Brocade Multi-Service IronWare QoS and Traffic Management Configuration Guide (Supporting R05.6.00) - Manual (Page 87)

Multi-Service IronWare QoS and Traffic Management Configuration Guide 73
53-1003037-02
Ingress Traffic processing through a device
4
7. Merge or force the priority value based on an ACL look-up. This is used for setting a a specific
priority for and L2, L3 or L4 traffic flow.
This process is described in Figure 2 .
FIGURE 2 Logic flow of Ingress QoS processing
Recognizing inbound packet priorities and mapping
to internal priority
The processes performed in the first block of Figure 2 can be described in two stages as described
in the following:
Stage 1
Collect priority and drop precedence information from various portions of the
packet header
• If a packet’s EtherType matches 8100 or the port’s EtherType, derive a priority value and drop
precedence by decoding the PCP value.
• If the qos use-dei command is configured, the bit between the VLAN ID and PCP in the VLAN
tag will be interpreted as a drop precedence and priority value.
• For MPLS packets, derive a priority value and drop precedence by decoding the EXP bits.
• For IPv4 or v6 packets, derive a priority value and drop precedence by decoding the DSCP bits.
• The derived values for PCP, EXP and DSCP are mapped to either a default map or a configured
Ingress Decode Policy Map.
L2 & L3 ACL Lookups
VLAN + MAC DA Lookup
Inbound
Packet
Recognize Inbound
Packet Priorities
and Map Packet priority
to an Internal Priority
and Drop Precedence
Count
Port
Priority PRAM
Priority Traffic
Policing
Towards further
Processing and then
Traffic Manager
Input for:
s
Stage 1
Stage 2
Recognize Received Values:
PCP value
DSCP value
-0,3
-ERGE
Map using the following
commands:
QOS
Force value using
the following commands:
qos dscp force
qos exp force
qos pcp force
Count defined
based on Internal
Priority Override or
Merge depending
ON
Force value using
the following commands:
priority force
DROP
PRECEDENCE
Input for:
s