QoS requirements and recommendations for data traffic:
Best Effort
- Traffic should be marked to DSCP 0.
- Adequate bandwidth should be assigned to this class because majority of applications default to this class. Recommended is to set aside 25 percent for this class.
Bulk
- Traffic should be marked to DSCP AF11; excess traffic can be marked down by a policer to AF12 or AF13.
- Traffic should have a moderate bandwidth guarantee but should be constrained from dominating a link.
Transactional or Interactive
- Traffic should be marked to DSCP AF21; excess traffic can be marked down by a policer to AF22 or AF23.
- Traffic should have an adequate bandwidth guarantee for the interactive, foreground operations that it supports.
Mission Critical
- Traffic should be marked to DSCP AF31; excess traffic can be marked down by a policer to AF32 or AF33.
- Traffic should have an adequate bandwidth guarantee for the interactive, foreground operations that it supports.
QoS requirements and recommendations for control plane:
Network Management
- Traffic should be marked to DSCP CS2.
- Network Management applications should be protected explicitly with a minimal bandwidth guarantee.
Scavenger
- Traffic should be marked to DSCP CS1.
- Traffic should be assigned the lowest configurable queuing service; for instance, in Cisco IOS, this means assigning a CBWFQ of 1 percent.
References
Cisco QoS Exam Certification Guide (IP Telephony Self-Study) (2nd Edition)
End-to-End QoS Network Design: Quality of Service in LANs, WANs, and VPNs
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