Is CoS the same as IP Precedence? 1

[tbitner]

Hello, From my understanding of QoS for voice traffic, the TOS/Diffserv should be 46 and precedence 5.

My question is, I have a device that list the correct TOS/Diffserv, but then has COS value 6. Is COS the same as IP Precedence? If so, shouldn't the COS value be 5?

Here's the weird thing. If I setup a class-map on my router to match IP precedence 5, this above traffic matches. How does COS 6 convert in bits into Precedence 5?

Thanks,
Todd

 

[unclerico]

CoS is layer 2 info while ToS is layer 3. CoS is 802.1p, ToS can be DiffServ or IP Precedence. Both CoS and IP Precedence use only 3 bits (possible values of 0 - 7) while DiffServ uses all 8 bits of the ToS byte (really it only uses 6) (possible values 0 - 63). A lot of voice solutions mark traffic with a CoS value of 6 out of the box.

I hate all Uppercase... I don't want my groups to seem angry at me all the time! =)
- ColdFlame (vbscript forum)

 

[tbitner]

ok, that makes sense. The device's value of COS = 6 is referring to IP Precedence of 6 (Internet). It just strikes me as odd that this voip device has Diffserv = 46 but COS = 6 when I thought it should be 5.

Thanks!