Validation of application behavior on a virtual time integrated network emulation testbed

Combination of emulation and simulation offers the hope of both functional and temporal fidelity when modeling large scale networks and the applications that use them. Emulation of unmodified software gives functional fidelity, but not necessary temporal fidelity. We addressed this in prior work by embedding the OpenVZ virtual machine system in virtual time. Validation reveals that there are network timing errors whose magnitude depend on the length of a virtual machine execution timeslice. A natural question asks to what degree these errors impact the behavior of applications. For instance, if an application is relatively insensitive to these errors, we can increase performance by allowing larger emulation timeslices. We study a variety of applications with different network and CPU demands. We find, surprisingly, that difference in application behavior due to simply using OpenVZ often dominate the errors, implying that we need not be overconcerned about errors due to larger timeslices.