Of the many things I've learned about the internet, oversubscription has to be one of the least understood. All carriers oversubscribe at some level and they aren't even required to publish how much they allow on their networks.
Oversubscription can be explained with one example;
1 Neighborhood
1 internet circuit running to the neighborhood
15 houses
For ease of numbers sake, let's say that all of the houses subscribe at 500MB plans.
Generally, that's enough for a 'normal' house, probably even a bit too much… until…
A global pandemic hits, and everyone, including the children in the neighborhood are all home… ALL THE TIME.
A family of 4 who used the internet at different times of the day/night now use all of this at the same time, all day:
Work including video meetings (x2)
Online virtual school - WE LOVE YOU TEACHERS!!
Email/Slack/Discord/Teams
Gaming
Web browsing
Watching golf swing instructional videos
Streaming TV
Your smart home devices
Etc…
And they're doing it on multiple devices each, which adds to the perceived 'slow' speed of the network, because lots of data is being send and received through a single pipe.
So, that family upgrades their plan from 500MB -> 1GB/month. Makes sense, they want more bandwidth to share with the family… but…
…so do all other 14 houses on the street.
But, if 15 houses each have a 1GB connection, that makes 15GB - and the circuit is only 10GB… right?
Right.
So, if everyone was using their entire plan's bandwidth, there is too much data being sent over that circuit.
Packets are lost. Videos buffer. VOIP stutters. You hang on uploading that perfect picture to IG - the one where the entire family is looking at the camera at the same time!
The neighborhood-wide decision to increase internet plans actually made the situation WORSE and clogged the neighborhood pipe even more, and everyone's experience suffers.
So, how do you fix it? We'll you can't control which providers decide to put circuits in your neighborhood, and you can't tell them you need a circuit upgrade until it hits their "magical" oversubscription limit.
You can impose household limits on devices, use different quality streams on devices and applications, or go take a walk outside.
If business class internet is available, that could be a direction you can go - but it's more expensive, and still oversubscribes (though presumably not as much).
This is a common practice across all providers, and a necessity for providers to keep costs within reach.
Just remember that it may take a few extra seconds for your family photo to post during congested times.