Installing and Administering Internet Services

Chapter 7 299

Conﬁguring the Network Time Protocol (NTP)

Advanced NTP Topics

The maximum stratum level a server can have is 15.

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— 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 may, 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 to 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 older concept that is no longer used.

Figure 7-3 illustrates relationships between time servers in a

synchronization subnet.