QuickCast: Fast and Efficient Inter-Datacenter Transfers using Forwarding Tree Cohorts
For cloud providers with dedicated WANs, QuickCast addresses the slow-receiver bottleneck in multicast transfers, offering a practical solution to improve performance.
QuickCast speeds up average receiver completion times by up to 10x with only 1.04x more bandwidth, and improves all-receiver completion times by up to 1.6x at high loads for inter-datacenter transfers.
Large inter-datacenter transfers are crucial for cloud service efficiency and are increasingly used by organizations that have dedicated wide area networks between datacenters. A recent work uses multicast forwarding trees to reduce the bandwidth needs and improve completion times of point-to-multipoint transfers. Using a single forwarding tree per transfer, however, leads to poor performance because the slowest receiver dictates the completion time for all receivers. Using multiple forwarding trees per transfer alleviates this concern--the average receiver could finish early; however, if done naively, bandwidth usage would also increase and it is apriori unclear how best to partition receivers, how to construct the multiple trees and how to determine the rate and schedule of flows on these trees. This paper presents QuickCast, a first solution to these problems. Using simulations on real-world network topologies, we see that QuickCast can speed up the average receiver's completion time by as much as $10\times$ while only using $1.04\times$ more bandwidth; further, the completion time for all receivers also improves by as much as $1.6\times$ faster at high loads.