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From: Stef Coene <stef.coene@docum.org>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] tc keywords
Date: Fri, 01 Nov 2002 20:51:28 +0000	[thread overview]
Message-ID: <marc-lartc-103618395326419@msgid-missing> (raw)
In-Reply-To: <marc-lartc-103618194624180@msgid-missing>

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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  reply	other threads:[~2002-11-01 20:51 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-11-01 20:16 [LARTC] tc keywords Daniel Corbe
2002-11-01 20:51 ` Stef Coene [this message]
2002-11-02  0:24 ` Kenneth Porter
2002-11-02  9:02 ` Stef Coene

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