Multicast On-path Telemetry Solutions
draft-ietf-mboned-multicast-telemetry-02

MBONED                                                           H. Song
Internet-Draft                                                M. McBride
Intended status: Standards Track                  Futurewei Technologies
Expires: 8 July 2022                                           G. Mirsky
                                                               ZTE Corp.
                                                               G. Mishra
                                                            Verizon Inc.
                                                               H. Asaeda
                                                                    NICT
                                                                 T. Zhou
                                                                  Huawei
                                                          4 January 2022

                 Multicast On-path Telemetry Solutions
                draft-ietf-mboned-multicast-telemetry-02

Abstract

   This document discusses the requirement of on-path telemetry for
   multicast traffic.  The existing solutions are examined and their
   issues are identified.  Solution modifications are proposed to allow
   the original multicast tree to be correctly reconstructed without
   unnecessary replication of telemetry information.

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.

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."

Song, et al.               Expires 8 July 2022                  [Page 1]
Internet-Draft             Multicast Telemetry              January 2022

   This Internet-Draft will expire on 8 July 2022.

Copyright Notice

   Copyright (c) 2022 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 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.  Requirements for Multicast Traffic Telemetry  . . . . . . . .   3
   3.  Issues of Existing Techniques . . . . . . . . . . . . . . . .   4
   4.  Proposed Modifications to Existing Techniques . . . . . . . .   5
     4.1.  Per-hop postcard using IOAM DEX . . . . . . . . . . . . .   5
     4.2.  Per-section postcard  . . . . . . . . . . . . . . . . . .   7
   5.  Considerations for Different Multicast Protocols  . . . . . .   8
     5.1.  Application in PIM  . . . . . . . . . . . . . . . . . . .   8
     5.2.  Application of MVPN X-PMSI Tunnel Encapsulation
           Attribute . . . . . . . . . . . . . . . . . . . . . . . .   9
     5.3.  Application in BIER . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  10
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     10.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   Multicast traffic is used across operator networks to support
   residential broadband customers, private MPLS customers and used with
   corporate intranet internal customers.  Multicast provides real time
   interactive online meetings or podcasts, IPTV and financial markets
   real-time data, which all have a reliance on UDP's unreliable
   transport.  End to end QOS, therefore, should be a critical component
   of multicast deployment in order to provide a good end user viewing
   experience.  If a packet is dropped, and that packet happens to be a

Song, et al.               Expires 8 July 2022                  [Page 2]
Internet-Draft             Multicast Telemetry              January 2022

   reference frame (I-Frame) in the video feed, the client receiver of
   the multicast feed goes into buffering mode resulting in a frozen
   window.  Multicast packet drops and delay can severely affect the
   application performance and user experience.

   It is important to monitor the performance of the multicast traffic.
   New on-path telemetry techniques such as In-situ OAM
   [I-D.ietf-ippm-ioam-data], Postcard-based Telemetry
   [I-D.song-ippm-postcard-based-telemetry], and Hybrid Two-Step (HTS)
   [I-D.mirsky-ippm-hybrid-two-step] are useful and complementary to the
   existing active OAM performance monitoring methods, provide promising
   means to directly monitor the network experience of multicast
   traffic.  However, multicast traffic has some unique characteristics
   which pose some challenges on efficiently applying such techniques.

   The IP Multicast S,G data is identical from one branch to another on
   it's way to multiple receivers.  When adding iOAM trace data, to
   multicast packets, we enlarge data packets thus consuming more
   network bandwidth.  Instead of adding iOAM trace data, it could be
   more efficient to collect the telemetry information using solutions,
   such as iOAM postcard or HTS, to cut down on the redundant iOAM data.
   The problem is that a postcard type solution doesn't have a branch
   identifier.

   This draft proposes a set of solutions to this iOAM data redundancy
   problem.  The requirements for multicast traffic telemetry are
   discussed along with the issues of the existing on-path telemetry
   techniques.  We propose modifications to make these techniques adapt
   to multicast in order for the original multicast tree to be correctly
   reconstructed while eliminating redundant data.

2.  Requirements for Multicast Traffic Telemetry

   Multicast traffic is forwarded through a multicast tree.  With PIM
   and P2MP (MLDP, RSVP-TE) the forwarding tree is established and
   maintained by the multicast routing protocol.  With BIER, no state is
   created in the network to establish a forwarding tree, instead, a
   bier header provides the necessary information for each packet to
   know the egress points.  Multicast packets are only replicated at
   each tree branch node for efficiency.

