Measuring the energy impact of hybrid peer-to-peer / CDN video delivery: initial takeaways (Lumen)
In this work, former colleagues have assembled the last pieces of a project on which I have contributed before leaving the company. Topic is video delivery, the biggest chunk of internet traffic in the last years, and how we can optimize the energy consumption of its delivery.
Classical way to serve that traffic is through CDNs, constellation of cache servers close to the people who consume the content. The article shows that combining CDN with the special technology developed by Lumen is a way to optimize the system as a whole, bringing energy savings of factors two or three.
The tech is peer to peer video delivery: user A and user B watch the same stream online. User A downloads content from CDN but user B does not have to, because user A will forward the data to user B through a direct WebRTC connection, similar to what video chats do.
This reduces a lot the strain on CDN servers, by up to 80%. But the extra energy consumed by user A in this example is to be compared to the wattage spared on the CDN side. It turns out that CDN servers are so heavily optimized that the small power increments at the many end users' side add up to more than the CDN saving, so that enabling peer to peer in the general case is not worth it.
But video traffic is usually peaked, meaning lots of people watch in the evening, and almost nobody does it the rest of the day. The article takes real production traffic shapes and demonstrates that enabling a power hungrier tech (P2P) for a short part of the day is better than having an efficient CDN run the whole day, during peaks of traffic (good) but also when nobody watches the streams (bad). Indeed, CDN has to be sized for traffic peaks and will stay idle most of the time, while P2P scales linearly with traffic.
The goal is then to smartly allocate traffic between CDN and P2P to optimize the savings. Some strategies are detailed in the article.
To conclude, for standard traffic shapes, P2P video delivery is a key contributor to greener operations. On top of being a fascinating technology.
See my lighning talk with Sanket Shettennavar at Demuxed 2022 on this topic
Lumen Mesh delivery homepage: https://www.lumen.com/en-us/edge-computing/mesh-delivery.html (formerly Streamroot)