Author: Brian Tarbox, Distinguished Member of the Technical Staff
There are a lot of factors working against traditional caching in video delivery. Content libraries continue to grow. Consumers are watching video on a wider variety of connected devices. And operators are increasingly relying on adaptive bit rate (ABR) streaming to manage video quality. All of these variables make content caching more difficult. Pieces of content are spread around, and customized versions make it less likely that any given file will become popular enough for operators to reap the benefits of caching.
However, that doesn’t mean caching should go away. At Motorola, we believe there is still a big opportunity for intelligent caching using a Content Affinity approach. In short, instead of using a stateless design where content is stored on different servers regardless of which chunks go with which other chunks, all of the bits from a single program should be stored together in one place.
There are huge advantages to caching content using Content Affinity. Although edge servers are no longer interchangeable since specific servers are designated to host specific content, the savings in both disk space and network bandwidth utilization are enormous. For example, if all requests for a copy of the movie Spiderman go to the same server, there is a far greater opportunity for fragment re-use than if the streams for that movie are distributed randomly to several dozen servers. That fragment re-use can lead to significant reductions in storage and streaming costs.
It’s important to note that Content Affinity works best in large-scale deployments. First, the complexity of such systems means that caching benefits must outweigh the cost of designing and installing an effective caching architecture. Second, the bigger a deployment, the more data is available on content use, which makes the predictive function of caching more reliable and effective. In other words, tier two and tier three cable systems may not benefit from content caching, but larger operators still have much to gain.
Historically, intelligent caching has proven its worth as a mechanism for operational savings. Even in a multi-format and fragmented delivery environment, that benefit should not be discounted lightly. Our modeling shows that many operators can benefit from a combination of both adaptive bit rate streaming and intelligent caching.
For more on caching configurations with ABR streaming, see Motorola’s presentation at The Cable Show in the session “We Accept Cache: Intelligent Design for Media Storage and Delivery,” Tuesday, May 22, 2012, at 3:30pm in Room 157AB East or visit us at booth #733.
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