   There are several requirements for multicast traffic telemetry, a few
   of which are:

   *  Reconstruct and visualize the multicast tree through data plane
      monitoring.

   *  Gather the multicast packet delay and jitter performance.

Song, et al.               Expires 8 July 2022                  [Page 3]
Internet-Draft             Multicast Telemetry              January 2022

   *  Find the multicast packet drop location and reason.

   *  Gather the VPN state and tunnel information in case of P2MP
      multicast.

   In order to meet these requirements, we need the ability to directly
   monitor the multicast traffic and derive data from the multicast
   packets.  The conventional OAM mechanisms, such as multicast ping and
   trace, may not be sufficient to meet these requirements.

3.  Issues of Existing Techniques

   On-path Telemetry techniques that directly retrieve data from
   multicast traffic's live network experience are ideal to address the
   above mentioned requirements.  The representative techniques include
   In-situ OAM (IOAM) Trace option [I-D.ietf-ippm-ioam-data], IOAM
   Direct Export (DEX) option [I-D.ioamteam-ippm-ioam-direct-export],
   and Postcard-based Telemetry with Packet Marking(PBT-M)
   [I-D.song-ippm-postcard-based-telemetry].  However, unlike unicast,
   multicast poses some unique challenges to applying these techniques.

   Multicast packets are replicated at each branch node in the
   corresponding multicast tree.  Therefore, there are multiple copies
   of packets in the network.

   If the IOAM trace option is used for on-path data collection, the
   partial trace data will also be replicated into multiple copies.  The
   end result is that each copy of the multicast packet has a complete
   trace.  Most of the data, however, is redundant.  Data redundancy
   introduces unnecessary header overhead, wastes network bandwidth, and
   complicates the data processing.  In case the multicast tree is
   large, and the path is long, the redundancy problem becomes severe.

   The PBT solutions, including the IOAM DEX option and PBT-M, can be
   used to eliminate such data redundancy, because each node on the tree
   only sends a postcard covering local data.  However, they cannot
   track the tree branches properly so it can bring confusion about the
   multicast tree topology.  For example, Node A has two branches, one
   to Node B and the other to node D, and Node B leads to Node C and
   Node D leads to Node E.  From the received postcards, one cannot tell
   whether or not Node C(E) is the next hop of Node B(D).

   The fundamental reason for this problem is that there is not an
   identifier (either implicit or explicit) to correlate the data on
   each branch.

Song, et al.               Expires 8 July 2022                  [Page 4]
Internet-Draft             Multicast Telemetry              January 2022

4.  Proposed Modifications to Existing Techniques

   Two solutions are proposed to address the above issues.  One is built
   on PBT and requires augmentation or modification to the instruction
   header of the IOAM Direct Export Option; the other combines the IOAM
   trace option and PBT for an optimized solution.

4.1.  Per-hop postcard using IOAM DEX

   One way to mitigate PBT's multiple tree tracking weakness is to
   augment it with a branch identifier field.  Note that this works for
   the IOAM DEX option but not for PBT-M because the IOAM DEX option
   uses an instruction header.  To make the branch identifier globally
   unique, the branch node ID plus an index is used.  For example, if
   Node A has two branches, one to Node B and one to Node C, Node A will
   use [A, 0] as the branch identifier for the branch to B, and [A, 1]
   for the branch to C.  The identifier is unchanged for each multicast
   tree instance and carried with the multicast packet until the next
   branch node.  Each postcard needs to include the branch identifier in
   the export data.  The branch identifier, along with the other fields
   such as flow ID and sequence number, is sufficient for the data
   analyzer to reconstruct the topology of the multicast tree.

   Figure 1 shows an example of this solution.  "P" stands for the
   postcard packet.  The square brackets contains the branch identifier.
   The curly brace contains the telemetry data about a specific node.

