  Website fingerprinting is an attack that uses size and timing characteristics
of encrypted downloads to identify targeted websites. Since this can defeat the
privacy goals of anonymity networks such as Tor, many algorithms to defend
against this attack in Tor have been proposed in the literature. These
algorithms typically consist of some combination of the injection of dummy
"padding" packets with the delay of actual packets to disrupt timing patterns.
For usability reasons, Tor is intended to provide low latency; as such, many
authors focus on padding-only defenses in the belief that they are
"zero-delay." We demonstrate through Shadow simulations that by increasing
queue lengths, padding-only defenses add delay when deployed network-wide, so
they should not be considered "zero-delay." We further argue that future
defenses should also be evaluated using network-wide deployment simulations
