att_abstract={{Since the last in-depth studies of measured TCP traffic some 6-
8 years ago, the Internet has experienced significant changes, including
the rapid deployment of backbone links with 1-2 orders
of magnitude more capacity, the emergence of bandwidth-intensive
streaming applications, and the massive penetration of new TCP
variants. These and other changes beg the question whether the
characteristics of measured TCP traffic in today�s Internet reflect
these changes or have largely remained the same. To answer this
question, we collected and analyzed packet traces from a number of
Internet backbone and access links, focused on the �heavy-hitter�
flows responsible for the majority of traffic. Next we analyzed their
within-flow packet dynamics, and observed the following features:
(1) in one of our datasets, up to 15.8% of flows have an initial congestion
window (ICW) size larger than the upper bound specified
by RFC 3390. (2) Among flows that encounter retransmission rates
of more than 10%, 5% of them exhibit irregular retransmission behavior
where the sender does not slow down its sending rate during
retransmissions. (3) TCP flow clocking (i.e., regular spacing between
flights of packets) can be caused by both RTT and non-RTT
factors such as application or link layer, and 60% of flows studied
show no pronounced flow clocking. To arrive at these findings,
we developed novel techniques for analyzing unidirectional TCP
flows, including a technique for inferring ICW size, a method for
detecting irregular retransmissions, and a new approach for accurately
extracting flow clocks.}},
	att_authors={ag1971, ss2864, os1872, ww9241},
	att_copyright_notice={{(c) ACM, 2009. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM Internet Measurement Conference{{, 2009-11-04}}}},
	att_tags={TCP, internet traffic analysis, passive measurements},
	author={Feng Qian and Alexandre Gerber and Z. Morley Mao and Subhabrata Sen and Oliver Spatscheck and Walter Willinger},
	institution={{in Proc. of ACM Internet Measurement Conference (IMC)}},
	title={{TCP Revisited: A Fresh Look at TCP in the Wild}},