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The indicator will consist in several graphs representing the number of servers that have been fully synchronized with the master tree after an update of the tree. Different kind of updates will be measured: update of the index file, update of packages of various sizes, updates of ISOs.

According to the system's specifications proposed by WP4, the updates on the global index are effectuated by the trusted peers every time that a new package is published or rebuilt into a new version by the publisher. This is based on the notification mechanism implemented by the system. The notification is done simultateously for all the trusted peers, so each update of the content is immediately registered by the peers and the index is updated accordingly.

The indicator will reflect the efficiency of the multicast algorithm implemented by the P2P system. Basically this indicator expresses the time needed in the multicast phase to diffuse the content in the whole network.

• Hierarchical mirroring architecture
  The timestamps on index files (e.g hdlist) as well as on package files on mirrors will be fetched and stored by EDOS mirror monitoring toolkit. These timestamps will then be computed for issuing a series of statistics on time distance between mirrors and the reference server.
• WP4 P2P architecture
  The evaluation of the time distance indicators can be performed at the peer application level, by comparing the times elapsed between the notification event and the arrival of the package on the client peer.