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Unformatted text preview: Large-scale Virtualization in the Emulab Network Testbed Mike Hibler Robert Ricci Leigh Stoller Jonathon Duerig Shashi Guruprasad Tim Stack Kirk Webb Jay Lepreau University of Utah, School of Computing www.emulab.net www.flux.utah.edu Abstract Network emulation is valuable largely because of its abil- ity to study applications running on real hosts and some- what real networks. However, conservatively allocating a physical host or network link for each corresponding virtual entity is costly and limits scale. We present a system that can faithfully emulate, on low-end PCs, vir- tual topologies over an order of magnitude larger than the physical hardware, when running typical classes of distributed applications that have modest resource re- quirements. This version of Emulab virtualizes hosts, routers, and networks, while retaining near-total applica- tion transparency, good performance fidelity, responsive- ness suitable for interactive use, high system throughput, and efficient use of resources. Our key design techniques are to use the minimum degree of virtualization that pro- vides transparency to applications, to exploit the hierar- chy found in real computer networks, to perform opti- mistic automated resource allocation, and to use feed- back to adaptively allocate resources. The entire system is highly automated, making it easy to use even when scaling to more than a thousand virtual nodes. This paper identifies the many problems posed in building a practi- cal system, and describes the systems motivation, de- sign, and preliminary evaluation. 1 Introduction Network experimentation environments that emulate some aspects of the environmentnetwork testbeds play an important role in the design and validation of dis- tributed systems and networking protocols. In contrast to simulated environments, testbeds like Emulab  and PlanetLab  provide more realistic testing grounds for developing and experimenting with software. Emulated environments implement virtual network configurations atop real hardware: this means that experimenters can use real operating systems and other software, run their Currently at Cisco Systems, VMware, and Morgan Stanley, re- spectively. Work done at the University of Utah. applications unmodified, and obtain actual (not simu- lated) performance measures. A primary challenge for future emulation environ- ments is scale. Because emulated environments are sup- ported by actual hardware, an emulated system that is larger than the underlying physical system requires the careful allocation and multiplexing of a testbeds physi- cal resources. To avoid experimental artifacts, the orig- inal Emulab used strictly conservative resource alloca- tion. It mapped virtual network nodes and links one-to- one onto dedicated PCs and switched Ethernet links. We have four motivations for relaxing this constraint, allow- ing controlled multiplexing of virtual onto physical re- sources. First, some applications such as peer-to-peer...
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This note was uploaded on 11/12/2011 for the course CE 726 taught by Professor Staf during the Spring '11 term at SUNY Buffalo.
- Spring '11