[Iccrg] congestion control and visability to the user

[Mikael Abrahamsson]

On Mon, 29 Mar 2010, michawe at ifi.uio.no wrote:

> My notion was that it's not, usually, because of standard TCP
> being "lame" (as Matt rightfully called it).

This is the first time in my 15+ year of networking that I've heard this 
view of the world. I couldn't disagr ee more. Only time I wasn't able to 
saturate my access link was when I was using Win95 or so, and it didn't s 
upport window scaling and my internet connection was 100+ megabit/s and 
the ftp server was 10ms away. I could n't disagree more with this view of 
the world.

> However, in this world of CUBIC in Linux, a growing number
> of users with proper buffer sizing / window scaling, and,
> above all, users (or their (P2P) applications) opening as
> many connections as they need, I can imagine that what
> you say is true.

I don't kno wwhat part of the world where this hasn't been true for a 
long++ time, but it's not in my neck of the woods.

> Well of course economical reasons are there. Bandwidth
> costs money. So, is all we're doing here with congestion
> control only about:
> 1) managing fairness within the user's local networks, and
> 2) making the network operate even if ISPs don't investe
> in enough core bandwidth, which apparently hardly ever
> happens?

Again, ISPs only get away with congesting their cores if there isn't 
enough competition in the market, and that's not a technical problem, it's 
usually a political problem. Trying to handle this dysfunctional situation 
by technical means is bound to fail. Why would someone invest in expensive 
bw capacity/congestion/flow/fairness technology if said upgrade due to bw 
constraints is already too expensive?I don't get it.

> XCP was really just an example. The point was that, given
> that we can get a benefit from explicit feedback for
> congestion control, it might be enough to do it on the
> first and last hop, where doing it might actually be feasible.

In my experience, the biggest congestion problem is in the upstream 
direction from my CPE. Any normal user would have an ADSL modem or alike 
there from some low-end manufacturer who won't invest a dollar more to do 
anything more than FIFO because they're acting in an extremely tight 
marketplace where every cent counts. There is already plenty of tech out 
there to help in this siuation but they've chosen to do nothing. 
Fair-queue is one which would hugely benefit all ADSL users (or anyone 
with slow uplinks). This is not being done, and yet people are talking 
about inveting eve nmore complicated mechanisms?

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se