DYNAMIC TIME VIRTUALIZATION FOR SCALABLE AND HIGH FIDELITY HYBRID NETWORK EMULATION
A system and method for measurement of the performance of a network by simulation, wherein time divergence is addressed by using discrete event simulation time to control and synchronize time advance or time slow down on virtual machines for large-scale hybrid network emulation, particularly where the loss of fidelity could otherwise be substantial. A dynamic time control and synchronization mechanism is implemented in a hypervisor clock control module on each test bed machine, which enables tight control of virtual machine time using time information from the simulation. A simulator state introspection and control module, running alongside the simulator, enables extraction of time information from the simulation and control of simulation time, which is supplied to the virtual machines. This is accomplished with a small footprint and low overhead.
1 . A system for simulating operation of a network, comprising:
a simulator for simulating operation of said network; and
a simulator time clock for providing simulation time to the components of the network, said simulation time being advanced at discrete moments in real time, to advance time when said simulator conducts operations faster than the real time, and to advance more slowly than the real time when said simulator conducts operations more slowly than said real time.
2 . The system of claim 1 , further comprising a simulator introspection and control module for extracting time information from said simulator, and for control of simulation time.
3 . The system of claim 1 , further comprising a hypervisor for providing said simulation time and a simulation time advance rate to the simulated components of the network.
4 . The system of claim 3 , wherein said hypervisor comprises a clock control module, wherein said clock control module receives said simulation time and a time slow down factor.
5 . The system of claim 3 , wherein said hypervisor comprises:
a clock control module which receives said simulation time and a time slow down factor and provides updated timeout values, and outputs said simulation time, and said simulation time advance rate;
a periodic timer and a one shot timer for each simulated component of the network receiving the updated timeout values and for outputting timer interrupts; and
a system time setting mechanism for receiving said simulation time and said simulation time advance rate;
wherein said simulated components of said network receive one of a time interrupt from one of said periodic timer and said one-shot timer, and said simulation time and said simulation time advance rate from said system time setting mechanism.
6 . The system of claim 1 , wherein said simulated components are virtual machines.
7 . The system of claim 6 , wherein said virtual machines represent nodes of said network.
8 . The system of claim 7 , wherein said system time is a piece-wise linear approximation of actual simulation time in said simulator, sampled at discrete moments in said real time.
9 . The system of claim 1 , wherein the discrete moments are at constant time intervals from one another.
10 . The system of claim 1 , wherein said simulation time is constrained so as not to advance faster than said real time.
11 . A method system for simulating operation of a network, comprising:
simulating operation of said network;
providing simulation time to said components of said network, at discrete moments in real time, to advance time when a simulator conducts operations faster than said real time, and to advance more slowly than said real time when said simulator conducts operations more slowly than said real time.
12 . The method of claim 11 , wherein said simulation time is driven by a timestamp of a next event to be processed in the simulation.
13 . The method of claim 11 , wherein said simulation time is driven by receipt of a data packet by a node in said network.
14 . The method of claim 11 , wherein said simulated components are virtual machines.
15 . The method of claim 14 , wherein said virtual machines represent nodes of a network.
16 . The method of claim 11 , wherein said system time is a piece-wise linear approximation of actual simulation time in said simulator, sampled at discrete moments in said real time.
17 . The method of claim 11 , wherein said discrete moments are at constant time intervals from one another.
18 . The method of claim 11 , wherein said simulation time is constrained so as not to advance faster than said real time.
19 . A computer readable non-transitory storage medium storing instructions of a computer program which when executed by a computer system results in performance of steps of a method for disseminating content, comprising:
simulating operation of said network;
providing simulation time to said components of said network, at discrete moments in real time, to advance time when a simulator conducts operations faster than said real time, and to advance more slowly than said real time when said simulator conducts operations more slowly than said real time.