How Open Caching Aims To Support Broadcast Grade Streaming - Part 1

Open Caching, a specification created by the Streaming Video Alliance (SVA), promises Content Providers a standardized CDN (Content Delivery Network) model that delivers a better end-customer QoE (Quality of Experience), and a possible way for ISPs (Internet Service Providers) to gain new operational efficiencies and earn new revenues from the delivery of OTT services.

These promises are some of the most important issues to resolve for D2C streaming video services to reach full “broadcast-scale”, according to some industry observers and participants.

The grand vision for Open Caching is of an open and global CDN marketplace with CDN capacity provided directly inside ISP networks. Saying this another way, it is a way for ISPs and their CDN partners to serve Content Providers to achieve the same benefits from Edge Cache proximity to customers that Netflix, DAZN and other major streamers have already achieved for their own D2C streaming services through their own private CDNs.

The hype around Open Caching is growing as demand increases for broadcast-grade and broadcast-scale streaming. So, what is all the hype about? This 2-part article inspects the latest information about Open Caching and, with inputs from various industry leaders, looks at how it is expected to become a more important part of the Content Provider CDN ecosystem in future.

The Drivers Of Open Caching

The Open Caching initiative is founded on achieving three key objectives for video streaming:

1.  Multi-CDN And Interoperability
Content Providers have audiences that transcend individual CDNs and ISPs. Therefore, Content Providers naturally consider how to achieve the required combination of audience reach, service price, and service performance from their CDN suppliers. To achieve this, they have progressively migrated to a multi-CDN model. While multi-CDN brings certain benefits, like reach, price, and resiliency opportunities, it also brings extra complexity to a Content Provider because it involves managing multiple suppliers across a non-standardized set of interfaces. As streaming grows, the importance of standardization between CDNs also grows to simplify operations for the Content Provider, both in terms of supplier management but also in terms of daily operational activities such as managing content across multiple caching environments.

2.  Closeness To Consumers
Streaming video generally benefits from being delivered closer to the consumer. A CDN platform deployed inside an ISP network creates the closest possible point to a consumer for CDN deployment – imagine a location in a major city in any country. For people in or near that city this is typically the best place for a CDN Edge to serve a stream. In the future, as streaming quantities and peak throughputs grow, this location may need to be even more distributed – such as in smaller cities, where telephone exchanges host important broadband access network systems. This “deeper point” inside the ISP network is generally not where any CDN infrastructure is deployed today – we simply have not needed to do it yet, but things are set to change as D2C services grow.

For Content Providers, this closer-to-the-consumer positioning typically results in best possible quality and latency (i.e., best QoE - Quality of Experience), which are critical factors for the success of their services, particularly given the growing amount of live and linear content that is being streamed. For ISPs, a more deeply distributed Edge layer yields important benefits – it decongests their core network by shifting often many Tbps of throughput to deeper network locations, which means they can deliver higher quantities of streaming video while avoiding the expense of dramatically expanding their core network to handle it. This, in turn, leaves the core network capacity more available for all the other digital services that are growing at the same time as video streaming, such as IoT (Internet of Things), video conferencing, and security services.

It is important to note that “closeness” does not necessarily equal “better throughput”. Better throughput is really a function of “available capacity”. If capacity was unlimited, a stream could traverse an IP network to reach a consumer at its target bitrate without any problems. Capacity bottlenecks are what cause streaming performance issues. However, with that said, being closer to the consumer avoids the all-important network capacity bottleneck which is the ingress point into the ISP (i.e., the peering, transit, or interconnect points where today’s traditional CDN Edge interfaces to an ISP network), which is representative of the internal capacity available on the ISP’s core network.

3.  ISP Revenue Generation From OTT
Some ISPs offer pay-TV services, aggregating many content providers into a set of packages for consumers. Many ISPs do not offer pay-TV services. Existing pay-TV services are under pressure from D2C services that encourage “pay-TV cord-cutting”. At the same time, the level of video traffic delivered over ISP networks is increasing because of D2C video streaming, but the ISPs are not participating in the revenue generated from those services. In fact, in some countries, regulators are currently focused on creating a new industry balance by taxing the largest bandwidth users, like Netflix, to return some revenues from their above-average usage. But simply put, as “closer to the consumer” becomes more important for QoE and network decongestion reasons, demand for and support for CDN capacity inside ISP networks grows.

ISPs are therefore very well-positioned to support the Media industry to provide high-bandwidth, high-quality, low-latency video services to consumers. It’s a win-win-win for the consumer, ISP and D2C Streamer. And as well as enabling this best possible QoE, ISPs can potentially replace their pay-TV profits with D2C streaming profits. For ISPs who do not have pay-TV services today, the D2C streaming trend offers them an opportunity to generate new revenues from their network infrastructure.

The Technical Specification Headlines

Open Caching is a technical specification – not a standard – that enables CDNs to interoperate with other CDNs within an Open Caching network. This provides the necessary building block for Content Providers to have simpler and more efficient standardized interfaces across multiple CDNs, and for ISPs to build out capacity that can be uniformly and easily used by the Content Providers. For Content Providers, Open Caching should be thought of as an overlay across multiple CDN domains (private CDN, public CDN, ISP-CDN). It would provide Content Providers with a way to manage their content delivery and their content in a consistent way, regardless of which CDN infrastructure is physically being used.

