The new content system is designed to do two things: deliver better download rates in more places around the world, and also to simply streamline the publishing process on Steam, ultimately making it possible to ship more games than we would have been able to with the old system.
The maximum aggregate bandwidth of the system will be greater than the current system; this will help us satisfy spikes in demand when there’s a big release. We will also be able to send content from more places, to better serve people all around the globe. All the content on the new system is sent via HTTP; this is more firewall-friendly than the current system, and will automatically take advantage of web-caching proxies installed at ISPs.
Another way that the new content system improves the bandwidth picture is by requiring each user to download less data. With the Steam content system that’s been in place for a few years now, if an individual file on disk were modified by a game update, your client had to download the whole file. That can be painful when the file in question is really large. The new system supports delivering only the differences between the old and new files, meaning game updates will be much smaller overall.
These changes have given us an opportunity to write new tools for game developers and content publishers that simplify the process of both publishing and updating a game on Steam. Simplifying the publishing process means it takes the partner and us less time to ship each product, so we can ship more stuff to more users.
In addition, the new content system will allow us to build several new features that we’ve often heard requested. Upcoming client releases will include things like download scheduling, bandwidth throttling, and prioritizing which games get downloaded first. You’ll also be able to download an update to a game while you’re playing that game; Steam will apply the update after you exit the game.
Over time, more and more of the content on Steam will be delivered using this new system. Soon, Dota 2 will be delivered using it. In the meantime, if you’d like to try out this new content system you can do so right now; if you download a 1280x720 (HD) trailer from the store, it will happen via the new content system.