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Versions: 00 01 02 03

IS-IS for IP Internets                                   H. Gredler, Ed.
Internet-Draft                                    Juniper Networks, Inc.
Intended status: Standards Track                               S. Amante
Expires: November 22, 2013                  Level 3 Communications, Inc.
                                                               T. Scholl
                                                                  Amazon
                                                                L. Jalil
                                                                 Verizon
                                                            May 21, 2013


                    Advertising MPLS labels in IS-IS
               draft-gredler-isis-label-advertisement-03

Abstract

   Historically MPLS label distribution was driven by protocols like
   LDP, RSVP and LBGP.  All of those protocols are session oriented.  In
   order to obtain a label binding for a given destination FEC from a
   given router one needs first to establish an LDP/RSVP/LBGP session
   with that router.

   Advertising MPLS labels in IGPs
   [I-D.gredler-rtgwg-igp-label-advertisement] describes several use
   cases where utilizing the flooding machinery of link-state protocols
   for MPLS label distribution allows to obtain the binding without
   requiring to establish an LDP/RSVP/LBGP session with that router.

   This document describes the protocol extension to distribute MPLS
   label bindings using the IS-IS protocol.

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



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   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 November 22, 2013.

Copyright Notice

   Copyright (c) 2013 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
   (http://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.































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Motivation, Rationale and Applicability  . . . . . . . . . . .  4
     2.1.  Issue: Bi-directionality semantics . . . . . . . . . . . .  5
     2.2.  Issue: IP path semantics . . . . . . . . . . . . . . . . .  5
     2.3.  Issue: Lack of 'path' notion . . . . . . . . . . . . . . .  5
     2.4.  Motivation . . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  MPLS label TLV . . . . . . . . . . . . . . . . . . . . . . . .  6
     3.1.  Flags  . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.2.  subTLV support . . . . . . . . . . . . . . . . . . . . . .  7
     3.3.  IPv4 Prefix ERO subTLV . . . . . . . . . . . . . . . . . .  7
     3.4.  IPv6 Prefix ERO subTLV . . . . . . . . . . . . . . . . . .  8
     3.5.  Unnumbered Interface ID ERO subTLV . . . . . . . . . . . .  9
     3.6.  IPv4 Prefix Bypass ERO subTLV  . . . . . . . . . . . . . . 10
     3.7.  IPv6 Prefix Bypass ERO subTLV  . . . . . . . . . . . . . . 10
     3.8.  Unnumbered Interface ID Bypass ERO subTLV  . . . . . . . . 11
     3.9.  Prefix ERO and Prefix Bypass ERO subTLV path semantics . . 12
     3.10. All Router Block subTLV  . . . . . . . . . . . . . . . . . 12
     3.11. All Router ID IPv4 Map subTLV  . . . . . . . . . . . . . . 14
     3.12. All Router ID IPv6 Map subTLV  . . . . . . . . . . . . . . 15
   4.  Advertising Label Examples . . . . . . . . . . . . . . . . . . 15
     4.1.  Sample Topology  . . . . . . . . . . . . . . . . . . . . . 15
       4.1.1.  Transport IP addresses and Router-IDs  . . . . . . . . 16
       4.1.2.  Link IP addresses  . . . . . . . . . . . . . . . . . . 16
     4.2.  One-hop LSP to an adjacent Router  . . . . . . . . . . . . 17
     4.3.  One-hop LSP to an adjacent Router using a specific link  . 17
     4.4.  Advertisement of Fast Re-Route LSP for One-Hop LSP . . . . 17
     4.5.  Advertisement of an RSVP LSP . . . . . . . . . . . . . . . 18
     4.6.  Advertisement of an LDP LSP  . . . . . . . . . . . . . . . 18
     4.7.  Interarea advertisement of diverse paths . . . . . . . . . 18
     4.8.  Advertisement of SPT labels using 'All Router Block'
           TLV  . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
     4.9.  Expansion of an 'All Router Block' subTLV  . . . . . . . . 20
   5.  Inter Area Protocol Procedures . . . . . . . . . . . . . . . . 21
     5.1.  Applicability  . . . . . . . . . . . . . . . . . . . . . . 21
     5.2.  Data plane operations  . . . . . . . . . . . . . . . . . . 21
     5.3.  Control plane operations . . . . . . . . . . . . . . . . . 21
       5.3.1.  MPLS Label operations  . . . . . . . . . . . . . . . . 21
       5.3.2.  MPLS Label Block operations  . . . . . . . . . . . . . 22
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 22
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 22
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 23
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 23
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 24
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24




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1.  Introduction

   MPLS label allocations are predominantly distributed by using the LDP
   [RFC5036], RSVP [RFC5151] or labeled BGP [RFC3107] protocol.  All of
   those protocols have in common that they are session oriented, which
   means that in order to obtain label binding for a given destination
   FEC from a given router one needs first to establish a direct control
   plane (LDP/RSVP/LBGP) session with that router.

   There are a couple of practical use cases
   [I-D.gredler-rtgwg-igp-label-advertisement] where the consumer of a
   MPLS label binding may not be adjacent to the router that performs
   the binding.  Bringing up an explicit session using the existing
   label distribution protocols between the non-adjacent router that
   binds the label and the router that acts as a consumer of this
   binding is the existing remedy for this dilemma.

