[Ns-developers] Coming up: Synchronized Network Emulation for ns-3

[Elias Weingärtner]

Dear ns-3 developers,

I wanted to let you know that there's something in the pipe according
to the ns-3 emulation features that might be interesting for you:

Essentially, network emulation as implemented in ns-3, right now
suffers from the burden that the simulation has to be real-time
capable, as otherwise a time drift between the simulation and the real
system may occur and thus corrupt the results. The only option so far
is to speed up the simulation, e.g. by parallelization or by throwing
more horsepowers at it.  We follow a different approach. To solve this
problem, we are currently working on an implementation of Synchronized
Network Emulation [1] for ns-3. It allows one to synchronize the
execution of a ns-3 simulation with the one of the real-systems
attached. Essentially, this way we make the real time systems execute
slower to match the simulation speed.  We achieve this by placing the
software prototypes in a virtualization environment, precisely a
modified Xen hypervisor, that controls the execution and the time
perception of the OS in order to make this synchronization process
transparent to the OS hosting the software prototype. Our HotMetrics
paper[1| provides additional insight on this concept.

Our implementation was initially based on OMNeT++, but  since a couple
of days we have a first lab-prototype based on ns-3 3.4. It allows the
synchronized execution of ns-3 and Xen domains with an accuracy up to
10 microseconds. If we choose an accuracy of one 1 millisecond, the
synchronization overhead is below 5%. Right now, we're performing a
lot of testing and evaluations, and we're currently preparing these
results for a publication at a major conference.  However, we would
also like to contribute the toolchain to the ns-3 community once
published, as we anticipate it to be valuable for the networking
research community.

Best regards,

Elias


[1]  Weingärtner, E, Schmidt, F, Heer, T, and Wehrle, K (2008):
"Synchronized network emulation: matching prototypes with complex
simulations", SIGMETRICS Performance Evaluation Review, 36(2):58-63.
http://ds.informatik.rwth-aachen.de/members/weingaertner/publications/pdfs/hotmetrics08_shortened.pdf

----
Dipl.-Inf. Elias Weingaertner
Research Assistant
Distributed Systems Group
RWTH Aachen
Germany
http://ds.informatik.rwth-aachen.de/members/weingaertner