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How to configure Priority Flow Control

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Information

 
TitleHow to configure Priority Flow Control
Objective
Use Priority Flow Control to Pause certain traffic when a buffer congestion is detected to allow a portion of the traffic to pause and allowing other traffic on the port.
Environment
EXOS ALL
Flow Control / QOS
Procedure

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Configure each of the 10G links L3 and L4 into three Traffic Class Groups TCG0, TCG1 and TCG2 for LAN, SAN and IPC traffic respectively. Allocate 4Gps (40%) for the LAN traffic, 4Gps (40%) for the SAN traffic and 2Gps (20%) for the IPC traffic.  Enable Priority Flow Control for the TCG1 (SAN traffic). 

Assume LAN, SAN and IPC traffic is present on links L3 and L4 with unique 802.1p values of 0, 1 and 2 respectively. 

Map QoS Profiles (QP) to the Traffic Class Groups as follows.

QP 3 = ETS TCG2, IPC traffic

QP 2 = ETS TCG1, SAN traffic

QP 1 = ETS TCG0, LAN traffic

Also map 802.1p values of 0, 1, 2 to QoS Profiles QP1, QP2 and QP3 respectively.

The DCB Profile of the traffic is summarized in the table below. 

Traffic Class Group QoS Profile 802.1p value PFC Bandwidth % Min. Bandwidth Max. Bandwidth

TCG2    (IPC) QP3 2 No 20 20 100

TCG1   (SAN) QP2 1 Yes 40 40 100

TCG0   (LAN) QP1 0 No 40 40 100

Configuration steps for the Core Switch.

Create the QoS profiles. (Note that qp1 already exists by default.)

create qosprofile qp2

create qosprofile qp3

Configure the QoS scheduling method so that the IPC traffic can be configured as strict priority and the LAN/SAN traffic as weighted round robin.

configure qosscheduler weighted-round-robin

configure qosprofile qp3 use-strict-priority

Map the 802.1p priorities to QoS profiles.

configure dot1p type 0 qp1

configure dot1p type 1 qp2

configure dot1p type 2 qp3

Configure the bandwidth egress rate shaping for these QoS Profiles on link L3 

configure qosprofile qp1 minbw 40 maxbw 100 ports 2:1

configure qosprofile qp2 minbw 40 maxbw 100 ports 2:1

configure qosprofile qp3 minbw 20 maxbw 100 ports 2:1

Now do the same for link L4.

configure qosprofile qp1 minbw 40 maxbw 100 ports 2:2

configure qosprofile qp2 minbw 40 maxbw 100 ports 2:2

configure qosprofile qp3 minbw 20 maxbw 100 ports 2:2

Enable PFC for the SAN traffic on the links L2, L3 and L4

enable flow-control rx-pause qosprofile qp2 ports 2:1,2:2,2:4

enable flow-control tx-pause priority 1 ports 2:1,2:2,2:4

Configuration steps for the Top-of-rack switches.

Create the QoS profiles. Note that qp1 already exists by default.

create  qosprofile qp2

create  qosprofile qp3

Configure the QoS scheduling method so that the IPC traffic can be configured as strict priority and the LAN/SAN traffic as weighted round robin.

configure qosscheduler weighted-round-robin

configure qosprofile qp3 use-strict-priority

Map the 802.1p priorities to QoS profiles.

configure dot1p type 0 qp1

configure dot1p type 1 qp2

configure dot1p type 2 qp3

Now configure the bandwidth egress rate shaping for these QoS Profiles on each uplink. 

configure qosprofile qp1 minbw 40 maxbw 100 ports 1

configure qosprofile qp2 minbw 40 maxbw 100 ports 1

configure qosprofile qp3 minbw 20 maxbw 100 ports 1

Now enable Priority Flow Control for the SAN traffic on the uplinks L3 and L4

enable flow-control rx-pause qosprofile qp2 ports 1

enable flow-control tx-pause priority 1 ports 1

Additional notes

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