BIER support via ISIS
draft-przygienda-bier-isis-ranges-02

Internet Engineering Task Force                            A. Przygienda
Internet-Draft                                                  Ericsson
Intended status: Standards Track                             L. Ginsberg
Expires: April 26, 2015                                    Cisco Systems
                                                               S. Aldrin
                                                                  Huawei
                                                                J. Zhang
                                                  Juniper Networks, Inc.
                                                        October 23, 2014


                         BIER support via ISIS
                  draft-przygienda-bier-isis-ranges-01

Abstract

   Specification of an ISIS extension to support BIER domains.

Requirements Language

   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] .

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 http://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 April 26, 2015.

Copyright Notice

   Copyright (c) 2014 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



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   (http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   4.  Concepts  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  BIER Domains in Extended Reachability TLVs  . . . . . . .   4
     4.2.  BIER Domains  . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Enabling a BIER Domain  . . . . . . . . . . . . . . . . .   4
     5.2.  Encapsulation . . . . . . . . . . . . . . . . . . . . . .   5
     5.3.  Label Advertisements for MPLS encapsulated BIER domains .   5
       5.3.1.  Special Consideration . . . . . . . . . . . . . . . .   5
     5.4.  BFR-id Advertisements . . . . . . . . . . . . . . . . . .   5
     5.5.  Flooding  . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Packet Formats  . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  BIER Info sub-TLV . . . . . . . . . . . . . . . . . . . .   6
     6.2.  BIER MPLS Encapsulation sub-sub-TLV . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Bit Index Explicit Replication (BIER)
   [I-D.draft-wijnands-bier-architecture-00] defines an architecture
   where all intended multicast receivers are encoded as bitmask in the
   Multicast packet header within different encapsulations such as
   [I-D.draft-wijnands-mpls-bier-encapsulation-01].  A router that
   receives such a packet will forward the packet based on the Bit
   Position in the packet header towards the receiver(s), following a
   precomputed tree for each of the bits in the packet.  Each receiver
   is represented by a unique bit in the bitmask.

   This document presents first attempt at necessary extensions to the
   currently deployed ISIS for IP [RFC1195] protocol to support
   distribution of information necessary for operation of BIER domains.
   This document defines a new TLV to be advertised by every router
   participating in such BIER domains.



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2.  Terminology

   Some of the terminology specified in
   [I-D.draft-wijnands-bier-architecture-00] is replicated here and
   extended by necessary definitions:

   BIER:  Bit Index Explicit Replication (The overall architecture of
      forwarding multicast using a Bit Position).

   BIER-OL:  BIER Overlay Signaling.  (The method for the BFIR to learn
      about BFER's).

   BM:  Bit Mask (A bit stream of a certain fixed length.  Each Bit
      represents a receiver).

   P-BM:  Packet Bit Mask (A Bit Mask included in the Multicast Packet).

   BP:  Bit Position (A single Bit from the Bit Mask that represents a
      receiver).

   BFR:  Bit Forwarding Router (A router that participates in Bit Index
      Multipoint Forwarding).

   BFIR:  Bit Forwarding Ingress Router (The ingress border router that
      inserts the BM into the packet).

   BFER:  Bit Forwarding Egress Router.  A router that participates in
      Bit Index Forwarding as leaf.  Each BFER must be a BFR.

   BFT:  Bit Forwarding Tree used to reach all BFERs in a domain.

   BIFT:  Bit Index Forwarding Table (A Bit index forwarding table).

   BMS:  Bit Mask Set. Set containing bit positions of all BFER
      participating in a set.

   BMP:  Bit Mask Position, a given bit in a BMS.

   Invalid BMP:  Unassigned Bit Mask Position, consisting of all 0s.

   Invalid BFR-id:  Unassigned BFR-id, consisting of all 0s.

   IGP signalled BIER domain:  A BIER domain information carried in IGP
      and identified by its multi-topology and bitmask length.







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3.  IANA Considerations

   This document adds the following new sub-TLVs to the registry of sub-
   TLVs for TLVs 235, 237 [RFC5120] and TLVs 135,236
   [RFC5305],[RFC5308].

