Re: [LARTC] few doubts about the working of tc

From: "Akarapu Mahesh" <mahesh_a6@hotmail.com>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] few doubts about the working of tc
Date: Tue, 26 Mar 2002 17:01:11 +0000	[thread overview]
Message-ID: <marc-lartc-101716216919440@msgid-missing> (raw)
In-Reply-To: <marc-lartc-101716550824091@msgid-missing>

HI stef,
The following is the test scenario i am using.

A--->B--->C

First let me explain what i am doing here. I want to rate limit the traffic 
between A and B dynamically. I am doing this on A using "tc". All these 
machines have redhat 7.1 and A has 2.2.13 kernel with diffserv patch and B 
and C have 2.4.3 kernels.The following is the script that i am using.

1)tc qdisc del dev eth1 root
2)tc qdisc add dev eth1 root handle 1: cbq bandwidth 100Mbit cell 8 avpkt 
1000 mpu 64
3)tc class add dev eth1 parent 1:0 classid 1:1 cbq bandwidth 100Mbit rate 
100Mbit allot 1514 cell 8 weight 10Mbit prio 8 maxburst 20 avpkt 1000
4)tc class add dev eth1 parent 1:1 classid 1:2 cbq bandwidth 100Mbit rate 
60Mbit allot 1514 cell 8 weight 6Mbit prio 3 maxburst 20 avpkt 1000 bounded
5)sudo tc class add dev eth1 parent 1:1 classid 1:3 cbq bandwidth 100Mbit 
rate 40Mbit allot 1514 cell 8 weight 4Mbit prio 7 maxburst 20 avpkt 1000 
bounded
6)tc filter add dev eth1 parent 1:0 protocol ip prio 1 u32 match ip dst 
192.168.123.5 flowid 1:2

SInce i want to limit only the traffic between A and C i created only one 
filter for class 1:2. NOw i am changing the bandwidth limit using the 
following command. In the above 192.168.123.5 is the address of C.

7)tc class change dev eth1 parent 1:1 classid 1:2 cbq bandwidth 100Mbit rate 
60Mbit allot 1514 cell 8 weight 6Mbit prio 3 maxburst 20 avpkt 1000 bounded

Now let me tell my doubts.

1)Now suppose the bandwidth limit of A-->C traffic is changed from 60Mbps to 
20Mbps during a transfer, how does tc react to it?? Does it send the packets 
remaining in the queue at 60Mbps or 20Mbps or does it drop all the packets 
before changing the limit to 20Mbps??

2) Can i run the same script on B to limit the taffic between A and C??

thanks
mahesh

>From: Stef Coene <stef.coene@docum.org>
>To: "Akarapu Mahesh" <mahesh_a6@hotmail.com>, lartc@mailman.ds9a.nl
>Subject: Re: [LARTC] few doubts about the working of tc
>Date: Mon, 25 Mar 2002 18:51:33 +0100
>
>On Monday 25 March 2002 17:14, Akarapu Mahesh wrote:
> > HI,
> > I am new to tc. I have a few basic doubts about the working of tc.I am
> > trying to limit the bandwidth between two linux machines to 12Mbps. I am
> > using the route filter to achieve this. I tested with ttcp traffic 
>between
> > these machines. I used tcpdump cature the data during this transfer and
> > observed this using tcptrace. I find that the throuhgput was much higher
> > than 12Mbp sometimes during the transfer. But the avg throughput for the
> > whole transfer was 12Mbps. NOw my doubt is how tc is going to limit the
> > bandwidth?? Please let me know how exactly tc limits the bandwidth.
>How do you made your setup ?  CBQ or HTB? classes, qdiscs, filters ?
>More info plz.
>
>Stef
>
>--
>
>stef.coene@docum.org
>  "Using Linux as bandwidth manager"
>      http://www.docum.org/
>      #lartc @ irc.openprojects.net

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