IP Multicasting has been a crucial requirement of many scalable networked virtual environments by providing an efficient network mechanism through which a sender can transmit its information to a large number of receivers without having to send multiple copies of the same data over a physical link. The widespread deployment of IP Multicast has been slow due to some yet unresolved issues, prompting recent efforts in the development of multicasting protocols at the application layer instead of at the network layer. Most of these protocols address the case of a single source streaming media to a large number of receivers in applications such as video-on-demand or live broadcast. Collaborative and distributed virtual environments exhibit different characteristics that in turn necessitate a different set of requirements for application layer multicast protocols. This paper presents an introduction to application layer multicasting as it relates to distributed and collaborative virtual environments and the development of our own end system multicast protocol for multi-sender virtual teleconference applications.