Intermittently connected mobile networks are sparse wireless networks where most of the time there does not exist a complete path from the source to the destination. These networks fall into the general category of Delay Tolerant Networks. There are many real networks that follow this paradigm, for example, wildlife tracking sensor networks, military networks, inter-planetary networks, etc. In this context, conventional routing schemes would fail.To deal with such networks researchers have suggested to use flooding-based routing schemes. While flooding-based schemes have a high probability of delivery, they waste a lot of energy and suffer from severe contention, which can significantly degrade their performance. Furthermore, proposed efforts to significantly reduce the overhead of flooding-based schemes have often be plagued by large delays. With this in mind, we introduce a new routing scheme, called Spray and Wait, that "sprays" a number of copies into the network, and then "waits" till one of these nodes meets the destination.Using theory and simulations we show that Spray and Wait outperforms all existing schemes with respect to both average message delivery delay and number of transmissions per message delivered; its overall performance is close to the optimal scheme. Furthermore, it is highly scalable retaining good performance under a large range of scenarios, unlike other schemes. Finally, it is simple to implement and to optimize in order to achieve given performance goals in practice.

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Spray and wait: an efficient routing scheme for intermittently connected mobile networks

We consider the problem of routing in intermittently connected networks. In such networks there is no guarantee that a fully connected path between source and destination exist at any time, rendering traditional routing protocols unable to deliver messages between hosts. We propose a probabilistic routing protocol for such networks.

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Probabilistic routing in intermittently connected networks

Disruption-tolerant networks (DTNs) attempt to route network messages via intermittently connected nodes. Routing in such environments is difficult because peers have little information about the state of the partitioned network and transfer opportunities between peers are of limited duration. In this paper, we propose MaxProp, a protocol for effective routing of DTN messages. MaxProp is based on prioritizing both the schedule of packets transmitted to other peers and the schedule of packets to be dropped. These priorities are based on the path likelihoods to peers according to historical data and also on several complementary mechanisms, including acknowledgments, a head-start for new packets, and lists of previous intermediaries. Our evaluations show that MaxProp performs better than protocols that have access to an oracle that knows the schedule of meetings between peers. Our evaluations are based on 60 days of traces from a real DTN network we have deployed on 30 buses. Our network, called UMassDieselNet, serves a large geographic area between five colleges. We also evaluate MaxProp on simulated topologies and show it performs well in a wide variety of DTN environments.

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MaxProp: Routing for Vehicle-Based Disruption-Tolerant Networks

Delay-tolerant Networking (DTN) enables communication in sparse mobile ad-hoc networks and other challenged environments where traditional networking fails and new routing and application protocols are required. Past experience with DTN routing and application protocols has shown that their performance is highly dependent on the underlying mobility and node characteristics. Evaluating DTN protocols across many scenarios requires suitable simulation tools. This paper presents the Opportunistic Networking Environment (ONE) simulator specifically designed for evaluating DTN routing and application protocols. It allows users to create scenarios based upon different synthetic movement models and real-world traces and offers a framework for implementing routing and application protocols (already including six well-known routing protocols). Interactive visualization and post-processing tools support evaluating experiments and an emulation mode allows the ONE simulator to become part of a real-world DTN testbed. We show sample simulations to demonstrate the simulator's flexible support for DTN protocol evaluation.

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The ONE simulator for DTN protocol evaluation

In this paper, we address the problem of routing in intermittently connected networks. In such networks there is no guarantee that a fully connected path between source and destination exists at any time, rendering traditional routing protocols unable to deliver messages between hosts. There does, however, exist a number of scenarios where connectivity is intermittent, but where the possibility of communication still is desirable. Thus, there is a need for a way to route through networks with these properties. We propose PRoPHET, a probabilistic routing protocol for intermittently connected networks and compare it to the earlier presented Epidemic Routing protocol through simulations. We show that PRoPHET is able to deliver more messages than Epidemic Routing with a lower communication overhead.

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Probabilistic Routing in intermittently connected networks

This document is a product of the Delay Tolerant Networking Research Group and has been reviewed by that group. No objections to its publication as an RFC were raised.

This document defines PRoPHET, a Probabilistic Routing Protocol using History of Encounters and Transitivity. PRoPHET is a variant of the epidemic routing protocol for intermittently connected networks that operates by pruning the epidemic distribution tree to minimize resource usage while still attempting to achieve the best-case routing capabilities of epidemic routing. It is intended for use in sparse mesh networks where there is no guarantee that a fully connected path between the source and destination exists at any time, rendering traditional routing protocols unable to deliver messages between hosts. These networks are examples of networks where there is a disparity between the latency requirements of applications and the capabilities of the underlying network (networks often referred to as delay and disruption tolerant). The document presents an architectural overview followed by the protocol specification.

Probabilistic Routing Protocol for Intermittently Connected Networks

This paper describes the Saami Network Connectivity (SNC) project that seeks to establish Internet communication for the Saami population of Reindeer Herders, who live in remote areas in Swedish Lapland, and relocate their base in accordance with a yearly cycle dictated by the natural behavior of reindeer This population currently does not have reliable wired, wireless or satellite communication capabilities in major areas within which they work and stay (or would prefer to stay if possible) A radical solution is therefore required, which is compatible with the Saami population's goal to uphold their land by being able to live there and care for the environment An approach based on the concept of Delay Tolerant Networks is discussed here

/pdf/providing-connectivity-to-the-saami-nomadic-community-3k4stvgi9e.pdf

Providing connectivity to the Saami nomadic community

Research within Delay- and Disruption Tolerant Networks (DTN) has evolved into a mature research area. PRoPHET is a routing protocol for DTNs that was developed when DTN research was in its infancy and which has been studied by many. In this paper we investigate how the protocol can evolve to meet new challenges that has been identified through research and practical experience. We propose some minor modifications to the routing metric calculations done in PRoPHET which has potential to alleviate some issues and improve the performance of the protocol. Using these modifications, we define an updated version of the protocol called PRoPHETv2. We run simulations to verify the operation of the protocol and compare its performance against the original version of the protocol as well as some other routing protocols. The evaluations are done using both traces from an existing DTN deployment and a synthetic mobility model. Since the basic mechanisms of the protocol remain the same, migrating existing implementations to the new version of PRoPHET is possible with limited effort.

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Avri Doria

Papers

Probabilistic routing in intermittently connected networks

Probabilistic Routing in intermittently connected networks

Probabilistic Routing Protocol for Intermittently Connected Networks

Providing connectivity to the Saami nomadic community

The evolution of a DTN routing protocol - PRoPHETv2