Reference Guide

910 | System Time and Date
www.dell.com | support.dell.com
Each of these components are maintained separately in the protocol in order to facilitate error control and
management of the subnet itself. 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 with respect to 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 networking OS synchronizes with a time-serving host to get the correct time. You can set Dell
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.
Protocol Overview
NTP message to one or more servers and processes the replies as received. The server interchanges
addresses and ports, fills in or overwrites certain fields in the message, recalculates the checksum and
returns it immediately.
Information included in the NTP message allows each client/server peer to determine the timekeeping
characteristics of its other peers, including the expected accuracies of their clocks. Using this information
each peer is able to select the best time from possibly several other clocks, update the local clock and
estimate its accuracy.