  The current Internet design is not capable to support communications in
environments characterized by very long delays and frequent network partitions.
To allow devices to communicate in such environments, delay-tolerant networking
solutions have been proposed by exploiting opportunistic message forwarding,
with limited expectations of end-to-end connectivity and node resources. Such
solutions envision non-traditional communication scenarios, such as disaster
areas and development regions. Several forwarding algorithms have been
investigated, aiming to offer the best trade-off between cost (number of
message replicas) and rate of successful message delivery. Among such
proposals, there has been an effort to employ social similarity inferred from
user mobility patterns in opportunistic routing solutions to improve
forwarding. However, these research effort presents two major limitations:
first, it is focused on distribution of the intercontact time over the complete
network structure, ignoring the impact that human behavior has on the dynamics
of the network; and second, most of the proposed solutions look at challenging
networking environments where networks have low density, ignoring the potential
use of delay-tolerant networking to support low cost communications in networks
with higher density, such as urban scenarios. This paper presents a study of
the impact that human behavior has on opportunistic forwarding. Our goal is
twofold: i) to show that performance in low and high density networks can be
improved by taking the dynamics of the network into account; and ii) to show
that the delay-tolerant networking can be used to reduce communication costs in
networks with higher density by taking the behavior of the user into account.
