On Fri., Apr 16, 2010, Michael SIERCHIO wrote:
>> Referring to the page '/firewall_shaper_edit.php', there are
>> several choices for 'IP Type of Service':
>> It seems that recent RFCs  have outdated the classical TOS
>> semantics used by the most recent M0n0wall release. I'm trying
>> to match DSCP class selector 5 (CS5) and am confused about the
>> mapping to the older TOS bits. A document  on such mapping
>> helps a little.
>Have you looked at actual traffic to see if these bits are being
>used according to the newer semantics?
Okay, now I've finally looked at the actual traffic and:
Yes the bits are being set according to my wishes (CS5/EF.)
After I verified that I can manipulate how they are set, I decoded
them according to both the DSCP RFC and the older TOS semantics.
CS5 is 101000 while EF is 101110:
*** CS5 *** *** EF ***
Precedence-bits Other-bits Precedence-bits Other-bits
101 000 101 110
The 'other-bits' correspond to 'lowdelay, throughput, ?' but it
is the 'precedence-bits' which best describe these traffic types.
Namely, precedence 101 describes the packet as 'CRITIC/ECP'.
This leads to the question:
Of the remaining bits 'reliability, mincost, congestion,'
which relate to the precedence-bits associated with DSCP
class selector 5 (namely 101 or CRITIC/ECP)?
>This information is useful for routing, esp. fragmented packets,
>but is of very little importance to controlling bandwidth
>utilization to and from your endpoint users.
One endpoint user is sending low priority FTP traffic while
another user is sending high priority RTP traffic. If I can
mark the traffic in question properly, then these DSCP markings
should indeed be useful for controlling bandwidth utilization in
the m0n0wall router. Do you agree?