Looking into ibrdtn mail list, I have found a thread in which Johannes  explained some way around to avoid the issues with the clock synchronization. So what I did was to run the daemon with the option --badclock and now the dtnping works fine as well as sending stuff through dtn nodes(just in one way from node 2 to node C); however, I would like to solve the issue with the clocks, could you tell me what is the precision that I would achieve with the clocks? Since, I have already set both dates on the systems with maybe a difference of few seconds, but if I disable the --badclock option then I still have that error.