BIER WG                                                         Q. Xiong
Internet-Draft                                           ZTE Corporation
Intended status: Standards Track                               G. Mirsky
Expires: 6 November 2022                                        Ericsson
                                                                   F. Hu
                                                              Individual
                                                                  C. Liu
                                                            China Unicom
                                                              5 May 2022


                                BIER BFD
                         draft-ietf-bier-bfd-02

Abstract

   Point to multipoint (P2MP) BFD is designed to verify multipoint
   connectivity.  This document specifies the application of P2MP BFD in
   BIER network.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on 6 November 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.










Xiong, et al.            Expires 6 November 2022                [Page 1]


Internet-Draft                  BIER BFD                        May 2022


   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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   3.  BIER BFD Encapsulation  . . . . . . . . . . . . . . . . . . .   3
   4.  BIER BFD Session Bootstrapping  . . . . . . . . . . . . . . .   3
     4.1.  BIER OAM Bootstrapping  . . . . . . . . . . . . . . . . .   4
     4.2.  IGP Protocol Bootstrapping  . . . . . . . . . . . . . . .   4
       4.2.1.  IS-IS Extension for BIER BFD  . . . . . . . . . . . .   5
       4.2.2.  OSPF Extension for BIER BFD . . . . . . . . . . . . .   6
   5.  Discriminators and Packet Demultiplexing  . . . . . . . . . .   7
   6.  Active Tail in BIER BFD . . . . . . . . . . . . . . . . . . .   7
     6.1.  Unsolicited Head Notification Mode  . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  BIER OAM Message Type . . . . . . . . . . . . . . . . . .   8
     9.2.  BFD Discriminator TLV . . . . . . . . . . . . . . . . . .   9
     9.3.  BIER BFD Sub-sub-TLV  . . . . . . . . . . . . . . . . . .   9
     9.4.  BIER BFD Sub-TLV  . . . . . . . . . . . . . . . . . . . .   9
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   Bit Index Explicit Replication (BIER) [RFC8279] provides the
   forwarding of multicast data packets through a multicast domain.  It
   does so without requiring any explicit tree-building protocol and
   without requiring intermediate nodes to maintain any per-flow state.

   [RFC8562] defines a method of using Bidirectional Forwarding
   Detection (BFD) to monitor and detect unicast failures between the
   sender (head) and one or more receivers (tails) in multipoint or
   multicast networks.  [RFC8563] describes active tail extensions to
   the BFD protocol for multipoint networks.




Xiong, et al.            Expires 6 November 2022                [Page 2]


Internet-Draft                  BIER BFD                        May 2022


   This document describes the procedures for using such mode of BFD
   protocol to monitor connectivity between a multipoint sender, Bit-
   Forwarding Ingress Router (BFIR), and a set of one or more multipoint
   receivers, Bit-Forwarding Egress Routers (BFERs).  The BIER BFD only
   supports the unidirectional multicast.  This document defines the use
   of P2MP BFD as per [RFC8562], and active tail as per [RFC8563] for
   BIER-specific domain.

2.  Conventions used in this document

2.1.  Terminology

   This document uses the acronyms defined in [RFC8279] along with the
   following:

   BFD: Bidirectional Forwarding Detection.

   OAM: Operations, Administration, and Maintenance.

   P2MP: Point to Multi-Point.

2.2.  Requirements Language

   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.

3.  BIER BFD Encapsulation

   BIER BFD encapsulation uses the BIER OAM packet format defined in
   [I-D.ietf-bier-ping].  The value of the Message Type field MUST be
   set to BIER BFD (TBD1 will be assigned by IANA Section 9.1).  BFD
   Control packet, defined in Section 4 [RFC5880], immediately follows
   the BIER OAM header.  The operation of Multipoint BFD with the BFD
   Control Packet is described in [RFC8562].

4.  BIER BFD Session Bootstrapping

   As defined in [RFC8562], a BIER BFD session MAY be established to
   monitor the state of the multipoint path.  The BIER BFD session could
   be created for each multipoint path and the set of BFERs over which
   the BFIR is requested to run BIER BFD.  The BFIR MUST advertise the
   multipoint path and the value of My Discriminator associated with the
   path to the set of BFERs.  Bootstrapping a BIER BFD session MAY use
   BIER OAM message Section 4.1 or the control plane Section 4.2.




