[e2e] why fair sharing? ( Are we doing sliding window in the Internet?)

Jon Crowcroft Jon.Crowcroft at cl.cam.ac.uk
Sat Jan 13 02:43:27 PST 2007

yes indeed...

the use of congestion avoidance is to avoid congestion at shared points in the
net, which _should_ be an unusual occurrance (by definition)

but: most nets should be designed for the expected traffic load
with some design headroom for variance. when i get x million DSL users, I _know_
what the rate is that they are limited to at their access line. I can build a
core for that, and i can peer or connect to upstream tiers with capacity in line
with that. i can also engineer for p2p traffic.

the congestion experienced often by academics and researchers and people working
for techy geeky companies is because they don't have a
designed network and don't pay proper prices for impedence matched networks - we
have a 10Gbps access line to the internet in cambridge - many departmtnts have
gigE attachments to the net - TCP encourages (doesnt avoid) congestion:) in this
scenario. but it isnt the scenario experienced by the great unwashed public
Internet users.

bob briscoe's note is good reading, but it talks to the situation where people
have way faster access lines than their mean access use. this isn't the dominant
situation in the commercial net where DSL (and cable ) broadband access can be
co-designed/dimensioned with the core net provisioning.

in this case, customers get what they pay for (If i want 20Mbps DSL, I can get it
easily, but i pay more than i do for 8Mbps or for 384kbps all in line with the 
ISP maximising profit subject to competition with Other ISPs controlling them
meeting the users utility/satisfaction - this is all discussed in Kelly's work
quite nicely

actually, if TCP used ECN right (again, other bob briscoe work) it would just be
achinveing the same as this argument (kelly etal) but just on a shorter timescale
if ECN pricing was done right (see re-feedback etc etc) but if you strive for
"fairness" in the current world, you are striving for an illusion

In missive <Pine.LNX.4.44.0701121747490.18433-100000 at gato.kotovnik.com>, Vadim Antonov typ

 >>On Fri, 12 Jan 2007, John Wroclawski wrote:
 >>> Along these lines folks might want to read Bob Briscoe's internet 
 >>> draft "Flow Rate Fairness: Dismantling a Religion", Bob Briscoe (BT), 
 >>> IETF Internet-Draft <draft-briscoe-tsvarea-fair-00.pdf>, can be found 
 >>> in many formats at 
 >>> http://www.cs.ucl.ac.uk/staff/bbriscoe/pubs.html#rateFairDis
 >>Pretty much my point all along.
 >>I have one issue with the paper, though -- they advocate fairness based on
 >>"the costs, not benefits".  That shows that they didn't really thought
 >>about economics. The real-life enterprises (such as ISPs) maximise profit,
 >>so they are interested in giving most profitable customers a bigger share
 >>and penalize less profitable customers - thus creating incentive to pay 
 >>more for the better performance.
 >>The cost-based allocation does not work economically, as it encourages 
 >>incurring higher costs in order to obtain higher benefits.



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