Re: Spurious Timeouts, Fact or Fake?

On 08/03/2011 07:45 PM, Emmanuel Lochin wrote:
> Hi Detlef,
>
> I think the study on spurious timeout you cite cannot be transposed to
> the Internet.
> If you look at :
>
> Sharad Jaiswal, Gianluca Iannaccone, Christophe Diot, James F. Kurose,
> Donald F. Towsley,
> Measurement and classification of out-of-sequence packets in a tier-1
> IP backbone.
> IEEE/ACM Trans. Netw. (TON) 15(1):54-66 (2007)
>
> the authors show that 40% of the links present in their dataset
> effectively reorder
> packets (might due to load balancing, multiple network paths, dynamic
> route generation and link bonding).
>

Thanks again for the hint.

However, at the moment, I want to get a perspective for my own work and 
therefore, I need a somewhat constructive approach.

First of all, observing packet reordering on 40 % of the links in some 
reasonable dataset is worrying. And it makes clear that there is a huge 
difference between Internetworking in the RFC "theory" and the practical 
implementation.

Or, to put it into some perhaps dramatic words: To which deal are we 
doing sliding window in the Internet and to which deal are we doing some 
crude mixture of loss recovery and slow start? Some kind of stop'n wait, 
and now and then there is some lucky TCP session with some "windowlett" 
of two or four segments?

When I looked at Jasleens paper, all the OS discussed therein used the 
EWMA filters from RFC 2988.

Question: Where do these stem from?

Lucky guess? "Many" (i.e. > 10) experiments? Divine inspiration? Some 
verses of the bible? Or the Koran?

I don't know.

Are these natural constants?

Or are all networks created equal, endowed by their creator with some 
unalienable properties, that amongst these are the alpha and beta of the 
EWMA filters for SRTT and RTTVAR? (Or should I say: Life, Liberty and 
the pursuit of Happiness?)

Now, actually, the Internet works. And it works pretty fine. So, the 
recommendations by RFC 2988 can hardly be completely nonsense. However, 
can we give a set of assumptions / boundary conditions / ..., when 
thhese concepts do hold for sure?

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