[dns-operations] Full-service resolver - Pending Upstream Query behaviour

[Peter van Dijk]

On Tue, 2021-10-05 at 11:04 -0700, Paul Vixie wrote:
> was cache miss deduplication by q-tuple ever standardized? it is a nec'y part of kaminsky resistance and so ought to be part of whatever BCP corpus comes about. pending upstream query behaviour would be an expansion on cache miss dedup by q-tuple, such that a rising tide of timeouts would yield probabilistic prediction of servfail for cache misses aimed at the affected <zone,auth>.

https://datatracker.ietf.org/doc/html/rfc5452#section-5 describes the
problem, without prescribing a solution.

PowerDNS Recursor performs 'query chaining' to prevent those duplicate
queries. It is not described in the docs outside of this small phrase: 
https://doc.powerdns.com/recursor/metrics.html?highlight=chaining#chain-resends

Kind regards,
-- 
Peter van Dijk
PowerDNS.COM BV - https://www.powerdns.com/