   This document describes an IS-IS protocol extension which allows
   routers to advertise MPLS label bindings within and beyond an IGP
   domain, and controlling inter-area distribution.


2.  Motivation, Rationale and Applicability

   One possible way of distributing MPLS labels using IS-IS has been
   described in Segment Routing
   [I-D.previdi-filsfils-isis-segment-routing].  The authors propose to
   re-use the IS-Reach TLVs (22, 23, 222) and Extended IP Prefix TLVs
   (135, 236) for carrying the label information.  While retrofitting
   existing protocol machinery for new purposes is generally a good
   thing, Segment Routing [I-D.previdi-filsfils-isis-segment-routing]
   falls short of addressing some use-cases defined in
   [I-D.gredler-rtgwg-igp-label-advertisement].

   The dominant issue around re-using IS-Reach TLVs and the extended IP
   Prefix TLVs is that both family of TLVs have existing protocol
   semantics, which might not be well suitable to advertising MPLS label
   switched paths in a generic fashion.  These are specifically:

   o  Bi-directionality semantics

   o  IP path semantics

   o  Lack of 'path' notion







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2.1.  Issue: Bi-directionality semantics

   'Bi-directionality semantics', affects the complexity around
   advertisement of unidirectional LSPs.  Label advertisement of per-
   link labels or 'Adj-SIDs' [I-D.previdi-filsfils-isis-segment-routing]
   is done using IS-reach TLVs.  Usually implementations need to have an
   adjacency in 'Up' state prior to advertising this adjacency as IS-
   reach TLV in its Link State PDUs (LSPs).  In order to advertise e.g.
   one-hop MPLS LSP in a given link an implementation first needs to
   have an adjacency, which only transitions to 'Up' state after passing
   the 3-way check.  This implies bi-directionality.  If an
   implementation wants to advertise per-link LSPs to e.g. outside the
   IGP domain then it would need to fake-up an adjacency.  Changing
   existing IGP Adjacency code to support such cases defeats the purpose
   of re-using existing functionality as there is not much common
   functionality to be shared.

2.2.  Issue: IP path semantics

   LSPs pointing to a Node are advertised as 'Node-SIDs'
   [I-D.previdi-filsfils-isis-segment-routing] using the family of
   extended IP Reach TLVs.  That means that in order to advertise a MPLS
   LSP, one is inheriting the semantics of advertising an IP path.
   Consider router A has got existing MPLS LSPs to its entire one-hop
   neighborhood and is re-advertising those MPLS LSPs using IP
   reachability semantics.  Now we have two exact matching IP
   advertisements.  One from the owning router (router B) which
   advertises its stable transport loopback address and another one from
   router A re-advertising a MPLS LSP path to router B. Existing routing
   software may get confused now as the 'stable transport' address shows
   up from multiple places in the network and more worse the IP
   forwarding path for control-plane protocols may get mingled with the
   MPLS data plane.

2.3.  Issue: Lack of 'path' notion

   Both IS-Reach TLVs and IP Prefix Reachability TLVs have a limited
   semantics describing MPLS label-switched paths in the sense of a
   'path'.  Both encoding formats allow to specify a pointer to some
   specific router, but not to describe a MPLS label switched path
   containing all of its path segments.
   [I-D.previdi-filsfils-isis-segment-routing] allows to define
   'Forwarding Adjacencies' as per [RFC4206].  The way to describe a
   path of a given forwarding adjacency is to carry a list of "Segment
   IDs".  That implies that nodes which do not yet participate in
   'Segment routing' or are outside of a 'Segment routing' domain can
   not be expressed using those path semantics.




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   A protocol for advertising MPLS label switched paths, should be
   generic enough to express paths sourced by existing MPLS LSPs, such
   that ingress routers can flexibly combine them according to
   application needs.

2.4.  Motivation

   IGP advertisement of MPLS label switched paths requires a new set of
   protocol semantics (path paradigm), which hardly can be expressed
   using the existing IS-IS protocol.  This document describes IS-IS
   protocol extensions which allows generic advertisement of MPLS label
   bindings in IS-IS.

   The Protocol extensions described in this document are equally
   applicable to IPv4 and IPv6 carried over MPLS.  Furthermore the
   proposed use of distributing MPLS Labels using IGP prototocols
   adheres to the architectural principles laid out in [RFC3031].


3.  MPLS label TLV

   The MPLS Label TLV may be originated by any Traffic Engineering
   [RFC5305] capable router in an IS-IS domain.  The router may
   advertise a single label binding or a block of label bindings.  For
   single label binding advertisement a router needs to provide at least
   a single 'nexthop style' anchor.  The protocol supports more than one
   'nexthop style' anchor to be attached to a Label binding, which
   results into a simple path description language.  In analogy to RSVP
   the terminology for this is called an 'Explicit Route Object' (ERO).
   Since ERO style path notation allows to anchor label bindings to to
   both link and node IP addresses any label switched path, can be
   described.  Furthermore also Label Bindings from other protocols can
   get easily re-advertised.

   Due to the limited size of subTLV space (See [RFC5311] section 4.5
   for details), The MPLS Label TLV has cumulative rather than canceling
   semantics.  If a router originates more than one MPLS Label TLV with
   the same Label value, then the subTLVs of the second, third, etc.
   TLV are accumulated.  Since some subTLVs represent an ordered set
   (e.g.  ERO subTLVs) allocation and ordering of TLV space inside
   particular IS-IS LSP fragment is significant and needs to be tracked.

