1012 Configuring Data Center Bridging Features
Traffic is passed across stacking links using WDRR for all CoS queues. This
will affect the observed behavior of ETS on egress ports scheduling traffic
from over-subscribed stacking links.
The three supported traffic class groups support an industry standard
configuration such that one traffic class group offers lossless service (PFC
enabled using WRR); one traffic class group contains priorities which are best
effort (PFC disabled using WRR); and one traffic class group offers an
expedited service (utilizes strict priority). When auto configuration is
enabled on ports using ETS, the traffic classes are combined according to the
above. Internally, the DCBX TCG mapping is restricted to using three TCGs
regardless of the number of TCGs advertised by the configuration source,
with the strict priority traffic mapped onto TCG 2, lossless traffic mapped
onto TCG1, and all other traffic mapped onto TCG0.
For ETS to be operational in a manually configured environment, the
following minimum steps must be performed:
1
Configure the CoS queue to Traffic Class Group mapping for the egress
ports.
2
Enable the appropriate scheduling algorithm for each TCG.
3
Configure the weight percentage for each TCG.
Variation on the Example Configuration
This example configures three classes of traffic and utilizes the secondary
(ETS) scheduler only:
• Best effort traffic: CoS Queue 0 for untagged and VLAN tagged frames
with VPTs: 0, 1, and 2
• Lossless iSCSI: CoS Queue 1, VLAN tagged frames with VPT equal to 3
• Expedited Traffic: CoS Queue 2, VLAN tagged frames with VPTs: 4, 5, 6, 7
console(config-if-Te1/0/2)#classofservice dot1p-mapping 0 0
console(config-if-Te1/0/2)#classofservice dot1p-mapping 1 0
console(config-if-Te1/0/2)#classofservice dot1p-mapping 2 0
console(config-if-Te1/0/2)#classofservice dot1p-mapping 3 1
console(config-if-Te1/0/2)#classofservice dot1p-mapping 4 2
console(config-if-Te1/0/2)#classofservice dot1p-mapping 5 2
console(config-if-Te1/0/2)#classofservice dot1p-mapping 6 2
console(config-if-Te1/0/2)#classofservice dot1p-mapping 7 2
console(config-if-Te1/0/1)#classofservice traffic-class-group 0 0
console(config-if-Te1/0/1)#classofservice traffic-class-group 1 1