When we invoke Channel.send(), we pass a bufffer to JGroups. At the transport level, JGroups marshals the sender and destination address, plus all headers and the buffer into a new byte[] buffer, which is then passed to the socket (DatagramSocket, MulticastSocket, Socket).

We cannot do gathering writes on a DatagramSocket because DatagramSocket doesn't expose this functionality, contrary to a DatagramChannel.

We could avoid having to copy the user's buffer by using gathering writes: effectively passing to the socket NIO ByteBuffers containing:
1: Src and dest address plus flags, plus possibly size
2: The marshalled headers
3: The buffer passed to JGroups by the user

We can obtain a gathering-write channel as follows:

ByteBuffer[] buffers; // contains the 3 byte buffers above
DatagramSocket sock;
DatagramChannel ch=sock.getChannel();
ch.write(buffers, 0, length); // length is the number of bytes of the total marshalled message

This is supported by a GatheringByteChannel.

I don't think there's currently a need to do scattered reads, but this needs to get investigated more. Also investigate whether MulticastSockets support gathering writes (whether they expose the correct DatagramChannel).