Video: RIST: Enabling Remote Work with Reliable Live Video Over Unmanaged Networks

Last week’s article on RIST, here on The Broadcast Knowledge, stirred up some interest about whether we view RIST as being against SRT & Zixi, or whether it’s an evolution thereof. Whilst the talk covered the use of RIST and the reasons one company chose to use it, this talk explains what RIST achieves in terms of features showing that it has a ‘simple’ and ‘main’ profile which bring different features to the table.

Rick Ackermans is the chair of the RIST Activity Group which is the group that develops the specifications. Rick explains some of the reasons motivating people to look at the internet and other unmanaged networks to move their video. The traditional circuit-based contribution and distribution infrastructure on which broadcasting relied has high fixed costs. Whilst this can be fully justifiable for transmitter links, though still expensive, for other ad-hoc circuits you are paying all the time for something which is only occasionally used, satellite space in the C-band is reducing squeezing people out. And, of course, remote working is much in the spotlight so technologies like RIST which don’t have a high latency (unlike HLS) are in demand.

RIST manages to solve many of the problems with using the internet such as protecting your content from theft and from packet loss. It’s a joint effort between many companies including Zixi and Haivision. The aim is to create choice in the market by removing vendor bias and control. Vendors are more likely to implement an open specification than one which has ties to another vendor so this should open up the market creating more demand for this type of solution.

In the next section, we see how RIST as a group is organised and who it fits in to the Video Services Forum, VSF. We then look at the profiles available in RIST. A full implementation aims at being a 3-layer onion with the ‘Simple Profile’ in the middle. This has basic network resilience and interoperability. On top of that, the ‘Main Profile’ is built which adds encryption, authentication and other features. The future sees an ‘Enhanced Profile’ which may bring with it channel management.

Rick then dives down into each of these profiles to uncover the details of what’s there and explain the publication status. The simple profile allows full RTP interoperability for use as a standard sender, but also adds packet recovery plus seamless switching. The Main profile introduces the use of GRE tunnels where a single connection is setup between two devices. Like a cable, multiple signals can then be sent down the cable together. From an IT perspective this makes life so much easier as the number of streams is totally transparent to the network so firewall configuration, for example, is made all the simpler. However it also means that by just running encryption on the tunnel, everything is encrypted with no further complexity. Encryption works better on higher bitrate streams so, again, running on the aggregate has a benefit than on each stream individually. Rick talks about the encryption modes with DTLS and Pre-shared Key being available as well as the all important, but often neglected, step of authenticating – ensuring you are sending to the endpoint you expected to be sending to.

The last part of the talk covers interoperability, including a comparison between RIST and SRT. Whilst there are many similarities, Rick claims RIST can cope with higher percentages of packet loss. He also says that 2022-7 doesn’t work with SRT, though The Broadcast Knowledge is aware of interoperable implementations which do allow 2022-7 to work even through SRT. The climax of this section is explaining the setup of the RIST NAB demo, a multi-vendor, international demo which proved the reliability claims. Rick finishes by examining some case studies and with a Q&A.

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Merrick Ackermans Rick Ackermans
MVA Broadcast Consulting
RIST Activity Group Chair

Video: RIST and Open Broadcast Systems

RIST is a streaming protocol which allows lossy networks such as the internet to be used for critical streaming applications. Called Reliable Internet Stream Transport, it uses ARQ (Adaptive Repeat reQuest) retransmission technology to request any data that is lost by the network, creating reliable paths for video contribution.

In this presentation Kieran Kunhya from Open Broadcast Systems explains why his company has chosen RIST protocol for their software-based encoders and decoders. Their initial solution for news, sports and linear channels contribution over public internet was based on FEC (Forward Error Correction), a technique used for controlling errors in transmission by sending data in a redundant way using error-correcting code. However, FEC couldn’t cope with large burst losses, there was limited interoperability and the implementation was complex. Protecting the stream by sending the same feed over multiple paths and/or sending a delayed version of the stream on the same path, had a heavy bandwidth penalty. This prompted them, instead, to implement an ARQ technique based on RFC 4585 (Extended RTP Profile for Real-time Transport Control Protocol-Based Feedback), which gave them functionality quite similar to the basic RIST functionality.

Key to the discussion, Kieran explains why they decided not to adopt the SRT protocol. As SRT is based file transfer protocol, it’s difficult or impossible to add features like bonding, multi-network and multi-point support which were available in RIST from day one. Moreover, RIST has a large IETF heritage from other industries and is vendor-independent. In Kieran’s opinion SRT will become a prosumer solution (similar to RTMP, now, for streaming) and RIST will be the professional solution (analogous to MPEG-2 Transport Streams).

