Hi Daniel,

I reada your post below and it solved some queries on the nature of event
processing being done by ns for me too. However, I have one question. How
does ns handle scenarios like hidden/masked nodes etc? lets consider this
following scenario: Nodes 1 and 2 have had a successful RTS-CTS exchange and
are in the process of transferring Data packets. During this time, Node 3
moves into their transmission range and sends in an interfering packet which
results in a collision at node 2. Now, according to your mail - the
simulator should first be sequentially carrying out the entire packet
exchange and update the trace file. After this, how does it take the effect
of node 3 and ensure that a collision is reported?? This should take place
sequentially after the packet exchange (according to wall-clock time) but
the simulator clock should be stopped at the data transmission process
itself right??

I know this is implemented correctly in ns, but am confused as to how they
are doing it. It would be of great help if you could let me know your
opinions. Thanks in advance.


On 4/1/06, Daniel Mahrenholz <[EMAIL PROTECTED]> wrote:
> On Friday 31 March 2006 17:33, Saurabh Sinha wrote:
> > I just wanted to know that whether ns2 supports threads or not? Like can
> > more that 2 two stations transmit at the same time
> > It will of gr8 help if some one can post a suggestion
> Yes and no - ns2 itself does not use threads. But the event-based
> processing
> model does not need threads to allow for concurrent threads of control.
> That
> means two station can perform actions at the same moment in time. The
> simulator will serialize them and compute them sequentially. An
> event-based
> simulation does not need to care about real-time (wall clock time), it has
> its own time base and so can compute as much events (happening) at the
> same
> time as you need. The simulation time will stand still during the
> processing
> of an event and will jump to the execution time of the next event that has
> to
> be processed.
> Hope this answers your question.
> Daniel.
> --
> Dipl.-Inf. Daniel Mahrenholz, University of Magdeburg, Germany
> Homepage: http://ivs.cs.uni-magdeburg.de/~mahrenho

Mohammad Zubair Ahmad
PhD Student, Computer Engineering
University of Central Florida,
Orlando, FL 32826

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