28 research outputs found
Structured Peer-to-Peer Overlay Deployment on MANET: A Survey
There are many common characteristics between Peer-to-Peer (P2P) overlay networks and Mobile Ad-hoc Networks (MANET). Self-organization, decentralization, dynamicity and changing topology are the most shared features. Furthermore, when used together, the two approaches complement each other. P2P overlays provide data storage/retrieval functionality, and their routing information can complement that of MANET. MANET provides wireless connectivity between clients without depending on any pre-existing infrastructure. The aim of this paper is to survey current P2P over MANET systems. Specifically, this paper focuses on and investigates structured P2P over MANET. Overall, more than thirty distinct approaches have been classified into groups and introduced in tables providing a structured overview of the area. The survey addresses the identified approaches in terms of P2P systems, MANET underlay systems and the performance of the reviewed systems
A one hop overlay system for Mobile Ad Hoc Networks
Peer-to-Peer (P2P) overlays were initially proposed for use with wired networks.
However, the very rapid proliferation of wireless communication technology has
prompted a need for adoption of P2P systems in mobile networks too. There are
many common characteristics between P2P overlay networks and Mobile Ad-hoc
Networks (MANET). Self-organization, decentralization, a dynamic nature and
changing topology are the most commonly shared features. Furthermore, when
used together, the two approaches complement each other. P2P overlays provide
data storage/retrieval functionality and MANET provides wireless connectivity
between clients without depending on any pre-existing infrastructure. P2P overlay
networks can be deployed over MANET to address content discovery issues.
However, previous research has shown that deploying P2P systems straight over
MANET does not exhibit satisfactory performance. Bandwidth limitation, limited
resources and node mobility are some of the key constraints.
This thesis proposes a novel approach, OneHopOverlay4MANET, to exploit the
synergies between MANET and P2P overlays through cross-layering. It combines
Distributed Hash Table (DHT) based structured P2P overlays with MANET underlay
routing protocols to achieve one logical hop between any pair of overlay
nodes. OneHopOverlay4MANET constructs a cross-layer channel to permit direct
exchange of routing information between the Application layer, where the overlay
operates, and the MANET underlay layer. Consequently, underlay routing information
can be shared and used by the overlay. Thus, OneHopOverlay4MANET
reduces the typical management traffic when deploying traditional P2P systems
over MANET. Moreover, as a result of building one hop overlay, OneHopOverlay4MANET
can eliminate the mismatching issue between overlay and underlay
and hence resolve key lookups in a short time, enhancing the performance of the
overlay.
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In this thesis, we present OneHopOverlay4MANET and evaluate its performance
when combined with different underlay routing protocols. OneHopOverlay4MANET
has been combined with two proactive underlays (OLSR and BATMAN)
and with three reactive underlay routing protocols (DSR, AODV and
DYMO). In addition, the performance of the proposed system over OLSR has
been compared to two recent structured P2P over MANET systems (MA-SP2P
and E-SP2P) that adopted OLSR as the routing protocol. The results show that
better performance can be achieved using OneHopOverlay4MANET
A membership management protocol for mobile P2P networks
MANETs are self-organizing networks composed of mobile wireless nodes with often scarce resources. Distributed applications based on the P2P paradigm are the best candidates to run over such networks. To profit from the service provided by a P2P overlay (e.g. file sharing using BitTorrent), a node needs to be permanently informed about the other members of the overlay (e.g. other peers interested in the same file as currently provided by the BitTorrent central tracker). This P2P membership management is a costly and difficult task in such dynamic and resource limited environment. We focus on this problem and we propose a robust, network friendly and decentralized membership management protocol allowing peer discovery and update. Compared to flooding, client-server or multicast based approaches, our protocol achieves significantly lower network overhead and lower pollution of caches caused by peers who have left. Moreover, as network splits are very frequent in MANETs, our protocol is designed to be partition-aware. Namely, it allows separate overlays providing the same service to efficiently merge together when communication opportunities occur. The efficiency of our solution is validated through extensive NS-2 simulations
Towards Securing Peer-to-peer SIP in the MANET Context: Existing Work and Perspectives
