[e2e] Google seeks to tweak TCP

Detlef Bosau detlef.bosau at web.de
Mon Feb 6 06:51:12 PST 2012

On 02/03/2012 07:36 PM, Daniel Havey wrote:
> Hmmm, not really.  If a service provider drops non-TCP packets then my TCP alternative will never have a chance to get off the ground.  I could build it, but, what is the point if nobody will use it?
> I believe that any new solution must not only play nice with TCP, but be indistinguishable from TCP.  Otherwise the packets may be dropped.

However, this is implementation and development and not primarily research.

>> And whenever people are exited by simple recipes which save
>> the world, we always should keep in mind RFC 1925.
>>>      (6)  It is easier to move a problem around (for example, by moving the problem to a different part of the overall network architecture) than it is to solve it.
> This is getting interesting.  So the goal of Cubic (from the paper) is to provide more RTT fairness.  It does this.

Oh, I should better not look at the Cubic paper. Why shall we pursue 
"RTT fairness"? Particularly, when wireless networks are included, this 
is no longer RTT fairness but fate sharing instead.

> I don't think that queuing delay is the only cause of large RTTs.  Sometimes a link is just slow and sketchy.  Happens all the time.  maybe 802.11n has negotiated a slow rate or there are lots of retransmissions.  There will probably be a lot of packets in the queue because of this, but, the link is slow and that is why the RTTs are large.  I'm thinking of projects like "Wireless Africa" where links are slow and lossy.

According to my experience, it is difficult to sell lossy links in 
papers. However, being lossy and being slow are often just two sides of 
the same mountain.

> Such links have difficulty even reaching their tiny capacity with Reno.  They do much better with Cubic.

What's the very reason for this behaviour? Is it because Reno cannot 
deal well with losses?

Detlef Bosau
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