Internet Engineering Task Force (IETF)                     A. Malis, Ed.
Request for Comments: 6827                        Verizon Communications
Obsoletes: 5787                                           A. Lindem, Ed.
Updates: 5786                                                   Ericsson
Category: Standards Track                          D. Papadimitriou, Ed.
ISSN: 2070-1721                                           Alcatel-Lucent
                                                            January 2013

Automatically Switched Optical Network (ASON)
Routing for OSPFv2 Protocols

Abstract

   The ITU-T has defined an architecture and requirements for operating
   an Automatically Switched Optical Network (ASON).

   The Generalized Multiprotocol Label Switching (GMPLS) protocol suite
   is designed to provide a control plane for a range of network
   technologies.  These include optical networks such as time division
   multiplexing (TDM) networks including the Synchronous Optical
   Network/Synchronous Digital Hierarchy (SONET/SDH), Optical Transport
   Networks (OTNs), and lambda switching optical networks.

   The requirements for GMPLS routing to satisfy the requirements of
   ASON routing and an evaluation of existing GMPLS routing protocols
   are provided in other documents.  This document defines extensions to
   the OSPFv2 Link State Routing Protocol to meet the requirements for
   routing in an ASON.

   Note that this work is scoped to the requirements and evaluation
   expressed in RFC 4258 and RFC 4652 and the ITU-T Recommendations that
   were current when those documents were written.  Future extensions or
   revisions of this work may be necessary if the ITU-T Recommendations
   are revised or if new requirements are introduced into a revision of
   RFC 4258.  This document obsoletes RFC 5787 and updates RFC 5786.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6827.

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.

   1. Introduction ....................................................4
      1.1. Conventions Used in This Document ..........................5
   2. Routing Areas, OSPF Areas, and Protocol Instances ...............5
   3. Terminology and Identification ..................................6
   4. Reachability ....................................................7
   5. Link Attribute ..................................................8
      5.1. Local Adaptation ...........................................8
      5.2. Bandwidth Accounting .......................................9
   6. Routing Information Scope .......................................9
      6.1. Link Advertisement (Local and Remote TE Router ID Sub-TLV) .9
      6.2. Reachability Advertisement (Local TE Router ID Sub-TLV) ...11
   7. Routing Information Dissemination ..............................11
      7.1. Import/Export Rules .......................................12
      7.2. Loop Prevention ...........................................12
           7.2.1. Inter-RA Export Upward/Downward Sub-TLVs ...........13
           7.2.2. Inter-RA Export Upward/Downward Sub-TLV Processing .13
   8. OSPFv2 Scalability .............................................14
   9. Security Considerations ........................................15
   10. IANA Considerations ...........................................15
      10.1. Sub-TLVs of the Link TLV .................................15
      10.2. Sub-TLVs of the Node Attribute TLV .......................16
      10.3. Sub-TLVs of the Router Address TLV .......................16
   11. Management Considerations .....................................17
      11.1. Routing Area (RA) Isolation ..............................17
      11.2. Routing Area (RA) Topology/Configuration Changes .........17
   12. Comparison to Requirements in RFC 4258 ........................17
   13. References ....................................................25
      13.1. Normative References .....................................25
      13.2. Informative References ...................................25
   14. Acknowledgements ..............................................26
      14.1. RFC 5787 Acknowledgements ................................26
   Appendix A. ASON Terminology ......................................27
   Appendix B. ASON Routing Terminology ..............................28
   Appendix C. Changes from RFC 5787 .................................29

1. Introduction

   The Generalized Multiprotocol Label Switching (GMPLS) [RFC3945]
   protocol suite is designed to provide a control plane for a range of
   network technologies.  These include optical networks such as time
   division multiplexing (TDM) networks including SONET/SDH, Optical
   Transport Networks (OTNs), and lambda switching optical networks.

   The ITU-T defines the architecture of the Automatically Switched
   Optical Network (ASON) in [G.8080].

   [RFC4258] describes the routing requirements for the GMPLS suite of
   routing protocols to support the capabilities and functionality of
   ASON control planes identified in [G.7715] and in [G.7715.1].

   [RFC4652] evaluates the IETF Link State routing protocols against the
   requirements identified in [RFC4258].  Section 7.1 of [RFC4652]
   summarizes the capabilities to be provided by OSPFv2 [RFC2328] in
   support of ASON routing.  This document describes the OSPFv2
   specifics for ASON routing.

   Multi-layer transport networks are constructed from multiple networks
   of different technologies operating in a client-server relationship.
   The ASON routing model includes the definition of routing levels that
   provide scaling and confidentiality benefits.  In multi-level
   routing, domains called routing areas (RAs) are arranged in a
   hierarchical relationship.  Note that as described in [RFC4652],
   there is no implied relationship between multi-layer transport
   networks and multi-level routing.  The multi-level routing mechanisms
   described in this document work for both single-layer and multi-layer
   networks.

   Implementations may support a hierarchical routing topology (multi-
   level) for multiple transport network layers and/or a hierarchical
   routing topology for a single transport network layer.

