Robert Welch Archives – The Broadcast Knowledge

Video: The Future Impact of Moore’s Law on Networking

Posted on 1st July 2021 by Russell Trafford-Jones

Many feel that Moore’s law has lost its way when it comes to CPUs since we’re no longer seeing a doubling of chip density every two years. This change is tied to the difficulty in shrinking transistors even more when their size is already close to some of the limits imposed by physics. In the networking world, transistors are bigger so which is allowing significant growth in bandwidth to continue. In recent years we have tracked the rise of 1GbE which made way for 10GbE, 40GbE and 100 Gigabit networking. We’re now seeing general availability of 400Gb with 800Gb firmly on the near-term roadmaps as computation within SFPs and switches increases.

In this presentation, Arista’s Robert Welch and Andy Bechtolsheim, explain how the 400GbE interfaces are made up, give insight into 800GbE and talks about deployment possibilities for 400GbE both now and in the near future harnessing in-built multiplexing. It’s important to realise that high capacity links we’re used to today of 100GbE or above are delivered by combining multiple lower-bandwidth ethernet links, known as lanes. 4x25GbE gives a 100GbE interface and 8x50GbE lanes provides 400GbE. The route to 800GbE is, then to increase the number of lanes or bump the speed of the lanes. The latter is the chosen route with 8x100GbE in the works for 2022/2023.

One downside of using lanes is that you will often need to break these out into individual fibres which is inconvenient and damages cost savings. Robert outlines the work being done to bring wavelength multiplexing (DWDM) into SFPs so that multiple wavelengths down one fibre are used rather than multiple fibres. This allows a single fibre pair to be used, much simplifying cabling and maintaining compatibility with the existing infrastructure. DWDM is very powerful as it can deliver 800GB over distances of over 5000km or 1.6TB for 1000km, It also allows you to have full-bandwidth interconnects between switches. Long haul SFPs with DWDM built in are called OSFP-LS transceivers.

Cost per bit is the religion at play here with the hyperscalers keenly buying into the 400Gb technology because this is only twice-, not four-, times the price of the 100Gb technology it’s replacing. The same is true of 800Gb. The new interfaces will run the ASICs faster and so will need to dissipate more heat. This has led to two longer form factors, the OSFP and QSFP-DD. The OSFP is a little larger than the QSFP but an adaptor can be used to maintain QSFP-form factor compatibility.

Andy explains that 800Gb Ethernet has been finished by the Ethernet Technology Alliance and is going into 51,2t silicon which will allow channels of native 800Gb capacity. This is somewhat in the future, though and Andy says that in the way 25G has worked well for us the last 5 years, 100gig is where the focus is for the next 5. Andy goes on to look at what future 800G chassis might loo like saying that in 2U you would expect 64 800G OSFP interfaces which could provide 128 400G outputs or 512 100G outputs with no co-packaged optics required.

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Speakers

	Robert Welch Technical Solutions Lead, Arista
	Andy Bechtolsheim Chairman, Chief Development Officer and Co-Founder, Arista Networks

Video: ST 2110 The Future of Live Remote Production

Posted on 29th March 2021 by Russell Trafford-Jones

Trying to apply the SMPTE ST 2110 hype to the reality of your equipment? This video is here to help. There are many ‘benefits’ of IP which are banded about yet it’s almost impossible to realise them all in one company. For the early adopters, there’s usually one benefit that has been the deal-breaker with other benefits helping boost confidence. Smaller broadcast companies, however, can struggle to get the scale needed for cost savings, don’t require as much flexibility and can’t justify the scalability. But as switches get cheaper and ST 2110 support continues to mature, it’s clear that we’re beyond the early adopter phase.

This panel gives context to ST 2110 and advises on ways to ‘get started’ and skill up. Moderated by Ken Kerschbaumer from the Sports Video Group, Leader’s Steve Holmes, Prinyar Boon from Phabrix join the panel with Arista colleagues Gerard Phillips and Robert Welch and Bridge Technologies’ Chairman Simen Frostad.

The panel quickly starts giving advice. Under the mantra ‘no packet left behind’, Gerard explains that, to him, COTS (Commercial Off The Shelf) means a move to enterprise-grade switches ‘if you want to sleep at night’. Compared to SDI, the move to IT can bring cost savings but don’t skimp on your switch infrastructure if you want a good quality product. Simen was pleased to welcome 2110 as he appreciated the almost instant transmission that analogue gave. The move to digital added a lot of latency, even in the SDI portions of the chain thanks to frame syncs. ST 2110, he says, allows us to get back, most of the way, to no-latency production. He’s also pleased to bid good-bye to embedded data.

