DNS depends on extensive caching for good performance, and every DNS zone owner must set Time-to-Live (TTL) values to control their DNS caching. Today there is relatively little guidance backed by research about how to set TTLs, and op- erators must balance conflicting demands of caching against agility of configuration. Exactly how TTL value choices affect operational networks is quite challenging to understand for several reasons: DNS is a distributed service, DNS resolu- tion is security-sensitive, and resolvers require multiple types of information as they traverse the DNS hierarchy. These complications mean there are multiple frequently interacting, places TTLs can be specified. This paper provides the first careful evaluation of how these factors affect the effective cache lifetimes of DNS records, and provides recommenda- tions for how to configure DNS TTLs based on our findings. We provide recommendations in TTL choice for different situations, and for where they must be configured. We show that longer TTLs have significant promise, reducing median latency from 183 ms to 28.7 ms for one country-code TLD.
|Talk Duration||Lightning Talk 10 Minutes|