Hello Luis,
I think fragmentation as defined by the RFC 5050 is a very difficult thing. During the development of IBR-DTN, I recognized many cases which could lead to a bad network behavior, that I decided to just implement the safe ones.
These cases are pro-active fragmentation on sender only and reactive fragmentation with limited scope. While the pro-active fragmentation only split up a bundle at the receiver (and not on the path to its destination), the reactive fragmentation allows to resume an aborted bundle transfer between two nodes. In example, sender A transfers a bundle X to peer B. If the transmission gets interrupted, X will be split up virtually into X' and X''. The peer B can now forward the fragment X'' but what should A do now with the copy of X and X'? Should it forward only X' or X or both if another peer is met? I decided to limit the scope of the fragmentation to the relation between A and B, so that only if A meets B again the remaining fragment X' is forwarded. In case node A meets another peer, the complete bundle X is forwarded.
The RFC 5050 do not specify the exact behavior for that mechanism, because this may depend on the used routing scheme. The way IBR-DTN handle this issue works (as far I can tell) with any routing scheme out there, but may be not ideal in any case.
Kind regards, Johannes Morgenroth
Am 08.11.2013 18:10, schrieb Luís Carlos Guedes:
Hello,
I wanted to make an improvement related to the fragmentation process. The fragmentation process is made node by node, which limits the efficiency of IBR-DTN. This process can be improved, by enabling the different parts of a bundle that could be received by a destination from different nodes.
For example, a node A has a bundle to send to node D. First, 30 percent of the bundle are sent to node B and then 70 percent are sent to node C. Then i want that node D is able to receive the fragments from B and C and reassemble them together.
Do you have some idea how can i do this? Is it and issue of the DTN or in the protocols of routing?
Thank you in advance, Luis Guedes