What software services run on top of a CDN?

Just as important as a highly distributed CDN platform are the software services that run on top of it. While many CDN providers support a primary set of performance-enhancing features such as caching, dynamic site acceleration, and adaptive bit rate streaming, the varying levels of intelligence built into these services differentiate their real-world performances. Moreover, as online interactions become increasingly diverse and sophisticated, companies need CDNs with forward-looking capabilities that cut complexity and allow them to leverage advancing web technologies to easily deliver the most engaging Internet experiences possible.


Web and Mobile Experiences


A decade ago, websites were relatively simple and static, and optimizing website performance was primarily about eliminating Internet latency in the “middle-mile”. By efficiently caching content close to end users and intelligently mapping users to the closest servers, CDNs could greatly reduce latency and improve the end-user experience. Today, Internet latency is still hugely important, but the situation is far more complicated, as sites and mobile apps are getting richer, more dynamic, and more complex with increased use of APIs and third-party content calls. Web page sizes have doubled in the last three years alone, due to steady weight increases in images, JavaScript, CSS, and custom fonts. Even worse, Responsive Web Design sites may suffer from “over-downloading”– a site design technique that delivers an optimized experience to both desktop and mobile users and can result in mobile devices requesting unneeded rich media assets meant for larger display devices. Moreover, devices themselves are getting more diverse. In 2012, there were roughly 4,000 different mobile devices in the marketplace; in 2015, there were more than 24,000 – creating a hyperfragmented landscape of form factors, browsers, operating systems, and device capabilities to support.

Delivering a speedy and engaging experience to every user, every time in this complex and fast-evolving marketplace requires a CDN with a broad set of intelligent services that work in concert to optimize each end-user experience. These services include advanced caching, dynamic site acceleration, front end optimization, image management, API and mobile app acceleration, and predictive acceleration.


Advanced caching capabilities


While caching is a basic CDN feature, advanced caching capabilities allow a CDN to cache more content – and cache it more efficiently – even as sites become increasingly dynamic. Most CDNs support the ability to set TTLs and ignore or follow various cache control headers, but differentiation comes in the granularity of control over cache rules and cache keys. An advanced CDN will also have powerful cache control engines to support a broad range of cache behaviors through flexible, nested rules with sophisticated pattern matching, and they offer the ability to key off of various request features including cookie values, query string, geo-location, partial URL, HTTP header values, or any combination thereof. This enables caching of many types of content that are typically thought of as dynamic — such as search results, API calls, product category pages, content targeted to different audience segments, and frequently changing content.

For example, by looking for the presence of a “logged in” cookie, a CDN can cache and serve all non-logged-in users one version of a site while fetching personalized content from the origin server for logged-in users. In many cases, a large subset of content may be the same for logged-in and non-logged-in users, and a CDN with advanced cache key mechanisms can serve all of this content from the edge, boosting website performance significantly.


Dynamic site acceleration


Truly uncacheable content requires a combination of dynamic site acceleration techniques including route and transport-layer protocol (TCP) optimizations. Several CDN providers claim to use TCP optimizations, but they are only truly effective with a highly distributed network that sits close to end users, minimizing the distance data travels over unoptimized routes. Moreover, whereas TCP optimizations work primarily by reducing the number of round trips required to render a webpage, another key dynamic site acceleration technology — route optimization — works by actually reducing the latency of each round trip.

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