It is smoothed RTT. Forwarders however have highly variable RTT as the records usually needs to be looked up from the authoritative servers so what you end up measuring is RTT + resolution time. RRsets expire at the same time on both the local caching server and the forwarders.
> On 21 Aug 2025, at 22:07, DEMBLANS Mathieu <demblan...@numihfrance.fr> wrote: > > Hello, > Anyone know how forwarder is choosen when there is several configured ? > Threads about this subject I found talk about RTT but we doesn’t observe > these. > It looks more like a round robin. > I have tested the response time of the forwarders, our 2 locals servers > respond in 2ms, the 2 others, that are remote, respond in 14ms but if I check > the DNS traffic between the NS requested and the forwarders contacted I have > a 26/26/23/23% repartition, 26% for remotes forwarders. > We use bind 9.18.24 > Any idea about how it should work? > -- > 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 -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: ma...@isc.org -- 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