   This document describes the processing of the generic (technology-
   independent) link attributes that are defined in [RFC3630],
   [RFC4202], and [RFC4203] and that are extended in this document.  As
   described in Section 5.2, technology-specific traffic engineering
   attributes and their processing may be defined in other documents
   that complement this document.

   Note that this work is scoped to the requirements and evaluation
   expressed in [RFC4258] and [RFC4652] and the ITU-T Recommendations
   that were current when those documents were written.  Future
   extensions or revisions of this work may be necessary if the ITU-T
   Recommendations are revised or if new requirements are introduced
   into a revision of [RFC4258].

1.1. Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

   The reader is assumed to be familiar with the terminology and
   requirements developed in [RFC4258] and the evaluation outcomes
   described in [RFC4652].

   General ASON terminology is provided in Appendix A.  ASON routing
   terminology is described in Appendix B.

2. Routing Areas, OSPF Areas, and Protocol Instances

   An ASON routing area (RA) represents a partition of the transport
   plane, and its identifier is used within the control plane as the
   representation of this partition.

   RAs are hierarchically contained: a higher-level (parent) RA contains
   lower-level (child) RAs that in turn MAY also contain RAs.  Thus, RAs
   contain RAs that recursively define successive hierarchical RA
   levels.  Routing information may be exchanged between levels of the
   RA hierarchy, i.e., Level N+1 and N, where Level N represents the RAs
   contained by Level N+1.  The links connecting RAs may be viewed as
   external links (inter-RA links), and the links representing
   connectivity within an RA may be viewed as internal links (intra-RA
   links).  The external links to an RA at one level of the hierarchy
   may be internal links in the parent RA.  Intra-RA links of a child RA
   MAY be hidden from the parent RA's view [RFC4258].

   An ASON RA can be mapped to an OSPF area, but the hierarchy of ASON
   RA levels does not map to the hierarchy of OSPF areas.  Instead,
   successive hierarchical levels of RAs MUST be represented by separate
   instances of the protocol.  Thus, inter-level routing information
   exchange (as described in Section 7) involves the export and import
   of routing information between protocol instances.

   An ASON RA may therefore be identified by the combination of its OSPF
   Instance ID and its OSPF Area ID.  With proper and careful network-
   wide configuration, this can be achieved using just the OSPF Area ID,
   and this process is RECOMMENDED in this document.  These concepts are
   discussed in Section 7.

   A key ASON requirement is the support of multiple transport planes or
   layers.  Each transport node has associated topology (links and
   reachability), which is used for ASON routing.

3. Terminology and Identification

   This section describes the mapping of key ASON entities to OSPF
   entities.  Appendix A contains a complete glossary of ASON routing
   terminology.

   There are three categories of identifiers used for ASON routing
   (G.7715.1): transport-plane names, control-plane identifiers for
   components, and Signaling Communications Network (SCN) addresses.
   This section discusses the mapping between ASON routing identifiers
   and corresponding identifiers defined for GMPLS routing and how these
   support the physical (or logical) separation of transport-plane
   entities and control-plane components.  GMPLS supports this
   separation of identifiers and planes.

   In the context of OSPF Traffic Engineering (TE), an ASON transport
   node corresponds to a unique OSPF TE node.  An OSPF TE node is
   uniquely identified by the TE Router Address TLV [RFC3630].  In this
   document, the TE Router Address is referred to as the TE Router ID.
   In GMPLS, TE router addresses are advertised as reachable in both the
   control and transport planes, see Section 4 below.  Furthermore, the
   TE Router ID should not be confused with the OSPF Router ID that
   uniquely identifies an OSPF router within an OSPF routing domain
   [RFC2328] and is in a name space for control-plane components.

   The Router Address top-level TLV definition, processing, and usage
   are largely unchanged from [RFC3630].  This TLV specifies a stable
   OSPF TE node IP address, i.e., the IP address is always reachable
   when there is IP connectivity to the associated OSPF TE node.

   ASON defines a Routing Controller (RC) as an entity that handles
   (abstract) information needed for routing and the routing information
   exchange with peering RCs by operating on the Routing Database (RDB).
   ASON defines a Protocol Controller (PC) as an entity that handles
   protocol-specific message exchanges according to the reference point
   over which the information is exchanged (e.g., E-NNI, I-NNI) and
   internal exchanges with the RC [RFC4258].  In this document, an OSPF
   router advertising ASON TE topology information will perform both the

   functions of the RC and PC.  The OSPF routing domain comprises the
   control plane, and each OSPF router is uniquely identified by its
   OSPF Router ID [RFC2328].

4. Reachability

   In ASON, reachability information describes the set of endpoints that
   are reachable by the associated node in the transport plane.
   Reachability information represents transport-plane resources, e.g.,
   an optical cross-connect interface, and uses transport-plane
   identifiers.