Xiong, et al.            Expires 6 November 2022                [Page 3]


Internet-Draft                  BIER BFD                        May 2022


   The BIER BFD bootstrapping MUST be repeated when the value of this
   discriminator being changed.

4.1.  BIER OAM Bootstrapping

   The BIER OAM could be used for bootstrapping the BIER BFD session.
   The BFIR sends the BIER OAM Echo request message carrying a BFD
   discriminator TLV which immediately follows the Target SI-Bitstring
   TLV (section 3.3.2 [I-D.ietf-bier-ping]).

   The Target SI-Bitstring TLV MUST be used to carry the set of BFER
   information (including Sub-domain-id, Set ID, BS Len, Bitstring) for
   the purpose of the session establishment.

   Figure 1 displays the format of BFD Discriminator TLV.


       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         Type = TBD2           |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                        My Discriminator                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 1: BFD Discriminator TLV


   where:

   *  Type indicates BFD Discriminator TLV.  The value (TBD2) is to be
      allocated by IANA (Section 9.2).

   *  Length MUST be set to 4.

   *  My Discriminator - four-octet long field.  The value is the local
      discriminator generated by BFIR for this session.  This
      discriminator MUST be used as the My Discriminator field n the
      BIER BFD Control packets sent by the BFIR.

4.2.  IGP Protocol Bootstrapping

   An alternative option to bootstrap the BIER BFD is to advertise the
   BFD information in the control plane.  This document defines a new
   BIER BFD Sub-sub-TLV carried in IGP protocol including IS-IS and
   OSPF.





Xiong, et al.            Expires 6 November 2022                [Page 4]


Internet-Draft                  BIER BFD                        May 2022


   The BFIR generates the My Discriminator value for each multicast flow
   and advertises it to the expecting BFERs, which is indicated by the
   Bitstring and the BIFT-id, which is carried in BIER BFD sub-sub-TLV.
   The corresponding BFERs SHOULD store the My Discriminator value for
   packet Demultiplexing.

4.2.1.  IS-IS Extension for BIER BFD

   The new BIER BFD Sub-sub-TLV is carried within the BIER Info sub-TLV
   defined in [RFC8401].  The format is displayed in Figure 2.


        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Type = TBD3  |     Length    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      My Discriminator                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     RESERVED          |            BIFT-id                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                 BitString  (first 32 bits)                    ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                                                               ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                 BitString  (last 32 bits)                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 2: BIER BFD Sub-sub-TLV for IS-IS Extension


   where:

   *  Type indicates BIER BFD sub-sub-TLV.  The value (TBD3) is to be
      allocated by IANA (Section 9.3).

   *  Length is a two-octet field.  The value is the length of the BIER
      BFD Sub-sub-TLV for IS-IS extension, in octets

   *  My Discriminator is a four-octet long field.  The value is a
      unique, nonzero discriminator value generated by BFIR for each
      multipoint path.  This discriminator MUST be used as the My
      Discriminator field n the BIER BFD Control packets sent by the
      BFIR.

   *  BIFT-id is a two-octet field.  The value represents a particular
      Bit Index Forwarding Table (BIFT) as per [RFC8279].




Xiong, et al.            Expires 6 November 2022                [Page 5]


Internet-Draft                  BIER BFD                        May 2022


   *  BitString field carries the set of BFR-IDs of BFER(s) that the
      BFIR expects to establish the BIER BFD session.

4.2.2.  OSPF Extension for BIER BFD

   The new BIER BFD Sub-TLV is a sub-TLV of the BIER Sub-TLV defined in
   [RFC8444].  The format is displayed in Figure 3.


      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Type = TBD4             |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        My Discriminator                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     RESERVED          |            BIFT-id                    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                 BitString  (first 32 bits)                    ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                 BitString  (last 32 bits)                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 3: BIER BFD Sub-TLV for OSPF extension


           Figure 3: BIER BFD Sub-sub-TLV for IS-IS Extension


   where:

   *  Type indicates BIER BFD sub-TLV.  The value (TBD4) is to be
      allocated by IANA (Section 9.4).

   *  Length is a two-octet field.  The value is the length of the BIER
      BFD sub-TLV for OSPF extension, in octets

   *  My Discriminator is a four-octet long field.  The value is a
      unique, nonzero discriminator value generated by BFIR for each
      multipoint path.  This discriminator MUST be used as the My
      Discriminator field n the BIER BFD Control packets sent by the
      BFIR.

