Abstract The explosive growth of mobile and wireless communications has attracted interests in the integration of mobile and wireless networks with wired ones and the wired Internet in particular. In order to deal with the scalability and reliability issues for group communication services in such a network environment, many existing protocols divide the whole group into subgroups and organize them into a tree-based hierarchy. A special node in each subgroup is responsible for collecting acknowledgement messages and locally retransmitting lost messages within the subgroup. However, the tree-based hierarchy has the single point of failure problem, which may seriously affect the performance of group communications. We propose a RingNet hierarchy of proxies that is a combination of logical trees and logical rings. The proposed hierarchy has the self-organization property because it can heal itself as quickly as possible in the presence of failures. Therefore, it has no single point of failure problem. We formally prove that, with high probability of 99.899%, the proposed hierarchy with up to 10 000 proxies directly attached by a large number of mobile hosts only needs simple and efficient procedures to repair broken logical rings when the node failure probability is bounded by 0.1%. We also validate the proposed protocol by extensive simulations, which show that the proposed protocol scales very well when the size of the network becomes large, and that it is highly resilient to failures when the node failure probability becomes large.