Orckit-Corrigent MPLS-TP Technical Note 1212

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



    Technical NoteMPLS-TP

    Jan. 2011

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



    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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    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


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


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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


    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


    End-to-end Protection

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


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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



    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





    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




    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 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


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

    management to the MPLS domain, while preserving its flexibility and


    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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    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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