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rfc:rfc8339

Internet Engineering Task Force (IETF) P. Jain, Ed. Request for Comments: 8339 Cisco Systems, Inc. Category: Standards Track S. Boutros ISSN: 2070-1721 VMWare, Inc.

                                                             S. Aldrin
                                                           Google Inc.
                                                            March 2018

Definition of P2MP PW TLV for Label Switched Path (LSP) Ping Mechanisms

Abstract

 Label Switched Path (LSP) Ping is a widely deployed Operation,
 Administration, and Maintenance (OAM) mechanism in MPLS networks.
 This document describes a mechanism to verify connectivity of Point-
 to-Multipoint (P2MP) Pseudowires (PWs) using LSP Ping.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 7841.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 https://www.rfc-editor.org/info/rfc8339.

Copyright Notice

 Copyright (c) 2018 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
 (https://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Jain, et al. Standards Track [Page 1] RFC 8339 P2MP PW TLV for LSP Ping March 2018

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
 2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.1.  Specification of Requirements . . . . . . . . . . . . . .   3
   2.2.  Abbreviations . . . . . . . . . . . . . . . . . . . . . .   4
 3.  Identifying a P2MP PW . . . . . . . . . . . . . . . . . . . .   5
   3.1.  P2MP Pseudowire Sub-TLV . . . . . . . . . . . . . . . . .   5
 4.  Encapsulation of OAM Ping Packets . . . . . . . . . . . . . .   6
 5.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .   6
 6.  Controlling Echo Responses  . . . . . . . . . . . . . . . . .   7
 7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
 8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
 9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
   9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
   9.2.  Informative References  . . . . . . . . . . . . . . . . .   9
 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  10
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

Jain, et al. Standards Track [Page 2] RFC 8339 P2MP PW TLV for LSP Ping March 2018

1. Introduction

 A Point-to-Multipoint (P2MP) Pseudowire (PW) emulates the essential
 attributes of a unidirectional P2MP Telecommunications service such
 as P2MP ATM over a Public Switched Network (PSN).  Requirements for
 P2MP PWs are described in [RFC7338].  P2MP PWs are carried over a
 P2MP MPLS LSP.  The procedures for P2MP PW signaling using BGP are
 described in [RFC7117]; LDP for single segment P2MP PWs is described
 in [RFC8338].  Many P2MP PWs can share the same P2MP MPLS LSP; this
 arrangement is called an "Aggregate P2MP Tree".  An Aggregate P2MP
 Tree requires an upstream-assigned label so that on the Leaf PE
 (L-PE), the traffic can be associated with a Virtual Private Network
 (VPN) or a Virtual Private LAN Service (VPLS) instance.  When a P2MP
 MPLS LSP carries only one VPN or VPLS service instance, the
 arrangement is called an "Inclusive P2MP Tree".  For an Inclusive
 P2MP Tree, the P2MP MPLS LSP label itself can uniquely identify the
 VPN or VPLS service being carried over the P2MP MPLS LSP.  The P2MP
 MPLS LSP can also be used in the Selective P2MP Tree arrangement to
 carry multicast traffic.  In a Selective P2MP Tree arrangement,
 traffic to each multicast group in a VPN or VPLS instance is carried
 by a separate unique P2MP LSP.  In an Aggregate Selective P2MP Tree
 arrangement, traffic to a set of multicast groups from different VPN
 or VPLS instances is carried over the same shared P2MP LSP.
 The P2MP MPLS LSPs are setup using either P2MP RSVP-TE [RFC4875] or
 Multipoint LDP (mDLP) [RFC6388].  Mechanisms for fault detection and
 isolation for data-plane failures for P2MP MPLS LSPs are specified in
 [RFC6425].  This document describes a mechanism to detect data-plane
 failures for P2MP PW carried over P2MP MPLS LSPs.
 This document defines a new P2MP Pseudowire sub-TLV for the Target
 Forwarding Equivalence Class (FEC) Stack for P2MP PWs.  The P2MP
 Pseudowire sub-TLV is added in the Target FEC Stack TLV by the
 originator of the echo request at the Root PE (R-PE) to inform the
 receiver at the Leaf PE (L-PE) of the P2MP PW being tested.
 Support for multi-segment PWs is out of scope of this document.

