Datacenter Traffic Control: Understanding Techniques and Trade-offs
Creators: name: Noormohammadpour, Mohammad
name: Cauligi S. Raghavendra
Publisher: name: figshare
Year: 2018
Subjects: subject: 100503 Computer Communications Networks
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: 100504 Data Communications
subject: 100506 Optical Fibre Communications
subject: 100507 Optical Networks and Systems
subject: Distributed Computing
subject: FOS: Computer and information sciences
subject: FOS: Computer and information sciences
subject: 80503 Networking and Communications
subject: Computer Engineering
subject: 120404 Engineering Systems Design
subject: FOS: Other engineering and technologies
subject: FOS: Other engineering and technologies
subject: Applied Computer Science

description: Datacenters provide cost-effective and flexible access to scalable compute and storage resources necessary for today’s cloud computing needs. A typical datacenter is made up of thousands of servers connected with a large network and usually managed by one operator. To provide quality access to the variety of applications and services hosted on datacenters and maximize performance, it deems necessary to use datacenter networks effectively and efficiently. Datacenter traffic is often a mix of several classes with different priorities and requirements. This includes user-generated interactive traffic, traffic with deadlines, and long-running traffic. To this end, custom transport protocols and traffic management techniques have been developed to improve datacenter network performance. In this tutorial paper, we review the general architecture of datacenter networks, various topologies proposed for them, their traffic properties, general traffic control challenges in datacenters and general traffic control objectives. The purpose of this paper is to bring out the important characteristics of traffic control in datacenters and not to survey all existing solutions (as it is virtually impossible due to massive body of existing research). We hope to provide readers with a wide range of options and factors while considering a variety of traffic control mechanisms. We discuss various characteristics of datacenter traffic control including management schemes, transmission control, traffic shaping, prioritization, load balancing, multipathing, and traffic scheduling. Next, we point to several open challenges as well as new and interesting networking paradigms. At the end of this paper, we briefly review inter-datacenter networks that connect geographically dispersed datacenters which have been receiving increasing attention recently and pose interesting and novel research problems. To measure the performance of datacenter networks, different performance metrics have been used such as flow completion times, deadline miss rate, throughput and fairness. Depending on the application and user requirements, some metrics may need more attention. While investigating different traffic control techniques, we point out the trade-offs involved in terms of costs, complexity and performance. We find that a combination of different traffic control techniques may be necessary at particular entities and layers in the network to improve the variety of performance metrics. We also find that despite significant research efforts, there are still open problems that demand further attention from the research community.