This service has been running for approximately three years. The domestic source is available for sup and ftp for USA users on sup.netbsd.org and ftp.netbsd.org, and for Australian users on sup.au.netbsd.org and ftp.au.netbsd.org. Timing Deltas are built once per day in the early hours of the morning Eastern Australian time. No deltas are created if there are no changed files. There are manual pages for the individual ctm commands.
Some additional information is available in the FreeBSD handbook .
Setup Choose a directory to hold the deltas. Don't bother to uncompress it. In general any time you miss a delta due to mail accident or whatever, just ftp it. Choose a directory to unpack into. In the new directory run ctm on all the deltas you ftp'd.