   In order to advertise blocks of reachable address prefixes, a
   summarization mechanism is introduced that is based on the techniques
   described in [RFC5786].  For ASON reachability advertisement, blocks
   of reachable address prefixes are advertised together with the
   associated transport-plane node.  The transport-plane node is
   identified in OSPF TE Link State Advertisements (LSAs) by its TE
   Router ID, as discussed in Section 6.

   In order to support ASON reachability advertisement, the Node
   Attribute TLV defined in [RFC5786] is used to advertise the
   combination of a TE Router ID and its set of associated reachable
   address prefixes.  The Node Attribute TLV can contain the following
   sub-TLVs:

      - Local TE Router ID sub-TLV: Length: 4; Defined in Section 6.2
      - Node IPv4 Local Address sub-TLV: Length: variable; [RFC5786]
      - Node IPv6 Local Address sub-TLV: Length: variable; [RFC5786]

   A router may support multiple transport nodes as discussed in
   Section 6 and, as a result, may be required to advertise reachability
   separately for each transport node.  As a consequence, it MUST be
   possible for the router to originate more than one TE LSA containing
   the Node Attribute TLV when used for ASON reachability advertisement.

   Hence, the Node Attribute TLV [RFC5786] advertisement rules are
   relaxed.  A Node Attribute TLV MAY appear in more than one TE LSA
   originated by the RC when the RC is advertising reachability
   information for a different transport node identified by the Local TE
   Router sub-TLV (refer to Section 6.2).

   As specified in [RFC3630], TE-advertised router addresses are also
   advertised as reachable in the control plane and are therefore also
   valid identifiers in the ASON SCN name space.

5. Link Attribute

   With the exception of local adaptation (described below), the mapping
   of link attributes and characteristics to OSPF TE Link TLV sub-TLVs
   is unchanged [RFC4652].  OSPF TE Link TLV sub-TLVs are described in
   [RFC3630] and [RFC4203].  Advertisement of this information SHOULD be
   supported on a per-layer basis, i.e., one TE LSA per unique switching
   capability and bandwidth granularity combination.

5.1. Local Adaptation

   Local adaptation is defined as a TE link attribute (i.e., sub-TLV)
   that describes the cross/inter-layer relationships.

   The Interface Switching Capability Descriptor (ISCD) TE Attribute
   [RFC4202] identifies the ability of the TE link to support cross-
   connection to another link within the same layer.  When advertising
   link adaptation, it also identifies the ability to use a locally
   terminated connection that belongs to one layer as a data link for
   another layer (adaptation capability).  However, the information
   associated with the ability to terminate connections within that
   layer (referred to as the termination capability) is advertised with
   the adaptation capability.

   For instance, a link between two optical cross-connects will contain
   at least one ISCD attribute describing the Lambda Switching Capable
   (LSC) switching capability.  Conversely, a link between an optical
   cross-connect and an IP/MPLS Label Switching Router (LSR) will
   contain at least two ISCD attributes, one for the description of the
   LSC termination capability and one for the Packet Switching Capable
   (PSC) adaptation capability.

   In OSPFv2, the Interface Switching Capability Descriptor (ISCD) is a
   sub-TLV (type 15) of the top-level Link TLV (type 2) [RFC4203].  The
   adaptation and termination capabilities are advertised using two
   separate ISCD sub-TLVs within the same top-level Link TLV.

   An interface MAY have more than one ISCD sub-TLV, per [RFC4202] and
   [RFC4203].  Hence, the corresponding advertisements should not result
   in any compatibility issues.

5.2. Bandwidth Accounting

   GMPLS routing defines an ISCD that provides, among other things, the
   quantities of the maximum/minimum available bandwidth per priority
   for Label Switched Paths (LSPs).  One or more ISCD sub-TLVs can be
   associated with an interface, per [RFC4202] and [RFC4203].  This
   information, combined with the Unreserved Bandwidth Link TLV sub-TLV
   [RFC3630], provides the basis for bandwidth accounting.

   In the ASON context, additional information may be included when the
   representation and information in the other advertised fields are not
   sufficient for a specific technology, e.g., SDH.  The definition of
   technology-specific information elements is beyond the scope of this
   document.  Some technologies will not require additional information
   beyond what is already defined in [RFC3630], [RFC4202], and
   [RFC4203].

6. Routing Information Scope

   For ASON routing, the control-plane component routing adjacency
   topology (i.e., the associated Protocol Controller (PC) connectivity)
   and the transport topology are not assumed to be congruent [RFC4258].
   Hence, a single OSPF router (i.e., the PC) MUST be able to advertise
   on behalf of multiple transport-layer nodes.  The OSPF routers are
   identified by OSPF Router ID, and the transport nodes are identified
   by TE Router ID.

   The Router Address TLV [RFC3630] is used to advertise the TE Router
   ID associated with the advertising Routing Controller (RC).  TE
   Router IDs for additional transport nodes are advertised through
   specification of the Local TE Router Identifier in the Local and
   Remote TE Router TE sub-TLV and the Local TE Router Identifier
   sub-TLV described in the sections below.  These Local TE Router
   Identifiers are typically used as the local endpoints for TE LSPs
   terminating on the associated transport node.

