[Ns-developers] turning nodes on/off - failure/recovery models

[Pavel Boyko]

  Hi, 

> it would be great if ns-3 could support switching on/off nodes.

  I agree. For my current needs unrecoverable node failure (e.g. battery 
failure) is enough. For wireless networks  we use "rocket to the Moon" 
workaround to instantly move node far away in z direction and forget about it. 
But sure, it would be nice to have a more meaningful device level failure 
support, like: 

virtual void NetDevice::TurnOff () = 0;
virtual void NetDevice::TurnOn () = 0;
virtual void NetDevice::Reset () { TurnOff (); TurnOn (); }  

  implemented by all devices and node failure/recovery helper which switches 
all devices off and on and even higher level stochastic failure-recovery 
models. 

>  But there may also
>  be scenarios where one wants to simulate that some nodes leave and other
>  nodes do later join the network. 
>  If "switch on with reset" would also be
>  supported, one could use the same nodes that were switched off before in
>  the latter case.

  I am afraid this will be very difficult to implement because node state is 
shared between large number of objects: devices, protocols, applications and 
reset them all can be problematic in general. Also the implicit assumption 
that initialization happens at time = 0 is badly spread through the code.

  Best regards,
  Pavel