The Role of CDNs in Improving OTT’s Performance

Although OTT (Over-the-top) platforms have been around for over a decade, the COVID-19 pandemic — along with the stay-at-home orders and physical distancing policies it brought — has increased the demand for digital entertainment and thus stimulated the growth of the global OTT market. The global OTT market registered a revenue of nearly $110,1 billion in 2018 and is anticipated to surpass $438,5 billion by 2026. In Indonesia, OTT platforms are also gaining more and more popularity. At the end of 2020, there were around 66 million Indonesians who accessed OTT services.

At its core, OTT covers various types of services including content streaming, messaging, and VoIP, but, today, it commonly refers to video and movie content delivery platforms such as YouTube and Netflix. Compared to conventional platforms like cable or satellite TV, OTT platforms have gained popularity due to three main reasons: availability, flexibility, and relatively low prices. However, although a third of the world’s population have opted for the convenience they offer, to retain and attract more subscribers, OTT platforms must provide excellent customer experience by delivering content at the highest possible quality; service must be smooth, uninterrupted, and in the resolution required by users. CDNs, or Content Delivery Networks, are at the core of this drive for better quality.

How CDNs Improve OTT’s Performance
CDNs refer to a network of servers which are strategically placed in multiple locations to cache data. Generally, CDNs work to help OTT platforms provide a flawless user experience through two features: content caching and multiple points of presence. CDNs’ content caching ability allows content to be stored at the closest points to the end-users. Meanwhile, CDNs’ multiple points of presence ensure any request for content made by a user doesn’t need to travel to the origin server and back; instead, the content is served to the user from the nearest server. Both caching capacity and geographical proximity allow request-fulfillment to be much quicker, thus reducing latency and increasing the buffering speed. 

How CDNs Perform
To support OTT platforms, CDNs perform seven core functions.

Content Traffic Management
CDNs manage the ingress and egress of OTT content, moving it from the origin server to the final ISP network that will then transport it to the IP-connected device. To perform this function, a CDN utilizes multiple layers of servers: at least one edge cache server and several intermediate cache servers that buffer content between the origin server and the edge cache servers.

Session Management
CDNs initiate and manage streaming sessions. Every unicast stream is characterized by dozens of stream parameters such as IP address, device type, and bitrate, so each must be monitored and managed. 

Content Storage
CDNs have high-performance, multi-faceted storage functions, from long-term storage such as VOD assets (films, TV series, etc.) to shorter-term storage such as downloaded TV series episodes or live content that can be rewound.

Content Management
To ensure storage and bandwidth efficiency, CDNs are in charge of managing what stays on storage and what is deleted. Generally, a CDN’s cache servers use a First In First Out model, but if any item on the list is re-requested, it will be delivered and immediately moved to the top of the list.

Load Balancing
Load balancing is normally performed across all the servers responsible for delivering content. The load of a content requested will be divided as evenly as possible among the cache servers which are delivering the specific content.

Platform Monitoring
All hardware, software, and network should be monitored to detect outages and degradation and then redirect stream requests appropriately. CDNs can be configured for servers to either seamlessly failover the streams they are carrying or with a stream restart.

Scale-out Management
A CDN has the capacity to integrate new capacity (by bringing new caches online and adding them to the server group) to its network while it’s in-service, allowing OTT platforms to expand streaming and storage capacity seamlessly.

The features and functions mentioned above allow CDNs to support OTT platforms and other content providers in providing top-notch experience to their users. Therefore, as OTT services are gaining more popularity, CDNs are also becoming a vital architecture in today’s digital ecosystem.