EVPN Network Layer Fault Management
draft-ietf-bess-evpn-bfd-03

Document Type Active Internet-Draft (bess WG)
Authors Vengada Prasad Govindan  , Mallik Mudigonda , Ali Sajassi  , Greg Mirsky  , Donald Eastlake 
Last updated 2021-02-22
Replaces draft-gmsm-bess-evpn-bfd
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INTERNET-DRAFT                                               V. Govindan
Intended status: Proposed Standard                          M. Mudigonda
                                                              A. Sajassi
                                                           Cisco Systems
                                                               G. Mirsky
                                                                     ZTE
                                                             D. Eastlake
                                                  Futurewei Technologies
Expires: August 21, 2021                               February 22, 2021

                  EVPN Network Layer Fault Management
                      draft-ietf-bess-evpn-bfd-03

Abstract

   This document specifies proactive, in-band network layer OAM
   mechanisms to detect loss of continuity and miss-connection faults
   that affect unicast and multi-destination paths (used by Broadcast,
   Unknown Unicast, and Multicast traffic) in an Ethernet VPN (EVPN)
   network.  The mechanisms specified in the draft are based on the
   widely adopted Bidirectional Forwarding Detection (BFD) protocol.

Status of this Memo

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

   Distribution of this document is unlimited. Comments should be sent
   to the authors or the BESS working group mailing list: bess@ietf.org.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft
   Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

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Table of Contents

      1. Introduction............................................3
      1.1 Terminology............................................3

      2. Scope of this Document..................................5
      3. Motivation for Running BFD at the EVPN Network Layer....6
      4. Fault Detection for Unicast Traffic.....................7

      5. Fault Detection for BUM Traffic.........................8
      5.1 Ingress Replication....................................8
      5.2 P2MP Tunnels (Label Switched Multicast)................8

      6. BFD Packet Encapsulation...............................10
      6.1 MPLS Encapsulation....................................10
      6.1.1 Unicast MPLS Encapsulation..........................10
      6.1.2 MPLS Ingress Replication (MP2P).....................11
      6.1.3 MPLS LSM (Label Switched Multicast, P2MP)...........12
      6.2 VXLAN Encapsulation...................................12
      6.2.1 Unicast VXLAN Encapsulation.........................12
      6.2.2 VXLAN Ingress Replication (MP2P)....................14
      6.2.3 VXLAN LSM (Label Switched Multicast, P2MP)..........14

      7. Scalability Considerations.............................15

      8. IANA Considerations....................................16
      8.1 Pseudowire Associated Channel Type....................16
      8.2 MAC Addresses.........................................16
      8.3 BFD Discriminator Attribute Type......................16

      9. Security Considerations................................17

      Acknowledgements..........................................17

      Normative References......................................18
      Informative References....................................20

      Authors' Addresses........................................21

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1. Introduction

   [ietf-bess-evpn-oam-req-frmwk] outlines the OAM requirements of
   Ethernet VPN networks (EVPN [RFC7432]).  This document specifies
   mechanisms for proactive fault detection at the network (overlay)
   layer of EVPN. The mechanisms proposed in the draft use the widely
   adopted Bidirectional Forwarding Detection (BFD [RFC5880]) protocol.

   EVPN fault detection mechanisms need to consider unicast traffic
   separately from Broadcast, Unknown Unicast, and Multicast (BUM)
   traffic since they map to different Forwarding Equivalency Classes
   (FECs) in EVPN. Hence this document proposes somewhat different fault
   detection mechanisms depending on the type of traffic and the type of
   tunnel used as follows:
      o  Using BFD [RFC5880] for unicast traffic and BUM traffic via
         MP2P tunnels.
      o  Using BFD Multipoint Active Tails [RFC8563] [mirsky-mpls-p2mp-
         bfd] for BUM traffic via a P2MP tunnel.

   Packet loss and packet delay measurement are out of scope for this
   document.

1.1 Terminology

   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.

   The following acronyms are used in this document.

