From Pastry to CrossROAD: CROSS-layer Ring Overlay for AD hoc networks

Abstract
P2p systems for mobile ad hoc networks are currently an open research area. Most of the existent solutions were thought for the wired networks, where thousands of nodes participate to the same service, while ad hoc networks are generally characterized by limited dimensions and scarce resources. In this paper, a performance evaluation of a structured p2p system (Pastry), running on a real ad hoc network, will be presented, and a new optimized solution, called CrossROAD, will be defined. CrossROAD exploits a cross-layer architecture to reduce the communication overhead introduced by Pastry and, at the same time, maintains all the basic principles of structured overlay networks.
by Franca Delmastro

Analisa o Pastry numa rede ad hoc e mostra que ele não possui bom deseempenho neste cenário. Propõe uma solução cross-layer para contornar esse problema, o CrossROAD.

• Utiliza um protocolo de roteamento pró-ativo
• Conhece a topologia da rede inteira
• Uma rede sobreposta para cada serviço
• Tabela de roteamento informa também os serviços que cada nó possui
• Endereço lógico é um hash do IP
• Cada nós consegue construir a rede sobreposta individualmente
• Não há necessidade de realizar roteamento
• Nenhuma conexão remota é necessária para entrar na rede e nem no caso de deixarem a rede
• Não precisa ficar verificando se os nós estão vivos, protocolo de roteamento já faz isso

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MobileMAN: Design, Integration, and Experimentation of Cross-Layer Mobile Multihop Ad Hoc Networks

Abstract
In the previous article [1], via experimental studies, we have analyzed the performance of a TCP/IP layered architecture in multihop ad hoc networks. The experimental results point out that a legacy protocol stack does not operate efficiently in ad hoc networks, and cross layering is a promising approach to improve the performance. Cross layering opens a second phase in the ad hoc network design. In this article we present the cross-layer architecture and related protocols, developed in the MobileMAN project. By implementing a full prototype of this architecture, we show that it significantly outperforms a legacy TCP/IP layered architecture.

A idéia do artigo é introduzir uma camada vertical (NeSt - Network Status) que server como um respositório de informação. Cada camada programa uma interface do modelo convencional de camadas e uma interface com a NeSt, assim mantem-se a modularidade das camadas e é possível usar informação cross-layer. Protocolos que não usam a NeSt funcionam da maneira convencional.

Trechos interessantes

• The basic idea behind this technique is to make information produced/collected by a protocol available to the whole protocol stack, so as to enable optimizations and improve network performance.
• At one end, solutions based on layer triggers implement interdependencies between protocols maintaining compatibility with strict layering. In this case the information exchange is limited to adjacent protocols. A full cross-layer design represents the other extreme; it introduces stackwide layers’ interdependencies that enable the optimization of each protocol’s performance by exploiting the full knowledge of the network status collected at different layers of the protocol stack.