Re: NAT, MANGLE, and TOS

[Jeffrey Laramie <JALaramie@Loudoun-Fairfax.com>]

SBlaze wrote:

>Currently I run a very and common setup for my home network.
>
>My Linux box acts as my router and gateway for my home network and simply NATs
>everything out to the cable modem and onto the internet.
>
>My question is this. I have read awhile ago that changing the TOS of packets
>can be beneficial in ganing small performance. Logically I thought this would
>pretty much be limited to a Point to Point systems. However by posting to some
>forums for broadband, i hearf through the perverbial grapevine that my
>ISP(Charter Communications) will honor user or application set TOS values
>unless they are under network congestion. I can of course not verify this.
>
>This is my quandry. Currently this is all I do..
>
>iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to 68.119.49.97
>
>Is it possible to mangle NAT in a way that all my nat traffic carries slightly
>higher TOS values? Will this give me a slight to any boost in upstream?
>
>As always thanks for any info in advance and hail to the open source community.
>SBlaze
>  
>
You can use the appropriately named mangle table to set TOS like this:

$iptables -t mangle -A OUTPUT -p tcp -m state --state 
NEW,RELATED,ESTABLISHED -m tcp --sport 80 -j TOS --set-tos 0x08

I don't have enough traffic on my network to see a noticeable difference 
when I change TOS, but given your situation, setting TOS might help.

Jeff