the to address represents user station b a session description protocol sdp portion contains the network address and port that the destination node or station is to send media packets to once the call is established sdp is described in rfc 2327 entitled u201c sdp session description protocol u201d dated april 1998 in the example the network address is 47 1 1 1 and the port number is 1000 the combination of the network address and port is represented as 47 1 1 1 1000 the flag rtp rtcp indicates that the specified network address and port is the network address and port for receiving media packets more generally the originating network address and port for user station a is referred to as a media the address and port of user station a for communicating media packets once the application server 42 receives the invite message it performs a location query on the to address and determines that user station b is in the same domain xxx com as user station a b is then identified as a valid address the location query can be performed using data in the database server 48 next the application server 42 sends a request at 302 to the media portal 44 to allocate napt resources for performing a network address and port translation of media packets in the requested call session in one.