Complete MPLS QoS Short Pipe Mode Configuration Lab on Cisco IOS | MPLS VPN QoS Part 4

Complete MPLS QoS Short Pipe Mode Configuration Lab Part 4

In Part 1 we built the MPLS Layer 3 VPN infrastructure using:

• OSPF
• MPLS
• LDP
• MP-BGP
• VRFs
• PE-CE Routing

In Part 2 we implemented MPLS QoS using Uniform Mode.

In Part 3 we implemented MPLS QoS using Long Pipe Mode.

Now in Part 4 we will configure MPLS QoS using Short Pipe Mode.

🎯 What You Will Learn

• MPLS Short Pipe Mode
• Difference between Uniform, Pipe, Long Pipe, and Short Pipe modes
• Customer-side QoS handling
• Traffic policing
• Priority Queuing
• Precedence-based QoS policies
• SP and Customer QoS separation
• MPLS QoS architecture

Table of Contents

• 1. MPLS Short Pipe Mode Introduction
• 2. Customer SLA Agreement
• 3. Remove Previous Long Pipe Configuration
• 4. Configure MPLS Short Pipe Mode
• 5. Verification Commands
• 6. MPLS QoS Mathematics
• 7. QoS Mode Comparison
• 8. Troubleshooting
• 9. Related Articles

1. MPLS QoS Short Pipe Mode Introduction

MPLS Short Pipe Mode is a QoS model where:

• The Service Provider network uses its own internal QoS policies
• The PE router applies QoS to customer traffic using the customer packet markings
• MPLS EXP values are ignored on the PE-CE egress link

Short Pipe Mode Logic

$$ Customer\\ QoS = Customer\\ Packet\\ Marking $$

But:

$$ SP\\ QoS \neq Customer\\ QoS $$

In Short Pipe Mode:

• The SP core uses MPLS EXP internally
• The PE router does not copy MPLS EXP values into the customer packet
• QoS on the PE-CE link is based only on the customer packet markings

💡 Important Concept

Short Pipe Mode preserves customer QoS markings while allowing the Service Provider to use independent QoS policies inside the MPLS core.

2. Customer & Service Provider Agreement

📌 SLA Requirements

• Traffic with Precedence 5 must receive priority treatment
• Priority traffic receives 1 Mbps guaranteed bandwidth
• Traffic with Precedence 3 must be policied to 256 kbps
• SP core internally uses MPLS EXP values

Priority Bandwidth Formula

$$ Priority\\ Bandwidth = \frac{Reserved\\ Bandwidth}{Link\\ Bandwidth} \times 100 $$

Example:

$$ \frac{1Mbps}{10Mbps} \times 100 = 10\% $$

3. Task 1 - Remove Previous Long Pipe Mode Configuration

Before configuring Short Pipe Mode, we must remove the previous Long Pipe Mode QoS policies.

This prevents conflicts between QoS configurations.

Configuration Conflict Formula

$$ Multiple\\ Policies = Undefined\\ QoS\\ Behavior $$

R4 Cleanup Configuration

R4

interface E0/0
 no service-policy input SET-QOS-GROUP

interface E0/3
 no service-policy output USE-QOS-GROUP

no policy-map SET-QOS-GROUP
no policy-map USE-QOS-GROUP

no class-map MPLS-PREC-7
no class-map QOS-PREC-4
no class-map QOS-PREC-7

Detailed Explanation

This configuration removes:

• Input service policies
• Output service policies
• Policy maps
• Class maps

The PE router is now ready for Short Pipe Mode deployment.

Verification Output

R4#show policy-map interface

No policy map is attached

4. Task 2 - Configure MPLS QoS Short Pipe Mode

Now we configure Short Pipe Mode.

Unlike Uniform Mode and Long Pipe Mode:

• We do not work with MPLS EXP bits
• We do not copy QoS values into customer packets
• We directly use customer packet precedence values

Short Pipe QoS Formula

$$ QoS\\ Policy \leftarrow Customer\\ Precedence $$

R4 Short Pipe Mode Configuration

R4

class-map QOS-PREC-3
 match precedence 3

class-map QOS-PREC-5
 match precedence 5

policy-map USE-QOS-GROUP

 class QOS-PREC-3
  police 256000

 class QOS-PREC-5
  priority percent 10

interface E0/3
 service-policy output USE-QOS-GROUP

Detailed Explanation

This policy performs:

• Traffic policing for precedence 3 traffic
• Priority queuing for precedence 5 traffic
• QoS decisions using customer packet markings

No MPLS EXP manipulation occurs on this interface.

💡 Why Use Short Pipe Mode?

Short Pipe Mode allows Service Providers to:

• Maintain internal MPLS QoS policies
• Respect customer packet markings
• Avoid modifying customer traffic
• Keep MPLS QoS hidden from customers

5. Verification Commands

Verify QoS Policies

show policy-map interface

Verify Traffic Counters

show policy-map interface e0/3

Verify Interface Statistics

show interfaces e0/3

Verify MPLS Forwarding

show mpls forwarding-table

Sample QoS Output

R4#show policy-map interface e0/3

Class-map: QOS-PREC-5
 Priority: 10%

Class-map: QOS-PREC-3
 police 256000 bps

6. MPLS QoS Mathematics

Traffic Policing Formula

$$ Allowed\\ Traffic = CIR $$

Where:

$$ CIR = 256000bps $$

Priority Queue Formula

$$ Priority\\ Queue = Reserved\\ Bandwidth $$

Bandwidth Percentage Formula

$$ Bandwidth\\ Percent = \frac{Reserved\\ Bandwidth}{Total\\ Link\\ Bandwidth} \times 100 $$

QoS Classification Formula

$$ Packet\\ Match \rightarrow QoS\\ Class $$

7. QoS Mode Comparison

QoS Mode	Customer Packet Modified?	QoS Source	Use Case
Uniform Mode	Yes	MPLS EXP	End-to-End QoS Visibility
Long Pipe Mode	No	QoS Group	SP Internal QoS
Short Pipe Mode	No	Customer Packet	Customer QoS Preservation

🎯 Short Pipe Mode Summary

• QoS is based on customer packet markings
• MPLS EXP values are ignored on PE-CE egress
• Customer packet markings remain unchanged
• SP QoS remains internal to MPLS core

8. Troubleshooting MPLS QoS Short Pipe Mode

Issue	Cause	Solution
No traffic matching	Wrong precedence value	Verify customer packet markings
Priority queue not working	Policy not applied	Check service-policy attachment
Traffic not policied	Incorrect CIR	Verify police value
Unexpected QoS behavior	Old QoS policies still active	Remove previous configurations
MPLS QoS confusion	Wrong QoS mode understanding	Verify Short Pipe architecture

9. Related Articles

• Complete MPLS L3VPN Configuration Lab Part 1
• Complete MPLS QoS Configuration Lab Part 2
• Complete MPLS QoS Long Pipe Mode Lab Part 3

Final Conclusion

This MPLS QoS Short Pipe Mode Lab Part 4 demonstrated how Service Providers can preserve customer QoS markings while maintaining independent MPLS QoS policies inside the backbone.

We configured:

• QoS cleanup operations
• Short Pipe Mode QoS
• Traffic policing
• Priority Queuing
• Precedence-based QoS classification
• Customer QoS preservation

Understanding MPLS QoS modes is essential for designing scalable Service Provider networks capable of supporting enterprise SLAs and differentiated traffic handling.

This concludes Part 4 of the MPLS VPN and MPLS QoS lab series.