   The MPLS Label TLV has type 149 and has the following format:








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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     |     Length    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |U|R|R|R|            MPLS Label                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 1: MPLS TLV format

   o  4 bits of flags, consisting of:

      *  1 bit of up/down information (U bit)

      *  3 bits are reserved for future use

   o  20 bits of MPLS label information

   o  0-252 octets of sub-TLVs, where each sub-TLV consists of a
      sequence of:

      *  1 octet of sub-TLV type

      *  1 octet of length of the value field of the sub-TLV

      *  0-250 octets of value

3.1.  Flags

   Flags

      Up/Down Bit: A router may flood MPLS label information across
      level boundaries.  In order to prevent flooding loops, a router
      will Set the Up/Down (U-Bit) when propagating from Level 2 down to
      Level 1.  This is done as per the procedures for IP Prefixes lined
      out in [RFC5302].

3.2.  subTLV support

   An originating router MAY want to attach one or more subTLVs to the
   MPLS label TLV.  SubTLVs presence is inferred from the length of the
   MPLS Label TLV.  If the MPLS Label TLV Length field is > 3 octets
   then one or more subTLVs may be present.

3.3.  IPv4 Prefix ERO subTLV

   The IPv4 ERO subTLV (Type 1) describes a path segment using IPv4
   Prefix style of encoding.  Its appearance and semantics have been



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   borrowed from Section 4.3.3.2 [RFC3209].

   The 'Prefix Length' field contains the length of the prefix in bits.
   Only the most significant octets of the prefix are encoded.  I.e. 1
   octet for prefix length 1 up to 8, 2 octets for prefix length 9 to
   16, 3 octets for prefix length 17 up to 24 and 4 octets for prefix
   length 25 up to 32, etc.

   The 'L' bit in the subTLV is a one-bit attribute.  If the L bit is
   set, then the value of the attribute is 'loose.'  Otherwise, the
   value of the attribute is 'strict.'

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |L|    Type     |     Length    | Prefix Length |  IPv4 Prefix  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | IPv4 Prefix  (continued, variable-length      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                  Figure 2: IPv4 Prefix ERO subTLV format

3.4.  IPv6 Prefix ERO subTLV

   The IPv6 ERO subTLV (Type 2) describes a path segment using IPv6
   Prefix style of encoding.  Its appearance and semantics have been
   borrowed from Section 4.3.3.3 [RFC3209].

   The 'Prefix Length' field contains the length of the prefix in bits.
   Only the most significant octets of the prefix are encoded.  I.e. 1
   octet for prefix length 1 up to 8, 2 octets for prefix length 9 to
   16, 3 octets for prefix length 17 up to 24 and 4 octets for prefix
   length 25 up to 32, ...., 16 octets for prefix length 113 up to 128.

   The 'L' bit in the subTLV is a one-bit attribute.  If the L bit is
   set, then the value of the attribute is 'loose.'  Otherwise, the
   value of the attribute is 'strict.'













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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |L|    Type     |     Length    | Prefix Length | IPv6 Prefix   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | IPv6 Prefix (continued)                                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | IPv6 Prefix (continued)                                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | IPv6 Prefix (continued)                                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | IPv6 Prefix (continued, variable length)      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                  Figure 3: IPv6 Prefix ERO subTLV format

3.5.  Unnumbered Interface ID ERO subTLV

   The appearance and semantics of the 'Unnumbered Interface ID' have
   been borrowed from Section 4 [RFC3477].

   The Unnumbered Interface-ID ERO subTLV (Type 9) describes a path
   segment that spans over an unnumbered interface.  Unnumbered
   interfaces are referenced using the interface index.  Interface
   indices are assigned local to the router and therefore not unique
   within a domain.  All elements in an ERO path need to be unique
   within a domain and hence need to be disambiguated using a domain
   unique Router-ID.

   The 'Router-ID' field contains the router ID of the router which has
   assigned the 'Interface ID' field.  Its purpose is to disambiguate
   the 'Interface ID' field from other routers in the domain.

   IS-IS supports two Router-ID formats:

   o  (TLV 134, 32-Bit format) [RFC5305]

   o  (TLV 140, 128-Bit format) [RFC6119]

   The actual Router-ID format gets derived from the 'Length' field.

   o  For 32-Bit Router-ID width the subTLV length is set to 8 octets.

   o  For 128-Bit Router-ID width the subTLV length is set to 20 octets.

   The 'Interface ID' is the identifier assigned to the link by the
   router specified by the router ID.



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   The 'L' bit in the subTLV is a one-bit attribute.  If the L bit is
   set, then the value of the attribute is 'loose.'  Otherwise, the
   value of the attribute is 'strict.'

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |L|    Type     |     Length    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //                   Router ID (32 or 128 bits)                //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Interface ID (32 bits)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 4: Unnumbered Interface ID ERO subTLV format

3.6.  IPv4 Prefix Bypass ERO subTLV

   The IPv4 Bypass ERO subTLV (Type 3) describes a Bypass LSP path
   segment using IPv4 Prefix style of encoding.  Its appearance and
   semantics have been borrowed from Section 4.3.3.2 [RFC3209].

