My observation is that packets are retransmitted 4 times until they are dropped on the MAC layer. This is the default value for MAC_LongRetryLimit in ns2.
The Transmission Delay in my simulation consisting of two nodes has only a minor randomness. It highly depends on the current data rate, and graphs are as angular as the troughput graphs.
What could be the reason?
- No retransmissions due to bit errors as there are just 2 nodes and no interference by noise.
- No retransmissions induced by multipath fading, as it is not simulated.
- Retransmissions only occur for queued packets after the nodes move out of transmission range. These retransmissions always fail and therefore do not affect the transmission delay.
- The interface queue behaves strange. It does not do FIFO. The interface queue size does not affect the graph shape much anyway.