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Example: Configuring CoS PFC for FCoE Traffic
Priority-based flow control (PFC, described in IEEE 802.1Qbb) is a link-level flow control mechanism that you apply at ingress interfaces. PFC enables you to divide traffic on one physical link into eight priorities. You can think of the eight priorities as eight “lanes” of traffic that correspond to queues (forwarding classes). Each priority is mapped to a 3-bit IEEE 802.1p CoS value in the VLAN header.
You can selectively apply PFC to the traffic in any queue without pausing the traffic in other queues on the same link. You must apply PFC to FCoE traffic to ensure lossless transport.
This example describes how to configure PFC for FCoE traffic:
Requirements
This example uses the following hardware and software components:
One switch
Junos OS Release 11.1 or later for the QFX Series
Overview
FCoE traffic requires PFC to ensure lossless packet transport. This example shows you how to configure PFC on FCoE traffic, use the default FCoE forwarding-class-to-queue mapping and:
Configure a classifier that associates the FCoE forwarding class with FCoE traffic, which is identified by IEEE 802.1p code point 011 (priority 3).
Configure a congestion notification profile to apply PFC to the FCoE traffic.
Apply the classifier and the PFC configuration to ingress interfaces.
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 the CoS bandwidth scheduling for the FCoE forwarding class output queue.
On switches that support enhanced transmission selection (ETS) hierarchical port scheduling, create a forwarding class set (priority group) that includes the FCoE forwarding class; this is required to configure enhanced transmission selection (ETS) and support data center bridging (DCB).
For ETS, configure the bandwidth scheduling for the FCoE priority group.
Apply the configuration to ingress and egress interfaces. How this is done differs depending on whether you use ETS or direct port scheduling for the CoS configuration.
For direct port scheduling, you apply a scheduler map directly to the interface. A scheduler map maps schedulers to forwarding classes, and applies the CoS properties of the scheduler to the output queue mapped to the forwarding class.
For ETS hierarchical port scheduling, you apply the scheduler map to a traffic control profile, and then apply the traffic control profile to the interface. The scheduler map maps CoS properties to forwarding classes (and their associated output queues) just as it does for direct port scheduling. The traffic control profile maps CoS properties to the priority group (a group of forwarding classes defined in a forwarding class set) that contains the forwarding class, creating a CoS hierarchy that allocates port bandwidth to a group of forwarding classes (priority group), and then allocates the priority group bandwidth to the individual forwarding classes.
Each interface in this example acts as both an ingress interface and an egress interface, so the classifier, congestion notification profile, and scheduling are applied to all of the interfaces.
Topology
Table 1 shows the configuration components for this example.
Component |
Settings |
|---|---|
Hardware |
One switch |
Behavior aggregate classifier (maps the FCoE forwarding class to incoming packets by IEEE 802.1 code point) |
Code point Ingress interfaces: |
PFC congestion notification profile |
|
FCoE queue scheduler |
|
Forwarding class-to-scheduler mapping |
Scheduler map On switches that support direct port scheduling, if you use
port scheduling, attach the scheduler map directly to interfaces |
ETS only: Forwarding class set (FCoE priority group) |
|
ETS only: Traffic control profile |
For ETS hierarchical scheduling, attach the traffic control
profile (using the |
Figure 1 shows a block diagram of the configuration components and the configuration flow of the CLI statements used in the example.
Configuration
- CLI Quick Configuration
- Common Configuration (Applies to ETS Hierarchical Scheduling and to Port Scheduling)
- ETS Hierarchical Scheduling Configuration
- Port Scheduling Configuration
- Results
CLI Quick Configuration
To quickly configure PFC for FCoE traffic, copy the following commands, paste them in a text file, remove 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 configuration is separated into the configuration common to ETS and direct port scheduling, and the portions of the configuration that apply only to ETS and only to port scheduling.
