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Example: Configuring PFC Across Layer 3 Interfaces

Requirements

• Two Juniper Networks QFX5100 Switches
• Junos OS Release 13.2 or later for the QFX Series
• Two Ethernet hosts

Overview

• Configure the Layer 2 and Layer 3 interfaces on the switches
• Configure VLANs to carry the traffic across the Layer 2 and Layer 3 networks
• Configure integrated routing and bridging (IRB) interfaces on the Layer 2 interfaces to move the Layer 2 VLAN traffic to Layer 3
• Configure and apply the appropriate classifiers to the interfaces
• Configure and apply congestion notification profiles (CNPs) on the interfaces to enable PFC on the traffic that you want to be lossless

  Note: Configuring or changing PFC on an interface blocks the entire port until the PFC change is completed. After a PFC change is completed, the port is unblocked and traffic resumes. Blocking the port stops ingress and egress traffic, and causes packet loss on all queues on the port until the port is unblocked.

• Configure lossless forwarding classes and hierarchical port scheduling (also known as enhanced transmission selection) on the interfaces

Note: PFC operates at the queue level, based on the IEEE 802.1p code point in the priority code point (PCP) field of the Ethernet frame header (sometimes known as the CoS bits). For this reason, traffic on Layer 3 interfaces on which you want to enable PFC must use an IEEE 802.1p classifier to map incoming traffic to forwarding classes (which are in turn mapped to output queues) and loss priorities. You cannot use a DSCP or DSCP IPv6 classifier to classify Layer 3 traffic if you want to enable PFC on traffic flows.

Topology

Figure 1 shows the topology for this example.

Figure 1: Enabling PFC Across Layer 3 Interface Hops

Table 1 shows the configuration components for this example. On the two QFX5100 switches, the Ethernet host-facing interfaces use the same interface names and configuration, and the Layer 3 network-facing interfaces use the same interface names and configuration.

Configuration

• Step-by-Step Procedure
• Results

CLI Quick Configuration

To configure PFC across Layer 3 interfaces, copy the following commands, paste them in a text file, remove the line breaks, change variables and details to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level. The same configuration applies to both QFX5100 Switch SW1 and QFX5100 Switch SW2:

Step-by-Step Procedure

Step-by-Step Procedure

1. Configure the Layer 3 interface VLANs and IP addresses:
   [edit interfaces]
user@switch# set xe-0/0/40 vlan-tagging
user@switch# set xe-0/0/40 unit 0 vlan-id 103
user@switch# set xe-0/0/40 unit 0 family inet address 100.103.1.2/24
user@switch# set xe-0/0/41 vlan-tagging
user@switch# set xe-0/0/41 unit 0 vlan-id 104
user@switch# set xe-0/0/41 unit 0 family inet address 100.104.1.2/24

   
   

2. Configure the Layer 2 interface VLAN membership and interface mode:
   [edit interfaces]
user@switch# set xe-0/0/20 unit 0 family ethernet-switching interface-mode trunk
user@switch# set xe-0/0/20 unit 0 family ethernet-switching vlan members vlan105
user@switch# set xe-0/0/21 unit 0 family ethernet-switching interface-mode trunk
user@switch# set xe-0/0/21 unit 0 family ethernet-switching vlan members vlan106

   
   

3. Configure the IRB interfaces and VLANs to transport incoming Layer 2 traffic assigned to VLANs vlan105 (of which interface xe-0/0/20 is a member) and vlan106 (of which interface xe-0/0/21 is a member) across Layer 3:
   [edit]
user@switch# set interfaces irb unit 105 family inet address 100.105.1.1/24
user@switch# set interfaces irb unit 106 family inet address 100.106.1.1/24
user@switch# set vlans vlan105 vlan-id 105
user@switch# set vlans vlan106 vlan-id 106
user@switch# set vlans vlan105 l3-interface irb.105
user@switch# set vlans vlan106 l3-interface irb.106

   
   

4. Configure the lossless forwarding classes and a best-effort forwarding class for any other traffic that might use the interfaces:
   [edit class-of-service]
user@switch# set forwarding-classes class lossless-3 queue-num 3 no-loss
user@switch# set forwarding-classes class lossless-4 queue-num 4 no-loss
user@switch# set forwarding-classes class all-others queue-num 0

