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MPLS Transport Profile (MPLS-TP) Applicability: Use Cases and Design

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 6965.
Authors Luyuan Fang , Dr. Nabil N. Bitar , Raymond Zhang , Masahiro Daikoku , Ping Pan
Last updated 2015-10-14 (Latest revision 2013-05-01)
Replaces draft-fang-mpls-tp-use-cases-and-design
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Informational
Additional resources Mailing list discussion
Stream WG state WG Document
Document shepherd Loa Andersson
Shepherd write-up Show Last changed 2013-01-28
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INTERNET-DRAFT                                              L. Fang, Ed.
Intended Status: Informational                                     Cisco
Expires: November 1, 2013                                       N. Bitar
                                                                R. Zhang
                                                          Alcatel Lucent
                                                              M. Daikoku
                                                                  P. Pan

                                                             May 1, 2013

             MPLS-TP Applicability; Use Cases and Design  


   This document provides the applicability of Multiprotocol Label
   Switching Transport Profile (MPLS-TP) with use case studies and
   network design considerations. The use cases include Metro Ethernet
   access and aggregation transport, Mobile backhaul, and packet optical

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at


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Copyright and License Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   described in the Simplified BSD License.

Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2. Background  . . . . . . . . . . . . . . . . . . . . . . . .  4
   2. MPLS-TP Use Cases . . . . . . . . . . . . . . . . . . . . . . .  6
     2.1. Metro Access and Aggregation  . . . . . . . . . . . . . . .  6
     2.2. Packet Optical Transport  . . . . . . . . . . . . . . . . .  7
     2.3. Mobile Backhaul . . . . . . . . . . . . . . . . . . . . . .  7
       2.3.1. 2G and 3G Mobile Backhaul . . . . . . . . . . . . . . .  8
       2.3.2. 4G/LTE Mobile Backhaul  . . . . . . . . . . . . . . . .  8
   3. Network Design Considerations . . . . . . . . . . . . . . . . .  9
     3.1. The role of MPLS-TP . . . . . . . . . . . . . . . . . . . .  9
     3.2. Provisioning mode . . . . . . . . . . . . . . . . . . . . .  9
     3.3. Standards compliance  . . . . . . . . . . . . . . . . . . . 10
     3.4. End-to-end MPLS OAM consistency . . . . . . . . . . . . . . 10
     3.5. PW Design considerations in MPLS-TP networks  . . . . . . . 11
     3.6. Proactive and on-demand MPLS-TP OAM tools . . . . . . . . . 11
     3.7. MPLS-TP and IP/MPLS Interworking considerations . . . . . . 12
   4. Security Considerations . . . . . . . . . . . . . . . . . . . . 12
   5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 12
   6. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 12
   7. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     7.1. Normative References  . . . . . . . . . . . . . . . . . . . 13
     7.2. Informative References  . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
   Contributors' Addresses  . . . . . . . . . . . . . . . . . . . . . 15


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1. Introduction

   This document provides applicability, use case studies and network
   design considerations for the Multiprotocol Label Switching Transport
   Profile (MPLS-TP). 

1.1. Terminology

      Term     Definition
      ------   ------------------------------------------------------- 
      2G       2nd generation wireless telephone technology 
      3G       3rd generation of mobile telecommunications technology
      4G       4th Generation Mobile network 
      ADSL     Asymmetric Digital Subscriber Line 
      AIS      Alarm Indication Signal
      ASNGW    Access Service Network Gateway
      ATM      Asynchronous Transfer Mode
      BFD      Bidirectional Forwarding Detection
      BTS      Base Transceiver Station
      CC-CV    Continuity Check and Connectivity Verification
      CDMA     Code Division Multiple Access
      E-LINE   Ethernet point-to-point connectivity
      E-LAN    Ethernet LAN, provides multipoint connectivity
      eNB      Evolved Node B
      EPC      Evolved Packet Core
      E-VLAN   Ethernet Virtual Private LAN
      EVDO     Evolution-Data Optimized 
      G-ACh    Generic Associated Channel
      GAL      G-ACh Label
      GMPLS    Generalized Multi-Protocol Label Switching
      GSM      Global System for Mobile Communications
      HSPA     High Speed Packet Access
      IPTV     Internet Protocol television
      L2VPN    Layer 2 Virtual Private Network
      L3VPN    Layer 3 Virtual Private Network
      LAN      Local Access Network
      LDI      Link Down Indication
      LDP      Label Distribution Protocol
      LSP      Label Switched Path
      LTE      Long Term Evolution
      MEP      Maintenance Entity Group End Point
      MIP      Maintenance Entity Group Intermediate Point   
      MPLS     MultiProtocol Label Switching
      MPLS-TP  MultiProtocol Label Switching Transport Profile
      MS-PW    Multi-Segment Pseudowire
      NMS      Network Management System
      OAM      Operations, Administration, and Maintenance
      OPEX     Operating Expenses

