[e2e] opening multiple TCP connections getting popular

Bob Briscoe rbriscoe at jungle.bt.co.uk
Thu Aug 30 11:13:39 PDT 2007


Yes, congestion control deals with congestion anywhere on the path which is 
correct. And your ISP should be able to limit you based on total volume of 
congestion you cause anywhere on the paths you are using (acting on behalf 
of the other networks). But at present, your ISP only knows about 
congestion in its own network.

The proposal I've made allows it to know about congestion on the e2e 
path.... And it allows yuor ISP to know about how much congestion is 
upstream and how much downstream of any point. So other networks can use 
this metric in SLAs to make it want to act on their behalf.

All using 1 bit in the IP header along with the ECN field, but without 
changing any existing network elements.

Probably best to read the proposal I've made. Choose a paper from
with a description that best matches your interest.


At 17:49 30/08/2007, Detlef Bosau wrote:
>Bob Briscoe wrote:
>>1/ This isn't just an issue between a user and her local ISP. Shifting 
>>the focus from your personal DSL use (which is probably to an 
>>over-provisioned academic campus at the other end), a typical filesharing 
>>user is just as likely to be hitting a bottleneck in another ISP's 
>>backhaul (or bottlenecks in both local and remote backhauls).
>>Even if her bottleneck is remote, I'd still like her to be able to behave 
>>like w TCPs, but we need a simple accountability framework that allows 
>>her own ISP to choke her if she causes excessive congestion, whether the 
>>bottleneck is local or remote (which, as you know, is what I've proposed).
>Isn´t this exactly, what CC does? If congestion causes harm, i.e. dropped 
>packets, these drops will choke the connection.
>>2/ If everyone was trying to fill their access link with TCPs (or MulTCP) 
>>continuously, the bottlenecks would nearly always NOT be their own lines, 
>>no matter how carefully they spread out the traffic. This is in fact 
>>close to the current situation - even without everyone participating in 
>>p2p filesharing, bottlenecks have already moved out of the lines into the 
>IIRC, this is one of the Todos, Sally Floyd mentions on her open questions 
>list: Where is the bottleneck?
>However, stupid me, to my understanding any congestion drop simply 
>throttles the connection. And that´s exactly what we want to do.
>To my understanding, your point is mainly the target function, you want to 
>optimize, and the fairness criterion.
>And a pure e2e approach is limited here because the individual socket does 
>not see the big picture of your network, neither your prefered fairness 
>criterion or target function.
>In some respect, this is similar to the Ethernet capture effect (which was 
>found by Keshav IIRC?).
>Without any central- / point- /... coordination function / admission 
>control / ressource control, you will most likely find more or less 
>strange cases which cause "surprising" results.
>Detlef Bosau                          Mail:  detlef.bosau at web.de
>Galileistrasse 30                     Web:   http://www.detlef-bosau.de
>70565 Stuttgart                       Skype: detlef.bosau
>Mobile: +49 172 681 9937

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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