Root zone TTLs have not changed since 1999. In this report, the RSSAC Caucus studies the extent to which the current root zone TTLs are still appropriate for today’s Internet environment. Selecting a TTL for a given resource record involves finding the right balance between a few tradeoffs. Intuitively, shorter TTLs are beneficial for data that changes frequently, whereas longer TTLs are beneficial for data that is relatively stable. Related to this, longer TTLs provide robustness in the event of operational failures. All other things being equal, and assuming software involved in queries and responses follow the DNS protocol standards, shorter TTLs generally result in higher query rates, and longer TTLs result in lower query rates.