   The 'Prefix Length' field contains the length of the prefix in bits.
   Only the most significant octets of the prefix are encoded, i.e. 1
   octet for prefix length 1 up to 8, 2 octets for prefix length 9 to
   16, 3 octets for prefix length 17 up to 24 and 4 octets for prefix
   length 25 up to 32, etc.

   The 'L' bit in the subTLV is a one-bit attribute.  If the L bit is
   set, then the value of the attribute is 'loose.'  Otherwise, the
   value of the attribute is 'strict.'

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |L|    Type     |     Length    | Prefix Length |  IPv4 Prefix  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | IPv4 Prefix  (continued, variable-length)     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


              Figure 5: IPv4 Prefix Bypass ERO subTLV format

3.7.  IPv6 Prefix Bypass ERO subTLV

   The IPv6 ERO subTLV (Type 4) describes a Bypass LSP path segment
   using IPv6 Prefix style of encoding.  Its appearance and semantics
   have been borrowed from Section 4.3.3.3 [RFC3209].



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   The 'Prefix Length' field contains the length of the prefix in bits.
   Only the most significant octets of the prefix are encoded, i.e. 1
   octet for prefix length 1 up to 8, 2 octets for prefix length 9 to
   16, 3 octets for prefix length 17 up to 24 and 4 octets for prefix
   length 25 up to 32, ...., 16 octets for prefix length 113 up to 128.

   The 'L' bit in the subTLV is a one-bit attribute.  If the L bit is
   set, then the value of the attribute is 'loose.'  Otherwise, the
   value of the attribute is 'strict.'

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |L|    Type     |     Length    | Prefix Length | IPv6 Prefix   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | IPv6 Prefix (continued)                                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | IPv6 Prefix (continued)                                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | IPv6 Prefix (continued)                                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | IPv6 Prefix (continued, variable length)      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


              Figure 6: IPv6 Prefix Bypass ERO subTLV format

3.8.  Unnumbered Interface ID Bypass ERO subTLV

   The appearance and semantics of the 'Unnumbered Interface ID' have
   been borrowed from Section 4 [RFC3477].

   The Unnumbered Interface-ID Bypass ERO subTLV (Type 10) describes a
   Bypass LSP path segment that spans over an unnumbered interface.
   Unnumbered interfaces are referenced using the interface index.
   Interface indices are assigned local to the router and therefore not
   unique within a domain.  All elements in an ERO path need to be
   unique within a domain and hence need to be disambiguated using a
   domain unique Router-ID.

   The 'Router-ID' field contains the router ID of the router which has
   assigned the 'Interface ID' field.  Its purpose is to disambiguate
   the 'Interface ID' field from other routers in the domain.

   IS-IS supports two Router-ID formats:






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   o  (TLV 134, 32-Bit format) [RFC5305]

   o  (TLV 140, 128-Bit format) [RFC6119]

   The actual Router-ID format gets derived from the 'Length' field.

   o  For 32-Bit Router-ID width the subTLV length is set to 8 octets.

   o  For 128-Bit Router-ID width the subTLV length is set to 20 octets.

   The 'Interface ID' is the identifier assigned to the link by the
   router specified by the router ID.

   The 'L' bit in the subTLV is a one-bit attribute.  If the L bit is
   set, then the value of the attribute is 'loose.'  Otherwise, the
   value of the attribute is 'strict.'

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |L|    Type     |     Length    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //                   Router ID (32 or 128 bits)                //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Interface ID (32 bits)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 7: Unnumbered Interface ID Bypass ERO subTLV format

3.9.  Prefix ERO and Prefix Bypass ERO subTLV path semantics

   All 'Prefix ERO' and 'Prefix Bypass ERO' information represents an
   ordered set which describes the segments of a label-switched path.
   The last Prefix ERO subTLV describes the segment closest to the
   egress point of the LSP.  Contrary the first Prefix ERO subTLV
   describes the first segment of a label switched path.  If a router
   extends or stitches a label switched path it MUST prepend the new
   segments path information to the Prefix ERO list.  The same ordering
   applies for the Bypass ERO labels.  An implementation SHOULD first
   encode all primary path EROs followed by the bypass EROs.

3.10.  All Router Block subTLV

   The 'All Router Block' subTLV (Type 6) denominates the label block
   size of an MPLS Label advertisement and its semantics to connect to
   all routers in a given IS-IS domain using a local assigned [RFC3031]
   label range.  Note that the actual mapping of a router within the
   label range is done using the subTLVs described in Section 3.11 and



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   Section 3.12.  Since generation of an 'All Router ID IPv4 Map' or
   'All Router ID IPv6 Map' subTLV is a local policy decision, it might
   be the case that connectivity is provided not to 'All' but rather a
   subset of 'All' routers.  Keeping policy decisions aside, for
   simplicity reasons, assume that All Routers in a domain do generate
   either the 'All Router ID IPv4 Map' or 'All Router ID IPv6 Map'
   subTLVs and therefore all routers desire construction of a Label
   switched path from every source router in the network.  The basic
   concept of using label blocks to provide connectivity to a set of
   routers has been borrowed from [RFC4761] which allows to advertise
   labels from multiple end-points using a single control-plane message.
   The difference to [RFC4761] is that rather than advertising where a
   particular packet came from (=source semantics), destination
   semantics (where a particular packet will be going to) is advertised.

