Abstract
We propose a secure group management protocol for a multicast CDN (content delivering network) service. The protocol is IGAP (Internet group membership authentication protocol), which capable of accurate accounting to a user access to IP multicast groups. In IGAP, user authentication process synchronizes a group membership operation. IGAP is designed to be used in a controlled or managed IPv4 multicast environment, when authentication and accounting are required to access the network. The user authentication information in IGAP enables a provider to control the distribution of the multicast traffic as well as to collect real time user accounting information.