Other types of resolver are multipole resolvers. Archive.today currently blocks requests from Cloudflare's recursive DNS resolver, 1.1.1.1. The client side of the DNS is called a DNS resolver. A validating stub resolver uses the CD bit to perform its own recursive authentication. Users generally do not communicate directly with a DNS resolver. Some resolver implementations use TCP for all queries. Cloudflare runs an authoritative DNS resolver with a network of over 20 million Internet properties. A URN resolver resolves those URNs to GML CRS definitions. Initial launch with support for list-based blocking as a public DNS resolver. CleanBrowsing is a free public DNS resolver with content filtering, founded by Daniel B. Cid. DNF uses libsolv, an external dependency resolver. About half of these clients were using Google's public DNS resolver. SFX was the first OpenURL link resolver or link server. DNSCurve is intended to secure communication between a resolver and an authoritative server. This is not to be confused with the "root.hints" file used to bootstrap a resolver.