Session Border Controllers (SBCs) are becoming an important part of the Internet infrastructure. Some of these Session Border Controllers are being split into Media Gateway Controller (MGC) and Media Gateway (MG) components. One important function of a SBC is to perform Network Address and Port Translation (NAPT). This Recommendation allows the MGC to instruct an MG to latch to an address provided by an incoming Internet Protocol (IP) application data stream rather than the address provided by the call/bearer control. This enables the MG to open a pinhole for data flow.