延時是一種可以同步速度較慢的模擬器與真實運行的系統的方法。
一種常見的實作方式是利用全虛擬化技術，透過修改虛擬機管理器的內部時鐘來達到延時的效果。此方法雖然準確但是佈建困難且會耗用大量系統資源。
我們提出了一種輕量化的方式，透過攔截與修改時間相關的系統函式，我們可以在不需要全虛擬化的狀況下支援延時的功能。

Time Dilation is a technique for synchronising realtime emulators and slow simulators. It slows down time flow seen by emulators for simulators to catch up. A common approach is full-vitrualisation by patching internal clock of virtual machine hypervisor to provide virtual time to virtual machines. It is accurate but time-consuming to deploy and resource-hungry because every virtual machine needs to maintain its own guest OS. We propose a lightweight approach. By intercepting and modifying several time-related functions, we can support multiple emulators without setting up virtual machines.

K. Lawton et al., “Running multiple operating systems concur- rently on an ia32 pc using virtualization techniques,” Unpub- lished, November, 1999.
B. Lantz, B. Heller, and N. McKeown, “A network in a laptop: Rapid prototyping for software-defined networks,” in Proceedings of the 9th ACM SIGCOMM Workshop on Hot Topics in Net- works, Hotnets-IX, (New York, NY, USA), pp. 19:1–19:6, ACM, 2010.
M. Helsley, “Lxc: Linux container tools,” IBM devloperWorks Technical Library, 2009.
D. Gupta, K. Yocum, M. McNett, A. C. Snoeren, A. Vahdat, and G. M. Voelker, “To infinity and beyond: Time-warped network emulation,” in Proceedings of the 3rd Conference on Networked Systems Design & Implementation - Volume 3, NSDI’06, (Berke- ley, CA, USA), pp. 7–7, USENIX Association, 2006.
E. Weing ̈artner, F. Schmidt, H. V. Lehn, T. Heer, and K. Wehrle,
29
References 30
“Slicetime: A platform for scalable and accurate network emu- lation,” in Proceedings of the 8th USENIX Conference on Net- worked Systems Design and Implementation, NSDI’11, (Berkeley, CA, USA), pp. 253–266, USENIX Association, 2011.
H. W. Lee, D. Thuente, and M. L. Sichitiu, “Integrated simula- tion and emulation using adaptive time dilation,” in Proceedings of the 2Nd ACM SIGSIM/PADS Conference on Principles of Ad- vanced Discrete Simulation, SIGSIM-PADS ’14, (New York, NY, USA), pp. 167–178, ACM, 2014.
“libfaketime,” Available at https://github.com/wolfcw/ libfaketime.
T. R. Henderson, S. Roy, S. Floyd, and G. F. Riley, “Ns-3 project goals,” in Proceeding from the 2006 Workshop on Ns-2: The IP Network Simulator, WNS2 ’06, (New York, NY, USA), 2006.