netdev
[Top] [All Lists]

Re: looking for info about struct tcp_opt

To: Karl Jonas <karl.jonas@xxxxxxxxxxxx>
Subject: Re: looking for info about struct tcp_opt
From: Andi Kleen <ak@xxxxxx>
Date: Fri, 5 Jan 2001 15:08:49 +0100
Cc: netdev@xxxxxxxxxxx
In-reply-to: <3A55CF54.8C890679@xxxxxxxxxxxx>; from Karl Jonas on Fri, Jan 05, 2001 at 02:35:54PM +0100
References: <3A55CF54.8C890679@xxxxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx
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

<Prev in Thread] Current Thread [Next in Thread>