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Example: Configuring IEEE 802.1p Priority Remapping on an FCoE-FC Gateway

FCoE traffic typically uses IEEE 802.1p priority 3 (code point 011). However, if your FCoE network uses a different IEEE 802.1p priority than priority 3 for FCoE traffic, then you can use priority remapping to classify FCoE traffic into a lossless forwarding class mapped to that priority. You specify the lossless forwarding class used for the FCoE traffic by configuring a fixed classifier and applying it to the native FC (NP_Port) interface. All traffic received from the FC SAN on that NP_Port interface is classified into the forwarding class specified in the fixed classifier.

When native FC interfaces on the FCoE-FC gateway encapsulate incoming FC traffic in Ethernet to create FCoE frames, by default they assign IEEE 802.1p code point 011 to the FCoE traffic, forward the traffic internally to the gateway Ethernet interfaces, and then forward the traffic to the FCoE network. Setting a rewrite value for the IEEE 802.1p code point configures the gateway native FC interface to assign the rewrite value priority to the FCoE frames when the native FC interface forwards the FCoE frames to the gateway Ethernet interface. Instead of a priority of 3, the FCoE frames use the priority specified in the rewrite value.

You can configure one rewrite value for each local FCoE-FC gateway fabric. All of the native FC interfaces in a particular fabric must use the same rewrite value. Native FC interfaces that belong to different FCoE-FC gateway fabrics can use different rewrite values.

This example shows how to configure FCoE priority remapping for a converged Ethernet network that uses priority 5 (IEEE code point 101) for FCoE traffic. If your network uses priority 3 for FCoE traffic, then you do not need to remap the FCoE priority, because the default configuration supports lossless FCoE transport on priority 3.

Requirements

This example uses the following hardware and software components:

  • One Juniper Networks QFX3500 Switch

  • Junos OS Release 12.3 or later for the QFX Series

Overview

Native FC interfaces on an FCoE-FC gateway receive native FC traffic from the FC SAN and encapsulate it in Ethernet to create FCoE frames. Priority remapping enables you to map the encapsulated FC traffic (the FCoE traffic) to any IEEE 802.1p priority.

To support lossless FCoE traffic flows, you must configure the remapped priority correctly on the native FC interfaces and also on the Ethernet interfaces that connect to the FCoE network. Achieving lossless behavior for FCoE traffic when you remap the FCoE priority requires configuring:

  • A lossless forwarding class for FCoE traffic (or using the default fcoe forwarding class)

  • A behavior aggregate (BA) classifier on the FCoE Ethernet interfaces to map the FCoE forwarding class to the IEEE 802.1p code points (priority) used for FCoE traffic on the FCoE network (the ingress classifier priority for the forwarding class must be the same as the rewrite value priority)

  • A fixed classifier on the FCoE-FC gateway FC interface that maps all traffic from the FC network into the lossless FCoE forwarding class (the forwarding class must be lossless)

  • A priority rewrite value that remaps the IEEE 802.1p code point on the FCoE-FC gateway FC interface to the priority used for FCoE traffic on the FCoE network

  • An input congestion notification profile (CNP) to enable priority-based flow control (PFC) on the FCoE code point (the code point used as the rewrite value) at the Ethernet interface ingress and an output CNP to configure flow control to pause the correct output queue at the Ethernet interface egress

    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.

  • A DCBX application and application map on the Ethernet interface to support DCBX application TLV exchange for the lossless FCoE traffic on the FCoE priority

The priority specified in the BA classifier, CNP, and DCBX application map on the Ethernet ingress interfaces must match the priority specified in the fixed classifier and rewrite value configurations on the FC interfaces. You must specify the same lossless FCoE forwarding class in each configuration and use the same IEEE 802.1p code point (priority) so that the FCoE traffic is properly classified into flows and so that those flows receive lossless treatment.

Topology

This example shows how to configure priority remapping of FCoE traffic on one native FC interface (fc-0/0/2) connected to the FC SAN and on one Ethernet interface (xe-0/0/27) connected to the converged Ethernet (FCoE) network. Both the native FC interface and the Ethernet interface belong to the same local FC fabric on the FCoE-FC gateway.

The converged Ethernet network uses priority 5 (IEEE 80.21p code point 101) for FCoE traffic. The native FC interface on the FCoE-FC gateway receives FC traffic from the FC SAN. The native FC interface encapsulates the FC traffic in Ethernet to create FCoE frames, tags the frames with the IEEE 802.1p priority value 101, and then forwards the FCoE frames to the FCoE-FC gateway Ethernet interface. Because traffic marked with IEEE 802.1p priority 5 is mapped to a lossless FCoE forwarding class, the traffic receives lossless treatment. The Ethernet interface forwards the FCoE traffic on to the Ethernet network.

FCoE traffic (tagged with priority 5) arriving at the FCoE-FC gateway from the Ethernet network receives lossless treatment and is forwarded to the native FC interface. The native FC interface removes the Ethernet encapsulation from the FCoE frames and forwards the resulting native FC traffic to the FC SAN.

