A Framework for Point-to-Multipoint MPLS in Transport Networks
draft-fbb-mpls-tp-p2mp-framework-01

Abstract

The Multiprotocol Label Switching (MPLS) Transport Profile (MPLS-TP) is the common set of MPLS protocol functions defined to enable the construction and operation of packet transport networks. The MPLS-TP supports both point-to-point and point-to-multipoint transport paths. This document defines the elements and functions of the MPLS-TP architecture applicable specifically to supporting point-to-multipoint transport paths.

This document is a product of a joint Internet Engineering Task Force (IETF) / International Telecommunication Union Telecommunication Standardization Sector (ITU-T) effort to include an MPLS Transport Profile within the IETF MPLS and PWE3 architectures to support the capabilities and functionalities of a packet transport network.

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Table of Contents

1.  Introduction
    1.1.  Scope
    1.2.  Terminology
        1.2.1.  Additional Definitions and Terminology
    1.3.  Applicability
2.  MPLS Transport Profile Point-to-Multipoint Requirements
3.  Architecture
    3.1.  MPLS-TP Encapsulation and Forwarding
4.  Operations, Administration and Maintenance (OAM)
5.  Control Plane
    5.1.  Point-to-Multipoint LSP Control Plane
    5.2.  Point-to-Multipoint PW Control Plane
6.  Survivability
7.  Network Management
8.  Security Considerations
9.  IANA Considerations
10.  References
    10.1.  Normative References
    10.2.  Informative References

1.  Introduction

The Multiprotocol Label Switching (MPLS) Transport Profile (MPLS-TP) is the common set of MPLS protocol functions defined to meet the requirements specified in [RFC5654] (Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and S. Ueno, “Requirements of an MPLS Transport Profile,” September 2009.). The MPLS-TP Framework [I‑D.ietf‑mpls‑tp‑framework] (Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. Berger, “A Framework for MPLS in Transport Networks,” May 2010.) provides an overall introduction to the MPLS-TP and defines the general architecture of the Transport Profile, as well as those aspects specific to point-to-point transport paths. The purpose of this document is to define the elements and functions of the MPLS-TP architecture applicable specifically to supporting point-to-multipoint transport paths.

This document is a product of a joint Internet Engineering Task Force (IETF) / International Telecommunication Union Telecommunication Standardization Sector (ITU-T) effort to include an MPLS Transport Profile within the IETF MPLS and PWE3 architectures to support the capabilities and functionalities of a packet transport network.

1.1.  Scope

This document defines the elements and functions of the MPLS-TP architecture related to supporting point-to-multipoint transport paths. The reader is referred to [I‑D.ietf‑mpls‑tp‑framework] (Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. Berger, “A Framework for MPLS in Transport Networks,” May 2010.) for those aspects of the MPLS-TP architecture that are generic, or concerned specifically with point-to-point transport paths.

1.2.  Terminology

1.2.1.  Additional Definitions and Terminology

Detailed definitions and additional terminology may be found in [I‑D.ietf‑mpls‑tp‑framework] (Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. Berger, “A Framework for MPLS in Transport Networks,” May 2010.) and [RFC5654] (Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and S. Ueno, “Requirements of an MPLS Transport Profile,” September 2009.).

1.3.  Applicability

The point-to-multipoint connectivity provided by an MPLS-TP network is based on the point-to-multipoint connectivity provided by MPLS networks. MPLS TE-LSP support is discussed in [RFC4875] (Aggarwal, R., Papadimitriou, D., and S. Yasukawa, “Extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for Point-to-Multipoint TE Label Switched Paths (LSPs),” May 2007.) and [RFC5332] (Eckert, T., Rosen, E., Aggarwal, R., and Y. Rekhter, “MPLS Multicast Encapsulations,” August 2008.), and PW support is being developed based on [I‑D.ietf‑pwe3‑p2mp‑pw‑requirements] (Heron, G., Wang, L., Aggarwal, R., Vigoureux, M., Bocci, M., Jin, L., JOUNAY, F., Niger, P., Kamite, Y., DeLord, S., and L. Martini, “Requirements for Point-to-Multipoint Pseudowire,” January 2010.) and [I‑D.ietf‑l2vpn‑vpms‑frmwk‑requirements] (Kamite, Y., JOUNAY, F., Niven-Jenkins, B., Brungard, D., and L. Jin, “Framework and Requirements for Virtual Private Multicast Service (VPMS),” October 2009.). MPLS-TP point-to-multipoint connectivity is analogous to that provided by traditional transport technologies such as Optical Transport Network (OTN) point-to-multipoint [ref?] and optical drop-and-continue [ref?], and thus supports the same class of traditional applications.

