Search Results for: 2022-7

Video: AES67 over WAN

Posted on by Russell Trafford-Jones

Deeply embedded in the audio industry and adopted into SMPTE ST 2110, AES67 workflows surround us. Increasingly our workflows are in multiple locations so moving AES67 on the WAN and the internet is essential. If networks were always perfect, this would be easy but as that’s not the case, this RAVENNA talk examines what the problems are and how to solve them.

Andreas Hildebrand introduces the video with an examination of how the WAN, whether that’s a company’s managed wide area network or the internet at large, is different from a LAN. Typical issues are packet loss, varying latency meaning the packets arrive with jitter, lack of PTP and multicast. With this in mind, Nicolas Sturmel from Merging Technologies takes the reins to examine the solutions.

Nicolas explains the typically EBU Tech 3326 (also known as ACIP) is used for WAN contribution which specifies how a sender and receiver communicate and the codecs to be used. Although PCM is available, many codecs such as AptX are also prescribed for use. Nicolas says that ACIP is great for most applications but if you need low-latency, precise timing and PCM-quality staying AES67 may be the best policy, even over the WAN.

Having identified your AES6-over-WAN workflow, the question is how to pull it off. Nicolas looks at three methods, one is FEC whereby you are constantly sending redundant data. FEC can send up to around 25% extra data so that if any is lost, the extra information sent can be leveraged to determine the lost values and reconstruct the stream. This is can work well but requires sending this extra data constantly therefore putting up your bandwidth. It can also only deal with certain losses requiring them to be of a short duration.

Instead of FEC, you can use RIST, SRT or a similar re-transmission technology. These will actively recover any lost packets and have the benefit that you only transmit more data when you have lost data. Lastly, he mentions SMPTE ST 2022-7 which uses two paths of identical data to cover losses in any one of them. Although this is 100% extra data, the benefit is that it can deal with any type of loss including a complete path failure which neither of the others can do. It is, however possible to combine FEC or RIST with a 2022-7 workflow so you can have two levels of protection.

Timing over the WAN is not ideal as PTP loses accuracy over long-latency links and it assumes symmetry. On the internet, it’s possible to get links where the latency is longer in one direction than the other. An easy, though potentially costly, workaround for distributing PTP over the WAN is to use GPS, GLONASS or similar to synchronise grandmaster clocks at each location.

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Speakers

Nicolas Sturmel Nicolas Sturmel
Product Manager & Senior Technologist
Merging Technologies
Andreas Hildebrand Andreas Hildebrand
RAVENNA Evangelist,
ALCNetworx

Video: IP Media Networks for Live Production

Posted on by Russell Trafford-Jones

Building and controlling a network for SMPTE ST 2110 go hand in hand when it comes to planning an installation. As ST 2110 delivers all media essences separately, networks can easily end up carrying tens of thousands of flows emphasising the need for efficient network design and having a full understanding of the paths your media are using.

This video is co-presented by Nevion and Arista and starts by observing that the traditional difference between a LAN and WAN is being eroded leading as WANs get faster and better, we find that we can now deliver multi-location broadcast facilities which act similarly to if everything was co-located. Moreover, introduces Martin Walbum Media Function virtualisation which is enabled by network-connected equipment allowing for shared processing and shared control. For instance, it’s now possible to house all equipment in a datacentre and allow this to be used remotely maximising the utilisation of the equipment allowing a broadcaster to maximise the value of its purchases and minimise costs.

Arista’s Gerard Phillips takes a look at SDI systems to understand how we expect IP systems to behave and what we expect them to do. The system needs to deliver high throughput, instantaneous switching with low latency and no tolerance for failure. In order to do this, not only do we need to get the right software but to deliver the resilience we need, the network needs the correct architecture. Gerard takes us through the different options starting with a typical, flat, layer 2 networks and working up to leaf and spine along with a treatment of red, blue and purple networks.

Gerard recently did a deep dive on network design for live production for the IET. Take a look for much more detail on how to architect a network for uncompressed media.

