Tag Archives: Guest Post

NTS Published as Standard

This is a guest blogpost by Martin Langer, Ph.D. student for “Secured Time Synchronization Using Packet-Based Time Protocols” at Ostfalia University of Applied Sciences, Germany.


The Internet Engineering Task Force (IETF) published the Network Time Security protocol (NTS) as RFC 8915 on October 1, 2020. This new standard offers security mechanisms for the widely used Network Time Protocol v4 (NTPv4), which has been operated mostly unsecured until now. After almost eight years of development, global collaboration, and many interoperability tests of leading NTP software developers, NTS represents a mature security protocol. In this post, I’ll give you a short overview of the development progress of NTS and provide a list of public implementations and NTS secured time servers…

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NTP Filtering (Delay & Blockage) in the Internet

NTP (Network Time Protocol) messages are sometimes rate-limited or blocked entirely by Internet operators. This little-known “NTP filtering” was put into place several years ago in response to DDoS (Distributed Denial of Service) attacks. NTP filtering may drop NTP messages based on rate or message size. Let’s dig into it: Continue reading NTP Filtering (Delay & Blockage) in the Internet

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Setting up NTS-Secured NTP with NTPsec

This is a guest blogpost by Martin Langer, Ph.D. student for “Secured Time Synchronization Using Packet-Based Time Protocols” at Ostfalia University of Applied Sciences, Germany.


In the previous posts, I already introduced the Network Time Security (NTS) protocol and described the most important features. Although the specification process has not been completed, there are already some independent NTS implementations and public time servers (IETF106). NTPsec is one of the important representatives of this series and already offers an advanced NTS solution. In this post, I’ll give you a short guide to setting up an NTS-secured NTP client/server with NTPsec.

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Intro to NetworkMiner

This is a guest blogpost by Erik Hjelmvik, an expert in network forensics and network security monitoring at NETRESEC.


Wireshark is the default goto tool for analyzing captured network traffic for most network engineers. But there are a few other free and open source alternatives that are sometimes overlooked, one of which is NetworkMiner (disclaimer: I’m the creator of NetworkMiner).

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Network Time Security – Strengths & Weaknesses

This is a guest blogpost by Martin Langer, Ph.D. student for “Secured Time Synchronization Using Packet-Based Time Protocols” at Ostfalia University of Applied Sciences, Germany.


The Network Time Security protocol (NTS) is close to completion as an Internet standard and will replace the existing security mechanisms in NTP. The introductory article on NTS describes the basic communication process as well as the most important features. Despite high-security efforts, NTS also has its limitations. In this blogpost, I list the strengths and weaknesses of the new authentication mechanism and describe them briefly.

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Network Time Security – New NTP Authentication Mechanism

This is a guest blogpost by Martin Langer, Ph.D. student for “Secured Time Synchronization Using Packet-Based Time Protocols” at Ostfalia University of Applied Sciences, Germany.


In many areas, the use of authentication mechanisms in NTP is important to prevent the manipulation of time information by an attacker. For many years, NTP has been offering solutions such as a Symmetric Key based method and the Autokey approach. However, both have serious disadvantages, for which reason they are rarely used to secure NTP connections. After years of development, a new standard is to be adopted in 2020 that solves the problems of the current mechanisms and offers a real alternative. First implementations of the so-called Network Time Security protocol (NTS) are already available and interoperate with each other …

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NTP Server’s Delta Time

This is a guest blogpost by Jasper Bongertz. His own blog is at blog.packet-foo.com.


Running your own NTP server(s) is usually a good idea. Even better if you know that they’re working correctly and serve their answers efficiently and without a significant delay, even under load. This is how you can use Wireshark to analyze the NTP delta time for NTP servers:

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F5 BIG-IP Application Level NTP Health Checks

When configuring a pool of NTP servers on a F5 BIG-IP load balancer you need to choose how to check if they are still up and running. There is no specific NTP monitor on a F5 BIG-IP that does an application layer health check (like there is for http or radius). The out-of-the-box options that can be used are only ICMP and UDP monitoring. Let’s first look at the pros and cons of using either (or both) of these monitors. Then let’s build a custom UDP monitor that does a better job at checking whether the NTP servers are still healthy.

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