M-LDP Signaling Through BIER Core
draft-ietf-bier-mldp-signaling-over-bier-03

Network Working Group                                    H. Bidgoli, Ed.
Internet-Draft                                               J. Kotalwar
Intended status: Standards Track                                   Nokia
Expires: 23 April 2024                                       I. Wijnands
                                                               M. Mishra
                                                            Cisco System
                                                                Z. Zhang
                                                        Juniper Networks
                                                               E. Leyton
                                                                 Verizon
                                                         21 October 2023

                   M-LDP Signaling Through BIER Core
              draft-ietf-bier-mldp-signaling-over-bier-03

Abstract

   Consider an end-to-end Multipoint LDP (mLDP) network, where it is
   desirable to deploy BIER in a segment of this network.  It might be
   desirable to deploy BIER with minimal disruption to the mLDP network
   or a redesign of the network.

   This document describes a procedure needed for mLDP tunnels to be
   signaled over and stitched through a BIER core, allowing LDP routers
   to run traditional mLDP services through a BIER core.

Status of This Memo

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   This Internet-Draft will expire on 23 April 2024.

Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   2
     2.1.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  mLDP Signaling Through BIER domain  . . . . . . . . . . . . .   4
     3.1.  Ingress BBR procedure . . . . . . . . . . . . . . . . . .   5
       3.1.1.  Automatic tLDP session Creation . . . . . . . . . . .   5
       3.1.2.  ECMP Method on IBBR . . . . . . . . . . . . . . . . .   5
     3.2.  Egress BBR procedure  . . . . . . . . . . . . . . . . . .   5
       3.2.1.  IBBR procedure for arriving upstream assigned
               label . . . . . . . . . . . . . . . . . . . . . . . .   6
       3.2.2.  BIER Interface ID SUB-TLVs  . . . . . . . . . . . . .   6
   4.  Datapath Forwarding . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Datapath traffic flow . . . . . . . . . . . . . . . . . .   7
   5.  Recursive FEC . . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Consideration  . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Some operators that are using mLDP P2MP LSPs for their multicast
   transport would like to deploy BIER technology in some segments of
   their network.  This draft explains a method to signal mLDP services
   through a BIER domain, with minimal disruption and operational impact
   to the mLDP domain.

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

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2.1.  Definitions

   Some of the terminology specified in [RFC8279]is replicated here and
   extended by necessary definitions:

   BIER:

   Bit Index Explicit Replication, The overall architecture of
   forwarding multicast using a Bit Position.

   BFR:

   Bit Forwarding Router, A router that participates in Bit Index
   Multipoint Forwarding.  A BFR is identified by a unique BFR prefix in
   a BIER domain.

   BFIR:

   Bit-Forwarding Ingress Router, The ingress border router that inserts
   the Bit Map into the packet.  Each BFIR must have a valid BFR-id
   assigned.  BFIR is a term used for data plane packet forwarding.

   BFER:

   Bit-Forwarding Egress Router, A router that participates in Bit Index
   Forwarding as leaf.  Each BFER must have a valid BFR-id assigned.
   BFER is a term used for data plane packet forwarding.

   BBR:

   BIER Boundary router.  The router between the LDP domain and BIER
   domain.

   IBBR:

   Ingress BIER Boundary Router.  The ingress router from a signaling
   point of view.  It maintains mLDP adjacency toward the LDP domain and
   determines if the Multipoint LDP FEC needs to be signaled across the
   BIER domain via Targeted LDP.

   EBBR:

   Egress BIER Boundary Router.  The egress router in a BIER domain from
   signaling point of view.  It terminates the targeted LDP signaling
   through the BIER domain.  It also keeps track of all IBBRs that are
   part of this P2MP tree

   BIFT:

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   Bit Index Forwarding Table.

   BIER sub-domain:

   A further distinction within a BIER domain identified by its unique
   sub-domain identifier.  A BIER sub-domain can support multiple
   BitString Lengths.

   BFR-id:

   An optional, unique identifier for a BFR within a BIER sub-domain,
   all BFERs and BFIRs need to be assigned a BFR-id.

   ILM:

   MPLS Incoming Label Map.

