Internet of Things – Architecture © - 91 -
translatable to HTTP by decompression or XML is translatable to
EXI by compression, IPv4 is translatable to IPv6 by mapping;- Constrained device support. For instance, in the recurring
example, the raw data produced by the Mote Runner Sensors
shall be converted into machine-readable formats in order for the
Alarm Service to be able to interprete and use them.
3.6.3 Composed modelling options
Actual networks may need more than a single communication stack that can be
arranged in several configurations: in particular, here we will analyse how two of
the most popular configurations can be modelled according to the IoT
Communication Model. In the following we will refer to (1) gateway configuration
as the composition of two or more protocol stacks that are placed side by side
across different media, and (2) virtual configuration as the composition of two or
more protocol stacks, one on top of the other.
3.6.3.1 Gateway configuration
In this configuration, the IoT Communication Model describes the overall
communication behaviour of the system so that any two communicating
element can be seen seamlessly connected.
Figure 21 provides a graphical example of the modelling of three protocol
stacks in gateway configuration. In this example, the two end-point Application
Layers can communicate thanks to the gateways which maps the underline
stacks.
Figure 21 : Gateway configuration for multiple protocol stacks, aligned according to the
IoT aspect model (see Figure 20 ).In particular, the first gateway (on the left of the figure) bridges the
communication between an Ethernet and a WiFi network, while the second (on
the right), in addition to the bridging functionality between WiFi and ZigBee,