Reliable Multicast over local network

I am implementing a messaging system using C++ and Qt. After much thought, I have determined that multicasting or a multicast-style technique will work best to solve my problem. However, I have learned about UDP's unreliability and believe it to be unacceptable.

My requirements are as follows:

• Messages are to be sent in a binary serialized form.
• From any given node on the network, I must be able to send messages to the other nodes.
• Message delivery must be insured.

I have heard of OpenPGM and NORM as alternatives for UDP. If anyone has experience with either of these, could you please share?

I am also open to the possibility of implementing "reliable" multicast by myself, in the application layer, but I would prefer not to if there is a library that already implements this.

I am using C++ and Qt, therefore .NET or Java-based solutions are not acceptable unless they are open-source and I may port them to C++.

Thank you very much.

EDIT 20120816T1853 MDT: An additional question: would either PGM or NORM have to be implemented at the hardware/IP level? Or can they be overlayed on top of existing protocols?

We have implemented our own reliable multicast protocol over UDP called RSP, since we needed something cross-platform and at the time couldn't find a good solution between Linux and Windows. The Windows PGM implementation disconnects slow clients which leave the send window, whereas our implementation throttles the sender similar to TCP. Afaik OpenPGM can be configured to do the same.