         P:[A,0]{A}  P:[A,0]{B}  P:[B,1]{D} P:[B,0]{C}
              ^            ^          ^        ^
              :            :          :        :
              :            :          :        :
              :            :          :      +-:-+
              :            :          :      |   |
              :            :      +---:----->| C |--...
            +-:-+        +-:-+    |   :      |   |
            |   |        |   |----+   :      +---+
            | A |------->| B |        :
            |   |        |   |--+   +-:-+
            +---+        +---+  |   |   |
                                +-->| D |--....
                                    |   |
                                    +---+

                         Figure 1: Per-hop Postcard

Song, et al.               Expires 8 July 2022                  [Page 5]
Internet-Draft             Multicast Telemetry              January 2022

   Each branch fork node needs to generate the branch ID for each branch
   in its multicast tree instance and include it in the IOAM DEX option
   header so the downstream node can learn it.  The branch ID contains
   two parts: the branch fork node ID and a unique branch index.

   Figure 2 shows that the branch ID is carried as an optional field
   after the flow ID and sequence number optional fields in the IOAM DEX
   option header.  A bit "M" in the Flags field is reserved to indicate
   the presence of the branch index field.  The "M" flag position will
   be determined later after the other flags are specified in
   [I-D.ioamteam-ippm-ioam-direct-export].

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        Namespace-ID           |M|          Flags              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |               IOAM-Trace-Type                 |   Reserved    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Flow ID (optional)                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     Sequence Number  (Optional)               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                  Encoded Branch ID (optional)                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 2: Carry Branch Index in IOAM DEX option header

   To avoid introducing a new type of data field to the IOAM DEX option
   header, we can encode the branch identifier using the existing node
   ID data field as defined in [I-D.ietf-ippm-ioam-data].  Currently,
   the node ID field occupies three octets.  A simple solution is to
   shorten the node ID field so a number of bits can be saved to encode
   the branch index, as shown 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Hop_Lim     |              node_id          |  branch index |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 3: Encode Branch Index with Node ID Method 1

Song, et al.               Expires 8 July 2022                  [Page 6]
Internet-Draft             Multicast Telemetry              January 2022

   Another encoding method is to use the sum of the node ID and the
   branch index as the new node ID, as shown in Figure 4.  As long as
   the node IDs are assigned with large enough gap, the telemetry data
   analyzer can still successfully recover the original node ID and
   branch index.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Hop_Lim     |              node_id + branch index           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 4: Encode Branch Index with Node ID Method 2

   Once a node gets the branch ID information from the upstream, it MUST
   carry this information in its telemetry data export postcards, so the
   original multicast tree can be correctly reconstructed based on the
   postcards.

4.2.  Per-section postcard

   The second solution is a combination of the IOAM trace mode and PBT.
   To avoid data redundancy at each branch node, the trace data
   accumulated, to that point, is exported by a postcard before the
   packet is replicated.  In this case, each branch still needs to
   maintain some identifier to help correlate the postcards for each
   tree section.  The natural way to accomplish this is to simply carry
   the branch node's data (including its ID) in the trace of each
   branch.  This is also necessary because each replicated multicast
   packet can have different telemetry data pertaining to this
   particular copy (e.g., node delay, egress timestamp, and egress
   interface).  As a consequence, the local data exported by each branch
   node can only contain partial data (e.g., ingress interface and
   ingress timestamp).

   Figure 5 shows an example in a segment of a multicast tree.  Node B
   and D are two branch nodes and they will export a postcard covering
   the trace data for the previous section.  The end node of each path
   will also need to export the data of the last section as a postcard.

Song, et al.               Expires 8 July 2022                  [Page 7]
Internet-Draft             Multicast Telemetry              January 2022

                P:{A,B'}            P:{B1,C,D'}
                   ^                     ^
                   :                     :
                   :                     :
                   :                     :    {D1}
                   :                     :    +--...
                   :        +---+      +---+  |
                   :   {B1} |   |{B1,C}|   |--+ {D2}
                   :    +-->| C |----->| D |-----...
       +---+     +---+  |   |   |      |   |--+
       |   | {A} |   |--+   +---+      +---+  |
       | A |---->| B |                        +--...
       |   |     |   |--+   +---+             {D3}
       +---+     +---+  |   |   |{B2,E}
                        +-->| E |--...
                       {B2} |   |
                            +---+

                       Figure 5: Per-section Postcard

   There is no need to modify the IOAM trace mode header format.  We
   just need to configure the branch node to export the postcard and
   refresh the IOAM header and data.