      BFD - Bidirectional Forwarding Detection [RFC5880]

      BUM - Broadcast, Unknown Unicast, and Multicast

      CC - Continuity Check

      CV - Connectivity Verification

      EVI - EVPN Instance

      EVPN - Ethernet VPN [RFC7432]

      FEC - Forwarding Equivalency Class

      GAL - Generic Associated Channel Label [RFC5586]

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      LSM - Label Switched Multicast (P2MP)

      LSP - Label Switched Path

      MP2MP - Multi-Point-to-Multi-Point

      MP2P - Multi-Point-to-Point

      OAM - Operations, Administration, and Maintenance

      P2MP - Point-to-Multi-Point (LSM)

      P2P - Point to Point.

      PE - Provider Edge

      VXLAN - Virtual eXtensible Local Area Network (VXLAN) [RFC7348]

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2. Scope of this Document

   This document specifies BFD based mechanisms for proactive fault
   detection for EVPN as specified in [RFC7432] and also for EVPN using
   VXLAN encapsulation [RFC8365]. It covers the following:

      o  Unicast traffic using Point-to-Point (P2P) and Multi-Point-to-
         Point (MP2P) tunnels.

      o  BUM traffic using Multi-Point-to-Point (MP2P) tunnels (ingress
         replication).

      o  BUM traffic using Point-to-Multi-Point (P2MP) tunnels (Label
         Switched Multicast (LSM)).

      o  MPLS and VXLAN encapsulation.

   This document does not discuss BFD mechanisms for:

      o  EVPN variants like PBB-EVPN [RFC7623].  It is intended to
         address this in future versions.

      o  Integrated Routing and Bridging (IRB) solution based on EVPN
         [ietf-bess-evpn-inter-subnet-forwarding].  It is intended to
         address this in future versions.

      o  EVPN using other encapsulations such as NVGRE or MPLS over GRE
         [RFC8365].

      o  BUM traffic using MP2MP tunnels.

   This document specifies procedures for BFD asynchronous mode. BFD
   demand mode is outside the scope of this specification except as it
   is used in [RFC8563]. The use of the Echo function is outside the
   scope of this specification.

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3. Motivation for Running BFD at the EVPN Network Layer

   The choice of running BFD at the network layer of the OAM model for
   EVPN [ietf-bess-evpn-oam-req-frmwk] was made after considering the
   following:

   o  In addition to detecting link failures in the EVPN network, BFD
      sessions at the network layer can be used to monitor the
      successful setup, such as label programming, of MP2P and P2MP EVPN
      tunnels transporting Unicast and BUM traffic.  The scope of
      reachability detection covers the ingress and the egress EVPN PE
      (Provider Edge) nodes and the network connecting them.

   o  Monitoring a representative set of path(s) or a particular path
      among multiple paths available between two EVPN PE nodes could be
      done by exercising entropy mechanisms such as entropy labels, when
      they are used, or VXLAN source ports.  However, paths that cannot
      be realized by entropy variations cannot be monitored.  The fault
      monitoring requirements outlined by [ietf-bess-evpn-oam-req-frmwk]
      are addressed by the mechanisms proposed by this draft.

   BFD testing between EVPN PE nodes does not guarantee that the EVPN
   service is functioning. (This can be monitored at the service level,
   that is CE to CE.) For example, an egress EVPN-PE could understand
   EVPN labeling received but could switch data to an incorrect
   interface.  However, BFD testing in the EVPN Network Layer does
   provide additional confidence that data transported using those
   tunnels will reach the expected egress node.  When BFD testing in the
   EVPN overlay fails, that can be used as an indication of a Loss-of-
   Connectivity defect in the EVPN underlay that would cause EVPN
   service failure.

