Re: [PATCH] tcp: Implement a two-level initial RTO as per draft RFC2988bis-02.

From: Alexander Zimmermann
Date: Thu May 19 2011 - 12:56:12 EST

Am 19.05.2011 um 18:40 schrieb tsuna:

> On Thu, May 19, 2011 at 1:02 AM, Hagen Paul Pfeifer <hagen@xxxxxxxx> wrote:
>> So yes, it CAN be wise to choose other lower/upper bounds. But keep in
>> mind that we should NOT artificial limit ourself. I can image data center
>> scenarios where a initial RTO of <1 match perfectly.
> Yes that's exactly the point I was trying to make when talking to
> Alexander offline. On today's Internet, RTTs are easily in the
> hundreds of ms, and initRTO is 3s, so there's 2 orders of magnitude of
> difference. In my environment,

Exactly. This is the point. It's *your* environment. However, TCP is
general purpose. And for the wider internet 1s is know to be save. See the
measurements in the draft that Mark Allman run.

> if my RTT is ~2µs, an initRTO of 200ms
> means that there's a gap of 6 orders of magnitude (!).

Currently, initRTO is 3s. So you the gap is even larger.

> And yes,
> although I don't work for High Frequency Trading companies in Wall
> Street, I'm already buying switches full of line-rate 10Gb ports with
> a port-to-port latency of 500ns for L2/L3 forwarding/switching. I
> expect this kind of network gear will quickly become prevalent in
> datacenter/backend environments.
> --
> Benoit "tsuna" Sigoure
> Software Engineer @

// Dipl.-Inform. Alexander Zimmermann
// Department of Computer Science, Informatik 4
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