A while ago I've been involved in an interesting discussion focusing on NTP authentication and whether you can actually implement it reliably on Cisco IOS. What I got out of it (apart from a working example :) was the feeling that NTP and it's implementation in Cisco IOS was under-understood and under-documented, so I planned to write an article about it.
However, as I did my research, I figured out there's so much I didn't know about NTP (do you know what's the essential difference between a peer and a server?)that I decided to start with an introductory article explaining the basics of NTP, SNTP and their IOS implementation. It's been published under the name “It’s Good to be on Time” in the IP corner section of our company's web site.