HP-UX Internet Services Administrator's Guide (May 2010)

Stratum-2 and -3 Time Servers
Stratum-2 time servers use stratum-1 servers as their time source. Likewise, stratum-3
servers use stratum-2 servers as their time sources. The maximum stratum level a server
can have is 15.
Time Server Roles
An NTP time server can take different roles in its relationships with other time servers
in the synchronization subnet. A time server can take one or more of the following
roles:
• Server— Provides time to clients when requested. This role can be assumed by
time servers at various strata.
• Peer— 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.
• Client— 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 can
in turn provide synchronization to its clients or peers.
• Broadcaster— Provides time to the specified remote host, or more typically, the
broadcast address on a LAN. This role is most appropriate for an NTP time server
that provides time to workstation clients on a LAN.
• Broadcast Client— Listens for and synchronizes with the broadcast time. This role
is most appropriate for time server clients on a LAN.
NOTE: Broadcasting is not recommended especially when used with local clock
impersonators. Broadcasting is an old concept that is no longer used.
Figure 4-3 illustrates the relationship between time servers in a synchronized subnet.
Figure 4-3 Example of Relationships Between Time Servers
Advanced NTP Topics 59