MBONE: Multicasting Tomorrow's Internet
Multicast routing algorithms are described in the paper "Multicast Routing in Internetworks and Extended LANs" by S. Deering, in the Proceedings of the ACM SIGCOMM '88 Conference. His dissertation Multicast Routing in a Datagram Network is available: ftp://gregorio.stanford.edu/vmtp-ip/
There is an article in the June 1992 ConneXions about the first IETF audiocast from San Diego, and a later version of that article is in the July 1992 ACM SIGCOMM CCR. A reprint of the latter article is available by anonymous FTP from ftp://venera.isi.edu/pub/ietf-audiocast-article.ps.