Different applications for the RIST protocol are discussed, including 24/7 linear channels for satellite uplink from playout, interactive (two-way) talking heads for news, high bitrate live events and reverse vision lines for monitoring purposes. Also, there is a big potential for using RIST in cloud solutions for live broadcast production workflows. Kieran hopes that more broadcasters will start using spin-up and spin-down cloud workflows, which will help save space and money on infrastructure.

What’s interesting, Open Broadcast Solutions are not currently interested in RIST Main Profile (the main advantages of this profile are support for encryption, authentication and in-band data). Kieran explains that to control devices in remote locations you need some kind of off-the-shelf VPN anyway. These systems provide encryption and NAT port traversal, so the problem is solved at a different layer in the OSI model and this gives customers more control over the type of encryption they want.

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Kieran Kunhya Kieran Kunhya
Founder and CEO,
Open Broadcast Systems

Video: RIST in the Cloud

Cloud workflows are starting to become an integral part of broadcasters’ live production. However, the quality of video is often not sufficient for high-end broadcast applications where cloud infrastructure providers such as Google, Oracle or AWS are accessed through the public Internet or leased lines.

A number of protocols based on ARQ (Adaptive Repeat reQuest) retransmission technology have been created (including SRT, Zixi, VideoFlow and RIST) to solve the challenge of moving professional media over the Internet which is fraught with dropped packets and unwanted delays. Protocols such as a SRT and RIST enable broadcast-grade video delivery at a much lower cost than fibre or satellite links.

The RIST (Reliable Internet Streaming Transport) protocol has been created as an open alternative to commercial options such as Zixi. This protocol is a merging of technologies from around the industry built upon current standards in IETF RFCs, providing an open, interoperable and technically robust solution for low-latency live video over unmanaged networks.

In this presentation David Griggs from Amazon Web Services (AWS) talks about how the RIST protocol with cloud technology is transforming broadcast content distribution. He explains that delivery of live content is essential for the broadcasters and they look for a way to deliver this content without using expensive private fibre optics or satellite links. With unmanaged networks you can get content from one side of the world to the other with very little investment in time and infrastructure, but it is only possible with protocols based on ARQ like RIST.

Next, David discusses the major advantages of cloud technology, being dynamic and flexible. Historically dimensioning the entire production environment for peak utilisation was financially challenging. Now it is possible to dimension it for average use, while leveraging cloud resources for peak usage, providing a more elastic cost model. Moreover, the cloud is a good place to innovate and to experiment because the barrier to entry in terms of cost is low. It encourages both customers and vendors to experiment and to be innovative and ultimately build more compelling and better solutions.

David believes that open and interoperable QoS protocols like RIST will be instrumental in building complex distribution networks in the cloud. He hopes that AWS by working together with Net Insight, Zixi and Cobalt Digital can start to build innovative and interoperable cloud solutions for live sports.

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David Griggs
Senior Product Manager, Media Services
AWS Elemental

Video: RIST Pre-Shared Key Encryption

An important factor when sending production video feeds and other media over the internet for most people is encryption. When distributing to the end user, it’s different, but for contribution having the assurance that no-one else can view the video is very reassuring to all parties even when the content doesn’t necessitate it. RIST has been in development for a while and has grown beyond the simple profile which only dealt with packet loss. Now with the main profile, encryption is possible; there are actually two ways to encrypt. One uses DTLS which is the UDP-based equivalent of the same TLS encryption that https:// websites use, the other uses pre-shared keys (PSK).

Sergio Ammirata from DVEO starts the talk by introducing the main profile and the use of GRE tunnels. The use of a tunnel from sender to receiver allows for a single connection to carry multiple channels of multiplexed data. Importantly. it also allows the encryption to happen to the tunnel rather than to each media stream separately.

The next section of the talk revises what DTLS is: part of the main profile providing TLS encryption to UDP. Given this is an encryption method, it’s important to realise it is not part of the data-loss recovery algorithms. Since DTLS is based on TLS, it will also need certificates. Just like websites you have the choice of having a self-signed certificate or one signed by a trusted authority. This means that you not only know that you are sending encrypted data, you are also sending it to a trusted computer, not someone unintended. Sergio takes us through the workflow of verifying the certificates highlighting, for instance, the requirement for a realtime clock otherwise the start and expiry dates in the certificates wouldn’t have any meaning.

With PSK, there is no authentication. It encrypts the whole of the GRE tunnel except for headers with an AES key related to the pre-shared passphrase. The encryption is changed periodically by an automatic process. It’s important to realise that because this is so deterministic, this can be used for bonded connections. When Sergio then looks at the data flow for using PSK, we see that that it is much simpler with many fewer handshakes.

As to when PSK is the route to take over using DTLS, one-to-many transmission is an obvious candidate but also where there is only one-way communication such as most satellite links. Sergio finishes the talk by looking at the use of FEC and taking questions from the floor.

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Sergio Ammirata Sergio Ammirata