21.1 What is Directed Diffusion?

Directed Diffusion is a method of data dissemination especially suitable in distributed sensing scenarios. It differs from IP method of communication. For IP ``nodes are identified by their end-points, and inter-node communication is layered on an end-to-end delivery service provided within the network''. Directed diffusion, on the other hand is data-centric. Data generated by sensor nodes are identified by their attribute-value pair. Sinks or nodes that request data send out ``interest''s into the network. Data generated by ``source'' nodes that match these interests, ``flow'' towards the sinks. Intermediate nodes are capable of caching and transforming data. For details on directed diffusion, see ``Directed Diffusion: A Scalable and Robust Communication Paradigm for Sensor Networks'', authored by Chalermek Intanagonwiwat, Ramesh Govindan and Deborah Estrin that appeared in MobiCOM, August 2000, Boston, Massachusetts. This and other diffusion related papers can be viewed at https://www.isi.edu/scadds/publications.html under publications section.