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On the Spatial-temporal Reachability of DTNs
Cheng Zhang
1
, Chunhe Xia
1,2
, Haiquan Wang
2,3
, and Xiaojian Li
2,4
1
Beijing Key Laboratory of Network Technology, Beihang University, Beijing, China
2
State Key Laboratory of Virtual Reality Technology and Systems, Beihang University,
Beijing, China
3
College of Software, Beihang University, Beijing, China
4
College of Computer Science & Information Technology, Guangxi Normal University,
Guilin, China
zc850717@gmail.com, {xch,whq}@buaa.edu.cn,
xiaojian@mailbox.gxnu.edu.cn
Abstract.
As traditional “Connectivity” concept from the Internet ignores the
possibility of opportunistic contacts in DTNs, this paper brings time dimension
into consideration, proposes Spatial-Temporal Path, Spatial-Temporal Reachabil-
ity and K-Reachability in order to better describe the whole communication
process and “Eventual Transportability” of DTN. Analytical and simulation re-
sults are given to show the correctness of our approach. Furthermore, Spa-
tial-Temporal Reachability and K-Reachability, which tell a network's robustness
in a quantitative fashion, are proved to be suitable for analyzing efficiency and
routing performance of DTNs.
Keywords:
DTN, Connectivity, Spatial-Temporal Reachability.
1
Introduction
Delay/Disruption Tolerant Networks, known as DTNs[1, 2] and DTMNs[3] are some
typical cases of challenged network[4, 5], which is defined as a network that possesses
one or more of the following characteristics: high end-to-end path latency, intermittent
connection between nodes, or the absence of an end-to-end path from sources to des-
tinations. In such situations, TCP, usually used in traditional Internet communication,
faces great challenges when dealing with DTNs' highly dynamic fashion[6]. Therefore,
in a set of new protocols called Bundle, researchers came up with a “store-carry-
forward” strategy[1, 2, 7-9]. A forwarding node carries messages before getting the
“opportunity” to forward them. This strategy enables the message to be delivered
successfully in a given time in a DTN environment. By using Spatial-Temporal
routing[10], the communicating process of DTNs is characterized as opportunis-
tic contacting[11].
Traditional “Connectivity” concepts in relation to the Internet focus on the
end-to-end path between a pair of nodes for an instant time. In order to better understand
