Considering the type of platform that Twitch is, I’d be naive to think that the Twitch developers have not thought about using Anycast for their delivery method. In the past couple years it’s become more and more popular and proving to be an overall positive change for many different platforms (the latest I can recall is LinkedIn). So my question is rather simple - has the Twitch team considered implementing Anycast? If so, what are the pros / cons that have been brought up? If not, are there any reasons why you would be against it?
You most likely won’t get a Twitch response about this since they don’t tend to respond to inquiries about their infrastructure.
Twitch already uses Anycast for its CDN, as does most every website using a CDN. If you’re wanting video over Anycast then that is a different beast to scale, which might be why Twitch may be hesitant to implement it. Twitch only has a certain amount of bandwidth to each edge server and each edge server may not have the same video content of its neighbor. Twitch currently balances traffic to each edge with their Usher server, which redirects users to the closest server based on their IP geolocation and where the video is syndicated.
It is important to note that Anycast is a network-level routing that directs traffic to the nearest server. Since streaming video is extremely bandwidth intensive, it may make it a lot more complicated to handle the network against congestion (especially when there’s a lot of traffic redirecting being performed and not every video edge has the same syndicated video). Twitch can already easily manage congestion in locations by making their Usher service direct requests to a different location. It’s may also be more cost effective the way they do it now.
Twitch has been serving some video over what seems to be an Anycast CDN powered by Level3, but much of its video is still served from its own edges in PoPs globally.
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