   Value: 32 (suggested - to be assigned by IANA)

   Name: BIER Info

4.  Concepts

4.1.  BIER Domains in Extended Reachability TLVs

   This draft introduces a sub-TLV in the extended reachability TLVs to
   distribute information about BIER domains and services they carry.
   To satisfy the requirements for BIER prefixes per
   [I-D.draft-wijnands-bier-architecture-00] additional information may
   be carried in [I-D.draft-ginsberg-isis-prefix-attributes].

4.2.  BIER Domains

   ISIS extensions are capable of carrying BIER information not only for
   a single BIER domains but for multiple ones.  A BIER domain in ISIS
   is currently always uniquely identified by the tuple of multi-
   topology MT and bitmask length ML it belongs to denoted as <MT,ML>.

   Each such domain itself has as its unique attributes the
   encapsulation used and the type of tree it is using to forward BIER
   frames (currently always SPF).

5.  Procedures

5.1.  Enabling a BIER Domain

   A given domain with masklength ML in a multi-topology MT [RFC5120]
   (denoted as <MT,ML>) is normally not advertised to preserve the
   scaling of the protocol (i.e.  ISIS carries no TLVs containing any of
   the elements related to <MT,ML>) and is enabled by a first BIER sub-
   TLV (Section 6.1) containing <MT,ML> being advertised into the area.
   The trigger itself is outside the scope of this draft but can be for
   example a VPN desiring to initiate a BIER layer as MI-PMSI [RFC6513]
   tree.  It is outside the scope of this document to describe what
   trigger for a router capable of participating <MT,ML> is used to
   start the origination of the necessary information to join into it.






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5.2.  Encapsulation

   All routers in the flooding scope of the BIER TLVs SHOULD advertise
   the same encapsulation for a given <MT,ML>.  A router discovering
   encapsulation advertised that is different from its own MUST report a
   misconfiguration of a specific <MT,ML>.  Each router MUST compute
   BFTs for <MT,ML> using only routers having the same encapsulation as
   its own advertised encapsulation in BIER sub-TLV for <MT,ML>.

5.3.  Label Advertisements for MPLS encapsulated BIER domains

   Each router MAY advertise within the BIER MPLS Encapsulation sub-sub-
   TLV (Section 6.2) of a BIER Info sub-TLV (Section 6.1) for <MT,ML>
   (denoted further as TLV<MT,ML>) a valid starting label value and a
   non-zero range length.  It MUST advertise a valid label value and a
   non-zero range length in case it has computed itself as being on the
   BFT rooted at any of the BFRs with valid BFR-ids (except itself if it
   does NOT have a valid BFR-id) participating in <MT,ML>.

   A router CAN decide to not advertise its TLV<MT,ML> if it does not
   want to participate in the domain due to resource constraints, label
   space optimization, administrative configuration or any other
   reasons.

5.3.1.  Special Consideration

   A router MUST advertise for <MT,ML> label range size that guarantees
   to cover the maximum BFR-id injected into <MT,ML> (which implies a
   certain set id as described in
   [I-D.draft-wijnands-bier-architecture-00]).  Any router that violates
   this condition MUST be excluded from BIER BFTs for <MT,ML>.

5.4.  BFR-id Advertisements

   Each BFER MAY advertise with its TLV<MT,ML> the BFR-id that it has
   administratively chosen.

   If a router discovers that two BFRs it can reach advertise the same
   value for BFR-id for <MT,ML>, it MUST report a misconfiguration and
   disregard those routers for all BIER calculations and procedures for
   <MT,ML> to align with [I-D.draft-wijnands-bier-architecture-00].  It
   is worth observing that based on this procedure routers with
   colliding BFR-id assignments in <MT,ML> MAY still act as BFIRs in
   <MT,ML> but will be never able to receive traffic from other BFRs in
   <MT,ML>.






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5.5.  Flooding

   BIER domain information SHOULD change and force flooding
   infrequently.  Further discussion TBD.

6.  Packet Formats

   All ISIS BIER information is carried within the TLVs 235, 237
   [RFC5120] and TLVs 135,236 [RFC5305],[RFC5308].

6.1.  BIER Info sub-TLV

   This sub-TLV carries the information for the BIER domains that the
   router participates in as BFR.  It can repeat multiple times for
   different domain <MT,ML> combinations.  If the same <MT,ML> domain is
   advertised multiple times with different encapsulations, the result
   is unspecified.

   The sub-TLV carries a single <MT,ML> combination followed by optional
   sub-sub-TLVs specified within its context such as e.g.  BIER MPLS
   Encapsulation per Section 6.2.





