[e2e] TCP "experiments"

Marco Mellia mellia at tlc.polito.it
Wed Jul 31 12:05:34 PDT 2013

> if someone is just making the sender side send faster no matter what the circumstance
> then you'd be right - but a lot of TCP changes make it more _efficient_ which benefits
> everyone - for example TCP Fast Open means less packets on the net, which is a 
> win-win scenario (lower latency for this user, less in the queues for other users)…


> so a lot of the things people at google and other places are trying to do
> are universally beneficial imho.....why would they not be?

If you want an example where a change would be not "fair", you can consider YouTube.
Now they start to use more than one TCP connection to serve the video.
This avoids that the application gets stuck because the TCP connection gets stuck.
In case of competing traffic (and congestion), YouTube client will download in parallel from multiple connections (we have seen up to 5).
Thus sharing capacity is not fair against other concurrent traffic.
You may say that Video is not best effort, so why not.
But in a scenario where you use YouTube and I use MyTube, you'll see, and I'll not see :(
You are more aggressive, and get a larger share of capacity.

Same for TCP initial window. You use 10, I use 2. You are more aggressive. I suffer from additional losses/delay because of you (in case we share the same link).

As said, weighting the pros against the cons is not easy.

Anyway, I found it funny that we can discuss this forever. But actually no one has the right/power/control of imposing anything on the Internet. 
Basically, it's a perfect anarchy, where everyone is allowed to do/deploy whatever he thinks it's good for him. 
I push more, I get more. I don't care if you get hurt…
Would be nice to have a system where some judge can say that you are pushing too much, and provide a punishment for you. But this seems quite impossible here…


> In missive <FFE1446C-A44E-40E8-BAF4-BFF44082BFEE at tlc.polito.it>, Marco Mellia typed:
>>> Jon,
>>> I think no one is saying that big companies are doing dumb things. It's =
>>> just that the Internet is a really shared infrastructure.
>>> Unless resources are infinite (which may be actually the case for Google =
>>> :)), gaining something somewhere comes at the expenses of loosing =
>>> something else somewhere else.
>>> Considering TCP, it is easy to show that "I can gain". It is much harder =
>>> to show "who else is loosing".
>>> And weighting the plus and the minus is even more complicated.
>>> M
>>> --=20
>>> Marco Mellia - Assistant Professor
>>> Dipartimento di Elettronica e Telecomunicazioni
>>> Politecnico di Torino
>>> Corso Duca Degli Abruzzi 24
>>> 10129 - Torino - IT
>>> Tel: +39-011-090-4173
>>> Cel: +39-331-6714789
>>> Skype: mgmellia
>>> Home page: http://www.tlc-networks.polito.it/mellia
>>> On Jul 30, 2013, at 1:34 AM, Jon Crowcroft <Jon.Crowcroft at cl.cam.ac.uk> =
>>> wrote:
>>>> the nice thing about a lot of the big cloud/web service outfits=20
>>>> is that they run a huge _range_ of applications so a point solution=20
>>>> tcp optimised for just one thing that=20
>>>> harmed the common case uses of TCP would be ruled out -=20
>>>> =20
>>>> if you think about the mix of map/reduce,=20
>>>> video streaming, social net, searches, gmail, gfs, google docs, etc =
>>> etc=20
>>>> (and similar mixes for microsoft bing + hotmail + azure etc;=20
>>>> and similar for apple iCloud, appstore, and similar for,
>>>> oh, i dunno, maybe even facebook),=20
>>>> then I doubt very much we'd see them do something
>>>> as narrowly dumb as people seem to imply here=20
>>>> (or deploy someone else's dumb narrow hack either)....
>>>> =20
>>>> as for impact between different cloud/web service providers
>>>> (e.g. google being smart enough to optimise a TCP hack for all that =
>>> stuff
>>>> but still harm Amazon's traffic for book/cd buying, EC2, cloud music =
>>> player
>>>> etc etc, that would be incredibly ingeneiously dumb,=20
>>>> but also unlikely, since a major google's revenue depends on=20
>>>> people finding stuff on _other servers,=20
>>>> and finding those other services useful,=20
>>>> so it would be kind of silly to auction advert space to the highest =
>>> bidder=20
>>>> iand deliver those adverts in a way that broke the advertised =
>>> things....
>>>> =20
>>>> [I suppose you could deliver adverts that broke TCP services to
>>>> servers that hadn't paid you to advertise them - that'd be pretty
>>>> super duper whacky type of cyberwarfare game some folks at the NSA
>>>> probably have fun thinking up.....
>>>> =20
>>>> maybe Huawei could deploy some DPI-based filter to harm succesful =
>>> businesses only
>>>> so as to bring down the whole capitalist imperialist western =
>>> civilisation....oh no,
>>>> wait, they need our net to work so they can sell us their routers...
>>>> =20
>>>> In missive <2EBB07CA-C011-4DC4-AACD-5A9D959C59D7 at isi.edu>, Joe Touch =
>>> typed:
>>>> =20
>>>>>> =20
>>>>>> =20
>>>>>> On Jul 29, 2013, at 11:14 PM, Jon Crowcroft =
>>> <Jon.Crowcroft at cl.cam.ac.uk> wro=3D
>>>>>> te:
>>>>>> =20
>>>>>>> google have extremely good instrumentation -
>>>>>> =20
>>>>>> They can now see how my PC talks to amazon.com now?
>>>>>> =20
>>>>>>> their shareholders would get upset if they deployed things that =
>>> broke
>>>>>>> the world badly -
>>>>>> =20
>>>>>> Even if they made Google 0.01% faster? And increased ad revenue as a =
>>> result?=3D
>>>>>> And stock value or dividends?
>>>>>> =20
>>>>>>> that's the NSA's job.
>>>>>> =20
>>>>>> Sound like you're referring to my first point above :-)
>>>>>> =20
>>>>>> Joe=3D20
>>>>>> =20
>>>> =20
>>>> cheers
>>>> =20
>>>>  jon
>>>> =20
> cheers
>   jon

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