Hello.

By design of the bundle protocol, synchronized clocks are mandatory in a DTN. Since that is heavy constrain, I am working on solutions to mitigate the issue or provide time-synchronization even in losely connected networks. Basically, there are two approaches. One of them is the Age Block Extension which allows to track the age of a bundle without a correct clock. Since this might be quite inaccurately, IBR-DTN provides a mechanism to synchronize clocks. The approach to do this is described in this paper:http://dl.acm.org/citation.cfm?doid=2348616.2348618 http://dl.acm.org/citation.cfm?doid=2348616.2348618.

To enable time-sync you need at least one reference clock (master) in your network.

# Master configuration time_reference = yes time_discovery_announcements = yes

The best way is to choose a node with a NTP (or something equal) as master. Sich a master will announce its time data to slaves.

# Slave configuration time_reference = no time_discovery_announcements = yes time_synchronize = yes

If the daemon runs as root, it can set the nodes clock if synchronized

time_set_clock = no

Be aware of that existing code in the releases is very experimental and not completly polished to work under all circumstances. There are known bugs which are already solved in the master GIT branch, but due to larger changes not in the 0.10.x releases.

Kind regards, Johannes

Am 23.09.2013 14:40, schrieb Shyam B:

Hello All,

I am working on a project with DTN in which while exchanging the bundles either don't reach the destination or the file transfer fails completely. Then I routed the problem on different times on the system. There was some google page about BAD_Clock, but I am not able to find that page on ibrdtn wiki anymore.

Could someone help me with, how to configure:

1. Considering completely BAD_Clocks on different nodes, I can still

be able to transmit data. I don't mind time conscience/ security in this regard, for now. My nodes (RPis) are not connected to internet, so they don't know anything about time if they are switched off. Moreoever, I do not have a real-time clock for it.

2. When setting time_synchronize parameter in the ibrdtnd.conf file

does not help. What does this really do, any documentation on this and other <time> related parameter would be helpful.

Thanks a lot!