Common Configuration that applies to ETS Hierarchical Scheduling and to Port Scheduling:
[edit class-of-service] set classifiers ieee-802.1 fcoe-classifier forwarding-class fcoe loss-priority low code-points 011 set congestion-notification-profile fcoe-cnp input ieee-802.1 code-point 011 pfc set interfaces xe-0/0/31 unit 0 classifiers ieee-802.1 fcoe-classifier set interfaces xe-0/0/32 unit 0 classifiers ieee-802.1 fcoe-classifier set interfaces xe-0/0/33 unit 0 classifiers ieee-802.1 fcoe-classifier set interfaces xe-0/0/34 unit 0 classifiers ieee-802.1 fcoe-classifier set interfaces xe-0/0/31 congestion-notification-profile fcoe-cnp set interfaces xe-0/0/32 congestion-notification-profile fcoe-cnp set interfaces xe-0/0/33 congestion-notification-profile fcoe-cnp set interfaces xe-0/0/34 congestion-notification-profile fcoe-cnp set schedulers fcoe-sched priority low transmit-rate 3g set schedulers fcoe-sched shaping-rate percent 100 set scheduler-maps fcoe-map forwarding-class fcoe scheduler fcoe-sched
Configuration for ETS hierarchical scheduling—the ETS-specific portion of this example configures forwarding class set (priority group) membership, priority group CoS settings (traffic control profile), and assigns the priority group and its CoS configuration to the interfaces:
[edit class-of-service] set forwarding-class-sets fcoe-pg class fcoe set traffic-control-profiles fcoe-tcp scheduler-map fcoe-map guaranteed-rate 3g set traffic-control-profiles fcoe-tcp shaping-rate percent 100 set interfaces xe-0/0/31 forwarding-class-set fcoe-pg output-traffic-control-profile fcoe-tcp set interfaces xe-0/0/32 forwarding-class-set fcoe-pg output-traffic-control-profile fcoe-tcp set interfaces xe-0/0/33 forwarding-class-set fcoe-pg output-traffic-control-profile fcoe-tcp set interfaces xe-0/0/34 forwarding-class-set fcoe-pg output-traffic-control-profile fcoe-tcp
Configuration for port scheduling—the port-scheduling-specific portion of this example assigns the scheduler map (which sets the CoS treatment of the forwarding classes in the scheduler map) to the interfaces:
[edit class-of-service] set interfaces xe-0/0/31 scheduler-map fcoe-map set interfaces xe-0/0/32 scheduler-map fcoe-map set interfaces xe-0/0/33 scheduler-map fcoe-map set interfaces xe-0/0/34 scheduler-map fcoe-map
Common Configuration (Applies to ETS Hierarchical Scheduling and to Port Scheduling)
Step-by-Step Procedure
To configure the ingress classifier for FCoE traffic, PFC on the FCoE traffic, apply the PFC and classifier configurations to interfaces, and configure queue scheduling, for both ETS hierarchical scheduling and port scheduling (common configuration):
Configure a classifier to set the loss priority and IEEE 802.1 code point assigned to the FCoE forwarding class at the ingress:
[edit class-of-service] user@switch# set classifiers ieee-802.1 fcoe-classifier forwarding-class fcoe loss-priority low code-points 011
Configure PFC on the FCoE queue by applying FCoE to the IEEE 802.1 code point
011:[edit class-of-service] user@switch# set congestion-notification-profile fcoe-cnp input ieee-802.1 code-point 011 pfc
Apply the PFC configuration to the ingress interfaces:
