Failure handling in a reliable multicast protocol for improving buffer utilization and accommodating heterogeneous receivers

Reliable multicast protocols are an important class of protocols for reliably disseminating information from a sender to multiple receivers in the face of node and link failures. A tree-based reliable multicast protocol (TRAM) provides scalable reliable multicast by grouping receivers in hierarchical repair groups and using a selective acknowledgment mechanism. We present an improvement to TRAM to minimize the resource utilization at intermediate hosts and to localize the effect of slow or malicious receivers on normal receivers. We present an evaluation of TRAM and TRAM++ on a campus-wide WAN without errors and with message errors. The evaluation brings out that, given a constraint on the buffer availability at intermediate hosts, TRAM++ can tolerate the constraint at the expense of increasing the end-to-end latency for the normal receivers by only 3.2% compared to TRAM in error-free cases. When slow or faulty receivers are present, TRAM++ is able to provide the same uninterrupted quality of service to the normal nodes while localizing the effect of the faulty ones without incurring any additional memory overhead.