Miles Quaritch
Member
From the FAQ
http://windows.microsoft.com/en-gb/windows-10/windows-update-delivery-optimization-faq
How does Delivery Optimisation work?
Delivery Optimisation works in two ways.
Download updates and apps from other PCs
In addition to downloading updates and apps from Microsoft, Windows will get updates and apps from other PCs that already have them. You can choose which PCs you get these updates from:
PCs on your local network. When Windows downloads an update or app, it will look for other PCs on your local network that have already downloaded the update or app using Delivery Optimisation. Windows then downloads parts of the file from those PCs and parts of the file from Microsoft. Windows doesnt download the entire file from one place. Instead, the download is broken down into smaller parts. Windows uses the fastest, most reliable download source for each part of the file.
PCs on your local network and PCs on the Internet. Windows uses the same process as when getting updates and apps from PCs on your local network, and also looks for PCs on the Internet that can be used as sources to download parts of updates and apps.
Send updates and apps to other PCs
When Delivery Optimisation is turned on, your PC sends parts of apps or updates that youve downloaded using Delivery Optimisation to other PCs on your local network, or on the Internet, depending on your settings.
http://windows.microsoft.com/en-gb/windows-10/windows-update-delivery-optimization-faq