QuickCast: Fast and Efficient Inter-Datacenter Transfers using Forwarding Tree Cohorts

Large inter-datacenter transfers are crucial for cloud service efficiency and are increasingly used by organizations that have dedicated wide area networks between datacenters. A recent work uses multicast forwarding trees to reduce the bandwidth needs and improve completion times of point-to-multipoint transfers. Using a single forwarding tree per transfer, however, leads to poor performance because the slowest receiver dictates the completion time for all receivers. Using multiple forwarding trees per transfer alleviates this concern--the average receiver could finish early; however, if done naively, bandwidth usage would also increase and it is apriori unclear how best to partition receivers, how to construct the multiple trees and how to determine the rate and schedule of flows on these trees. This paper presents QuickCast, a first solution to these problems. Using simulations on real-world network topologies, we see that QuickCast can speed up the average receiver's completion time by as much as $10\times$ while only using $1.04\times$ more bandwidth; further, the completion time for all receivers also improves by as much as $1.6\times$ faster at high loads.Comment: [Extended Version] Accepted for presentation in IEEE INFOCOM 2018, Honolulu, H

Online Multicast Traffic Engineering for Software-Defined Networks

Previous research on SDN traffic engineering mostly focuses on static traffic, whereas dynamic traffic, though more practical, has drawn much less attention. Especially, online SDN multicast that supports IETF dynamic group membership (i.e., any user can join or leave at any time) has not been explored. Different from traditional shortest-path trees (SPT) and graph theoretical Steiner trees (ST), which concentrate on routing one tree at any instant, online SDN multicast traffic engineering is more challenging because it needs to support dynamic group membership and optimize a sequence of correlated trees without the knowledge of future join and leave, whereas the scalability of SDN due to limited TCAM is also crucial. In this paper, therefore, we formulate a new optimization problem, named Online Branch-aware Steiner Tree (OBST), to jointly consider the bandwidth consumption, SDN multicast scalability, and rerouting overhead. We prove that OBST is NP-hard and does not have a $|D_{max}|^{1-\epsilon}$-competitive algorithm for any $\epsilon >0$, where $|D_{max}|$ is the largest group size at any time. We design a $|D_{max}|$-competitive algorithm equipped with the notion of the budget, the deposit, and Reference Tree to achieve the tightest bound. The simulations and implementation on real SDNs with YouTube traffic manifest that the total cost can be reduced by at least 25% compared with SPT and ST, and the computation time is small for massive SDN.Comment: Full version (accepted by INFOCOM 2018