It is possible to start small, is the reassuring message next from the panel. The trick here is to start with an island of 2110 and do your learning there. Prinyar lifts up a tote bag saying he has a 2110 system he can fit in there which takes just 10 minutes to get up and running. With two switches, a couple of PTP grandmasters and some 2110 sources, you have what you need to start a small system. There is free software that can help you learn about it, Easy NMOS is a quick-to-deploy NMOS repository that will give you the basics to get your system up and running. You can test NMOS APIs for free with AMWA’s testing tool. The EBU’s LIST project is a suite of software tools that help to inspect, measure and visualize the state of IP-based networks and the high-bitrate media traffic they carry and there’s is also SDPoker which lets you test ST 2110 SDP files. So whilst there are some upfront costs, to get the learning, experience and understanding you need to make decisions on your ST 2110 trajectory, it’s cost-effective and can form part of your staging/test system should you decide to proceed with a project.

The key here is to find your island project. For larger broadcasters or OB companies, a great island is to build an IP OB truck. IP has some big benefits for OB Trucks as we heard in this webinar, such as weight reduction, integration with remote production workflows and scalability to ‘any size’ of event. Few other ‘islands’ are able to benefit in so many ways, but a new self-op studio or small control room may be just the project for learning how to design, install, troubleshoot and maintain a 2110 system. Prinyar cautions that 2110 shouldn’t be just about moving an SDI workflow into IP. The justification should be about improving workflows.

Remote control is big motivator for the move to ST 2110. Far before the pandemic, Discovery chose 2110 for their Eurosport production infrastructure allowing them to centralise into two European locations all equipment controlled in production centres in countries around Europe. During the pandemic, we’ve seen the ability to create new connections without having to physically install new SDI is incredibly useful. Off the back of remote control of resources, some companies are finding they are able to use operators from locations where the hourly rate is low.

Before a Q&A, the panel addresses training. From one quarter we hear that ensuring your home networking knowledge is sound (DHCP, basic IP address details) is a great start and that you can get across the knowledge needed very little time. Prinyar says that he took advantage of a SMPTE Virtual Classroom course teaching the CCNA, whilst Robert from Arista says that there’s a lot in the CCNA that’s not very relevant. The Q&A covers 2110 over WAN, security, hardware life cycles and the reducing carbon footprint of production.

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Speakers

	Steve Holmes Applications Engineer, Leader
	Prinyar Boon Product Manager, PHABRIX
	Gerard Phillips Systems Engineer, Arista
	Simen Frostad Chairman, Bridge Technologies
	Robert Welch Technical Solutions Lead, Arista
	Moderator: Ken Kerschbaumer Chair & Editorial Directo, Sports Video Group

Video: Proper Network Designs and Considerations for SMPTE ST-2110

Posted on 14th December 2020 by Russell Trafford-Jones

Networks from SMPTE ST 2110 systems can be fairly simple, but the simplicity achieved hides a whole heap of careful considerations. By asking the right questions at the outset, a flexible, scalable network can be built with relative ease.

“No two networks are the same” cautions Robert Welch from Arista as he introduces the questions he asks at the beginning of the designs for a network to carry professional media such as uncompressed audio and video. His thinking focusses on the network interfaces (NICs) of the devices: How many are there? Which receive PTP? Which are for management and how do you want out-of-band/ILO access managed? All of these answers then feed into the workflows that are needed influencing how the rest of the network is created. The philosophy is to work backwards from the end-nodes that receive the network traffic.

Robert then shows how these answers influence the different networks at play. For resilience, it’s common to have two separate networks at work sending the same media to each end node. Each node then uses ST 2022-7 to find the packets it needs from both networks. This isn’t always possible as there are some devices which only have one interface or simply don’t have -7 support. Sometimes equipment has two management interfaces, so that can feed into the network design.

PTP is an essential service for professional media networks, so Robert discusses some aspects of implementation. When you have two networks delivering the same media simultaneously, they will both need PTP. For resilience, a network should operate with at least two Grand Masters – and usually, two is the best number. Ideally, your two media networks will have no connection between them except for PTP whereby the amber network can benefit from the PTP from the blue network’s grandmaster. Robert explains how to make this link a pure PTP-only link, stopping it from leaking other information between networks.

Multicast is a vital technology for 2110 media production, so Robert looks at its incarnation at both layer 2 and layer 3. With layer 2, multicast is handled using multicast MAC addresses. It works well with snooping and a querier except when it comes to scaling up to a large network or when using a number of switches. Robert explains that this because all multicast traffic needs to be sent through the rendez-vous point. If you would like more detail on this, check out Arista’s Gerard Phillips’ talk on network architecture.

Looking at JT-NM TR-1001, the guidelines outlining the best practices for deploying 2110 and associated technologies, Robert explains that multicast routing at layer 3 works much increases stability, enables resiliency and scalability. He also takes a close look at the difference between ‘all source’ multicasting supported by IGMP version 2 and the ability to filter for only specific sources using IGMP version 3.

Finishing off, Robert talks about the difficulties in scaling PTP since all the replies/requests go into the same multicast group which means that as the network scales, so does the traffic on that multicast group. This can be a problem for lower-end gear which needs to process and reject a lot of traffic.

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Speaker

Robert Welch
Technical Solutions Lead
Arista Networks

Video: Keeping Time with PTP

Posted on 4th November 2020 by Russell Trafford-Jones

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.

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Speakers