   Along with each label block a router advertises one for more 'IDs'.
   The 'ID' must be unique within a given domain.  The 'ID' serves as
   ordinal to determine the actual label value inside the set of all
   advertised label ranges of a given router.  A receiving router uses
   the ordinal to determine the actual label value in order to construct
   forwarding state to a particular destination router.  The 'ID' is
   separately advertised using the subTLVs described in Section 3.11 and
   Section 3.12.

   The ability to advertise more than one label block eases operational
   procedures for increasing the number of supported routers within a
   domain.  For example consider a given domain has got support for <M>
   routers and runs out of ID space.  It simply advertises one more
   label block to cover additional ordinals outside the range of the
   first label block.  An example of label-block expansion is described
   in more detail in Section 4.9

   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            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Block Size            | Algo  |      Topology-ID      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 8: All Router Block subTLV format

   The 'Block Size' value contains the size of the label advertisement.
   The 'value determines the amount of reachable router endpoints within
   a given Label block.  It MUST contain a value greater or equal than
   two.  Note that the label base is inferred from the Label Value in
   the carrying MPLS Label TLV.  For example if a router wants to
   advertise a label range of 5000-5099 then it would need to generate a



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   MPLS Label TLV with a Label value of 5000 and a Block Size of 100.

   The 'Algo' value denominates the path computation algorithm in order
   to calculate the forwarding topology.  The basic SPF algorithm has an
   assigned 'Algo' code point of zero.  The purpose of the 'Algo' field
   is to extend the notion of Label Block Signaling to arbitrary
   algorithms like for example 'MRT'
   ([I-D.ietf-rtgwg-mrt-frr-architecture].  Advertised Label Blocks with
   an unknown, unsupported or non-configured algorithm MUST be silently
   ignored.

   The 'Reserved' bits are for future use.  They should be zero on
   transmission and ignored on receipt.

   The 'Topology-ID' field contains the Multi Topology ID ([RFC5120])
   for which the advertised Label Block does apply.  The basic IPv4
   unicast Topology has an assigned 'Topology-ID' code point of zero.
   The basic IPv6 unicast Topology has an assigned 'Topology=ID' code
   point of 2.  Advertised Label Blocks with an unknown, unsupported or
   non-configured Topology-ID MUST be silently ignored.

   A MPLS Label TLV containing the 'All Router Block' subTLV MUST only
   contain the 'All Router IPv4 Map' subTLV (Section 3.11) or the 'All
   Router IPv6 Map' subTLV (Section 3.12).

3.11.  All Router ID IPv4 Map subTLV

   The 'All Router ID IPv4 Map' TLV (Type 7) maps an 'ID' to a given
   stable transport IPv4 address.  Its purpose is to associate a given
   transport IPv4 IP address to the ordinal inside a label range as
   described in Section 3.10.

   A router MAY advertise more than one 'ID' to 'IPv4 address' mapping
   pair, in case it has more than one stable transport IPv4 address.

   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            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     IPv4 Address (4 octets)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               ID              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 9: All Router ID IPv4 Map subTLV format

   The 'IPv4 address' contains stable IPv4 transport address of a given



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   router.

   The 'ID' contains the ordinal value of an advertising router inside
   the set of all advertised label blocks of a given router.

3.12.  All Router ID IPv6 Map subTLV

   The 'All Router ID IPv6 Map' TLV (Type 8) maps an 'ID' to a given
   stable transport IPv6 address.  Its purpose is to associate a given
   transport IPv6 IP address to the ordinal inside a label range as
   described in Section 3.10.

   A router MAY advertise more than one 'ID' to 'IPv6 address' mapping
   pair, in case it has more than one stable transport IPv6 address.

   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            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | IPv6 Address (16 octets)                                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | IPv6 Address (continued)                                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | IPv6 Address (continued)                                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | IPv6 Address (continued)                                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               ID              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 10: All Router ID IPv6 Map subTLV format

   The 'IPv6 address' contains the stable IPv6 transport address of a
   given router.

   The 'ID' contains the ordinal value of an advertising router inside
   the set of all advertised label blocks of a given router.


4.  Advertising Label Examples

4.1.  Sample Topology

   The following topology (Figure 11) and IP addresses shall be used
   throughout the Label advertisement examples.





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                         AS1                           :    AS 2
                                                       :
                          :                            :
              Level 1     :     Level 2                :
                          :                            :
                          :                            :
   +-----+             +-----+-IP3--1-IP4--+-----+     :
   | R1  +-IP1--1-IP2--+ R2  |             | R3  |     :
   +--+--+             +--+--+-IP5--3-IP6--+--+--+-IP15-IP16-
      |                   |                   |        :     \
     IP9                 IP7                IP13       :      \
      |                   |                   |        :    +--+--+
      1                   1                   1        :    |  R7 |
      |                   |                   |        :    +--+--+
    IP10                 IP8                IP14       :      /
      |                   |                   |        :     /
   +--+--+             +--+--+             +--+--+-IP17-IP18-
   |  R4 +-IP19-2-IP20-+ R5  |-IP11-2-IP12-| R6  |     :
   +-----+             +-----+             +-----+     :
                          :                            :
                          :                            :
                          :                            :

