Installing and Administering Internet Services

300 Chapter7
Configuring the Network Time Protocol (NTP)
Advanced NTP Topics
Figure 7-3 Example of Relationships Between Time Servers
Planning a Multiple-Server NTP Configuration
The following are guidelines that you should consider when planning
your configuration:
• Every NTP hierarchy must have at least one stratum-1 server. You
may configure your administrative domain to have outside sources of
synchronization which ultimately link to stratum-1 server(s), or you
may implement your own hierarchy of NTP time servers with one or
more stratum-1 servers.
• Configure at least three time servers in your administrative domain.
It is important to provide multiple, redundant sources of time
synchronization. NTP is specifically designed to select an optimal
source of synchronization from several potential candidates. Each
time server should be a peer with each of the other time servers.
• For each time server, select 1-3 outside sources of synchronization.
This assures a relative degree of reliability in obtaining time,
especially if you can select sources that do not share common paths.
The sources should operate at a stratum level that is one less than
the local time servers.
• The outside sources of synchronization should each be in different
Stratum 1
Stratum 2
Stratum 3
Gordo
Penelope
Golden
Hugo
(server)
(server)
(client)
(client)
(peer) (peer)
(broadcaster)
(broadcaster)
(broadcast client)
Bonita