   The use of multiple OSPF Routers to advertise TE information for the
   same transport node is not considered a required use case and is not
   discussed further in this document.

6.1. Link Advertisement (Local and Remote TE Router ID Sub-TLV)

   When an OSPF Router advertises on behalf of multiple transport nodes,
   the link endpoints cannot be automatically assigned to a single
   transport node associated with the advertising router.  In this case,
   the local and remote transport nodes MUST be identified by TE Router
   ID to unambiguously specify the transport topology.

   For this purpose, a new sub-TLV of the OSPFv2 TE LSA top-level Link
   TLV is introduced that defines the Local and Remote TE Router ID.

   The Type field of the Local and Remote TE Router ID sub-TLV is
   assigned the value 10 (see Section 10).  The Length field takes the
   value 8.  The Value field of this sub-TLV contains 4 octets of the
   Local TE Router Identifier followed by 4 octets of the Remote TE
   Router Identifier.  The value of the Local and Remote TE Router
   Identifier MUST NOT be set to 0.

   The format of the Local and Remote TE Router ID sub-TLV is:

    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 (10)           |          Length (8)           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Local TE Router Identifier                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Remote TE Router Identifier                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This sub-TLV MUST be included as a sub-TLV of the top-level Link TLV
   if the OSPF router is advertising on behalf of one or more transport
   nodes having TE Router IDs different from the TE Router ID advertised
   in the Router Address TLV.  For consistency, this sub-TLV MUST be
   included when OSPF is used for the advertisement of ASON information
   as described herein.  If it is not included in a Link TLV, or if a
   value of 0 is specified for the Local or Remote TE Router Identifier,
   the Link TLV will not be used for transport-plane path computation.
   Additionally, the condition SHOULD be logged for possible action by
   the network operator.

   Note: The Link ID sub-TLV identifies the other end of the link (i.e.,
   Router ID of the neighbor for point-to-point links) [RFC3630].  When
   the Local and Remote TE Router ID sub-TLV is present, it MUST be used
   to identify local and remote transport node endpoints for the link
   and the Link-ID sub-TLV MUST be ignored.  In fact, when the Local and
   Remote TE Router ID sub-TLV is specified, the Link-ID sub-TLV MAY be
   omitted.  The Local and Remote TE Router ID sub-TLV, if specified,
   MUST only be specified once.  If specified more than once, instances
   other than the first will be ignored and the condition SHOULD be
   logged for possible action by the network operator.

6.2. Reachability Advertisement (Local TE Router ID Sub-TLV)

   When an OSPF router is advertising on behalf of multiple transport
   nodes, the routing protocol MUST be able to associate the advertised
   reachability information with the correct transport node.

   For this purpose, a new sub-TLV of the OSPFv2 TE LSA top-level Node
   Attribute TLV is introduced.  This TLV associates the local prefixes
   (see above) to a given transport node identified by the TE Router ID.

   The Type field of the Local TE Router ID sub-TLV is assigned the
   value 5 (see Section 10).  The Length field takes the value 4.  The
   Value field of this sub-TLV contains the Local TE Router Identifier
   encoded over 4 octets.

   The format of the Local TE Router ID sub-TLV is:

    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 (5)          |          Length (4)           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Local TE Router Identifier                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This sub-TLV MUST be included as a sub-TLV of the top-level Node
   Attribute TLV if the OSPF router is advertising on behalf of one or
   more transport nodes having TE Router IDs different from the TE
   Router ID advertised in the Router Address TLV.  For consistency,
   this sub-TLV MUST be included when OSPF is used for the advertisement
   of ASON information as described herein.  If it is not included in a
   Node Attribute TLV, or if a value of 0 is specified for the Local TE
   Router Identifier, the Note Attribute TLV will not be used for
   determining ASON SCN reachability.  Additionally, the condition
   SHOULD be logged for possible action by the network operator.

7. Routing Information Dissemination

   An ASON routing area (RA) represents a partition of the transport
   plane, and its identifier is used within the control plane as the
   representation of this partition.  An RA may contain smaller RAs
   inter-connected by links.  ASON RA levels do not map directly to OSPF
   areas.  Rather, hierarchical levels of RAs are represented by
   separate OSPF protocol instances.  However, it is useful to align the
   RA IDs and area ID in order to facilitate isolation of RAs as
   described in Section 11.1.

   Routing Controllers (RCs) supporting multiple RAs disseminate
   information downward and upward in this ASON hierarchy.  The vertical
   routing information dissemination mechanisms described in this
   section do not introduce or imply hierarchical OSPF areas.  RCs
   supporting RAs at multiple levels are structured as separate OSPF
   instances with routing information exchange between levels described
   by import and export rules between these instances.  The
   functionality described herein does not pertain to OSPF areas or OSPF
   Area Border Router (ABR) functionality.

