I have ~70ms latency over my VPN connection and need to set up a backup/replication system. SMB is the worst, with throughput ~200KB/s. SCP gives me ~400KB/s. HTTP ~700KB/s. The links are symmetric 50mbit connections.

Is there any kind of file transfer protocol designed for this kind of high latency connection?


  • what does ftp look like?
    – tony roth
    Commented Jan 5, 2012 at 18:42
  • 2
    Stationwagon full of tapes. Commented Jan 5, 2012 at 18:48
  • 1
    Have you looked at WAN accelerators? Not inexpensive but can really help.
    – Dave M
    Commented Jan 5, 2012 at 20:01
  • How many files, and how small? Could be relevant.
    – Smithers
    Commented Apr 27, 2015 at 18:56

3 Answers 3


If you already have a VPN in-place, then ftp might be a valid choice.

A latency of ~70ms is not what I would call high though. SCP and http should perform far better then what you describe on a 50mb/s 70ms link. You may have some other problem. You might want to use iperf or something else that can test the raw capacity of your connection.

  • 3
    +1 for other problem. I regularly reach over 1MiB/s on 200+ms links. RSS should take care of latency, if there are lots of small files to transfer, than every protocol will be slow. tar them before transfer. If tarring doesn't help: you've got different problem. Commented Jan 5, 2012 at 21:01
  • 1
    +1. 70ms rtd is not that much and transfers over a 50Mb/s link shoud really be faster than what the OP states. Other problem here.
    – petrus
    Commented Jan 5, 2012 at 21:36
  • I for one do NOT think that you have another problem! While 70ms is indeed a good value, it still matters a LOT! Especially for small files! There's no way you can transfer more than 10 tiny small files per second, even though you have 50mb/s. Unless you use rsync or tar it. Just calculate one rountrip for open, one for close, one for each chunk for SMB. It really is that bad
    – Christian
    Commented Aug 21, 2012 at 21:38

I'd use tar

you can either create a tarfile and transfer it, or directly pipe the output throught netcat or similar tools.

The advantage is that the protocol won't do a lot of file-open handshakes.


I would probably use scp or rsync and the arcfour cipher.

  • If that's too tricky, robocopy can be setup to wait/retry if the connection drops, but robocopy is only clever enough to overwrite the whole of any changed file rather than just the changes.
    – Robin Gill
    Commented Jan 5, 2012 at 19:00

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