2.  MPLS Transport Profile Point-to-Multipoint Requirements

The requirements for MPLS-TP are specified in [RFC5654] (Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and S. Ueno, “Requirements of an MPLS Transport Profile,” September 2009.), [I‑D.ietf‑mpls‑tp‑oam‑requirements] (Vigoureux, M. and D. Ward, “Requirements for OAM in MPLS Transport Networks,” March 2010.), and [I‑D.ietf‑mpls‑tp‑nm‑req] (Mansfield, S. and K. Lam, “MPLS TP Network Management Requirements,” October 2009.). This section provides a brief summary of point-to-multipoint transport requirements as set out in those documents; the reader is referred to the documents themselves for the definitive and complete list of requirements.

• MPLS-TP must support unidirectional point-to-multipoint (P2MP) transport paths.
• MPLS-TP must support traffic-engineered point-to-multipoint transport paths.
• MPLS-TP must be capable of using P2MP server (sub)layer capabilities as well as P2P server (sub)layer capabilities when supporting P2MP MPLS-TP transport paths.
• The MPLS-TP control plane must support establishing all the connectivity patterns defined for the MPLS-TP data plane (i.e., unidirectional P2P, associated bidirectional P2P, co-routed bidirectional P2P, unidirectional P2MP) including configuration of protection functions and any associated maintenance functions.
• Recovery techniques used for P2P and P2MP should be identical to simplify implementation and operation.
• Unidirectional 1+1 and 1:n protection for P2MP connectivity must be supported.
• MPLS-TP recovery in a ring must protect unidirectional P2MP transport paths.

3.  Architecture

The overall architecture of the MPLS Transport Profile is defined in [I‑D.ietf‑mpls‑tp‑framework] (Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. Berger, “A Framework for MPLS in Transport Networks,” May 2010.). The architecture for point-to-multipoint MPLS-TP comprises the following additional elements and functions:

• Unidirectional point-to-multipoint Label Switched Paths (LSPs)
• Unidirectional point-to-multipoint pseudowires (PWs)
• Optional point-to-multipoint LSP and PW control planes
• Survivability, network management, and Operations, Administration and Maintenance (OAM) functions for point-to-multipoint PWs and LSPs

The following subsections summarise the encapsulation and forwarding of point-to-multipoint traffic within an MPLS-TP network, and the encapsulation options for delivery of traffic to and from MPLS-TP Customer Edge devices when the network is providing a packet transport service.

3.1.  MPLS-TP Encapsulation and Forwarding

Packet encapsulation and forwarding for MPLS-TP point-to-multipoint LSPs is identical to that for MPLS-TE point-to-multipoint LSPs. MPLS-TE point-to-multipoint LSPs were introduced in [RFC4875] (Aggarwal, R., Papadimitriou, D., and S. Yasukawa, “Extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for Point-to-Multipoint TE Label Switched Paths (LSPs),” May 2007.) and the related data-plane behaviour was further clarified in [RFC5332] (Eckert, T., Rosen, E., Aggarwal, R., and Y. Rekhter, “MPLS Multicast Encapsulations,” August 2008.). MPLS-TP allows for both upstream-assigned and downstream-assigned labels for use with point-to-multipoint LSPs.

Packet encapsulation and forwarding for point-to-multipoint PWs is currently being defined by the PWE3 Working Group [I‑D.raggarwa‑pwe3‑p2mp‑pw‑encaps] (Aggarwal, R. and F. JOUNAY, “Point-to-Multipoint Pseudo-Wire Encapsulation,” March 2010.).

