With the proliferation of Mac and iOS devices in every corner of your home and office, you may have no idea just how much of your Internet bandwidth is being used to download content from Apple's servers. A caching server can help you make sure all your devices are up to date while leaving your Internet bandwidth almost untouched.
According to Apple, Apple's Caching service, which is a part of Apple's $20 Server app:
...speeds up the download of software distributed by Apple through the Internet. It caches all software updates, App Store purchases, iBook downloads, iTunes U downloads (apps and books purchases only), and Internet Recovery software that local Mac and iOS devices download.
What this means, practically speaking, is that instead of making all the Mac and iOS devices in your network run out over the Internet to download and update content from Apple's servers, you can host those updates on your servers, which makes for faster updates and less external bandwidth usage.
Think of it this way: It's Monday morning and Apple has released a new OS update that is 500MB in size. If you have 50 Macs and each one of those devices has to connect to Apple's servers over the Internet to download the update, that's 25GB of data downloaded directly from Apple using a connection that is much slower than your private network. If you're using a caching server, 500MB gets downloaded from Apple and the other 24.5GB are downloaded from your server, making the most of your faster network speeds and reducing the amount data downloaded from the Internet.
Here's how it works:
The beauty of the caching service is that it requires very little configuration on your part.
That's it! There's nothing else you need to configure.
Caching Service
You can set up the Caching Service by selecting Caching in the Services sidebar in Apple's Server app.
Once you've installed the Server app you'll find the Caching server under the services section in the sidebar of the Server app. (If the service is already running you'll see a small green light next to it.) When you select it you'll see three sections:
Once you configure your settings, turn the server on and it just works, invisible to everyone on your network.