media delivery in websites

How big websits deliver media content to large number of users? Are there any video/audio stream开发者_如何转开发ing frameworks available? Do they store the big video clips in databases?

I know this is not a specific question; I am not looking for a perticular website - just thinking which is the most common way

CDNs. Content Delivery Networks. There are a few free options you can go with, but the best ones you pay for. With CDNs you can deliver your media to multiple nodes through TCP and UDP both. It works utilizing both Unicast and Broadcast.