5.  Considerations for Different Multicast Protocols

   MTRACEv2 [RFC8487] provides an active probing approach for the
   tracing of an IP multicast routing path.  Mtrace can also provide
   information such as the packet rates and losses, as well as other
   diagnostic information.  New on-path telemetry techniques will
   enhance Mtrace, and other existing OAM solutions, with more granular
   and realtime network status data through direct measurements.  There
   are various multicast protocols that are used to forward the
   multicast data.  Each will require their own unique on-path telemetry
   solution.

5.1.  Application in PIM

   PIM-SM [RFC7761] is the most widely used multicast routing protocol
   deployed today.  Of the various PIM modes (PIM-SM, PIM-DM, BIDIR-PIM,
   PIM-SSM), PIM-SSM is the preferred method due to its simplicity and
   removal of network source discovery complexity.  With all PIM modes,
   control plane state is established in the network in order to forward
   multicast UDP data packets.  All PIM modes utilize network based
   source discovery except for PIM-SSM, which utilizes application based
   source discovery.  IP Multicast packets fall within the range of
   224.0.0.0 through 239.255.255.255.  The telemetry solution will need

Song, et al.               Expires 8 July 2022                  [Page 8]
Internet-Draft             Multicast Telemetry              January 2022

   to work within this address range and provide telemetry data for this
   UDP traffic.

   The proposed solutions for encapsulating the telemetry instruction
   header and metadata in IPv4/IPv6 UDP packets are described in
   [I-D.herbert-ipv4-udpencap-eh] and
   [I-D.ioametal-ippm-6man-ioam-ipv6-deployment].

5.2.  Application of MVPN X-PMSI Tunnel Encapsulation Attribute

   Multipoint Label Distribution Protocol (mLDP), P2MP RSVP-TE, Ingress
   Replication (IR), PIM MDT SAFI with GRE Transport, are commonly used
   within a Multicast VPN (MVPN) environment utilizing MVPN procedures
   Multicast in MPLS/BGP IP VPNs [RFC6513] and BGP Encoding and
   Procedures for Multicast in MPLS/BGP IP VPNs [RFC6514].  MLDP LDP
   Extension for P2MP and MP2MP LSPs [RFC6388] provides extensions to
   LDP to establish point-to-multipoint (P2MP) and multipoint-to-
   multipoint (MP2MP) label switched paths (LSPs) in MPLS networks.
   P2MP RSVP-TE provides extensions to RSVP-TE RSVP-TE for P2MP LSPs
   [RFC4875] for establish traffic-engineered P2MP LSPs in MPLS
   networks.  Ingress Replication (IR) P2MP Trees Ingress Replication
   Tunnels in Multicast VPNs [RFC7988] using unicast replication from
   parent node to child node over MPLS Unicast Tunnel.  PIM MDT SAFI
   Multicast in BGP/MPLS IP VPNs [RFC6037]utilizes PIM modes PIM-SSM,
   PIM-SM, PIM-BIDIR control plane with GRE transport data plane in the
   core for X-PMSI P-Tree using MVPN procedures.  Replication SID SR
   Replication Segment for Multi-point Service Delivery
   [I-D.ietf-spring-sr-replication-segment] replication segments for
   P2MP multicast service delivery in Segment Routing SR-MPLS networks.
   The telemetry solution will need to be able to follow these P2MP and
   MP2MP paths.  The telemetry instruction header and data should be
   encapsulated into MPLS packets on P2MP and MP2MP paths.  A
   corresponding proposal is described in
   [I-D.song-mpls-extension-header].

5.3.  Application in BIER

   BIER [RFC8279] adds a new header to multicast packets and allows the
   multicast packets to be forwarded according to the header only.  By
   eliminating the requirement of maintaining per multicast group state,
   BIER is more scalable than the traditional multicast solutions.

   OAM Requirements for BIER [I-D.ietf-bier-oam-requirements] lists many
   of the requirements for OAM at the BIER layer which will help in the
   forming of on-path telemetry requirements as well.

Song, et al.               Expires 8 July 2022                  [Page 9]
Internet-Draft             Multicast Telemetry              January 2022

   There is also current work to provide solutions for BIER forwarding
   in ipv6 networks.  For instance, a solution, BIER in Non-MPLS IPv6
   Networks [I-D.xie-bier-ipv6-encapsulation], proposes a new bier
   Option Type codepoint from the "Destination Options and Hop-by-Hop
   Options" IPv6 sub-registry.  This is similar to what IOAM proposes
   for IPv6 transport.