3.  mLDP Signaling Through BIER domain

                        BBR                   BBR
         |---LDP Domain--|-----BIER domain-----|---LDP domain--|
    S--( A )-----------( B ) ---- ( C ) ---- ( D )-----------( E )--h

                       EBBR                  IBBR
    Sig  <----MLDP------|<----targeted LDP----|<---MLDP------
    (new)

                      BFIR                  BFER
         ------------->|--------BIER-------->|------------->  Datapatah
                                                               (new)

                       Figure 1: BIER boundary router

   As per figure 1, point-to-multipoint and multipoint-to-multipoint
   LSPs established via mLDP [RFC6388] can be signaled through a bier
   domain via Targeted LDP sessions.  This procedure is explained in
   [RFC7060] (Using LDP Multipoint Extension on Targeted LDP Sessions).

   This document provides details and defines some needed procedures.

   .

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3.1.  Ingress BBR procedure

   In Figure 1, the Ingress BBR (IBBR) is connected to the mLDP domain
   on downstream and a BIER domain on the upstream.  To connect the LDP
   domains via BIER domain, IBBR needs to establish a targeted LDP
   session with EBBR closest to the root of the P2MP or MP2MP LSP.  To
   do so IBBR will follow procedures in [RFC7060] in particular section
   6 "Targeted mLDP with Multicast Tunneling".

   The Target LDP session can be established manually via configuration
   or via automated mechanism.

3.1.1.  Automatic tLDP session Creation

   tLDP sessions can be signaled automatically from every IBBR to the
   appropriate EBBR.  When mLDP FEC arrives at the IBBR from LDP domain,
   IBBR can automatically start a tLDP session to the EBBR closest to
   the root node.  Both IBBR and EBBR should be in auto-discovery mode
   and react to the arriving tLDP signaling packets (i.e. targeted
   hellos, keep-alives etc...) to establish the session automatically.

   The root node address in the mLDP FEC can be used to find the EBBR.
   To identify the EBBR, the same procedures as [RFC7060] section 2.1
   can be used or the procedures as explained in the
   [draft-ietf-bier-pim-signaling] appendix A.

3.1.2.  ECMP Method on IBBR

   If the IBBR finds multiple equal cost EBBRs on the path to the root,
   it can use a vendor specific algorithm to choose between the EBBRs.
   These algorithms are beyond the scope of this draft.  As an example
   the IBBR can use the lowest EBBR IP address to establish its mLDP
   signaling to.

3.2.  Egress BBR procedure

   The Egress BBR (EBBR) is connected to the upstream mLDP domain.  The
   EBBR should accept the tLDP session generated form the IBBR.  It
   should assign a unique "upstream assigned label" for each arriving
   FEC generated by the IBBRs.

   The EBBR should follow the [RFC7060] procedures with the following
   modifications:

   *  The label assigned by the EBBR cannot be Implicit Null.  This is
      to ensure that the identity of each p2mp and/or mp2mp tunnel in
      the BIER domain is uniquely distinguished.

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   *  The label can be assigned from a domain-wide Common Block (DCB)
      [draft-ietf-bess-mvpn-evpn-aggregation-label]

   *  The Interface ID TLV, as per [RFC6389] should includes a new BIER
      sub-tlv as tunnel identifier.

   The EBBR will also generate a new label and FEC toward the root in
   the LDP domain.  The EBBR Should stitch this generated label with the
   "upstream assigned label" to complete the P2MP or MP2MP LSP.

   With the same token the EBBR should track all the arriving FECs and
   the IBBRs that are generating these FECs.  The EBBR will use this
   information to build the bier header for each set of common FEC
   arriving from the IBBRs.

3.2.1.  IBBR procedure for arriving upstream assigned label

   Upon receiving the "upstream assigned label", the IBBR should create
   its own stitching instruction between the "upstream assigned label"
   and the downstream signaled label.

3.2.2.  BIER Interface ID SUB-TLVs

   As per [RFC6389] when LDP is used for upstream label assignment,the
   Interface ID TLV is used for signaling the Tunnel Identifier and it
   carries sub-TLVs.  This document defines two new Interface ID sub-
   TLVs for BIER.

   Below is the Interface ID BIER sub-TLV for IPv4 BIER prefix:

        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 (TBD1)                |               15              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      IBBR Prefix IPv4                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  sub-domain-id|      BFR-id                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Below is the Interface ID BIER sub-TLV for IPv6 BIER prefix:

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        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)                |               23              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      IBBR Prefix IPv6                         |
       ~                         ........                              ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  sub-domain-id|      BFR-id                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4.  Datapath Forwarding

4.1.  Datapath traffic flow

   On the BFIR when the MPLS label for P2MP/MP2MP LSP arrives from
   upstream, a lookup in the ILM table is done and the label is swapped
   with the tLDP upstream assigned label.  The BFIR will note all the
   BFERs that are interested in specific P2MP/MP2MP LSP (as per section
   3.2).  The BFIR will put the corresponding BIER header with the bit
   index set for all the IBBRs interested in this stream.  The BFIR will
   set the BIERHeader.Proto = MPLS and will forward the BIER packet into
   the BIER domain.

