6. Case study
In the department of Computer Science at the Technische
Universität München the TinyIPFIX protocol was
developed in order to support an efficient data transmission
in a wireless sensor network with constrained hardware.
One of the application scenarios is building
automation where different environmental data, such as
temperature, sound, light, and humidity, is monitored [2].
The TinyIPFIX protocol is based on the IETF Standard IPFIX
which was developed for monitoring in large Peer-to-
Peer networks. It is interesting for sensor networks because
it is easy to parse and has a high transmission efficiency
and little overhead due to its push-protocol
characteristic and its template-based design [26]. In sensor
networks the data is measured periodically in pre-defined
intervals and often processed and aggregated in the network
in order to save network traffic on the way to the
data sink. TinyIPFIX supports these properties and is described
in detail in references [26] and [2]. In order to provide
more security, the established wireless sensor
network was extended by sensor hardware performing
DTLS security. As before, we chose the OPAL node [21].
The TinyIPFIX protocol introduced earlier is included on
the application layer in the performed solution of the
department, which allows an independent functionality
to the underlying layers. Thus, it is straightforward to integrate
a DTLS solution into the network while still using
TinyIPFIX as the application protocol of choice. However,
our current implementation requires more resources than
smaller motes, such as the TelosB mote, have to offer. Thus,
the network is subdivided into clusters where the OPAL
node works as a cluster head. It can also perform the innetwork
message aggregation to reduce network overhead.