2. Terminology

2.1. Specification of Requirements

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
 "OPTIONAL" in this document are to be interpreted as described in
 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
 capitals, as shown here.

Jain, et al. Standards Track [Page 3] RFC 8339 P2MP PW TLV for LSP Ping March 2018

2.2. Abbreviations

 ACH:        Associated Channel Header
 AGI:        Attachment Group Identifier
 ATM:        Asynchronous Transfer Mode
 CE:         Customer Edge
 FEC:        Forwarding Equivalence Class
 GAL:        Generic Associated Channel Label
 LDP:        Label Distribution Protocol
 L-PE:       Leaf PE (one of many destinations of the P2MP MPLS LSP,
             i.e., egress PE)
 LSP:        Label Switched Path
 LSR:        Label Switching Router
 mLDP:       Multipoint LDP
 MPLS-OAM:   MPLS Operations, Administration, and Maintenance
 P2MP:       Point-to-Multipoint
 P2MP-PW:    Point-to-Multipoint Pseudowire
 PE:         Provider Edge
 PSN:        Public Switched Network
 PW:         Pseudowire
 R-PE:       Root PE (ingress PE, PE initiating P2MP PW setup)
 RSVP:       Resource Reservation Protocol
 TE:         Traffic Engineering
 TLV:        Type, Length, Value
 VPLS:       Virtual Private LAN Service

Jain, et al. Standards Track [Page 4] RFC 8339 P2MP PW TLV for LSP Ping March 2018

3. Identifying a P2MP PW

 This document introduces a new LSP Ping Target FEC Stack sub-TLV, the
 P2MP Pseudowire sub-TLV, to identify the P2MP PW under test at the
 P2MP Leaf PE (L-PE).

3.1. P2MP Pseudowire Sub-TLV

 The P2MP Pseudowire sub-TLV has the format shown in Figure 1.  This
 TLV is included in the echo request sent over P2MP PW by the
 originator of the request.
 The Attachment Group Identifier (AGI), as described in Section 3.4.2
 of [RFC4446], in P2MP Pseudowire sub-TLV identifies the VPLS
 instance.  The Originating Router's IP address is the IPv4 or IPv6
 address of the P2MP PW root.  The address family of the IP address is
 determined by the IP Addr Len field.
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | AGI Type    |   AGI Length  |                                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                                 |
     ~                          AGI Value                            ~
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | IP Addr Len |                                                 |
     +-+-+-+-+-+-+-+                                                 |
     ~               Originating Routers IP Addr                     ~
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
               Figure 1: P2MP Pseudowire Sub-TLV Format
 For Inclusive and Selective P2MP Trees, the echo request is sent
 using the P2MP MPLS LSP label.
 For Aggregate Inclusive and Aggregate Selective P2MP Trees, the echo
 request is sent using a label stack of [P2MP MPLS LSP label, upstream
 assigned P2MP PW label].  The P2MP MPLS LSP label is the outer label
 and the upstream assigned P2MP PW label is the inner label.

Jain, et al. Standards Track [Page 5] RFC 8339 P2MP PW TLV for LSP Ping March 2018

4. Encapsulation of OAM Ping Packets

 The LSP Ping echo request packet is encapsulated with the MPLS label
 stack as described in previous sections, followed by one of the two
 encapsulation options:
 o  GAL [RFC6426] followed by an IPv4 (0x0021) or IPv6 (0x0057) type
    Associated Channel Header (ACH) [RFC4385]
 o  PW ACH [RFC4385]
 To ensure interoperability, implementations of this document MUST
 support both encapsulations.

