Disruption-Tolerant Networking: A Comprehensive Survey on Recent Developments and Persisting Challenges

Maurice J. Khabbaz, Chadi M. Assi, Wissam F. Fawaz
2012 IEEE Communications Surveys and Tutorials  
Nowadays, wireless networks are witnessing several deployments in various extreme environments where they suffer from different levels of link disruptions depending on the severity of the operating conditions. In all cases, their operation requirements are differently altered and their performance is negatively affected rendering them heterogeneous by nature. In the open literature, these networks are known as Intermittently Connected Networks (ICNs). The existing Internet protocols fail to
more » ... ate properly in the context of ICNs, thus raising a variety of new challenging problems that are attracting the attention of the networking research community. Delay-/Disruption-Tolerant Networking emerged as a highly active area of research where networking experts compete in addressing the various ICN problems. Over time, unicast routing, one of the architectural key components common to all ICNs, became an almost independent field of research in which significant efforts continue to be invested. In contrast, network architectural designs, scheduling and forwarding issues dating from the early days of Inter-Planetary Networks (IPNs) have received relatively little attention and accumulate numerous pending challenges. Moreover, the gap caused by the lack of accurate ICN mathematical models is still large irrespective of some of the appreciated seminal works in this direction. This paper sheds the light over the latest advancements in each of the above-mentioned research sectors and highlight pending open issues in each of them. to reside in a node's buffer for a long period of time. Based on this assumption, buffer sizes are relatively small and optimized in such a way to keep a low overall packet drop rate due to buffer overload. Following these fundamental assumptions, the Internet, the global packet switching network, was conceived and its operating protocols, particularly the TCP/IP protocol suite, were developed. However, such assumptions may not be appropriate when modeling existing and recently emerging wireless networks, especially those deployed in extreme environments (e.g. battlefields, volcanic regions, deep oceans, deep space, developing regions, etc.) where they suffer challenging conditions (e.g. military wars and conflicts, terrorist attacks, earthquakes, volcanic eruptions, floods, storms, hurricanes, severe electromagnetic interferences, congested usage, etc.) resulting in excessive delays, severe bandwidth restrictions, remarkable node mobility, frequent power outages and recurring communication obstructions. Under such conditions, wireless network connectivity becomes considerably intermittent and the existence of contemporaneous end-to-end path(s) between any source-destination pair can no longer be guaranteed. Unusual and repetitive occurrences of network partitioning and topology changes occur; thus, it is utterly probable that two nodes currently co-existing in an arbitrary connected portion of the network may not co-exist in that same or any different connected network portion in the future. Due to low power, network nodes often unexpectedly shut down or enter sleep mode for energy saving resulting in frequent link disruptions. Data transmission rates become highly asymmetric and links highly error prone. When coupled with relatively small node buffer sizes, buffer overload becomes a severely penalizing problem as it exponentially increases the packet drop rate. Popular examples of such intermittently connected networks (ICNs) scenarios, which have already been the subject of extensive research, include:
doi:10.1109/surv.2011.041911.00093 fatcat:isxq2w2ppjgp3bfxu7bbfwcmli