RCDS promotes efficient use of the network by providing a lightweight protocol for queries and updates. In most cases, the resolution process is expected to cost one extra long-distance round-trip (to an RCDS server), and one extra local round-trip (to a SONAR server), as compared to the name-to-address lookup for a URL. The benefit is that the client can then choose to access the resource from a nearby server (rather than the one explicitly listed in a URL); the client can also avoid fetching the resource at all if it can tell by the catalog record that it is not needed, or (using the LIFN as a cache validator) that a locally-cached copy exists. Finally, because RCDS allows listing of multiple URLs for a resource, it allows the client to choose not only a nearby server, but also the best access protocol that it supports. RCDS thus provides a means to transition from ftp and http to more efficient protocols; for instance, streaming protocols for real-time audio and video, or multicast-based protocols for information which is transmitted simultaneously to many users.