A client player performs a query to a nameserver against a network map of Internet traffic conditions. The query is made asking for a particular service (e.g., RTSP) via a particular protocol (TCP) in a particular domain. In response, the nameserver returns a set of one or more tokens, with each token defining a machine or, in the preferred embodiment, a group of machines, from which the player should seek to obtain the stream. The player may then optionally perform one or more tests to determine which of a set of servers provides a best quality of service for the stream. That server is then used to retrieve the stream. Periodically, the client player code repeats the query during stream playback to determine whether there is a better source for the stream. If a better source exists, the player performs a switch to the better stream source "on the fly" if appropriate to maintain and/or enhance the quality of service. Preferably, the client player publishes data identifying why it selected a particular server, and such data may be used to augment the network map used for subsequent request routing determinations.