  Connecting usual things/objects to the Internet allows the monitoring and
control of such things from anywhere, which is usually referred to as the
Internet of Things (IoT). Things communicate among themselves or with other
entities (e.g., a server) so that information can be gathered from things
whilst proper actions can be taken upon them. A prominent communication
approach adopted by many IoT applications is related to the Publish/Subscribe
(P/S) paradigm. Any communication entity willing to provide some data announces
its intention to a server (broker), establishing itself as a publisher for such
data/topic. Entities that are willing to receive any published data, register
themselves to the broker as subscribers. While employing just one broker might
lead to a bottleneck and a single point of failure, when having multiple
brokers one could end up having difficulties with their management. This work
presents a scalable and efficient proposal for the federation of independent
brokers, by allowing subscribers to get all their publications no matter to
which broker publishers and subscribers are associated with.