                        Figure 11: Sample Topology

4.1.1.  Transport IP addresses and Router-IDs

   o  R1: 192.168.1.1

   o  R2: 192.168.1.2

   o  R3: 192.168.1.3

   o  R4: 192.168.1.4

   o  R5: 192.168.1.5

   o  R6: 192.168.1.6

   o  R7: 192.168.1.7

4.1.2.  Link IP addresses

   o  R1 to R2 link: 10.0.0.1, 10.0.0.2

   o  R1 to R4 link: 10.0.0.9, 10.0.0.10





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   o  R2 to R3 link #1: 10.0.0.3, 10.0.0.4

   o  R2 to R3 link #2: 10.0.0.5, 10.0.0.6

   o  R2 to R5 link: 10.0.0.7, 10.0.0.8

   o  R3 to R6 link: 10.0.0.13, 10.0.0.14

   o  R3 to R7 link: 10.0.0.15, 10.0.0.16

   o  R4 to R5 link: 10.0.0.19, 10.0.0.20

   o  R5 to R6 link: 10.0.0.11, 10.0.0.12

   o  R6 to R7 link: 10.0.0.17, 10.0.0.18

   The IGP link metrics are displayed in the middle of the link.  All of
   them are assumed to be bi-directional.

4.2.  One-hop LSP to an adjacent Router

   If R1 would advertise a label <N> bound to a one-hop LSP from R1 to
   R2 it would encode as follows:

      TLV 149: MPLS label <N>, Flags {}:

         IPv4 Prefix ERO subTLV: 192.168.1.2/32, Strict

4.3.  One-hop LSP to an adjacent Router using a specific link

   If R2 would advertise a label <N> bound to a one-hop LSP from R2 to
   R3, using the link #2 it would encode as follows

      TLV 149: MPLS label <N>, Flags {}:

         IPv4 Prefix ERO subTLV: 10.0.0.6/32, Strict

4.4.  Advertisement of Fast Re-Route LSP for One-Hop LSP

   R2 may advertise a one-hop LSP from R2 to R3, along with a Link
   Protection Bypass for the directly adjacent links between those two
   nodes.  The Link Protection Bypass would use the path: {R2, R5, R6,
   R3}.  R2 would encode both the primary LSP and Link Protection Bypass
   LSP as follows:

      TLV 149: MPLS label <N>, Flags {}:





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         IPv4 Prefix ERO subTLV: 192.168.1.3/32, Strict

         IPv4 Prefix Bypass ERO subTLV: 192.168.1.5/32, Strict

         IPv4 Prefix Bypass ERO subTLV: 192.168.1.6/32, Strict

         IPv4 Prefix Bypass ERO subTLV: 192.168.1.3/32, Strict

4.5.  Advertisement of an RSVP LSP

   Consider a RSVP LSP name "R2-to-R6" traversing (R2 to R3 using link
   #1, R6):

   If R2 would advertise a label <N> bound to the RSVP LSP named
   'R2-to-R6', it would encode as follows

      TLV 149: MPLS label <N>, Flags {}:

         IPv4 Prefix ERO subTLV: 10.0.0.4/32, Strict

         IPv4 Prefix ERO subTLV: 192.168.1.6/32, Strict

4.6.  Advertisement of an LDP LSP

   Consider R2 that creates a LDP label binding for FEC 172.16.0.0/12
   using label <N>.

   If R2 would re-advertise this binding in IS-IS it would encode as
   follows

      TLV 149: MPLS label <N>, Flags {}:

         IPv4 Prefix ERO subTLV: 172.16.0.0/12, Loose

4.7.  Interarea advertisement of diverse paths

   Consider two R2->R6 paths: {R2, R3, R6} and {R2, R5, R6}

   Consider two R5->R3 paths: {R5, R2, R3} and {R5, R6, R3}

   R2 encodes its two paths to R6 as follows:

      TLV 149: MPLS label <N1>, Flags {}:

         IPv4 Prefix ERO subTLV: 192.168.1.3, Strict

         IPv4 Prefix ERO subTLV: 192.168.1.6, Strict




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      TLV 149: MPLS label <N2>, Flags {}:

         IPv4 Prefix ERO subTLV: 192.168.1.5, Strict

         IPv4 Prefix ERO subTLV: 192.168.1.6, Strict

   R5 encodes its two paths to R3 as follows:

      TLV 149: MPLS label <N1>, Flags {}:

         IPv4 Prefix ERO subTLV: 192.168.1.2, Strict

         IPv4 Prefix ERO subTLV: 192.168.1.3, Strict

      TLV 149: MPLS label <N2>, Flags {}:

         IPv4 Prefix ERO subTLV: 192.168.1.6, Strict

         IPv4 Prefix ERO subTLV: 192.168.1.3, Strict

   A receiving L1 router does see now all 4 paths and may decide to
   load-balance across all or a subset of them.

4.8.  Advertisement of SPT labels using 'All Router Block' TLV

   All routers within a given area MUST advertise their Label Blocks
   along with an 'ID'.