The Session Initiation Protocol (SIP) is a key building block of many social applications, including VoIP communication and instant messaging. In its original architecture, SIP heavily relies on servers such as proxies and registrars. Mobile Ad hoc NETworks (MANETs) are networks comprised of mobile devices that communicate over wireless links, such as tactical radio networks or vehicular networks. In such networks, no fixed infrastructure exists and server-based solutions need to be redesigned to work in a peer-to-peer fashion. We survey existing proposals for the implementation of SIP over such MANETs and analyze their security issues. We then discuss potential solutions and their suitability in the MANET context
Effects of Data Replication on Data Exfiltration in Mobile Ad hoc Networks Utilizing Reactive Protocols
A swarm of autonomous UAVs can provide a significant amount of ISR data where current UAV assets may not be feasible or practical. As such, the availability of the data the resides in the swarm is a topic that will benefit from further investigation. This thesis examines the impact of le replication and swarm characteristics such as node mobility, swarm size, and churn rate on data availability utilizing reactive protocols. This document examines the most prominent factors affecting the networking of nodes in a MANET. Factors include network routing protocols and peer-to-peer le protocols. It compares and contrasts several open source network simulator environments. Experiment implementation is documented, covering design considerations, assumptions, and software implementation, as well as detailing constant, response and variable factors. Collected data is presented and the results show that in swarms of sizes of 30, 45, and 60 nodes, le replication improves data availability until network saturation is reached, with the most significant benefit gained after only one copy is made. Mobility, churn rate, and swarm density all influence the replication impact
Data Storage and Dissemination in Pervasive Edge Computing Environments
Nowadays, smart mobile devices generate huge amounts of data in all sorts of gatherings.
Much of that data has localized and ephemeral interest, but can be of great use if shared
among co-located devices. However, mobile devices often experience poor connectivity,
leading to availability issues if application storage and logic are fully delegated to a
remote cloud infrastructure. In turn, the edge computing paradigm pushes computations
and storage beyond the data center, closer to end-user devices where data is generated
and consumed. Hence, enabling the execution of certain components of edge-enabled
systems directly and cooperatively on edge devices.
This thesis focuses on the design and evaluation of resilient and efficient data storage
and dissemination solutions for pervasive edge computing environments, operating with
or without access to the network infrastructure. In line with this dichotomy, our goal can
be divided into two specific scenarios. The first one is related to the absence of network
infrastructure and the provision of a transient data storage and dissemination system
for networks of co-located mobile devices. The second one relates with the existence of
network infrastructure access and the corresponding edge computing capabilities.
First, the thesis presents time-aware reactive storage (TARS), a reactive data storage
and dissemination model with intrinsic time-awareness, that exploits synergies between
the storage substrate and the publish/subscribe paradigm, and allows queries within a
specific time scope. Next, it describes in more detail: i) Thyme, a data storage and dis-
semination system for wireless edge environments, implementing TARS; ii) Parsley, a
flexible and resilient group-based distributed hash table with preemptive peer relocation
and a dynamic data sharding mechanism; and iii) Thyme GardenBed, a framework
for data storage and dissemination across multi-region edge networks, that makes use of
both device-to-device and edge interactions.
The developed solutions present low overheads, while providing adequate response
times for interactive usage and low energy consumption, proving to be practical in a
variety of situations. They also display good load balancing and fault tolerance properties.Resumo
Hoje em dia, os dispositivos móveis inteligentes geram grandes quantidades de dados
em todos os tipos de aglomerações de pessoas. Muitos desses dados têm interesse loca-
lizado e efêmero, mas podem ser de grande utilidade se partilhados entre dispositivos
co-localizados. No entanto, os dispositivos móveis muitas vezes experienciam fraca co-
nectividade, levando a problemas de disponibilidade se o armazenamento e a lógica das
aplicações forem totalmente delegados numa infraestrutura remota na nuvem. Por sua
vez, o paradigma de computação na periferia da rede leva as computações e o armazena-
mento para além dos centros de dados, para mais perto dos dispositivos dos utilizadores
finais onde os dados são gerados e consumidos. Assim, permitindo a execução de certos
componentes de sistemas direta e cooperativamente em dispositivos na periferia da rede.