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4. Fault Detection for Unicast Traffic

   The mechanisms specified in BFD for MPLS LSPs [RFC5884] [RFC7726]
   are, except as otherwise provided herein, applied to test the
   handling of unicast EVPN traffic.  When discriminators are required
   for de-multiplexing the BFD sessions, they can be advertised through
   BGP using the BFD Discriminator Attribute [ietf-bess-mvpn-fast-
   failover].  Discriminators are needed for MPLS since the label stack
   does not contain enough information to identify the sender of the
   packet.

   The usage of MPLS entropy labels or various VXLAN source ports takes
   care of the requirement to monitor various paths of the multi-path
   server layer network [RFC6790].  Each unique realizable path between
   the participating PE routers MAY be monitored separately when such
   entropy is used.  At least one path of multi-path connectivity
   between two PE routers MUST be tracked with BFD, but in that case the
   granularity of fault-detection will be coarser.

   To support unicast fault management to a PE node, that PE MUST
   allocate or be configured with a BFD discriminator to be used for the
   BFD messages to it. By default, it advertises this discriminator with
   BGP using the BFD Discriminator Attribute [ietf-bess-mvpn-fast-
   failover] with BFD Mode TBD4 in an EVPN MAC/IP Advertisement Route
   [RFC7432] and extracts its peer's discriminator from such an
   attribute. however, these discriminators MAY be exchanged out-of-band
   or through some other mechanism outside the scope of this document.

   If configured to do so, once a PE knows a unicast route and
   discriminator for another PE, it endeavors to bring UP and maintain a
   BFD session to that other PE. Once the BFD session is UP, the ends of
   the BFD session MUST NOT change the local discriminator values of the
   BFD Control packets they generate, unless they first bring down the
   session as specified in [RFC5884].  The BFD session is brought down
   if a PE is no longer configured to maintain it or if a route and
   discriminator are no longer available.

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5. Fault Detection for BUM Traffic

   Section 5.1 below discusses BUM traffic fault detection for MP2P
   tunnels using ingress replication and Section 5.2 discusses such
   fault detection for P2MP tunnels.

5.1 Ingress Replication

   Ingress replication uses separate MP2P tunnels for transporting BUM
   traffic from the ingress PE (head) to a set of one or more egress PEs
   (tails).  The fault detection mechanism specified by this document
   takes advantage of the fact that the head makes a unique copy for
   each tail.

   Another key aspect to be considered in EVPN is the advertisement of
   the Inclusive Multicast Ethernet Tag Route [RFC7432].  The BUM
   traffic flows from a head node to a particular tail only after the
   head receives such inclusive multicast route from the tail. This
   route contains the BUM EVPN MPLS label (downstream allocated)
   corresponding to the MP2P tunnel for MPLS encapsulation and contains
   the IP address of the PE originating the inclusive multicast route
   for use in VXLAN encapsulation. It also contains a BFD Discriminator
   Attribute [ietf-bess-mvpn-fast-failover] with BFD Mode TDB4 giving
   the BFD discriminator that will be used by the tail. This is the P2P
   mode since a P2P BFD session is used in the MP2P case.

   There MAY exist multiple BFD sessions between a head PE and an
   individual tail due to (1) the usage of MPLS entropy labels [RFC6790]
   or VXLAN source ports for an inclusive multicast FEC and (2) due to
   multiple MP2P tunnels indicated by different tail labels or IP
   addresses for MPLS or VXLAN. If configured to do so, once a PE knows
   a multicast route and discriminator for another PE it endeavors to
   bring UP and maintain a BFD session to that other PE. Once a BFD
   session for a path is UP, the ends of the BFD session MUST NOT change
   the local discriminator values of the BFD Control packets they
   generate, unless they first bring down the session as specified in
   [RFC5884]. The BFD session is brought down if a PE is no longer
   configured to maintain it or if a route and discriminator are no
   longer available.

