Video: Monolithic and Spine-Leaf Architectures

Posted on by Russell Trafford-Jones

It’s hard to talk about SMPTE 2110 system design without hearing the term ‘spine and leaf’. It’s a fundamental decision that needs to be made early on in the project; how many switches will you use and how will they be interconnected? Deciding is not without accepting compromises, so what needs to be considered?

Chris Lapp from Diversified shares his experience in designing such systems. Monolithic design has a single switch at the centre of the network with everything connected directly to it. For redundancy, this is normally complemented by a separate, identical switch providing a second network. For networks which are likely to need to scale, monolithic designs can add a hurdle to expansion once they get full. Also, if there are many ‘low bandwidth’ devices, it may not be cost-effective to attach them. For instance, if your central switch has many 40Gbps ports, it’s a waste to use many to connect to 1Gbps devices such as audio endpoints.

The answer to these problems is spine and leaf. Chris explains that this is more resilient to failure and allows easy scaling whilst retaining a non-blocking network. These improvements come at a price, naturally. Firstly, it does cost more and secondly, there is. added complexity. In a large facility with endpoints spread out, spine and leaf may be the only sensible option. However, Chris explores a cheaper version of spine and leaf often called ‘hub and spoke’ or ‘hybrid’.

If you are interested in this topic, listen to last week’s video from Arista’s Gerard Philips which talked in more detail about network design covering the pros and cons of spine and leaf, control using IGMP and SDN, PTP design amongst other topics. Read more here.

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Speakers

Chris Lapp Chris Lapp
Project Engineer, SME Routing
Diversified
Wes Simpson Wes Simpson
President, Telcom Product Consulting
Owner, LearnIPVideo.com

Video: CDN Trends in FPGAs & GPUs

Posted on by Russell Trafford-Jones

As technology continues to improve, immersive experiences are all the more feasible. This video looks at how the CDNs can play their part in enabling technologies which seem to rely on fast, local, compute. However, as with many internet services, low latency is very important.

Greg Jones from Nvidia and Nehal Mehta form Intel give us the lowdown in this video on what’s happening today to enable low-latency CDNs and what the future might look like. Intel, owners of FPGA makers Altera, and Nvidia are both interested in how their products can be of as much service at the edge as in the core datacentres.

Greg is involved in XR development at Nvidia. ‘XR’ is a term which refers to an outcome rather than any specific technology. Ostensibly ‘eXtended’ reality, it includes some VR, some augmented reality and anything else which helps improve the immersive experience. Greg explains that the importance of getting the ‘motion to photon’ delay to within 20ms. CDNs can play a role in this by moving compute to the edge. This tracks with current trends on wanting to reduce backhaul, edge computation is already on the rise.

Greg also touches on recent power improvements on newer GPUs. Similar to what we heard the other day from Gerard Phillips from Arista who said that switch manufacturers were still using technology that CPU’s were on several years ago meaning there’s plenty in the bank for speed increases over the coming years. According to Greg, the same is true for GPUs. Moreover, it’s important to compare compute per watt rather than doing it in absolute terms.

Nehal Mehta explains that, in the same way that GPUs can offload certain tasks from the CPU, so do FPGAs. At scale, this can be critical for tasks like deep packet inspection, encryption or even dynamic ad insertion at the edge,

The second half of video looks at what’s happening during the pandemic. Nehal explains that need for encryption has increased and Greg sees that large engineering functions are now, or many are soon likely to be, done in the cloud. Greg sees XR as going a long way to helping people collaborate around a large digital model and may help to reduce travel.

The last point made is regarding video conferencing all day long leaving people wanting “more meaningful interactions”. We are seeing attempts at richer and richer meeting experiences, both with and without XR.
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Speakers

Greg Jones Greg Jones
Global Business Development, XR
NVIDIA
Nehal Mehta Nehal Mehta
Direcotr Visiual Cloud, CDN Segment,
Intel
Tim Siglin Moderator: Tim Siglin
Founding Executive Director,
Help Me Stream

Video: Doing Better Congestion Control with BBR & Copa

Posted on by Russell Trafford-Jones

In networking there are many possible bottlenecks, but the most pervasive is congestion caused by links operating at capacity and saturating the buffers. Full buffers are unable to fully adapt to the incoming traffic, increasing the chances of dropped packets, but the extra latency added by full buffer after full buffer quickly adds up and this extra latency further degrades the quality of the connection for the data that does make it through.

