Can QoS for a corporate environment be adjusted to prioritize traffic from SharePoint online so that improves user experience when uploading/downloading large files? My network team is telling me no because the SharePoint URL is outside the network. I am probably wrong but isn't QoS used for precisely prioritizing types of traffic for users? Thanks for helping me understand. Thanks
QoS is of no use if the traffic is going on the Internet, simply because almost no ISP is acting on QoS markings (in fact, it's normally stripped automatically when entering their network)
For QoS to be useful at all, all nodes in the path (routers, switches, etc) mustn't reset the marking and also must ACT on it (ie: if you have "DSCP EF" marking - normally used for Voice & Video, if the switch doesn't strip it but doesn't prioritize those packets, it doesn't help)
That is why your Network team told you that they can't do anything - unless there are some network bottleneck on your own network, if you go out the Internet where QoS isn't used, everything is "Best Effort" and every stream is (supposedly) treated equally (your Sharepoint traffic isn't more important to your provider than your're co-worker web requests).
Even if you had a special understanding with your provider, they're connected to others and so on and so forth, until you reach the Sharepoint servers. If any LINK used to reach those doesn't support QoS, then you have NONE.
TL;DR: QoS is NOT supported on the Internet at large
There are two issues here:
First, can you identify Sharepoint traffic exclusively? Since it uses ports 80 and 443, it's hard to distiguish Sharepoint from normal web traffic. I assume you don't also want to prioritize cat videos. To identify Sharepoint reliably, you need deep packet inspection -- that takes a lot of network horsepower.
Second, are you sure that network congestion on your internal network is really causing the problem? Is all web browsing slow? You say your Sharepoint sites are external to your network. There are many possible external causes for slowness that you have no control over, and QoS will do nothing to help that.