associate to queue 1 using the policy map. The same class map needs to be applied in switch B as welland when queue 1 gets congested, PFC would be generated for priority 2. Switch A on receiving PFCframes with priority 2 would stop scheduling queue 1.If a tagged packet with VLAN dot1p as 5 ingresses on switch A. Consider that tagged packet also hasDSCP in range of 0-7.These packets will match the class map and get queued on queue 1 on both theswitches.But when queue 1 gets congested on switch B, PFC frames for tagged packets will not be generated asPFC is not enabled on dot1p priority 5.Support for marking dot1p value in L3 Input Qos PolicyIn case the incoming packet is untagged and the packet which goes out to the peer is tagged, then thedot1p should be marked appropriately using L3 Input Qos Policy. This is required because in the peerswitch PFC will be generated based on the dot1p value. Currently if the ingress is untagged and egress istagged, then dot1p priority 0(default) will be added as part of the tag header and from the next hop PFCwill be based on that dot1p priority. Support is added to mark the dot1p value in the L3 Input Qos Policyin this feature. Hence it is possible to mark both DSCP and Dot1p simultaneously in the L3 Input QosPolicy. You are expected to mark the Dot1p priority when the ingress packets are untagged but go out tothe peer as taggedNOTE: L2 qos-policy behavior will be retained and would not be changed, that is we would notallow to set both DSCP and Dot1p in the L2 Input Qos Policy.Example case:Consider that two switches A and B are connected back to back via a tagged interface. Consider the casewhere untagged packets arrive on switch A, if you want to generate PFC for priority 2 for DSCP range0-7, then you must need to match the interested traffic using the class map. You should create an L3Input Qos Policy and mark vlan dot1p as 2. You have to associate both the L3 class map and L3 Input QosPolicy to queue 1 using the policy map.In switch B, global dot1p honoring should be enabled, this will queue the packets on queue 1 as the dot1pwill be 2 and PFC should be enabled for priority 2. The policy map applied on switch A need not beenabled in switch B. When queue 1 in switch B gets congested, PFC will be generated for priority 2 whichwill be honored in switch A.You will not get the below CLI errors after adding this support:Dell(conf)#qos-policy-input qos-inputDell(conf-qos-policy-in)#set mac-dot1p 5% Error: Dot1p marking is not allowed on L3 Input Qos Policy.Dell(conf-qos-policy-in)#You will also be able to mark both DSCP and Dot1p in the L3 Input Qos Policy:Dell(conf)#qos-policy-input qos-inputDell(conf-qos-policy-in)#set mac-dot1p 2Dell(conf-qos-policy-in)#set ip-dscp 5Dell Dell(conf-qos-policy-in)#Quality of Service (QoS) 725
