DummyNet configuration for opportunistic Links for emulating DTN

[Luigi Rizzo]

On Mon, May 09, 2011 at 10:16:43PM +0530, quamar niyaz wrote:
> Hi,
> 
> I am working on a application which is meant for Delay Tolerant Network. I
> want to emulate the opportunistic link availability for the data sending
> nodes using dummyNet . One scenario,  suppose from source node to
> destination node let's say a data link is available at around 9 a.m. morning
> and the latency of the link from source node to destination node is 1hr. So
> if a request for upload comes around 8 a.m. at the sending node then the
> data should start reaching to the destination node after 10 a.m. as the link
> between the nodes comes at 9 and the latency is 1 hr so delivery time at the
> destination node(9 a.m. +1hr. = 10.am.). In other words sending node should
> hold the data in its buffer till 10 a.m as the nodes are actually in my 100
> Mbps LAN so for emulating this the sender must start sending the data after
> 10 a.m.
> 
> Can the buffer holds such large amount of data e.g. 500 MB for an hour. Or I
> have to modify the buffer size if yes, to which file i have to modify and
> then build dummynet. Or simply writing a batch scripts is fine for this.
> Please let me know. Thanks in advance

this kind  of stuff belongs to the application layer, not in
the link layer. It is not just a matter of buffering, but
the fact that your application will likely want to choose what
to send when the link becomes available.

cheers
luigi