A Framework for Point-to-Multipoint MPLS in Transport Networks
draft-fbb-mpls-tp-p2mp-framework-04

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.

Status of this Memo

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This Internet-Draft will expire on December 15, 2012.

Copyright Notice

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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
• Authors' Addresses

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]. The MPLS-TP Framework [RFC5921] 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 [RFC5921] 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 [RFC5921] and [RFC5654].

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] and [RFC5332], and PW support is being developed based on [I-D.ietf-pwe3-p2mp-pw-requirements] and [I-D.ietf-l2vpn-vpms-frmwk-requirements]. 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], [RFC5860], and [RFC5951]. 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 [RFC5921]. 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] and the related data-plane behaviour was further clarified in [RFC5332]. 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].

4. Operations, Administration and Maintenance (OAM)

The overall OAM architecture for MPLS-TP is defined in [RFC6371].

[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 [RFC6373].

[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].

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.ietf-pwe3-p2mp-pw].

6. Survivability

The overall survivability architecture for MPLS-TP is defined in [RFC6372].

[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 [RFC5951]. They derive from the generic specifications described in ITU-T G.7710/Y.1701 [G.7710] for transport technologies. They also incorporate the OAM requirements for MPLS Networks [RFC4377] and MPLS-TP Networks [RFC5860] 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 [RFC5921], 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