LSR                                                           A. Smirnov
Internet-Draft                                       Cisco Systems, Inc.
Updates: 5786 (if approved)                                    A. Retana
Intended status: Standards Track                          Huawei R&D USA
Expires: April 6, 2019                                         M. Barnes
                                                     Cisco Systems, Inc.
                                                         October 3, 2018

   OSPF Routing with Cross-Address Family Traffic Engineering Tunnels


   When using Traffic Engineering (TE) in a dual-stack IPv4/IPv6 network
   the Multiprotocol Label Switching (MPLS) TE Label Switched Paths
   (LSP) infrastructure may be duplicated, even if the destination IPv4
   and IPv6 addresses belong to the same remote router.  In order to
   achieve an integrated MPLS TE LSP infrastructure, OSPF routes must be
   computed over MPLS TE tunnels created using information propagated in
   another OSPF instance.  This is solved by advertising cross-address
   family (X-AF) OSPF TE information.

   This document describes an update to RFC5786 that allows for the easy
   identification of a router's local X-AF IP addresses.

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
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   This Internet-Draft will expire on April 6, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( 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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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Backward Compatibility  . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   TE Extensions to OSPFv2 [RFC3630] and to OSPFv3 [RFC5329] have been
   described to support intra-area TE in IPv4 and IPv6 networks,
   respectively.  In both cases the TE database provides a tight
   coupling between the routed protocol and TE signaling information in
   it.  In other words, any use of the TE link state database is limited
   to IPv4 for OSPFv2 [RFC2328] and IPv6 for OSPFv3 [RFC5340].

   In a dual stack network it may be desirable to set up common MPLS TE
   LSPs to carry traffic destined to addresses from different address
   families on a router.  The use of common LSPs eases potential
   scalability and management concerns by halving the number of LSPs in
   the network.  Besides, it allows operators to group traffic based on
   business characteristics and/or applications or class of service, not
   constrained by the network protocol which carries it.

   For example, an LSP created based on MPLS TE information propagated
   by OSPFv2 instance can be defined to carry both IPv4 and IPv6
   traffic, instead of having both OSPFv2 and OSPFv3 to provision a
   separate LSP for each address family.  Even if in some cases the
   address family-specific traffic is to be separated, the calculation
   from a common database may prove operationally beneficial.

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   A requirement when creating a common MPLS TE infrastructure is the
   ability to reliably map the X-AF family addresses to the
   corresponding advertising tail-end router.  This mapping is a
   challenge because the LSAs containing the routing information are
   carried in one OSPF instance while the TE calculation may be done
   using a TE database from a different instance.

   A simple solution to this problem is to rely on the Router ID to
   identify a node in the corresponding OSPFv2 and OSPFv3 databases.
   This solution would mandate both instances on the same router to be
   configured with the same Router ID.  However, relying on the
   correctness of the configuration puts additional burden on network
   management and adds cost to the operation of the network.  The
   network becomes even more difficult to manage if OSPFv2 and OSPFv3
   topologies do not match exactly, for example if area borders are
   drawn differently in the two protocols.  Also, if the routing
   processes do fall out of sync (having different Router IDs, even if
   for local administrative reasons), there is no defined way for other
   routers to discover such misalignment and to take any corrective
   measures (such as to avoid routing through affected TE tunnels or
   issuing warning to network management).  The use of misaligned router
   IDs may result in delivering the traffic to the wrong tail-end
   router, which could lead to suboptimal routing or even traffic loops.

   This document describes an update to [RFC5786] that allows for the
   easy identification of a router's local X-AF IP addresses.  Routers
   using the Node Attribute TLV [RFC5786] can include non-TE enabled
   interface addresses in their OSPF TE advertisements, and also use the
   same sub-TLVs to carry X-AF information, facilitating the mapping
   mentioned above.

