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Paper by David Culler, Philip Levis, Neil Patel, and Scott Shenker Presented by: Lee Hathcock. Trickle: A Self-Regulating Algorithm for Code Propagation and Maintenance in Wireless Sensor Networks. The Problem. Code propagation in WSNs is costly
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Paper by David Culler, Philip Levis, Neil Patel, and Scott Shenker Presented by: Lee Hathcock Trickle: A Self-Regulating Algorithm for Code Propagation and Maintenance in Wireless Sensor Networks
The Problem • Code propagation in WSNs is costly • Desire an algorithm for scheduling code propagation • Low maintenance • Rapid propagation • Scalable • The solution? Trickle, of course. • Few packets per hour, propagates in tens of seconds, scales well, robust, and only 11 bytes of state info
Trickle Overview • Every once in a while, a node transmits code “metadata” that represents its current code, provided it hasn’t heard the same data recently. • Either all nodes are up to date, or… • …a node needs to be updated. • If a node needs to be updated, it happens by either… • …a node hearing that it is out of date, and broadcasts its metadata so it can be updated, or… • …a node hears that another node is out of date, and sends an update to the code.
Trickle Algorithm • “Polite gossip” • Parameters • c: a counter, incremented each time a node hears its own metadata • k: a threshold, usually between 1 and 2 • t: a timer value, between the range of 0- • : a time constant
Algorithm Analysis • k*m packet transmissions, but only under the following assumptions • No packet loss • Perfect interval synchronization • Single hop network • Relax each of these constraints
Conclusions • Related work • SPIN, SPIN-RL • SRM • Demers et al. • PlanetP • Reijers et al. • Assumes nodes always on • More of a scheduler than anything • As such, can be used for more than code propagation
References • P. Levis, N. Patel, D. Culler, and S. Shenker, "Trickle: A self-regulating algorithm for code propagation and maintenance in wireless sensor networks," NSDI, 2004.