7.1. Import/Export Rules

   RCs supporting RAs disseminate information upward and downward in the
   hierarchy by importing/exporting routing information as TE LSAs.  TE
   LSAs are area-scoped Opaque LSAs with Opaque type 1 [RFC3630].  The
   information that MAY be exchanged between adjacent levels includes
   the Router Address, Link, and Node Attribute top-level TLVs.

   The imported/exported routing information content MAY be transformed,
   e.g., filtered or aggregated, as long as the resulting routing
   information is consistent.  In particular, when more than one RC is
   bound to adjacent levels and both are allowed to import/export
   routing information, it is expected that these transformations are
   performed in a consistent manner.  Definition of these policy-based
   mechanisms are outside the scope of this document.

   In practice, and in order to avoid scalability and processing
   overhead, routing information imported/exported downward/upward in
   the hierarchy is expected to include reachability information (see
   Section 4) and, upon strict policy control, link topology
   information.

7.2. Loop Prevention

   When more than one RC is bound to an adjacent level of the ASON
   hierarchy and is configured to export routing information upward or
   downward, a specific mechanism is required to avoid looping of
   routing information.  Looping is the re-advertisement of routing
   information into an RA that had previously advertised that routing
   information upward or downward into an upper or lower level RA in the
   ASON hierarchy.  For example, without loop-prevention mechanisms,
   this could happen when the RC advertising routing information
   downward in the hierarchy is not the same one that advertises routing
   information upward in the hierarchy.

7.2.1. Inter-RA Export Upward/Downward Sub-TLVs

   The Inter-RA Export sub-TLVs can be used to prevent the
   re-advertisement of OSPF TE routing information into an RA that
   previously advertised that information.  The type value 13 (see
   Section 10) will indicate that the associated routing information has
   been exported downward.  The type value 12 (see Section 10) will
   indicate that the associated routing information has been exported
   upward.  While it is not required for routing information exported
   downward, both sub-TLVs will include the Routing Area (RA) ID from
   which the routing information was exported.  This RA is not
   necessarily the RA originating the routing information but the RA
   from which the information was immediately exported.

   These additional sub-TLVs MAY be included in TE LSAs that include any
   of the following top-level TLVs:

      - Router Address top-level TLV
      - Link top-level TLV
      - Node Attribute top-level TLV

   The Type field of the Inter-RA Export Upward and Inter-RA Export
   Downward sub-TLVs are respectively assigned the values 12 and 13 (see
   Section 10).  The Length field in these sub-TLVs takes the value 4.
   The Value field in these sub-TLVs contains the associated RA ID.  The
   RA ID value must be a unique identifier for the RA within the ASON
   routing domain.

   The format of the Inter-RA Export Upward and Inter-RA Export Downward
   sub-TLVs is graphically depicted below:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Upward/Downward Type    |           Length (4)          |
   |             (12/13)           |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Associated RA ID                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

7.2.2. Inter-RA Export Upward/Downward Sub-TLV Processing

   TE LSAs MAY be imported or exported downward or upward in the ASON
   routing hierarchy.  The direction and advertising RA ID are
   advertised in an Inter-RA Export Upward/Downward sub-TLV.  They MUST
   be retained and advertised in the receiving RA with the associated
   routing information.

   When exporting routing information upward in the ASON routing
   hierarchy, any information received from a level above, i.e., tagged
   with an Inter-RA Export Downward sub-TLV, MUST NOT be exported
   upward.  Since an RA at Level N is contained by a single RA at
   Level N+1, this is the only checking that is necessary and the
   associated RA ID is used solely for informational purposes.

   When exporting routing information downward in the ASON routing
   hierarchy, any information received from a level below, i.e., tagged
   with an Inter-RA Export Upward sub-TLV, MUST NOT be exported downward
   if the target RA ID matches the RA ID associated with the routing
   information.  This additional checking is required for routing
   information exported downward since a single RA at Level N+1 may
   contain multiple RAs at Level N in the ASON routing hierarchy.  In
   other words, routing information MUST NOT be exported downward into
   the RA from which it was received.

8. OSPFv2 Scalability

   The extensions described herein are only applicable to ASON routing
   domains, and it is not expected that the attendant reachability (see
   Section 4) and link information will ever be combined with global
   Internet or Layer 3 Virtual Private Network (VPN) routing.  If there
   were ever a requirement for a given RC to participate in both
   domains, separate OSPFv2 instances would be utilized.  However, in a
   multi-level ASON hierarchy, the potential volume of information could
   be quite large and the recommendations in this section MUST be
   followed by RCs implementing this specification.

   - Routing information exchange upward/downward in the hierarchy
     between adjacent RAs MUST, by default, be limited to reachability
     information.  In addition, several transformations such as prefix
     aggregation are RECOMMENDED to reduce the amount of information
     imported/exported by a given RC when such transformations will not
     impact consistency.

   - Routing information exchange upward/downward in the ASON hierarchy
     involving TE attributes MUST be under strict policy control.
     Pacing and min/max thresholds for triggered updates are strongly
     RECOMMENDED.

   - The number of routing levels MUST be maintained under strict policy
     control.

