Abstract

A data center is a facility for housing computational and storage systems interconnected through a communication network called data center network (DCN). Due to a tremendous growth in the computational power, storage capacity and the number of inter-connected servers, the DCN faces challenges concerning efficiency, reliability and scalability. Although transmission control protocol (TCP) is a time-tested transport protocol in the Internet, DCN challenges such as inadequate buffer space in switches and bandwidth limitations have prompted the researchers to propose techniques to improve TCP performance or design new transport protocols for DCN. Data center TCP (DCTCP) emerge as one of the most promising solutions in this domain which employs the explicit congestion notification feature of TCP to enhance the TCP congestion control algorithm. While DCTCP has been analyzed for two-tier tree-based DCN topology for traffic between servers in the same rack which is common in cloud applications, it remains oblivious to the traffic patterns common in university and private enterprise networks which traverse the complete network interconnect spanning upper tier layers. We also recognize that DCTCP performance cannot remain unaffected by the underlying DCN architecture hence there is a need to test and compare DCTCP performance when implemented over diverse DCN architectures. Some of the most notable DCN architectures are the legacy three-tier, fat-tree, BCube, DCell, VL2, and CamCube. In this research, we simulate the two switch-centric DCN architectures; the widely deployed legacy three-tier architecture and the promising fat-tree architecture using network simulator and analyze the performance of DCTCP in terms of throughput and delay for realistic traffic patterns. We also examine how DCTCP prevents incast and outcast congestion when realistic DCN traffic patterns are employed in above mentioned topologies. Our results show that the underlying DCN architecture significantly impacts DCTCP performance. We find that DCTCP gives optimal performance in fat-tree topology and is most suitable for large networks.

Highlights

  • A data center is a facility that houses computational and storage systems which are interconnected through a communication network

  • Traffic characteristics of data center networks In this subsection, we summarize the traffic characteristics of data center networks which we studied in order to understand realistic and common Data Center Network (DCN) traffic patterns for our simulations

  • The fat-tree DCN topology is simulated such that 48-port 1 gigabit ethernet (GigE) switches and 1 Gbps Ethernet links are used at all layers

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Summary

Introduction

A data center is a facility that houses computational and storage systems which are interconnected through a communication network. In addition to computational and storage systems, it includes power supply equipment, communication network, air conditioning, security systems and other related devices and can span over an area as large as a small town These data centers serve a large number of popular services in Internet such as search engines (e.g. Google), Internet commerce (e.g. Amazon and e-Bay), web based e-mail (e.g. yahoo mail), social networking (e.g. Myspace and Facebook) and video sharing (e.g. YouTube). In addition to some dual-centric architectures combining the best of both categories, the legacy three-tier tree-based architecture continues to be the most widely deployed and fat-tree being the most promising in terms of scalability, robustness and cost (Bilal et al 2013). A typical data center network consists of access layer, aggregation layer and core layer It consists of routers and switches, in two-level or three-level hierarchy.

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