5.2 P2MP Tunnels (Label Switched Multicast)

   Fault detection for BUM traffic distributed using a P2MP tunnel uses
   BFD Multipoint Active Tails in one of the three methods providing
   head notification depending on configuration. Sections 5.2.2 and
   5.2.3 of [RFC8563] describe two of these methods ("Head Notification

Govindan, et al                                                 [Page 8]
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   and Tail Solicitation with Multipoint Polling" and "Head Notification
   with Composite Polling").  The third method ("Head Notification
   without Polling") is touched on in Section 5.2.1 of [RFC8563] and
   fully specified in [mirsky-mpls-p2mp-bfd].  All three of these modes
   assume the existence of a unicast path from each tail to the head. In
   addition, Head Notification with Composite Polling assumes a head to
   tail unicast path.

   The BUM traffic flows from a head node to the tails after the head
   receives an Inclusive Multicast Tag Route [RFC7432]. This contains
   the BUM EVPN MPLS label (upstream allocated) corresponding to the
   P2MP tunnel for MPLS encapsulation. It also contains a BFD
   Discriminator Attribute [ietf-bess-mvpn-fast-failover] with BFD Mode
   1 and with a Source IP Address TLV giving the address associated with
   the MultiPoint Head of the P2MP session.  This BFD discriminator
   advertised by a tail in the inclusive multicast route or otherwise
   configured at or communicated to the head MUST be used in any reverse
   unicast traffic so the head can determine which tail is responding.
   If configured to do so, once a PE knows a P2MP multicast route and
   needed discriminators, it brings UP and maintains a BFD active tails
   session to the tails.  The BFD session is brought down if a PE is no
   longer configured to maintain it or if the multicast route and
   discriminators are no longer available.

   For MPLS encapsulation of the head to tails BFD, Label Switched
   Multicast is used. For VXLAN encapsulation, BFD is delivered to the
   tails through underlay multicast using an outer multicast IP address.

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6. BFD Packet Encapsulation

   The sections below discuss the MPLS and VXLAN encapsulations of BFD
   for EVPN network layer fault management.

6.1 MPLS Encapsulation

   This section describes use of the Generic Associated Channel Label
   (GAL) for BFD encapsulation in MPLS based EVPN network layer fault
   management.

6.1.1 Unicast MPLS Encapsulation

   As shown in Figure 1, the packet initially contains the following
   labels: LSP label (transport), the optional entropy label, the EVPN
   Unicast label, and then the Generic Associated Channel label with the
   G-ACh type set to TBD1.  The G-ACh payload of the packet MUST contain
   the destination L2 header (in overlay space) followed by the IP
   header that encapsulates the BFD packet.  The MAC address of the
   inner packet is used to validate the <EVI, MAC> in the receiving
   node.

      - The destination MAC MUST be the dedicated unicast MAC TBD3 (see
        Section 8) or the MAC address of the destination PE.
      - The destination IP address MUST be 127.0.0.1/32 for IPv4
        [RFC1812] or ::1/128 for IPv6 [RFC4291].
      - The destination IP port MUST be 3784 [RFC5881].
      - The source IP port MUST be in the range 49152 through 65535.
      - The discriminator values for BFD are obtained through BGP as
        discussed in Section 4.

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       <---------- 4 bytes ---------->
      +-------------------------------+  -----
      |          LSP Label            |      |
      +-------------------------------+      |
      :      entropy label indicator  :      |
      + (optional)                    +  MPLS Label Stack
      :      entropy label            :      |
      +-------------------------------+      |
      |      EVPN Unicast label       |
      +-------------------------------+      |
      | Generic Assoc. Channel Label  |      |
      +-------------------------------+  -----
      |  ACH word, Type TBD1 no TLVs  |
      +-------------------------------+  ---     -------
      |    Destination MAC Address    |    |           |
      +               +---------------+    |           |
      |   TBD2        |               |    |           |
      +---------------+               +  L2 Header     |
      |       Source MAC Address      |    |           |
      +---------------+---------------+    |           |
      | VLAN Ethertype|     VLAN-ID   |    |           |
      +---------------+---------------+    |           |
      |IP4/6 Ethertype|                    |           |
      +---------------+---------------+  ---           |
      /                               /           G-ACh Payload
      /...      IPv4/6 Header      .../                |
      /                               /                |
      +-------------------------------+                |
      |                               |                |
      +           UDP Header          +                |
      |                               |                |
      +-------------------------------+                |
      |                               |                |
      +       BFD Control Packet      +                |
      /                               /                |
      /...                         .../  ---------------