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      PE       Provider-Edge device
      PDN GW   Packet Data Network Gateway
      PW       Pseudowire
      RAN      Radio Access Network
      RDI      Remote Defect Indication
      S1       LTE Standardized interface between eNB and EPC 
      SDH      Synchronous Digital Hierarchy
      SGW      Serving Gateway
      SLA      Service Level Agreement
      SONET    Synchronous Optical Network 
      S-PE     PW Switching Provider Edge   
      SP       Service Provider
      SRLG     Shared Risk Link Groups
      SS-PW    Single-Segment Pseudowire
      TDM      Time Division Multiplexing
      TFS      Time and Frequency Synchronization
      tLDP     Targeted Label Distribution Protocol
      VPN      Virtual Private Network
      UMTS     Universal Mobile Telecommunications System 
      X2       LTE Standardized interface between eNBs for handover

1.2. Background

   Traditional transport technologies include SONET/SDH, TDM, and ATM.
   There is a transition away from these transport technologies to new
   packet transport technologies. In addition to the increasing demand
   for bandwidth, packet transport technologies offer the following key

   Bandwidth efficiency: Traditional transport technologies support
   fixed Bandwidth, no packet statistical multiplexing, the bandwidth is
   reserved in the transport network regardless it is used by the client
   or not. In contrast, packet technologies support statistical
   multiplexing. This is the most important motivation for the
   transition from traditional transport technologies to packet
   transport technologies. The proliferation of new distributed
   applications which communicate with servers over the network in a
   bursty fashion has been driving the adoption of packet transport
   techniques, since packet multiplexing of traffic from bursty sources
   provides more efficient use of bandwidth than traditional circuit-
   based TDM technologies.

   Flexible data rate connections: The granularity of data rate
   connections of traditional transport technologies is limited to the
   rigid PDH or SONET hierarchy (e.g., DS1, DS3, OC3, OC12, etc.).
   Packet technologies support flexible data rate connections. The
   support of finer data rate granularity is particularly important for

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   today's wireline and wireless services and applications.

   QoS support: While traditional transport technology, such as TDM, has
   very limited QoS support, packet transport can provide proper QoS
   treatment for IPTV, Voice and Video over IP applications.

   The root cause for transport moving to packet transport is the shift
   of application from TDM to packet. For example, Voice TDM to VoIP;
   Video to Video over IP; TDM access lines to Ethernet; TDM VPNs to IP
   VPNs and Ethernet VPNs. In addition, network convergence and
   technology refreshes demand for common and a flexible infrastructure
   that provides multiple services.

   As part of MPLS family, MPLS-TP complements existing IP/MPLS
   technologies; it closes the gaps in the traditional access and
   aggregation transport to enable end-to-end packet technology
   solutions in a cost efficient, reliable, and interoperable manner.
   After several years of industry debate on which packet technology to
   use, MPLS-TP has emerged as the next generation transport technology
   of choice for many Service Providers worldwide. 

   The Unified MPLS strategy - using MPLS from core to aggregation and
   access (e.g. IP/MPLS in the core, IP/MPLS or MPLS-TP in aggregation
   and access) appear to be very attractive to many SPs. It streamlines
   the operation, reduces the overall complexity, and improves end-to-
   end convergence. It leverages the MPLS experience, and enhances the
   ability to support revenue generating services.