   Depending on how the BIER header is encapsulated into packets with
   different transport protocols, the method to encapsulate the
   telemetry instruction header and metadata also varies.  It is also
   possible to make the instruction header and metadata a part of the
   BIER header itself, such as in a TLV.

6.  Security Considerations

   No new security issues are identified other than those discovered by
   the IOAM, PBT and HTS drafts.

7.  IANA Considerations

   The document makes no request of IANA.

8.  Contributors

   TBD

9.  Acknowledgments

   The authors would like to thank Frank Brockners for the comments and
   advice.

10.  References

10.1.  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>.

   [RFC4687]  Yasukawa, S., Farrel, A., King, D., and T. Nadeau,
              "Operations and Management (OAM) Requirements for Point-
              to-Multipoint MPLS Networks", RFC 4687,
              DOI 10.17487/RFC4687, September 2006,
              <https://www.rfc-editor.org/info/rfc4687>.

Song, et al.               Expires 8 July 2022                 [Page 10]
Internet-Draft             Multicast Telemetry              January 2022

   [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>.

   [RFC6037]  Rosen, E., Ed., Cai, Y., Ed., and IJ. Wijnands, "Cisco
              Systems' Solution for Multicast in BGP/MPLS IP VPNs",
              RFC 6037, DOI 10.17487/RFC6037, October 2010,
              <https://www.rfc-editor.org/info/rfc6037>.

   [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>.

   [RFC6513]  Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
              BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
              2012, <https://www.rfc-editor.org/info/rfc6513>.

   [RFC6514]  Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
              Encodings and Procedures for Multicast in MPLS/BGP IP
              VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
              <https://www.rfc-editor.org/info/rfc6514>.

   [RFC7761]  Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
              Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
              Multicast - Sparse Mode (PIM-SM): Protocol Specification
              (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
              2016, <https://www.rfc-editor.org/info/rfc7761>.

   [RFC7988]  Rosen, E., Ed., Subramanian, K., and Z. Zhang, "Ingress
              Replication Tunnels in Multicast VPN", RFC 7988,
              DOI 10.17487/RFC7988, October 2016,
              <https://www.rfc-editor.org/info/rfc7988>.

   [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>.

Song, et al.               Expires 8 July 2022                 [Page 11]
Internet-Draft             Multicast Telemetry              January 2022

   [RFC8487]  Asaeda, H., Meyer, K., and W. Lee, Ed., "Mtrace Version 2:
              Traceroute Facility for IP Multicast", RFC 8487,
              DOI 10.17487/RFC8487, October 2018,
              <https://www.rfc-editor.org/info/rfc8487>.

10.2.  Informative References

   [I-D.herbert-ipv4-udpencap-eh]
              Herbert, T., "IPv4 Extension Headers and UDP Encapsulated
              Extension Headers", Work in Progress, Internet-Draft,
              draft-herbert-ipv4-udpencap-eh-01, 8 March 2019,
              <https://www.ietf.org/archive/id/draft-herbert-ipv4-
              udpencap-eh-01.txt>.

   [I-D.ietf-bier-oam-requirements]
              Mirsky, G., Kumar, N., Chen, M., and S. Pallagatti,
              "Operations, Administration and Maintenance (OAM)
              Requirements for Bit Index Explicit Replication (BIER)
              Layer", Work in Progress, Internet-Draft, draft-ietf-bier-
              oam-requirements-11, 15 November 2020,
              <https://www.ietf.org/archive/id/draft-ietf-bier-oam-
              requirements-11.txt>.

   [I-D.ietf-ippm-ioam-data]
              Brockners, F., Bhandari, S., and T. Mizrahi, "Data Fields
              for In-situ OAM", Work in Progress, Internet-Draft, draft-
              ietf-ippm-ioam-data-17, 13 December 2021,
              <https://www.ietf.org/archive/id/draft-ietf-ippm-ioam-
              data-17.txt>.

   [I-D.ietf-spring-sr-replication-segment]
              (editor), D. V., Filsfils, C., Parekh, R., Bidgoli, H.,
              and Z. Zhang, "SR Replication Segment for Multi-point
              Service Delivery", Work in Progress, Internet-Draft,
              draft-ietf-spring-sr-replication-segment-06, 25 October
              2021, <https://www.ietf.org/archive/id/draft-ietf-spring-
              sr-replication-segment-06.txt>.

