A class of structured P2P systems supporting browsing

Browsing is a way of finding documents in a large amount of data which is complementary to querying and which is particularly suitable for multimedia documents. Locating particular documents in a very large collection of multimedia documents such as the ones available in peer to peer networks is a difficult task. However, current peer to peer systems do not allow to do this by browsing. In this report, we show how one can build a peer to peer system supporting a kind of browsing. In our proposal, one must extend an existing distributed hash table system with a few features : handling partial hash-keys and providing appropriate routing mechanisms for these hash-keys. We give such an algorithm for the particular case of the Tapestry distributed hash table. This is a work in progress as no proper validation has been done yet.Comment: 14 page

A decentralized service discovery approach on peer-to-peer network

Service-Oriented Computing (SOC) is emerging as a paradigm for developing distributed applications. A critical issue of utilizing SOC is to have a scalable, reliable, and robust service discovery mechanism. However, traditional service discovery methods using centralized registries can easily suffer from problems such as performance bottleneck and vulnerability to failures in large scalable service networks, thus functioning abnormally. To address these problems, this paper proposes a peer-to-peer-based decentralized service discovery approach named Chord4S. Chord4S utilizes the data distribution and lookup capabilities of the popular Chord to distribute and discover services in a decentralized manner. Data availability is further improved by distributing published descriptions of functionally equivalent services to different successor nodes that are organized into virtual segments in the Chord4S circle. Based on the service publication approach, Chord4S supports QoS-aware service discovery. Chord4S also supports service discovery with wildcard(s). In addition, the Chord routing protocol is extended to support efficient discovery of multiple services with a single query. This enables late negotiation of Service Level Agreements (SLAs) between service consumers and multiple candidate service providers. The experimental evaluation shows that Chord4S achieves higher data availability and provides efficient query with reasonable overhead

Dataplane Specialization for High-performance OpenFlow Software Switching

OpenFlow is an amazingly expressive dataplane program- ming language, but this expressiveness comes at a severe performance price as switches must do excessive packet clas- sification in the fast path. The prevalent OpenFlow software switch architecture is therefore built on flow caching, but this imposes intricate limitations on the workloads that can be supported efficiently and may even open the door to mali- cious cache overflow attacks. In this paper we argue that in- stead of enforcing the same universal flow cache semantics to all OpenFlow applications and optimize for the common case, a switch should rather automatically specialize its dat- aplane piecemeal with respect to the configured workload. We introduce ES WITCH , a novel switch architecture that uses on-the-fly template-based code generation to compile any OpenFlow pipeline into efficient machine code, which can then be readily used as fast path. We present a proof- of-concept prototype and we demonstrate on illustrative use cases that ES WITCH yields a simpler architecture, superior packet processing speed, improved latency and CPU scala- bility, and predictable performance. Our prototype can eas- ily scale beyond 100 Gbps on a single Intel blade even with complex OpenFlow pipelines

Crime scripting: A systematic review

The file attached to this record is the author's final peer reviewed version.More than two decades after the publication of Cornish’s seminal work about the script-theoretic approach to crime analysis, this article examines how the concept has been applied in our community. The study provides evidence confirming that the approach is increasingly popular; and takes stock of crime scripting practices through a systematic review of over one hundred scripts published between 1994 and 2018. The results offer the first comprehensive picture of this approach, and highlights new directions for those interested in using data from cyber-systems and the Internet of Things to develop effective situational crime prevention measures

A DHT-Based Discovery Service for the Internet of Things

Current trends towards the Future Internet are envisaging the conception of novel services endowed with context-aware and autonomic capabilities to improve end users' quality of life. The Internet of Things paradigm is expected to contribute towards this ambitious vision by proposing models and mechanisms enabling the creation of networks of "smart things" on a large scale. It is widely recognized that efficient mechanisms for discovering available resources and capabilities are required to realize such vision. The contribution of this work consists in a novel discovery service for the Internet of Things. The proposed solution adopts a peer-to-peer approach for guaranteeing scalability, robustness, and easy maintenance of the overall system. While most existing peer-to-peer discovery services proposed for the IoT support solely exact match queries on a single attribute (i.e., the object identifier), our solution can handle multiattribute and range queries. We defined a layered approach by distinguishing three main aspects: multiattribute indexing, range query support, peer-to-peer routing. We chose to adopt an over-DHT indexing scheme to guarantee ease of design and implementation principles. We report on the implementation of a Proof of Concept in a dangerous goods monitoring scenario, and, finally, we discuss test results for structural properties and query performance evaluation