   MPLS-TP is a subset of MPLS functions that meet the packet transport
   requirements defined in [RFC5654]. This subset includes: MPLS data
   forwarding, pseudo-wire encapsulation for circuit emulation, and
   dynamic control plane using GMPLS control for LSP and tLDP for
   pseudo-wire (PW). MPLS-TP also extends previous MPLS OAM functions,
   such as BFD extension for proactive Connectivity Check and
   Connectivity Verification (CC-CV) [RFC6428], and Remote Defect
   Indication (RDI) [RFC6428], LSP Ping Extension for on-demand CC-CV
   [RFC6426]. New tools have been defined for alarm suppression with
   Alarm Indication Signal (AIS) [RFC6427], and switch-over triggering
   with Link Defect Indication (LDI) [RFC6427]. Note that since the MPLS
   OAM feature extensions defined through the process of MPLS-TP
   development are part of the MPLS family, the applicability is general
   to MPLS, and not limited to MPLS-TP.

   The requirements of MPLS-TP are provided in MPLS-TP Requirements [RFC
   5654], and the architectural framework is defined in MPLS-TP
   Framework [RFC5921]. This document's intent is to provide the use
   case studies and design considerations from a practical point of view
   based on Service Providers deployments plan as well as actual

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   The most common use cases for MPLS-TP include Metro access and
   aggregation, Mobile Backhaul, and Packet Optical Transport. MPLS-TP
   data plane architecture, path protection mechanisms, and OAM
   functionality are used to support these deployment scenarios. 

   The design considerations discussed in this document include: the
   role of MPLS-TP in the network; provisioning options; standards
   compliance; end-to-end forwarding and OAM consistency; compatibility
   with existing IP/MPLS networks; and optimization vs. simplicity
   design trade-offs.

2. MPLS-TP Use Cases

2.1. Metro Access and Aggregation 

   The use of MPLS-TP for Metro access and aggregation transport is the
   most common deployment scenario observed in the field. 

   Some operators are building green-field access and aggregation
   transport infrastructure, while others are upgrading/replacing their
   existing transport infrastructure with new packet technologies. The
   existing legacy access and aggregation networks are usually based on
   TDM or ATM technologies. Some operators are replacing these networks
   with MPLS-TP technologies, since legacy ATM/TDM aggregation and
   access are becoming inadequate to support the rapid business growth
   and too expensive to maintain. In addition, in many cases the legacy
   devices are facing End of Sale and End of Life issues. As operators
   must move forward with the next generation packet technology, the
   adoption of MPLS-TP in access and aggregation becomes a natural
   choice. The statistical multiplexing in MPLS-TP helps to achieve
   higher efficiency compared with the time division scheme in the
   legacy technologies. MPLS-TP OAM tools and protection mechanisms help
   to maintain high reliability of transport networks and achieve fast

   As most Service Providers' core networks are MPLS enabled, extending
   the MPLS technology to the aggregation and access transport networks
   with a Unified MPLS strategy is very attractive to many Service
   Providers. Unified MPLS strategy in this document means having end-
   to-end MPLS technologies through core, aggregation, and access. It
   reduces OPEX by streamlining operation and leveraging the operational
   experience already gained with MPLS technologies; it also improves
   network efficiency and reduces end-to-end convergence time. 

   The requirements from the SPs for ATM/TDM aggregation replacement
   often include: i) maintaining the previous operational model, which

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   means providing a similar user experience in NMS, ii) supporting the
   existing access network, (e.g., Ethernet, ADSL, ATM, TDM, etc.), and
   connections with the core networks, and iii) supporting the same
   operational capabilities and services (L3VPN, L2VPN, E-LINE/E-LAN/E-
   VLAN, Dedicated Line, etc.). MPLS-TP can meet these requirements and
   in general the requirements defined in [RFC5654] to support a smooth

2.2. Packet Optical Transport 

   Many SP's transport networks consist of both packet and optical
   portions. The transport operators are typically sensitive to network
   deployment cost and operational simplicity. MPLS-TP supports both
   static provisioning through NMS and dynamic provisioning via the
   GMPLS control plane. As such, it is viewed as a natural fit in some
   of the transport networks, where the operators can utilize the MPLS-
   TP LSP's (including the ones statically provisioned) to manage user
   traffic as "circuits" in both packet and optical networks, and when
   they are ready, move to dynamic control plane for greater efficiency.

