Cell2

















 Celll
 Cell3

 Isolated Cell Cells with common hosts

 Figure 3.5 Isolated Cells

3.3.2 Godfather-Child Policy

 Every host selects one of its neighbors as its godfather. Whenever the IDS on the

host dies it is the godfather's responsibility to bring it back to life. To tell the godfather

that it is awake, the host periodically sends out "alive" messages to the godfather. The

godfather expects to receive these messages at regular intervals. In case it does not

receive the "alive" message the godfather will timeout. After timing out, it will try to

bring the host back to life, and raise an alert with its local coordinator. The godfather -

child policy is implemented by the heartbeat module of the EGIDEM architecture.

 There are a few rules for selecting the godfather for a host.

 If A is the godfather of B then B cannot be the godfather of A.

 Small cycles of godfathers should be avoided as far as possible. A cycle is
 desirable in case it spans the whole network. This measure helps to make sure
 that bringing down a select set of IDSs at a time does not proceed without an