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Questions and Answers
What is typically considered a Stratum 0 device in the context of time synchronization?
What is typically considered a Stratum 0 device in the context of time synchronization?
Which protocol is primarily used for synchronizing clocks over a network?
Which protocol is primarily used for synchronizing clocks over a network?
What role does the Global Positioning System (GPS) serve in network time synchronization?
What role does the Global Positioning System (GPS) serve in network time synchronization?
In the context of time synchronization, what does the term 'delay' refer to?
In the context of time synchronization, what does the term 'delay' refer to?
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What is the function of the domain name of a time server in network synchronization?
What is the function of the domain name of a time server in network synchronization?
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What is the primary source of accurate time used in network synchronization?
What is the primary source of accurate time used in network synchronization?
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Which system utilizes satellite signals to assist in time synchronization?
Which system utilizes satellite signals to assist in time synchronization?
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In network time synchronization, what does the term 'delay' most commonly refer to?
In network time synchronization, what does the term 'delay' most commonly refer to?
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What is the role of the domain name of a time server in the synchronization process?
What is the role of the domain name of a time server in the synchronization process?
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Which layer of time sources does a Stratum 0 device belong to?
Which layer of time sources does a Stratum 0 device belong to?
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Study Notes
Network Time Protocol (NTP)
- NTP is the most common method for synchronizing clocks on computers, laptops, smartphones, tablets, and smart TVs.
- It's one of the oldest internet protocols still in use today.
- Developed by David L. Mills at the University of Delaware in the 1980s.
- A client polls one or more NTP servers to get the correct time.
- Accuracy is measured in tens of milliseconds (e.g., 50ms, 80ms).
Precision Time Protocol (PTP)
- Uses special hardware to create timestamps (not software), making it more accurate.
- A "Grandmaster" device is designated as the most reliable time source and sends synchronization messages to other devices ("followers").
- Unlike NTP, PTP clients don't ask servers for time; the Grandmaster pushes time to "followers".
- Accuracy is better than 1 microsecond (measured in nanoseconds).
- PTP is used for sub-nanosecond accuracy in applications like industrial automation, audio/video broadcasting, and financial trading.
- The White Rabbit Network (CERN) uses PTP.
How NTP Works
- A client sends a request to a time server.
- The server processes the request and sends a reply.
- The client receives the reply.
Time Delays
- Network delays affect time synchronization.
- Time is required for requests to reach servers, for servers to process requests, and for replies to reach clients.
- Clients must consider delays when attempting to synchronize time.
Time Synchronization Calculations
- Offset: Calculation to adjust for delays. Accounts for both request and response times.
- Round Trip Delay: Time taken for the request and reply to travel back and forth.
- Timestamps from both client and server are used to calculate offset and delays.
Stratum Levels
- Stratum 0: Global Navigation Satellite System (GNSS) like GPS, GLONASS, etc., providing high-precision time.
- Stratum 1 (primary time servers): Servers connected to Stratum 0 devices offering time synchronization services over a network.
- Stratum 2 and 3: Servers connected to Stratum 1 devices, further disseminating synchronized time to connected devices.
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Description
Explore the differences between Network Time Protocol (NTP) and Precision Time Protocol (PTP) in this quiz. Learn about their functionalities, accuracy levels, and applications in various technologies. Test your knowledge on how these protocols synchronize time in modern devices.