                   Figure 1. MPLS Unicast Encapsulation

6.1.2 MPLS Ingress Replication (MP2P)

   The packet initially contains the following labels: LSP label
   (transport), the optional entropy label, the BUM label, and the split
   horizon label [RFC7432] (where applicable).  The G-ACh type is set to
   TBD1.  The G-ACh payload of the packet is as described in Section
   6.1.1 except that the destination MAC address is the dedicated
   multicast MAC TBD2.

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6.1.3 MPLS LSM (Label Switched Multicast, P2MP)

   The encapsulation is the same as in Section 6.1.2 for ingress
   replication except that the transport label identifies the P2MP
   tunnel, in effect the set of tail PEs, rather than identifying a
   single destination PE at the end of an MP2P tunnel.

6.2 VXLAN Encapsulation

   This section describes the use of the VXLAN [RFC7348] [RFC8365] for
   BFD encapsulation in VXLAN based EVPN fault management.

6.2.1 Unicast VXLAN Encapsulation

   Figure 2 below shows the unicast VXLAN encapsulation.  The outer and
   inner IP headers have a unicast source IP address of the BFD message
   source and a destination IP address of the BFD message destination

   The destination UDP port MUST be 3784 [RFC5881]. The source port MUST
   be in the range 49152 through 65535. If the BFD source has multiple
   IP addresses, entropy MAY be further obtained by using any of those
   addresses assuming the source is prepared for responses directed to
   the IP address used.

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       <---------- 4 bytes ---------->
      +-------------------------------+  ---
      |    Destination MAC Address    |    |
      +               +---------------+    |
      |               |               |    |
      +---------------+               +  L2 Header
      |       Source MAC Address      |    |
      +-------------------------------+    |
      | VLAN Ethertype|     VLAN-ID   |    |
      +---------------+---------------+    |
      |IP4/6 Ethertype|                    |
      +---------------+---------------+  ---
      /                               /
      /...      IP4/6 Header       .../
      /                               /
      +-------------------------------+
      |                               |
      +           UDP Header          +
      |                               |
      +-------------------------------+
      |                               |
      +          VXLAN Header         +
      |                               |
      +-------------------------------+  ---
      |    Destination MAC Address    |    |
      +               +---------------+    |
      |               |               |    |
      +---------------+               +  L2 Header
      |       Source MAC Address      |    |
      +---------------+---------------+    |
      | IP4 Ethertype |                    |
      +---------------+---------------+  ---
      /                               /
      /...       IP4 Header        .../
      /                               /
      +-------------------------------+
      |                               |
      +           UDP Header          +
      |                               |
      +---------------+---------------+
      |                               |
      +       BFD Control Packet      +
      |                               |
      /...                         .../

                   Figure 2. VXLAN Unicast Encapsulation

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6.2.2 VXLAN Ingress Replication (MP2P)

   The BFD packet construction is as given in Section 6.2.1 except as
   follows:

   (1) The destination IP address used by the BFD message source is that
       advertised by the destination PE in its Inclusive Multicast EVPN
       route for the MP2P tunnel in question; and

   (2) The Your BFD discriminator used is the one advertised by the BFD
       destination using BGP as discussed in Section 5.1 for the MP2P
       tunnel.

6.2.3 VXLAN P2MP

   The VXLAN encapsulation for the head-to-tails BFD packets uses the
   multicast destination IP corresponding to the VXLAN VNI.

   The destination port MUST be 3784. For entropy purposes, the source
   port can vary but MUST be in the range 49152 through 65535 [RFC5881].
   If the head PE has multiple IP addresses, entropy MAY be further
   obtained by using any of those addresses.

