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

From: Stef Coene <stef.coene@docum.org>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] few doubts about the working of tc
Date: Thu, 03 Jan 1980 23:15:45 +0000	[thread overview]
Message-ID: <marc-lartc-101716550824091@msgid-missing> (raw)

On Tuesday 26 March 2002 18:01, Akarapu Mahesh wrote:
> 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??
I don't know what happens if you use the change command. :(. It will change 
the bandwidth, but I don't know what happens with the queue.

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

Stef

-- 

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