Why Use a Fishing Line When you Have a Net? An Adaptive Multicast Data Distribution Protocol

The design and implementation of a system to provide reliable and efficient distribution of large quantities of data to many hosts on a local area network or internetwork is described. By exploiting the one-to-many transmission capabilities of multicast and broadcast, it is possible to transmit data to multiple hosts simultaneously, using less bandwidth and thus obtaining greater efficiency than repeated unicasting. Although performance measurements indicate the superiority of multicast, we dynamically select from available transmission modes so as to maximize efficiency and throughput while providing reliable delivery of data to all hosts. Our results demonstrate that file-distribution programs based on our protocol can benefit from a substantial speed-up over TCP-based programs such as rdist. For example, our system has been used to distribute a 133 Kbyte password file to 68 hosts in 20 seconds, whereas the equivalent rdist took 251 seconds.