Because a multicast data server or broadcast disk can have clients of very different network capacities, the server needs to offer its repository of data items at a variety of transmission speeds to service clients' varied requests. In this paper, we study how to slice a server's available outgoing network capacity into data channels, how to assign the server's data to those channels, and how to assign clients to the channels given clients' varied requests and download speeds. We find that good choices in this area can improve performance for clients by three-fold or more, and surprisingly, finding the good choices do not require advance knowledge of clients' exact download speeds, once we have chosen the slowest client speed we want to support.
This paper considers how to divide a multicast server's data and outgoing network bandwidth (throughput) into multiple data channels, so that the server can accommodate clients of different download-connection speeds. Clients attempting to download data faster than their connections support will suffer transmission losses and unfairly throttle other transmissions sharing the same connection, so it is important for clients to receive no more data channels than their connection's throughput will support. The paper considers how the number of data channels the server provides impacts system performance, and compares different ways the server can divide its outgoing bandwidth among the channels, two factors that determine the lowest-throughput client the server is willing support. This paper also studies how to assign clients to the server's channels to consume the clients' bandwidth, evaluates how the cost of data-channel bandwidth can affect performance, and considers the performance effect of a server that knows its clients' exact connection speeds in advance and sets its data channels accordingly.
@techreport{lg-channels-extended,
author = {Wang Lam and Hector Garcia-Molina},
title = {Slicing Broadcast Disks (extended version)},
institution = {Stanford University},
year = {2003},
note = {Available at http://dbpubs.stanford.edu/pub/2003-50}
}