   The method described in this document can also be used to compute
   X-AF mapping of egress LSR for sub-LSPs of a Point-to-Multipoint LSP
   (see [RFC4461]).  Considerations of using Point-to-Multipoint MPLS TE
   for X-AF traffic forwarding is outside the scope of this

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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3.  Operation

   [RFC5786] defined the Node IPv4 Local Address and Node IPv6 Local
   Address sub-TLVs of the Node Attribute TLV for a router to advertise
   additional local IPv4 and IPv6 addresses.  To solve the problem
   outlined in [RFC5786] OSPFv2 would advertise and use only IPv4
   addresses and OSPFv3 would advertise and use only IPv6 addresses.

   This document updates [RFC5786] so that a router can also announce
   one or more local X-AF addresses using the corresponding Local
   Address sub-TLV.  In other words, to implement the X-AF routing
   technique proposed in this document, OSPFv2 will advertise the Node
   IPv6 Local Address sub-TLV and OSPFv3 will advertise the Node IPv4
   Local Address sub-TLV, possibly in addition to advertising other IP
   addresses as documented by [RFC5786].

   A node that implements X-AF routing SHOULD advertise in the
   corresponding Node Local Address sub-TLV all X-AF IP addresses local
   to the router that can be used by Constrained SPF (CSPF) to calculate
   MPLS TE LSPs.  In general, OSPF SHOULD advertise the IP address
   listed in the Router Address TLV of the X-AF instance maintaining
   MPLS TE database plus any additional local addresses advertised by
   the X-AF OSPF instance in its Node Local Address sub-TLV.
   Implementation MAY advertise other local X-AF addresses.

   If the Node Attribute TLV carries both the Node IPv4 Local Address
   sub-TLV and the Node IPv6 Local Address sub-TLV, then the X-AF
   component must be considered for the consolidated calculation of MPLS
   TE LSPs.  Both instances may carry the required information, it is
   left to local configuration to determine which database is used.

   On Area Border Routers (ABR), each advertised X-AF IP address MUST be
   advertised into at most one area.  If OSPFv2 and OSPFv3 area borders
   match (i.e. for each interface area number for OSPFv2 and OSPFv3
   instances is numerically equal), then the X-AF addresses MUST be
   advertised into the same area in both instances.  This allows other
   ABRs connected to the same set of areas to know with which area to
   associate MPLS TE tunnels.

   During the X-AF routing calculation, X-AF IP addresses are used to
   map locally created LSPs to tail-end routers in the LSDB.  The
   mapping algorithm can be described as:

      Walk the list of all MPLS TE tunnels for which the computing
      router is a head-end.  For each MPLS TE tunnel T:

   1.  If T's destination IP address is from the same address family as
       the computing OSPF instance, then the tunnel must have been

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       signaled based on MPLS TE information propagated in the same OSPF
       instance.  Process the tunnel as per [RFC3630] or [RFC5329].

   2.  Otherwise it is a X-AF MPLS TE tunnel.  Note tunnel's destination
       IP address.

   3.  Walk the X-AF IP addresses in the LSDBs of all connected areas.
       If a matching IP address is found, advertised by router R in area
       A, then mark the tunnel T as belonging to area A and terminating
       on tail-end router R.  Assign an intra-area SPF cost to reach
       router R within area A as the IGP cost of tunnel T.

   After completing this calculation, each TE tunnel is associated with
   an area and tail-end router in terms of the routing LSDB of the
   computing OSPF instance and has a metric.

   Note that for clarity of description the mapping algorithm is
   specified as a single calculation.  Actual implementations for the
   efficiency may choose to support equivalent mapping functionality
   without implementing the algorithm exactly as it is described.