Considering Complex Search Techniques in DHTs Under Churn

Abstract-Traditionally complex queries have been performed over unstructured P2P networks by means of flooding, which is inherently inefficient due to the large number of redundant messages generated. While Distributed Hash Tables (DHTs) can provide very efficient look-up operations, they traditionally do not provide any methods for complex queries. By exploiting the structure inherent in DHTs we can perform complex querying over structured P2P networks by means of efficiently broadcasting the search query. This allows every node in the network to process the query locally, and hence is as powerful and flexible as flooding in unstructured networks, but without the inefficiency of redundant messages. While there have been various approaches proposed for broadcasting search queries over DHTs, the focus has not been on validation under churn. Comparing blind search methods for DHTs through simulation we see that churn, in particular nodes leaving the network, has a large impact on query success rate. In this paper we present novel results comparing blind search over Chord and Pastry while under varying levels of churn. We further consider how different data replication strategies can be used to enhance the query success rate

Istunnon aloitusprotokollaan pohjautuvat mobiilivertaisverkot

This work continues on my Master's Thesis work done between July 2005 and January 2006. In my Master's Thesis, we presented how a mobile peer-to-peer file-sharing application can be implemented using the Session Initiation Protocol (SIP) as the underlying signaling protocol. The main objective of this thesis is to evaluate what kind of special requirements mobile environment poses for peer-to-peer application design, and present how peer-to-peer based services can be efficiently realized in next-generation mobile networks by using SIP with some enhancements as the peer-to-peer signaling protocol. This thesis is divided into two parts. In the first part, we present different peer-to-peer architectures and search algorithms, and evaluate their suitability for mobile use. We also review some mobile peer-to-peer middleware and file-sharing applications. Then, in the second part, we present our hybrid mobile peer-to-peer architecture consisting of a Symbian based mobile client and a SIP Application Server based super-peer. Key findings of this thesis are that the mobile peer-to-peer application based on SIP signaling and hybrid peer-to-peer architecture is suitable for mobile use as it minimizes overhead in mobile nodes and allows mobile operator to have control on its users in multi-operator environment. Also, the performance of the application satisfies user requirements.Tämä työ on jatkoa diplomityölleni, joka tehtiin Heinäkuu 2005 – Tammikuu 2006 välisenä aikana. Diplomityössäni esitimme kuinka mobiilivertaisverkkosovellus voidaan toteuttaa käyttäen Session Initiation Protocol (SIP) protokollaa allaolevana signalointiprotokollana. Tämän työn päätavoite on selvittää, mitä erikoisvaatimuksia mobiiliympäristö vertaisverkkosovelluksen suunnittelulle asettaa sekä kuinka vertaisverkkopalveluita voidaan tehokkaasti toteuttaa seuraavan sukupolven mobiiliverkoissa käyttämällä laajennettua SIP protokollaa sovelluksen merkinantoprotokollana. Tämä työ on jaettu kahteen osaan. Ensimmäisessa osassa käsittelemme eri vertaisverkkoarkkitehtuureja ja hakualgoritmeja, sekä arvioimme näiden sopivuutta mobiilikäyttöön. Käymme myös läpi joitain mobiilivertaisverkkotiedostojako-ohjelmia sekä middleware-alustoja. Työn toisessa osassa esittelemme oman mobiilivertaisverkkoarkkitehtuurimme, joka koostuu Symbian mobiilisovelluksesta sekä SIP sovelluspalvelin super-peer solmusta. Tutkimuksen päälöydökset ovat seuraavat: SIP protokollaa käyttävä hybridi-vertaisverkkosovellus toimii hyvin matkapuhelinympäristössä, koska se minimoi puhelimeen kohdistuvan rasituksen ja tekee mahdolliseksi matkapuhelinoperaattorin hallita sovelluksen käyttäjiä myöskin monioperaattoriympäristössä. Tämän lisäksi ohjelmiston suorituskyky täyttää käytäjien sille asettamat vaatimukset

Sensitivity Analysis of Checkpointing Strategies for Multimemetic Algorithms on Unstable Complex Networks

The use of volatile decentralized computational platforms such as, e.g., peer-to-peer networks, is becoming an increasingly popular option to gain access to vast computing resources. Making an effective use of these resources requires algorithms adapted to such a changing environment, being resilient to resource volatility. We consider the use of a variant of evolutionary algorithms endowed with a classical fault-tolerance technique, namely the creation of checkpoints in a safe external storage. We analyze the sensitivity of this approach on different kind of networks (scale-free and small-world) and under different volatility scenarios. We observe that while this strategy is robust under low volatility conditions, in cases of severe volatility performance degrades sharply unless a high checkpoint frequency is used. This suggest that other fault-tolerance strategies are required in these situations.Universidad de Málaga, Campus de Excelencia Internacional Andalucía Tech. This work is partially supported by the MINECO project EphemeCH (TIN2014-56494-C4-1-P), by the Junta de Andalucía project DNEMESIS (P10-TIC-6083