Installing and Administering Internet Services

Chapter 7 211
Configuring NTP
Overview
Time Server Roles
An NTP time server can assume different roles in its relationships with
other time servers in the synchronization subnet. A time server can
assume one or more of the following roles:
• Server—The local host provides time to clients when requested. This
role can be assumed by time servers at various strata. The server role
is illustrated in Figure 7-2.
Figure 7-2 Local Host as Server
• Peer—The local host obtains time from a specified server and
provides time to that server, if requested. This role is most
appropriate for stratum-1 and stratum-2 servers or for time servers
that are interconnected via multiple network paths. The peer role is
illustrated in Figure 7-3.
Figure 7-3 Local Host as Peer
• Client—The local host obtains time from a specified server, but does
not provide time to that server. This role is appropriate for time
servers that obtain time from a server of a lower-numbered stratum
(for example, a stratum-1 server). The local host may, in turn, provide
synchronization to its clients or peers. The client role is illustrated in
Figure 7-4.
Figure 7-4 Local Host as Client
Local Host
Remote Host
Time
Local Host
Remote Host
Time
Local Host
Remote Host
Time