Video: Keeping Time with PTP

Different from his talk of the same name we covered last week, Mike Waidson from Telestream explains the fundamentals of PTP joined by Leigh Whitcomb from Imagine Communications and Robert Welch from Arista. Very few PTP talks include a live BCMA quiz plus, with more time than the IP Showcase talks, this is a well-paced, deep look into the basics.

Mike starts by reviewing how the measurement of time has been more and more accurately measured with us now, typically using atomic clocks. In the TV-domain analogue video used signals for B&B which gave frequency information in the subcarrier and allowed frequency locking and to keep in sync with other signals. NTP has allowed computers and routers on IP networks to keep lock allowing sub-millisecond synchronisation over LANs. Now we have IEEE 1588 PTP which harnesses hardware for maximum precision providing sub-microsecond precision.

Traditionally an SPG would create many different synchronising signals, distributed by DAs. With PTP however, the idea is creating a single time signal on to the network (as well as older signals if necessary). Although, the important thing to remember is that PTP both sends and receives data from the endpoints. GPS is made from 31 active satellites of which only 4 are needed for a lock. But other systems such as the Russian GLONASS, the Chinese BAIDU Navigational system or the European Galileo can also be used, sometimes in conjunction with each other to improve locking speed or give resilience.

Mike and his co-hosts give an overview of the standards that make all this possible, starting with the PTP standard itself IEEE 1588-2019 which is added to by SMPTE 2059. The latter is two standards that, together ensure broadcast devices can usefully harness PTP which is a general, cross-industry standard and track all signals back to a single point in time in 1970. Whilst this may seem extreme, the benefit of doing this is that if we know that all possible types of signal were in-phase at this one point in time, we can extrapolate how each signal should be phased now and use that information to synchronise the system. Upcoming to PTP, we hear, are standardised ways to monitor PTP plus additional security around the standard.

The next section looks at the types of Grandmaster and the fact that each clock works in its own domain. Typically, all your system will be in the same domain, but if you have incompatible situations such as older Dante networks or if you want to have a testing environment, you can use domains to separate your equipment. The standard, as defined by SMPTE 2059 is 127.

Mike then looks at the different types of PTP Message types: Announce, Sync & Follow up, Delay Request, Delay Response and Management Messages (broadcast information, drop second, time zone etc.) He then brings some of these up in Wireshark and talks us through the structure and what can be found within.

The most original part of the talk is the live walkthrough of three different scenarios where Leigh and Robert talk through their thinking on which clock will be the grandmaster and for what reason. This comes down to their understanding of the order of precedence of the metrics such as the manually-allotted priority, then the class of clock, clock accuracy and other values. One value worth remembering is that if your clock is locked to GPS it will have a class of 6, but if it then loses lock, it will become 7.

PTP talks are not complete without an explanation of the sync message exchanges needed to actually determine the time (and the relative delays in order to compute it) as well as the secondary clock types, boundary and transparent. Boundary clocks take on much of the two-way traffic in PTP protecting the grandmasters from having to speak directly to all the, potentially, thousands of devices. Transparent switches, simply update the time announcements with the delay for the message to move through the switch. Whilst this is useful in keeping the timing accurate, it provides no protection for the grandmasters.

Before the talk finishes with a Q&A, the team finish by explaining the difference between operating in unicast and multicast, prioritising PTP traffic using the differentiated services protocol and adding redundancy to the PTP system.

Watch now!
Free registration required

Robert Welch Robert Welch
Technical Solultions Lead,
Leigh Whitcomb Leigh Whitcomb
Principal Engineer.
Michael Waidson Mike Waidson
Application Engineer,

Video: Keeping Time with PTP

The audio world has been using PTP for years, but now there is renewed interest thanks to its inclusion in SMPTE ST 2110. Replacing the black and burst timing signal (and for those that used it, TLS), PTP changes the way we distribute time. B&B was a waterfall distribution, PTP is a bi-directional conversation which, as a system, needs to be monitored and should be actively maintained.

Michael Waidson from Telestream (who now own Tektronix) brings us the foundational basics of PTP as well as tips and tricks to troubleshoot your PTP system. He starts by explaining. the types of messages which are exchanged between the clock and the device as well as why all these different messages are necessary. We see that we can set the frequency at which the announce, sync and follow-up messages. The sync and follow-up messages actually contain the time. When a device receives one of these messages, it needs to respond with a ‘delay request’ in order to work out how much of a delay there is between it and the grand master clock. This will result in it receiving a delay response. On top of these basic messages, there is a periodic management message which can contain further information such as daylight savings time or drop-frame information.