   Among other attributes, bandwidth management, protection/recovery and
   OAM are critical in Packet/Optical transport networks. In the context
   of MPLS-TP, each LSP is expected to be associated with a fixed amount
   of bandwidth in terms of bits-per-second and/or time-slots. OAM is to
   be performed on each individual LSP. For some of the performance
   monitoring (PM) functions, the OAM mechanisms need to be able to
   transmit and process OAM packets at very high frequency. An overview
   of MPLS-TP OAM toolset is found in [RFC6669].

   Protection [RFC6372] is another important element in transport
   networks. Typically, ring and linear protection can be readily
   applied in metro networks. However, as long-haul networks are
   sensitive to bandwidth cost and tend to have mesh-like topology,
   shared mesh protection is becoming increasingly important. 

   In some cases, SPs plan to deploy MPLS-TP from their long haul
   optical packet transport all the way to the aggregation and access in
   their networks. 

2.3. Mobile Backhaul 

   Wireless communication is one of the fastest growing areas in
   communication worldwide. In some regions, the tremendous mobile
   growth is fueled by the lack of existing land-line and cable
   infrastructure. In other regions, the introduction of smart phones is
   quickly driving mobile data traffic to become the primary mobile
   bandwidth consumer (some SPs have already observed more than 85% of
   total mobile traffic are data traffic). MPLS-TP is viewed as a

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   suitable technology for Mobile backhaul. 

2.3.1. 2G and 3G Mobile Backhaul 

   MPLS-TP is commonly viewed as a very good fit for 2G/3G mobile
   backhaul. 2G (GSM/CDMA) and 3G (UMTS/HSPA/1xEVDO) Mobile Backhaul
   Networks are still currently dominating the mobile infrastructure. 

   The connectivity for 2G/3G networks is point to point (P2P). The
   logical connections are hub-and-spoke. Networks are physically
   constructed using a star or ring topology. In the Radio Access
   Network (RAN), each mobile Base Transceiver Station (BTS/Node B) is
   communicating with a Radio Controller (BSC/RNC). These connections
   are often statically set up.  

   Hierarchical or centralized architectures are often used for pre-
   aggregation and aggregation layers. Each aggregation network inter-
   connects with multiple access networks. For example, a single
   aggregation ring could aggregate traffic for 10 access rings with a
   total of 100 base stations.   

   The technology used today is largely ATM based. Mobile providers are
   replacing the ATM RAN infrastructure with newer packet technologies.
   IP RAN networks with IP/MPLS technologies are deployed today by many
   SPs with great success. MPLS-TP is another suitable choice for Mobile
   RAN. The P2P connections from base station to Radio Controller can be
   set statically to mimic the operation of today's RAN environments;
   in-band OAM and deterministic path protection can support fast
   failure detection and switch-over to satisfy the SLA agreements.
   Bidirectional LSPs may help to simplify the provisioning process. The
   deterministic nature of MPLS-TP LSP set up can also support packet
   based synchronization to maintain predictable performance regarding
   packet delay and jitters. The traffic engineered and co-routed
   bidirectional properties of an MPLS-TP LSP are of benefit in
   transporting packet based Time and Frequency Synchronization (TFS)
   protocols such as [1588overmpls]. However, the choice between an
   external, physical layer or packet based TFS method is network
   dependent and thus is out of scope of this document.

2.3.2. 4G/LTE Mobile Backhaul 

   One key difference between LTE and 2G/3G mobile networks is that the
   logical connection in LTE is a mesh, while in 2G/3G is a P2P star. In
   LTE, the base stations eNB/BTS communicate with multiple Network
   controllers (PDN GW/SGW or ASNGW), and the radio elements communicate
   with one another for signal exchange and traffic offload to wireless
   or wireline infrastructures. 


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   IP/MPLS has a great advantage in any-to-any connectivity
   environments. Thus, the use of mature IP or L3VPN technologies is
   particularly common in the design of SP's LTE deployment plans.

   The extended OAM functions defined in MPLS-TP, such as in-band OAM
   and path protection mechanisms bring additional advantages to support
   SLAs. The dynamic control-plane with GMPLS signaling is especially
   suited for the mesh environment, to support dynamic topology changes
   and network optimization.

