数据中心Clos网络负载均衡方案:问题、进展与展望  

Load Balancing Schemes for Data Center Network:Problems,Progress and Prospects

作　　者：刁兴龙 余晓杉[1] 刘勇[1] 黄狄涛 顾华玺[1] DIAO Xing-Long;YU Xiao-Shan;LIU Yong;HUANG Di-Tao;GU Hua-Xi(State Key Laboratory of Integrated Service Networks,Xidian University,Xi’an 710071)

机构地区：[1]西安电子科技大学ISN国家重点实验室,西安710071

出　　处：《计算机学报》2020年第12期2241-2258,共18页Chinese Journal of Computers

基　　金：国家重点研发计划项目(2018YFE0202800);国家自然科学基金(61634004,61934002,61901314);陕西省杰出青年科学基金(2020JC-26);中央高校基本科研业务费专项资金(JB190105);计算机体系结构国家重点实验室开放课题(CARCH201919)资助.

摘　　要：在云计算、大数据等信息技术的带动下,分布式应用成为数据中心网络内的主要业务模式.数据中心网络内部的流量呈现“东西向为主”、“大小流混合”的特性,实现数据中心网络负载均衡对提升网络带宽利用率、满足大小流需求具有重大意义.得益于数据中心网络Clos拓扑提供的并行相等跳数的路径,等价多路径(Equal-Cost Multipath,ECMP)被广泛用于数据中心网络负载均衡.在实际中复杂的流量场景下,ECMP并未表现出预期的性能,哈希碰撞、鼠流阻塞问题未能满足象流的高吞吐需求以及鼠流的低时延需求,另外,由链路故障导致的网络拓扑非对称性问题也给负载均衡带来了重大挑战.本文首先分析了ECMP在实际应用中面临的问题,然后针对具体问题对现有负载均衡方案进行了综述,剖析了各方案的基本思想和实现方法,并对各方案的均衡效果进行了分析.最后,本文从处理粒度、决策方式、拥塞感知范围等多个维度对现有的数据中心网络负载均衡方案做了对比,总结并展望了未来数据中心网络负载均衡技术的发展趋势.Driven by information technology such as cloud computing and big data techniques,distributed applications have become the most popular business model in data centers networks.There are two characteristics of traffic within the data center:east-west traffic accounts for a large proportion of the total traffic within data center,and the traffic within data center is a mixture of large flows and small flows(also called elephant flows and mice flows,respectively).Load balancing in data center networks is of great significance to improve network bandwidth utilization and meet the demand of large flows and small flows.Modern data centers often employ multi-rooted Clos topology which provides multi paths with equal hops between any two hosts,thus Equal-cost Multipath(ECMP)is widely used for load balancing in data center networks.The realistic traffic is very complex,and ECMP does not show the expected load balancing effect.Firstly,this paper analyzes the problems faced by ECMP in the realistic scenario,such as hash collision and mice-flow blocking,which fails to meet the high throughput demand of elephant flows and the low latency demand of mice flows.In addition,frequent link failures in data center networks lead to asymmetric topology,which reduces the number of equal cost paths and brings great challenges to load balancing.Then this paper investigates the existing load balancing schemes,analyzes the basic idea and the implementation of each scheme,and discusses the advantages and disadvantages of each scheme and the load balancing effect on the specific problem faced by ECMP.At last,this paper compares the various load balancing schemes in terms of three levels,including granularity,decision-making approach and the range of link-state awareness.Based on the comparison,this paper summarizes and forecasts the trend of future load balancing technology in data center networks.First,the granularity of load balancing tends to fine grained,because flow-level granularity can easily lead to hash collision and mice-flow blocki

关 键 词：数据中心网络 负载均衡 ECMP 哈希碰撞 鼠流阻塞 非对称性 

分 类 号：TP393[自动化与计算机技术—计算机应用技术]