[dtn-interest] What's the actual effect of using custody transfer?

[Martin Galvan <[e-mail]>]

Hi everybody! I'm reading a bit on DTN and I have a doubt about what
custody transfer actually does. From what I've read, a node that accepts
custody of a bundle promises it won't delete the bundle until it can
forward the bundle to either its destination or another node that accepts
its custody. However, I don't see what would be the difference between
doing that and not using custody transfer. Isn't the whole purpose of a
store-and-forward mechanism to do just that?

For example, let's assume we have three nodes, A, B and C. There's no
end-to-end path from A to C, and A is directly connected to B.

A----->B     C

If I understood custody transfer right, if A wants to send C a bundle using
custody transfer, it will request B to accept custody of the bundle; if B
accepts it will store the bundle until a link to C can be established. Once
that happens, B will then forward the bundle to C and delete it once it's
reached its destination.

What would happen if A didn't want to use custody transfer?

Thanks a lot!