Lakshminarayanan Subramanian*, Ion
Stoica* , Hari Balakrishnan+ ,Randy H. Katz*
* University of
California at Berkeley
+ Massachusetts
Institute of Technology
{lakme,istoica,randy}@cs.berkeley.edu
hari@nms.lcs.mit.edu
This paper describes the design, implementation, and experimental evaluation of 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 
. Using a wide-area overlay testbed of 19 hosts, we show that: (a) OverQoS
can simultaneously provide statistical loss guarantees of 
coupled with statistcal bandwidth guarantees ranging from 
Kbps to 
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.
