Brocade FastIron Ethernet Switch Administration Guide - Manual (Page 37)

NTP uses the concept of associations to describe communication between two machines running NTP.
NTP associations are statistically configured. On startup or on the arrival of NTP packets, associations
are created. Multiple associations are created by the protocol to communicate with multiple servers.
NTP maintains a set of statistics for each of the server or the client it is associated with. The statistics
represent measurements of the system clock relative to each server clock separately. NTP then
determines the most accurate and reliable candidates to synchronize the system clock. The final clock
offset applied for clock adjustment is a statistical average derived from the set of accurate sources.
When multiple sources of time (hardware clock, manual configuration) are available, NTP is always
considered to be more authoritative. NTP time overrides the time that is set by any other method.
NTPv4 obsoletes NTPv3 (RFC1305) and SNTP (RFC4330). SNTP is a subset of NTPv4. RFC 5905
describes NTPv4.
To keep the time in your network current, it is recommended that each device have its time
synchronized with at least four external NTP servers. External NTP servers should be synchronized
among themselves to maintain time synchronization.
NOTE
Network Time Protocol (NTP) commands must be configured on each individual device.
Basic Software Features
FastIron Ethernet Switch Administration Guide 37
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