All Internet-Drafts are available via ftp, http, and rsync. This page provided details about these services, including locations and instructions related to I-D mirrors.
rsync.ietf.org is updated 4 times per day.
The updates usually take about an hour to complete. However, due to network load, and data volume, your mileage may vary.
The rsync usually completes by 0300, 1100, 1600, 1900. All times are Eastern. (UTC: 0200, 0800, 1600, 2100).