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8/10/2019 Orckit-Corrigent MPLS-TP Technical Note 1212

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Technical NoteMPLS-TP

Jan. 2011


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Table of contents

Introduction 3

MPLS-TP Overview 4-5

The need for MPLS-TP 6MPLS-TP OAM 7-8

MPLS-TP Survivability 9

MPLS-TP control plane and management 10

Orckit-Corrigent MPLS-TP value proposition 11-12

Migration to MPLS-TP 13

Summary 14

List of figures

Figure #1: MPLS-TP evolution 6

Figure #2: CCM Flow 7

Figure #3: Orckit-Corrigent IP/MPLS and MPLS-TP interworking 12


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Introduction

The Multiprotocol Label Switching Transport Profile (MPLS -TP) is a packet

transport technology that leverages benefits from the existing MPLS

networking infrastructure, and improves the efficiency and effectiveness of

packet transport networks, while maintaining the mandatory Operation

Administration and Maintenance (OAM) capabilities of legacy SONET/SDH

networks.

This technical note provides information on MPLS-TP technologies andimplementation in Orckit-Corrigents Packet Transport Network (PTN)

solutions.


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MPLS-TP Overview

MPLS-TP is based on a subset of MPLS technologies with additionaltransport functionalities, as in traditional transport networks, making it a

reliable, scalable, and cost optimized packet-based transport technology.

MPLS-TP introduces additional transport functionalities such as

comprehensive OAM capabilities, survivability, data-plane/control-plane

separation, and static provisioning of bidirectional services. This is in addition

to well-accepted MPLS functionalities such as Quality of Service (QoS),

scalability, traffic engineering and Layer 2 packet forwarding. The result is the

ability to provide network operators with full control over their packet

networks.

MPLS-TP Functionalities

MPLS-TP includes the following main functionalities defined by Internet

Engineer Task Force (IETF) and International Telecommunications UnionTelecommunications Standardization Sector (ITU-T) standardization bodies

Bidirectional Label Switch Path (LSP)

o Transmit and receive traffic following the same path throughout

the network

Enhanced OAM tools

o Continuity Check (CC) for fast failure detection

o Alarm Indication Signal (AIS) for fault isolation

o Remote Defect Indication (RDI) for fault isolation

o Loopback (LB), similar to IP ping, for basic maintenance

o Loss/delay measurement for detection of performance

degradation

End-to-end Protection

o 1:1 bidirectional end-to-end protection scheme triggered by

OAM


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o Sub 50ms linear protection

o Pseudo wire (PW) and LSP protection

Control plane options

o Separation from the data plane

o Static or dynamic LSP configuration

MPLS-TP in the standardization bodies

The IETF and the ITU-T teams agreed to work together on the design of

MPLS-TP, in order to bring transport network requirements to the existing

MPLS technology.

The Joint Working Group (JWT) focuses on the following main categories

General requirements

OAM

Survivability

Network management

The JWT started their work in March 2008. The first draft was published in

July 2008 and the final agreement is expected at the end of 2011.


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The need for MPLS-TP

The increasing growth of packet-based traffic is driving the need for evolved

transport networks. The next generation transport technologies should

leverage the same benefits of legacy transport in terms of end-to-end

determinism, OAM, high availability, high reliability, and easy to use

management.

IP/MPLS

SONET/SDH

MPLS-TP

P a c k e t e f f i c i e n c y

T r a n s p o

r t r e l i a b i

l i t y

IP/MPLS

SONET/SDH

MPLS-TP

P a c k e t e f f i c i e n c y

T r a n s p o

r t r e l i a b i

l i t y

Figure #1: MPLS-TP evolution


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MPLS-TP OAM

MPLS-TP OAM provides the same OAM concepts and methods which areavailable in legacy transport networks, including

Fast failure detection

Alarm suppression

Remote defect indication

Protection switching

OAM packets are carried on Generic Associated channel (G-Ach).

OAM and data packets are carried on the same path, therefore enabling

simpler and faster monitoring of the PW and LSP layers.

MPLS-TP OAM introduces the functional components, Maintenance End

Point (MEP) and Maintenance Intermediate Point (MIP), which enable running

OAM packets between two end points, such as:

1. Continuity checks (CC) messages allowing fast detection of lost of

connectivity, as well as connection mis-configuration.

The CC messages are sent periodically by MEP and monitored for Loss Of

Continuity (LOC) by each MEP/MIP.

The transmission interval can be set to a minimum of 3.3 ms, allowing forvery fast-failure detection.

Figure #2: CCM Flow


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2. Delay and Loss Measurements (DM/LM) allowing the detection of

performance degradations.

3. Loopback (LB) messages allowing on-demand bidirectional diagnostic

test for connectivity check and failure localization.

4. Alarms suppress enabling fault localization while avoiding unnecessary

alarms propagation. AIS and RDI are sent to the remote sides in case of

LOC detection.