   
   

5. Configure the IEEE classifier for the Layer 2 and Layer 3 interfaces to classify incoming traffic into the lossless forwarding classes based on the IEEE 802.1p code point of the traffic:
   [edit class-of-service classifiers]
user@switch# set ieee-802.1 lossless-3-4-ieee forwarding-class lossless-3 loss-priority low code-points 011
user@switch# set ieee-802.1 lossless-3-4-ieee forwarding-class lossless-4 loss-priority low code-points 100

   
   

6. Configure the CNP to enable PFC on the lossless priorities (the lossless forwarding classes mapped to IEEE 802.1p code points 3 and 4):
   [edit class-of-service congestion-notification-profile]
user@switch# set lossless-cnp input ieee-802.1 code-point 011 pfc
user@switch# set lossless-cnp input ieee-802.1 code-point 100 pfc

   
   

7. Configure hierarchical scheduling to support the lossless configuration (included here for completeness; see the Related Documentation links for detailed examples of scheduling configuration) and apply it to the Layer 2 and Layer 3 interfaces:
   [edit class-of-service]
set schedulers lossless_sch transmit-rate 6g
set schedulers lossless_sch shaping-rate percent 100
set schedulers all-others_sch transmit-rate 4g
set scheduler-maps lossless_map forwarding-class lossless-3 scheduler lossless_sch
set scheduler-maps lossless_map forwarding-class lossless-4 scheduler lossless_sch
set scheduler-maps all-others_map forwarding-class all-others scheduler all-others_sch
set forwarding-class-sets lossless_fc_set class lossless-3
set forwarding-class-sets lossless_fc_set class lossless-4
set forwarding-class-sets all-others_fc_set class all-others
set traffic-control-profiles lossless_tcp scheduler-map lossless_map
set traffic-control-profiles lossless_tcp guaranteed-rate percent 60
set traffic-control-profiles lossless_tcp shaping-rate percent 100
set traffic-control-profiles all-others_tcp scheduler-map all-others_map
set traffic-control-profiles all-others_tcp guaranteed-rate percent 40
set interfaces xe-0/0/20 forwarding-class-set lossless_fc_set output-traffic-control-profile lossless_tcp
set interfaces xe-0/0/20 forwarding-class-set all-others_fc_set output-traffic-control-profile all-others_tcp
set interfaces xe-0/0/21 forwarding-class-set lossless_fc_set output-traffic-control-profile lossless_tcp
set interfaces xe-0/0/21 forwarding-class-set all-others_fc_set output-traffic-control-profile all-others_tcp
set interfaces xe-0/0/40 forwarding-class-set lossless_fc_set output-traffic-control-profile lossless_tcp
set interfaces xe-0/0/40 forwarding-class-set all-others_fc_set output-traffic-control-profile all-others_tcp
set interfaces xe-0/0/41 forwarding-class-set lossless_fc_set output-traffic-control-profile lossless_tcp
set interfaces xe-0/0/41 forwarding-class-set all-others_fc_set output-traffic-control-profile all-others_tcp

   
   

8. Apply the Layer 2 IEEE 802.1p classifier and the CNP to the Layer 3 interfaces:
   [edit class-of-service interfaces]
user@switch# set xe-0/0/40 classifiers ieee-802.1 lossless-3-4-ieee
user@switch# set xe-0/0/40 congestion-notification-profile lossless-cnp
user@switch# set xe-0/0/41 classifiers ieee-802.1 lossless-3-4-ieee
user@switch# set xe-0/0/41 congestion-notification-profile lossless-cnp

   
   

9. Apply the Layer 2 IEEE 802.1p classifier and the CNP to the Layer 2 interfaces:
   [edit class-of-service interfaces]
user@switch# xe-0/0/20 unit 0 classifiers ieee-802.1 lossless-3-4-ieee
user@switch# xe-0/0/20 congestion-notification-profile lossless-cnp
user@switch# xe-0/0/21 unit 0 classifiers ieee-802.1 lossless-3-4-ieee
user@switch# xe-0/0/21 congestion-notification-profile lossless-cnp

   
   

Results

Display the results of the interface, VLAN, and class-of-service configurations (the system shows only the explicitly configured parameters; it does not show default parameters). The results are valid for both QFX5100 Switch SW1 and QFX5100 Switch SW2 because the same configuration is used on both switches.

