Understanding of "mask"

[Luigi Rizzo]

On Tue, Nov 23, 2010 at 02:19:02PM +0000, nangergong wrote:
> Hi, all,
> 
>   I don't understand the meaning of "mask",
>   for example, in the following statements:
> --------------------------------------
>   ipfw pipe 1 config delay 80ms mask all
>   ipfw add 600 pipe 1 ip from 9.161.150.55 to 9.161.148.72
> ----------------------------------------
> 
> What is the usage of  "mask all"?
> I think in total there is only 1 queue, so "mask all" here doesn't make any

mask tells ipfw to create as many actual pipes (and queues) as
there are different values of the 5-tuple after masking.
E.g. for a pipe with bw limitations (say bw 100Kbit/s)
each flow would get its own 100Kbit/s without interference
from the others.

In this case the mask is useless because the pipe has only
delay so there would be no interference anyways.

cheers
luigi