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MPLS-TP Survivability

MPLS-TP provides similar protection switching mechanisms which are used inlegacy SONET/SDH transport networks, including

End to end linear protection for LSP, PW and Multi Segment PW (MS-

PW) layers

Protection State Coordination (PSC) mechanism to synchronize the

both ends on protection status and commands

Sub-50 ms protection in case of failure in the data plane (relying on

OAM messages transmission at 3.3 ms rate)

Manual protection commands e.g. manual switch, lockout, clear

Provides architecture of 1+1 and 1:1 protection schemes

Protection switching is triggered upon Signal Fail (i.e. LOC) or Signal

Degrade (SD) or manual commands

All these mechanisms provide enhanced LSP/PW/MS-PW end- to-end

protection, ensuring network reliability and high availability.


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MPLS-TP control plane and management

The control plane in MPLS-TP is the mechanism used for provisioningLSPs/PWs dynamically over the packet network. The control plane is optional

and separated from the data plane. A failure of the control plane will not

create any kind of data plane failure.

When no control plane is used, operators can set up LSPs and PWs statically

using a Network Management System (NMS), similar to the way it is done in

legacy transport networks, without IP or routing protocols.

In the dynamic approach, a control plane is used. LSPs and PWs creation is

done by Generalize MPLS (GMPLS) and Targeted Label Distribution Protocol

(T-LDP).


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Figure #3: Orckit-Corrigent IP/MPLS and MPLS-TP interworking

Together with the dual stacking of IP/MPLS and MPLS-TP, Orckit-Corrigent

CM-4000 offers a centralized NMS (CM-View) with a Path Computation

Element (PCE), Traffic Engineering Database (TED) and Call Admission

Control (CAC). This solution enables

Automatic provisioning of LSPs considering Traffic Engineering (TE)

properties such as Class of Service (CoS) and bandwidth

Understanding the relationship between network resources and LSPs

Creation of manual or automatic explicit route

Support of a disjointed path for LSP/PW protection


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Migration to MPLS-TP

Service providers who wish to deploy a new packet-based transport network

based on MPLS-TP technology are facing a dilemma of which technology to

use as a stepping stone until MPLS-TP will be ratified. Such intermediate step

should take into account the complexity and the cost of migrating at the end to

MPLS-TP. There are 2 options for such intermediate step:

1. T-MPLS technology

2. IP/MPLS Technology

In the first option, the T-MPLS which is a non-standard technology is

positioned as a stepping stone to MPLS-TP. The assumption is that since T-

MPLS is the basic of MPLS-TP, the migration in the future will only be a

software upgrade, but since the MPLS-TP standard still has a long way to go,

there is a risk that service providers will end up with a complicated and

expensive migration.

In the second approach, the service providers can choose the IP/MPLStechnology as a step towards the MPLS-TP, the IP/MPLS is field-proven and

a de-facto standard unlike T-MPLS.

In such approach the service providers will eliminate the risk of using a non-

standard technology and in addition they will have the ability to migrate only

part of their IP/MPLS network to MPLS-TP due to the interworking between

the 2 technologies.

Orckit-Corrigent CM-4000 products support both IP/MPLS and MPLS-TP

simultaneously making the migration process smooth and cost-efficient

enabling service providers to migrate to the standardized MPLS-TP by using a

software upgrade only and saving the cost of new hardware.


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Summary

MPLS-TP brings transport characteristics such as OAM, survivability and

management to the MPLS domain, while preserving its flexibility and

scalability.

Orckit-Corrigents CM-4000 PTN solutions support IP/MPLS and MPLS-TP

simultaneously, and by doing this enable the service provider a smooth

migration from IP/MPLS to MPLS-TP as well as interoperability between the

two technologies.

Orckit-Corrigent actively participates in the MPLS-TP standardization efforts

and its CM-4000 products already support MPLS-TP. The CM-4000 MPLS

and MPLS-TP interoperability was demonstrated at Carrier Ethernet World

Congress, Warsaw during September 2010.


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Acronyms

AIS Alarm Indication Signals

CAC Connection Admission Control

CC Continuity Check

CESoPSN Circuit Emulation Service over Packet SwitchingNetworks

G-Ach Generic Associated channel

GMPLS Generalize Multi Protocol Label Switching

IETF Internet Engineer Task Force

IP Internet Protocol

JWT Joint Working Group

LB Loopback

LM Loss Measurements

LOC Loss Of Continuity

LSP Label Switch Path

MEP Maintenance End Point

MPLS Multi Protocol Label Switching

MPLS-TP Multi Protocol Label Switching Transport Profile

NMS Network Management System

OAM Operation, Administration, Maintenance

PCE Path Computation Element

PSC Protection State Coordination

PTN Packet Transport Network

PW Pseudo wire

QoS Quality of Service

RDI Remote Defect Indications


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SD Signal Degrade

SDH Synchronous Digital Hierarchy

SONET Synchronous Optical Networking

TE Traffic Engineering

TED Traffic Engineering Database

T-LDP Targeted Label Distribution Protocol

TP Traffic Profile


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