Brocade Multi-Service IronWare QoS and Traffic Management Configuration Guide (Supporting R05.6.00) - Manual (Page 59)

Multi-Service IronWare QoS and Traffic Management Configuration Guide 45
53-1003037-02
Forcing the priority of a packet
3
Custom decode support
User defined decode maps are supported on the Brocade NetIron CES and Brocade NetIron CER.
The custom decode maps have the following implication for QoS handling:
• Per port custom decode maps are not supported. Only a single global QoS map is
supported.
• A number of custom decode maps can be defined in the Multi-Service IronWare, but only
one can be active at any time in the hardware.
• A user defined map can be applied to replace any existing map including the default map.
• User defined maps are supported for PCP, EXP and DSCP.
• Custom decode maps are supported. This means that packet can be decoded by any one
of the many user defined map currently active in the hardware but there will be one and
only encode map. Encoding will always be based on default encode map.
• The packet will be decoded as per the decode map, but during encoding NOT all the values
will be encoded correctly.
• If the packet is decoded based on DSCP value, the Brocade NetIron CES and Brocade
NetIron CER will decode the packet to correct internal priority (Traffic Class) and Drop
Precedence. This QoS will be internally respected and packet will be treated in accordance
with the assigned Priority and DP. During encoding (if enabled) however, the Brocade
NetIron CES and Brocade NetIron CER will encode all the packet QoS attributes as shown
below:
• Assume trust mode is DSCP and encoding policy is turned on for UP and DSCP
• Assume custom Decode Map: DSCP 56 to Priority 0 and DP 0
• Encode map is always default
• IPv4 tagged packet comes with DSCP 56 and UP 5
• The packet will be assigned Internal Priority of 0 and DP of 0
• The packet going out will have 802.1p value of 0
• The packet will NOT have expected DSCP value of 0, instead it will go out unchanged
(56)
• If the packet is decoded based on PCP value (which is possible if qos trust mode is PCP
force or no trust mode is forced but packet is Tagged and payload is not IPv4), the Brocade
NetIron CES will decode the packet to correct internal priority (Traffic Class) and Drop
Precedence. This QoS will be internally respected and packet will be treated in accordance
with the assigned Priority and DP. During encoding (if enabled) however, Brocade NetIron
CES and Brocade NetIron CER will encode all the packet QoS attributes as shown below:
• Assume trust mode is DSCP and encoding policy is turned on for UP and DSCP
• Assume custom Decode Map: PCP 5 to Priority 0 and DP 0
• Encode map is always default
• Assume an IPv4 tagged packet comes with DSCP 56 and UP 5
• The packet will be assigned Internal Priority of 0 and DP of 0
• The packet going out will have DSCP value of 0
• The packet will not have expected PCP value of 0, instead it will go out unchanged (5)