Network Time Synchronization

Importance of Synchronization

• All network devices (computers, printers, routers, switches) have clocks displaying date and time.
• Synchronization of these clocks is critical to ensure log files are consistent.
• Some servers require closely synchronized times for authentication.
• Accurate time stamps are essential for diagnosing outages.

Automatic Updates

• Local systems usually update time automatically, managed by system and network administrators.
• Administrators decide update frequency and the servers used for synchronization.

Network Time Protocol (NTP)

• NTP Protocol: Used for time synchronization on networks.
• NTP Server: Listens on UDP port 123, provides time updates without modifying its own time.
• NTP Client: Requests time updates from NTP servers and adjusts its time accordingly.
• Devices can function as both NTP clients and servers.
• Important to identify roles (client, server, or both) for network devices.

Accuracy and Stratum Values

• Stratum Value: Indicates the accuracy of an NTP server.
  • Stratum 0: Atomic clocks (e.g., GPS clocks, US Naval Observatory).
  • Stratum 1: Devices synchronized to Stratum 0, primary time servers.
  • Stratum 2 and beyond: Incrementally less accurate as the stratum value increases.
• Most networks use Stratum 1 and 2 devices.

Configuration on Local Devices

• Local computers often act as NTP clients.
• Configuration settings typically show the NTP servers used for synchronization.
• Multiple servers can be listed for redundancy; the lowest stratum server is usually preferred.

Considerations for Large Networks

• Large networks may have their own NTP servers referencing specific stratum devices.
• The choice of which NTP server to use would depend on the stratum level for accuracy.
• Devices will generally synchronize with the server having the lowest stratum value available.