This chapter describes the Real-Time Transport Protocol media loopback-support in Session Description Protocol (SDP) specified in RFC (Request for Comments) 6849. The wide deployment of Voice-over IP (VoIP), real-time text, and Video-over IP services has introduced new challenges in managing and maintaining real-time voice/text/video quality, reliability, and overall performance. In particular, media delivery is an area that needs attention. One method of meeting these challenges is monitoring the media delivery performance by looping media back to the transmitter. This is typically referred to as “active monitoring” of services. Media loopback is especially popular in ensuring the quality of transport to the edge of a given VoIP, real-time text, or Video-over IP service. Today, in networks that deliver real-time media, short of running “ping” and “traceroute” to the edge, administrators are left without the necessary tools to actively monitor, manage, and diagnose quality issues with their service. The extension defined herein adds new SDP media types and attributes that enable establishment of media sessions where the media is looped back to the transmitter. Such media sessions will serve as monitoring and troubleshooting tools by providing the means for measurement of more advanced VoIP, real-time text, and Video-over IP performance metrics.