
Google resolvers got no response (i.e. timeout) for ipp.gov/dnskey from its authoritative name servers. If there is anyone on this list who manages ipp.gov DNS servers, please take a look. Our resolver IPs can be found at https://developers.google.com/speed/public-dns/faq#locations.
I get a response for DNSKEY just fine*. However, the payload of the response is 1279 bytes, and Google's resolvers set the maximum UDP receive payload to 1232, which results in the truncated response. Unfortunately, the ipp.gov servers don't respond over TCP, so the resolvers aren't able to retrieve ipp.gov/DNSKEY.
Thanks, I suspected this problem but tried to verify using a wrong buffer size by mistake.
The problem here is that the ipp.gov servers aren't responding on TCP/53. But of curiosity, why a max payload size of 1232 for the Google resolvers? It seems like that would result in a lot more TCP transactions (and overhead) for queries to signed zones.
There is still chance for fragmented UDP responses to get dropped nowadays, so we want response in single UDP packets or otherwise from TCP. Overhead should be insignificant due to the cache in resolvers. That being said, we are testing 4k max UDP buffer and may turn it on in the near future.
Casey
* Although, that's only if the DO bit is set; interestingly, if I don't set the DO bit, the response times out.