Real-time media applications create a communication path for the signaling information that announces and establishes the communiation, and a separate path or paths for the associated media. The presence of Network Address Translators (NATs) and firewalls can sometimes block the media with the result that end-users experience one-way audio and/or video. The NTAP testbed was designed to discover the network configurations that block the media and to characterize the nature of the blockage (one-way audio vs. failure to establish the call for example), and the conditions under which the failure occurs. The testbed provided a hierarchy of nested networks and subnetworks on which SIP and HTML clients and servers are distributed. STUN and TURN servers as well as firewalls can be placed in various positions on the network as well. A test matrix describing various locations for the network elements wasa created and tests were done to identify and characterize the failure scenarios. The nest steps for this project are to automate the testing, and expand the network using NFV and SDN technologies.