Esta tese foca-se no desenho e avaliação de soluções resilientes e eficientes para arma-
zenamento e disseminação de dados em ambientes pervasivos de computação na periferia
da rede, operando com ou sem acesso à infraestrutura de rede. Em linha com esta dico-
tomia, o nosso objetivo pode ser dividido em dois cenários específicos. O primeiro está
relacionado com a ausência de infraestrutura de rede e o fornecimento de um sistema
efêmero de armazenamento e disseminação de dados para redes de dispositivos móveis
co-localizados. O segundo diz respeito à existência de acesso à infraestrutura de rede e
aos recursos de computação na periferia da rede correspondentes.
Primeiramente, a tese apresenta armazenamento reativo ciente do tempo (ARCT), um
modelo reativo de armazenamento e disseminação de dados com percepção intrínseca
do tempo, que explora sinergias entre o substrato de armazenamento e o paradigma pu-
blicação/subscrição, e permite consultas num escopo de tempo específico. De seguida,
descreve em mais detalhe: i) Thyme, um sistema de armazenamento e disseminação de
dados para ambientes sem fios na periferia da rede, que implementa ARCT; ii) Pars-
ley, uma tabela de dispersão distribuída flexível e resiliente baseada em grupos, com
realocação preventiva de nós e um mecanismo de particionamento dinâmico de dados; e
iii) Thyme GardenBed, um sistema para armazenamento e disseminação de dados em
redes multi-regionais na periferia da rede, que faz uso de interações entre dispositivos e
com a periferia da rede.
As soluções desenvolvidas apresentam baixos custos, proporcionando tempos de res-
posta adequados para uso interativo e baixo consumo de energia, demonstrando serem
práticas nas mais diversas situações. Estas soluções também exibem boas propriedades de balanceamento de carga e tolerância a faltas
Distributed resource discovery: architectures and applications in mobile networks
As the amount of digital information and services increases, it becomes increasingly important to be able to locate the desired content. The purpose of a resource discovery system is to allow available resources (information or services) to be located using a user-defined search criterion. This work studies distributed resource discovery systems that guarantee all existing resources to be found and allow a wide range of complex queries. Our goal is to allocate the load uniformly between the participating nodes, or alternatively to concentrate the load in the nodes with the highest available capacity.
The first part of the work examines the performance of various existing unstructured architectures and proposes new architectures that provide features especially valuable in mobile networks. To reduce the network traffic, we use indexing, which is particularly useful in scenarios, where searches are frequent compared to resource modifications. The ratio between the search and update frequencies determines the optimal level of indexing. Based on this observation, we develop an architecture that adjusts itself to changing network conditions and search behavior while maintaining optimal indexing. We also propose an architecture based on large-scale indexing that we later apply to resource sharing within a user group. Furthermore, we propose an architecture that relieves the topology constraints of the Parallel Index Clustering architecture. The performance of the architectures is evaluated using simulation.
In the second part of the work we apply the architectures to two types of mobile networks: cellular networks and ad hoc networks. In the cellular network, we first consider scenarios where multiple commercial operators provide a resource sharing service, and then a scenario where the users share resources without operator support. We evaluate the feasibility of the mobile peer-to-peer concept using user opinion surveys and technical performance studies. Based on user input we develop access control and group management algorithms for peer-to-peer networks. The technical evaluation is performed using prototype implementations. In particular, we examine whether the Session Initiation Protocol can be used for signaling in peer-to-peer networks. Finally, we study resource discovery in an ad hoc network. We observe that in an ad hoc network consisting of consumer devices, the capacity and mobility among nodes vary widely. We utilize this property in order to allocate the load to the high-capacity nodes, which serve lower-capacity nodes. We propose two methods for constructing a virtual backbone connecting the nodes
Estabelecimento de redes de comunidades sobreponíveis
Doutoramento em Engenharia InformáticaUma das áreas de investigação em Telecomunicações de interesse crescente
prende-se com os futuros sistemas de comunicações móveis de 4a geração
e além destes. Nos últimos anos tem sido desenvolvido o conceito de redes
comunitárias, no qual os utilizadores se agregam de acordo com interesses
comuns. Estes conceitos têm sido explorados de uma forma horizontal em
diferentes camadas da comunicação, desde as redes comunitárias de comunicação
(Seattle Wireless ou Personal Telco, p.ex.) até às redes de interesses
peer-to-peer. No entanto, estas redes são usualmente vistas como redes de
overlay, ou simplesmente redes de associação livre. Na prática, a noção de
uma rede auto-organizada, completamente orientada ao serviço/comunidade,
integralmente suportada em termos de arquitetura, não existe. Assim este
trabalho apresenta uma realização original nesta área de criação de redes
comunitárias, com uma arquitetura subjacente orientada a serviço, e que suporta
integralmente múltiplas redes comunitárias no mesmo dispositivo, com
todas as características de segurança, confiança e disponibilização de serviço
necessárias neste tipo de cenários (um nó pode pertencer simultaneamente
a mais do que uma rede comunitária). Devido à sua importância para
os sistemas de redes comunitárias, foi dado particular atenção a aspetos de
gestão de recursos e controlo de acessos. Ambos realizados de uma forma
descentralizada e considerando mecanismos dotados de grande escalabilidade.
