There exists a formal description format for multicast sessions, the Session Description Protocol (SDP, RFC 2327). The most widely adopted manifestation of this protocol is the graphical SDR tool (Session Directory Tool). A user can join an advertisement by clicking the particular entry.
Alternative approaches use web portals or Java applets to display session announcements. For detailed information on these tools and multicast applications in general, visit the excellent repository of the UCL Networked Multimedia Research Group at http://www-mice.cs.ucl.ac.uk/multimedia/software.
Multicast Security
Discussion of multicast security issues is primarily carried out in the IETF Multicast Security (msec) Working Group. It deals with secure group communication for large groups involving a single trusted entity (authoritative group controller), which establishes and enforces the group's security policy and join/leave procedures to secure groups.
Of course, group key management and distribution involving a mechanism called group security associations (GSAs) is essential to the overall architecture. A GSA represents the multicast equivalent of a unicast security association (SA) that is well known from the IPSec protocol framework.
Another important aspect of multicast security is the delicate issue of (distributed) denial of service ([D]DoS) in multicast environments. For further details, look at the foundation document for multicast security, the IETF draft "The Multicast Security Architecture" (http://www.ietf.org/internet-drafts/draft-ietf-msec-arch-04.txt). This document describes an end-to-end security framework independent of aspects such as NAT, multicast routing, admission control protocols, and reliable multicast mechanisms.
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