VoIP QoS with TOS>63 ?

RouterOS General
1

I need to start using some QoS for VoIP calls.
However it seems firewall mangle only accepts TOS values between 0 and 63 but I have Linksys devices that have default TOS=0x68 (decimal 104) and TOS=0xb8 (dec 184) and my Asterisk boxes use 0xef (dec 239) as default to name but a few. What gives?
I really do not want to reconfigure all my client devices to implement QoS based on TOS values. :open_mouth:

Or am I missing the pot entirely here?

Thanks
Ekkas

2

I don’t see how that can be, unless I’m really missing something here.

DSCP uses the lower 6 bits of the ToS byte, which means values between 0 and 63. The last two bits are for ECN (explicit congestion notification) and shouldn’t be used for anything else.

3

Just found this:
http://wiki.slfree.net/index.php/QoS_for_VOIP_in_Mikrotik

Does it seem correct to divide the values by 4?
I’m going to try it and see if my packets get ‘discovered’…

4

After some googling that looks right.

It depends on whether or not the software looks at the value as an 8 byte value (the entire TOS byte), or just the six bits used for DSCP. To convert between the two you multiply by four (to go from 2^6 to 2^8). RouterOS looks at things as a 6 byte field, whatever Linksys equipment you have as well as the Asterisk server look at it as an 8 byte field.

5

Seems to be working for 0xb8 (dec/8= 46) but not for 0xef (dec/8=59) but then again, 184(0xb8) is divisible by 4 but 239(0xef) not, don’t know if that’s an issue.
Ekkas