   Some operators are using the same model as in 2G and 3G Mobile
   Backhaul, which uses IP/MPLS in the core, and MPLS-TP with static
   provisioning (through NMS) in aggregation and access. The reasoning
   is as follows: the X2 traffic load in LTE networks currently may be a
   very small percentage of the total traffic. For example, one large
   mobile operator observed that X2 traffic was less than one percent of
   the total S1 traffic. Therefore, optimizing the X2 traffic may not be
   the design objective in this case. The X2 traffic can be carried
   through the same static tunnels together with the S1 traffic in the
   aggregation and access networks, and further forwarded across the
   IP/MPLS core. In addition, mesh protection may be more efficient with
   regard to bandwidth utilization, but linear protection and ring
   protection are often considered simpler by some operators from the
   point of view of operation maintenance and trouble shooting, and so
   are widely deployed. In general, using MPLS-TP with static
   provisioning for LTE backhaul is a viable option. The design
   objective of using this approach is to keep the operation simple and
   use a common model for mobile backhaul, especially during the
   transition period.

   The TFS considerations stated in Section 3.3.1 apply to the 4G/LTE
   Mobile Backhaul case as well.

3. Network Design Considerations  

3.1. The role of MPLS-TP

   The role of MPLS-TP is to provide a solution to help evolve
   traditional transport towards packet. It is designed to support the
   transport characteristics/behavior described in [RFC5654]. The
   primary use of MPLS-TP is largely to replace legacy transport
   technologies, such as SONET/SDH. MPLS-TP is not designed to replace
   the service support capabilities of IP/MPLS, such as L2VPN, L3VPN,
   IPTV, Mobile RAN, etc. 

3.2. Provisioning mode

   MPLS-TP supports two provisioning modes: i) a mandatory static

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   provisioning mode, which must be supported without dependency on
   dynamic routing or signaling; and ii) an optional distributed dynamic
   control plane, which is used to enable dynamic service provisioning.

   The decision on which mode to use is largely dependent on the
   operational feasibility and the stage of network transition.
   Operators who are accustomed to the transport-centric operational
   model (e.g., NMS configuration without control plane) typically
   prefer the static provisioning mode. This is the most common choice
   in current deployments. The dynamic provisioning mode can be more
   powerful but it is more suited to operators who are familiar with the
   operation and maintenance of IP/MPLS technologies or are ready to
   step up through training and planned transition. 

   There may be also cases where operators choose to use the combination
   of both modes. This is appropriate when parts of the network are
   provisioned in a static fashion and other parts are controlled by
   dynamic signaling. This combination may also be used to transition
   from static provisioning to dynamic control plane.   

3.3. Standards compliance 

   It is generally recognized by SPs that standards compliance is
   important for lowering cost, accelerating product maturity, achieving
   multi-vendor interoperability, and meeting the expectations of their
   enterprise customers. 

   MPLS-TP is a joint work between IETF and ITU-T. In April 2008, IETF
   and ITU-T jointly agreed to terminate T-MPLS and progress MPLS-TP as
   joint work [RFC5317]. The transport requirements are provided by ITU-
   T, the protocols are developed in IETF.  

3.4. End-to-end MPLS OAM consistency 

   End-to-end MPLS OAM consistency is highly desirable in order to
   enable Service Providers to deploy an end-to-end MPLS solution. As
   MPLS-TP adds OAM function to the MPLS toolkit, it cannot be expected
   that a full-function end-to-end LSP with MPLS-TP OAM can be achieved
   when the LSP traverses a legacy MPLS/IP core. Although it may be
   possible to select a subset of MPLS-TP OAM that can be gatewayed to
   the legacy MPLS/IP OAM, a better solution is achieved by tunneling
   the MPLS-TP LSP over the legacy MPLS/IP network. In that mode of
   operation, legacy OAM may be run on the tunnel in the core, and the
   tunnel end-points may report issues in as much detail as possible to
   the MIPs in the MPLS-TP LSP. Note that over time it is expected that
   routers in the MPLS/IP core will be upgraded to fully support MPLS-TP
   features: once this has occurred, it will be possible to run end-to-
   end MPLS-TP LSPs seamlessly across the core. 

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3.5. PW Design considerations in MPLS-TP networks 

   In general, PWs in MPLS-TP work the same as in IP/MPLS networks. Both
   Single-Segment PW (SS-PW) and Multi-Segment PW (MS-PW) are supported.
   For dynamic control plane, Targeted LDP (tLDP) is used. In static
   provisioning mode, PW status is a new PW OAM feature for failure
   notification. In addition, both directions of a PW must be bound to
   the same transport bidirectional LSP. 