Para isso, é apresentada uma linguagem de políticas que suporta a
criação de comunidades virtuais. Esta linguagem não é apenas utilizada para
o mapeamento da estrutura social dos membros da comunidade, como para,
gerir dispositivos, recursos e serviços detidos pelos membros, de uma forma
controlada e distribuída.One of the research areas with increasing interest in the field of telecommunications,
are the ones related to future telecommunication systems, both 4th
generation and beyond. In parallel, during the last years, several concepts
have been developed related to clustering of users according to their interested,
in the form of community networks. Solutions proposed for these concepts
tackle the challenges horizontally, for each layer of the communication
stack, ranging from community based communication networks (e.g. Seattle
Wireless, or Personal Telco), to interest networks based on peer-to-peer protocols.
However, these networks are presented either as free joining, or overlay
networks. In practice, the notion of a self-organized, service and community
oriented network, with these principles embedded in its design principles, is
yet to be developed. This work presents an novel instantiation of a solution in
the area of community networks, with a underlying architecture which is fully
service oriented, and envisions the support for multiple community networks
in the same device. Considerations regarding security, trust and service availability
for this type of environments are also taken. Due to the importance of
resource management and access control, in the context of community driven
communication networks, a special focus was given to the support of scalable
and decentralized management and access control methods. For this
purpose, it is presented a policy language which supports the creation and
management of virtual communities. The language is not only used for mapping
the social structure of the community members, but also to, following
a distributed approach, manage devices, resources and services owned by
each community member
Private and censorship-resistant communication over public networks
Society’s increasing reliance on digital communication networks is creating unprecedented opportunities for wholesale
surveillance and censorship. This thesis investigates the use of public networks such as the Internet to build
robust, private communication systems that can resist monitoring and attacks by powerful adversaries such as national
governments.
We sketch the design of a censorship-resistant communication system based on peer-to-peer Internet overlays in which
the participants only communicate directly with people they know and trust. This ‘friend-to-friend’ approach protects
the participants’ privacy, but it also presents two significant challenges. The first is that, as with any peer-to-peer
overlay, the users of the system must collectively provide the resources necessary for its operation; some users might
prefer to use the system without contributing resources equal to those they consume, and if many users do so, the
system may not be able to survive.
To address this challenge we present a new game theoretic model of the problem of encouraging cooperation between
selfish actors under conditions of scarcity, and develop a strategy for the game that provides rational incentives for
cooperation under a wide range of conditions.
The second challenge is that the structure of a friend-to-friend overlay may reveal the users’ social relationships to
an adversary monitoring the underlying network. To conceal their sensitive relationships from the adversary, the
users must be able to communicate indirectly across the overlay in a way that resists monitoring and attacks by other
participants.
We address this second challenge by developing two new routing protocols that robustly deliver messages across
networks with unknown topologies, without revealing the identities of the communication endpoints to intermediate
nodes or vice versa. The protocols make use of a novel unforgeable acknowledgement mechanism that proves that a
message has been delivered without identifying the source or destination of the message or the path by which it was
delivered. One of the routing protocols is shown to be robust to attacks by malicious participants, while the other
provides rational incentives for selfish participants to cooperate in forwarding messages