Roteamento utilizando potencial de entrega em redes tolerantes a atrasos

• Ano de defesa: 2010
• Autor(a) principal: Nunes, Cristina Moreira
• Orientador(a): Dotti, Fernando Luís
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Pontifícia Universidade Católica do Rio Grande do Sul; Porto Alegre
• Palavras-chave em Português: INFORMÁTICA; REDES DE COMPUTADORES; ROTEAMENTO - REDES DE COMPUTADORES; PROTOCOLOS DE APLICAÇÃO SEM FIO (PROTOCOLOS DE REDE DE COMPUTAÇÃO)
• Link de acesso: http://hdl.handle.net/10923/1675

Delay Tolerant Network (DTN) are networks in which frequent interruptions, high delay, and high error rates may occur. In these networks the nodes are mobile and play the role of routers, storing and transferring messages that need to be delivered. This thesis consider the stochastic DTN, where the topological changes are not known in advance and techniques are proposed that try to increase the probability of success in the routing, using, for instance, historical knowledge of network behavior in the routing decision. DTN has some similarities to ad hoc networks, but due to frequent disruptions that occur in DTN, the routing problem is handled differently. In sparse scenarios, due to lack of connectivity of nodes, DTN has higher percentage of delivered messages, at the price of higher delays. A study comparing these two kinds of networks is carried out by this thesis, providing quantitative information about this aspect. This work proposes three variations of a routing protocol for stochastic DTN based on a metric called “delivery potential”, which is used while deciding how messages are forwarded. The delivery potential is a historical measure that indicates the number of meetings in which the nodes are involved in a period of time. In order to increase the probability to find the destination, the strategy gives priority to routing nodes that have a high number of meetings. The initial protocol is called ARPR (Adaptive Potential Routing Protocol) and, in comparison with other protocols for the same type of network, presents a percentage of delivered messages equivalent to these protocols, with a very low overhead, especially for sparse networks (important in DTN).An APRP variation uses an acknowledgement mechanism for messages already delivered in order to release space in buffer for new messages. This variation is called APRP-Ack and has better performance than ARPR, despite causing an increase in the average delay in the delivery of messages. Finally, the APRP-Group is proposed, in order to reduce the delay generated by APRP-Ack. The APRP-Group seeks to identify groups of nodes with similar delivery potential and decide on the forwarding of messages based on these groups. This protocol provides a significant reduction in the delivery delay, compared to APRP and APRP-Ack, maintaining low costs of communication and maintaining or improving levels of delivery. The above mentioned proposed protocols where evaluated using a DTN specific simulation environment specific and compared to analogous protocols from the literature, specially with the Spray and Wait due to its high performance reported in the literature.