Re: pfifo_fast behavior.

[dE <de.techno@gmail.com>]

On 05/12/13 19:33, dE wrote:
> Hello everyone!
>
> I was trying to do some traffic shaping to make http pages more 
> responsive while torrenting. So I decided to modify TOS value of 
> packets to have an affect on the default pfifo_fast qdisc.
>
> I've the following iptable rules --
>
> #DNS request
> iptables -t mangle -A OUTPUT -o eth1 -p udp -m multiport --dports 53 
> -j TOS --set-tos 0x10
>
> #DNS response
> iptables -t mangle -A PREROUTING -i eth1 -p udp -m multiport --sports 
> 53 -j TOS --set-tos 0x10
>
> #Incoming torrent connections
> iptables -t mangle -A PREROUTING -i eth1 -p tcp -m multiport --dports 
> 2000 -j TOS --set-tos 0x2
> iptables -t mangle -A PREROUTING -i eth1 -p udp -m multiport --dports 
> 2000,1900,2001 -j TOS --set-tos 0x2
>
> #Mail server
> iptables -t mangle -A OUTPUT -o eth1 -p tcp -d imap.googlemail.com -m 
> multiport --dports 993 -j TOS --set-tos 0x10
>
> #HTTP(S)
> iptables -t mangle -A OUTPUT -o eth1 -p tcp -m multiport --dports 
> 80,443 -j TOS --set-tos 0x14
> #iptables -t mangle -A OUTPUT -o eth1 -p tcp -m multiport --dports 
> 80,443 -j TOS --set-tos 0x10
> iptables -t mangle -A PREROUTING -i eth1 -p tcp -m multiport --sport 
> 80,443 -j TOS --set-tos 0x14
> #iptables -t mangle -A PREROUTING -i eth1 -p tcp -m multiport --sport 
> 80,443 -j TOS --set-tos 0x10
>
> There is an improvement, but it's so little that it feels like 
> placebo, making me doubt the above action. So are the actions correct?
>
> man tc-prio has a table --
>
> TOS     Bits  Means                    Linux Priority    Band
> ------------------------------------------------------------
> 0x0     0     Normal Service           0 Best Effort     1
> 0x2     1     Minimize Monetary Cost   1 Filler          2
> 0x4     2     Maximize Reliability     0 Best Effort     1
> 0x6     3     mmc+mr                   0 Best Effort     1
> 0x8     4     Maximize Throughput      2 Bulk            2
> 0xa     5     mmc+mt                   2 Bulk            2
> 0xc     6     mr+mt                    2 Bulk            2
> 0xe     7     mmc+mr+mt                2 Bulk            2
> 0x10    8     Minimize Delay           6 Interactive     0
> 0x12    9     mmc+md                   6 Interactive     0
> 0x14    10    mr+md                    6 Interactive     0
> 0x16    11    mmc+mr+md                6 Interactive     0
> 0x18    12    mt+md                    4 Int. Bulk       1
> 0x1a    13    mmc+mt+md                4 Int. Bulk       1
> 0x1c    14    mr+mt+md                 4 Int. Bulk       1
> 0x1e    15    mmc+mr+mt+md             4 Int. Bulk       1
>
> But is there a difference between all TOS values which fall in a 
> single band?
>
> I mean, does the behavior of pfifo_fast change if I change from 0x12 
> to 0x16? Cause I thought the qdisc to be simple, and a different 
> behavior for all of the above TOS values means pfifo_fast does a lot 
> more than just placing packets in 3 different queues.
>
> Another question -- how do you get these TOS values? and what does -j 
> TOS --set-tos <HEX/DEC> do? Does it modify the 4 bits or the whole 8 
> bit TOS value in the header, or does something completely different?
>
> I'm running a custom kernel with Gentoo OS.

Looks like this's long written and forgotten code.