Re: "mask" in tc commands

[Mariano Korman <mkorman@mat.upc.es>]

Hi, Khalid
> 
> hi,
> can anyone tell me what os the signification of the keyword "mask" in  tc commands
> and why it is there?

mask is used in different contexts and it has different meanings.

when you use "mask" in a dsmark qdisc, it has to do with the TOS byte.
You can read Almesberger's paper on Diffserv over Linux where it is all
explained. I give you here a brief summary. For every class in a dsmark
qdisc, you specify a "mask" and a "value". The formula is as follows:

TOS of packet when dequeued = (TOS of packet when enqueued * mask ) +
value

if you use "mask" in a filter, it has a completely different meaning.

Hope it helped

	Mariano Korman

> is there any thing to have with the tos byte?
> are all the values possible to set for the tos byte in Linux?
> please help
> and thanks tu everybody