I am using the Network Simulator NS2 program (https://www.isi.edu/nsnam/ns/) in order to simulate a simple network topology with 1 UDP agent and 1 CBR Application Traffic sending data from a node over to another node further away. Somewhere in the middle of the topology, there is a choice of network path involved since there are two alternative options (either e.g. 1-2-3 or 1-4-3 where node 1 is sending data and 3 receiving). I am also using the following commands for dynamic routing:
Agent/rtProto/Direct set preference_ 200 $ns rtproto DV
I also use an rtmodel stop/start event in order to simulate the following network topology change: connection of nodes 1 and 2 is "cut off" and then reinstated later. My questions are as follows:
1) How is the time that exists between the path change after the 1-2 connection drop calculated? I can see some 11-byte rtProtoDV packets being transmitted through the network but I don't exactly understand how the time between the connection drop and the packet-delivery network path change is calculated.
2) Which one of all the nodes defines where the packets will be directed? So, does the traffic source define the whole path that one of its sent packets will follow, or do the intermittent nodes decide seperately where to forward the packets ad-hoc?
3) What does the
Agent/rtProto/Direct set preference_ 200 command exactly do? I have read on the NS2 manual that the default value is 100, but what does it exactly do differently when it is 100 vs. when it is 200? The NS2 manual isn't clear at all at that point... (https://www.isi.edu/nsnam/ns/doc/node311.html)