PFC Configuration
Configuration
PFC feature supports lossless Ethernet for selected traffic classes in congested network environments.
Configuring PFC parameter exchange typically involves enabling PFC mode, turning on PFC, and allowing the negotiation of control for each traffic priority (priorities 0–7).
Note: On Tomahawk3 (TH3) platforms and LTSW platforms (Tomahawk4 (TH4) platforms, Tomahawk5 (TH5) platforms and Trident4 (TR4) platforms), performing add, delete, or update operations on PFC will cause a system-wide traffic interruption, resulting in configured session flaps.
Topology
This topology illustrates a spine-leaf router architecture where Priority Flow Control (PFC) manages traffic at the queue level, optimizing the flow from spine to leaf while minimizing packet loss and enhancing overall quality of service.
PFC Configuration
Configuring PFC
Execute the following steps to configure PFC on both interfaces on leaf router.
1. Enable PFC on interface ge49 / ge1.
!
interface ge49
priority-flow-control mode on
priority-flow-control enable priority 0 1 2
ip address 1.1.1.1/24
!
interface ge1
priority-flow-control mode on
priority-flow-control enable priority 0 1 2 3
ip address 2.2.2.1/24
!
2. Configure lossless with priority for the default queuing policy 0, 1, and 2.
policy-map type queuing default default-out-policy
class type queuing default q0
priority
lossless
exit
class type queuing default q1
priority
lossless
exit
class type queuing default q2
priority
lossless
exit
Sample Show Running Configurations:
OcNOS#show running-config interface ge49
!
interface ge49
priority-flow-control mode on
priority-flow-control enable priority 0 1 2
load-interval 30
ip address 1.1.1.1/24
!
OcNOS#
OcNOS#show running-config interface ge1
!
interface ge1
priority-flow-control mode on
priority-flow-control enable priority 0 1 2
priority-flow-control advertise-local-config
priority-flow-control cap 5
priority-flow-control link-delay-allowance 100
load-interval 30
ip address 2.2.2.1/24
!
OcNOS#
policy-map type queuing default default-out-policy
class type queuing default q0
priority
lossless
exit
class type queuing default q1
priority
lossless
exit
class type queuing default q2
priority
lossless
exit
!
Validation
Execute the following show commands to view the PFC information on Leaf:
To display statistics about the number of PFC pause frames sent and received for a specified L3 interface.
OcNOS#show priority-flow-control statistics all
interface pri pause sent pause received
======================================================
ge1 0 0 0
ge1 1 0 0
ge1 2 0 0
ge1 3 0 0
ge1 4 0 0
ge1 5 0 0
ge1 6 0 0
ge1 7 0 0
ge49 0 668536 0
ge49 1 0 0
ge49 2 0 0
ge49 3 0 0
ge49 4 0 0
ge49 5 0 0
ge49 6 0 0
ge49 7 0 0
To display the average traffic rate over the load interval of the interfaces ge49 and ge1.
OcNOS#show interface counters rate mbps
+-------------------+--------------+-------------+--------------+-------------+
| Interface | Rx mbps | Rx pps | Tx mbps | Tx pps |
+-------------------+--------------+-------------+--------------+-------------+
ge1 0.00 0 24.06 23493
ge49 24.16 23592 0.16 320
To display the ingress and egress traffic discard reason counters on the interface.
OcNOS#show interface counters indiscard-stats
+-------------+------------------+---------------+---------------+-----------------+------------------+--------------+--------------------+
| Interface | Port Block Drops | Vlan Discards | ACL/QOS Drops | Policy Discards | EGR Port Unavail | IBP Discards | Total Discards |
+-------------+------------------+---------------+---------------+-----------------+------------------+--------------+--------------------+
OcNOS#show interface counters queue-stats
E - Egress, I - Ingress, Q-Size is in bytes
* indicates monitor is active
+------------------+--------------------+--------+-----------------+-------------------+-----------------+-------------------+
| Interface | Queue/Class-map | Q-Size | Tx pkts | Tx bytes | Dropped pkts | Dropped bytes |
+------------------+--------------------+--------+-----------------+-------------------+-----------------+-------------------+
cpu best-effort (E) 0 16 1440 0 0
cpu nd (E) 0 52 4536 0 0
cpu bpdu (E) 0 276 18768 0 0
ge1 q0 (E) 435200 48098084 6156554752 0 0
ge1 q7 (E) 0 6 540 0 0
ge1 mc-q7 (E) 0 10 820 0 0
ge2 q7 (E) 0 4 344 0 0
ge2 mc-q7 (E) 0 12 1000 0 0
ge47 q7 (E) 0 4 344 0 0
ge47 mc-q7 (E) 0 16 1328 0 0
ge49 mc-q7 (E) 0 10 820 0 0
ge49 pg-q0 (I) 420352 NA NA NA NA
xe52 q7 (E) 0 6 540 0 0
xe52 mc-q7 (E) 0 9 738 0 0
xe53 mc-q7 (E) 0 10 820 0 0
OcNOS#show interface counters rate mbps
+-------------------+--------------+-------------+--------------+-------------+
| Interface | Rx mbps | Rx pps | Tx mbps | Tx pps |
+-------------------+--------------+-------------+--------------+-------------+
ge1 0.00 0 99.25 96926
ge49 99.27 96945 0.68 1327
OcNOS#show interface counters rate mbps
+-------------------+--------------+-------------+--------------+-------------+
| Interface | Rx mbps | Rx pps | Tx mbps | Tx pps |
+-------------------+--------------+-------------+--------------+-------------+
ge1 0.00 0 85.72 83710
ge49 85.72 83707 0.59 1146
OcNOS#show interface counters rate mbps
+-------------------+--------------+-------------+--------------+-------------+
| Interface | Rx mbps | Rx pps | Tx mbps | Tx pps |
+-------------------+--------------+-------------+--------------+-------------+
ge1 0.00 0 95.24 93011
ge49 95.24 93012 0.65 1274
OcNOS#show priority-flow-control statistics all
interface pri pause sent pause received
======================================================
ge1 0 0 0
ge1 1 0 0
ge1 2 0 0
ge1 3 0 0
ge1 4 0 0
ge1 5 0 0
ge1 6 0 0
ge1 7 0 0
ge49 0 0 0
ge49 1 45822 0
ge49 2 0 0
ge49 3 0 0
ge49 4 0 0
ge49 5 0 0
ge49 6 0 0
ge49 7 0 0
OcNOS#show interface counters rate mbps
+-------------------+--------------+-------------+--------------+-------------+
| Interface | Rx mbps | Rx pps | Tx mbps | Tx pps |
+-------------------+--------------+-------------+--------------+-------------+
ge1 0.00 0 100.01 97661
ge49 100.01 97663 0.68 1337
OcNOS#
OcNOS#show interface counters rate mbps
+-------------------+--------------+-------------+--------------+-------------+
| Interface | Rx mbps | Rx pps | Tx mbps | Tx pps |
+-------------------+--------------+-------------+--------------+-------------+
ge1 0.00 0 100.00 97660
ge49 100.00 97657 0.68 1337
OcNOS#show priority-flow-control statistics all
interface pri pause sent pause received
======================================================
ge1 0 0 0
ge1 1 0 0
ge1 2 0 0
ge1 3 0 0
ge1 4 0 0
ge1 5 0 0
ge1 6 0 0
ge1 7 0 0
ge49 0 0 0
ge49 1 0 0
ge49 2 50660 0
ge49 3 0 0
ge49 4 0 0
ge49 5 0 0
ge49 6 0 0
ge49 7 0 0