The copies of message routing and the data forwarding routing are the major in the current researches on sensor network delay-tolerant routing [1].
Anonymous communication protocols (e.g., Onion Routing [1], TOR [2], Dissent [3, 4], RAC [5]) are the main solutions enforcing this property.
The problem of the intermittent connectivity due to the random mobility of the nodes in the network brings great challenges to the routing [1].
Anonymous networks (e.g., Onion Routing [1], Tor [2], Dissent [3, 4], RAC [5]) represents a more complex approach to prevent a third party to map a user identity to a query.
In order to improve the four-stage traditional routing [1, 2], network coding has been introduced to attain the maximum possible information flow and to increase the network throughput [3 7].
Location-based routing [27] and directional routing [28] is also experimented for WSNs.
Alternatively, opportunistic feeding and routing [10] has also been experimented.
Epidemic routing [9] is a typical one among these protocols.
Prominent examples are cognitive radio [57 59], network coding [60, 61] and directional routing [62, 63].
According to the number of the copies of message in the network, it can be divided into simple-copy routing [8, 9] and multi-copy routing [10, 11].
The main representative algorithms are as follows: direct transmission routing protocol [12, 13], first-time-connection routing protocol [8], random routing protocol [9], Spray and Wait routing protocol [14], Epidemic routing protocol [10], and RDAD routing protocol [15].