It’s no surprise then, that a lot of work goes into finding the best ‘congestion’ algorithms to allow data senders to back off when a link stops responding well. This talk, from Facebook engineer Nitin Garg, examines old and new approaches to keeping streams fast and responsive by running a 4-million-data-point test of three contenders, Cubic, BBR and Copa.


Nitin starts by introducing what we mean by ‘congestion’, how and why it occurs. The simple example is that your computer can send data, typically, at up to 1Gbps, yet your uplink to the internet is likely below this number. So congestion control is a feedback mechanism which lets your computer realise that sending at 1Gbps isn’t working and allows it to throttle back to a speed which fits within your upload bandwidth. The same is true further down the pipe. If you have 50Mbps uplink to the internet, but you are sending to a server which only has 10Mbps left, not only does your computer need to throttle below 50, but also 10Mbps.

We then walk through how Cubic, BBR and Copa work with Nitin explaining the differences. <a href=”https://web.mit.edu/copa/” rel=”noopener” target=”_blank>Copa is the newest of the protocols comes from MIT and comes with the unique ability to tune it to your need; throughput or low latency. As discussed above, to keep latency down, buffer size needs to be minimised which stops you being aggressive in loading up links which leads to latency and throughput being at opposite ends of a see-saw.

Nitin’s test was on mobile phones using Facebook’s Live streaming app on Android and iOS for live streaming with ABR where the app itself adapts to ensure that it is streaming with as high a quality as possible, but willing to reduce the bitrate when needed. Testing from global markets, they measured round trip times and the amount of delivered data. Nitin walks through the results both for latency and throughput and shows that when Copa is optimised for latency, in the worst conditions it leads the other two protocols in latency reduction.

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Speakers

Nitin Garg Nitin Garg
Software Engineer, Videos Infra,
Facebook

Video: 5 Myths About Dolby Vision & HDR debunked

Posted on by Russell Trafford-Jones

There seem no let up in the number of technologies coming to market and whilst some, like HDR, have been slowly advancing on us for many years, the technologies that enable them such as Dolby Vision, HDR10+ and the metadata handling technologies further upstream are more recent. So it’s no surprise that there is some confusion over what’s possible and what’s not.

In this video, Bitmovin and Dolby the truth behind 5 myths surrounding the implementation and financial impact of Dolby Vision and HDR in general. Bitmovin sets the scene by with Sean McCarthy giving an overview on their research into the market. He explains why quality remains important, simply put to either keep up with competitors or be a differentiator. Sean then gives an overview of the ‘better pixels’ principle underlining that improving the pixels themselves is often more effective than higher resolution, technologies such as wide colour gamut (WCG) and HDR.

David Brooks then explains why HDR looks better, explaining the biology and psychology behind the effect as well as the technology itself. The trick with HDR is that there are no extra brightness values for the pixels, rather the brightness of each pixel is mapped onto a larger range. It’s this mapping which is the strength of the technology, altering the mapping gives different results, ultimately allowing you to run SDR and HDR workflows in parallel. David explains how HDR can be mapped down to low-brightness displays,

The last half of this video is dedicated to the myths. Each myth has several slides of explanation, for instance, the one suggests that the workflows are very complex. Hangen Last walks through a number of scenarios showing how dual (or even three-way) workflows can be achieved. The other myths, and the questions at the end, talk about resolution, licensing cost, metadata, managing dual SDR/HDR assets and live workflows with Dolby Vision.

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Speakers

David Brooks David Brooks
Senior Director, Professional Solutions,
Dolby Laboratories
Hagan Last Hagan Last
Technology Manager, Content Distribution,
Dolby Laboratories
Sean McCarthy Sean McCarthy
Senior Technical Product Marketing Manager,
Bitmovin
Kieran Farr Moderator: Kieran Farr
VP Marketing,
Bitmovin