Um escalonador de pacotes para o protocolo MPQUIC apoiado na similaridade dos caminhos

Orientador: Michele Nogueira LimaDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Informática. Defesa : Curitiba, 16/09/2019Inclui referências: p. 73-79Área de concentração: Ciência da ComputaçãoResumo: Os servicos Web evoluiram significativamente desde o seu inicio no final dos anos 80. Ao longo dos anos, estes servicos aumentaram em numero, tamanho e complexidade. Alem disso, novos servicos como aqueles de streaming, os jogos online e a realidade virtual demandam cada vez mais recursos devido as exigencias dos usuarios e a concorrencia entre as plataformas que disponibilizam estes servicos. Em geral, estes servicos sao sensiveis as falhas e a latencia da rede. Garantir a entrega de pacotes de maneira confiavel e uma das principais funcoes da camada de transporte. Contudo, os protocolos de transporte dominantes na Internet, como o protocolo TCP e UDP, possuem limitacoes e sao dificeis de serem atualizados, justamente pela sua alta utilizacao. Em face disso, a empresa Google desenvolveu o protocolo de transporte QUIC (Quick UDP Internet Connection) e um grupo de trabalho do IETF trata da sua padronizacao. O protocolo QUIC e fundamentado no protocolo UDP e sua proposta e substituir o conjunto de protocolos da Web formado pelos protocolos HTTP/TLS/TCP. O protocolo QUIC traz beneficios ao reduzir a latencia da conexao por se abster do processo de estabelecimento de conexao (three-way handshake) na maioria de suas conexoes, alem de aumentar a seguranca durante a comunicacao ao criptografar todos os seus pacotes e parte das informacoes contidas no cabecalho de seus segmentos. Em pesquisas realizadas pela empresa Google, o protocolo QUIC diminui 3% o tempo medio de carregamento na pagina de pesquisa da empresa, quando comparado ao protocolo TCP. Contudo, estes valores tendem a crescer com o uso simultaneo das multiplas interfaces de rede disponiveis nos dispositivos dos usuarios. Visando a este objetivo, outro grupo de trabalho do IETF impulsiona o desenvolvimento do protocolo QUIC sobre multicaminhos. O protocolo QUIC Multicaminhos (MPQUIC) apresenta vantagem no uso das multiplas interfaces de rede disponiveis com o intuito de aumentar o desempenho e a disponibilidade dos servicos. Entretanto, o uso de varios caminhos simultaneamente resulta em desafios relacionados a diversidade e a heterogeneidade da rede. Um desses desafios e a entrega de pacotes fora de ordem (ou o problema de reordenamento), que ocorre devido a estas adversidades. As abordagens na literatura destinadas a mitigacao do problema de reordenamento, direcionam suas propostas ao escalonador de pacotes, que e um dos principais componentes dos protocolos multicaminhos e emprega um importante papel no desempenho da transmissao, pois ele e o responsavel pela selecao e alocacao de dados nos diferentes caminhos disponiveis para a comunicacao entre cliente e servidor. Sendo assim, este trabalho apresenta o escalonador STOUT (do ingles, Similarity againsT packets OUT-of-order) que visa reduzir os efeitos da heterogeneidade dos caminhos ao seleciona-los baseando-se na similaridade de suas caracteristicas. Em testes realizados, o escalonador STOUT demonstrou melhor desempenho quando comparado ao escalonador padrao do protocolo MPQUIC, alem de diminuir o tempo em que os pacotes aguardam para reordenacao. Palavras-chave: Transmissao Multicaminhos, Escalonador, MPQUIC, QUIC, Reordenamento de Pacotes, DesempenhoAbstract: Web services have evolved significantly since their conception in the late 1980s. Over the years, these services have increased in number, size and complexity. In addition, new services, such as streaming services, online games, and virtual reality, are increasingly demanding resources due to user requests and competition among the platforms that provide these services. In general, these services are sensitive to network failures and latency. Ensuring reliable delivery of packages is one of the key functions of the transport layer. However, dominant Internet transport protocols, such as the TCP and UDP protocol, have limitations and are difficult to be updated due to their high utilization. Given these facts, Google has developed Quick UDP Internet Connection (QUIC) transport protocol and an IETF working group addresses its standardization. The QUIC protocol is based on the UDP protocol and its purpose is to replace the web protocol set formed by the HTTP/TLS/TCP protocols. The QUIC protocol has benefits in reducing connection latency by refraining from the three-way-handshake process on most of your connections, as well as increasing security during communication by encrypting all your connections, packets and part of the information contained in the header of their segments. In researches by Google, the QUIC protocol decreases the average load time on the company's search page by 3% compared to the TCP protocol. However, these values tend to grow with the simultaneous use of multiple network interfaces available on user devices. Towards this end, another IETF working group drives the development of the multipath QUIC protocol. The multipath QUIC (MPQUIC) protocol has the advantage of using the multiple network interfaces available to increase performance and service availability. However, using multiple paths simultaneously results in challenges related to network diversity and heterogeneity. One of these challenges is the delivery of out-of-order packages (or the reordering problem), which occurs because of these adversities. Approaches in the literature aimed at mitigating the reordering problem directing their proposals to the packet scheduler, which is a major component of multipath protocols and plays an important role in transmission performance as it is responsible for data selection and allocation through different paths available for client-server communication. Thus, this work presents the scheduler named Similarity againsT packets OUT-of-order (STOUT) which aims to reduce the effects of path heterogeneity by selecting them based on the similarity of their characteristics. In tests performed, the STOUT scheduler has shown better performance compared to the standard MPQUIC protocol scheduler, as well as decreasing the time packets wait for reordering. Keywords: Multipath Transmission, Scheduler, MPQUIC, QUIC, Packet Reordering, Performanc

