Quality of Service Classification

Classification of packets is part of a Quality of Service mechanism that distinguishes between different traffic streams. Traffic descriptors categorise an IP packet to a specific class.

Classifying packets should take place at the network edge as close to the source of the traffic as possible.

Once the packet has been classified, it can be marked, queued, policed, shaped or a combination of these.

There are number of different traffic descriptors that can used for classification, commonly Layer 2, 3, 4 and 7 are used:

  • Internal: Quality of Service Groups that locally significant to a router
  • Layer 7:
    • Next generation network-based application recognition (NBAR2)
  • Layer 4:
    • TCP or UDP ports
  • Layer 3:
    • Differentiated Services Code Points (DSCP),
    • IP Precedence (IPP),
    • Source or destination IP address:
  • Layer 2
    • MAC address
    • 802.1Q/p Class of Service bits
  • Layer 1
    • Physical Interface
    • Subinterface
    • Physical Port



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