I am using HPA's tftp server for PXE boot. When I try downloading an image from my tftp server using curl, the transfer rate is less than 3 MB/s, even on my 1Gb network.

curl -o initrd.gz tftp://

Is this an inherent limitation of the tftp protocol, or can this be configured?

  • Same problem here,hpux and solaris tftp are really fast Linux tftp is ultraslow(slackware) – elbarna Dec 6 '14 at 23:54
  • Try to increase the maximum block size on the server (e.g. --blocksize 1468).
  • Check with server in debug mode, see if there are retransmits.
  • Check if you really have Gb connection end-to-end.
  • Test on a different client node.
  • Check if there is some other problem not related to tftp - try iperf, tcpdump, ethtool ...
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    setting --blocksize 1468 on the server alone did not help. I had to specify the block size on the client as well, i.e. curl --tftp-blksize 1468. Then I get around 6.5 MB/s. This still does not seem very impressive. With ftp, I get over 100 MB/s on the same machines. – Martin Vegter Mar 29 '14 at 11:29

iperf, jperf (java based iperf) and ethtool will help a ton in figuring this out!

TFTP is a "block by block" file transfer protocol which makes it a completely different beast from FTP/SFTP/FTPS. Each block that is transferred is checked(acknowledged) to make sure it made it across the link intact. If every little block of data is not perfect, those blocks get re-transmitted, slowing down your transfer considerably. I have gone up to a 16384 block size on a GB network link with no problems, but I have also had to knock that back considerably on less reliable GB links...the smaller the block size, the greater chance of a successful block transfer, thus less re-transmissions. It's a bit of a balancing act finding what works best on your network, but a little trial and error should make quick work of figuring that out!

This relates more to Windows as it involves TFTP Windowsizing (RFC 7440) to transmit more blocks at a time, but is a great guide to illustrating the process of figuring out the settings that are going to yield better transfers on your network. https://ccmexec.com/2016/09/tweaking-pxe-boot-times-in-configuration-manager-1606/

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