Throughput and why do ISPs sell too much bandwidth?
- by jonescb
I hope the question made sense how I worded it. :)
I've been wondering, maximum theoretical bandwidth is measured as RWIN/RTT (Window size / round trip time)
Source 1 and Souce 2
So if a major city only 100 miles away gives me a ping of 50ms, and I have the default 64kb TCP window size then my maximum throughput will be 12.5Mb/s. Everything further away would give me a higher ping and therefore a lower throughput.
Is there any reason to buy something like FiOS with a 50Mb/s or greater connection? Will you ever be able to reach that kind of speed?
I know you can increase the TCP window size to increase throughput, but it has to be at both ends which is a deal breaker because you can't control the server.
I'm assuming other network protocols like UDP aren't quite as affected by latency as TCP is, but how much of overall network traffic does non-TCP make up vs TCP.
Am I just misguided about how throughput works? But if the above is correct, then why should a consumer like me buy way more bandwidth than can be realistically used. Maybe the only reason is for downloading multiple things at once, or one thing from multiple servers/peers?