Comunicação Anycast em redes definidas por software

Dissertação de mestrado integrado em Engenharia de Telecomunicações e InformáticaA comunicação Anycast (um para um de muitos) é um novo paradigma que tem sido usada na prática para pelo menos um serviço crítico na Internet: o DNS. Tal como o multicast (um para muitos), este paradigma utiliza o conceito de grupo, mas a informação é enviada apenas para um dos membros do grupo que esteja em melhor condições (tipicamente o mais próximo), em vez de sempre para todos. As Redes Definidas por Software (SDN) têm sido apontadas como um novo paradigma de redes que permite facilmente projetar, desenvolver e implementar uma rede. Esta arquitetura separa o plano de controlo do plano de dados de uma rede. O plano de controlo é puramente desenvolvido em software e o plano de dados em hardware. As redes baseadas na arquitetura SDN ganharam maior destaque a partir da especificação do protocolo OpenFlow. Este protocolo centraliza o controlo da tabela de fluxos dos dispositivos de rede num controlador externo e flexível, e fornece um protocolo seguro para facilitar a comunicação entre os controladores e switches. Nesta dissertação propõe-se uma estratégia de encaminhamento Anycast, adequada a Redes Definidas por Software (SDN), e que tem em conta métricas de Qualidade de Serviço (QoS). A largura de banda disponível foi escolhida como métrica QoS com o objetivo de mostrar que o seu uso no cálculo de caminhos Anycast permite efetivamente melhorar o desempenho global da rede, com melhor aproveitamento dos recursos disponíveis. A estratégia proposta foi implementada em Python, na forma de um novo componente do controlador POX, e testada em ambiente laboratorial usando o emulador Mininet. No cenário de teste foi usada uma topologia gerada automaticamente, na qual se cria um grupo Anycast com um conjunto de servidores escolhidos aleatoriamente. O controlador recolhe informação de largura de banda disponível em todos os links da topologia e calcula árvores de entrega Anycast por servidor com base nessa métrica, para todos os clientes, usando o algoritmo de Prim. Os resultados obtidos mostram que esta estratégia permite aumentar a largura de banda usada na comunicação Anycast, quando comparada com uma estratégia baseada apenas nos caminhos mais curtos.Anycast communication (one for one of many) is a new paradigm that has been used in practice for at least one critical Internet service: DNS. Like multicast (one for many), this paradigm uses the concept of a group of systems, but the information is sent only to one of the members of the group that is in best conditions (typically the nearest), rather than always for everyone. Software Defined Networks (SDN) have been identified as a new network paradigm that allows to easily design, develop and implement a network. This architecture separates the control plane from the data plane of a network. The control plan is developed purely in software and the data plan in hardware. Networks based on this SDN architecture gained greater prominence after the specification of the OpenFlow protocol. This protocol centralizes the control of the flow tables of all network devices in an external and flexible controller, and provides a secure protocol to facilitate communication between controllers and switches. This dissertation proposes an Anycast routing strategy, suitable for Software Defined Networks (SDN), which takes into account Quality of Service (QoS) metrics. The available bandwidth was chosen as a QoS metric, in order to show that its use in Anycast path calculations effectively improves the overall performance of the network, with a better use of the available resources. The proposed strategy was implemented in Python, in the form of a new POX controller component, and tested in a laboratory environment using the Mininet emulator. In the test scenario, an automatically generated topology was used in which an Anycast group was created with a set of servers chosen at random. The controller collects available bandwidth information on all topology links and calculates Anycast delivery trees per server based on this metric, for all clients, using the Prim algorithm. The results show that this strategy allows to increase the bandwidth used in Anycast communication, when compared to a strategy based only on the shortest paths

Resilient and Scalable Forwarding for Software-Defined Networks with P4-Programmable Switches

Traditional networking devices support only fixed features and limited configurability. Network softwarization leverages programmable software and hardware platforms to remove those limitations. In this context the concept of programmable data planes allows directly to program the packet processing pipeline of networking devices and create custom control plane algorithms. This flexibility enables the design of novel networking mechanisms where the status quo struggles to meet high demands of next-generation networks like 5G, Internet of Things, cloud computing, and industry 4.0. P4 is the most popular technology to implement programmable data planes. However, programmable data planes, and in particular, the P4 technology, emerged only recently. Thus, P4 support for some well-established networking concepts is still lacking and several issues remain unsolved due to the different characteristics of programmable data planes in comparison to traditional networking. The research of this thesis focuses on two open issues of programmable data planes. First, it develops resilient and efficient forwarding mechanisms for the P4 data plane as there are no satisfying state of the art best practices yet. Second, it enables BIER in high-performance P4 data planes. BIER is a novel, scalable, and efficient transport mechanism for IP multicast traffic which has only very limited support of high-performance forwarding platforms yet. The main results of this thesis are published as 8 peer-reviewed and one post-publication peer-reviewed publication. The results cover the development of suitable resilience mechanisms for P4 data planes, the development and implementation of resilient BIER forwarding in P4, and the extensive evaluations of all developed and implemented mechanisms. Furthermore, the results contain a comprehensive P4 literature study. Two more peer-reviewed papers contain additional content that is not directly related to the main results. They implement congestion avoidance mechanisms in P4 and develop a scheduling concept to find cost-optimized load schedules based on day-ahead forecasts