4.  Operations, Administration and Maintenance (OAM)

The overall OAM architecture for MPLS-TP is defined in [I‑D.ietf‑mpls‑tp‑oam‑framework] (Allan, D., Busi, I., Niven-Jenkins, B., Fulignoli, A., Hernandez-Valencia, E., Levrau, L., Mohan, D., Sestito, V., Sprecher, N., Helvoort, H., Vigoureux, M., Weingarten, Y., and R. Winter, “MPLS-TP OAM Framework,” April 2010.).

[Editor's note: This section will contain a summary of point-to-multipoint OAM as described in the OAM Framework.]

5.  Control Plane

The overall control plane architecture for MPLS-TP is defined in [I‑D.abfb‑mpls‑tp‑control‑plane‑framework] (Andersson, L., Berger, L., Fang, L., Bitar, N., Takacs, A., Vigoureux, M., and E. Bellagamba, “MPLS-TP Control Plane Framework,” February 2010.).

[Editor's note: This section will contain a summary of the point-to-multipoint control plane as described in the Control Plane Framework.]

5.1.  Point-to-Multipoint LSP Control Plane

The MPLS-TP control plane for point-to-multipoint LSPs uses Generalized MPLS (GMPLS) and is based on Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for point-to-multipoint LSPs as defined in [RFC4875] (Aggarwal, R., Papadimitriou, D., and S. Yasukawa, “Extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for Point-to-Multipoint TE Label Switched Paths (LSPs),” May 2007.).

5.2.  Point-to-Multipoint PW Control Plane

The MPLS-TP control plane for point-to-multipoint pseudowires is based on the LDP P2MP signaling extensions for PWs defined in [I‑D.martini‑pwe3‑p2mp‑pw] (Martini, L., Boutros, S., Sivabalan, S., Konstantynowicz, M., Vecchio, G., Nadeau, T., JOUNAY, F., Niger, P., Kamite, Y., Jin, L., Vigoureux, M., Ciavaglia, L., and S. Delord, “Signaling Root-Initiated Point-to-Multipoint Pseudowires using LDP,” October 2009.).

6.  Survivability

The overall survivability architecture for MPLS-TP is defined in [I‑D.ietf‑mpls‑tp‑survive‑fwk] (Sprecher, N. and A. Farrel, “Multiprotocol Label Switching Transport Profile Survivability Framework,” June 2010.).

[Editor's note: This section will contain a summary of point-to-multipoint survivability as described in the Survivability Framework.]

7.  Network Management

The network management architecture and requirements for MPLS-TP are specified in [I‑D.ietf‑mpls‑tp‑nm‑req] (Mansfield, S. and K. Lam, “MPLS TP Network Management Requirements,” October 2009.). They derive from the generic specifications described in ITU-T G.7710/Y.1701 [G.7710] (, “ITU-T Recommendation G.7710/Y.1701 (07/07), "Common equipment management function requirements",” 2005.) for transport technologies. They also incorporate the OAM requirements for MPLS Networks [RFC4377] (Nadeau, T., Morrow, M., Swallow, G., Allan, D., and S. Matsushima, “Operations and Management (OAM) Requirements for Multi-Protocol Label Switched (MPLS) Networks,” February 2006.) and MPLS-TP Networks [I‑D.ietf‑mpls‑tp‑oam‑requirements] (Vigoureux, M. and D. Ward, “Requirements for OAM in MPLS Transport Networks,” March 2010.) and expand on those requirements to cover the modifications necessary for fault, configuration, performance, and security in a transport network.

[Editor's note: Decide what if anything needs to be said about P2MP-specific network management considerations.]

8.  Security Considerations

General security considerations for MPLS-TP are noted in [I‑D.ietf‑mpls‑tp‑framework] (Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. Berger, “A Framework for MPLS in Transport Networks,” May 2010.), and security considerations for point-to-multipoint PWs and LSPs in the documents that define them. This document introduces no new security considerations in itself.

9.  IANA Considerations

IANA considerations resulting from specific elements of MPLS-TP functionality are detailed in the documents specifying that functionality. This document introduces no additional IANA considerations in itself.

10.  References

10.1. Normative References

10.2. Informative References

Authors' Addresses