A simulation tool is developed for the performance analysis and evaluation of Internet phone applications. The tool can be used off-line to simulate real two-way phone conversations under different Internet loss and delay conditions. The simulation model includes access links that connect an Internet service provider to the Internet, as well as background Internet phone and data traffic. It also includes details of Internet phone implementations such as encoding, packetization, silence detection, and the IP, UDP, and RTP protocols. An original feature of the simulator is that it takes into account explicitly the synchronization of talkspurts in a two-way conversation. Example results of two-way conversations under various delay and loss conditions are provided in audio files. Pointers to download the files are at http://www-net.cs.umass.edu/similar to sbmoon/synch.html.