Figure 1 shows the topology for this example, and Table 1 shows the configuration components for this example.

Figure 1: Topology of the IEEE 802.1p Priority Remapping ExampleTopology of the IEEE 802.1p Priority Remapping Example
Table 1: Components of the IEEE 802.1p Priority Remapping Configuration Topology

Component

Settings

Hardware

QFX3500 switch

Forwarding class configuration

Name—fcoe1

Queue mapping—queue 5

Packet drop attribute—no-loss

Note:

The lossless forwarding class can be mapped to any output queue. However, because FCoE uses priority 5 in this example, matching that traffic to a forwarding class that uses queue 5 creates a configuration that is logical and easy to map because the priority and the queue are identified by the same number.

BA classifier (Ethernet interface)

Name—fcoe_gw_classifier

Maps code point 101 (IEEE 802.1p priority 5) to the fcoe1 forwarding class and assigns traffic a packet loss priority of low.

The classifier is applied to Ethernet interface xe-0/0/27.

Fixed classifier (native FC interface)

Forwarding class—fcoe1

The classifier is applied to native FC interface fc-0/0/2

Rewrite value

IEEE 802.1p code point—101

The rewrite value is applied to native FC interface fc-0/0/2

PFC configuration (CNP on Ethernet interface)

Name—fcoe1_p5_rewrite_cnp

Input CNP code point—101

Output CNP code point—101

Output CNP flow control queue—5

Interface—xe-0/0/27

DCBX application mapping

Application name—myfcoe5

Application ether-type—0x8906

Application map name—myfcoe5_map

Application map code points—101

Interface—xe-0/0/27

Note:

LLDP and DCBX must be enabled on the interface. By default, LLDP and DCBX are enabled on all Ethernet interfaces.

The priority used to identify FCoE traffic (5, IEEE 802.1p code point 101) is configured for lossless transport across the QFX device on interfaces xe-0/0/27 and fc-0/0/2, which belong to the same local FC fabric on the FCoE-FC gateway.

On the Ethernet interface, the classifier maps priority 5 to a lossless forwarding class (fcoe1), the input CNP enables PFC on incoming priority 5 traffic, and the output CNP enables output queue 5 to respond to pause messages received from the peer on traffic tagged with priority 5. On the native FC interface, FC traffic is remapped from priority 3 (the default mapping) to priority 5 and assigned to the same lossless forwarding class, fcoe1, because of the fixed classifier configuration. In this way, traffic tagged with priority 5 on interfaces xe-0/0/27 and fc-0/0/2 receives lossless treatment.

Note:

To avoid fate sharing, ensure that the remapped priority is classified only to the forwarding class used in the fixed classifier on all other interfaces. For example, if you configure a fixed classifier on an FC interface that classifies all of the traffic into lossless forwarding class fcoe1 and remaps the priority to priority 5 (IEEE 802.1p code point 101), then in all other classifier configurations on all other interfaces, priority 5 should always be classified to forwarding class fcoe1. If you classify priority 6 on another interface to forwarding class fcoe1, then congestion on priority 6 traffic affects priority 5 traffic unfairly.

Note:

This example does not include scheduling (bandwidth allocation) configuration or the local FC fabric configuration. This examples focuses only on priority remapping.

Configuration

CLI Quick Configuration

To quickly configure IEEE 802.1p priority remapping on an FCoE-FC gateway, 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.

Procedure

Step-by-Step Procedure

To configure a lossless forwarding class for FCoE traffic, classify FCoE traffic into that forwarding class, configure a rewrite value on the native FC interface for the FCoE traffic, and enable PFC on the Ethernet interface, and configure DCBX application protocol TLV exchange for FCoE traffic:

  1. Configure the lossless forwarding class (named fcoe1 and mapped to output queue 5) for FCoE traffic that uses IEEE 802.1p priority  5:

  2. Configure an ingress classifier named fcoe_gw_classifier to map the FCoE priority (IEEE 802.1p code point 101) to the lossless FCoE forwarding class (fcoe1):

  3. Apply the classifier named fcoe_gw_classifier to Ethernet interface xe-0/0/27:

  4. Configure the fixed classifier on the native FC interface, using the lossless FCoE forwarding class fcoe1 (all traffic from the FC SAN is classified into the specified forwarding class). The traffic classified into this forwarding class is tagged with the priority value configured in the next step.

  5. Configure the rewrite value (IEEE 802.1p code point 101) applied to all incoming traffic from the FC SAN on the native FC interface. The rewrite value is the IEEE 802.1p priority that the encapsulated FCoE traffic classified into the fcoe1 forwarding class uses on the converged Ethernet network.

