The Minion architecture of Nowlan et
al. 12 has several features that would be
beneficial and complementary to Paceline’s strengths, such as its SSL strategy
and wire-compatible changes to TCP
that allow unordered receive.
Paceline reduces sender-side queuing delay by writing the minimum
amount to the TCP socket buffer. Recently, the bufferbloat problem has received greatly renewed general attention
and interest. The recent algorithm work
by Kathleen Nichols and Van Jacobson
is a promising step since it is easy to implement and needs no configuration. 11
What is still missing, however, is true
end-to-end evaluation that quantifies
the total combined effect of refinements
to TCP, ECN (Explicit Congestion Notification), AQM (Active Queue Management), and adaptive multimedia.
Underlying our interest is what we
believe remains an open question: Is
there really a line between applications
that needs to break from TCP for interactivity reasons? This is a line that has
been moving steadily over time.
Introducing a new transport layer is
challenging because the designer must
address several critical issues. First, the
transport layer has to improve performance significantly for the target applications in order to justify the extra effort. Second, the enhancements should
not negatively affect other traffic types;
we adhere to the vision that the Internet
should remain a general-purpose infrastructure for a vast array of applications.
Finally, the performance improvements
at the transport level in terms of latency,
fairness, and utilization need to translate to quality improvements at the application level. Paceline has shown positive results in all these aspects.
We tested Paceline extensively using videoconferencing scenarios over
WAN settings. Paceline was also used
in a small cloud-based game prototype
to scale the wide area communication
of an Epic-scale game scenario. 13 Both
of these applications show significant
improvements in multimedia quality because of the reductions in TCP
sender-side delays and the use of adaptation in Paceline.
To ensure we have a general-purpose
transport supporting a wide range of
applications, we tested using a network
traffic generator simulating different
HTTP Web traffic flavors (for example,
HTTP1.0 and HTTP1.1, with and with-
out pipelining). The experiment tested
Web document downloads while vary-
ing the number of objects per page and
the page size. Paceline improved the
bandwidth utilization using the multi-
streaming feature as we increased the
number of objects as a result of the
automatic pipelining of small transac-
tions on top of the underlying channel.
Thanks to colleagues at the Network,
Systems, and Security lab at the Univer-
sity of British Columbia for their feed-
back on previous drafts of the article.
Special thanks to Mahdi Tayarani Na-
jaran for his significant contributions
to the design and implementation of
Paceline. Finally, thanks to Terry Coatta
for helping to improve both the style
and content of this article.
Four Billion Little Brothers?: Privacy, mobile
phones, and ubiquitous data collection
VoIP: What is it Good for?
Sudhir R. Ahuja and Robert En
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Aiman Erbad recently joined the computer science and
engineering department at qatar University as an assistant
professor after completing his Ph.d. at the University
of British Columbia. His research interests include Web
architecture, networking, real-time multimedia, ubiquitous
computing, and concurrency support.
Charles “Buck” Krasic works on large-scale processing
of video at google’s You Tube. Prior to joining You Tube, he
was a professor in the department of computer science
at the University of British Columbia. His research led to
the development of qStream. Other research interests
include multimedia, operating systems, networking, and