Michael moves on to looking at troubleshooting highlighting the four main numbers to check: The domain value, grandmaster ID, message rates and the communication mode. PTP is a global standard used in many industries. To make PTP most useful to the broadcast industry, SMPTE ST 2059 defines values to use for message repetition (4 per second for announce messages, 8 for sync, delay request and delay response). ST 2059 also defines how devices can determine the phase of any broadcast signal for any given time which is the fundamental link needed to ensure all devices keep synchronicity.

Another good tip from Michael is if you see the grandmaster MAC changing between the grandmasters on the system, this indicates it’s no receiving any announce messages so is initiating the Best Master Clock Algorithm (BMCA) and trying the next grandmaster. Some PTP monitoring equipment including from Meinberg and from Telestream can show the phase lag of the PTP timing as well as the delay between the primary and secondary grandmaster – the lower the better.

A talk on PTP can’t avoid mentioning boundary clocks and transparent switches. Boundary clocks take on much of the two-way traffic in PTP protecting the grandmasters from having to speak directly to all the, potentially, thousands of devices. Transparent switches, simply update the time announcements with the delay for the message to move through the switch. Whilst this is useful in keeping the timing accurate, it provides no protection for the grandmasters. He finishes video ends with a look at how to check PTP messages on the switch.

Watch now!

Michael Waidson Michael Waidson
Application Engineer
Telestream (formerly Tektronix)

Video: ST 2110 Test and Measurement Super Session

This IP Showcase super session consists of six presentation from six different vendors which focus on specific aspects of test or measurement that is unique for ST 2110 environment. It is worth noting that these are technology presentations, not product presentations.

The session is led by Willem Vermost from EBU. He describes what kind of issues we need to solve in a SMPTE ST 2110 environment in terms of testing and monitoring. He speaks about PTP accuracy, traffic shaping (SMPTE ST 2110-21) and SMPTE ST 2022-7 redundancy.

Next, Michael Waidson from Tektronix focuses on Precision Time Protocol (PTP) which is a cornerstone of synchronisation of IP media networks. He walks us through Best Master Clock algorithm, boundary and transparent clocks plus PTP fault finding. (You might also want to watch the Monitoring and Measuring IP Media Networks presentation by Michael which we recently published on The Broadcast Knowledge.)

Furthermore, Jack Douglass from PacketStorm talks about ST 2110-21 traffic shaping measurements. He also shows how to use network emulation tools for testing ST 2022-7 link redundancy (the same data is sent through two separate paths of network emulation that are synchronised together, then burst loss are generated using RTP sequence number, with the least important bit different on both paths).

The next speaker is Ståle Kristoffersen from Bridge Technologies. He focuses on live performance monitoring in a ST 2110 network – does the signal make sense? (IP headers, RTP headers, ST 2110-20/30/40 essences), do all of the signals arrive? (packet loss, monitoring packet loss on 2022-7 links), does the signal arrive on time? (late can be just as bad as a packet loss) amongst others.

Moreover, Kevin Salvidge from Leader shows the differences in monitoring in an SDI and an all-IP facility. He compares single essence per BNC with multiple essences per fibre, synchronous and asynchronous transport and causes for errors (cable loss and impedance mismatch vs error packet loss and network overload). He also emphasises the need for accuracy of PTP and explains how to measure it.

Last but not least, Adam Schadle from Video Clarity walk us through video / audio performance and quality methods. He shows how to use picture and sound quality objective tests to understand network behaviour.

The presentations are followed by Q&A session.

See the slides here.

Watch now!


Willem Vermost Willem Vermost
Senior IP Media Technology Architect
Michael Waidson
Application Engineer
Jack Douglass
VP Marketing and Business Development
Ståle Kristoffersen Ståle Kristoffersen
Lead Software Developer
Bridge Technologies
Kevin Salvidge
European Regional Development Manager
Adam Schadle
Vice President
Video Clarity

Video: Monitoring and Measuring IP Media Networks


The transition from point-to-point SDI based infrastructure to IP essence flows requires a very different approach to fault-finding. Although new IP diagnostic tools are already available on the market, engineers need combined broadcast and IT knowledge to fully understand the flow of video, audio and data across the switching fabric – including packet jitter, latency, and buffer over/underflows causing dropped packets.

In this video Michael Waidson from Tektronix presents methodologies involved in monitoring IP media networks. The following topics are covered:

  • Strategies for choosing IP Address, Port Number and Payload Type for easier identification of the streams
  • Troubleshooting basics (fibres and SFPs types, checking switch ports)
  • PTP synchronisation
  • Checking syntax of decoded streams (Layer 5 RTP, Marker Bit, Payload Type, Sequence Number, Timestamp)
  • Packet transmission (multiple paths, out of order packets in receiver, jitter, PIT Histogram)
  • Timing (reference clock, RTP timestamps, checking PTP lock, PTP and RTP offset, transmission traffic shape models)

You can download the slides here.


Michael Waidson
Application Engineer