  6. Configure the input stanza of the CNP (named fcoe1_p5_rewrite_cnp) to enable PFC on the FCoE priority on the Ethernet interface:

  7. Configure the output stanza of the CNP to enable output queue 5 to respond to pause messages received from the peer on traffic tagged with priority 5:

  8. Apply the CNP named fcoe1_p5_rewrite_cnp to Ethernet interface xe-0/0/27:

  9. Configure a DCBX application for FCoE to map to the Ethernet interface, so that DCBX can exchange application protocol TLVs on the correct (remapped) IEEE 802.1p FCoE priority:

  10. Configure a DCBX application map to map the FCoE application to the correct (remapped) IEEE 802.1p FCoE priority:

  11. Apply the application map to the Ethernet interface so that DCBX exchanges FCoE application TLVs on the correct code point:

Verification

To verify the configuration and proper operation of IEEE 802.1p priority remapping on an FCoE-FC gateway, perform these tasks:

Verifying the Forwarding Class Configuration

Purpose

Verify that the lossless forwarding class fcoe1 has been created.

Action

Show the forwarding class configuration by using the operational command show class-of-service forwarding class:

Meaning

The show class-of-service forwarding-class command shows all of the forwarding classes. The command output shows that the fcoe1 forwarding class is configured on output queue 5 with the no-loss packet drop attribute enabled.

Because we did not explicitly configure the default forwarding classes, they remain in their default state, including the lossless configuration of the fcoe and no-loss default forwarding classes.

Verifying the Behavior Aggregate Classifier Configuration

Purpose

Verify that the classifier maps the forwarding classes to the correct IEEE 802.1p code points (priorities) and packet loss priorities.

Action

List the classifier configured for priority remapping using the operational mode command show class-of-service classifier name fcoe_gw_classifier:

Meaning

The show class-of-service classifier name fcoe_gw_classifier command shows the IEEE 802.1p code points and the loss priorities that are mapped to the forwarding classes in the classifier. The command output shows that the classifier maps forwarding class fcoe1 to IEEE 802.1p code point 101 (priority 5) with a packet loss priority of low.

Verifying the FC Interface Configuration (Fixed Classifier, Rewrite Value)

Purpose

Verify that the native FC interface (NP_Port) classifies incoming traffic into forwarding class fcoe1 and that the interface rewrite value is priority 5 (IEEE code point 101).

Action

Display the FC interface configuration using the operational mode command show configuration class-of-service interfaces fc-0/0/2:

Meaning

The show configuration class-of-service interfaces fc-0/0/2 command shows that the rewrite value for incoming (input) traffic is IEEE 802.1p code point 101 (priority 5), and that the interface uses forwarding class fcoe1 as the fixed classifier for all incoming traffic.

Verifying the Ethernet Interface PFC Configuration (CNP)

Purpose

Verify that PFC is enabled on the correct priority (IEEE 802.1p code point 101) for lossless transport and that flow control is enabled on the correct output queue (queue 5) on the Ethernet interface.

Action

List the congestion notification profile using the operational mode command show class-of-service congestion-notification fcoe1_p5_rewrite_cnp:

Meaning

The show class-of-service congestion-notification fcoe1_p5_rewrite_cnp command shows the input and output stanzas of the CNP. The input stanza shows that PFC is enabled on IEEE 802.1p code point 101 (priority 5). The input stanza also shows that the CNP uses the default values of 100 meters for the cable length value and 2500 bytes for the maximum receive unit (MRU) value.

The output stanza shows that flow control is enabled on output queue 5 for IEEE 802.1p priority code point 101 (priority 5).

Verifying the Ethernet Interface Configuration

Purpose

Verify that the classifier fcoe_gw_classifier and the congestion notification profile fcoe1_p5_rewrite_cnp are configured on Ethernet interface xe-0/0/27.

Action

List the ingress interfaces using the operational mode command show configuration class-of-service interfaces xe-0/0/27:

Meaning

The show configuration class-of-service interfaces xe-0/0/27 command shows that the congestion notification profile fcoe1_p5_rewrite_cnp is configured on the interface, and that the IEEE 802.1p classifier associated with the interface is fcoe_gw_classifier.

Verifying the DCBX Application Configuration

Purpose

Verify that the DCBX application named myfcoe5 for FCoE is configured.

Action

List the DCBX applications by using the configuration mode command show applications:

Meaning

The show applications configuration mode command shows all of the configured applications. The output shows that the application myfcoe5 is configured with an EtherType of 0x8906 (the correct EtherType for FCoE traffic).

Verifying the DCBX Application Map Configuration

Purpose

Verify that the application map myfcoe5_app_map is configured.

Action

List the application map by using the configuration mode command show policy-options application-maps:

Meaning

The show policy-options application-maps configuration mode command lists all of the configured application maps and the applications that belong to each application map. The output shows that there is one application map, myfcoe5_app_map, which consists of the application named myfcoe5 mapped to IEEE 802.1p code point 101 (priority 5).

Verifying the DCBX Application Protocol Exchange Interface Configuration

Purpose

Verify that the application map is applied to the correct interface (xe-0/0/27).

Action

List the application maps using the configuration mode command show protocols dcbx:

Meaning

The show protocols dcbx configuration mode command lists the application map association with interfaces. The output shows that interface xe-0/0/27 uses application map myfcoe5_app_map.