[edit class-of-service] user@switch# set interfaces xe-0/0/31 congestion-notification-profile fcoe-cnp user@switch# set interfaces xe-0/0/32 congestion-notification-profile fcoe-cnp user@switch# set interfaces xe-0/0/33 congestion-notification-profile fcoe-cnp user@switch# set interfaces xe-0/0/34 congestion-notification-profile fcoe-cnp
Assign the classifier to the ingress interfaces:
[edit class-of-service] user@switch# set interfaces xe-0/0/31 unit 0 classifiers ieee-802.1 fcoe-classifier user@switch# set interfaces xe-0/0/32 unit 0 classifiers ieee-802.1 fcoe-classifier user@switch# set interfaces xe-0/0/33 unit 0 classifiers ieee-802.1 fcoe-classifier user@switch# set interfaces xe-0/0/34 unit 0 classifiers ieee-802.1 fcoe-classifier
Configure output scheduling for the FCoE queue:
[edit class-of-service] user@switch# set schedulers fcoe-sched priority low transmit-rate 3g user@switch# set schedulers fcoe-sched shaping-rate percent 100
Map the FCoE forwarding class to the FCoE scheduler:
[edit class-of-service] user@switch# set scheduler-maps fcoe-map forwarding-class fcoe scheduler fcoe-sched
ETS Hierarchical Scheduling Configuration
Step-by-Step Procedure
To configure the forwarding class set (priority group) and priority group scheduling (in a traffic control profile), and apply the ETS hierarchical scheduling for FCoE traffic to interfaces:
Configure the forwarding class set for the FCoE traffic:
[edit class-of-service] user@switch# set forwarding-class-sets fcoe-pg class fcoe
Define the traffic control profile for the FCoE forwarding class set:
[edit class-of-service] user@switch# set traffic-control-profiles fcoe-tcp scheduler-map fcoe-map guaranteed-rate 3g user@switch# set traffic-control-profiles fcoe-tcp shaping-rate percent 100
Apply the FCoE forwarding class set and traffic control profile to the egress ports:
[edit class-of-service] user@switch# set interfaces xe-0/0/31 forwarding-class-set fcoe-pg output-traffic-control-profile fcoe-tcp user@switch# set interfaces xe-0/0/32 forwarding-class-set fcoe-pg output-traffic-control-profile fcoe-tcp user@switch# set interfaces xe-0/0/33 forwarding-class-set fcoe-pg output-traffic-control-profile fcoe-tcp user@switch# set interfaces xe-0/0/34 forwarding-class-set fcoe-pg output-traffic-control-profile fcoe-tcp
Port Scheduling Configuration
Step-by-Step Procedure
To apply port scheduling for FCoE traffic to interfaces:
Apply the scheduler map to the egress ports:
[edit class-of-service] user@switch# set interfaces xe-0/0/31 scheduler-map fcoe-map user@switch# set interfaces xe-0/0/32 scheduler-map fcoe-map user@switch# set interfaces xe-0/0/33 scheduler-map fcoe-map user@switch# set interfaces xe-0/0/34 scheduler-map fcoe-map
Results
Display the results of the configuration (the system
shows only the explicitly configured parameters; it does not show
default parameters such as the fcoe lossless forwarding
class). The results are from the ETS hierarchical scheduling configuration
to show the more complex configuration. Direct port scheduling results
would not show the traffic control profile or forwarding class set
portions of the configuration, and would display the name of the scheduler
map under each interface (instead of the names of the forwarding class
set and output traffic control profile), but is otherwise the same.
