[e2e] opening multiple TCP connections getting popular

Bob Briscoe rbriscoe at jungle.bt.co.uk
Wed Aug 29 09:23:38 PDT 2007

e2e-interest folks,

This product is being very aggressively marketed:
It opens 10 HTTP/TCP connections to accelerate video downloads - 
essentially using the well-known broken feature of TCP (see the I-D below) 
to enable one user to compete more aggressively for the same bandwidth 
against other users. But it flies below the limit of 10 concurrent half 
open connections added to Windows XP SP2 - claimed to be added to slow down 
worms but also limiting p2p filesharing clients.

Amazingly, these guys are approaching ISPs to re-sell this product - so 
their customers will just be competing more aggressively with each other 
and largely end up back where they started. It's worth reading the Business 
Week article linked off the above page to see just how convincingly this is 
being marketed - They fooled the technology assessment people in at least 
one large ISP (mentioning no names).

If you're tempted to poke fun at all these people because they clearly 
don't understand, I actually think we should be chastened ourselves. Why 
shouldn't app-layer people expect the transport layer to correctly handle 

To quote the Internet Draft "Flow Rate Fairness: Dismantling a Religion"
"...flow rate fairness isn't even capable of reasoning about questions 
like, "How many flows is it fair to start between two endpoints? ...
...there will certainly be no solution until the networking community gets 
its head out of the sand and understands how unrealistic its view is; and 
how important this issue is--a conflict between the vested interests of 
real businesses and real people."

King Cnut commanded the tide not to wash over him sitting on his throne on 
the English beach, but at least when the experiment failed he humbly 
accepted he was subject to greater powers, never wearing his crown again. 
I'm worrying away at the IETF to work on a proper solution to the 
TCP-fairness problem, rather than merely issuing the decree that RFC2616 
HTTP/1.1 clients should observe a 2 connection limit to each server.


Bob Briscoe, <bob.briscoe at bt.com>      Networks Research Centre, BT Research
B54/77 Adastral Park,Martlesham Heath,Ipswich,IP5 3RE,UK.    +44 1473 645196 

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