[Asterisk-Users] QoS TOS numbers and Cisco IOS

[Rich Adamson]

> Does anyone know how setting the TOS bits in iax.conf corresponds to 
> the Cisco TOS types?
> 
> For example, if I set:
> 
> tos=0x04
> 
> in iax.conf, and on the Cisco, I use:
> 
> access-list 110 permit ip any any tos 4
> 
> I can't get the Cisco to match any packets.  I've tried various 
> combinations of numbers on both asterisk and the cisco.  I've also 
> tried hex to decimal conversion.  I just can't get the Cisco to see the 
> TOS bits that I set in iax.conf.

Here's what I'm using.

sip.conf:
tos=0x18  ;lowdelay     ;sets ip tos bits (=lowdelay, throughput)  
iax.conf:
tos=lowdelay

Cisco:
class-map match-all voice-rtp
  match access-group 103

access-list 103 permit ip any any tos min-delay
access-list 103 permit ip any any tos 12

C1750#show access-list 103
Extended IP access list 103
    permit ip any any tos min-delay (2077271 matches)
    permit ip any any tos 12 (651833 matches)

The NAI Sniffer does a better job of showing the bits. Here's two
samples for the above:

sip packet (tos=0x18):
      IP: Type of service = 18
      IP:       000. ....   = routine
      IP:       ...1 .... = low delay
      IP:       .... 1... = high throughput
      IP:       .... .0.. = normal reliability
      IP:       .... ..0. = ECT bit - transport protocol will ignore the CE bit
      IP:       .... ...0 = CE bit - no congestion

iax packet (tos=lowdelay):
      IP: Type of service = 10
      IP:       000. ....   = routine
      IP:       ...1 .... = low delay
      IP:       .... 0... = normal throughput
      IP:       .... .0.. = normal reliability
      IP:       .... ..0. = ECT bit - transport protocol will ignore the CE bit
      IP:       .... ...0 = CE bit - no congestion

Study the above and the bits become very clear. :)