rsync is a program that is useful for backing up files over the network. It has plenty of options.
Limit the bandwidth used in kB/s
e.g. --bwlimit=9000 will cap the speed at 9000kB/sec. This leaves some slack on a 100Mbit connection.
rsync can be run via ssh. This provides an encrypted connection.
When running rsync over ssh, the network connection can become saturated as ssh traffic has higher priority than other traffic. I noticed other data such as MySQL data connections were timing out. To workaround this issue I used the bwlimit option to limit the bandwidth used.