Service updates and lookups are provided through the FortiGuard Distribution Network (FDN). The FDN is a global network of FortiGuard Distribution Servers (FDS) providing current antivirus and intrusion prevention and detection engines and signatures, Web Filtering and email filtering rating databases and lookups, and firmware images. If you deploy your FortiManager unit to be a private FDS, the FortiManager unit will synchronize available updates with the FDN, then provide FortiGuard updates to your managed devices. Using a private FDS provides a faster connection to your security infrastructure.