xe-0/0/20 {
    unit 0 {
        family ethernet-switching {
            interface-mode trunk;
            vlan {
                members vlan105;
            }
        }
    }
}
xe-0/0/21 {
    unit 0 {
        family ethernet-switching {
            interface-mode trunk;
            vlan {
                members vlan106;
            }
        }
    }
}
xe-0/0/40 {
    vlan-tagging;
    unit 0 {
        vlan-id 103;                    
        family inet {
            address 100.103.1.2/24;
        }
    }
}
xe-0/0/41 {
    vlan-tagging;
    unit 0 {
        vlan-id 104;
        family inet {
            address 100.104.1.2/24;
        }
    }
}
irb {
    unit 105 {
        family inet {
            address 100.105.1.1/24;
        }
    }
    unit 106 {
        family inet {
            address 100.106.1.1/24;     
        }
    }
}
vlan {
    unit 105 {
        family inet {
            address 100.105.1.1/24;
        }
    }
    unit 106 {
        family inet {
            address 100.106.1.1/24;
        }
    }
}

vlan105 {
    vlan-id 105;
    l3-interface irb.105;
}
vlan106 {
    vlan-id 106;
    l3-interface irb.106;
}

classifiers {
    ieee-802.1 lossless-3-4-ieee {
        forwarding-class lossless-3 {
            loss-priority low code-points 011;
        }
        forwarding-class lossless-4 {
            loss-priority low code-points 100;
        }
    }
}
forwarding-classes {
    class lossless-3 queue-num 3 no-loss;
    class lossless-4 queue-num 4 no-loss;
    class all-others queue-num 0;
}
traffic-control-profiles {              
    lossless_tcp {
        scheduler-map lossless_map;
        shaping-rate percent 100;
        guaranteed-rate percent 60;
    }
    all-others_tcp {
        scheduler-map all-others_map;
        guaranteed-rate percent 40;
    }
}
forwarding-class-sets {
    lossless_fc_set {
        class lossless-3;
        class lossless-4;
    }
    all-others_fc_set {
        class all-others;
    }
}
congestion-notification-profile {
    lossless-cnp {
        input {
            ieee-802.1 {                
                code-point 011 {
                    pfc;
                }
                code-point 100 {
                    pfc;
                }
            }
        }
    }
}
interfaces {
    xe-0/0/20 {
        forwarding-class-set {
            lossless_fc_set {
                output-traffic-control-profile lossless_tcp;
            }
            all-others_fc_set {
                output-traffic-control-profile all-others_tcp;
            }
        }
        congestion-notification-profile lossless-cnp;
        unit 0 {
            classifiers {               
                ieee-802.1 lossless-3-4-ieee;
            }
        }
    }
    xe-0/0/21 {
        forwarding-class-set {
            all-others_fc_set {
                output-traffic-control-profile all-others_tcp;
            }
            lossless_fc_set {
                output-traffic-control-profile lossless_tcp;
            }
        }
        congestion-notification-profile lossless-cnp;
        unit 0 {
            classifiers {
                ieee-802.1 lossless-3-4-ieee;
            }
        }
    }
    xe-0/0/40 {
        forwarding-class-set {
            lossless_fc_set {           
                output-traffic-control-profile lossless_tcp;
            }
            all-others_fc_set {
                output-traffic-control-profile all-others_tcp;
            }
        }
        congestion-notification-profile lossless-cnp;
        classifiers {
            ieee-802.1 lossless-3-4-ieee;
        }
    }
    xe-0/0/41 {
        forwarding-class-set {
            lossless_fc_set {
                output-traffic-control-profile lossless_tcp;
            }
            all-others_fc_set {
                output-traffic-control-profile all-others_tcp;
            }
        }
        congestion-notification-profile lossless-cnp;
        classifiers {                   
            ieee-802.1 lossless-3-4-ieee;
        }
    }
}
scheduler-maps {
    lossless_map {
        forwarding-class lossless-3 scheduler lossless_sch;
        forwarding-class lossless-4 scheduler lossless_sch;
    }
    all-others_map {
        forwarding-class all-others scheduler all-others_sch;
    }
}
schedulers {
    lossless_sch {
        transmit-rate 6g;
        shaping-rate percent 100;
    }
    all-others_sch {
        transmit-rate 4g;
    }
}                                    

Tip: To quickly configure the switch, issue the load merge terminal command, and then copy the hierarchies and paste them into the switch terminal window.