   The Your BFD discriminator is the value distributed for this
   multicast fault management purpose as discussed in Section 5.2.

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7. Scalability Considerations

   The mechanisms proposed by this draft could affect the packet load on
   the network and its elements especially when supporting
   configurations involving a large number of EVIs.  The option of
   slowing down or speeding up BFD timer values can be used by an
   administrator or a network management entity to maintain the overhead
   incurred due to fault monitoring at an acceptable level.

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8. IANA Considerations

   The following IANA Actions are requested.

8.1 Pseudowire Associated Channel Type

   IANA is requested to assign a channel type from the "Pseudowire
   Associated Channel Types" registry in [RFC4385] as follows.

         Value   Description    Reference
         -----   ------------   ------------
         TBD1    BFD-EVPN OAM   [this document]

8.2 MAC Addresses

   IANA is requested to assign parallel multicast and unicast MAC
   addresses under the IANA OUI [0x01005E900101 and 0x00005E900101
   suggested] as follows:

     IANA Multicast 48-bit MAC Addresses
         Address   Usage                  Reference
         -------  ---------------------   ---------------
         TBD2    EVPN Network Layer OAM   [this document]

     IANA Unicast 48-bit MAC Addresses
         Address   Usage                  Reference
         -------  ---------------------   ---------------
         TBD3    EVPN Network Layer OAM   [this document]

8.3 BFD Discriminator Attribute Type

   IANA is requested to assign a value from the IETF Review range in the
   BFD Mode sub-registry on the Border Gateway Protocol Parameters
   Registry web page as follows:

         Value    Description      Reference
         -----   ---------------   ---------------
         TBD4    P2P BFD Session   [this document]

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9. Security Considerations

   Security considerations discussed in [RFC5880], [RFC5883], and
   [RFC8029] apply.

   MPLS security considerations [RFC5920] apply to BFD Control packets
   encapsulated in a MPLS label stack. When BPD Control packets are
   routed, the authentication considerations discussed in [RFC5883]
   should be followed.

   VXLAN BFD security considerations in [RFC8971] apply to BFD packets
   encapsulate in VXLAN.

Acknowledgements

   The authors wish to thank the following for their comments and
   suggestions:

      Mach Chen

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Normative References

   [ietf-bess-mvpn-fast-failover] Morin, T., Kebler, R., Mirsky, G.,
             "Multicast VPN fast upstream failover",
             draft-ietf-bess-mvpn-fast-failover (in RFC Editor's queue),
             February 2019.

   [mirsky-mpls-p2mp-bfd] G. Mirsky, S. Mishra, "BFD for Multipoint
             Networks over Point-to-Multi-Point MPLS LSP", draft-mirsky-
             mpls-p2mp-bfd (work in progress), November 2020.

   [RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers",
             RFC 1812, DOI 10.17487/RFC1812, June 1995,
             <https://www.rfc-editor.org/info/rfc1812>.

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, DOI
             10.17487/RFC2119, March 1997, <http://www.rfc-
             editor.org/info/rfc2119>.

   [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
             Architecture", RFC 4291, DOI 10.17487/RFC4291, February
             2006, <https://www.rfc-editor.org/info/rfc4291>.

   [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, <http://www.rfc-editor.org/info/rfc4385>.

   [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
             "MPLS Generic Associated Channel", RFC 5586, DOI
             10.17487/RFC5586, June 2009, <https://www.rfc-
             editor.org/info/rfc5586>.

   [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
             (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
             <http://www.rfc-editor.org/info/rfc5880>.

   [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
             (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, DOI
             10.17487/RFC5881, June 2010, <https://www.rfc-
             editor.org/info/rfc5881>.

   [RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
             (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,
             June 2010, <https://www.rfc-editor.org/info/rfc5883>.

Govindan, et al                                                [Page 18]
Internet-Draft                       EVPN Network Layer Fault Management

   [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
             "Bidirectional Forwarding Detection (BFD) for MPLS Label
             Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
             June 2010, <https://www.rfc-editor.org/info/rfc5884>.

