OSPF Extensions for BIER
draft-ietf-bier-ospf-bier-extensions-08

OSPF                                                      P. Psenak, Ed.
Internet-Draft                                                  N. Kumar
Intended status: Standards Track                            IJ. Wijnands
Expires: April 6, 2018                                             Cisco
                                                             A. Dolganow
                                                                   Nokia
                                                           T. Przygienda
                                                                J. Zhang
                                                  Juniper Networks, Inc.
                                                               S. Aldrin
                                                            Google, Inc.
                                                         October 3, 2017


                        OSPF Extensions for BIER
              draft-ietf-bier-ospf-bier-extensions-08.txt

Abstract

   Bit Index Explicit Replication (BIER) is an architecture that
   provides multicast forwarding through a "BIER domain" without
   requiring intermediate routers to maintain multicast related per-flow
   state.  Neither does BIER require an explicit tree-building protocol
   for its operation.  A multicast data packet enters a BIER domain at a
   "Bit-Forwarding Ingress Router" (BFIR), and leaves the BIER domain at
   one or more "Bit-Forwarding Egress Routers" (BFERs).  The BFIR router
   adds a BIER header to the packet.  Such header contains a bit-string
   in which each bit represents exactly one BFER to forward the packet
   to.  The set of BFERs to which the multicast packet needs to be
   forwarded is expressed by the according set of bits set in BIER
   packet header.

   This document describes the OSPF protocol extension required for BIER
   with MPLS encapsulation.

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
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   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




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   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 April 6, 2018.

Copyright Notice

   Copyright (c) 2017 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 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.  Flooding of the BIER Information in OSPF  . . . . . . . . . .   3
     2.1.  BIER Sub-TLV  . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  BIER MPLS Encapsulation Sub-TLV . . . . . . . . . . . . .   4
     2.3.  Optional BIER Tree Type Sub-TLV . . . . . . . . . . . . .   5
     2.4.  Optional BIER sub-domain BSL conversion Sub-TLV . . . . .   6
     2.5.  Flooding scope of BIER Information  . . . . . . . . . . .   7
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
     4.1.  BIER Tree Type Registry . . . . . . . . . . . . . . . . .   8
   5.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Bit Index Explicit Replication (BIER) is an architecture that
   provides optimal multicast forwarding through a "BIER domain" without
   requiring intermediate routers to maintain any multicast related per-
   flow state.  Neither does BIER explicitly require a tree-building
   protocol for its operation.  A multicast data packet enters a BIER
   domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the
   BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs).
   The BFIR router adds a BIER header to the packet.  The BIER header
   contains a bit-string in which each bit represents exactly one BFER
   to forward the packet to.  The set of BFERs to which the multicast



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   packet needs to be forwarded is expressed by setting the bits that
   correspond to those routers in the BIER header.

   BIER architecture requires routers participating in BIER to exchange
   BIER related information within a given domain.  BIER architecture
   permits link-state routing protocols to perform distribution of such
   information.  This document describes extensions to OSPF necessary to
   advertise BIER specific information in the case where BIER uses MPLS
   encapsulation as described in [I-D.ietf-bier-mpls-encapsulation].

   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].

2.  Flooding of the BIER Information in OSPF

   All BIER specific information that a Bit-Forwarding Router (BFR)
   needs to advertise to other BFRs is associated with a BFR-Prefix.  A
   BFR prefix is a unique (within a given BIER domain) routable IP
   address that is assigned to each BFR as described in more detail in
   section 2 of [I-D.ietf-bier-architecture].

   Given that BIER information must be associated with a BFR prefix, the
   OSPF Extended Prefix Opaque LSA [RFC7684] has been chosen for
   advertisement.

2.1.  BIER Sub-TLV

   A Sub-TLV of the Extended Prefix TLV (defined in [RFC7684]) is
   defined for distributing BIER information.  The Sub-TLV is called the
   BIER Sub-TLV.  Multiple BIER Sub-TLVs may be included in the Extended
   Prefix TLV.