Verification

To verify that the PFC across Layer 3 interfaces configuration has been created and is operating properly, perform these tasks:

• Verifying the Interface Configuration
• Verifying the VLAN Configuration
• Verifying the PFC Configuration (Congestion Notification Profile)
• Verify the Forwarding Class Configuration
• Verifying the Classifier Configuration
• Verifying the Interface CoS Configuration (Hierarchical Scheduling, PFC, and Classifier Mapping to Interfaces)

Verifying the Interface Configuration

Purpose

Verify that the Layer 2 Ethernet interfaces, Layer 3 IP interfaces, IRB interfaces, and VLAN interfaces have been created on the switch and are correctly configured.

Action

xe-0/0/20 {
    unit 0 {
        family ethernet-switching {
            interface-mode trunk;
            vlan {
                members vlan105;
            }
        }
    }
}
xe-0/0/21 {
    unit 0 {
        family ethernet-switching {
            interface-mode trunk;
            vlan {
                members vlan106;
            }
        }
    }
}
xe-0/0/40 {
    vlan-tagging;
    unit 0 {
        vlan-id 103;                    
        family inet {
            address 100.103.1.2/24;
        }
    }
}
xe-0/0/41 {
    vlan-tagging;
    unit 0 {
        vlan-id 104;
        family inet {
            address 100.104.1.2/24;
        }
    }
}
irb {
    unit 105 {
        family inet {
            address 100.105.1.1/24;
        }
    }
    unit 106 {
        family inet {
            address 100.106.1.1/24;     
        }
    }
}
vlan {
    unit 105 {
        family inet {
            address 100.105.1.1/24;
        }
    }
    unit 106 {
        family inet {
            address 100.106.1.1/24;
        }
    }
}

Meaning

• Interfaces xe-0/0/20 and xe-0/0/21 are Ethernet interfaces (family ethernet-switching) in trunk interface mode. Interface xe-0/0/20 is a member of VLAN vlan105, and interface xe-0/0/21 is a member of VLAN vlan106.
• Interfaces xe-0/0/40 and xe-0/0/41 are IP interfaces (family inet) with VLAN tagging enabled. Interface xe-0/0/40 has an IP address of 100.103.1.2/24 and a VLAN ID of 103. Interface xe-0/0/41 has an IP address of 100.104.1.2/24 and a VLAN ID of 104.
• Two IRB interfaces are configured, IRB unit 105 with an IP address of 100.105.1.1/24 and IRB unit 106 with an IP address of 100.106.1.1/24.
• Two VLAN interfaces are configured, VLAN unit 105 with an IP address of 100.105.1.1/24 (for IRB interface unit 105) and VLAN unit 106 with an IP address of 100.106.1.1/24 (for IRB interface unit 106).

Verifying the VLAN Configuration

Purpose

Verify that VLANs have been created on the switch and are correctly configured.

Action

vlan105 {
    vlan-id 105;
    l3-interface irb.105;
}
vlan106 {
    vlan-id 106;
    l3-interface irb.106;
}

Meaning

• VLAN vlan105 has been configured with VLAN ID 105 on IRB interface irb.105.
• VLAN vlan106 has been configured with VLAN ID 106 on IRB interface irb.106.

Verifying the PFC Configuration (Congestion Notification Profile)

Purpose

Verify that PFC has been enabled on the correct IEEE 802.1p code points (priorities) in the CNP.

Action

lossless-cnp {
    input {
        ieee-802.1 {
            code-point 011 {
                pfc;
            }
            code-point 100 {
                pfc;
            }
        }
    }
}

Meaning

• The CNP named lossless-cnp is configured on the switch.
• The CNP lossless-cnp enables PFC on IEEE 802.1p code points 100 and 100.

Verify the Forwarding Class Configuration

Purpose

Verify that the two lossless forwarding classes and the best-effort forwarding class have been configured on the switch.