   If R2 would advertise a label block <N1> with a size of 10, declaring
   SPT label forwarding support to all routers within a given domain, it
   would encode as follows:

      TLV 149: MPLS Label <N1>, Flags {}:

         All Router Block subTLV: Block Size 10, Algo 0, Topology 0

         All Router ID IPv4 Map subTLV: ID 2, 192.168.1.2

   If R3 would advertise a label block <N2> with a size of 10, declaring
   SPT label forwarding support to all routers within a given domain, it
   would encode as follows:

      TLV 149, MPLS Label <N2>, Flags {}:

         All Router Block subTLV: Block Size 10, Algo 0, Topology 0

         All Router ID IPv4 Map subTLV: ID 3, 192.168.1.3




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   If R5 would advertise a label block <N3> with a size of 10, declaring
   SPT label forwarding support to all routers within a given domain, it
   would encode as follows:

      TLV 149, MPLS Label <N3>, Flags {}:

         All Router Block subTLV: Block Size 10, Algo 0, Topology 0

         All Router ID IPv4 Map subTLV: ID 5, 192.168.1.5

   If R6 would advertise a label block <N4> with a size of 10, declaring
   SPT label forwarding support to all routers within a given domain, it
   would encode as follows:

      TLV 149, MPLS Label <N4>, Flags {}:

         All Router Block subTLV: Block Size 10, Algo 0, Topology 0

         All Router ID IPv4 Map subTLV: ID 6, 192.168.1.6

   Consider now R2 constructing a SPT label for R6.  R2s SPT to R6 is
   {R2, IP4, R3, R6}.  R2 first determines if its downstream router (R3)
   has advertised a label-block.  Since R3 has advertised a label block
   'N2' and it has received R6 'ID' of 6 it will be picking the 6th
   label value inside the advertised range of its downstream neighbor.
   Specifically R2 MUST be program a MPLS SWAP for its own label range
   Label(N1+6) to Label(N2+6), NH 10.0.0.4 into its MPLS transit RIB.
   Furthermore R2 MAY program a MPLS PUSH operation for IP 192.168.1.6
   to Label (N2+6), NH 10.0.0.4 into its IPv4 tunnel RIB.

   Next walk down to R3, which is the next router on the SPT tree
   towards R6.  R3s SPT to R6 is {R3, R6}.  R3 determines if its
   downstream router (R6) has advertised a label-block.  Since R6 has
   advertised a label block 'N4' and it has received R6 'ID' of 6 it
   will be picking the 6th label value inside the advertised range of
   its downstream neighbor.  Since R3 is the penultimate router to R6 it
   MUST program a MPLS POP for its own label range Label(N2+6) NH
   10.0.0.14 into its MPLS transit RIB.  Furthermore R3 MAY program a
   MPLS NOP for IP 192.168.1.6, NH 10.0.0.14 into its IPv4 tunnel RIB.

4.9.  Expansion of an 'All Router Block' subTLV

   All routers within a given area MUST advertise their Label Blocks
   along with an 'ID'.  Now assume that the initial label block size
   assignment is too small to support all routers which generate an
   ordinal within an IGP domain.  Consider the seven routers in
   Figure 11, and assume that R7 advertises a new ID '15' using an 'All
   Router ID Map' subTLV.  ID '15' is outside of the range of '10' as



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   per the previous example in Section 4.8.  Now all the routers in an
   IGP domain need to advertise one more label block in order to map the
   ID '15' to an actual label value.

   All routers would advertise in addition to their label block <N> with
   a size of 10, a second label block <N2> with a size sufficient enough
   that the new ordinal can get covered.  In this example the same block
   size 10 is used also for the second label block.  For example router
   R2 would advertise the following label bindings.

      TLV 149: MPLS Label <N1>, Flags {}:

         All Router Block subTLV: Block Size 10, Algo 0, Topology 0

         All Router ID IPv4 Map subTLV: ID 2, 192.168.1.2

      TLV 149: MPLS Label <N2>, Flags {}:

         All Router Block subTLV: Block Size 10, Algo 0, Topology 0

   Now the upstream router can map the new ID of R7 to an actual label
   value, as ID '15' corresponds to the 5th label inside the second
   Label block.


5.  Inter Area Protocol Procedures

5.1.  Applicability

   Propagation of a MPLS LSP across a level boundary is a local policy
   decision.

5.2.  Data plane operations

   If local policy dictates that a given L1L2 router needs to re-
   advertise a MPLS LSPs from one Level to another then it MUST allocate
   a new label and program its label forwarding table to connect the new
   label to the path in the respective other level.  Depending on how to
   reach the re-advertised LSP, this is typically done using a MPLS
   'SWAP' or 'SWAP/PUSH' data plane operation.

5.3.  Control plane operations

5.3.1.  MPLS Label operations

   If local policy dictates that a given L1L2 router re-advertises a
   MPLS LSPs into another Level then it MUST prepend its "Traffic-
   Engineering-ID" as a loose hop in the Prefix ERO subTLV list.  If the



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   LSP is propagated from a higher Level to a lower Level then the
   'Down' bit MUST be set.

5.3.2.  MPLS Label Block operations

   If local policy dictates that a given L1L2 router advertises its 'All
   Router Block' into another Level, then it also MUST re-advertise all
   known 'ID' ordinals (again gated by policy) to the respective other
   Level.  Without knowledge of all 'ID's in the network no router is
   able to construct SPT label switched paths.  If a Label Block and its
   ID mappings are propagated from a higher Level to a lower Level then
   the 'Down' bit MUST be set.


