[e2e] Are we doing sliding window in the Internet?

Mon Jan 7 02:46:47 PST 2008

References: <003801c73448$713c10c0$6e8944c6 at telemuse.net> <45A4D230.5020105 at web.de>	<477D6A3E.7080900 at isi.edu> <603BF90EB2E7EB46BF8C226539DFC20701316AE2 at EVS-EC1-NODE1.surrey.ac.uk> <477DA1D1.50809 at reed.com>	<477DC5DA.6070800 at isi.edu> <5640c7e00801032220h1fa945b9k61a01c70235fb035 at mail.gmail.com> <477E5677.6010808 at isi.edu>	<200801041713.RAA29230 at cisco.com> <477E6D30.1080905 at isi.edu>	<477E96B2.3000600 at reed.com> <477EAEBE.9080906 at isi.edu> <AFE0AC8DCDE68842B94E8EC69D5F21D635EB120231 at NA-EXMSG-W602.wingroup.windeploy.ntdev.microsoft.com> <477EC061.4080101 at isi.edu> <AFE0AC8DCDE68842B94E8EC69D5F21D635EB12025E at NA-EXMSG-W602.wingroup.windeploy.ntdev.microsoft.com> <477EC65D.1010606 at isi.edu>	<477ED546.6040005 at psg.com> <477EEA23.8070901 at reed.com>	<071424AB-2FEB-418E-AEDA-849913F9D0B4 at ncsu.edu> <477F18D9.30106 at isi.edu>	<700B57DF-259E-45F0-8234-AE1D504D8027 at ncsu.edu> <477FB5AB.3090601 at isi.edu>	<F204A621-B1F0-4699-8E72-5D4409F6006B at ncsu.edu> <47806455.8040508 at isi.edu> <6C616168-133B-4314-81!
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Hi,

On 2008-1-6, at 21:51, ext Christian Huitema wrote:
>> It's important to remember the two reasons for congestion control  
>> from
>> Sally's RFC2914: preventing congestion collapse and establishing some
>> degree of fairness.
>
> Wait a minute. This is equivalent to saying that continuous  
> stability of the Internet depends on the benevolent cooperation of  
> all Internet users. The implementation of slow start in TCP did  
> indeed prevent the Internet to collapse at a crucial time in its  
> evolution. But that was then. I don't think we can extrapolate the  
> 1988 fix into an everlasting principle, not with a billion hosts on  
> the Internet.

this is taking us pretty far away from the context in which I made the  
statement you quoted above (what we learn from the current CUBIC  
deployment), but anyway:

I'm not saying that end system transport-layer congestion control is  
all that we'll ever need, especially when end systems become selfish.  
But I do think that the stable operation of the Internet has been  
depending and probably is still depending on the majority of the  
traffic being sent over congestion-controlled transport protocols.

If that changes (and my nightmare scenario is that the BitTorrent guys  
realize that they don't need to use the in-kernel TCP stack, all they  
need to use is the TCP packet format), yes, then we do need something  
else, as you say below.

> In that research on "network based" mechanisms, we should accept  
> that end systems will be primarily motivated by their self interest.  
> They are certainly not motivated by a desire to be fair with others.  
> The desire of fairness is a social contract, and I don't think we  
> can assume such a contract when the Internet covers the entire  
> world. If we could, that would indeed be a good thing, we would also  
> have worldwide peace and all that kind of thing. So, we have better  
> assume that end system will try to maximize their individual  
> satisfaction, rather than looking for the common good. If we cannot  
> rely on the benevolent sum of individual behaviors, we need to build  
> mechanisms in the network that help it guarantee its stability.
>
> In fact, ISP are already attempting to build this "stabilization  
> tools" in their networks. We see various forms of traffic shaping  
> implemented at bottleneck points. We see various tools used to  
> perform "traffic engineering". ISP need to do that if they have any  
> hope of providing some kind of guarantees of service. Many on this  
> list will find those tools crude, or possibly harmful. Fine, but the  
> reaction cannot be to retreat in the ivory tower and leer at those  
> lowly network engineers. Instead of clinging to the illusion that we  
> can entirely solve the problem in an end to end fashion, that all  
> end systems will follow the dictate of the E2E group, maybe we  
> should actually address the problem. What is the best mechanisms to  
> deploy in the Internet to make it immune to variations in end to end  
> algorithms?

I agree with you that there'll need to be something that protects the  
network and other users from selfish end systems, and it will need to  
be a mechanism that doesn't only rely on the cooperation of those end  
systems.

But I'm also not convinced that this functionality should completely  
move into the network, which is what I think ISPs are currently  
attempting to do. An architecture that gives incentives to the end  
systems to behave correctly, rather than controlling everything  
network-side, appears more viable to me. (And we've just gotten some  
EU money over the next three years to look at how such a system would  
look in detail.)

Lars