QOS marking matrix

[Ratheesh mv]

Hi all,

Can anyone please explain the difference between  following QOS marking matrix?

1)QOS group.

2)Discard-calss

3)Traffic-class.

I noticed that somewhere QOS group is used and in some other examples discard-class or traffic-class are used. I am not able to properly understand the differences and circumstances. 

Thanks in advance.

[marce1000 · Accepted solution]

                              Here are the definitions of the three terms you mentioned:

1. QOS Group: A QOS Group is a set of network traffic flows that have similar QOS requirements. For example, a QOS group might be defined for VoIP traffic, which requires low latency and high bandwidth, or for file transfer traffic, which might require high bandwidth but is less sensitive to latency.

2. Discard Class: Discard Class is a classification of network traffic that determines how the network will handle traffic that exceeds the available network resources. The discard class specifies which traffic will be dropped first in the event of network congestion.

3. Traffic Class: Traffic Class is a classification of network traffic that determines the priority with which the traffic will be handled by the network. Different traffic classes may have different QOS requirements, and the network may prioritize traffic based on the traffic class to ensure that the most critical traffic receives the necessary QOS.

In summary, QOS Group defines a set of traffic flows with similar QOS requirements, Discard Class determines how the network will handle traffic that exceeds the available network resources, and Traffic Class determines the priority with which the traffic will be handled by the network based on its QOS requirements.

 M.

[Joseph W. Doherty]

QoS group is a Cisco feature which can lump together traffic, based on your criteria, for specific QoS treatment.  Basically, it's much like a ToS marking but it's only local to the device.

Discard class is another Cisco feature, much like QoS group including being only known within the device.  Basically it's provided to allow you to set discard values in conjunction with QoS group.  Consider QoS group, conceptionally, much like DSCP AF classes (1..4) and the discard class much like DSCP AF classes drop marking (1..3).  Unlike DSCP AF, QoS group and discard class offer more values. QoS group, 0..99 and and discard class, 0..7.

Logically a traffic-class is a set of traffic that is treated alike, for QoS purposes, includes possibly having different drop probabilities within that class.  For example, a traffic-class generally maps into a single CBWFQ class.  Usually, one or more DSCP markings might map to a QoS traffic-class, ditto if using QoS groups, although since QoS groups are local to the device, unlikely you would have multiple QoS groups mapping into the same traffic-class.

QoS command-line documentation mentioning both QoS group and discard-class.