   *  BIFT-id is a two-octet field.  The value represents a particular
      Bit Index Forwarding Table (BIFT) as per [RFC8279].




Xiong, et al.            Expires 6 November 2022                [Page 6]


Internet-Draft                  BIER BFD                        May 2022


   *  BitString field carries the set of BFR-IDs of BFER(s) that the
      BFIR expects to establish the BIER BFD session.

5.  Discriminators and Packet Demultiplexing

   As defined in [RFC8562], the BFIR sends BFD Control packets to the
   set of BFERs over the multipoint path via the BIER BFD session with
   My Discriminator is set to the value assigned by the BFIR, and the
   value of the Your Discriminator is set to zero.  The set of BFERs
   MUST demultiplex BFD packets based on a combination of the source
   address, My Discriminator value.  The source address is BFIR-id and
   BIER MPLS Label (MPLS network) or BFIR-id and BIFT-id (Non-MPLS
   network) for BIER BFD.  My Discriminator value is advertised in BIER
   BFD bootstrapping using one of the options described in Section 4.

6.  Active Tail in BIER BFD

   [RFC8563] defined an extension for Multipoint BFD, which allows the
   head to discover the state of a multicast distribution tree for any
   sub-set of tails.  For BIER BFD in the active tail mode, the BFIR may
   learn the state and connectivity of the BFERs by allowing the BFERs
   to notify the BFIR.  As per [RFC8563] provides detailed information
   on how the BFIR can use multipoint Poll sequence message or a
   combination of multicast and unicast Poll sequence messages to
   determine the state of the multicast tree.  Also, [RFC8563] describes
   that a BFER can transmit an unsolicited unicast Poll sequence message
   to the BFIR (note that a unicast message must be sent over a path
   which is disjoint from the multicast distribution tree).

6.1.  Unsolicited Head Notification Mode

   [I-D.ietf-mpls-p2mp-bfd] provides detailed information on using the
   unsolicited notification method for P2MP MPLS LSP, which is also
   applicable to BIER.

   In Section 5.2.1 [RFC8563] is noted that "the tail sends unsolicited
   BFD packets in response to the detection of a multipoint path
   failure" but without the specifics on the information in the packet
   and frequency of transmissions.  This document defines the procedure
   of the active tail with unsolicited notifications for BIER as
   specified below.

   Upon detecting the failure, a BFER sends a BFD control packet with
   the following settings:

   *  the Poll (P) bit is set;

   *  the Status (Sta) field is set to Down value;



Xiong, et al.            Expires 6 November 2022                [Page 7]


Internet-Draft                  BIER BFD                        May 2022


   *  the Diagnostic (Diag) field is set to Control Detection Time
      Expired value;

   *  the value of the Your Discriminator field is set to the value the
      BFER has been used to demultiplex that BFD multipoint session;

   *  BFD Control packet is encapsulated in IP/UDP with the destination
      IP address of the BFIR and the UDP destination port number set to
      4784 per [RFC5883]

   *  the BFD Control packets are transmitted at the rate of one per
      second until either the BFER receives valid for this BFD session
      control packet with the Final (F) bit is set from the BFIR or the
      defect condition clears.

   To improve the likelihood of notifying the BFIR of the failure, the
   BFER SHOULD transmit three BFD Control packets defined above in short
   succession.

   A BFIR that has received the BFD Control packet, as described above,
   sends the unicast IP/UDP encapsulated BFD control packet with the
   Final (F) bit set to the BFER.

7.  Security Considerations

   For BIER OAM packet processing security considerations, see
   [I-D.ietf-bier-ping].

   For general multipoint BFD security considerations, see [RFC8562].

   No additional security issues are raised in this document beyond
   those that exist in the referenced BFD documents.

8.  Acknowledgements

   The authors would like to thank the comments and suggestions from
   Sandy Zhang, Jeffrey (Zhaohui) Zhang, Donald Eastlake 3rd.