5. Operations

 In this section, we explain the operation of the LSP Ping over a P2MP
 PW.  Figure 2 shows a P2MP PW PW1 setup from Root PE R-PE1, to Leaf
 PEs (L-PE2, L-PE3, and L-PE4).  The transport LSP associated with the
 P2MP PW1 can be mLDP P2MP MPLS LSP or P2MP TE tunnel.
               |<--------------P2MP PW---------------->|
        Native |                                       |  Native
       Service |     |<--PSN1->|      |<--PSN2->|      |  Service
        (AC)   V     V         V      V         V      V   (AC)
          |    +-----+         +------+         +------+    |
          |    |     |         |   P1 |=========|L-PE2 |AC3 |    +---+
          |    |     |         |   .......PW1.........>|-------->|CE3|
          |    |R-PE1|=========|   .  |=========|      |    |    +---+
          |    |  .......PW1........  |         +------+    |
          |    |  .  |=========|   .  |         +------+    |
          |    |  .  |         |   .  |=========|L-PE3 |AC4 |    +---+
  +---+   |AC1 |  .  |         |   .......PW1.........>|-------->|CE4|
  |CE1|------->|...  |         |      |=========|      |    |    +---+
  +---+   |    |  .  |         +------+         +------+    |
          |    |  .  |         +------+         +------+    |
          |    |  .  |=========|   P2 |=========|L-PE4 |AC5 |    +---+
          |    |  .......PW1..............PW1.........>|-------->|CE5|
          |    |     |=========|      |=========|      |    |    +---+
          |    +-----+         +------+         +------+    |
                           Figure 2: P2MP PW

Jain, et al. Standards Track [Page 6] RFC 8339 P2MP PW TLV for LSP Ping March 2018

 When an operator wants to perform a connectivity check for the P2MP
 PW1, the operator initiates an LSP Ping echo request from Root PE
 R-PE1, with the Target FEC Stack TLV containing the P2MP Pseudowire
 sub-TLV in the echo request packet.  For an Inclusive P2MP Tree
 arrangement, the echo request packet is sent over the P2MP MPLS LSP
 with one of the following two encapsulation options:
 o  {P2MP LSP label, GAL} MPLS label stack and IPv4 or IPv6 ACH.
 o  {P2MP LSP label} MPLS label stack and PW ACH.
 For an Aggregate Inclusive Tree arrangement, the echo request packet
 is sent over the P2MP MPLS LSP with one of the following two
 encapsulation options:
 o  {P2MP LSP label, P2MP PW upstream assigned label, GAL} MPLS label
    stack and IPv4 or IPv6 ACH.
 o  {P2MP LSP label, P2MP PW upstream assigned label} MPLS label stack
    and PW ACH.
 The intermediate P routers do MPLS label swap and replication based
 on the incoming MPLS LSP label.  Once the echo request packet reaches
 L-PEs, L-PEs use the GAL and the IPv4/IPv6 ACH Channel header or PW
 ACH as the case may be, to determine that the packet is an OAM
 Packet.  The L-PEs process the packet and perform checks for the P2MP
 Pseudowire sub-TLV present in the Target FEC Stack TLV as described
 in Section 4.4 in [RFC8029] and respond according to the processing
 rules in that document.

6. Controlling Echo Responses

 The procedures described in [RFC6425] for preventing congestion of
 Echo Responses (Echo Jitter TLV in Section 3.3 of [RFC6425]) and
 limiting the echo reply to a single L-PE (Node Address P2MP Responder
 Identifier TLV in Section 3.2 of [RFC6425]) should be applied to P2MP
 PW LSP Ping.

7. Security Considerations

 The proposal introduced in this document does not introduce any new
 security considerations beyond those that already apply to [RFC6425].

Jain, et al. Standards Track [Page 7] RFC 8339 P2MP PW TLV for LSP Ping March 2018

8. IANA Considerations

 This document defines a new sub-TLV type included in the Target FEC
 Stack TLV (TLV Type 1) [RFC8029] in LSP Ping.
 IANA has assigned the following sub-TLV type value from the "Sub-TLVs
 for TLV Types 1, 16, and 21" sub-registry within the "Multiprotocol
 Label Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters"
 registry:
    37 P2MP Pseudowire

