Quality of Service (QoS) Classification and Marking Notes
The first part of building a QoS policy is to identify the traffic that you need to treat preferentially (give better priority), or differentially. This is accomplished via classification and marking.
- Classification – sorts packets into different traffic types that policies can then be applied to.
- Marking (or re-marking) – establishes a trust boundary on which scheduling tools later utilize. The edge of the network where markings are either accepted or rejected is known as the trust-boundary.
- Classifier tools – Inspect one or more fields in a packet to identify the type of traffic that is being carried. After being identified, it is passed to the appropriate mechanism to handle that type of traffic class.
- Marking tools – actually write a field within the packet (or frame, cell, label) to preserve the classification decision. By marking traffic at a trust boundary, subsequent nodes do not have to perform the same in-depth analysis to determine how to treat the packet.
Classification Tools
These tools can examine a number of criteria within layers 1, 2, 3, 4, and 7.
- L1 – Physical interface, subinterface, PVC, port
- L2 – MAC, 802.1Q/p CoS, VLAN, MPLS EXP, ATM Cell Continue reading
