3 research outputs found
A comparative study of aggregate TCP retransmission rates
Segment retransmissions are an essential tool in assuring reliable end-to-end
communication in the Internet. Their crucial role in TCP design and operation
has been studied extensively, in particular with respect to identifying
non-conformant, buggy, or underperforming behaviour. However, TCP segment
retransmissions are often overlooked when examining and analyzing large traffic
traces. In fact, some have come to believe that retransmissions are a rare
oddity, characteristically associated with faulty network paths, which,
typically, tend to disappear as networking technology advances and link
capacities grow. We find that this may be far from the reality experienced by
TCP flows. We quantify aggregate TCP segment retransmission rates using
publicly available network traces from six passive monitoring points attached
to the egress gateways at large sites. In virtually half of the traces examined
we observed aggregate TCP retransmission rates exceeding 1%, and of these,
about half again had retransmission rates exceeding 2%. Even for sites with low
utilization and high capacity gateway links, retransmission rates of 1%, and
sometimes higher, were not uncommon. Our results complement, extend and bring
up to date partial and incomplete results in previous work, and show that TCP
retransmissions continue to constitute a non-negligible percentage of the
overall traffic, despite significant advances across the board in
telecommunications technologies and network protocols. The results presented
are pertinent to end-to-end protocol designers and evaluators as they provide a
range of "realistic" scenarios under which, and a "marker" against which,
simulation studies can be configured and calibrated, and future protocols
evaluated