Flow Control for Limited

This paper analyzes a multi-round ow control algorithm that attempts to minimize the time required to multicast a message to a group of recipients and receive responses directly from each group member. Such a ow control algorithm may be necessary because the urry of responses to the multicast can overrow the buuer space of the process that issued the multicast. The condition that each recipient directly respond to the multicast prevents the use of reliable multicast protocols based on software combining trees or negative-acknowledgements. The ow control algorithm analyzed here directs the responding processes to hold their responses for some period of time, called the backoo time, before sending them to the originator. The backoo time depends on the number of recipients that will respond, the originator's available buuer space and buuer service time distribution, and the number of times that the originator is willing to retransmit its message. This paper develops an approximate analysis of the service time distribution of the limited buuer, preemptive queuing process that occurs within the protocol processing layers of a multi-programmed operating system. It then uses this model to calculate multicast backoo times. The paper reports experimental veriication of the accuracy of this service time model and discusses its application to the multicast ow control problem.