HP-UX Internet Services Administrator's Guide (August 2003)

Conﬁguring NTP

Advanced NTP Topics

Chapter 476

time source can be a device such as a radio receiver. Figure 4-2 shows the

relationship between the GPS receiver time source and the stratum-1

server associated with it.

Figure 4-2 Stratum-1 Time Servers

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.

Stratum 1

Server

Stratum 2

Server

Stratum 2

Server

external

clock

--Stratum 0

Server