said by funchords:
The only people who can call this "technical" are the people who have been adequately buffaloed into thinking that George Ou knows what he is talking about.
He does not.
In all seriousness I truly do respect many of the things you post, but in this case George (while not 100% correct in his position either) is a heck of a lot closer to reality than you are in your counter arguments with him. Oversubscription at the edge is common in every network design; it's a matter of efficiency. Designing for full capacity for all edge ports is like designing freeways so that there would never be rush hour congestion; you'd bankrupt yourself in the process of building it.
The TCP fairness problem exists on the segments that experience saturation on a regular basis, which is generally the segment between the CMTS head-ends and the cable modems. Contrary to what George Ou posted the problem will present itself on both the upstream and downstream segments, but will manifest itself more readily in the lower capacity upstream segments.
You've stated a few times that TCP throttling is irrelevant because people are already limited by the upstream connection of their cable modem. That's a bit like saying "I still have checks, how can my account be out of money?!" The gotcha is that there is not enough upstream capacity for everybody to transmit at once, and when congestion occurs on the common upstream channel to the CMTS head-end, the TCP sessions will scale themselves in relation to capacity on the entire channel, not according to the provisioned capacity for each cable modem. For example:
Say you have an 8/1 service no a DOCSIS 1.1 network. Say you have 9 users all uploading in a single TCP session each at the same time, each user will get 1mbps to saturate out the connection.
Now say you had 18 users again all using a single TCP session, TCP will naturally balance things out so that each connection will average about 500kbps.
Now say you had 17 users, but one of the users had 2 TCP sessions. 9mbps channel capacity / 18 TCP sessions = 500kbps per TCP connection. That means 16 people will see 500kbps, and the 1 user using 2 TCP sessions will see 1mbps.
The numbers don't break down quite that neat in the field, but overall they're pretty close.