   The BIER Sub-TLV has the following format:

   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             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Sub-domain-ID |     MT-ID     |              BFR-id           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Sub-TLVs (variable)                      |
   +-                                                             -+
   |                                                               |


      Type: TBD1



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      Length: Variable, dependent on sub-TLVs.

      Sub-domain-ID: Unique value identifying the BIER sub-domain within
      the BIER domain, as described in section 1 of
      [I-D.ietf-bier-architecture].

      MT-ID: Multi-Topology ID (as defined in [RFC4915]) that identifies
      the topology that is associated with the BIER sub-domain.

      BFR-id: A 2 octet field encoding the BFR-id, as documented in
      section 2 of [I-D.ietf-bier-architecture].  If the BFR is not
      locally configured with a valid BFR-id, the value of this field is
      set to invalid BFR-id per [I-D.ietf-bier-architecture].

   Each BFR sub-domain MUST be associated with one and only one OSPF
   topology that is identified by the MT-ID.  If the association between
   BIER sub-domain and OSPF topology advertised in the BIER sub-TLV by
   other BFRs is in conflict with the association locally configured on
   the receiving router, the BIER Sub-TLV MUST be ignored.

   If a BFR advertises the same Sub-domain-ID in multiple BIER sub-TLVs,
   the BRF MUST be treated as if it did not advertise a BIER sub-TLV for
   such sub-domain.

   All BFRs MUST detect advertisement of duplicate valid BFR-IDs for a
   given MT-ID and Sub-domain-ID.  When such duplication is detected all
   BFRs advertising duplicates MUST be treated as if they did not
   advertise a valid BFR-id.

2.2.  BIER MPLS Encapsulation Sub-TLV

   The BIER MPLS Encapsulation Sub-TLV is a Sub-TLV of the BIER Sub-TLV.
   The BIER MPLS Encapsulation Sub-TLV is used in order to advertise
   MPLS specific information used for BIER.  It MAY appear multiple
   times in the BIER Sub-TLV.

   The BIER MPLS Encapsulation Sub-TLV has the following format:

   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             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Lbl Range Size |                Label Range Base               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |BS Len |                     Reserved                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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      Type: TBD2

      Length: 4 octets

      Label Range Size: A 1 octet field encoding the label range size of
      the label range.  It MUST be greater then 0, otherwise the
      advertising router MUST be treated as if it did not advertise a
      BIER sub-TLV.

      Label Range Base: A 3 octet field, where the 20 rightmost bits
      represent the first label in the label range.  The 4 leftmost bits
      MUST be ignored.

      Bit String Length: A 4 bits field encoding the supported BitString
      length associated with this BFR-prefix.  The values allowed in
      this field are specified in section 2 of
      [I-D.ietf-bier-mpls-encapsulation].

      The "label range" is the set of labels beginning with the label
      range base and ending with ((label range base)+(label range size)-
      1).  A unique label range is allocated for each BitStream length
      and Sub-domain-ID.  These labels are used for BIER forwarding as
      described in [I-D.ietf-bier-architecture] and
      [I-D.ietf-bier-mpls-encapsulation].

      The size of the label range is determined by the number of Set
      Identifiers (SI) (section 1 of [I-D.ietf-bier-architecture]) that
      are used in the network.  Each SI maps to a single label in the
      label range.  The first label is for SI=0, the second label is for
      SI=1, etc.

   If same BS length is repeated in multiple BIER MPLS Encapsulation
   Sub-TLV inside the same BIER Sub-TLV, the BIER sub-TLV MUST be
   ignored.

   Label ranges within all BIER MPLS Encapsulation Sub-TLV inside the
   same BIER Sub-TLV MUST NOT overlap.  If the overlap is detected, the
   advertising router MUST be treated as if it did not advertise a BIER
   sub-TLV.

   All advertised labels MUST be valid, otherwise the BIER sub-TLV MUST
   be ignored.

