Internet Protocols (IP) required end-to-end connectivity. It operates poorly in an environment with a very long delay path and frequent network partitions which causes by severe power or memory constraints by end nodes which make the network infrastructure lacking ‘always-on’ environment. Delay and disruption can be caused by long distance and time. There are some fundamental assumptions in the internet architecture that can cause a break in the network under long delays and intermittent connectivity such as
i. There is always an end-to-end path between source and destination exists.
ii. Need to establish at least one round-trip or transmission and response before any application data can flow. This means that there is a requirement of the sender and receiver negotiate a connection to regulate the flow of data.
iii. Retransmissions from the source are good way to provide reliable communication.
iv. End-to-end loss is relatively small.
v. Endpoint-based security is sufficient to meet most security concerns.
DTN is used to tolerate long delays and intermittent connectivity which is a weakness in Internet Protocols. DTN is able to enable a connection when there is no end-to-end path between the source and destination, the round-trip is not needed to regulate the flow of data, retransmission from data receivers is not in use for repairing errors because there is no end-to-end path and unlike IP, DTN is ignoring the end-to-end dependency such as in IP fundamental assumptions (iv) and (v). There are environments that exhibiting some of these characteristics which are:
i. Space communications where there are high latencies, intermittent connectivity due to antenna schedule.
ii. Sensor networks when nodes need to power down to conserve energy.
iii. Line of sight radios especially for urban area with wooded/hill environments.
iv. Mobile networks