   [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and L.
             Yong, "The Use of Entropy Labels in MPLS Forwarding", RFC
             6790, DOI 10.17487/RFC6790, November 2012, <http://www.rfc-
             editor.org/info/rfc6790>.

   [RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
             L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
             eXtensible Local Area Network (VXLAN): A Framework for
             Overlaying Virtualized Layer 2 Networks over Layer 3
             Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
             <https://www.rfc-editor.org/info/rfc7348>.

   [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
             Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
             Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
             2015, <http://www.rfc-editor.org/info/rfc7432>.

   [RFC7726] Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S.
             Aldrin, "Clarifying Procedures for Establishing BFD
             Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726,
             DOI 10.17487/RFC7726, January 2016, <https://www.rfc-
             editor.org/info/rfc7726>.

   [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>.

   [RFC8365] Sajassi, A., Ed., Drake, J., Ed., Bitar, N., Shekhar, R.,
             Uttaro, J., and W. Henderickx, "A Network Virtualization
             Overlay Solution Using Ethernet VPN (EVPN)", RFC 8365, DOI
             10.17487/RFC8365, March 2018, <https://www.rfc-
             editor.org/info/rfc8365>.

   [RFC8563] Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky,
             Ed., "Bidirectional Forwarding Detection (BFD) Multipoint
             Active Tails", RFC 8563, DOI 10.17487/RFC8563, April 2019,
             <https://www.rfc-editor.org/info/rfc8563>.

Govindan, et al                                                [Page 19]
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Informative References

   [ietf-bess-evpn-inter-subnet-forwarding] Sajassi, A., Salam, S.,
             Thoria, S., Rekhter, Y., Drake, J., Yong, L., and L.
             Dunbar, "Integrated Routing and Bridging in EVPN",
             draft-ietf-bess-evpn-inter-subnet-forwarding-13 (work in
             progress), February 2021.

   [ietf-bess-evpn-oam-req-frmwk] Salam, S., Sajassi, A., Aldrin, S., J.
             Drake, and D. Eastlake, "EVPN Operations, Administration
             and Maintenance Requirements and Framework",
             draft-ietf-bess-evpn-oam-req-frmwk-04, work in progress,
             July 2019.

   [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
             Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
             <https://www.rfc-editor.org/info/rfc5920>.

   [RFC7623] Sajassi, A., Ed., Salam, S., Bitar, N., Isaac, A., and W.
             Henderickx, "Provider Backbone Bridging Combined with
             Ethernet VPN (PBB-EVPN)", RFC 7623, DOI 10.17487/RFC7623,
             September 2015, <http://www.rfc-editor.org/info/rfc7623>.

   [RFC8971] Pallagatti, S., Ed., Mirsky, G., Ed., Paragiri, S.,
             Govindan, V., and M. Mudigonda, "Bidirectional Forwarding
             Detection (BFD) for Virtual eXtensible Local Area Network
             (VXLAN)", RFC 8971, DOI 10.17487/RFC8971, December 2020,
             <https://www.rfc-editor.org/info/rfc8971>.

Govindan, et al                                                [Page 20]
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Authors' Addresses

      Vengada Prasad Govindan
      Cisco Systems

      Email: venggovi@cisco.com

      Mudigonda Mallik
      Cisco Systems

      Email: mmudigon@cisco.com

      Ali Sajassi
      Cisco Systems
      170 West Tasman Drive
      San Jose, CA  95134, USA

      Email: sajassi@cisco.com

      Gregory Mirsky
      ZTE Corp.

      Email: gregimirsky@gmail.com

      Donald Eastlake, 3rd
      Futurewei Technologies
      2386 Panoramic Circle
      Apopka, FL 32703 USA

      Phone: +1-508-333-2270
      Email: d3e3e3@gmail.com

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Copyright, Disclaimer, and Additional IPR Provisions

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   document authors. All rights reserved.

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   described in the Simplified BSD License.

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