Why RIST?

Why RIST? 

By Wes Simpson, Owner, LearnIPVideo.com

Abstract: This white paper describes the technical and operational benefits of RIST for end users and technology providers who are considering using it for their high-reliability, high-performance media transport applications. 

RIST stands for “Reliable Internet Stream Transport,” and that is exactly what it accomplishes – moving high-quality video and audio signals across public IP networks while preventing packet loss and other signal degradations. While there have been a number of companies that have developed their own, proprietary protocols, RIST is the first to offer a completely open specification, allowing anyone to download the necessary documents and develop a compliant solution.  In addition, open-source code libraries are available on a number of platforms, making implementation even easier for end-users and developers alike.

History and Progress

Even though it is one of the most recently developed protocols for high-quality video transport over uncontrolled networks, RIST has made significant progress.  RIST was developed by an Activity Group (AG) within the VSF (Video Services Forum) as a way to promote interoperability between vendors. This group has been active since 2017. To date, the RIST AG has produced two specifications; RIST Simple Profile and RIST Main Profile. Simple Profile devices support ARQ and bonding/load sharing. Main Profile devices add encryption, authentication and tunneling, and are backwards-compatible with Simple Profile devices. An Advanced Profile specification is targeted for release in 2021.

 The AG is open to all the members of the VSF, and work continues to define new features and enhancements that expand the capabilities of RIST for new applications. Any new version of the RIST specification that results from this work will be published on the VSF website and freely downloadable by anyone.

In 2018, the RIST Forum was formed as a separate organization to help educate the media industry about RIST technology and to act as a clearinghouse for industry news and technical information.

Key RIST Functions

ARQ, or Automatic Repeat reQuest, is used by RIST to compensate for missing packets within a received stream. When packet losses are detected, receivers can send messages to senders to request that the missing packets be re-transmitted to the receiver.  Once the re-sent packets are delivered, the receiver can put them into the proper sequence, thereby allowing the media content to be correctly decoded without gaps or errors.

Tunneling is the process of combining multiple packet flows into a single network connection. Doing this improves manageability of the resulting signal by simplifying firewall configuration (a single port as compared to multiple ports). Tunneling also permits non-native protocols to be transported over a foreign backbone network. For example, multicast LAN packets can be sent over a unicast WAN network, or IPv6 packets over an IPv4 network.  Another useful feature is support for transporting any generic data inside the tunnel, allowing applications such as in-band control.

Encryption provides protection against unauthorized access to the content of media packets. Authentication is also supported - endpoints can authorize each other, preventing streams from being sent from fraudulent sources or delivered to unintended destinations.

All RIST receivers intrinsically support network bonding, load sharing and redundant paths using packet replication. These features allow RIST senders to deliver packets very flexibly over virtually any available IP network connection.  Bonding (also known as inverse multiplexing) allows a high-speed packet stream to be distributed across multiple lower-speed connections and then reassembled at the destination. Load sharing allows packets to be sent over multiple network connections so that, in the event that one of the connections fails, the other connections can be used to carry the packet load without interruption. With packet replication, sending devices can make multiple copies of outbound packets that are delivered over multiple links, allowing lost packets on one link to be losslessly replaced by packets from another link, in the manner of SMPTE ST 2022-7.

RIST Benefits

RIST has already been adopted by a significant number of technology providers and end users. Here are some of the many benefits of making this choice.

Interoperability – RIST is all about allowing multiple technology providers to be able to send and receive streams between compatible devices. This fixes the problem of vendor “lock-in” that has been prevalent for many years in the market for high-quality media transport devices, including many of the so-called “cellular bonding” systems that are widely used for news-gathering and other live events.

The RIST AG has supported several rounds of successful interoperability testing, with the most recent round in early 2020.  To date, the following companies have participated in one or more interop tests:  Artel, Cobalt Digital, DVEO, Evertz, Net Insight, Nevion, Qvidium, SipRadius, Videoflow and Zixi, and the most recent tests have also included compiled versions of the libRIST open-source library code.

The original Simple Profile of RIST was built to be compatible with existing SMPTE ST 2022-2 senders and receivers (also known as ProMPEG CoP3), which have seen widespread deployment over the past decade. In fact, an ST 2022-2 receiver can receive a stream directly from a RIST sender without needing to send any packet correction messages or other special configuration.  