Action

class lossless-3 queue-num 3 no-loss;
class lossless-4 queue-num 4 no-loss;
class all-others queue-num 0;

Meaning

• Forwarding class lossless-3 is mapped to queue 3 and is configured as a lossless forwarding class (the no-loss attribute is applied)
• Forwarding class lossless-4 is mapped to queue 4 and is configured as a lossless forwarding class (the no-loss attribute is applied)
• Forwarding class all-others is mapped to queue 0. It is not a lossless forwarding class (the no-loss attribute is not applied).

Verifying the Classifier Configuration

Purpose

Verify that the IEEE 802.1p classifier has been configured on the switch.

Action

ieee-802.1 lossless-3-4-ieee {
    forwarding-class lossless-3 {
        loss-priority low code-points 011;
    }
    forwarding-class lossless-4 {
        loss-priority low code-points 100;
    }
}

Meaning

The show configuration class-of-service classifiers command displays all of the classifiers configured on the switch. The command output shows that the Layer 2 IEEE 802.1p classifier lossless-3-4-ieee classifiers traffic with the code point 011 into the lossless-3 forwarding class with a loss priority of low, and classifies traffic with the code point 100 into the lossless-4 forwarding class with a loss priority of low.

Verifying the Interface CoS Configuration (Hierarchical Scheduling, PFC, and Classifier Mapping to Interfaces)

Purpose

Verify that the interfaces have the correct hierarchical scheduling, PFC, and classifier configurations.

Action

xe-0/0/20 {
    forwarding-class-set {
        lossless_fc_set {
            output-traffic-control-profile lossless_tcp;
        }
        all-others_fc_set {
            output-traffic-control-profile all-others_tcp;
        }
    }
    congestion-notification-profile lossless-cnp;
    unit 0 {
        classifiers {
            ieee-802.1 lossless-3-4-ieee;
        }
    }
}
xe-0/0/21 {
    forwarding-class-set {
        all-others_fc_set {
            output-traffic-control-profile all-others_tcp;
        }
        lossless_fc_set {
            output-traffic-control-profile lossless_tcp;
        }                               
    }
    congestion-notification-profile lossless-cnp;
    unit 0 {
        classifiers {
            ieee-802.1 lossless-3-4-ieee;
        }
    }
}
xe-0/0/40 {
    forwarding-class-set {
        lossless_fc_set {
            output-traffic-control-profile lossless_tcp;
        }
        all-others_fc_set {
            output-traffic-control-profile all-others_tcp;
        }
    }
    congestion-notification-profile lossless-cnp;
    classifiers {
        ieee-802.1 lossless-3-4-ieee;
    }
}                                       
xe-0/0/41 {
    forwarding-class-set {
        lossless_fc_set {
            output-traffic-control-profile lossless_tcp;
        }
        all-others_fc_set {
            output-traffic-control-profile all-others_tcp;
        }
    }
    congestion-notification-profile lossless-cnp;
    classifiers {
        ieee-802.1 lossless-3-4-ieee;
    }
}

Meaning

• The configuration on Layer 2 Ethernet interfaces xe-0/0/20 and xe-0/0/21 includes:
  • Hierarchical scheduling—The forwarding class set lossless_fc_set with the traffic control profile lossless_tcp for the lossless traffic, and the forwarding class set all-others_fc_set with the traffic control profile all-others_tcp for the best-effort traffic are applied to both interfaces.
  • PFC—The lossless-cnp congestion notification profile is applied to both interfaces.
  • Classifiers—The Layer 2 IEEE 802.1p classifier lossless-3-4-ieee is applied to both interfaces.
• The configuration on Layer 3 IP interfaces xe-0/0/40 and xe-0/0/41 includes:
  • Hierarchical scheduling—The forwarding class set lossless_fc_set with the traffic control profile lossless_tcp for the lossless traffic, and the forwarding class set all-others_fc_set with the traffic control profile all-others_tcp for the best-effort traffic are applied to both interfaces.
  • PFC—The lossless-cnp congestion notification profile is applied to both interfaces.
  • Classifiers—The Layer 2 IEEE 802.1p classifier lossless-3-4-ieee is applied to both interfaces. Traffic that would use a DSCP or a DSCP IPv6 classifier if it were configured uses the IEEE 802.1p classifier instead. Using the IEEE 802.1p classifier allows the interface to use PFC to pause traffic during periods of congestion to prevent packet loss.