Classification Tools | Network Quality of Service Technologies

Classification tools serve to identify traffic flows so that specific QoS policies can be applied to specific flows, such as TelePresence media and control flows. Often the termsclassification and marking are used interchangeably (yet incorrectly so); therefore, you need to understand the distinction between classification and marking operations:

• Classification refers to the inspection of one or more fields in a packet (the term packet is used loosely here to include all Layer 2 to Layer 7 fields, not just Layer 3 fields) to identify the type of traffic that the packet is carrying. When identified, the traffic is directed to the applicable policy-enforcement mechanism for that traffic type, where it receives predefined treatment (either preferential or deferential). Such treatment can include marking/remarking, queuing, policing, shaping, or any combination of these (and other) actions.
• Marking, on the other hand, refers to changing a field within the packet to preserve the classification decision that was reached. When a packet has been marked, a trust boundary is established, upon which other QoS tools later depend. Marking is only necessary at the trust boundaries of the network and (as with all other QoS policy actions) cannot be performed without classification. By marking traffic at the trust boundary edge, subsequent nodes do not have to perform the same in-depth classification and analyses to determine how to treat the packet.

MQC performs classification based on the logic defined within the class map structure. Such logic can include matching criteria at the data link, network, or transport Layer (Layers 2 to 4) or even at the application layer (Layer 7)