9. Security Considerations

   This document specifies the contents and processing of OSPFv2 TE LSAs
   [RFC3630] and [RFC4202].  The TE LSA extensions defined in this
   document are not used for Shortest Path First (SPF) computation and
   have no direct effect on IP routing.  Additionally, ASON routing
   domains are delimited by the usual administrative domain boundaries.

   Any mechanisms used for securing the exchange of normal OSPF LSAs can
   be applied equally to all TE LSAs used in the ASON context.
   Authentication of OSPFv2 LSA exchanges (such as OSPF cryptographic
   authentication [RFC2328] [RFC5709]) can be used to provide
   significant protection against active attacks.  [RFC5709] defines a
   mechanism for authenticating OSPFv2 packets by making use of the
   Hashed Message Authentication Code (HMAC) algorithm in conjunction
   with the SHA family of cryptographic hash functions.

   RCs implementing export/import of ASON routing information between
   RAs MUST also include policy control of both the maximum amount of
   information advertised between RAs and the maximum rate at which it
   is advertised.  This is to isolate the consequences of an RC being
   compromised to the RAs to which that subverted RC is attached.

   The "Analysis of OSPF Security According to KARP Design Guide"
   [OSPF-SEC] provides a comprehensive analysis of OSPFv2 and OSPFv3
   security relative to the requirements specified in [RFC6518].

10. IANA Considerations

   This document defines new sub-TLVs for inclusion in OSPF TE LSAs.
   IANA has assigned values per the assignment policies for the
   registries of code points for these sub-TLVs [RFC3630].

   The following subsections summarize the required sub-TLVs.

10.1. Sub-TLVs of the Link TLV

   This document defines the following sub-TLVs of the Link TLV
   advertised in the OSPF TE LSA:

   -  Local and Remote TE Router ID sub-TLV (10)
   -  Inter-RA Export Upward sub-TLV (12)
   -  Inter-RA Export Downward sub-TLV (13)

   Codepoints for these sub-TLVs have been allocated in the Standards
   Action range of the "Types for sub-TLVs of TE Link TLV (Value 2)"
   registry [RFC3630].

   Note that the same values for the Inter-RA Export Upward sub-TLV and
   the Inter-RA Export Downward sub-TLV MUST be used when they appear in
   the Link TLV, Node Attribute TLV, and Router Address TLV.

10.2. Sub-TLVs of the Node Attribute TLV

   This document defines the following sub-TLVs of the Node Attribute
   TLV advertised in the OSPF TE LSA:

      - Local TE Router ID sub-TLV (5)
      - Inter-RA Export Upward sub-TLV (12)
      - Inter-RA Export Downward sub-TLV (13)

   Codepoints for these sub-TLVs have been assigned in Standards Action
   range of the "Types for sub-TLVs of TE Node Attribute TLV (Value 5)"
   [RFC5786].

   Note that the same values for the Inter-RA Export Upward sub-TLV and
   the Inter-RA Export Downward sub-TLV MUST be used when they appear in
   the Link TLV, Node Attribute TLV, and Router Address TLV.

10.3. Sub-TLVs of the Router Address TLV

   The Router Address TLV is advertised in the OSPF TE LSA [RFC3630].
   Since the TLV had no sub-TLVs defined, a "Types for sub-TLVs of
   Router Address TLV (Value 1)" registry has been defined.

   The registry guidelines for the assignment of types for sub-TLVs of
   the Router Address TLV are as follows:

      o  Types in the range 0-32767 are to be assigned via Standards
         Action.

      o  Type 0 in the aforementioned Standards Action range (0-32767)
         is reserved.

      o  Types in the range 32768-32777 are for experimental use; these
         will not be registered with IANA and MUST NOT be mentioned by
         RFCs.

      o  Types in the range 32778-65535 are not to be assigned at this
         time.  Before any assignments can be made in this range, there
         MUST be a Standards Track RFC that specifies IANA
         Considerations that covers the range being assigned.

   This document defines the following sub-TLVs for inclusion in the
   Router Address TLV:

      - Inter-RA Export Upward sub-TLV (12)
      - Inter-RA Export Downward sub-TLV (13)

   Codepoints for these sub-TLVs have been allocated in the Standards
   Action range of the "Types for sub-TLVs of Router Address TLV
   (Value 1)" registry.

   Note that the same values for the Inter-RA Export Upward sub-TLV and
   the Inter-RA Export Downward sub-TLV MUST be used when they appear in
   the Link TLV, Node Attribute TLV, and Router Address TLV.

11. Management Considerations

11.1. Routing Area (RA) Isolation

   If the RA ID is mapped to the OSPF Area ID as recommended in
   Section 2, OSPF [RFC2328] implicitly provides isolation.  On any
   intra-RA link, packets will only be accepted if the area ID in the
   OSPF packet header matches the area ID for the OSPF interface on
   which the packet was received.  Hence, RCs will only establish
   adjacencies and exchange reachability information (see Section 4.0)
   with RCs in the same RA.  Other mechanisms for RA isolation are
   beyond the scope of this document.

