*2.9.14. OCEAN - Observation based cooperation enforcement in ad hoc networks*

OCEAN[75] approach to selfishness in ad-hoc networks is to disallow any second-hand information exchanges. Instead, a node makes routing decisions based solely on direct observations of its neighbouring nodes' interactions with it. OCEAN is designed on top of DSR protocol, may reside on each node in the network and hosts five components: Neighbour Watch (in order to observe the behaviour of the neighbours of a node), Route Ranker (estimating and maintaining ratings for each of the neighbouring nodes), Rankbased Routing (so as to avoid routes containing nodes in the faulty list), Malicious Traffic Rejection (rejecting all traffic from nodes it considers misleading so that a node is not able to relay its own traffic under the guise of forwarding it on somebody else's behalf) and Second Chance Mechanism (using a time-out based approach for removing a node from a faulty list after a fixed period of observed inactivity and assigning to it a neutral value). Once the rating of a node falls below a certain threshold, the node is added to the faulty list comprising all misbehaving nodes. In order to tackle selfish behaviour, the authors introduce a simple packet forwarding economy scheme, relying again only on direct observations of interactions with neighbours.

Due to the usage of only first-hand information, OCEAN is more resilient to rumour spreading. Finally, the authors rely on recent work on proof-of-effort mechanisms and mandate that a new identity will be accepted only if the owner shows reasonable effort in generating that identity.
