PFC with QOS Configuration
Priority-based Flow Control (PFC) is a way which provides a link-level flow control mechanism that can be controlled independently for each frame priority. The goal of this mechanism is to ensure zero loss (lossless) under congestion in DCB networks.
Quality of Serive (QoS) works by default with lossy behaviour, which is required for proper functioning of minimum bandwidth, shaping and scheduling.
The requirement is to support PFC when QoS is enabled, ability to control lossy/lossless setting of port queues.
Note: The PFC with QoS works only for known unicast traffic.
Note: To manage peer congestion effectively, the shaper rate should only be applied to the egress interface of the peer node. Applying congestion control to all interfaces would inhibit PFC generation in response to peer congestion.
Topology
PFC with QoS
PFC with QoS Configuration
PFC + QoS functionality: On setting lossless on queue, traffic should be not be dropped at egress queue and on setting PFC on ingress, pause frames will be generated in order to reduce excess ingress traffic.
Note: The pause frame queue follows the VLAN priority of the source traffic. If it's necessary to adjust the VLAN priority on the switch, you can use the command set cos to make this change.
Note: When a pause frame is received in Device-1, congestion should be enforced on the egress interface of Device-2.
Configuration on Device-1
OcNOS#conf ter | Enter configure mode |
OcNOS(config)#hostname Device-1 | Configure host name |
OcNOS(config)#commit | Commit |
Device-1(config)#qos enable | Enable QoS |
Device-1(config)#qos statistics | Enable QoS Statistics |
Device-1(config)#bridge 1 protocol rstp vlan-bridge | Configure bridge group |
Device-1(config)#data-center-bridging enable bridge 1 | Enable data-center-bridging |
Device-1(config)#priority-flow-control enable bridge 1 | Enable priority-flow-control |
Device-1(config)#commit | Commit |
Device-1(config)#class-map type qos match-all CLASS1 | Configure QoS Class-map |
Device-1(config-cmap-qos)#match layer4 udp source-port 4791 | Define a classification criteria |
Device-1(config-cmap-qos)#exit | Exit |
Device-1(config)#commit | Commit |
Device-1(config)#policy-map type qos POLICY1 | Configure QoS Policy-map |
Device-1(config-pmap-qos)#class type qos CLASS1 | Configure class type and specify the class-map type |
Device-1(config-pmap-c-qos)#set queue 4 | Setting a new value in the packet Egress queue for matched traffic |
Device-1(config-pmap-c-qos)#exit | Exit |
Device-1(config-pmap-qos)#exit | Exit |
Device-1(config)#commit | Commit |
Device-1(config)#policy-map type queuing default DEFAULTPOLICY | Configure QoS Policy-map |
Device-1(config-pmap-que-def)# class type queuing default q0 | Configure class type and specify the class-map type |
Device-1(config-pmap-c-que-def)# priority | Priority value of class-map attached to this policy-map |
Device-1(config-pmap-c-que-def)# exit | Exit |
Device-1(config-pmap-que-def)# class type queuing default q4 | Configure class type and specify the class-map type |
Device-1(config-pmap-c-que-def)# priority | Priority value of class-map attached to this policy-map |
Device-1(config-pmap-c-que-def)# lossless | enable lossless settings on egress queue |
Device-1(config-pmap-c-que-def)# exit | Exit |
Device-1(config-pmap-que-def)#commit | Commit |
Device-1(config-pmap-que-def)#exit | Exit |
Device-1(config)#interface xe3 | Configure Interface |
Device-1(config-if)# switchport | Set the switching characteristics of interface |
Device-1(config-if)# bridge-group 1 | Bridge-group |
Device-1(config-if)# switchport mode trunk | Set the mode of L2 interface as trunk |
Device-1(config-if)# switchport trunk allowed vlan all | Set the VLAN’s to be allowed |
Device-1(config-if)# shape rate 100 mbps burst 1000 | Configure QoS egress traffic shape |
Device-1(config-if)# service-policy type queuing output DEFAULTPOLICY | Configure a service-policy of type queuing to the egress interface. |
Device-1(config-if)#exit | Exit |
Device-1(config)#commit | Commit |
Device-1(config)#interface xe8 | Configure Interface |
Device-1(config-if)# switchport | Set the switching characteristics of interface |
Device-1(config-if)# bridge-group 1 | Bridge-group |
Device-1(config-if)# switchport mode trunk | Set the mode of L2 interface as trunk |
Device-1(config-if)# switchport trunk allowed vlan all | Set the VLAN’s to be allowed |