Cooperative End-to-end Congestion Control in Heterogeneous Wireless Networks

Sharing the resources of multiple wireless networks with overlapped coverage areas has a potential of improving the transmission throughput. However, in the existing frameworks, the improvement cannot be achieved in congestion scenarios because of independent congestion control procedures among the end-to-end paths. Although various network characteristics make the congestion control complex, this variety can be useful in congestion avoidance if the networks cooperate with each other. When congestion happens in an end-to-end path, it is inevitable to have a packet transmission rate less than the minimum requested rate due to congestion window size adjustments. Cooperation among networks can help to avoid this problem for better service quality. When congestion is predicted for one path, some of the on-going packets can be sent over other paths instead of the congested path. In this way, the traffic can be shifted from a congested network to others, and the overall transmission throughput does not degrade in a congestion scenario. However, cooperation is not always advantageous since the throughput of cooperative transmission in an uncongested scenario can be less than that of non-cooperative transmission due to cooperation costs such as cooperation setup time, additional signalling for cooperation, and out-of-order packet reception. In other words, a trade-off exists between congestion avoidance and cooperation cost. Thus, cooperation should be triggered only when it is beneficial according to congestion level measurements. In this research, our aim is to develop an efficient cooperative congestion control scheme for a heterogeneous wireless environment. To this end, a cooperative congestion control algorithm is proposed, in which the state of an end-to-end path is provided at the destination terminal by measuring the queuing delay and estimating the congestion level. The decision on when to start/stop cooperation is made based on the network characteristics, instantaneous traffic condition, and the requested quality of service (QoS). Simulation results demonstrate the throughput improvement of the proposed scheme over non-cooperative congestion control.1 yea

Network Performance Improvements for Low-Latency Anonymity Networks

While advances to the Internet have enabled users to easily interact and exchange information online, they have also created several opportunities for adversaries to prey on users’ private information. Whether the motivation for data collection is commercial, where service providers sell data for marketers, or political, where a government censors, blocks and tracks its people, or even personal, for cyberstalking purposes, there is no doubt that the consequences of personal information leaks can be severe. Low-latency anonymity networks have thus emerged as a solution to allow people to surf the Internet without the fear of revealing their identities or locations. In order to provide anonymity to users, anonymity networks route users’ traffic through several intermediate relays, which causes unavoidable extra delays. However, although these networks have been originally designed to support interactive applications, due to a variety of design weaknesses, these networks offer anonymity at the expense of further intolerable performance costs, which disincentivize users from adopting these systems. In this thesis, we seek to improve the network performance of low-latency anonymity networks while maintaining the anonymity guarantees they provide to users today. As an experimentation platform, we use Tor, the most widely used privacy-preserving network that empowers people with low-latency anonymous online access. Since its introduction in 2003, Tor has successfully evolved to support hundreds of thousands of users using thousands of volunteer-operated routers run all around the world. Incidents of sudden increases in Tor’s usage, coinciding with global political events, confirm the importance of the Tor network for Internet users today. We identify four key contributors to the performance problems in low-latency anonymity networks, exemplified by Tor, that significantly impact the experience of low-latency application users. We first consider the lack of resources problem due to the resource-constrained routers, and propose multipath routing and traffic splitting to increase throughput and improve load balancing. Second, we explore the poor quality of service problem, which is exacerbated by the existence of bandwidth-consuming greedy applications in the network. We propose online traffic classification as a means of enabling quality of service for every traffic class. Next, we investigate the poor transport design problem and propose a new transport layer design for anonymous communication networks which addresses the drawbacks of previous proposals. Finally, we address the problem of the lack of congestion control by proposing an ATM-style credit-based hop-by-hop flow control algorithm which caps the queue sizes and allows all relays to react to congestion in the network. Our experimental results confirm the significant performance benefits that can be obtained using our privacy-preserving approaches