QoS - key and nonkey fields

In the context of QoS and classification of traffic, a key field is a parameter or attribute used to categorize or classify network traffic. Examples of key fields include source and destination IP addresses, port numbers, protocol types, and more. These fields are used in match statements in class maps as well as flow records used with CPM to define the criteria for traffic classification.

Nonkey fields, on the other hand, are additional data points that provide further information about the traffic but are not used for classifying the traffic into different classes. When you use the collect command in a flow record for example, you can specify which nonkey fields to gather data on. These might include things like:

  • Packet lengths
  • Time stamps (to calculate flow duration)
  • TCP flags
  • Packet counts
  • Byte counts
  • Other flow-specific details that are not used for classification but are useful for monitoring and analysis purposes