MPLS-TP: Where Are We? - IEEE Boston Section

MPLS-TP: Where Are We? 

Andrew G. Malis, PMTS 

Verizon Communications 

March 6, 2012 

OFC/NFOEC 

1

• Introduction to MPLS & MPLS-TP 

• MPLS-TP Functionality 

• MPLS-TP Deployment Scenarios 

• MPLS-TP Standardization Status 

• MPLS-TP Interoperability Testing 

Agenda 

2

• Multi-Protocol Label Switching 

What is MPLS? 

• Defined by Internet Engineering Task Force 

(IETF) beginning in 1998 

• A combination of: 

– A forwarding mechanism (label switching) 

– Connection (LSP - label switched path) establishment 

protocols (LDP, RSVP-TE) 

– Defined mappings onto Layer 2 technologies (PPP/ 

POS, Ethernet, ATM, Frame Relay) 

– OAM (Operations, Administration, and Maintenance) 

– Data path protection (fast reroute) 

3

IP 

Packet 

LER 

MPLS Label Forwarding Example 

Label 1 

IP 

Packet 

Label-Switched Path 

(LSP) 

LSR 

Label 2 

IP 

Packet 

Label 3 

IP 

Packet 

IP Forwarding LABEL SWITCHING 

IP Forwarding 

LSR 

LER 

IP 

Packet 

4

• IP Traffic Engineering 

• Layer 3/IP Virtual Private Networks 

IP/MPLS Applications 

• Pseudowires to transport layer 1 and layer 2 services 

(Ethernet, Frame Relay, ATM, TDM) over IP networks 

• Layer 2 VPNs (esp. Ethernet aka Virtual Private LAN 

Service) 

• Service provider network convergence 

• Widely used by almost every major IP service provider in 

the world for one more of these applications 

• Has created billions of dollars in revenue for service 

providers annually 

5

What is MPLS-TP? 

• MPLS-TP (MPLS Transport Profile) was created as a result of 

the majority of traffic in today’s networks being packet based 

(primarily IP and Ethernet), rather than circuit (TDM) based. 

• It is a subset (or profile) of MPLS (Multiprotocol Label 

Switching) that is suitable for use in packet-based optical 

transport networks. 

– Doesn’t use some IP/MPLS features that are unnecessary in a transport 

context, primarily native IP line-rate forwarding and features used to 

optimize IP routing over MPLS LSPs 

• Because it brings statistical packet switching to the transport 

layer of the network, it provides a much more efficient 

transport of packet traffic than the traditional mapping of 

packets into TDM transport circuits. 

• It enables optimization of packet transport to reduce overall 

network cost, allowing a more economical and efficient 

network infrastructure 

6

MPLS-TP Objectives 

• Enables MPLS to be deployed in a transport network and 

operated in a similar manner to existing transport 

technologies 

• Enables packet-based transport services with a similar 

degree of predictability, reliability and OAM to that found 

in TDM-based transport networks 

• Enables connection-oriented optical packet transport 

based on widely-deployed MPLS protocols, with 

transport-grade performance and operation similar to 

existing transport networks; ensures compatibility with IP/ 

MPLS 

7

Data Mobile Voice 

Services & 

Applications 

§� Multiple layers, separate single 

function networks 

§� Complicated service and network 

transformation 

§� Multiple single services 

§� Circuit-based transport 

IP and Ethernet Services Drive 

Network Transformation 

Multiple Legacy Networks Converged Infrastructure 

IP FR/ATM TDM PSTN 

E thernet 

POS 

ATM 

SONET/SDH 

WDM 

OSS / BSS OSS / BSS OSS / BSS 

Services & 

Applications 

SONET/SDH 

Services & 

Applications 

Wireline and 

Wireless 

Access 

Services and Applications 

OSS / BSS 

Multi-Services 

Aggregation 

and Core 

§� Converged multi-function network 

§� Easily enables service and network 

transformation 

§� Multi-service convergence 

§� Packet-enabled transport 

• Network Layers 

L2, IP, 


Packet 

Transport 

ETH, OTN 

Flexible 

Services 

Intelligent 

scaling and 

Traffic 

Engineering 

OSS: Operation Support System 

BSS: Business Support System 

8

MPLS-TP Network Model 

Connec&on Oriented, pre-‐determined working path and protect path. 

