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

Lars Eggert lars.eggert at nokia.com
Sun Jan 6 01:06:07 PST 2008


On 2008-1-5, at 13:16, ext Injong Rhee wrote:
> I am not sure either whether it is the job of  IETF to prove it is  
> safe and harmless-- how do they know?

when the IETF publishes RFCs, it needs to classify them into  
Experimental or Standards tracks. (There are also BCPs and  
Informational RFCs, but those aren't quite appropriate here.) So it is  
the IETF that needs to decide whether something is "safe for  
experimentation" and under what conditions (Experimental RFC), or  
whether something is "recommended for production use" (Standards Track  

Because congestion control is essential for the stable operation of  
the Internet, the transport area has a pretty high bar for declaring  
something "recommended for production use." I agree with you that what  
is needed to pass that bar isn't well-defined. I don't think it can be  
- different proposals will require different arguments based on  
different kinds of data in order to come to consensus in a WG on  
whether it is safe for experimentation or not, or can be recommended  
for production use or not.

There are currently three TCP variants (CUBIC, C-TCP and HTCP) that  
have made the jump from research paper to preliminary specification as  
Internet Drafts. As you know, the transport area has asked the IRTF's  
congestion control research group to help evaluate which of these  
three should be published as Experimental RFCs. (See http://www.ietf.org/IESG/content/ions/ion-tsv-alt-cc.txt) 
  I fully expect several of the three or even all of them to be  
published as Experimental RFCs.

After there is some experience from that experimental deployment,  
we'll think about recommending one of the variants (or maybe a spinoff  
or merge of one or more variants) for production use.

>  When those "standard" algorithms are IETF standardized, had they  
> more evaluation than CUBIC/BIC? At best, they had ns-2 simulation.  
> Back then there is no definition of realistic traffic patterns.

Well, the whole Internet was a small experimental testbed back then,  
and one with broken congestion control. That's very different from the  
current situation, where we have a commercial internetwork that has  
functioning congestion control (in the sense of preventing congestion  
collapse and establishing some sort of fairness) and there is a desire  
to deploy modifications that incrementally improve that congestion  
control under some conditions. Today, we need to be careful not to  
break something that works. Back then, people were fixing something  
that didn't work.

Finally, I'm personally very happy to see new research work coming to  
the transport area! Although the IETF standardization process can be  
tedious and takes time, the in-depth review and implementation efforts  
that often go along with it do improve the quality of the result.


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