TFTP is a UDP based file transfer protocol that uses a stop-and-wait and a simple retry loop, if you use only that you risk hitting congestion very fast and having a hard time to fix it.
The suggestions above to use iPXE and switch to TCP transfer methods such as HTTP make a lot of sense in that aspect.
The suggestions above to use iPXE and switch to TCP transfer methods such as HTTP make a lot of sense in that aspect.