Security – Media connections over a public network require encryption to protect valuable content from unauthorized access.  RIST Main Profile supports two different types of encryption: DTLS (Datagram Transport Layer Security) and PSK (Pre-Shared Key).

 DTLS uses handshake-based key exchange to encrypt UDP packet streams using traceable certificates. It is very similar to TLS that is widely used today for secure Internet browsing and HTTPS. DTLS works on a unicast, bi-directional network, where one sender communicates with one receiver.  An added benefit of DTLS is authorization, which allows the sending and receiving devices to confirm the identity of each other, preventing connections to unauthorized endpoints.

PSK encryption and decryption is based on secret passphrase that is known only to the sender and receiver, which is similar to the secret user passwords used by many websites. PSK allows one sender to generate a single stream that can be simultaneously decrypted by multiple receivers, supporting the widely used “one-to-many” or multicast configuration of many media networks. PSK encryption will also work on one-way networks, such as satellite and terrestrial broadcasting systems.

Flexibility – Like widely used standards such as MPEG, the RIST specification defines only the interface between RIST senders and receivers. This opens up the protocol for significant innovation, allowing technology providers the freedom to innovate as they develop RIST-compliant senders and receivers. Various aspects of a RIST implementation can be fine-tuned to meet specific applications, in areas including retransmission algorithms, buffer management, encryption key management and others. This flexibility has already been demonstrated by the wide array of products that have been released using RIST, ranging from mobile phone software to cloud-based services, plus hardware endpoints and gateways across a spectrum of speeds and capabilities.

The forthcoming RIST Advanced Profile will support a tunnel architecture that extends ARQ protection to the combined traffic.  This allows all sorts of control and data applications, including ones based on TCP, to be delivered and protected by RIST technology.

Innovation – Because RIST is built on industry standards from IETF, SMPTE and other organizations, the process of building new products is greatly simplified.  Existing products that use these common standards can be enhanced easily to offer RIST as an add-on or in place of other protocols. This helps explain the rapid spread of RIST technology into new application spaces, and as an upgrade to existing products.

The RIST specification is also being expanded to include new features to support more applications. In particular, the Advanced Profile currently being developed in the RIST AG is intended to include support for mixed satellite/terrestrial networks, support for VPNs, and improved firewall traversal.  This new specification is expected to be released in 2021.

Performance – Testing has demonstrated the ability of RIST connections to deliver error-free streams across network connections with greater than fifty percent packet loss, far exceeding the loss recovery capabilities of other widely-used protocols. RIST connections can also be tuned to have extremely low end-to-end latency relative to the network RTT (Round Trip Time) through the use of minimal buffers.

RIST was also built with speed in mind.  As Ultra HD/4K deployments increase, and as 8K technology comes to market, RIST applications can easily be scaled up to support the higher bandwidths required. And, because RIST is compatible with industry-standard FEC (Forward Error Correction), uncompressed content can also be delivered using RIST in many applications. 

Mobility – Media producers and consumers are increasingly using mobile devices for creating and viewing content. Wireless connectivity can cause packet loss and signal dropouts. To improve performance, RIST technology can be used, which is why Larix Broadcaster and Larix Player for iOS and Android are some of the most recent additions to the growing family of RIST-enabled products.

Cloud-based media processing also enables remote broadcasting and enhances mobility by providing signal ingest and distribution via cloud portals located around the globe. RIST software is easy to deploy in private or leased cloud instances, and is natively supported in the public cloud by Amazon/AWS Elemental’s MediaConnect service. 

Openness – All of the RIST specifications are developed by a group of experts under the auspices of the Video Services Forum. The specifications documents are all available as free downloads from the VSF.tv website and are licensed under Creative Commons Attribution-NoDerivatives 4.0, allowing anyone to reference and use them.

RIST is supported by a number of open-source activities, including VLCv4, WireShark, and ffmpeg (currently underway). An open-source code library call libRIST is also available, and has been used to create a number of products currently on the market.

Conclusion

For a newly developed specification, RIST has certainly hit the ground running. Already, multiple companies are using RIST to release new products and add features and increase performance of their existing products, with the added benefit of interoperability between providers.   The flexibility and performance of RIST are unmatched by other transport protocols, and innovation continues to proceed rapidly.

Put together, these features make RIST the most open, most modern technology available in the market today. Choose RIST to avoid lock-in, participate in innovation, and deliver media signals across a wide range of network conditions. For more information about RIST technologies and compatible products, please visit www.RIST.tv