Embedded Rule-based Management for Content-based DTNs - Advances in Network-Embedded Management and Applications - page 88

Fig. 1. The DEMOS Project
vulnerable neighborhoods as well as at their schools, parks, etc. The environmen-
tal data collected by those sensors are transmitted, using opportunistic networking
techniques, to the children's laptops as they pass by during their daily life. Later,
at school, using the same techniques, the data will be transmitted into the local
school server and from there to an environment monitoring station using the Inter-
net. This monitoring station may be operated by governmental or non-governmental
organizations, including the same community that is being object of the monitoring.
Each time data moves from sensors to laptops, school servers and monitoring
stations, the collected information is aggregated and summarized to guarantee the
scalability of the solution. Additionally, since the information may include data
about the position and environment of peoples' houses, the condentially of that
information has to be protected by encryption or anonymization techniques.
Opportunistic networks (ON), sometimes called Delay Tolerant Networks (DTN),
as opposed to infrastructure networks, are built on-the-y by mobile, intermittently
connected ad-hoc nodes, allowing to run delay tolerant applications. Many ON
routing algorithms have been proposed, see [8] for a comprehensive review, but the
common idea is always to store the message, to carry it for some time, and to for-
ward it when a suitable mobile node happens to be in range with the hope that,
after some of these store-and-forward steps, the message will eventually arrive to
its destination.
The optimum values for DTN algorithm's parameters are dependent on the
network characteristics (number of nodes, movement patterns) and data ow char-
acteristics (load, data patterns). Usually, those attributes are highly dynamic and
hard to predict. Some analysis can be done through extensive simulation, but fact
remains that to optimize the network performance, conguration parameters must
be adjusted to the environment, at runtime.