When multicast is slower than unicast

So I'm playing around with MDP (Multicast Dissemination Protocol) [1] and I am underwhelmed by its performance. I have it installed on five machines. The file I'm transfering is about 4.5MB in size and can be transferred in under 30 seconds using scp (and that's including the time it takes for me to type in a password), so to transfer the file to four machines (the fifth is doing the sending) should take around two minutes.

The first test I stopped after twelve minutes. Okay, so one of the machines is a bit flaky, so I decided to drop that one from the test and run the test again.

Ten minutes.

Also, because of the way multicast works, the sending process doesn't exactly end when the clients have the data just in case another process joins to receive the broadcast (I'm guessing, the documentation for MDP (Multicast Dissemination Protocol) is scant and the help feature doesn't work [2]) so this may not work for what we want to do.

[1] http://tang.itd.nrl.navy.mil/5522/mdp/mdp_index.html

[2] /boston/2005/04/11.1

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