11.2. Routing Area (RA) Topology/Configuration Changes

   The GMPLS Routing for ASON requirements [RFC4258] dictate that the
   routing protocol MUST support reconfiguration and SHOULD support
   architectural evolution.  OSPF [RFC2328] includes support for the
   dynamic introduction or removal of ASON reachability information
   through the flooding and purging of OSPF Opaque LSAs [RFC5250].
   Also, when an RA is partitioned or an RC fails, stale LSAs SHOULD NOT
   be used unless the advertising RC is reachable.  The configuration of
   OSPF RAs and the policies governing the redistribution of ASON
   reachability information between RAs are implementation issues
   outside of the OSPF routing protocol and beyond the scope of this
   document.

12. Comparison to Requirements in RFC 4258

   The following table shows how this document complies with the
   requirements in [RFC4258].  The first column contains a requirements
   number (1-30) and the relevant section in RFC 4258.  The second
   column describes the requirement, the third column discusses the

   compliance to that requirement, and the fourth column lists the
   relevant section in this document and/or another RFC that already
   satisfies the requirement.

13. References

13.1. Normative References

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

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

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

   [RFC3945]    Mannie, E., Ed., "Generalized Multi-Protocol Label
                Switching (GMPLS) Architecture", RFC 3945, October 2004.

   [RFC4202]    Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
                Extensions in Support of Generalized Multi-Protocol
                Label Switching (GMPLS)", RFC 4202, October 2005.

   [RFC4203]    Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions
                in Support of Generalized Multi-Protocol Label Switching
                (GMPLS)", RFC 4203, October 2005.

   [RFC5250]    Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
                OSPF Opaque LSA Option", RFC 5250, July 2008.

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

13.2. Informative References

   [RFC4258]    Brungard, D., Ed., "Requirements for Generalized Multi-
                Protocol Label Switching (GMPLS) Routing for the
                Automatically Switched Optical Network (ASON)",
                RFC 4258, November 2005.

   [RFC4652]    Papadimitriou, D., Ed., Ong, L., Sadler, J., Shew, S.,
                and D. Ward, "Evaluation of Existing Routing Protocols
                against Automatic Switched Optical Network (ASON)
                Routing Requirements", RFC 4652, October 2006.

   [RFC5709]    Bhatia, M., Manral, V., Fanto, M., White, R., Barnes,
                M., Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA
                Cryptographic Authentication", RFC 5709, October 2009.

   [RFC6518]    Lebovitz, G. and M. Bhatia, "Keying and Authentication
                for Routing Protocols (KARP) Design Guidelines",
                RFC 6518, February 2012.

   [OSPF-SEC]   Hartman, S. and Zhang, D., "Analysis of OSPF Security
                According to KARP Design Guide", Work in Progress,
                November 2012.

   [G.7715]     ITU-T Rec. G.7715/Y.1706, "Architecture and Requirements
                in the Automatically Switched Optical Network",
                June 2002.

   [G.7715.1]   ITU-T Rec. G.7715.1/Y.1706.1, "ASON Routing Architecture
                and Requirements for Link State Protocols",
                February 2004.

   [G.805]      ITU-T Rec. G.805, "Generic Functional Architecture of
                Transport Networks)", March 2000.

   [G.8080]     ITU-T Rec. G.8080/Y.1304, "Architecture for the
                automatically switched optical network", February 2012.

14. Acknowledgements

   The editors would like to thank Lyndon Ong, Remi Theillaud, Stephen
   Shew, Jonathan Sadler, Deborah Brungard, Lou Berger, and Adrian
   Farrel for their useful comments and suggestions.

14.1. RFC 5787 Acknowledgements

   The author would like to thank Dean Cheng, Acee Lindem, Pandian
   Vijay, Alan Davey, Adrian Farrel, Deborah Brungard, and Ben Campbell
   for their useful comments and suggestions.

   Lisa Dusseault and Jari Arkko provided useful comments during IESG
   review.

   Question 14 of Study Group 15 of the ITU-T provided useful and
   constructive input.

Appendix A. ASON Terminology

   This document makes use of the following terms:

   Administrative domain: (See Recommendation [G.805].)  For the
      purposes of [G.7715.1], an administrative domain represents the
      extent of resources that belong to a single player such as a
      network operator, a service provider, or an end-user.
      Administrative domains of different players do not overlap amongst
      themselves.

   Control plane: performs the call control and connection control
      functions.  Through signaling, the control plane sets up and
      releases connections and may restore a connection in case of a
      failure.

   (Control) Domain: represents a collection of (control) entities that
      are grouped for a particular purpose.  The control plane is
      subdivided into domains matching administrative domains.  Within
      an administrative domain, further subdivisions of the control
      plane are recursively applied.  A routing control domain is an
      abstract entity that hides the details of the RC distribution.

   External NNI (E-NNI): interfaces located between protocol controllers
      between control domains.

   Internal NNI (I-NNI): interfaces located between protocol controllers
      within control domains.