6.  Acknowledgements

   Many thanks to Yakov Rekhter and John Drake for their useful
   comments.


7.  IANA Considerations

   This documents request allocation for the following TLVs and subTLVs.

   +-----+--------+----------------------+------+---------+------------+
   | PDU | TLV    | subTLV               | Type | subType | #Occurence |
   +-----+--------+----------------------+------+---------+------------+
   | LSP | MPLS   |                      | 149  |         |        >=0 |
   |     | Label  |                      |      |         |            |
   |     |        | IPv4 Prefix ERO      |      | 1       |        >=0 |
   |     |        | IPv6 Prefix ERO      |      | 2       |        >=0 |
   |     |        | Unnumbered Interface |      | 9       |        >=0 |
   |     |        | ID ERO               |      |         |            |
   |     |        | IPv4 Prefix Bypass   |      | 3       |        >=0 |
   |     |        | ERO                  |      |         |            |
   |     |        | IPv6 Prefix Bypass   |      | 4       |        >=0 |
   |     |        | ERO                  |      |         |            |
   |     |        | Unnumbered Interface |      | 10      |        >=0 |
   |     |        | ID Bypass ERO        |      |         |            |
   |     |        | All Router Block     |      | 6       |        >=0 |
   |     |        | All Router ID IPv4   |      | 7       |        >=0 |
   |     |        | Map                  |      |         |            |
   |     |        | All Router ID IPv6   |      | 8       |        >=0 |
   |     |        | Map                  |      |         |            |
   +-----+--------+----------------------+------+---------+------------+

                         Table 1: IANA allocations




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   The MPLS Label TLV requires a new sub-registry.  Type value 149 has
   been assigned, with a starting sub-TLV value of 1, range from 1-127,
   and managed by Expert Review.


8.  Security Considerations

   This document does not introduce any change in terms of IS-IS
   security.  It simply proposes to flood MPLS label information via the
   IGP.  All existing procedures to ensure message integrity do apply
   here.


9.  References

9.1.  Normative References

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

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031, January 2001.

   [RFC3107]  Rekhter, Y. and E. Rosen, "Carrying Label Information in
              BGP-4", RFC 3107, May 2001.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, December 2001.

   [RFC3477]  Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links
              in Resource ReSerVation Protocol - Traffic Engineering
              (RSVP-TE)", RFC 3477, January 2003.

   [RFC4206]  Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
              Hierarchy with Generalized Multi-Protocol Label Switching
              (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.

   [RFC4761]  Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
              (VPLS) Using BGP for Auto-Discovery and Signaling",
              RFC 4761, January 2007.

   [RFC5036]  Andersson, L., Minei, I., and B. Thomas, "LDP
              Specification", RFC 5036, October 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.



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   [RFC5151]  Farrel, A., Ayyangar, A., and JP. Vasseur, "Inter-Domain
              MPLS and GMPLS Traffic Engineering -- Resource Reservation
              Protocol-Traffic Engineering (RSVP-TE) Extensions",
              RFC 5151, February 2008.

   [RFC5302]  Li, T., Smit, H., and T. Przygienda, "Domain-Wide Prefix
              Distribution with Two-Level IS-IS", RFC 5302,
              October 2008.

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

   [RFC5311]  McPherson, D., Ginsberg, L., Previdi, S., and M. Shand,
              "Simplified Extension of Link State PDU (LSP) Space for
              IS-IS", RFC 5311, February 2009.

   [RFC6119]  Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
              Engineering in IS-IS", RFC 6119, February 2011.

9.2.  Informative References

   [I-D.gredler-rtgwg-igp-label-advertisement]
              Gredler, H., Amante, S., Scholl, T., and L. Jalil,
              "Advertising MPLS labels in IGPs",
              draft-gredler-rtgwg-igp-label-advertisement-05 (work in
              progress), May 2013.

   [I-D.ietf-rtgwg-mrt-frr-architecture]
              Atlas, A., Kebler, R., Envedi, G., Csaszar, A., Tantsura,
              J., Konstantynowicz, M., White, R., and M. Shand, "An
              Architecture for IP/LDP Fast-Reroute Using Maximally
              Redundant Trees", draft-ietf-rtgwg-mrt-frr-architecture-02
              (work in progress), February 2013.

   [I-D.previdi-filsfils-isis-segment-routing]
              Previdi, S., Filsfils, C., Bashandy, A., Horneffer, M.,
              Decraene, B., Litkowski, S., Milojevic, I., Shakir, R.,
              Ytti, S., Henderickx, W., and J. Tantsura, "Segment
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Gredler, et al.         Expires November 22, 2013              [Page 24]


Internet-Draft      Advertising MPLS labels in IS-IS            May 2013


Authors' Addresses

   Hannes Gredler (editor)
   Juniper Networks, Inc.
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089
   US

   Email: hannes@juniper.net


   Shane Amante
   Level 3 Communications, Inc.
   1025 Eldorado Blvd
   Broomfield, CO  80021
   US

   Email: shane@level3.net


   Tom Scholl
   Amazon
   Seattle, WN
   US

   Email: tscholl@amazon.com


   Luay Jalil
   Verizon
   1201 E Arapaho Rd.
   Richardson, TX  75081
   US

   Email: luay.jalil@verizon.com
















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