* DNS resolvers ( http://en.wikipedia.org/wiki/Domain_Name_System )
* FTP / network backup
* NTP service ( http://en.wikipedia.org/wiki/Network_Time_Protocol )
Operating System Updates:
* Yum repositories for Red Hat Linux based systems
* Apt mirrors for Debian Linux based systems
* Windows service packs/hotfixes
* Critical security updates
* Uptime & service monitoring
