Yes, and no.
If you are a given a limited resource (in this case, a physical port that can process no more than 1gbps for example) and your efficiency in transferring data over that port is not 100%, the provider itself is not to blame. Each and every protocol has limitations, and in this case we are talking about payload I guess. What the provider should say is: if you need "true" 20mbps, then instead you should contract 20mbps X 1+your-payload-process-loss.
That's fine as long as they're giving you a resource that can potentially transfer the 20Mbps.
A silly example would be this: you fill your gas tank with 12 gallons... After driving until it's empty, your engine only used an average of 6 gallons to actually move you from point A to point B. The other 6 were just wasted in form of heat. Do you ask for your money back at the gas station? Or maybe you invest in a hybrid car?
That *is* a silly example. A more proper analogy would be that you buy 12 gallons of gas, but the station only deposits 11 gallons in your tank because the pumps are operated by gasoline engines and they feel it is fine to count the number of gallons pulled out of their tank instead of the amount given to the customer.
Like I mentioned before, this is not unique to networking, it's a broader concern in the design of any system or process.
Finding new ways to give the customer less while making it look like more has a long, proud history, yes. ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.