9. References

9.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119,
            DOI 10.17487/RFC2119, March 1997,
            <https://www.rfc-editor.org/info/rfc2119>.
 [RFC4385]  Bryant, S., Swallow, G., Martini, L., and D. McPherson,
            "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
            Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
            February 2006, <https://www.rfc-editor.org/info/rfc4385>.
 [RFC4446]  Martini, L., "IANA Allocations for Pseudowire Edge to Edge
            Emulation (PWE3)", BCP 116, RFC 4446,
            DOI 10.17487/RFC4446, April 2006,
            <https://www.rfc-editor.org/info/rfc4446>.
 [RFC6425]  Saxena, S., Ed., Swallow, G., Ali, Z., Farrel, A.,
            Yasukawa, S., and T. Nadeau, "Detecting Data-Plane
            Failures in Point-to-Multipoint MPLS - Extensions to LSP
            Ping", RFC 6425, DOI 10.17487/RFC6425, November 2011,
            <https://www.rfc-editor.org/info/rfc6425>.
 [RFC6426]  Gray, E., Bahadur, N., Boutros, S., and R. Aggarwal, "MPLS
            On-Demand Connectivity Verification and Route Tracing",
            RFC 6426, DOI 10.17487/RFC6426, November 2011,
            <https://www.rfc-editor.org/info/rfc6426>.
 [RFC7117]  Aggarwal, R., Ed., Kamite, Y., Fang, L., Rekhter, Y., and
            C. Kodeboniya, "Multicast in Virtual Private LAN Service
            (VPLS)", RFC 7117, DOI 10.17487/RFC7117, February 2014,
            <https://www.rfc-editor.org/info/rfc7117>.

Jain, et al. Standards Track [Page 8] RFC 8339 P2MP PW TLV for LSP Ping March 2018

 [RFC8029]  Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
            Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
            Switched (MPLS) Data-Plane Failures", RFC 8029,
            DOI 10.17487/RFC8029, March 2017,
            <https://www.rfc-editor.org/info/rfc8029>.
 [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
            2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
            May 2017, <https://www.rfc-editor.org/info/rfc8174>.
 [RFC8338]  Boutros, S., Ed. and S. Sivabalan, Ed., "Signaling Root-
            Initiated Point-to-Multipoint Pseudowire Using LDP",
            RFC 8338, DOI 10.17487/RFC8338, March 2018,
            <https://www.rfc-editor.org/info/rfc8338>.

9.2. Informative References

 [RFC4875]  Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
            Yasukawa, Ed., "Extensions to Resource Reservation
            Protocol - Traffic Engineering (RSVP-TE) for Point-to-
            Multipoint TE Label Switched Paths (LSPs)", RFC 4875,
            DOI 10.17487/RFC4875, May 2007,
            <https://www.rfc-editor.org/info/rfc4875>.
 [RFC6388]  Wijnands, IJ., Ed., Minei, I., Ed., Kompella, K., and B.
            Thomas, "Label Distribution Protocol Extensions for Point-
            to-Multipoint and Multipoint-to-Multipoint Label Switched
            Paths", RFC 6388, DOI 10.17487/RFC6388, November 2011,
            <https://www.rfc-editor.org/info/rfc6388>.
 [RFC7338]  Jounay, F., Ed., Kamite, Y., Ed., Heron, G., and M. Bocci,
            "Requirements and Framework for Point-to-Multipoint
            Pseudowires over MPLS Packet Switched Networks", RFC 7338,
            DOI 10.17487/RFC7338, September 2014,
            <https://www.rfc-editor.org/info/rfc7338>.

Jain, et al. Standards Track [Page 9] RFC 8339 P2MP PW TLV for LSP Ping March 2018

Acknowledgments

 The authors would like to thank Shaleen Saxena, Greg Mirsky, Andrew
 G. Malis, and Danny Prairie for their valuable input and comments.

Authors' Addresses

 Parag Jain (editor)
 Cisco Systems, Inc.
 2000 Innovation Drive
 Kanata, ON  K2K-3E8
 Canada
 Email: paragj@cisco.com
 Sami Boutros
 VMWare, Inc.
 United States of America
 Email: sboutros@vmware.com
 Sam Aldrin
 Google Inc.
 United States of America
 Email: aldrin.ietf@gmail.com

Jain, et al. Standards Track [Page 10]

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