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Chapter 5 – Configuring Class of Service
Chapter 5 – Configuring Class of Service
Introduction to CoS
This chapter familiarizes the user with using the Class of Service feature.
CoS Features
RuggedSwitch™ CoS provide you with the following features:
• Ability to prioritize traffic statically by port.
• Ability to prioritize traffic by the priority field in 802.1p and 802.1q tags.
• Ability to prioritize traffic based on its source or destination MAC address.
• Ability to prioritize traffic by the TOS field in the IP header.
• Ability to set the 802.1Q access priority from an established CoS.
CoS Concepts And Issues
CoS Operation
CoS provides the ability to expedite the transmission of certain frames and port
traffic over others. The CoS of a frame can take on one of two values, either
normal or high. The default policies of the switch enforce a normal CoS for all
traffic.
Note that CoS is only used internally by the switch, but may be conveyed
externally by mapping the CoS to the priority field in the 802.1Q tags of outgoing
frames.
The CoS feature has two main phases, inspection and forwarding.
Inspection Phase
In the inspection phase the CoS priority of a received frame is determined from:
• The priority field in 802.1P and 802.1Q tags
• The Differentiated Services Code Point (DSCP) component of the Type Of
Service (TOS) field, if the frame is IP.
• The default CoS for the port.
• A specific CoS based upon the source and destination MAC address (as set
in the Configure Static MAC Address Table menu).
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