Complete MPLS QoS Long Pipe Mode Configuration Lab Part 3 | Cisco MPLS EXP QoS Tutorial

Complete MPLS QoS Long Pipe Mode Configuration Lab Part 3

In Part 1 we configured the complete MPLS Layer 3 VPN infrastructure including:

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

In Part 2 we implemented MPLS QoS using Uniform Mode.

Now in Part 3 we will implement MPLS QoS using Long Pipe Mode.

🎯 What You Will Learn

• MPLS Long Pipe Mode
• Difference between Uniform and Long Pipe Mode
• QoS Group handling
• Discard-Class usage
• Service Provider QoS preservation
• MPLS EXP handling
• Customer vs SP QoS separation
• Traffic policing and prioritization

Table of Contents

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

1. MPLS QoS Long Pipe Mode Introduction

MPLS QoS Long Pipe Mode is a Service Provider QoS model where:

• SP QoS markings remain inside the provider network
• Customer packet markings are not modified
• QoS decisions are based on internal MPLS QoS markings

Long Pipe Mode Logic

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

This allows Service Providers to:

• Maintain independent internal QoS policies
• Protect backbone QoS architecture
• Avoid exposing internal QoS policies to customers

💡 Key Long Pipe Mode Concept

Unlike Uniform Mode, Long Pipe Mode does NOT copy SP MPLS EXP values back into customer packets.

2. Customer & Service Provider Agreement

📌 SLA Requirements

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

Bandwidth Reservation Formula

$$ Reserved\\ Bandwidth = \frac{Priority\\ Traffic}{Total\\ Bandwidth} \times 100 $$

Example:

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

3. Task 1 - Remove Previous Uniform Mode Configuration

Before implementing Long Pipe Mode, we must remove the Uniform Mode QoS configuration from R4.

This prevents policy conflicts and ensures clean QoS behavior.

Why Remove Previous Policies?

$$ Old\\ Policy + New\\ Policy = Conflict $$

Removing unused QoS policies is a best practice in production networks.

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

Detailed Explanation

This removes:

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

The router is now ready for Long Pipe Mode deployment.

Expected Verification Output

R4#show policy-map interface

No policy map is attached

4. Task 2 - Configure MPLS QoS Long Pipe Mode

Now we configure Long Pipe Mode.

The MPLS EXP markings will:

• Be copied into QoS Groups
• NOT be copied into customer packets
• Be used internally for SP QoS enforcement

Long Pipe QoS Formula

$$ MPLS\\ EXP \rightarrow QoS\\ Group $$

But:

$$ MPLS\\ EXP \not\rightarrow Customer\\ Packet $$

Step 1 - Copy MPLS EXP to QoS Group

R4

class-map MPLS-PREC-4
 match mpls experimental topmost 4

class-map MPLS-PREC-7
 match mpls experimental topmost 7

policy-map SET-QOS-GROUP

 class MPLS-PREC-4
  set qos-group mpls experimental topmost
  set discard-class 4

 class MPLS-PREC-7
  set qos-group mpls experimental topmost
  set discard-class 7

interface E0/0
 service-policy input SET-QOS-GROUP

What is Discard-Class?

Discard-Class is an internal QoS marking used during congestion.

It helps routers decide:

• Which packets to drop first
• Which packets to protect
• Congestion management priority

Congestion Drop Logic

$$ Higher\\ Discard\\ Class \rightarrow Lower\\ Drop\\ Probability $$

Step 2 - Use QoS Group for SP QoS Policy

R4

class-map QOS-PREC-4
 match qos-group 4

class-map QOS-PREC-7
 match qos-group 7

policy-map USE-QOS-GROUP

 class QOS-PREC-4
  police 128000

 class QOS-PREC-7
  priority percent 10

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

Important Long Pipe Behavior

Notice:

No "set precedence qos-group"

This means:

• SP QoS remains internal
• Customer packet headers are untouched
• MPLS QoS is invisible to customers

💡 Why Long Pipe Mode is Important

Many Service Providers prefer Long Pipe Mode because it keeps provider QoS architecture independent from customer QoS markings.

5. Verification Commands

Verify QoS Policies

show policy-map interface

Verify MPLS Labels

show mpls forwarding-table

Verify QoS Groups

show policy-map interface e0/0

Verify Discard-Class

show queueing interface

Sample QoS Output

R4#show policy-map interface e0/3

Class-map: QOS-PREC-7
 Priority: 10%

Class-map: QOS-PREC-4
 police 128000 bps

6. MPLS QoS Mathematics

Traffic Policing Formula

$$ Allowed\\ Rate = CIR $$

Where:

$$ CIR = 128000bps $$

Priority Queue Formula

$$ Priority\\ Queue = Guaranteed\\ Bandwidth $$

QoS Group Mapping

$$ QoS\\ Group = MPLS\\ EXP $$

Example:

$$ EXP\\ 7 \rightarrow QoS\\ Group\\ 7 $$

MPLS EXP Capacity

$$ 2^3 = 8 $$

EXP values:

$$ 0-7 $$

7. Uniform Mode vs Pipe Mode vs Long Pipe Mode

QoS Mode	Customer Packet Modified?	SP QoS Internal?	Use Case
Uniform Mode	Yes	No	End-to-End QoS Visibility
Pipe Mode	No	Yes	SP QoS Isolation
Long Pipe Mode	No	Yes	Advanced SP QoS

🎯 Long Pipe Mode Summary

• MPLS EXP values remain internal
• QoS Groups preserve SP markings
• Customer packets remain unchanged
• SP maintains independent QoS architecture

8. Troubleshooting MPLS QoS Long Pipe Mode

Issue	Cause	Solution
No QoS matching	Wrong EXP bits	Verify EXP marking
QoS Group missing	Policy not applied	Verify service-policy
Traffic not prioritized	Class-map mismatch	Check QoS Group values
Unexpected packet marking	Uniform Mode leftover config	Remove old policies
Policer not working	Wrong CIR value	Verify policing rate

9. Related Articles

• Complete MPLS L3VPN Configuration Lab Part 1
• Complete MPLS QoS Configuration Lab Part 2
• Complete MPLS QoS Short Pipe Mode Configuration Lab on Cisco IOS | MPLS VPN QoS Part 4

Final Conclusion

This MPLS QoS Long Pipe Mode Lab Part 3 demonstrated how Service Providers can preserve internal QoS policies without exposing QoS markings to customers.

We configured:

• QoS cleanup operations
• MPLS EXP classification
• QoS Group handling
• Discard-Class configuration
• Traffic policing
• Priority Queuing
• Long Pipe Mode QoS

Understanding MPLS QoS modes is critical for designing scalable Service Provider backbones that support differentiated services and SLA enforcement.

This concludes Part 3 of the MPLS VPN and MPLS QoS configuration series.