   As an example lets consider a router in dual-stack network running
   OSPFv2 and OSPFv3 for IPv4 and IPv6 routing correspondingly.  Suppose
   OSPFv2 instance is used to propagate MPLS TE information and the
   router is configured to accept TE LSPs terminating at local addresses and  Then the router will advertise into
   OSPFv2 instance IPv4 address in the Router Address TLV,
   additional local IPv4 address in the Node IPv4 Local
   Address sub-TLV, plus other Traffic Engineering TLVs as required by
   [RFC3630].  If OSPFv3 instance in the network is enabled for X-AF TE
   routing (that is, to use for IPv6 routing MPLS TE LSPs computed by
   OSPFv2), then the OSPFv3 instance of the router will advertise the
   Node IPv4 Local Address sub-TLV listing local IPv4 addresses and  Other routers in the OSPFv3 network
   will use this information to reliably identify this router as egress
   LSR for MPLS TE LSPs terminating at either or

4.  Backward Compatibility

   Node Attribute TLV and Node Local Address sub-TLVs and their usage
   are defined in [RFC5786] and updated by [RFC6827].  Way of using
   these TLVs as specified in this document is fully backward compatible
   with previous standard documents.

   An implementation processing Node Attribute TLV MUST interpret its
   content as follows:

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   o  If the Node Attribute TLV contains Local TE Router ID sub-TLV then
      this Node Attribute TLV MUST be treated as carrying routing
      information for ASON (Automatically Switched Optical Network) and
      processed as specified in [RFC6827].

   o  Otherwise Node Attribute TLV contains one or more instance(s) of
      Node IPv4 Local Address and/or Node IPv6 Local Address sub-TLVs.
      Meaning of each Local Address sub-TLV has to be identified

      *  If Node Local Address sub-TLV belongs to the same address
         family as instance of OSPF protocol advertising it then address
         carried in the sub-TLV MUST be treated as described in

      *  Otherwise the address is used for X-AF tunnel tail-end mapping
         as defined by this document.

   Only routers that serve as endpoints for one or more TE tunnels MUST
   be upgraded to support procedures described in this document:

   o  Tunnel tailends need to advertise Node IPv4 Local Address and/or
      Node IPv6 Local Address sub-TLVs as described in this

   o  Tunnel headends need to perform X-AF routing calculation as
      described in this specification

   Other routers in the network do not need to support X-AF procedures.

5.  Security Considerations

   This document introduces no new security concerns.  Security
   considerations of using Node Attribute TLV are discussed in

6.  IANA Considerations

   This document has no IANA actions.

7.  Acknowledgements

   The authors would like to thank Peter Psenak and Eric Osborne for
   early discussions and Acee Lindem for discussing compatibility with
   ASON extensions.

   We would also like to thank the authors of RFC5786 for laying down
   the foundation for this work.

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8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC5786]  Aggarwal, R. and K. Kompella, "Advertising a Router's
              Local Addresses in OSPF Traffic Engineering (TE)
              Extensions", RFC 5786, DOI 10.17487/RFC5786, March 2010,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

8.2.  Informative References

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328,
              DOI 10.17487/RFC2328, April 1998,

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              DOI 10.17487/RFC3630, September 2003,

   [RFC4461]  Yasukawa, S., Ed., "Signaling Requirements for Point-to-
              Multipoint Traffic-Engineered MPLS Label Switched Paths
              (LSPs)", RFC 4461, DOI 10.17487/RFC4461, April 2006,

   [RFC5329]  Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,
              "Traffic Engineering Extensions to OSPF Version 3",
              RFC 5329, DOI 10.17487/RFC5329, September 2008,

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,

   [RFC6827]  Malis, A., Ed., Lindem, A., Ed., and D. Papadimitriou,
              Ed., "Automatically Switched Optical Network (ASON)
              Routing for OSPFv2 Protocols", RFC 6827,
              DOI 10.17487/RFC6827, January 2013,

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Authors' Addresses

   Anton Smirnov
   Cisco Systems, Inc.
   De kleetlaan 6a
   Diegem  1831


   Alvaro Retana
   Huawei R&D USA
   2330 Central Expressway
   Santa Clara, CA  95050


   Michael Barnes
   Cisco Systems, Inc.
   510 McCarthy Blvd.
   Milpitas, CA  95035


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