Martin then looks at the need for orchestration. Broadcasters expect to deliver systems with, preferably, no downtime. As such, we’ve seen that network elements are typically duplicated as is the traffic which is delivered over two paths and SMPTE ST 2022-7. If you want to take something out of use for planned maintenance, it’s best to do that in a planned, ordered, way meaning you migrate flows away from it until it’s no longer in-circuit. Software-Defined Networks (SDNs), do exactly that. Martin walks us through the pros and cons of managing your network with IGMP and SDN. Gerard’s previous talk also looks at this in detail.

The video finishes with a look at which Arista switches can be used for media and a look at how Arista and Nevion implemented an ST 2110 network at Swiss broadcaster, tpc. This case study is presented in longer form in this video from the IP Showcase.

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Speakers

Gerard Phillips Gerard Phillips
Systems Engineer,
Arista
Martin Walbum Martin Walbum
Senior Vice President of Solution Strategy,
Nevion

Video: Progress Update for the ST 2110 WAN VSF Activity Group

Posted on by Russell Trafford-Jones

2110 Over WAN Update

Is SMPTE ST 2110 suitable for inter-site connectivity over the WAN? ST 2110 is moving past the early adopter phase with more and more installations and OB vans bringing 2110 into daily use but today, each site works independently. What if we could maintain a 2110 environment between sites. There are a number of challenges still to be overcome and moving a large number of essence flows long distances and between PTP time domains is one of them.

Nevion’s Andy Rayner is chair of the VSF Activity Group looking into transporting SMPTE ST 2110 over WAN and is here to give an update on the work in progress which started 18 months ago. The presentation looks at how to move media between locations which has been the primary focus to date. It then discusses how control over which media are shared will be handled as this is a new aspect to the work. Andy starts by outlining the protection offered in the scheme which supports both 2022-7 and FEC then explains that though FEC is valuable for single links where 2022-7 isn’t viable, only some of the possible ST 2022-5 FEC configurations are supported, in part, to keep latency low.

The headline to carrying 2110 over the WAN is that it will be done over a trunk. GRE is a widely used Cisco trunking technology. Trunking, also known as tunnelling, is a technique of carrying ‘private’ traffic over a network such that a device sending into the trunk doesn’t see any of the infrastructures between the entrance and the exit. It allows, for instance, IPv6 traffic to be carried over IPv4 equipment where the v4 equipment has no idea about the v6 data since it’s been wrapped in a v4 envelope. Similarly, the ipv6 equipment has no idea that the ipv6 data is being wrapped and carried by routers which don’t understand ipv6 since the wrapping and unwrapping of the data is done transparently at the handoff.

In the context of SMPTE ST 2110, a trunk allows one port to be used to create a single connection to the destination, yet carry many individual media streams within. This has the big benefit of simplifying the inter-site connectivity at the IT level, but importantly also means that the single connection is quite high bandwidth. When FEC is applied to a connection, the latency introduced increases as the bit rate reduces. Since ST 2110 carries audio and metadata separately, an FEC-protected stream would have variable latency depending on the type of the of traffic. Bundling them in to one large data stream allows FEC to be applied once and all traffic then suffers the same latency increase. The third reason is to ensure all essences take the same network path. If each connection was separate, it would be possible for some to be routed on a physically different route and therefore be subject to a different latency.

Entering the last part of the talk, Andy switches gears to talk about how site A can control streams in site B. The answer is that it doesn’t ‘control’, rather there is the concept of requesting streams. Site A will declare what is available and site B can state what it would like to connect to and when. In response, site A can accept and promise to have those sources available to the WAN interface at the right time. When the time is right, they are released over the WAN. This protects the WAN connectivity from being filled with media which isn’t actually being used. These exchanges are mediated and carried out with NMOS IS-04 an IS-05.

