M-LDP Signaling Through BIER Core
draft-ietf-bier-mldp-signaling-over-bier-00

Document Type Active Internet-Draft (bier WG)
Authors Hooman Bidgoli  , Jayant Kotalwar  , IJsbrand Wijnands  , Mankamana Mishra  , Zhaohui Zhang  , Eddie Leyton 
Last updated 2020-11-10
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Network Working Group                                    H. Bidgoli, Ed.
Internet-Draft                                               J. Kotalwar
Intended status: Informational                                     Nokia
Expires: May 5, 2021                                         I. Wijnands
                                                               M. Mishra
                                                            Cisco System
                                                                Z. Zhang
                                                        Juniper Networks
                                                               E. Leyton
                                                                 Verizon
                                                       November 01, 2020

                   M-LDP Signaling Through BIER Core
              draft-ietf-bier-mldp-signaling-over-bier-00

Abstract

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

   This document describes the 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

   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 May 5, 2021.

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Copyright Notice

   Copyright (c) 2020 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
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   (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
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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 . . . . . . . . . . . . . . . . . .   4
       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
   4.  Datapath Forwarding . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Datapath traffic flow . . . . . . . . . . . . . . . . . .   6
   5.  Recursive FEC . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Consideration  . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   7
   9.  Informative References  . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Some operators that are using mLDP P2MP LSPs for their multicast
   transport would like to deploy BIER technology in some segment 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 RFC 2119 [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 term used for dataplain packet forwarding.

   BFER:

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

   BBR:

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

   IBBR:

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

   EBBR:

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

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   BIFT:

   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.

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 boundry router

   As per figure 1, point-to-multipoint (P2MP) and multipoint-to-
   multipoint (MP2MP) 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 documents provides details and defines some needed procedures.

   .

3.1.  Ingress BBR procedure

   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

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   follow procedures in [RFC7060] in particular the 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 session can be signaled automatically from every IBBR to the
   appropriate EBBR.  When mLDP FEC arrives to 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 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 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 smallest 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 IBBR.  It should
   assign a unique "upstream assigned label" for each arriving FEC
   generated by IBBRs.

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

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

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

   o  The Interface ID TLV, as per [RFC6389] should includes a new BIER
      sub-domain sub- tlv (type TBD)

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

   With same token the EBBR should track all the arriving FECs and the
   IBBRs that are generating these FECs.  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", IBBR should create its
   own stitching instruction between the "upstream assigned label" and
   the down stream signaled label.

4.  Datapath Forwarding

4.1.  Datapath traffic flow

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

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

   The BFERs will receive the BIER packet, will look at the protocol of
   BIER header (MPLS).  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 above procedures also will work with a recursive FEC [RFC6512].
   The root used to determine the EBBR is the outer FECs root.  The
   entire recursive FEC needs to be preserve when it is forwarded via
   tLDP and the label request.

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6.  IANA Consideration

   1.  A new BIER sub-domain sub- tlv for the interface ID TLV to be
       assigned by IANA

7.  Security Considerations

   TBD

8.  Acknowledgments

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

9.  Informative 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"", February 2012.

   [draft-ietf-bier-pim-signaling]
              "H.Bidgoli, F. Xu, J. Kotalwar, IJ. Wijnands, M. Mishra,
              Z.  Zhang "PIM Signaling Through BIER Core"", February
              2012.

   [RFC6388]  "IJ. Wijnands, I. Minei, K. Kompella, B. Thomas "LDP
              Extensions for P2MP and MP2MP"", Novermber 2011.

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

   [RFC6512]  "IJ. Wijnands, E. Rosen, M. Napierala, N. Leymann "Using
              Multipoint LDP when the backbone has No route to the
              root"", February 2012.

   [RFC7060]  "M. Napierala, E. Rosen, IJ. Winjnands "Using LDP
              Multipoint Extensions on Targeted LDP Sessions"", November
              2013.

   [RFC8279]  "IJ. Wijnands, E. Rosen, A. Dolganow, T. Przygienda, S.
              Aldrin "Multicast using BIER"", April 2018.

Authors' Addresses

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   Hooman Bidgoli (editor)
   Nokia
   Ottawa
   Canada

   Email: hooman.bidgoli@nokia.com

   Jayant Kotalwar
   Nokia
   Montain View
   US

   Email: jayant.kotalwar@nokia.com

   IJsbrand Wijnands
   Cisco System
   Diegem
   Belgium

   Email: ice@cisco.com

   Mankamana Mishra
   Cisco System
   Milpitas
   USA

   Email: mankamis@cisco.com

   Zhaohui Zhang
   Juniper Networks
   Boston
   USA

   Email: zzhang@juniper.com

   Eddie Leyton
   Verizon

   Email: Edward.leyton@verizonwireless.com

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