Transport Tunnel 1:1 protec&on, switching triggered by in-‐band OAM. 

Op&ons with NMS for sta&c provisioning, or dynamic control plane for rou&ng and signaling. 

9






Agenda 

10

ECMP 

MP2P LDP 

PHP 

MPLS-TP Compared With IP/MPLS 

IP/MPLS in L3 

networks 


MPLS Transport Profile 

Subset to meet transport 

network operational 

requirements 

• MPLS/PWE3 architecture 

• MPLS forwarding 

• GMPLS/PWE3 control plane 

Additional 

functionality based 

on transport 

requirements (next 

page) 

11

Additional Functionality Based on 

Transport Requirements 

Transport-like OAM 

• In-band OAM channels 

• Performance monitoring for SLA verification 

• Tandem connections and multi-level operation 

• Wire-speed operation 

• Alarms and AIS 

Transport-like Resilience 

• Sub-50ms protection switching 

• Linear protection 

• Ring protection 

•Shared Mesh protection 

Addi&onal 

func&onality 

Transport- like Operation 

• Operation through NMS or 

control plane 

• Static provisioning 

• Traffic Engineering rules 

Addi$onal features for standard IP/MPLS routers & Op$cal Packet Transport equipment; 

enhanced interoperability between service rou$ng and op$cal transport 

12

Data Plane 

OAM 

– MPLS Forwarding 

– Connection-oriented Unidirectional and 

Bidirectional P2P and P2MP LSPs 

– Pseudowires to carry L2/L1 services (Ethernet, 

ATM, FR, Emulated TDM and SONET) 

– In-band OAM channel (GACH) 

– Connectivity Check (CC): proactive (ext. BFD) 

– Connectivity Verification (CV): reactive (ext. LSP 

Ping) 

– Alarm Suppression and Fault Indication with AIS, 

RDI, and Client Fault Indication (CFI) 

– Performance monitoring, proactive and reactive 

MPLS-TP Functionality 

Control Plane 

– NMS provisioning option 

– GMPLS control plane option 

– PW control plane option 

Resiliency 

– Sub-50ms protection switch over 

without c/p 

– 1:1, 1+1, 1:N path protection 

– Linear protection 

– Ring protection 

– Shared Mesh protection 

13

Why not just use Ethernet-based 

Transport? 

• MPLS-TP over GFP framing is more efficient on the wire than Ethernet 

framing 

• MPLS-TP uses an infinitely hierarchical label stack, which allows multilayer 

operation with clean separation between layers 

• MPLS-TP allows both static configuration of connections and 

dynamically signaled paths using the GMPLS control plane 

• MPLS-TP allows bandwidth to be reserved to connections, supports a 

rich set of QoS parameters, and includes 50ms restoration from outages 

• For Verizon and many other ISPs, MPLS-TP allows a graceful migration 

from the current IP/MPLS over SONET/SDH backbone, which uses 

MPLS Traffic Engineering (MPLS-TE) with a dynamic control plane to 

set up MPLS connections (label-switched paths, aka LSPs) 

• MPLS-TP LSPs can be unidirectional or bi-directional, and can be 

routed using a link-state routing protocol in the network elements, or via 

an offline network planning system 

14






Agenda 

15

Scenario 1: Dynamic MPLS-TP over OTN/DWDM 

• MPLS-TP provides transport services for many client networks 

• Ethernet services (native and Ethernet/MPLS) network: Inter-switch/router links, Ethernet tunnels transport 

• IP MPLS services network: Inter-outer IP links transport 

• Enterprises: Leased line replacement 

• Ethernet pseudowires over MPLS-TP LSPs will be used for backbone router interconnection 

• Islands of a client services network form a contiguous domain (e.g., IGP domain) 

• Client-transport network interface is a UNI 

16

Scenario 2: TDM Replacement with MPLS- 

TP Aggregation and Access 

17






Agenda 

18

History 

• MPLS standardized in the Internet Engineering Task Force 

beginning in 1998, and still continuing new features and extensions 

• Around 2006, ITU-T Study Group 15 (where SONET/SDH, OTN, and 

optical transport networks are standardized) began working on 

packet-based transport switching based on MPLS labels, called T- 

MPLS (aka G.8114). 

