Dell Configuration Guide for the S4048–ON System 9.14.2.6

The protocol also coordinates time distribution in a large, diverse network with various 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 automatically selects the best of several available time sources to synchronize to. You can combine multiple candidates to minimize the accumulated error. Temporarily or permanently insane time sources are detected and avoided.

Dell EMC Networking recommends configuring NTP for the most accurate time. In Dell EMC Networking OS, you can configure other time sources (the hardware clock and the software clock).

Because most host time servers 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.

In order to facilitate error control and management of the subnet itself, each of these components is maintained separately in the protocol. They provide not only precision measurements of offset and delay, but also definitive maximum error bounds, so that the user interface can determine not only the time, but the quality of the time as well.

In what may be the most common client/server model, a client sends an NTP message to one or more servers and processes the replies as received. The server interchanges addresses and ports, overwrites certain fields in the message, recalculates the checksum and returns the message immediately. Information included in the NTP message allows the client to determine the server time regarding local time and adjust the local clock accordingly. In addition, the message includes information to calculate the expected timekeeping accuracy and reliability, as well as select the best from possibly several servers.

Following conventions established by the telephone industry [BEL86], the accuracy of each server is defined by a number called the stratum, with the topmost level (primary servers) assigned as one and each level downwards (secondary servers) in the hierarchy assigned as one greater than the preceding level.

Dell EMC Networking OS synchronizes with a time-serving host to get the correct time. You can set Dell EMC Networking OS to poll specific NTP time-serving hosts for the current time. From those time-serving hosts, the system chooses one NTP host with which to synchronize and serve as a client to the NTP host. As soon as a host-client relationship is established, the networking device propagates the time information throughout its local network.