Interrupt and DMA on Arduino Due

Official Hardware Mega Due
3

The code is a little bit complicated for whose who do not know the SSC peripheral quite deeply.
But what I found is this:
Transmission of UDP packets to Ethernet uses 3 commands:
Udp.beginPacket(destIP, localPort); //Listen incoming data

Udp.write(Txbuf, sizeof(Txbuf)); // Write buffer Txbuf to Ethernet

Udp.endPacket(); //Close transmission

The software is stuck at the second command.
If I use regular polling instead of interrupt, no problem but with the limitation of acquiring to Ethernet only one out of two packets.