We have better performance because we have better architecture

Better Network Architecture for Improved Cache-Hit Ratio

When content delivery networks (CDNs) were founded over 15 years ago, the internet was very different from what it is today. Content was uniform, internet access was wired (mostly through telephone lines with limited bandwidth), internet transit was expensive, and interconnection between ISPs was limited. Naturally, the ideal topology was a highly distributed network with extensive last mile coverage by passing transit, which meant having an astronomical number of servers and nodes. This is what worked for the internet of yesterday. The first blog of the series focused on how our CDN delivers Better Performance, this blog will touch on the key points of why our better architecture drives better performance.

Today, ISPs and carriers are well interconnected. Content is highly personalized. Since internet access is no longer limited to telephone copper lines, it is now available from broadband ISPs via cable, fiber and wireless. A highly distributed network is no longer necessary in the modern internet architecture and has become a hindrance to efficient caching behavior. Verizon Digital Media Services’ CDN was architected to take advantage of the modern internet landscape. Instead of having thousands of small points of presence (PoPs) scattered throughout the globe, our strategically placed Super PoPs have massive computing power and high-bandwidth capacity at density internet connection points. This modern architecture delivers better performance by achieving better cache-hit ratio, better server-to-delivery ratio and better reliability.

Better cache-hit ratio. When content, such as a videos, images or files, is not cached inside the CDN, the edge server makes a request back to the origin server to obtain a copy of the content. This is called a “cache miss”. In a cache miss, the user does not enjoy the benefits of a CDN because the request is routed back to the origin server, as if a CDN didn’t exist. When this happens, you incur increased costs associated with more origin load and bandwidth costs. A cache hit is when the CDN has the requested content in its cache available to the user from its edge server. The higher the cache hit, the better the user experience. In a highly distributed architecture with tens of thousands of PoPs, it means tens of thousands of cache misses occurring before the content is fully loaded into a CDN. In today’s internet where content is highly personalized, highly distributed topology results in frequent cache misses that are detrimental to the user experience. A centralized topology like Verizon Digital Media Services results in more cache hits, not cache misses.

In addition, we’ve engineered a horizontally scalable PoP architecture that load balances at the application layer. So, even with hundreds of powerful servers within a Super PoP, an object is stored once within one of the servers. The Layer 7 load balancing allows hundreds of servers to become one titanic-sized computing infrastructure within a Super PoP. This architecture allows each Super PoP to have a larger usable cache footprint to cache content and translates to an average of 95 percent cache hit ratio for our customers, a significantly higher figure compared to legacy CDNs.

Better server-to-delivery ratio. A CDN is used to deliver to any surge in demand, expected or unexpected. If you’re maintaining excess equipment and capacity just for the occasional spike in traffic, you know that it is highly inefficient and very expensive. Therefore, cloud-based CDN services allow customers to meet surge without the unnecessary overhead. Furthermore, by concentrating computing capacity and massive bandwidth, we offer the best server-to-delivery ratio of any CDN, making us better positioned to handle massive spikes in traffic without degradation to user services.

Superior reliability. Centralized distribution combined with horizontal scaling also provides for higher fault tolerance without affecting the user experience. Our proprietary design creates redundancy to recover from hardware failures and the capabilities to withstand attacks.

With a CDN, more isn’t always better; more points of presence are actually less efficient. Next time a CDN brags about having hundreds of thousands of servers scattered among tens of thousands of point of presence, you should think about all the cache misses, the points of failures, and complexities involved with making changes and updates.

Verizon Digital Media Services operates differently. We’ve built the next-generation CDN with better architecture to provide better cache-hit ratio, better server-to-delivery ratio and better reliability.

Contact us to learn more.

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