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From:   Andi Kleen <ak@muc.de>
To:     Karl Jonas <karl.jonas@ccrle.nec.de>
Cc:     netdev@oss.sgi.com
Subject: Re: looking for info about struct tcp_opt
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In-Reply-To: <3A55CF54.8C890679@ccrle.nec.de>; from Karl Jonas on Fri, Jan 05, 2001 at 02:35:54PM +0100
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On Fri, Jan 05, 2001 at 02:35:54PM +0100, Karl Jonas wrote:
> WHAT IS THE UNIT OF SRTT?
> According to its declaration in sock.h, it is the 'smoothed rtt << 3' .
> Does this mean, that the value '8', which i observed, corresponds to a 
> round trip time of about 1 ms ?

In the linux kernel time is usually counted in jiffies (=timer interrupts),
on i386 that's 10ms, e.g. on alpha it is ~1ms.

Unit is jiffies<<3.

> 
> WHAT IS THE UNIT OF SND_CWND?
> In my trace, snd_cwnd initialises with 3 and increases by 1 for each
> packet
> sent (acked?), and slower after, corresponding perfectly to slow start / 

acked
> congestion avoidance. But what is the real size of the congestion window
> (maybe snd_cwnd * mss ?)  ?

It's packets. 2.4 switched to counting it in bytes, because the packet counting
has some problems.

factor is *average of your packet size.

> 
> WHAT IS THE RTO UNIT?
> I see a rto of 20. This seems to be quite short if it was 20 ms. Does
> linux
> count in 10's of ms here?

Yes, in jiffies.


-Andi