• Unfortunately, T-MPLS had some technical flaws and was in 

incompatible with IETF MPLS; also violated the IETF’s MPLS 

change process 

• In late 2007, the IETF leadership began working with SG15 

leadership to “fix” T-MPLS and make it compatible with IETF MPLS. 

The result was an MPLS-TP joint project begun in early 2008. G. 

8114 was killed, and a new process began where the SG15 would 

generate MPLS-TP requirements, while the IETF would generate 

protocol specifications based on ITU-T requirements 

19

MPLS-TP Standardization Process 

(Agreement between IETF and ITU-T SG 15) 

• IETF developing a set of MPLS-TP specifications with requirements from SG15 

• SG15 produces updated recommendations to replace G.8114 that largely refer to 

IETF RFCs 

OAM 

(MPLS WG) 

Requirements 

(ITU-T) 

Transport Profile Architectural Framework 

(IETF MPLS WG) 

Pseudowires 

(PWE3 WG) 

Survivability 


Control Plane 

(CCAMP WG) 

Network Management 


20

General 

Description Focus Area IETF RFC or WG documents 

JWT document JWT Report on MPLS-TP Architectural 

Considerations 

IAB document Uncoordinated Protocol Dev. 

Considered Harmful 

First milestone on MPLS-TP Joint 

work by IETF/ITU-T 

RFC 5317 

Inter-SDO coordination RFC 5704 

General MPLS-TP Terminology Terminology draft-ietf-mpls-tp-rosetta-stone 

Requirements 

IETF MPLS-TP General Definitions 

Requirements and Frameworks 

Description and Focus Area IETF RFC or WG documents 

General MPLS-TP Requirements. RFC 5654 

MPLS-TP OAM Requirements RFC 5860 

MPLS-TP Network Management Requirements RFC 5951 

Frameworks MPLS-TP Architecture Framework RFC 5921 

MPLS-TP Network Management Framework RFC 5950 

MPLS-TP OAM Architecture Framework RFC 6371 

MPLS-TP Survivability Framework RFC 6372 

MPLS-TP Control Plane Framework RFC 6373 

MPLS-TP OAM Analysis draft-ietf-mpls-tp-oam-analysis 

21

MPLS-TP Protocols for Forwarding and Protection 

Function IETF RFC or WG documents 

Data Plane MPLS-TP Identifiers conformant to existing 

ITU and compatible with existing IP/MPLS 

MPLS Label Stack Entry: 

"EXP" renamed to "Traffic Class" 

IETF MPLS-TP Data Plane, 

Protection Definitions 

MPLS Generic Associated Channel for In-band 

OAM and control 

In-Band Data Communication for the MPLS- 

TP 

RFC 6370 

RFC 5462 

RFC 5586 

RFC 5718 

MPLS TP Data Plane Architecture RFC 5960 

MPLS-TP UNI-NNI RFC 6215 

Protection MPLS-TP Linear Protection RFC 6378 

MPLS-TP MIB Management 

Function IETF RFC or WG documents 

Management MPLS-TP MIB management overview draft-ietf-mpls-tp-mib-management-overview 

22

Proactive FM OAM 

Functions 

On demand FM 

OAM Functions 

Proactive PM OAM 

Functions 

and 

On demand PM 

OAM 

Functions 

IETF MPLS-TP OAM (FM and PM) 

Definitions 

MPLS-TP Fault Management (FM) OAM Functions 

OAM Functions Protocol Definitions IETF WG documents 

MPLS-TP Identifiers conformant to existing 

ITU and compatible with existing IP/MPLS 

Identifiers RFC 6370 

Remote Defect Indication (RDI) Bidirectional Forwarding Detection 

(BFD) extensions 

RFC 6428 

Alarm Indication Signal (AIS) AIS message under G-Ach RFC 6427 

Link Down Indication (LDI) Flag in AIS message 

Lock Report (LKR) LKR message under G-Ach 

Config MPLS-TP OAM using LSP Ping LSP-Ping draft-ietf-mpls-lsp-ping-mpls-tpoam-conf 