user@switch> show configuration class-of-service
classifiers {
ieee-802.1 fcoe-classifier {
forwarding-class fcoe {
loss-priority low code-points 011;
}
}
traffic-control-profiles {
fcoe-tcp {
scheduler-map fcoe-map;
shaping-rate percent 100;
guaranteed-rate 3000000000;
}
}
forwarding-class-sets {
fcoe-pg {
class fcoe;
}
}
congestion-notification-profile {
fcoe-cnp {
input {
ieee-802.1 {
code-point 011 {
pfc;
}
}
}
}
}
interfaces {
xe-0/0/31 {
congestion-notification-profile fcoe-cnp;
forwarding-class-set {
fcoe-pg {
output-traffic-control-profile fcoe-tcp;
}
}
unit 0 {
classifiers {
ieee-802.1 fcoe-classifier;
}
}
}
xe-0/0/32 {
congestion-notification-profile fcoe-cnp;
forwarding-class-set {
fcoe-pg {
output-traffic-control-profile fcoe-tcp;
}
}
unit 0 {
classifiers {
ieee-802.1 fcoe-classifier;
}
}
}
xe-0/0/33 {
congestion-notification-profile fcoe-cnp;
forwarding-class-set {
fcoe-pg {
output-traffic-control-profile fcoe-tcp;
}
}
unit 0 {
classifiers {
ieee-802.1 fcoe-classifier;
}
}
}
xe-0/0/34 {
congestion-notification-profile fcoe-cnp;
forwarding-class-set {
fcoe-pg {
output-traffic-control-profile fcoe-tcp;
}
}
unit 0 {
classifiers {
ieee-802.1 fcoe-classifier;
}
}
}
}
scheduler-maps {
fcoe-map {
forwarding-class fcoe scheduler fcoe-sched;
}
}
schedulers {
fcoe-sched {
transmit-rate 3000000000;
shaping-rate percent 100;
priority low;
}
}
To quickly configure the interfaces, issue the load
merge terminal command and then copy the hierarchy and paste
it into the switch terminal window.
Verification
To verify that the PFC configuration for FCoE traffic components has been created and is operating properly, perform these tasks:
- Verifying That Priority-Based Flow Control Has Been Enabled
- Verifying the Ingress Interface PFC Configuration
Verifying That Priority-Based Flow Control Has Been Enabled
Purpose
Verify that PFC is enabled on the FCoE queue to enable lossless transport.
Action
List the congestion notification profiles using the
operational mode command show class-of-service congestion-notification:
user@switch> show class-of-service congestion-notification
Type: Input, Name: fcoe-cnp, Index: 51697
Cable Length: 100 m
Priority PFC MRU
000 Disabled
001 Disabled
010 Disabled
011 Enabled 2500
100 Disabled
101 Disabled
110 Disabled
111 Disabled
Type: Output
Priority Flow-Control-Queues
000
0
001
1
010
2
011
3
100
4
101
5
110
6
111
7
Meaning
The show class-of-service congestion-notification operational command lists all of the congestion notification profiles
and which IEEE 802.1p code points have PFC enabled. The command output
shows that PFC is enabled on code point 011 for the fcoe-cnp congestion notification profile.
The command also shows the default cable length (100 meters), the default maximum receive unit (2500 bytes), and the default mapping of priorities to output queues because this example does not include configuring these options.
Verifying the Ingress Interface PFC Configuration
Purpose
Verify that the classifier fcoe-classifier and the congestion notification profile fcoe-cnp are
configured on ingress interfaces xe-0/0/31, xe-0/0/32, xe-0/0/33, and xe-0/0/34.
Action
List the ingress interfaces using the operational mode
command show configuration class-of-service interfaces:
user@switch> show configuration class-of-service interfaces xe-0/0/31
congestion-notification-profile fcoe-cnp;
unit 0 {
classifiers {
ieee-802.1 fcoe-classifier;
}
}user@switch> show configuration class-of-service interfaces xe-0/0/32
congestion-notification-profile fcoe-cnp;
unit 0 {
classifiers {
ieee-802.1 fcoe-classifier;
}
}user@switch> show configuration class-of-service interfaces xe-0/0/33
congestion-notification-profile fcoe-cnp;
unit 0 {
classifiers {
ieee-802.1 fcoe-classifier;
}
}user@switch> show configuration class-of-service interfaces xe-0/0/34
congestion-notification-profile fcoe-cnp;
unit 0 {
classifiers {
ieee-802.1 fcoe-classifier;
}
}Meaning
The show configuration class-of-service interfaces commands list the congestion notification profile that is mapped
to the interface (fcoe-cnp) and the IEEE 802.1p classifier
associated with the interface (fcoe-classifier).