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Optimization of routing and wireless resource allocation in hybrid data center networks
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The high proliferation of smart devices and online services allows billions of users to connect with network while deploying a vast range of applications. Particularly, with the advent of the future 5G technology, it is expected that a tremendous mobile and data traffic will be crossing Internet network. In this regard, Cloud service providers are urged to rethink their data center architectures in order to cope with this unprecedented traffic explosion. Unfortunately, the conventional wired infrastructures struggle to resist to such a traffic growth and become prone to serious congestion problems. Therefore, new innovative techniques are required. In this thesis, we investigate a recent promising approach that augments the wired Data Center Network (DCN) with wireless communications. Indeed, motivated by the feasibility of the new emerging 60 GHz technology, offering an impressive data rate (≈ 7 Gbps), we envision, a Hybrid (wireless/wired) DCN (HDCN) architecture. Our HDCN is based on i) Cisco’s Massively Scalable Data Center (MSDC) model and ii) IEEE 802.11ad standard. Servers in the HDCN are regrouped into racks, where each rack is equipped with a: i) Ethernet top-of-rack (ToR) switch and ii) set of wireless antennas. Our research aims to optimize the routing and the allocation of wireless resources for inter-rack communications in HDCN while enhancing network performance and minimizing congestion. The problem of routing and resource allocation in HDCN is NP-hard. To deal with this difficulty, we will tackle the problem into three stages. In the first stage, we consider only one-hop inter-rack communications in HDCN, where all communicating racks are in the same transmission range. We will propound a new wireless channel allocation approach in HDCN to hardness both wireless and wired interfaces for incoming flows while enhancing network throughput. In the second stage, we deal with the multi-hop communications in HDCN where communicating racks can not communicate in one single-hop wireless path. We propose a new approach to jointly route and allocate channels for each single communication flow, in an online way. Finally, in the third stage, we address the batched arrival of inter-rack communications to the HDCN so as to further optimize the usage of wireless and wired resources. For that end, we propose: i) a heuristic-based and ii) an approximate, solutions, to solve the joint batch routing and channel assignment. Based on extensive simulations conducted in QualNet simulator while considering the full protocol stack, the obtained results for both real workload and uniform traces, show that our proposals outperform the prominent related strategies
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Wireless channel allocation plays as an important role in the-design of wireless network, as it greatly influences the throughput and performance of the network. It is proposed a technique to improve the usage of wireless spectrum in the context of IEEE 802.11 wireless network using new channel assignment methods among interfering Access Points (APs). Reliable channel selection for each Access Point (AP) is essential in setting up and operating densely deployed 802.11 WLANs. The aim of the channel selection is to provide efficient reuse of the spectrum and therefore minimize interference and improve the performance. The focus is mainly on to design an algorithm to solve the problem of channel allocation using Simulated Annealing. The algorithm minimizes the interference among the Access Points (APs). All the access points in the network operate on this algorithm simultaneously and determine the best channel it should use to minimize the interference from the neighboring access points.
To cope with the unprecedented traffic explosion, Internet giants are urged to rethink their data center design. Unfortunately, the conventional wired data centers struggle to support the impressive growth of both data and online services. In this regard, we resort to augmenting the wired Data Center Network (DCN) with wireless communication (60 GHz technology). Heretofore, only few research work have dealt with the optimization of multi-hop communications in such Hybrid DCN (HDCN) infrastructures. In this paper, we investigate, in HDCN, the issue of jointly: i) routing and ii) channel allocating, in both online and batch arrival modes. First, we formulate the online joint routing and channel assignment problem as a minimum weighted perfect matching problem. We propose a new strategy named Joint Routing and Channel Allocation Algorithm (JRCA-HDCN) that makes use of the Blossom algorithm and sequentially computes the optimal routing communication paths. Second, to handle the batched arrivals of flows, we formulate the batch joint routing and channel assignment problem as an advanced multi-commodity flow model. We propose two scalable approaches: i) a heuristic based solution, named Joint Routing and Channel Assignment Heuristic (JRH-HDCN), and ii) an approximate solution, named Scalable Joint Batch Routing and Channel Allocation (SJB-HDCN), based on the Lagrangian relaxation technique. Based on extensive network simulations conducted in QualNet simulator while considering the full protocol stack, the obtained results for both: i) real Facebook’s DC, and ii) uniform, traces, show that our schemes outperform the related strategies.
Recent results have made a promising case for offering oversubscribed wired data center networks (DCN) with extreme costs. Inter-rack wireless networks are drawing intensive attention to augment such wired DCNs with a few wireless links. Inspired by the promise of easy deployment and plug-and-play, we present VLCcube, a novel inter-rack wireless solution that extends the design of wireless DCN into three further dimensions: (1) all inter-rack links are wireless; (2) there is no imposition of any infrastructure-level alteration on wired production data centers; and (3) it should be plug-and-play, without any need of additional mechanical or electronic control operations. This vision, if realized, will lead to increased flexibility, reduced reconstructing cost, simplified configuration and usage, and outstanding compatibility with existing wired DCNs. Previous proposals, however, are opposed to the last two design rationales. To achieve this vision, the proposed VLCcube augments Fat-Tree, a representative DCN in production data centers, by organizing all racks into a wireless Torus structure via the emerging visible light links. We further present the topology design, hybrid routing, and flow scheduling schemes for VLCcube. Extensive evaluations indicate that VLCcube outperforms Fat-Tree significantly under the existing ECMP flow scheduling scheme, irrespective of the undergoing traffic pattern. Moreover, the performance of VLCcube can be significantly promoted by our congestion-aware flow scheduling scheme. More precisely, compared to ECMP, our flow scheduling scheme makes VLCcube achieve �1:50 throughput under batched flows, �2:21 and �2:59 throughput under two different kinds of online flows.
The rapid development of cloud computing in recent years has deeply affected our lifestyles. As core infrastructures of cloud computing, data centers have gained widespread attention from both the academia and industry. In a data center, the data center network (DCN) that plays a key role in computing and communication has attracted extensive interest from researchers. In this survey, we discuss the features, hardware, and architectures of DCN's, including their logical topological connections and physical component categorizations. We first give an overview of production data centers. Next, we introduce the hardware of DCN's, including switches, servers, storage devices, racks, and cables used in industries, which are highly essential for designing DCN architectures. And then we thoroughly analyze the topology designs and architectures of DCN's from various aspects, such as connection types, wiring layouts, interconnection facilities, and network characteristics based on the latest literature. Finally, the facility settings and maintenance issues for data centers that are important in the performance and the efficiency of DCN's are also briefly discussed. Specifically and importantly, we provide both qualitative and quantitative analyses on the features of DCN's, including performance comparisons among typical topology designs, connectivity discussion on average degree, bandwidth calculation, and diameter estimation, as well as the capacity enhancement of DCN's with wireless antennae and optical devices. The discussion of our survey can be referred as an overview of the ongoing research in the related area. We also present new observations and research trends for DCN's.