Device-1(config-if)# priority-flow-control mode on | Set priority-flow-control mode as ON |
Device-1(config-if)# priority-flow-control enable priority 0 4 | Set priority-flow-control mode’s priority |
Device-1(config-if)#service-policy type qos input POLICY1 | Configure QoS service policy |
Device-1(config-if)#exit | Exit |
Device-1(config)bridge 1 address 0000.0000.0101 forward xe3 | Configure a static MAC forwarding for the bridge with Client’s destination mac address / Ingress interface MAC of Device-1 to consider the traffic as known Unicast.“ |
Device-1(config)#commit | Commit |
Configuration on Device-2
OcNOS#conf ter | Enter configure mode |
OcNOS(config)#hostname Device-2 | Configure host name |
OcNOS(config)#commit | Commit |
Device-2(config)#qos enable | Enable QOS |
Device-2(config)#qos statistics | Enable QOS Statistics |
Device-2(config)#bridge 1 protocol rstp vlan-bridge | Configure bridge group |
Device-2(config)#data-center-bridging enable bridge 1 | Enable data-center-bridging |
Device-2(config)#priority-flow-control enable bridge 1 | Enable priority-flow-control |
Device-2(config)#commit | Commit |
Device-2(config)#class-map type qos match-all CLASS1 | Configure QOS Class-map |
Device-2(config-cmap-qos)#match layer4 udp source-port 4791 | Define a classification criteria |
Device-2(config-cmap-qos)#exit | Exit |
Device-2(config)#commit | Commit |
Device-2(config)#policy-map type qos POLICY1 | Configure QOS Policy-map |
Device-2(config-pmap-qos)#class type qos CLASS1 | Configure class type and specify the class-map type |
Device-2(config-pmap-c-qos)#set queue 4 | Setting a new value in the packet Egress queue for matched traffic |
Device-2(config-pmap-c-qos)#exit | Exit |
Device-2(config-pmap-qos)#commit | Commit |
Device-2(config-pmap-qos)#policy-map type queuing default DEFAULTPOLICY | Configure QOS Policy-map |
Device-2(config-pmap-que-def)# class type queuing default q0 | Configure class type and specify the class-map type |
Device-2(config-pmap-c-que-def)# priority | Priority value of class-map attached to this policy-map |
Device-2(config-pmap-c-que-def)# exit | Exit |
Device-2(config-pmap-que-def)# class type queuing default q4 | Configure class type and specify the class-map type |
Device-2(config-pmap-c-que-def)# priority | Priority value of class-map attached to this policy-map |
Device-2(config-pmap-c-que-def)# lossless | enable lossless settings on egress queue |
Device-2(config-pmap-c-que-def)# exit | Exit |
Device-2(config-pmap-que-def)#commit | Commit |
Device-2(config)#interface xe3 | Configure Interface |
Device-2(config-if)# switchport | Set the switching characteristics of interface |
Device-2(config-if)# bridge-group 1 | Bridge-group |
Device-2(config-if)# switchport mode trunk | Set the mode of L2 interface as trunk |
Device-2(config-if)# switchport trunk allowed vlan all | Set the VLAN’s to be allowed |
Device-2(config-if)#exit | Exit |
Device-2(config)#commit | Commit |
Device-2(config)#interface xe7 | Configure Interface |
Device-2(config-if)# switchport | Set the switching characteristics of interface |
Device-2(config-if)# bridge-group 1 | Bridge-group |
Device-2(config-if)# switchport mode trunk | Set the mode of L2 interface as trunk |
Device-2(config-if)# switchport trunk allowed vlan all | Set the VLAN’s to be allowed |
Device-2(config-if)# priority-flow-control mode on | Set priority-flow-control mode as ON |
Device-2(config-if)# priority-flow-control enable priority 0 4 | Set priority-flow-control mode’s priority |
Device-2(config-if)#service-policy type qos input POLICY1 | Configure QoS service policy |
Device-2(config-if)# shape rate 100 mbps burst 1000 | Configure QoS egress traffic shape |
Device-2(config-if)#exit | Exit |
Device-2(config)#commit | Commit |
Validation
Verify Pause frames Sent from Device-1
Device-1#show priority-flow-control statistics bridge 1
bridge : 1
interface pri pause sent pause received
===========================================
xe7 0 0 0
xe7 1 0 0
xe7 2 0 0
xe7 3 0 0
xe7 4 100265 0
xe7 5 0 0
xe7 6 0 0
xe7 7 0 0
Verify Pause frames Sent from peer node (Device-2)
Device-1#show priority-flow-control statistics bridge 1
bridge : 1
interface pri pause sent pause received
===========================================
xe3 0 0 94731
xe3 1 0 0
xe3 2 0 0
xe3 3 0 0
xe3 4 0 0
xe3 5 0 0
xe3 6 0 0
xe3 7 0 0
xe8 0 181682 0
xe8 1 0 0
xe8 2 0 0
xe8 3 0 0
xe8 4 0 0
xe8 5 0 0
xe8 6 0 0
xe8 7 0 0