Traffic priority

[Tanmoy]

Hi Connection,

Kindly understand me the difference between COS & TOS...class of service and type of service

both can play the same game or something else...

[mkazam001]

ToS = Type of Service. This is a byte in the IPv4 header which is used for Precedence, or in other words categorizing traffic classes (eg. precedence 0 = routine traffic, 5 = critical).

In the more modern form, the ToS is used for DSCP (works at L3). This is one of the tools available for QoS implementation.

CoS = Class of Service. This is a field in the ethernet header, also for categorizing traffic (0-7), CoS works at L2.

Regards, mk

please rate if helpful :)

[Tanmoy]

Hi MK,

Thanks u are saying that QOS is deciding factor of traffic precedence then can this same to be applied in shaping as well as policing....what is the difference between shaper rate & Policer??

[mkazam001]

There's a lot to consider when it comes to QoS to be honest.

Please see link below - explains difference between shaper & policer:

https://www.cisco.com/c/en/us/support/docs/quality-of-service-qos/qos-policing/19645-policevsshape.html

Regards, mk

please rate if helpful :)

[Joseph W. Doherty]

Belated response . . .

They both can play the same game. The big differences are CoS usually refers to the 3 bit priority in VLAN tags, while the L3 ToS is an 8 bit field. In earlier standards, the L3 ToS, like the L2 CoS, only provided 3 bits for priority (other bits had other QoS meanings). In the later standards, the ToS was "re-allocated", and it now has 6 bits that can be used for a QoS tag, with the DSCP, EF and less-than-BE standards, suggesting how to use those 6 bits.