Five-minute facts about packet timingNetwork Time Protocol version 4 (RFC 5905) is a spectacularly successful network time transfer protocol. It can be found in almost every IP network. Often NTP messages will traverse leased lines or the “public internet”. Therefore, it is especially important that an NTP client can determine that the NTP server is […]
Implementing PRP devices and networks
5 minute facts about packet timing In a previous post I talked about the new redundant networking protocols High Availability Seamless Redundancy (HSR) and Parallel Redundancy Protocol (PRP). These protocols are defined in the IEC 62439-3 standard. Today I want to talk in more detail about PRP devices and networks. Recall that a PRP network […]
The Root of All Timing: Understanding root delay and root dispersion in NTP
Five Minute Facts About Packet Timing If you examine an NTP packet you will see the fields root delay and root dispersion. See the diagram from RFC 5905 in Figure 1 bellow, which defines NTP version 4, the current version. You might ask what is with all this “root” stuff? Root in this case refers […]
Unicast Master Port Selection in PTP: When should a slave port swipe right
Five Minute Facts About Packet Timing In multicast PTP a slave port need only subscribe to the PTP multicast addresses and timing will come to it. However, in unicast PTP a slave port has to reach out to the master port it wants time from with PTP message requests. It is more of a client-server […]
What’s new in IEEE 1588-2019: L1 Sync
Five Minute Facts About Packet Timing Time to play what’s new in IEEE 1588-2019, the game where everyone wins new PTP features. L1 Sync is short for physical layer frequency synchronization. Recall that frequency sync is also referred to as syntonization. So, what is it? First, two clocks are syntonized if the they have the […]
What’s in IEEE 1588-2019: DIY PTP Port States
Five Minute Facts About Packet Timing In this installment of What’s in IEEE 1588-2019 we look at the exciting and dangerous world of manual port state configuration1. The Best Master Clock Algorithm leaving you uninspired? No longer a problem, you can configure the state of every PTP Port in your network to be whatever you […]
The PTP AUTHENTICATION TLV
Five Minute Facts About Packet Timing This is the next installment in our series: what is in the 2019 edition of IEEE 1588. Recently, I posted a discussion about GNSS spoofing, and what to do about it. However, the radio interface is not the only way that a hacker could disrupt the timing on your […]
GNSS Spoofing and how to mitigate it
Five Minute Facts About Packet Timing In a previous post I talked about GNSS jamming and how to mitigate it. Today I will discuss GNSS spoofing. Once again GNSS means Global Navisgation Satellite System, which includes not only GPS, but similar systems like the European Galileo. GNSS jamming is bad, but at least you always […]
GNSS jamming and how to mitigate it
Five Minute Facts About Packet Timing This post discusses GNSS jamming, for a discusstion of GNSS Spoofing see the follow up post. Before a timeserver transmits messages with timing information it usually gets that information from a GNSS receiver. That is a Global Navigation Satellite System. Such systems include the Global Positioning System (GPS), Galileo, […]
The Sync Monitor reverse PTP mechanism
Five Minute Facts About Packet Timing By Doug Arnold Since timing is a critical component of many networked systems, there is a desire among network operators to measure the time distribution performance in their networks. This includes logging time compliance for regulations such as MiFID II, as well as well as for general performance monitoring. To […]