Question: When a PSS (Packet-switched Streaming Service) Client detects a NAT (Network Address Translation), which of the following NAT traversal procedures relies on initiating UDP port opening by sending specific packets after port pairs are negotiated but before streaming starts?
Option 1: UPnP (Universal Plug and Play)
Option 2: SP/P Interleaving over a single TCP connection
Option 3: Punching through sending P packet and CP report on negotiated port pairs
Option 4: RTP over TCP using separate connections for P transport
Explanation: The correct answer is "Punching through sending P packet and CP report on negotiated port pairs" because this method specifically involves the client initiating NAT routing by "punching" (opening) UDP ports. This is achieved by sending a P packet on the P port pair and a CP report on the CP port pair after negotiation but before streaming begins, fitting the described scenario. UPnP may not always be available, SP/P Interleaving involves interleaving data over a single TCP connection, and RTP over TCP uses separate TCP connections for transport, which do not match the described method of initiating UDP port opening through packet sending.