   In the BIER domain, normal BIER forwarding procedure will be done, as
   per [RFC8279]

   The BFERs will receive the BIER packet and will look at the protocol
   field of BIER header, indicating MPLS protocol.  The BFER will remove
   the BIER header and will do a lookup in the ILM table for the
   upstream assigned label and perform its corresponding action.

   It should be noted that these procedures are also valid if BFIR is
   the ILER and/or BFER is the ELER as per [RFC7060]

5.  Recursive FEC

   The procedures above are also valid for mLDP recursive FEC.  The root
   used to determine the EBBR is the outer root of the FEC.  The entire
   recursive FEC needs to be preserved when it is forwarded via tLDP and
   the label request.

6.  IANA Consideration

   IANA maintains a registry of Interface ID Types for use in GMPLS in
   the registry "Generalized Multi-Protocol Label Switching (GMPLS)
   Signaling Parameters" and sub-registry "Interface_ID Types"

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   This document defines and requests two new Interface_ID Type for BIER
   from the Interface_ID Types space,

   *  BIER IPv4 prefix TLV (Value TBD)

   *  BIER IPv6 prefix TLV (Value TBD)

7.  Security Considerations

   While in the BIER domain the security considerations of [RFC8279] are
   relevant to this document.

   The implementation should also take into account the security
   recommendations of [RFC6389].

8.  Acknowledgments

   Authors would like to acknowledge Jingrong Xie and Nabeel Cocker for
   his comments and help on this draft.

9.  References

9.1.  Normative References

   [draft-ietf-bess-mvpn-evpn-aggregation-label]
              "Z. Zhang, E. Rosen, W. Lin, Z. Li, I. Wijnands, "MVPN/
              EVPN Tunnel Aggregation with Common Labels"", 27 April
              2018.

   [draft-ietf-bier-pim-signaling]
              "H, Bidgoli, F. Xu, J. Kotalwar, I. Wijnands, M. Mishra,
              Z.  Zhang", 29 July 2020.

   [RFC2119]  "S. Bradner, "Key words for use in RFCs to Indicate
              Requirement Levels"", March 1997.

   [RFC6388]  "IJ. Wijnands, I. Minei, K. Kompella, B.Thomas "Label
              Distribution Protocol Extensions for Point-to-Multipoint
              and Multipoint-to-Multipoint LSP"".

   [RFC6389]  "R Aggarwal, JL. Le Roux, "MPLS Upstream Label Assignment
              for LDP"", November 2011.

   [RFC7060]  "M. Napierala, E. Rosen, I. Wijnands", November 2013.

   [RFC8279]  "I. Wijnands, E. Rosen, A. ADolganow, T. Prygienda, S.
              Aldrin", November 2017.

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9.2.  Informative References

   [RFC8401]  "Ginsberg, L., Przygienda, T., Aldrin, S., and Z. Zhang,
              "BIER Support via ISIS"", June 2018.

   [RFC8444]  "Psenak, P., Kumar, N., Wijnands, IJ., Dolganow, A.,
              Przygienda, T., Zhang, Z., and S. Aldrin, "OSPF Extensions
              for Bit Index Explicit Replication"", June 2018.

   [RFC8556]  "Rosen, E., Ed., Sivakumar, M., Wijnands, IJ., Aldrin,
              S.,Dolganow, A., and T. Przygienda, "Multicast VPN Using
              Index Explicit Replication (BIER)", April 2018.

Authors' Addresses

   Hooman Bidgoli (editor)
   Nokia
   Ottawa
   Canada
   Email: hooman.bidgoli@nokia.com

   Jayant Kotalwar
   Nokia
   Montain View,
   United States of America
   Email: jayant.kotalwar@nokia.com

   IJsbrand Wijnands
   Cisco System
   Diegem
   Belgium
   Email: ice@cisco.com

   Mankamana Mishra
   Cisco System
   Milpitas,
   United States of America
   Email: mankamis@cisco.com

   Zhaohui Zhang
   Juniper Networks
   Boston,
   United States of America
   Email: zzhang@juniper.com

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   Eddie Leyton
   Verizon
   Email: Edward.leyton@verizonwireless.com

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