Lakshminarayanan Subramanian, Ion Stoica, Hari Balakrishnan, and Randy Katz
Proc. 1st Symposium on Networked Systems Design and Implementation (NSDI), San Francisco, CA, March 2004.

This paper describes the design, implementation, and experimental evaluation of {\em OverQoS}, an overlay-based architecture for enhancing the best-effort service of today's Internet. Using a Controlled loss virtual link (CLVL) abstraction to bound the loss rate observed by a traffic aggregate, OverQoS can provide a variety of services including: (a) smoothing packet losses; (b) prioritizing packets within an aggregate; (c) statistical loss and bandwidth guarantees.

We demonstrate the usefulness of OverQoS using two sample applications. First, RealServer can use OverQoS to improve the signal quality of multimedia streams by protecting more important packets at the expense of less important ones. Second, Counterstrike, a popular multi-player game, can use OverQoS to avoid frame drops and prevent end-hosts from getting disconnected in the presence of loss rates as high as 10%. Using a wide-area overlay testbed of 19 hosts, we show that: (a) OverQoS can simultaneously provide statistical loss guarantees of 0.1% coupled with statistcal bandwidth guarantees ranging from 100 Kbps to 2 Mbps across international links and broadband end-hosts; (b) OverQoS incurs a low bandwidth overhead (typically less than 5%) to achieve the target loss rate, and (c) the increase in the end-to-end delay is bounded by the round-trip-time along the overlay path.

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