Network Emulation with Adaptive Time Dilation

OVERVIEW

Project Description

Building a testbed for large-scale heterogeneous systems can be costly and inefficient. Emulation is often used to evaluate the performance of a system in a controlled environment. Time dilation allows virtual machines (VMs) to emulate higher performance than that of their physical machine. We present an approach using adaptive time dilation to emulate large-scale distributed systems composed of heterogeneous machines and OSs.

Our proposed emulation system can be used to test systems comprising heterogeneous OSs. To emulate heterogeneous OSs (e.g. Linux, FreeBSD, Windows, Cisco IOS, Junos, etc), we use QEMU-KVM that supports full virtualization.

Adaptive Time Dilation

Time dilation is a technique to slow the passage of virtual time (from the perspective of a virtual host) by a specified factor, which is referred to as time dilation factor (TDF). With time dilation, physical resources appear TDF times faster (i.e., higher performance is emulated). One second of virtual time passes for every TDF seconds of real time in virtual hosts (VHs). Therefore, time dilation enables empirical evaluation at CPU speeds that are not currently available from production hardware and larger system emulation on fewer physical hosts (PHs).

A fixed TDF can result in system underutilization. Adapting time dilation to system loads allows the system to effectively utilize its resources.

System Architecture

In order to allow VMs to run unmodified OSs, the control of time dilation is performed at the level of the QEMU-KVM hypervisor.

Synchronization agents exchange TDF control messages to synchronize VHs distributed over different PHs.

System Architecture

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