An improvement in the design and operation of telecommunications networks is described in which when a caller's telecommunication terminal does not know the address of the called party's telecommunications terminal, the caller's telecommunication terminal contacts one Session Initiation Protocol Proxy server after another until the address of the called party's telecommunications terminal is found. Thereafter, one or more of the Session Initiation Protocol Proxy servers that did not have the address of the called party's telecommunications terminal are populated with that information for future use.