Wednesday, 17 Jul 2024

Use Best Practices for Network Time Protocol


Network Time Protocol (NTP) is a crucial component of IP-based networks, ensuring accurate time synchronization for performance analysis and network behavior characterization. This article describes the best practices to design and manage NTP for optimal performance and reliability.


  • Knowledge of Network Time Protocol
  • Understanding of clock technology and public time servers

Background Information

Internet Protocol (IP) based networks have evolved from the traditional “best effort” delivery model to one that requires quantifiable performance and reliability. Accurate time synchronization is essential for modern performance analysis and is considered a competitive service differentiator. However, the often-overlooked principle of time synchronization can undermine network management efforts. This document outlines a hypothetical process definition for NTP management, offering guidance for organizations to meet their internal objectives.


  • Accuracy: Proximity of the clock absolute value to zero offset.
  • Accurate: Clock offset at zero at a specific time.
  • Drift: Variation of skew or second derivation of clock offset with respect to time.
  • Joint resolution: Sum of resolutions of two clocks when compared.
  • Node: An instantiation of the NTP protocol on a local processor.
  • Offset: Difference between clock-reported time and true time.
  • Peer: NTP protocol instantiation on a remote processor.
  • Resolution: Smallest unit by which a clock time is updated.
  • Skew: Clock frequency difference or first derivative of offset with respect to time.
  • Synchronize: When two clocks are accurate with respect to each other.
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Device Overview

The heart of the time service is the system clock, which tracks the current date and time and can be set from various sources. The system clock can distribute time to other systems and provides time to NTP, VINES time service, user commands, logging, and debugging messages. The system clock’s accuracy and reliability are crucial for proper time distribution.

NTP Overview

NTP is designed to synchronize time on a network of machines by running over UDP. It uses a set of distributed time servers and clients to achieve timekeeping synchronization. NTP networks typically obtain time from authoritative sources and distribute it across the network. NTP detects and synchronizes clocks based on stratum and performs well over WANs and LANs.

NTP Design Criteria

NTP design should ensure multiple lower stratum time sources, select reliable synchronization sources, and avoid synchronizing with unreliable peers. An NTP architecture can have a flat peer structure, hierarchical structure, or star structure. Lower stratum servers are preferred, considering their synchronization and accuracy.

Example NTP Deployments

  • WAN Time Distribution Network: NTP time obtained from public servers synchronizes corporate AS time servers in an OSPF hierarchy.
  • High Stratum Campus Time Distribution Network: The NTP hierarchy follows an OSPF hierarchy, with servers synchronized to area time servers and client devices using the broadcast option.
  • Low Stratum Campus Time Distribution Network: GPS or Cesium time sources provide stratum 1 time sources for a private network.
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Process Definitions

  • Create the NTP Design: Create a detailed design document for the NTP architecture that meets requirements and cost objectives.
  • Create a Seed File: Create a seed file to identify and prioritize network devices involved in the NTP architecture.
  • Baseline NTP Performance Parameters: Baseline variable parameters to set thresholds for abnormal conditions.

Task Definitions

  • Maintain the Seed File: Update the seed file to reflect network changes impacting the NTP architecture.
  • Execute the NTP Node Scan: Collect NTP information for critical, interesting, and configuration scans at different frequencies.
  • Review the NTP Node Reports: Analyze critical, interesting, and configuration reports for stability and initiate corrective actions.

Data Identification

  • SNMP Data Identification: Retrieve NTP information using SNMP queries for system group and peer group variables.

Data Collection

  • SNMP Data Collection: Use SNMP queries to collect NTP information for critical, interesting, and configuration scans.

Data Presentation

  • NTP Critical Node Report: Report on critical nodes’ NTP data, grouped by OSPF areas.
  • NTP Interesting Node Report: Report on interesting nodes’ NTP data, grouped by OSPF areas.
  • NTP Configuration Report: Comprehensive report on the overall NTP architecture, verifying deployment against design records.

Frequently Asked Questions

  • Can I synchronize multiple NTP servers in a hierarchical structure?
    Yes, a hierarchical structure is recommended for consistent, stable, and scalable NTP architecture. Core servers synchronize with external time sources, internal servers synchronize with core servers, and so on down the hierarchy.

  • How can I ensure accuracy and stability in my NTP deployment?
    Baseline NTP performance parameters, maintain the seed file, and regularly review NTP node reports to identify and address any issues.

  • What are the advantages of using broadcast mode in NTP?
    Broadcast mode simplifies configurations for LANs by allowing all operative clients to use the same configuration file. However, accuracy in performance measurements may be reduced.

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Implementing best practices for NTP design and management ensures accurate time synchronization and reliable network performance. By following the guidelines outlined in this article, organizations can optimize their NTP architecture and minimize potential issues. For more information, visit Eireview.