          0                   1                   2
          0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |    Type       |   Length      |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         | BM Len|Reservd|    BFR-id                     |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




   Type:  as indicated in IANA section.

   Length:  1 octet.

   Local BitMask Length (BM Len):  Bitmask length for this BIER domain
      that this router is advertising per
      [I-D.draft-wijnands-mpls-bier-encapsulation-01]. 4 bits.

   Reserved  reserved, must be 0 on transmission, ignored on reception.
      4 bits




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   BFR-id  A 2 octet field encoding the BFR-id, as documented in
      [I-D.draft-wijnands-bier-architecture-00].  If set to the invalid
      BFR-id advertising router is not owning any BFR-id.

6.2.  BIER MPLS Encapsulation sub-sub-TLV

   This sub-sub-TLV carries the information for the BIER MPLS
   encapsulations for a certain <MT,ML> and is carried within the BIER
   Info sub-TLV (Section 6.1) that the router participates in as BFR.
   It can repeat only once within it.  If this sub-sub-TLV is included
   more than once, the result is unspecified.



        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|Reservd|                    Label              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



   Type:  value of 0 indicating MPLS encapsulation.

   Length:  1 octet.

   Label Range Size:  Number of labels in the range used on
      encapsulation for this BIER domain, 1 octet.  This MUST never be
      advertise as 0 (zero) and otherwise, this sub-sub-TLV must be
      treated as if not present for BFT calculations and a
      misconfiguration SHOULD be reported by the receiving router.

   Label:  First label of the range used on encapsulation for this BIER
      domain and service, 20 bits.  The label is used for example by
      [I-D.draft-wijnands-mpls-bier-encapsulation-01] to forward traffic
      to sets of BFERs.

   Reserved  reserved, must be 0 on transmission, ignored on reception.
      4 bits

7.  Security Considerations

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




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8.  Acknowledgements

   The draft is aligned with the
   [I-D.draft-psenak-ospf-bier-extension-01] draft as far as the
   protocol mechanisms overlap.

   Many thanks for comments from (in no particular order) Hannes
   Gredler, Ijsbrand Wijnands and Peter Psenak.

9.  Normative References

   [I-D.draft-ginsberg-isis-prefix-attributes]
              Ginsberg et al., U., "IS-IS Prefix Attributes for Extended
              IP and IPv6 Reachability", internet-draft draft-ginsberg-
              isis-prefix-attributes-00.txt, October 2014.

   [I-D.draft-psenak-ospf-bier-extension-01]
              Psenak, P. and IJ. Wijnands, "OSPF Extension for Bit Index
              Explicit Replication", internet-draft draft-ietf-ospf-
              prefix-link-attr-01.txt, October 2014.

   [I-D.draft-wijnands-bier-architecture-00]
              Wijnands, IJ., "Stateless Multicast using Bit Index
              Explicit Replication Architecture", internet-draft draft-
              wijnands-bier-architecture-00.txt, February 2014.

   [I-D.draft-wijnands-mpls-bier-encapsulation-01]
              Wijnands et al., IJ., "Bit Index Explicit Replication
              using MPLS encapsulation", internet-draft draft-wijnands-
              mpls-bier-encapsulation-01.txt, February 2014.

   [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
              dual environments", RFC 1195, December 1990.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4971]  Vasseur, JP., Shen, N., and R. Aggarwal, "Intermediate
              System to Intermediate System (IS-IS) Extensions for
              Advertising Router Information", RFC 4971, July 2007.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120, February 2008.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, October 2008.




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   [RFC5308]  Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, October
              2008.

   [RFC6513]  Rosen, E. and R. Aggarwal, "Multicast in MPLS/BGP IP
              VPNs", RFC 6513, February 2012.

Authors' Addresses

   Tony Przygienda
   Ericsson
   300 Holger Way
   San Jose, CA  95134
   USA

   Email: antoni.przygienda@ericsson.com


   Les Ginsberg
   Cisco Systems
   510 McCarthy Blvd.
   Milpitas, CA  95035
   USA

   Email: ginsberg@cisco.com


   Sam Aldrin
   Huawei
   2330 Central Expressway
   Santa Clara, CA  95051
   USA

   Email: aldrin.ietf@gmail.com


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

   Email: zzhang@juniper.net









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