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Speakers

Andy Rayner Andy Rayner
Chief Technologist, Nevion,
Chair, WAN IP Activity Group, VSF
Wes Simpson Moderator: Wes Simpson
Founder, LearnIPVideo.com
Co-chair RIST Activity Group, VSF

Video: Network Design for Live Production

Posted on by Russell Trafford-Jones

The benefits of IP sound great, but many are held back with real-life concerns: Can we afford it? Can we plug the training gap? and how do we even do it? This video looks at the latter; how do you deploy a network good enough for uncompressed video, audio and metadata? The network needs to deal with a large number of flows, many of which are high bandwidth. If you’re putting it to air, you need reliability and redundancy. You need to distribute PTP timing, control and maintain it.

Gerard Philips from Arista talks to IET Media about the choices you need to make when designing your network. Gerard starts by reminding us of the benefits of moving to IP, the most tangible of which is the switching density possible. SDI routers can use a whole rack to switch over one thousand sources, but with IP Gerard says you can achieve a 4000-square router within just 7U. With increasingly complicated workflows and with the increasing scale of some broadcasters, this density is a major motivating factor in the move. Doubling down on the density message, Gerard then looks at the difference in connectivity available comparing SDI cables which have signal per cable, to 400Gb links which can carry 65 UHD signals per link.

Audio is always ahead of video when it comes to IP transitions so there are many established audio-over-IP protocols, many of which work at Layer 2 over the network stack. Using Layer 2 has great benefits because there is no routing which means that discovering everything on the network is as simple as broadcasting a question and waiting for answers. Discovery is very simple and is one reason for the ‘plug and play’ ease of NDI, being a layer 2 protocol, it can use mDNS or similar to query the network and display sources and destinations available within seconds. Layer 3-based protocols don’t have this luxury as some resources can be on a separate network which won’t receive a discovery request that’s simply broadcast on the local network.

Gerard examines the benefits of layer 2 and explains how IGMP multicast works detailing the need for an IGMP querier to be in one location and receiving all the traffic. This is a limiting factor in scaling a network, particularly with high-bandwidth flows. Layer 3, we hear, is the solution to this scaling problem bringing with it more control of the size of ‘failure domains’ – how much of your network breaks if there’s a problem.

The next section of the video gets down to the meat of network design and explains the 3 main types of architecture: Monolithic, Hub and spoke and leaf and spoke. Gerard takes time to discuss the validity of all these architectures before discussing coloured networks. Two identical networks dubbed ‘Red’ and ‘Blue’ are often used to provide redundancy in SMPTE ST 2110, and similar uncompressed, networks with the idea that the source generates two identical streams and feeds them over these two identical networks. The receiver receives both streams and uses SMPTE ST 2022-7 to seamlessly deal with packet loss. Gerard then introduces ‘purple’ networks, ones where all switch infrastructure is in the same network and the network orchestrator ensures that each of the two essence flows from the source takes a separate route through the infrastructure. This means that for each flow there is a ‘red’ and a ‘blue’ route, but overall each switch is carrying a mixture of ‘red’ and ‘blue’ traffic.

The beauty of using IGMP/PIM for managing traffic over your networks is that the network itself decides how the flows move over the infrastructure. This makes for a low-footprint, simple installation. However, without the ability to take into account individual link capacity, the capacity of the network in general, bitrate of individual flows and understanding the overall topology, there is very control over where your traffic is which makes maintenance and fault-finding hard and, more generally, what’s the right decision for one small part of the network is not necessarily the right decision for the flow or for the network as a whole. Gerard explains how Software-Defined Networking (SDN) address this and give absolute control over the path your flows take.

Lastly, Gerard looks at PTP, the Precision Time Protocol. 2110 relies on having the PTP in the flow, in the essence allowing flows of separate audio and video to have good lip-sync and to avoid phase errors when audio is mixed together (where PTP has been used for some time). We see different architectures which include two grandmaster clocks (GMs), discuss whether boundary clocks (BCs) or transparent clocks (TCs) are the way to go and examine the little security that is available to stop rogue end-points taking charge and becoming grandmaster themselves.

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Speaker

Gerard Phillips Gerard Phillips
Systems Engineer,
Arista