While Open Caching is positioned as a performance and operational benefit to Content Providers, the main financial beneficiaries are anticipated to be ISPs and their CDN partners who would carry the bulk of the content delivery responsibility. The commercial aspects of Open Caching are still in the early phases of being market tested, and will form the basis of a future article.

Some major industry players are behind the Open Caching initiative, including ISPs (e.g., BT, Orange, Telefonica, Verizon, Viasat), CDNs (e.g., Edgio, FastlyMainStreaming, Qwilt, Stackpath), technology vendors (e.g., ATEMEBroadpeakVecimaVelocix), and championed by what is currently a small set of content providers including Disney, Globo, Hulu, and Paramount. Notably, some major industry players not involved in the Open Caching initiative include Akamai and Microsoft.

The Open Caching (OC) technical specification covers three principal components:

  • Open Caching Node (OCN) – this is a server and its software that are deployed at the CDN Edge, whether that is inside the ISP network or peering with an ISP. OC specs can be used either to build an entire OC system, or to implement OC-compliant software on an existing CDN platform. The full vision for the OC specification that has ISP-owned Caches deployed inside ISP networks (i.e., the ISP’s OC-CDN) considers the OCN to be the final Cache in a multi-layered CDN architecture.
  • Open Caching Controller (OCC) – this software component allows content providers, CDNs, and ISPs to interact with the OC platform. It is the management component for delegations, configurations, content purging and pre-positioning, logging, and security. It must be deployed on a Cache prior to the OCN, not at the Origin, per Figure 1 below.
  • Request Router (RR) – this is the routing logic that directs viewers towards the appropriate OCN to deliver the content. There are three methods available in the OC specification – DNS, HTTP and Manifest. The RR logic exists at multiple layers of the CDN architecture, from the CDN Selector to the ISP’s OC-CDN.
Figure 1: Open Caching architecture (source, Streaming Video Alliance)

Figure 1: Open Caching architecture (source, Streaming Video Alliance)

With these 3 components, an API-based Open Caching solution can be constructed for a Content Provider, to which they can connect their Origin and CDN Selector systems. At that point, an Open Caching CDN will form part of a multi-CDN ecosystem. But in contrast to a public CDN service, albeit similarly to a private CDN (for more information about the Broadcaster Private CDN model, please refer to this article) or a proprietary ISP CDN, the ISP’s OC-CDN introduces “on-net” capacity and its associated QoE benefits.

But a point of clarification – being on-net (i.e., closer to the consumer) does not automatically mean perfect performance. There are still technical elements to consider in how a CDN service is architected (e.g., private dedicated capacity or multi-tenanted) and in how a CDN performs based on its software design (e.g., start-up times, session management, origin connectivity methodology). As an initiative, Open Caching is focused on these points, but so are other CDN suppliers that deploy CDN capacity inside ISP networks using their proprietary platforms.


Open Caching began in 2014 and was the foundation stone of the Streaming Video Alliance. This initiative has a clear ambition to improve the world of video streaming, and it has come a long way in the last few years. As broadcast-grade and broadcast-scale become hotter buttons for D2C streaming services, Open Caching could play a major part in delivering those requirements.

As Jason Thibeault, Executive Director of the SVA states: “The primary strengths of Open Caching are its openness and the fact it is API-based. This allows network operators, CDNs, and Content Providers to easily implement it through software upgrades to existing CDN infrastructure, rather than hardware changes. In addition, Content Providers can benefit from the single control-plane that allows for management of all caches across different delivery networks, while network operators can benefit from delivering popular content from an Edge deployed in their network that reduces backhaul network utilization.”

In the long-run the vision for Open Caching is that all CDN platforms will be OC-compliant and therefore enable a Content Provider to connect to all CDNs in a standardized way, to manage their unified CDN and their content through a single control plane.

Part 2 in this article considers the current state of Open Caching deployment, how Open Caching could revolutionize CDN capacity management, and what obstacles still exist before broad adoption can occur. 

You might also like...

Vendor Spotlight: Imagine Communications

Imagine supports media companies’ bottom line with “converged” technology platform.

Orchestrating Resources For Large-Scale Events: Part 2 - Connecting Remote Locations

A discussion of how to create reliable, secure, high-bandwidth connectivity between multiple remote locations, your remote production hub, and distributed production teams.

The OTT Lexicon For 2023: Part 1 - Is Our Terminology Getting A Bit OTT?

The world of streaming is defined by acronyms like SVOD, AVOD, FAST, OTT and more. But this leaves gaps and confusion in what is included in our OTT services. For example, what does a service like BBC iPlayer include? What…

Orchestrating Resources For Large-Scale Events: Part 1 - Planning Is Everything

An examination of how to plan & schedule resources to create resilient temporary multi-site broadcast production systems.

Sustainability Of Streaming: How Does OTT Compare With OTA? - Part 3

Parts 1 and 2 in this 3-part series analyzed the latest information about OTT and DTT energy consumption in the UK in the year 2021, concluding that there are important energy efficiency improvements to make in OTT, and some big decisions coming our…