2.3.  Optional BIER Tree Type Sub-TLV

   The BIER Tree Type Sub-TLV is a Sub-TLV of the BIER Sub-TLV.  This
   Sub-TLV carries the information associated with the supported BIER
   tree type for a sub-domain.  This Sub-TLV is optional and its absence



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   has the same semantics as its presence with Tree Type value 0 (SPF).
   When Tree Type 0 is used, it is RECOMMENDED that this Sub-TLV is
   omitted in order to reduce the space consumed in the parent TLV.

   This Sub-TLV MAY occur no more than once in a BIER sub-TLV.  If
   multiple occurences of this Sub-TLV are present in a single BIER Sub-
   TLV, the BIER sub-TLV MUST be ignored.

   If the tree type (implied or explicitly advertised) does not match
   the locally configured tree type associated with the matching sub-
   domain, the BIER sub-TLV MUST be ignored.

     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             |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Tree Type     |
    +-+-+-+-+-+-+-+-+

      Type: TBD3.

      Length: 1 octet.

      Tree Type: 1 octet field describing the Tree Type.  The following
      value is defined by this document:

         0: Shortest Path First (SPF) algorithm based on IGP link
         metric.  This is the standard shortest path algorithm as
         computed by the OSPF protocol.

2.4.  Optional BIER sub-domain BSL conversion Sub-TLV

   The BIER sub-domain BSL conversion Sub-TLV is a Sub-TLV of the BIER
   Sub-TLV.  This sub-TLV indicates whether the BFR is capable of
   imposing a different Bit String Length (BSL) than the one it received
   in a BIER encapsulated packet.  Such a capability may allow future,
   advanced tree types which ensure simple migration procedures from one
   BSL to another in a given MT-ID and Sub-domain-ID or prevent stable
   blackholes in scenarios where not all routers support the same set of
   BSLs in a given MT-ID and Sub-domain-ID.

   The BIER sub-domain BSL conversion Sub-TLV is optional and its
   absence indicates that the router is NOT capable of imposing
   different BSLs but will always forward the packet with the BSL
   unchanged.  This sub-TLV MAY occur at most once in a given BIER sub-
   TLV.  If multiple occurrences of this sub-TLV are received in a given
   BIER sub-TLV, the BIER sub-TLV MUST be ignored.



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   The BIER sub-domain BSL conversion Sub-TLV has following format:

     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             |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      Type: TBD4.

      Length: 0 octets.

2.5.  Flooding scope of BIER Information

   The flooding scope of the OSPF Extended Prefix Opaque LSA [RFC7684]
   that is used for advertising the BIER Sub-TLV is set to area-local.
   To allow BIER deployment in a multi-area environment, OSPF must
   propagate BIER information between areas.


                 (  )         (  )         (  )
               (      )     (      )     (      )
            R1  Area 1   R2  Area 0   R3  Area 2  R4
               (      )     (      )     (      )
                 (  )         (  )         (  )

               Figure 1: BIER propagation between areas


   The following procedure is used in order to propagate BIER related
   information between areas:

      When an OSPF Area Border Router (ABR) advertises a Type-3 Summary
      LSA from an intra-area or inter-area prefix to all its attached
      areas, it will also originate an Extended Prefix Opaque LSA, as
      described in [RFC7684].  The flooding scope of the Extended Prefix
      Opaque LSA type will be set to area-local.  The route-type in the
      OSPF Extended Prefix TLV is set to inter-area.  When determining
      whether a BIER Sub-TLV should be included in this LSA, an OSPF ABR
      will:

         - Examine its best path to the prefix in the source area and
         find the advertising router associated with the best path to
         that prefix.

         - Determine if such advertising router advertised a BIER Sub-
         TLV for the prefix.  If yes, the ABR will copy the information



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         from such BIER Sub-TLV when advertising BIER Sub-TLV to each
         attached area.

