Redundancy and distributed caching in mobile DTNs

Pitkänen, Mikko; Ott, Jörg

doi:10.1145/1366919.1366930

Cited by 34 publications

(19 citation statements)

References 29 publications

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“…We choose delay-tolerant networks as traditional ad-hoc networking places tight demands on connectedness of the nodes, which appears infeasible in our scenario. This paper extends our earlier work on opportunistic content caching and retrieval using resource identifiers [17] [18] and complements related work on using DTNs for active content dissemination to interested users [16] [14]. We introduce a simple notion of content queries based upon which we present how nodes should process and forward queries and respond to them returning matching locally available contents.…”

Section: Introductionmentioning

confidence: 70%

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Searching for content in mobile DTNs

Pitkänen

Kärkkäinen²,

Greifenberg³

et al. 2009

2009 IEEE International Conference on Pervasive Computing and Communications

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Abstract-Delay-tolerant Networking (DTN) provides a platform for applications in environments where end-to-end paths may be highly unreliable or do not exist at all. In many applications such as distributed wikis or photo sharing, users need to be able to find content even when they do not know an unambiguous identifier. In order do bring these applications to the domain of DTNs, a search scheme is required that works despite the unreliable network conditions. In this paper, we introduce a search scheme that makes no assumptions about the underlying routing protocols and the format of search requests. We evaluate different algorithms for forwarding and terminating search queries, using simulations with different classes of DTN routing protocols for different mobility scenarios.

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Section: Introductionmentioning

confidence: 70%

“…Earlier work by the authors has investigated web resource retrieval in mobile DTNs via Internet gateways [17] and shown how caching improves efficiency with shared interest on resources [18], using well-known DTN routing mechanisms.…”

Section: A Search In Unstructured and Ad-hoc Networkmentioning

confidence: 99%

Searching for content in mobile DTNs

Pitkänen

Kärkkäinen²,

Greifenberg³

et al. 2009

2009 IEEE International Conference on Pervasive Computing and Communications

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“…Transferring large data in small fragments without explicit acknowledgments may lead to reliability degradation in best-effort networks because all fragments should arrive at destination in order for the initial message to be reconstructed [26]. Redundancy ratio can then be chosen to improve delivery ratio while keeping volume transferred over the network at an acceptable limit.…”

Section: Message Fragmentation and Dtnmentioning

confidence: 99%

Adding Redundancy to Replication in Window-aware Delay-tolerant Routing

Sandulescu¹,

Nadjm‐Tehrani²

2010

JCM

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Abstract-This paper presents a resource-efficient protocol for opportunistic routing in delay-tolerant networks (DTN). First, our approach exploits the context of mobile nodes (speed, direction of movement and radio range) to estimate the size of a contact window. This knowledge is exploited to make better forwarding decisions and to minimize the probability of partially transmitted messages. Optimizing the use of bandwidth during overloads helps reduce energy consumption since partially transmitted messages are useless and waste transmission power. Second, we use a differentiation mechanism based on message utility. This allows allocating more resources for high utility messages. More precisely, messages are replicated in the order of highest utility first, and removed from the buffers in the reverse order. To illustrate the benefit of such a scheme, global accumulated utility is used as a system-wide performance metric. Third, we present a combined fragmentation/redundancy scheme which not only improves delivery ratio but also, if infrastructure is available, allows messages to be completed by pulling dropped fragments.Simulations illustrate the benefit of our model and show that our scheme provides lower overhead and higher delivery ratio, as well as higher accumulated utility compared to a number of well-known algorithms including Maxprop and SprayAndWait.

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“…Moreover, nodes may send out packets with linear combinations of previously received information leading to network coding [13]. In other cases, distributed caching is studied as a particular case of applied redundancy [14].…”

Section: Background and Related Workmentioning

confidence: 99%

Optimising Replication versus Redundancy in Window-Aware Opportunistic Routing

Sandulescu¹,

Nadjm‐Tehrani

2010

2010 Third International Conference on Communication Theory, Reliability, and Quality of Service

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Abstract-In this paper we address the replication versus redundancy optimisation problem for a class of intermittentlyconnected ad hoc networks with the following three characteristics: routing is performed by a store-carry-forward mechanism in an opportunistic manner, replication of custodian messages is used to increase the delivery ratio, and fragmentation combined with redundancy in the form of erasure coding is used to deal with large messages in short contact windows. We propose a novel mathematical model in which the merits of a high replication factor can be compared to a high level of redundancy in erasure coding. The purpose of the model is to identify the optimised level of replication and redundancy as a function of application-specific parameters like message size and time-to-live. Our model builds upon a component for message latency distribution that we have borrowed from earlier works (SprayAndWait) and that has been extended for erasure coding and constrained resources. The model is general and can be applied in different opportunistic settings using the following approach. First, we derive a set of equations that are demonstrated to identify the optimal replication and redundancy factor in a network with constrained resources. Then, the paper includes an extension that provides a tailormade latency distribution based on history profiling, thus making it applicable to any protocol that uses replication/redundancy in a similar network. By theoretical analysis and simulations, we demonstrate that using erasure coding together with replication offers an efficient yet flexible tradeoff between resource cost and protocol performance.

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Redundancy and distributed caching in mobile DTNs

Cited by 34 publications

References 29 publications

Searching for content in mobile DTNs

Searching for content in mobile DTNs

Adding Redundancy to Replication in Window-aware Delay-tolerant Routing

Optimising Replication versus Redundancy in Window-Aware Opportunistic Routing

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