   [I-D.ioametal-ippm-6man-ioam-ipv6-deployment]
              Bhandari, S., Brockners, F., Mizrahi, T., Kfir, A., Gafni,
              B., Spiegel, M., Krishnan, S., and M. Smith, "Deployment
              Considerations for In-situ OAM with IPv6 Options", Work in
              Progress, Internet-Draft, draft-ioametal-ippm-6man-ioam-
              ipv6-deployment-03, 29 March 2020,
              <https://www.ietf.org/archive/id/draft-ioametal-ippm-6man-
              ioam-ipv6-deployment-03.txt>.

Song, et al.               Expires 8 July 2022                 [Page 12]
Internet-Draft             Multicast Telemetry              January 2022

   [I-D.ioamteam-ippm-ioam-direct-export]
              Song, H., Gafni, B., Zhou, T., Li, Z., Brockners, F.,
              Bhandari, S., Sivakolundu, R., and T. Mizrahi, "In-situ
              OAM Direct Exporting", Work in Progress, Internet-Draft,
              draft-ioamteam-ippm-ioam-direct-export-00, 12 October
              2019, <https://www.ietf.org/archive/id/draft-ioamteam-
              ippm-ioam-direct-export-00.txt>.

   [I-D.mirsky-ippm-hybrid-two-step]
              Mirsky, G., Lingqiang, W., Zhui, G., and H. Song, "Hybrid
              Two-Step Performance Measurement Method", Work in
              Progress, Internet-Draft, draft-mirsky-ippm-hybrid-two-
              step-11, 8 July 2021, <https://www.ietf.org/archive/id/
              draft-mirsky-ippm-hybrid-two-step-11.txt>.

   [I-D.song-ippm-postcard-based-telemetry]
              Song, H., Mirsky, G., Filsfils, C., Abdelsalam, A., Zhou,
              T., Li, Z., Shin, J., and K. Lee, "In-Situ OAM Marking-
              based Direct Export", Work in Progress, Internet-Draft,
              draft-song-ippm-postcard-based-telemetry-11, 15 November
              2021, <https://www.ietf.org/archive/id/draft-song-ippm-
              postcard-based-telemetry-11.txt>.

   [I-D.song-mpls-extension-header]
              Song, H., Li, Z., Zhou, T., Andersson, L., and Z. Zhang,
              "MPLS Extension Header", Work in Progress, Internet-Draft,
              draft-song-mpls-extension-header-05, 10 July 2021,
              <https://www.ietf.org/archive/id/draft-song-mpls-
              extension-header-05.txt>.

   [I-D.xie-bier-ipv6-encapsulation]
              Xie, J., Geng, L., McBride, M., Asati, R., Dhanaraj, S.,
              Zhu, Y., Qin, Z., Shin, M., Mishra, G., and X. Geng,
              "Encapsulation for BIER in Non-MPLS IPv6 Networks", Work
              in Progress, Internet-Draft, draft-xie-bier-ipv6-
              encapsulation-10, 22 February 2021,
              <https://www.ietf.org/archive/id/draft-xie-bier-ipv6-
              encapsulation-10.txt>.

Authors' Addresses

   Haoyu Song
   Futurewei Technologies
   2330 Central Expressway
   Santa Clara,
   United States of America

   Email: hsong@futurewei.com

Song, et al.               Expires 8 July 2022                 [Page 13]
Internet-Draft             Multicast Telemetry              January 2022

   Mike McBride
   Futurewei Technologies
   2330 Central Expressway
   Santa Clara,
   United States of America

   Email: mmcbride@futurewei.com

   Greg Mirsky
   ZTE Corp.

   Email: gregimirsky@gmail.com

   Gyan Mishra
   Verizon Inc.

   Email: gyan.s.mishra@verizon.com

   Hitoshi Asaeda
   National Institute of Information and Communications Technology
   4-2-1 Nukui-Kitamachi, Tokyo
   184-8795
   Japan

   Email: asaeda@nict.go.jp

   Tianran Zhou
   Huawei

   Email: zhoutianran@huawei.com

Song, et al.               Expires 8 July 2022                 [Page 14]