Introduction to Data Center Network Architecture

Introduction to Data Center Network Architecture

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  Data Center NetworkArchitecture Presented by: Ankita Mahajan
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  Design Goals FAT-Tree DCN RecursiveDCN Design MDCs Virtualized DCN DCN-Introduction
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  Data Center Network DataCenter Networks are large clusters of servers interconnected by network switches. These servers are used to host applications which provide different concurrent services. Ex) • Web services like DNS, Web server, Mail server, gaming server, chat server. • Compute services like suggestion systems, indexing and scientific computing. DCN Usage Scenarios: • Compute Intensive: Heavily loaded servers, but low inter-server comm. Ex) HPC • Data Intensive: Huge intra-DCN data transfer, but low load at servers. Ex) Video and File Streaming • Balanced: Communication links and computing servers are proportionally loaded. Ex) Geographic Information System
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  Conventional DCN Architecture Rack3 Rack 10Rack 1 Rack 2 Server 21 Server 100 Server 91 Server 30 Server 1 Server 20 Server 11 Server 10 ToR ToRToR ToR AggrAggr Aggr Core Core Core [10 GigE switches] Aggregation [10 GigE switches] Edge [Commodity switches] Internet ETHERNET
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  DCN Design Goals •Availability and Fault tolerance: Multiple paths and replicated servers. Graceful Degradation. Challenges: • Reduced Utilization
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  DCN Design Goals •Availability and Fault tolerance: Multiple paths and replicated servers. Graceful Degradation. • Scalability: Incrementally increase DCN size as and when needed. • Low Cost: Lower power and cooling costs. Challenges: • Reduced Utilization • Scale-out vs Scale-up: per-port cost, cabling and packaging complexity, scalable cooling. • Placement, Air-Flow and rack-density
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  DCN Design Goals •Availability and Fault tolerance: Multiple paths and replicated servers. Graceful Degradation. • Scalability: Incrementally increase DCN size as and when needed. • Low Cost: Lower power and cooling costs. • Throughput: The number of requests completed by the data center per unit of time. (Compute + Transmission+ Aggregation Time) • Economies of scale: Utilize the benefits of its huge size. • Scalable interconnect bandwidth: Host to host communication at full bisection bandwidth. • Load balancing: Avoid hot-spots, to fully utilize the multiple paths. Challenges: • Reduced Utilization • Scale-out vs Scale-up: per-port cost, cabling and packaging complexity, scalable cooling. • Placement, Air-Flow and rack-density • TCP Incast, Large Buffer switches • Resource fragmentation: VLANs • Manual Configuration • Oversubscription: 1:1 vs 1:240 • Flooding and Routing n/w overhead
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  Fat-Tree Based DCArchitecture 1:1 Oversubscription ratio. Commodity Fat-tree with K=4 K-ary fat tree: three-layer topology (edge, aggregation and core) • each pod consists of (k/2)2 servers & 2 layers of k/2 k-port switches • each edge switch connects to k/2 servers & k/2 aggr. switches • each aggr. switch connects to k/2 edge & k/2 core switches • (k/2)2 core switches: each connects to k pods • i,e, (k/2)2 core switches for k2 pod switches and (k/2)2 servers.
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  Fat-Tree Based DCArchitecture 1:1 Oversubscription ratio. Commodity Fat-tree with K=4 Advantages: •Full Bisection BW: 1:1 Oversubscription ratio •Low Cost: Commodity switches Disadvantage: •Scalability: Size of n/w dependent upon ports per switch.48 ports => maximum 27,648 hosts. •Agility and Performance Isolation: Not supported
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  Recursive DCN Architecture •A Level-0 subnet is the basic building block. It contains inter-connected servers. • Each level-k subnet has multiple level-(k-1) subnets. • Ex) DCell, BCube, 4-4 1-4, etc • Advantages: • Highly Scalable commodity n/w • Low CapEx and OpEx. • Disadvantage: • Cabling and packaging
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  Modular Data Centers(MDC) High density, shipping container based DCN. Should be Robust and provide Graceful Performance Degradation. Advantages:
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  Modular Data Centers(MDC) High density, shipping container based DCN. Should be Robust and provide Graceful Performance Degradation. Advantages: • Fast deployment • Lower costs • Increased efficiency • Easy scale-out
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  Virtualized DCN Added Issues: •Agility: Allocate any server to any service dynamically for performance isolation. • VM-migration across DCNs: No manual configuration. • Availability and Fault tolerance: Configuration of server IP addresses Solution: Separation of Location and Identity addresses. Ex) VL2, 4-4 1-4, etc Data Structure of Directory Packet tunneled through physical network using location-IP header
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  Typical Inter ServerCommunication in DC
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  Example: 4-4 1-4DCN Fig: 4-4 1-4 Data Center • 4-4 1-4 is a location based forwarding architecture for DCN which utilizes IP-hierarchy. • Uses statically assigned, location based IP addresses for all network nodes. • Forwarding of packets is done by masking the destination IP address bits. • No routing or forwarding table maintained at switches • No convergence overhead of routing protocols. No. of physical machines in figure = 65,536
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  References • A. Kumar,S. V. Rao, and D. Goswami, “4-4, 1-4: Architecture for Data Center Network Based on IP Address Hierarchy for Efficient Routing," in Parallel and Distributed Computing (ISPDC), 2012 11th International Symposium on, 2012, pp. 235-242. • M. Al-Fares, A. Loukissas, and A. Vahdat, “A scalable, commodity data center network architecture," in Proceedings of the ACM SIGCOMM 2008 conference on Data communication, ser. SIGCOMM '08. New York, NY, USA: ACM, 2008, pp. 63-74.[Online]. Available: http://doi.acm.org/10.1145/1402958.1402967 • C. Guo, G. Lu, D. Li, H. Wu, X. Zhang, Y. Shi, C. Tian, Y. Zhang, and S. Lu, “Bcube:a high performance, server-centric network architecture for modular data centers.“ • T. Benson, A. Anand, A. Akella, and M. Zhang, “Understanding data center trac characteristics," SIGCOMM Comput. Commun. Rev., vol. 40, no. 1, pp. 92{99, Jan. 2010. [Online]. Available: http://doi.acm.org/10.1145/1672308.1672325 • A. Greenberg, J. Hamilton, D. A. Maltz, and P. Patel. “The cost of a cloud: research problems in data center networks.” SIGCOMM Comput. Commun. Rev.,39(1):68–73, 2009.