Dell N3200-ON EMC Networking N-Series Switches CLI Reference Guide version 6.6 - Page 711

CoS mapping tables, port default priority, and hardware queue parameters may be configured on LAG interfaces as well as Ethernet port interfaces. Queue Mapping The priority of a packet arriving at an interface is used to steer the packet to the appropriate outbound CoS queue through a mapping table. Network packets arriving at an ingress port are directed to one of n queues in an egress port(s) based on the translation of packet priority to CoS queue. The CoS mapping tables define the queue used to handle each enumerated type of user priority designated in either the 802.1p User Priority, or IP DSCP contents of a packet. If neither of these fields is trusted to contain a meaningful COS queue designation, the ingress port can be configured to use its default priority to specify the CoS queue. CoS queue mappings use the concept of trusted and untrusted ports. A trusted port is one that takes at face value a certain priority designation within arriving packets. Specifically, a port may be configured to trust one of the following packet fields: • IEEE 802.1p User Priority • IP Precedence • IP DSCP Packets arriving at the port ingress are inspected and their trusted field value is used to designate the COS queue that the packet is placed when forwarded to the appropriate egress port. A mapping table associates the trusted field value with the desired COS queue. Alternatively, a port may be configured as untrusted, whereby it does not trust any incoming packet priority designation and uses the port default priority value instead. All packets arriving at the ingress of an untrusted port are directed to a specific COS queue on the appropriate egress port(s) in accordance with the configured default priority of the ingress port. This process is also used for cases where a trusted port mapping is unable to be honored, such as when a non-IP packet arrives at a port configured to trust the User Priority or IP DSCP value. Layer 2 Switching Commands 711