Overview of NTP (Network Time Protocol)

NTP (Network Time Protocol) is considered to be a protocol, which would be utilized for synchronizing computer clock times in a network. It would be belonging to and is considered to be one of the oldest parts of the TCP/IP protocol suite. The term NTP would be applying to both the protocol as well as the client-server programs that would be running on computers. NTP was developed by David Mills at the University of Delaware in 1981 and is designed to be highly scalable and fault-tolerant.

How does NTP work?

The NTP client would be initiating a time-request exchange with the NTP server. As a result of this exchange, the client would be able to calculate the link delay as well as its local offset and adjust its local clock for matching the clock at the server's computer. As a rule, six exchanges over a period of about 5 to 10 minutes would be required for initially setting the clock.

Once synchronized, the client would be updating the clock about once every 10 minutes, basically would be requiring only a single message exchange additionally to client-server synchronization. This transaction would be occurring via the User Datagram Protocol on port 123. NTP would be also supporting broadcast synchronization of peer computer clocks. So, before we get to the features of NTP, if you are looking forward to appearing in the IT Certification Exam, you should opt for the training courses which are offered at the SPOTO Club.

Features of NTP

NTP servers, of which there would be thousands around the world, having access to highly precise atomic clocks as well as GPS clocks. Specialized receivers would be required to directly communicate with the NTP servers for these services. It isn’t practical or cost-effective for equipping every computer with one of these receivers. Instead, computers would be designated as primary time servers would be outfitted with the receivers, as well as they would be utilizing protocols like NTP to orchestrate the clock times of networked computers.

NTP would be utilizing UTC (Universal Coordinated Time) for synchronizing computer clock times with extreme precision, offering greater accuracy on smaller networks down to a single millisecond in a local area network as well as within tens of milliseconds over the internet. NTP doesn’t account for time zones, instead of relying on the host for performing such computations.

Hierarchy of time servers

Stratum levels

Degrees of separation from the UTC source would be defined as strata. A reference clock that would be receiving true time from a dedicated transmitter or satellite navigation system is categorized as stratum-0; a computer that would be directly linked to the reference clock is stratum-1; a computer that would be receiving its time from a stratum-1 computer is stratum-2, and so on. Accuracy would be reduced with each additional degree of separation.

In terms of security, NTP would be known to the vulnerabilities. The protocol could be exploited as well as utilized in denial-of-service attacks for two reasons:

First, it would be replying to a packet with a spoofed source IP address;

Second, at least one of its built-in commands would be sending a long reply to a short request.

Why is NTP important?

Accurate time across a network is considered to be quite important for many reasons; discrepancies of even fractions of a second could cause problems. For example, distributed procedures could be dependent on coordinated times for ensuring proper sequences are followed. Security mechanisms would be depending on consistent timekeeping across the network. File-system updates would be carried out by several computers also depending on synchronized clock times.

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