   In the common network topology involving multi-tier rings, the design
   choice is between using SS-PW or MS-PW. This is not a discussion
   unique to MPLS-TP, as it applies to PW design in general, but it is
   relevant here, since MPLS-TP is more sensitive to the operational
   complexities, as noted by operators. If MS-PW is used, Switched PE
   (S-PE) must be deployed to connect the rings. The advantage of this
   choice is that it provides domain isolation, which in turn
   facilitates trouble shooting and allows for faster PW failure
   recovery. On the other hand, the disadvantage of using S-PE is that
   it adds more complexity. Using SS-PW is simpler, since it does not
   require S-PEs, but less efficient because the paths across primary
   and secondary rings are longer. If operational simplicity is a higher
   priority, some SPs choose the latter. 

   Another design trade-off is whether to use PW protection in addition
   to LSP protection or rely solely on LSP protection. When the MPLS-TP
   LSPs are protected, if the working LSP fails, the protect LSP assures
   that the connectivity is maintained and the PW is not impacted.
   However, in the case of simultaneous failure of both working and
   protect LSPs, the attached PW would fail. By adding PW protection,
   and attaching the protect PW to a diverse LSP not in the same Shared
   Risk Link Group (SRLG), the PW is protected even when the primary PW
   fails.  Clearly, using PW protection adds considerably more
   complexity and resource usage, and thus operators often may choose
   not to use it, and consider protection against single point of
   failure as sufficient. 

3.6. Proactive and on-demand MPLS-TP OAM tools 

   MPLS-TP provide both proactive and on-demand OAM Tools. As a
   proactive OAM fault management tool, BFD Connectivity Check (CC) can
   be sent at regular intervals for Connectivity Check; three missed CC
   messages (or a configurable number) can trigger the failure
   protection switch-over. BFD sessions are configured for both working
   and protecting LSPs. 

   A design decision is choosing the value of the BFD CC interval. The
   shorter the interval, the faster the detection time is, but also the
   higher the resource utilization is. The proper value depends on the

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   application and the service needs.

   As an on-demand OAM fault management mechanism, for example when
   there is a fiber cut, Link Down Indication (LDI) message [RFC6427]
   can be generated from the failure point and propagated to the
   Maintenance Entity Group End Points (MEPs) to trigger immediate
   switch-over from working to protect path. An Alarm Indication Signal
   (AIS) can be propagated from the Maintenance Entity Group
   Intermediate Point (MIP) to the MEPs for alarm suppression. 

   In general, both proactive and on-demand OAM tools should be enabled
   to guarantee short switch-over times.  

3.7. MPLS-TP and IP/MPLS Interworking considerations  

   Since IP/MPLS is largely deployed in most SPs' networks, MPLS-TP and
   IP/MPLS Interworking is inevitable if not a reality. However,
   Interworking discussion is out of the scope of this document; it is
   for further study.

4. Security Considerations 

   Under the use case of Metro access and aggregation, in the scenario
   where some of the access equipment is placed in facilities not owned
   by the SP, the static provisioning mode of MPLS-TP is often preferred
   over the control plane option because it eliminates the possibility
   of a control plane attack which may potentially impact the whole
   network. This scenario falls into the Security Reference Model 2 as
   described in [RFC6941].

   Similar location issues apply to the mobile use cases, since
   equipment is often placed in remote and outdoor environment, which
   can increase the risk of un-authorized access to the equipment. 

   In general, NMS access can be a common point of attack in all MPLS-TP
   use cases, and attacks to GAL or G-ACh are unique security treats to
   MPLS-TP. The MPLS-TP security considerations are discussed in MPLS-TP
   Security Framework [RFC6941]. General security considerations for
   MPLS and GMPLS networks are addressed in Security Framework for MPLS
   and GMPLS Networks [RFC5920].  

5. IANA Considerations 

   This document contains no new IANA considerations. 

