Actually, in the literature there is no commonly agreed-upon terminology nor clear separation of concepts for opportunistic and delay-tolerant networks. The terms “opportunistic networks” and “delay-tolerant networks” are often used interchangeably. In our view, given the above DTN definition, opportunistic networks correspond to a more general concept and include DTNs. While DTNs assume the knowledge of Internet-like topologies, in which some links between gateways could be available just at certain (possibly unspecified) times, in opportunistic networks it is not mandatory to have a priori knowledge about the network topology. Routes in DTNs are typically computed via legacy-Internet techniques by taking into consideration the link unavailability just as another component of link cost. Instead, in opportunistic networks routes are computed at each hop while a packet is forwarded. So, each node receiving a message for an eventual destination exploits local knowledge to decide which is the best next hop, among its current neighbors, to reach the eventual packet destination. When no forwarding opportunity exists (e.g., no other nodes are in the transmission range, or the neighbors are evaluated not suitable for that communication), the node stores the message and waits for future contact opportunities with other devices to forward the information. Differently from DTNs, in opportunistic networks each single node acts as a gateway. This makes opportunistic networks a more flexible environment than DTNs, and calls for a more radical revision of legacy routing approaches designed for the Internet or for wellconnected MANETs.
Pelusi, L., Passarella, A., & Conti, M. (2006). Opportunistic networking: data forwarding in disconnected mobile ad hoc networks.IEEE communications Magazine,44(11), 134-141.
- 机会网络不需要有网络拓扑的相关先验知识
- 机会网络的路由在每一个包被转发的时候可能都是不一样的。（机会主义）
- 机会网络的每个节点都是网关。
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