   Link: (See Recommendation G.805.)  A "topological component" that
      describes a fixed relationship between a "subnetwork" or "access
      group" and another "subnetwork" or "access group".  Links are not
      limited to being provided by a single server trail.

   Management plane: performs management functions for the transport
      plane, the control plane, and the system as a whole.  It also
      provides coordination between all the planes.  The following
      management functional areas are performed in the management plane:
      performance, fault, configuration, accounting, and security
      management.

   Management domain: (See Recommendation G.805.)  A management domain
      defines a collection of managed objects that are grouped to meet
      organizational requirements according to geography, technology,
      policy, or other structure, and for a number of functional areas
      such as Fault, Configuration, Accounting, Performance, and
      Security (FCAPS), for the purpose of providing control in a
      consistent manner.  Management domains can be disjoint, contained,

      or overlapping.  As such, the resources within an administrative
      domain can be distributed into several possible overlapping
      management domains.  The same resource can therefore belong to
      several management domains simultaneously, but a management domain
      shall not cross the border of an administrative domain.

   Subnetwork Point (SNP): The SNP is a control-plane abstraction that
      represents an actual or potential transport-plane resource.  SNPs
      (in different subnetwork partitions) may represent the same
      transport resource.  A one-to-one correspondence should not be
      assumed.

   Subnetwork Point Pool (SNPP): A set of SNPs that are grouped together
      for the purposes of routing.

   Termination Connection Point (TCP): A TCP represents the output of a
      Trail Termination function or the input to a Trail Termination
      Sink function.

   Transport plane: provides bidirectional or unidirectional transfer of
      user information, from one location to another.  It can also
      provide transfer of some control and network management
      information.  The transport plane is layered; it is equivalent to
      the Transport Network defined in Recommendation G.805.

   User Network Interface (UNI): interfaces are located between protocol
      controllers between a user and a control domain.  Note: There is
      no routing function associated with a UNI reference point.

Appendix B. ASON Routing Terminology

   This document makes use of the following terms:

   Routing Area (RA): an RA represents a partition of the transport
      plane, and its identifier is used within the control plane as the
      representation of this partition.  Per [G.8080], an RA is defined
      by a set of subnetworks, the links that interconnect them, and the
      interfaces representing the ends of the links exiting that RA.  An
      RA may contain smaller RAs inter-connected by links.  The limit of
      subdivision results in an RA that contains two subnetworks
      interconnected by a single link.

   Routing Database (RDB): a repository for the local topology, network
      topology, reachability, and other routing information that is
      updated as part of the routing information exchange and may
      additionally contain information that is configured.  The RDB may
      contain routing information for more than one routing area (RA).

   Routing Components: ASON routing architecture functions.  These
      functions can be classified as protocol independent (Link Resource
      Manager (LRM), Routing Controller (RC)) or protocol specific
      (Protocol Controller (PC)).

   Routing Controller (RC): handles (abstract) information needed for
      routing and the routing information exchange with peering RCs by
      operating on the RDB.  The RC has access to a view of the RDB.
      The RC is protocol independent.

   Note: Since the RDB may contain routing information pertaining to
      multiple RAs (and possibly to multiple layer networks), the RCs
      accessing the RDB may share the routing information.

   Link Resource Manager (LRM): supplies all the relevant component and
      TE link information to the RC.  It informs the RC about any state
      changes of the link resources it controls.

   Protocol Controller (PC): handles protocol-specific message exchanges
      according to the reference point over which the information is
      exchanged (e.g., E-NNI, I-NNI) and internal exchanges with the RC.
      The PC function is protocol dependent.

Appendix C. Changes from RFC 5787

   This document contains the following changes from RFC 5787:

   1. This document will be on the Standards Track, rather than
      Experimental, and reflects experience gained from RFC 5787
      implementation and interoperability testing.  This also required
      changes to the IANA Considerations.

   2. There is a new Section 3 on Terminology and Identification to
      describe the mapping of key ASON entities to OSPF entities.

   3. Sections were reorganized to explain terminology before defining
      prefix extensions.

   4. There is a new Section 11, Management Considerations, which
      describes how existing OSPF mechanisms address ASON requirements
      on Routing Area changes.

   5. There is a new Section 12, which compares the document to the
      requirements in RFC 4258.

   6. The prefix format was changed to reference RFC 5786 rather than
      defining a separate format and The Node Attribute TLV in RFC 5786
      has been updated as a result.

7. Routing Information Advertisements were simplified from RFC 5787.

8. Review comments from ITU-T SG15 and the IESG were incorporated.

Authors' Addresses

   Andrew G. Malis
   Verizon Communications
   60 Sylvan Rd.
   Waltham, MA 02451 USA

   EMail: andrew.g.malis@verizon.com

   Acee Lindem
   Ericsson
   102 Carric Bend Court
   Cary, NC 27519

   EMail: acee.lindem@ericsson.com

   Dimitri Papadimitriou
   Alcatel-Lucent
   Copernicuslaan, 50
   2018 Antwerpen, Belgium

   EMail: dimitri.papadimitriou@alcatel-lucent.com