      In the Figure 1, R1 advertises a prefix 192.0.0.1/32 in Area 1.
      It also advertises Extended Prefix Opaque LSA for prefix
      192.0.0.1/32 and includes BIER Sub-TLV in it.  Area Border Router
      (ABR) R2 calculates the reachability for prefix 192.0.0.1/32
      inside Area 1 and propagates it to Area 0.  When doing so, it
      copies the entire BIER Sub-TLV (including all its Sub-TLVs) it
      received from R1 in Area 1 and includes it in the Extended Prefix
      Opaque LSA it generates for 192.0.0.1/32 in Area 0.  ABR R3
      calculates the reachability for prefix 192.0.0.1/32 inside Area 0
      and propagates it to Area 2.  When doing so, it copies the entire
      BIER Sub-TLV (including all its Sub-TLVs) it received from R2 in
      Area 0 and includes it in the Extended Prefix Opaque LSA it
      generates for 192.0.0.1/32 in Area 2.

3.  Security Considerations

   Implementations must assure that malformed TLV and Sub-TLV
   permutations do not result in errors which cause hard OSPF failures.

4.  IANA Considerations

   The document requests three new allocations from the OSPF Extended
   Prefix sub-TLV registry as defined in [RFC7684].

      BIER Sub-TLV: TBD1

      BIER MPLS Encapsulation Sub-TLV: TBD2

      BIER Tree Type Sub-TLV: TBD3

      BIER sub-domain BSL conversion Sub-TLV

4.1.  BIER Tree Type Registry

   IANA is requested to set up a registry called "BIER Tree Type".  The
   registration policy for this registry is "Standards Action"
   ([RFC8126] and [RFC7120]).

   Values in this registry must come from the range 0-255.

   The initial value in the BIER Tree Type registry is:

      0: Shortest Path First (SPF) algorithm based on standard IGP link
      metric.




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5.  Acknowledgments

   The authors would like to thank Rajiv Asati, Christian Martin, Greg
   Shepherd and Eric Rosen for their contribution.

6.  Normative References

   [I-D.ietf-bier-architecture]
              Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
              S. Aldrin, "Multicast using Bit Index Explicit
              Replication", draft-ietf-bier-architecture-06 (work in
              progress), April 2017.

   [I-D.ietf-bier-mpls-encapsulation]
              Wijnands, I., Rosen, E., Dolganow, A., Tantsura, J.,
              Aldrin, S., and I. Meilik, "Encapsulation for Bit Index
              Explicit Replication in MPLS and non-MPLS Networks",
              draft-ietf-bier-mpls-encapsulation-07 (work in progress),
              June 2017.

   [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>.

   [RFC4915]  Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
              Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
              RFC 4915, DOI 10.17487/RFC4915, June 2007,
              <https://www.rfc-editor.org/info/rfc4915>.

   [RFC7120]  Cotton, M., "Early IANA Allocation of Standards Track Code
              Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January
              2014, <https://www.rfc-editor.org/info/rfc7120>.

   [RFC7684]  Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
              Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
              Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
              2015, <https://www.rfc-editor.org/info/rfc7684>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.








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Authors' Addresses

   Peter Psenak (editor)
   Cisco
   Apollo Business Center
   Mlynske nivy 43
   Bratislava  821 09
   Slovakia

   Email: ppsenak@cisco.com


   Nagendra Kumar
   Cisco
   7200 Kit Creek Road
   Research Triangle Park, NC  27709
   US

   Email: naikumar@cisco.com


   IJsbrand Wijnands
   Cisco
   De Kleetlaan 6a
   Diegem  1831
   Belgium

   Email: ice@cisco.com


   Andrew Dolganow
   Nokia
   750 Chai Chee Rd
   06-06 Viva Business Park
   Singapore  469004

   Email: andrew.dolganow@alcatel-lucent.com


   Tony Przygienda
   Juniper Networks, Inc.
   10 Technology Park Drive
   Westford, MA  01886
   USA

   Email: prz@juniper.net





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   Jeffrey Zhang
   Juniper Networks, Inc.
   10 Technology Park Drive
   Westford, MA  01886
   USA

   Email: zzhang@juniper.net


   Sam Aldrin
   Google, Inc.
   1600 Amphitheatre Parkway
   Mountain View, CA
   USA

   Email: aldrin.ietf@gmail.com



































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