Continuity Verification (CV) LSP Ping and BFD Extensions RFC 6426 

Loopback (LBM/LBR) 1) In-band Loopback in G-Ach 

or 2) LSP Ping extensions 

Lock Instruct (LI) In-band Lock messages in G-ACh 

MPLS-TP Performance Management (PM) OAM Functions 

RFC 6436 

OAM Functions Protocol definitions IETF WG documents 

Packet loss measurement (LM) LM and DM query messages RFC 6374 

RFC 6375 

Packet delay measurement (DM) LM and DM query messages 

Throughput measurement Supported by LM 

Delay Variation measurement Supported by DM 

23

Controversy and Politics 

• The joint project continued well for about a year 

• However, some vendors one large mobile operator had already 

implemented and deployed a pre-standard version of G.8114/T-MPLS 

– Primary difference from IETF MPLS-TP is the OAM 

– IETF MPLS-TP OAM based on existing MPLS constructs 

– G.8114/T-MPLS OAM based on Ethernet OAM (Y.1731), cannot support full 

range of MPLS-TP requirements and functionality, but works in this 

particular deployment 

– These vendors and operator continued to push for Y.1731-based OAM to be 

an option for MPLS-TP, supported by their governments at ITU-T 

– ITU-T decided to produce two MPLS-TP OAM specifications, G.8113.1 for 

Y.1731-based OAM and G.8113.2 for IETF-based OAM 

– IETF’s official position is that one OAM is sufficient and an optional second 

OAM is technically unnecessary, makes equipment and network 

deployments more complex, and introduces a new interworking function 

• Mismatch in IETF and ITU-T processes haven’t helped the controversy 

• You may have seen dueling press releases and articles at Light Reading 

on the controversy 

24

Recommendations In Progress in 

ITU-T SG 15 

• ITU-T Recommendations in progress: 

– G.8110.1, MPLS-TP architecture 

– G.8113.1, Y.1731-based OAM for MPLS-TP 

– G.8113.2, IETF-based OAM for MPLS-TP 

– G.8121, MPLS-TP network element functional modeling 

• .1 and .2 versions to correspond with both OAM types 

– G.8131, MPLS-TP protection 

– G.8151, MPLS-TP network element management 

• These documents are for the most part expected to complete by YE 

2012 

• G.8113.1 is currently written using an “experimental” MPLS OAM 

codepoint; ITU-T has requested an official permanent codepoint 

allocation. This request is at the heart of the disagreement between 

the two organizations, and continues to be discussed 

25

Current Status 

§� Some 20 IETF RFCs published; initial round of work largely complete 

§� Some additional features (e.g. shared mesh protection) still in progress 

§� ITU-T SG15 continues to standardize it’s own Y.1731-based OAM as an optional 

alternative to IETF MPLS-based OAM 

26






Agenda 

27

MPLS-TP Function Functional Verification Interoperability 

LSPs and PW encapsulation G-Ach/GAL encapsulation 

Control Word (CW) inclusion 

LSPs and PW establishment Static label assignment 

Dynamic provisioning 

OAM: Continuity Check (CC) & 

Connectivity Verification (CV) 

On-demand Alarm Generation 

and Fault Notification 

Automatic Protection Switching 

(APS) 

MPLS-TP and MPLS 

Interworking 

OAM message generation @ various 

intervals 

Failure detection 

On-demand LSP connectivity verification 

Alarm generation and detection 

Generation of AIS/LDI/LCK/PW Status 

Auto generation of RDI 

CCCV Pause/Resume 

Ingress, Egress and Transit Node 

Different protection modes 

OAM status translation 

CW handling 

MPLS-TP Functional and 

Interoperability Testing 

Message exchange (correct encoding and 

interpretation) 

Label switching 

Interoperability of static SS-PW 

and dynamic SS-PW 

Label space compatible 

OAM message exchange 

CC/CV sessions established 

Ping encoding follows G-ACh Channel Type 

+ Echo or G-ACh Channel Type + IP/UDP/ 

Echo? 