9.  IANA Considerations

9.1.  BIER OAM Message Type

   IANA is requested to assign a new type from the BIER OAM Message Type
   registry as follows:







Xiong, et al.            Expires 6 November 2022                [Page 8]


Internet-Draft                  BIER BFD                        May 2022


                 +=======+=============+=================+
                 | Value | Description |    Reference    |
                 +=======+=============+=================+
                 |  TBD1 | BIER BFD    | [this document] |
                 +-------+-------------+-----------------+

                                  Table 1

9.2.  BFD Discriminator TLV

   IANA is requested to assign a new type from the BIER OAM TLV registry
   as follows:

            +=======+=======================+=================+
            | Value | Description           |    Reference    |
            +=======+=======================+=================+
            |  TBD2 | BFD discriminator TLV | [this document] |
            +-------+-----------------------+-----------------+

                                  Table 2

9.3.  BIER BFD Sub-sub-TLV

   IANA is requested to assign a new BIER BFD Sub-sub-TLV within the
   BIER Info sub-TLV registry is defined in [RFC8401] as follows:

            +=======+======================+=================+
            | Value | Description          |    Reference    |
            +=======+======================+=================+
            |  TBD3 | BIER BFD Sub-sub-TLV | [this document] |
            +-------+----------------------+-----------------+

                                 Table 3

9.4.  BIER BFD Sub-TLV

   IANA is requested to assign a new BIER BFD Sub-TLV from the BIER Sub-
   TLV registry is defined in [RFC8444] as follows:

              +=======+==================+=================+
              | Value | Description      |    Reference    |
              +=======+==================+=================+
              |  TBD4 | BIER BFD Sub-TLV | [this document] |
              +-------+------------------+-----------------+

                                 Table 4

10.  References



Xiong, et al.            Expires 6 November 2022                [Page 9]


Internet-Draft                  BIER BFD                        May 2022


10.1.  Normative References

   [I-D.ietf-bier-ping]
              Kumar, N., Pignataro, C., Akiya, N., Zheng, L., Chen, M.,
              and G. Mirsky, "BIER Ping and Trace", Work in Progress,
              Internet-Draft, draft-ietf-bier-ping-07, 11 May 2020,
              <https://datatracker.ietf.org/doc/html/draft-ietf-bier-
              ping-07>.

   [I-D.ietf-mpls-p2mp-bfd]
              Mirsky, G., Mishra, G., and D. E. 3rd, "BFD for Multipoint
              Networks over Point-to-Multi-Point MPLS LSP", Work in
              Progress, Internet-Draft, draft-ietf-mpls-p2mp-bfd-01, 10
              February 2022, <https://datatracker.ietf.org/doc/html/
              draft-ietf-mpls-p2mp-bfd-01>.

   [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>.

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

   [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>.

   [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>.

   [RFC8279]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
              Explicit Replication (BIER)", RFC 8279,
              DOI 10.17487/RFC8279, November 2017,
              <https://www.rfc-editor.org/info/rfc8279>.

   [RFC8401]  Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z.
              Zhang, "Bit Index Explicit Replication (BIER) Support via
              IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018,
              <https://www.rfc-editor.org/info/rfc8401>.








Xiong, et al.            Expires 6 November 2022               [Page 10]


Internet-Draft                  BIER BFD                        May 2022


   [RFC8444]  Psenak, P., Ed., Kumar, N., Wijnands, IJ., Dolganow, A.,
              Przygienda, T., Zhang, J., and S. Aldrin, "OSPFv2
              Extensions for Bit Index Explicit Replication (BIER)",
              RFC 8444, DOI 10.17487/RFC8444, November 2018,
              <https://www.rfc-editor.org/info/rfc8444>.

   [RFC8562]  Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky,
              Ed., "Bidirectional Forwarding Detection (BFD) for
              Multipoint Networks", RFC 8562, DOI 10.17487/RFC8562,
              April 2019, <https://www.rfc-editor.org/info/rfc8562>.

   [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>.

Authors' Addresses

   Quan Xiong
   ZTE Corporation
   No.6 Huashi Park Rd
   Wuhan
   Hubei, 430223
   China
   Phone: +86 27 83531060
   Email: xiong.quan@zte.com.cn


   Greg Mirsky
   Ericsson
   Email: gregimirsky@gmail.com


   Fangwei Hu
   Individual
   Email: hufwei@gmail.com


   Chang Liu
   China Unicom
   No.9 Shouti Nanlu
   Beijing
   100048
   China
   Phone: +86-010-68799999-7294
   Email: liuc131@chinaunicom.cn





Xiong, et al.            Expires 6 November 2022               [Page 11]