Introduction to ACD - Agile Content Delivery.

ACD is a software suite for CDNs (Content Delivery Networks). The services built around the ACD software come into play when a user starts to view video content on a video streaming portal. The focus is on the server side of the delivery. The portal and players or set-to-boxes are not part of ACD, although they are part of Agile Contents product portfolio as a whole. Likewise, video stream repackaging and DRM are not part of ACD (see ACP).

The ACD software can be used to build a complete private CDN and/or to select between CDNs. A typical deployment is a nation-wide TV streaming service operated by a telecom operator or a broadcaster.

At the core of the system sits ESB3024 Router which will process an incoming client request and make an optimized decision from where to serve the user. The router will classify each playback request according to a variety of configured parameters such as device type, geographic region or content class. Based on the classification together with the current state of the network, its streaming capacity and public offload CDNs status, the best streaming location is determined. If desired, business rules for when to use public CDNs can be applied.

The ACD software suite includes the ACD Cache that is installed on servers placed in data centers that will guarantee an efficient and robust distribution of the content. Depending on the core network architecture, a centralized or decentralized approach is best. Agile Content can help find a good system solution.

Behind the client facing interfaces, there are backend services to monitor and measure the system. This information can be used to troubleshoot network problems, analyze viewing patterns or to plan upgrades of capacity.

Returning to the router, it is built around a very flexible routing rule evaluation engine that can route between and within CDNs. The rule evaluation engine weighs together multiple sources of information to optimize system behavior. Apart from the request classification of device type, content class etc, there are also several integration APIs that can be used to extend the product and solve problems that are particular to a specific customer. One of those integration APIs is the Selection Input API which can take any external information such as streaming bitrate of public CDNs, load balancing settings from a GUI slide bar or status from network probes and include it in the routing decision rules. Another is the Subnet API that can efficiently handle thousands of subnets and map each one to a high-level group membership (typically a region) and route based on that. There is also a metrics API to monitor the service. It integrates out-of-the-box with Prometheus and Grafana.

All APIs are documented under the API overview.

In addition to the flexibility provided by the APIs, there is also a possibility to extend functionality via plugins (using Lua). This can be used to support the decoding and encoding of security tokens (digital signatures of the URLs) or advanced routing rules that are not available out-of-the-box.

A modern TV CDN is considered as critical infrastructure and has very high requirements on uptime and robustness. This is in obtained via multiple independent and stand-alone instances of each service (although particular use cases might require sharing data via a redundant database). The ACD software services run on RHEL8 Linux.

Note: Not all products or components that are part of ACD are documented here. Please contact our Sales for a complete overview.