Dynamic Mode Cos For Vlan Stacking - Dell Force10 Z9000 Configuration Manual

Example of Viewing DEI-Marking Configuration
To display the DEI-marking configuration, use the show interface dei-mark [interface slot/port | linecard
number port-set number] in EXEC Privilege mode.
Dell#show interface dei-mark
Default CFI/DEI Marking: 0
Interface Drop precedence CFI/DEI
--------------------------------
Te 1/1 Green
Te 1/1 Yellow
Te 2/9 Yellow
Te 2/10 Yellow

Dynamic Mode CoS for VLAN Stacking

One of the ways to ensure quality of service for customer VLAN-tagged frames is to use the 802.1p priority bits in the tag to indicate
the level of QoS desired.
When an S-Tag is added to incoming customer frames, the 802.1p bits on the S-Tag may be configured statically for each customer
or derived from the C-Tag using Dynamic Mode CoS. Dynamic Mode CoS maps the C-Tag 802.1p value to a S-Tag 802.1p value.
Figure 103. Statically and Dynamically Assigned dot1p for VLAN Stacking
When configuring Dynamic Mode CoS, you have two options:
• Mark the S-Tag dot1p and queue the frame according to the original C-Tag dot1p. In this case, you must have other dot1p QoS
configurations; this option is classic dot1p marking.
• Mark the S-Tag dot1p and queue the frame according to the S-Tag dot1p. For example, if frames with C-Tag dot1p values 0, 6,
and 7 are mapped to an S-Tag dot1p value 0, all such frames are sent to the queue associated with the S-Tag 802.1p value 0. This
option requires two different CAM entries, each in a different Layer 2 ACL FP block.
NOTE: The ability to map incoming C-Tag dot1p to any S-Tag dot1p requires installing up to eight entries in the Layer 2
QoS and Layer 2 ACL table for each configured customer VLAN. The scalability of this feature is limited by the impact of
the 1:8 expansion in these content addressable memory (CAM) tables.
Dell Networking OS Behavior: For Option A shown in the previous illustration, when there is a conflict between the queue selected
by Dynamic Mode CoS (vlan-stack dot1p-mapping) and a QoS configuration, the queue selected by Dynamic Mode CoS takes
precedence. However, rate policing for the queue is determined by QoS configuration. For example, the following access-port
configuration maps all traffic to Queue 0:
vlan-stack dot1p-mapping c-tag-dot1p 0-7 sp-tag-dot1p 1
However, if the following QoS configuration also exists on the interface, traffic is queued to Queue 0 but is policed at 40Mbps (qos-
policy-input for queue 3) because class-map "a" of Queue 3 also matches the traffic. This is an expected behavior.
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