Distributed database

The database that describes the overlay domain topology is stored in a distributed database.

Every Network Monitoring Element (the theodolite in the previous terminology) hosts a proxy of such abstract entity.

Such component keeps updated a local image of the database. Updates are propagated using an epidemic, peer-to-peer protocol.

The footprint of such protocol is kept under control by adaptively changing the number of tokens in the system, using a fully distributed feedback algorithm.

The simulation of such protocol in a system of 1000 NME gave encouraging results:

update frequency  1/5 1/secs
overall traffic	  5   MB/sec
update latency    40  secs

with a setup which is appropriate for a classical packet switching environment.

The simulation proved that the algorithm is self-stabilizing under severe stress (for instance, doubling instantaneously the number of NME

Layout of the NME

Passive monitoring

up: A modular approach to Grid Connectivity Monitoring