Re: [LARTC] Help with PRIO qdisc and filters

[Andy Furniss <andy.furniss@dsl.pipex.com>]

Pavan Kumar wrote:
> Hi,
> Sorry to bother you all. I have a typical problem sharing DSL upstream
> bandwidth with users. I have 3 types of traffic high-priority,
> medium-priority and low priority. My upstream rate is 960kbits. Traffic (any
> priority) can vary in bandwidth from 0 to 960kbits. I have a test setup
> where I can pump 600kbit of high priority sustained and I have 400kbit of
> low priority traffic sustained. I expect after the 600kbit high-priority
> traffic, the remaining 360kbit should be allocated to the medium and low
> priority. Since I do not have medium-priority everything should go to
> low-priority traffic. However, I do not see that behavior with the following
> tc script I have
>  
> ----------- Begin Script -------------
> # delete any existing qdiscs
> tc qdisc del dev ppp0 root
> # setup PRIO qdisc with 3 bands
> tc qdisc add dev ppp0 root handle 1: prio band 3 priomap 0 0 0 0 0 0 0 0 0 0
> 0 0 0 0 0 0
> # filter traffic for high priority based on TOS field
> tc filter add dev ppp0 parent 1:0 prio 1 protocol ip u32 match ip tos 0x28
> 0xff flowid 1:1
> tc filter add dev ppp0 parent 1:0 prio 1 protocol ip u32 match ip tos 0x48
> 0xff flowid 1:2
> tc filter add dev ppp0 parent 1:0 prio 1 protocol ip u32 match ip tos 0x58
> 0xff  flowid 1:3
>  
> # use ebtables to set the TOS field. First flush the rules
> ebtables -t broute -F
> ebtables -t broute -I BROUTING 1 -j ftos --set-ftos 0x28 -p IPv4 --ip-src
> 192.168.1.151/32
> ebtables -t broute -I BROUTING 2 -j ftos --set-ftos 0x48 -p IPv4 --ip-src
> 192.168.1.152/32
> ebtables -t broute -I BROUTING 3 -j ftos --set-ftos 0x58 -p IPv4 --ip-src
> 192.168.1.153/32
>  
> ----------- End Script ------------------
>  
> What I see is the high priority traffic is leaving at 600kbits as I measure
> it on my test equipment. However, I do not see any low-priority or
> medium-priority traffic coming out of the box. I would appreciate if you
> folks can please give me a hint as to what is happening and also any
> possible solutions. I need hard PRIO but the unused bandwidth should be
> shared by the other traffic. I am using Linux kernel 2.6.8.1 and iproute2
> (iproute2-2.6.8-ss040730.tar.gz).

You need to have prio as an htb class as it doesn't rate limit otherwise .

You'll also need to back off from your dsl rate to allow for overheads 
as they can be significant especially with lots of small packets.

Andy.

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