6. Acknowledgements

   The authors wish to thank Adrian Farrel for his review as Routing

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   Area Director, Adrian's detailed comments and suggestions were of
   great help for improving the quality of this document, and thank Loa
   Andersson and Adrian Farrel for their continued support and guidance.
   The authors would also like to thank Weiqiang Cheng for his helpful
   input on LTE Mobile backhaul based on his knowledge and experience in
   real world deployment, thank Stewart Bryant for his text contribution
   on timing, thank Russ Housley for his improvement suggestions, thank
   Andrew Malis for his support and use case discussion, thank Pablo
   Frank, Lucy Yong, Huub van Helvoort, Tom Petch, Curtis Villamizar,
   and Paul Doolan for their comments and suggestions, thank Joseph Yee
   and Miguel Garcia for their APPSDIR and Gen-ART reviews and comments

7. References

7.1. Normative References

   [RFC5654]  Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
              Sprecher, N., and S. Ueno, "Requirements of an MPLS
              Transport Profile", RFC 5654, September 2009.

   [RFC5920]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, July 2010.

   [RFC5921]  Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
              L., and L. Berger, "A Framework for MPLS in Transport
              Networks", RFC 5921, July 2010.

   [RFC6426]  Gray, E., Bahadur, N., Boutros, S., and R. Aggarwal, "MPLS
              On-Demand Connectivity Verification and Route Tracing",
              RFC 6426, November 2011.

   [RFC6427]  Swallow, G., Ed., Fulignoli, A., Ed., Vigoureux, M., Ed.,
              Boutros, S., and D. Ward, "MPLS Fault Management
              Operations, Administration, and Maintenance (OAM)",
              RFC 6427, November 2011.

   [RFC6428]  Allan, D., Ed., Swallow Ed., G., and J. Drake Ed.,
              "Proactive Connectivity Verification, Continuity Check,
              and Remote Defect Indication for the MPLS Transport
              Profile", RFC 6428, November 2011.

7.2. Informative References

   [RFC5317]  Bryant, S., Ed., and L. Andersson, Ed., "Joint Working
              Team (JWT) Report on MPLS Architectural Considerations for
              a Transport Profile", RFC 5317, February 2009.


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   [RFC6372]  Sprecher, N., Ed., and A. Farrel, Ed., "MPLS Transport
              Profile (MPLS-TP) Survivability Framework", RFC 6372,
              September 2011.

   [RFC6669]  Sprecher, N. and L. Fang, "An Overview of the Operations,
              Administration, and Maintenance (OAM) Toolset for MPLS-
              Based Transport Networks", RFC 6669, July 2012.

   [RFC6941]  Fang, L. Ed., Niven-Jenkins, B., Ed., Mansfield,  
              S., Ed., and R. Graveman, Ed., "MPLS-TP Security
              Framework," RFC 6941, April 2013.

   [1588overmpls], Davari, S., Oren, A., Bhatia, M., Roberts, P., and  
              L. Montini, "Transporting Timing messages over MPLS
              Networks," draft-ietf-tictoc-1588overmpls-04.txt, February

Authors' Addresses

      Luyuan Fang 
      Cisco Systems, Inc. 
      111 Wood Ave. South 
      Iselin, NJ 08830
      United States

      Nabil Bitar 
      40 Sylvan Road 
      Waltham, MA 02145
      United States 

      Raymond Zhang 
      701 Middlefield Road 
      Mountain View, CA 94043
      United States 

      Masahiro Daikoku
      KDDI corporation 
      3-11-11.Iidabashi, Chiyodaku, Tokyo

      Ping Pan

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      United States

Contributors' Addresses

      Kam Lee Yap 
      XO Communications 
      13865 Sunrise Valley Drive, 
      Herndon, VA 20171
      United States 

      Dan Frost 
      Cisco Systems, Inc.
      United Kingdom 

      Henry Yu 
      TW Telecom 
      10475 Park Meadow Dr. 
      Littleton, CO 80124
      United States

      Jian Ping Zhang   
      China Telecom, Shanghai    
      Room 3402, 211 Shi Ji Da Dao 
      Pu Dong District, Shanghai

      Lei Wang  
      Lime Networks
      Strandveien 30, 1366 Lysaker

      Mach(Guoyi) Chen 
      Huawei Technologies Co., Ltd. 
      No. 3 Xinxi Road 
      Shangdi Information Industry Base 
      Hai-Dian District, Beijing 100085 

      Nurit Sprecher  
      Nokia Siemens Networks 
      3 Hanagar St. Neve Ne'eman B 

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      Hod Hasharon, 45241 

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