Reference Guide

System Time and Date | 913

System Time and Date

System Time and Date settings, and Network Time Protocol are supported on the S5000 switch.

System times and dates can be set and maintained through the Network Time Protocol (NTP). They are

also set through FTOS CLIs and hardware settings.

This chapter includes the following sections:

• Network Time Protocol

• Configuring Network Time Protocol

• FTOS Time and Date

Network Time Protocol

Network Time Protocol (NTP) synchronizes timekeeping among a set of distributed time servers and

clients. The protocol also coordinates time distribution in a large, diverse network with a variety of

interfaces. In NTP, servers maintain the time and NTP clients synchronize with a time-serving host. NTP

clients choose from among several NTP servers to determine which offers the best available source of time

and the most reliable transmission of information.

NTP is a fault-tolerant protocol that will automatically select the best of several available time sources to

synchronize to. Multiple candidates can be combined to minimize the accumulated error. Temporarily or

permanently insane time sources will be detected and avoided.

Dell Networking recommends configuring NTP for the most accurate time. In FTOS, other time sources

can be configured (the hardware clock and the software clock).

NTP is designed to produce three products: clock offset, roundtrip delay, and dispersion, all of which are

relative to a selected reference clock.

• Clock offset represents the amount to adjust the local clock to bring it into correspondence with the

reference clock.

• Roundtrip delay provides the capability to launch a message to arrive at the reference clock at a

specified time.

• Dispersion represents the maximum error of the local clock relative to the reference clock.

Since most host time servers will synchronize via another peer time server, there are two components in

each of these three products, those determined by the peer relative to the primary reference source of

standard time and those measured by the host relative to the peer.