Thanks for the information. It seems to me that the comparison on failures between TCP and UDP make no sense at this moment. Davey 发件人: ripe-atlas [mailto:ripe-atlas-bounces@ripe.net] 代表 Tom 发送时间: 2017年5月9日 16:33 收件人: ripe-atlas@ripe.net 主题: Re: [atlas] Many timeout-failures for DNS over TCP For reference, it still appears on https://atlas.ripe.net/ for me - Tom May 9, 2017 9:14 AM, w.b.devries@utwente.nl wrote: Hi Davey, There used to be a message on the atlas.ripe.net frontpage, I retrieved it from google cache: Due to an unfortunate bug in a recent probe firmware (version 4760), TCP based DNS measurements are not providing correct results. This affects all ongoing and one-off measurements. The issue also affected DNSMON measurements between 14-23 March. On 23 March we deployed a corrected firmware on RIPE Atlas anchors (version 4770), and in the near future we'll deploy it on regular probes as well. Our excuses for the inconvenience caused! So any probe that is still on version 4760 will provide timeouts for TCP DNS lookups. Cheers, Wouter _____ From: ripe-atlas <ripe-atlas-bounces@ripe.net> on behalf of Davey Song($BAWNS7r(B) <ljsong@biigroup.cn> Sent: Tuesday, May 9, 2017 10:03 AM To: ripe-atlas@ripe.net Subject: [atlas] Many timeout-failures for DNS over TCP Hi folks, I setup measurements for DNS queries over both TCP and UDP. I found the timeout and failures of TCP is far more than UDP. For example : DNS over TCP: https://atlas.ripe.net/measurements/8552847/#!probes DNS over UDP: https://atlas.ripe.net/measurements/8552846/#!probes Is it normal ? I mean is there any special timeout routine/parameters of atlas probes from normal resolver? Best regards, Davey