No problem Fred. I'll have to summarize a bit though as there are lots of technologies that all work slightly different.
Essentially though, any individual bandwidth setting is all done at an aggregation device somewhere within your ISP. The actual media into your home, be it fiber, DSL, cable, wireless, has a hard top cap that is it's maximum. However anything they want to set below the maximum is usually done at the aggregation device. ISPs can do pretty much anything they want at this point, depending on the technology used.
This is one term often applied to the technical, maximum speed of a solution that enters your house or business.
For instance, a fiber connection to your home might use gear that tops out at, for example, 10 Mb/sec, 100 Mb/sec or 1 Gb/sec. The speed you get can be set at any number lower than the max but an upgrade beyond this maximum throughput normally requires a change in equipment and/or it's settings.
Available Rate (there are many terms for this depending on tech)
This is the speed you care about. The speed limit that your ISP has placed on you depending on the service you purchased. It is normally controlled at the aggregation device where your home's connection reaches the ISP. It's generally the point where your connection goes from being an individual circuit to joining 'the cloud.' This point is called a "Port". The port could be physical (your unique fiber plugs into the AG (Aggergation Device) or it could be logical (many customers are already travelling through the same fiber at this point but your network is still assigned a virtual port).
Your Port can be set to control all sorts of things just for you.
- Max upload speeds
- Max download speeds (up and down are often set differently)
- Max download/upload caps (if you push or pull more traffic, the total quantity of data per month irregardless of the speed, then you may start to pay more)
- Traffic shaping (some ISPs will give priority to certain types of traffic. For instance, regular web traffic may be given more maximum bandwidth than torrent downloads.)
- Blocking traffic (you may recall a certain wireless ISP that refused thier customers the ability to use Facetime unless they paid for a premium service)
- lots of other stuff
Generally, when you purchase a particular service you are paying for a certain package deal that states service levels like download speeds, monthly maximums, etc. Often they have profiles for each service level you can buy and they just apply that profile to your port when you sign up. Buy a better or lesser service and they usually just switch your profile. However technically, they can also tweak individual items if they want/need to.
For instance services like DSL have further limitations like distance and cable quality. House A might be 1 km from the ISP's serving office and is set to sync up at a top speed of 7.5 Mb/sec. House B which is 6km away from the serving equipment and maybe has smaller gauge copper cable to work with, might be synced up at only 1.5 Mb/sec to keep it more stable in those conditions. Ideally, they tell you what your house is capable of getting and you pay appropriately for that service level.
Over-provisioned cable can be adversely effected by the number simoultanious users on a loop of cable (dependent on design.) If they can not control individual maximums.
Fiber is usually your best guarantee of getting your purchased maximum but any service type can be reliable for speeds as long as it is designed and provisioned properly. There are just less limiting factors with fiber.
I can't address your individual situation of course but hopefully the above provides an understanding of how it works behind the scenes. People may correct me for technical details based on thier particular type of service, but please remember I was trying to generalize what happens over a very wide variety of services and tech. vendors. It was not meant to be a white paper.
With great power comes Awesome irresponsibility.