sport Protocol for Real-Time Applications. RTP seeks to provide end-to-end network transport functions that are suitable for applications that transmit data with real-time properties, (e.g., audio and video) over multicast or unicast network services. Applications typically run RTP on top of UDP, although RTP can also be used with other underlying network or transport protocols. RTP, a higher layer protocol, does not provide a mechanism to ensure that packets associated with a media stream arrive on time or in sequence. Lower layer services take care of those tasks. However, RTP does include a sequence number to allow the receiver to reconstruct packets in order. The sequence number can also be used to reconstruct a frame of video, for instance, an H.261 group of blocks (GOBs). The User Location Service (ULS), developed in February 1996 by R. Williams of Microsoft Corporation, is a protocol for locating hosts and establishing real-time sessions between them. The ULS is a directory, a place in cyberspace where a client can publish connection information such as the transport address of an application or a person. The ULS enables communication between compatible applications by allowing other clients to retrieve these addresses. The ULS is in not a part of the RTP, but the RTCP is. The RTCP, described along with the RTP in RFC 1889, is used to monitor the quality of service provided in a videoconference. It allows conferees to convey quality information to the meeting's chair or other person responsible for the conference's usability. RTCP provides the option for a sender to receive feedback from the recipients of a multicast stream on the success of RTP packet delivery. Since all participants get the same information, a single site can determine whether reception problems are unique to a site or are conference-wide. A sender can use the feedback from multiple recipients to adjust the broadcast, and scale back video quality or eliminate it entirely to reduce bandwidth requirements. Network administrators can use RT