Alarm encoding and interpretation 

AIS suppression state 

Alarm propagation 

PSC interoperability 

Switchover time measurements per LSP/ 

PW 

End to end service verification 

MS-PW (mix of MPLS-TP and IP/MPLS 

segments) 

28

Example Test Case: Protection 

Switching 

DUT is responsible for detecting 

failures and forcing switchover 

Egress PE: 

1. Respond to manual 

switchover command 

2. Terminate MPLS-TP OAM 

3. Terminate BFD 

4. Terminate Traffic 

5. Simulate CC/CV error and 

trigger DUT to switchover 

6. Simulate link failure and 

Key use cases to test: 

trigger DUT to switchover 

1. MPLS-TP OAM interoperability 

2. BFD Interoperability 

3. PSC interoperability 

4. Validate APS commands and performance 

5. Per LSP or PW Switchover time measurement based on traffic loss 

6. < 50 ms switchover time in various protection mode 

29

Protection Switching Test Results 

30

§� Performance Verification and Benchmarks 

• Can MPLS-TP deliver carrier grade services? 

§� Scale: service scale of LSP/PW 

§� Reliability: protection switching, recovery sub 50ms 

§� CoS: deliver service levels to meet SLAs 

§� Performance: traffic forwarding, low latency, low delay variation (jitter) 

§� Management: OAM (active and on demand) and MIB support 

• Support static provisioning via NMS 

• Support dynamic provisioning 

Additional Areas For Testing 

• Scalability Test Case : 

What is the maximum PW/ 

LSP capacity? 

31

MPLS-TP Public Interop Testing 

MPLS 2010 Conference Public Interoperability Demo (October 2010) 

• MPLS-TP static LSP establishment 

• MPLS-TP data plane verification 

• Exchange BFD CC messages 

• Use of BFD CC to identify failures 

• Functionality of protection modes 

First multi-vendor standards-based MPLS-TP interoperability testing 

32


§� MPLS and Ethernet World Congress (Feb 2011) Public 

Multi-Vendor Interoperability Test and Public Showcase 

Test validates interworking between transport domains 

33

Cisco & Ixia Demo in Verizon Lab: 

Sub-50 msec Failover (March 2011) 

34

was tested. For some test areas, results from Isocore 

spring LEC event are also presented to demonstrate the 

evolving implementations as standards become stable, 

MPLS-TP being one of the classic examples. 

Figure 2 shows the comprehensive setup highlighting 

the roles played by all participating nodes and logical 

representation of the network physical topology. 


MPLS 2011 Conference Public Interoperability Demo (October 2011) 

Figure 2: Logical Representation of MPLS2011 Demo 

Network 

• Statically provisioned co-routed 

LSPs 

• Linear Protection 

• MPLS-TP OAM - including BFD 

connectivity check (CC) and LSP 

Ping using ACH 

• BGP based multicast VPN (BGPmVPN) 

• MPLS services over 100G 

connections 

35

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• IETF Documents 

MPLS-TP Resources 

– MPLS-TP Requirements: http://datatracker.ietf.org/doc/rfc5654/ 

– MPLS-TP OAM Requirements: http://datatracker.ietf.org/doc/rfc5860/ 

– MPLS-TP Framework: http://datatracker.ietf.org/doc/rfc5921/ 

– MPLS-TP Data Plane Architecture: 

http://datatracker.ietf.org/doc/rfc5960/ 

• Isocore Public Reports: http://www.isocore.com/ 

• EANTC Public Reports: http://www.eantc.de/ 

• Light Reading MPLS-TP Briefing Center: 

http://www.lightreading.com/mplstp/ 

– MPLS-TP News & Analysis 

– Whitepaper and Webinar Archive: MPLS-TP in Next-Generation 

Transport Networks (July 2011) 

37

Questions? 

38

MPLS-TP: Where Are We? - IEEE Boston Section

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