[LARTC] tc keywords

[LARTC] tc keywords

[Daniel Corbe]

Could someone clue me in as to what exactly the following tc keywords do:

allot
cell
weight
maxburst
avpkt

Thanks,
Daniel
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Re: [LARTC] tc keywords

[Stef Coene]

On Friday 01 November 2002 21:16, Daniel Corbe wrote:
> Could someone clue me in as to what exactly the following tc keywords do:
This are not tc keywords, but are cbq keywords.
I have some of them explained on www.docum.org 
http://www.docum.org/stef.coene/qos/docs/qdisc.html

> allot
> cell
> weight
> maxburst
> avpkt

Bandwidth is the maximum bandwidth of the device where the queue is attached. 
This can be a NIC or a class from another qdisc. For a root-qdisc, the 
bandwidth has to be the same as the bandwidth of the device where it's 
attached to and not the link bandwidth. All QOS-elements with the same major 
number, has to have the same bandwidth.

avpkt is average packet size. Used to determine transmission time : 
transmission time = avpkt/link-bandwidth. You have to lower this for 
real-time traffic since they use smaller packets (usual <400).

mpu is minimal packet size. For ethernet-like devices this is 64. Packets 
smaller then MPU will be resetted to MPU. Typical MTU = 64.

allot is MTU + MAC header (parameter used by the link sharing scheduler)
Allot is always more then avpk*3/2. From tc-source:

if (allot < (avpkt*3)/2)
   allot = (avpkt*3)/2;

minburst is the number of bytes that will be transmitted in the shortest 
burst.

maxburst measure allowed class burstiness (please, read S.Floyd and VJ papers) 
: this is the maximum of bytes that will be transmitted in the longest burst.

est 1sec 8sec means, that kernel will evaluate average rate on this class with 
period 1sec and time constant 8sec. This rate is viewed with "tc -s class ls 
dev $DEVICE"

weight should be set proportional to rate. You can use this to divide the 
traffic in the different classes. (more info about splitting) The weight 
determines the number of bytes that a class is allowed to send in a 
scheduling round.

A cell value of 8 means that the packet transmission time will be measured in 
terms of 8 bytes.


Stef

-- 

stef.coene@docum.org
 "Using Linux as bandwidth manager"
     http://www.docum.org/
     #lartc @ irc.oftc.net

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Re: [LARTC] tc keywords

[Kenneth Porter]

--On Friday, November 01, 2002 09:51:28 PM +0100 Stef Coene 
<stef.coene@docum.org> wrote:

> Bandwidth is the maximum bandwidth of the device where the queue is
> attached.  This can be a NIC or a class from another qdisc. For a
> root-qdisc, the  bandwidth has to be the same as the bandwidth of the
> device where it's  attached to and not the link bandwidth. All
> QOS-elements with the same major  number, has to have the same bandwidth.

I was a little confused by this. I have a 100 Mbps NIC, but it's connected 
to a switch that throttles my allocation down to 4 Mbps. So which number do 
I use for the root CBQ bandwidth?

I'm using the WonderShaper, and it looks like it uses the NIC's speed, not 
the upstream cap. Is that correct, or a bug in the script?
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Re: [LARTC] tc keywords

[Stef Coene]

On Saturday 02 November 2002 01:24, Kenneth Porter wrote:
> --On Friday, November 01, 2002 09:51:28 PM +0100 Stef Coene
>
> <stef.coene@docum.org> wrote:
> > Bandwidth is the maximum bandwidth of the device where the queue is
> > attached.  This can be a NIC or a class from another qdisc. For a
> > root-qdisc, the  bandwidth has to be the same as the bandwidth of the
> > device where it's  attached to and not the link bandwidth. All
> > QOS-elements with the same major  number, has to have the same bandwidth.
>
> I was a little confused by this. I have a 100 Mbps NIC, but it's connected
> to a switch that throttles my allocation down to 4 Mbps. So which number do
> I use for the root CBQ bandwidth?
100Mbit.
After that, add a bounded class of 4mbit to the root qdisc.  Add all other 
class to this bounded class.

> I'm using the WonderShaper, and it looks like it uses the NIC's speed, not
> the upstream cap. Is that correct, or a bug in the script?
It's correct.

Stef

-- 

stef.coene@docum.org
 "Using Linux as bandwidth manager"
     http://www.docum.org/
     #lartc @ irc.oftc.net

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