Rate and give feedback:  Feedback Received. Thank You!

Rate and give feedback: 

X

This document helped resolve my issue

Yes No

Additional Comments

800 characters remaining

May we contact you if necessary?

Name:  

E-mail: 

Enter a valid Email ID

Need product assistance? Contact Juniper Support

Submit

This site is protected by hCaptcha and its Privacy Policy and Terms of Service apply.

English  

English

Example: Reducing Jitter in Hierarchical CoS Queues

Requirements

• MX960 router in an IPv4 network and running Junos OS Release 13.2 or later.
• Available Gigabit Ethernet port hosted on FPC slot 2, PIC slot 0, port 0.
• Available Gigabit Ethernet port hosted on port 0 of a Gigabit Ethernet Modular Interface Card (MIC) in PIC slot 0 of an MPC2 Q Modular Port Concentrator (MPC) in FPC slot 5.

Before you begin configuring this example, make sure that the maximum number of queues allowed for the hierarchical queuing MPC in slot 5 has not yet been configured. When you enter the show chassis fpc 5 command from configuration mode, the max-queues statement should not display.

Overview

In this example you configure hierarchical scheduling on a VLAN port hosted on a hierarchical queuing MPC. To reduce jitter in the queues for all egress ports hosted on the MPC, reduce the maximum number of queues allowed for MPC.

Configuration

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

Baseline Configuration

Step-by-Step Procedure

1. To configure the VLAN 1 input and output at xe-2/0/0.0 and xe-5/0/0.0:

   [edit]user@host# set interfaces xe-2/0/0 per-unit-scheduleruser@host# set interfaces xe-2/0/0 flexible-vlan-tagginguser@host# set interfaces xe-2/0/0 unit 0 vlan-id 1user@host# set interfaces xe-2/0/0 unit 0 family inet address 1.1.1.1/24 user@host# set interfaces xe-5/0/0 per-unit-scheduleruser@host# set interfaces xe-5/0/0 flexible-vlan-tagginguser@host# set interfaces xe-5/0/0 unit 0 vlan-id 1user@host# set interfaces xe-5/0/0 unit 0 family inet address 2.1.1.1/24

2. Map each of four queues to a forwarding class.

   [edit]user@host# set class-of-service forwarding-classes queue 0 beuser@host# set class-of-service forwarding-classes queue 1 efuser@host# set class-of-service forwarding-classes queue 2 afuser@host# set class-of-service forwarding-classes queue 3 nc

3. Assign a packet-scheduling priority value to each forwarding class.

   [edit]user@host# set class-of-service schedulers be_sch priority lowuser@host# set class-of-service schedulers ef_sch priority lowuser@host# set class-of-service schedulers af_sch priority strict-highuser@host# set class-of-service schedulers ef_sch priority low

4. Customize the default IEEE 802.1p classifier (BA classifier based on Layer 2 header) by defining different values for iEEE 802.1p code points.

   [edit]user@host# set class-of-service classifiers ieee_jitter forwarding-class be loss-priority low code-points 000user@host# set class-of-service classifiers ieee_jitter forwarding-class ef loss-priority low code-points 001user@host# set class-of-service classifiers ieee_jitter forwarding-class af loss-priority low code-points 010user@host# set class-of-service classifiers ieee_jitter forwarding-class nc loss-priority low code-points 011

5. Apply the BA classifier to the input of the logical units on xe-2/0/0.

   [edit]user@host# set interfaces xe-2/0/0 unit * classifiers ieee-802.1 ieee_jitter

6. Configure the scheduler map smap_jitter to map the forwarding classes to the schedulers.

   [edit]user@host# set class-of-service scheduler-maps smap_jitter forwarding-class be scheduler be_schuser@host# set class-of-service scheduler-maps smap_jitter forwarding-class ef scheduler ef_schuser@host# set class-of-service scheduler-maps smap_jitter forwarding-class af scheduler af_schuser@host# set class-of-service scheduler-maps smap_jitter forwarding-class nc scheduler nc_sch

7. Configure the traffic control profile tcp to combine the scheduler map smap_jitter (that maps the forwarding classes to the schedulers for port-based scheduling) with a shaping rate (for hierarchical scheduling).

   [edit]user@host# set class-of-service traffic-control-profiles tcp scheduler-map smap_jitteruser@host# set class-of-service traffic-control-profiles tcp shaping-rate 6g

8. Apply the traffic control profile to the router output at xe-5/0/0.

   [edit]user@host# set class-of-service-interfaces xe-5/0/0 unit * output-traffic-control-profile tcp

9. If you are done configuring the device, commit the configuration.

   [edit]user@host# commit

Results

Verification

Confirm that the configuration is working properly

• Measuring End-to-End Jitter to Establish the Baseline
• Configuring Jitter Reduction
• Measuring End-to-End Jitter to Verify Jitter Reduction

Measuring End-to-End Jitter to Establish the Baseline

Purpose

Establish a baseline measurement by noting the amount of jitter that occurs when the hierarchical queuing line card hosting the egress port is configured with the default maximum number of queues.

Action

1. Pass traffic through the VLAN.
2. Measure the variation in packet delay for selected packets in the data flow.

Configuring Jitter Reduction

Purpose

Reduce jitter in the VLAN port output queues.

Action

1. Configure a reduced maximum number of queues for egress ports on the hierarchical queuing MPC in slot 5, thereby reducing the jitter in the port queues.

   [edit]user@host# set chassis fpc 5 max-queue 64k

2. If you are done configuring the device, commit the configuration.

   [edit]user@host# commit

Measuring End-to-End Jitter to Verify Jitter Reduction

Purpose

Measure the amount of jitter that occurs when the hierarchical queuing line card hosting the egress port is configured with a reduced maximum number of queues.

Action

1. Pass traffic through the VLAN.
2. Measure the variation in packet delay for selected packets in the data flow.