





Internet Engineering Task Force (IETF)                  D. Papadimitriou
Request for Comments: 6001                                  M. Vigoureux
Updates: 4202, 4203, 4206, 4874, 4974, 5307               Alcatel-Lucent
Category: Standards Track                                    K. Shiomoto
ISSN: 2070-1721                                                      NTT
                                                             D. Brungard
                                                                     ATT
                                                             JL. Le Roux
                                                          France Telecom
                                                            October 2010


              Generalized MPLS (GMPLS) Protocol Extensions
          for Multi-Layer and Multi-Region Networks (MLN/MRN)

Abstract

   There are specific requirements for the support of networks
   comprising Label Switching Routers (LSRs) participating in different
   data plane switching layers controlled by a single Generalized Multi-
   Protocol Label Switching (GMPLS) control plane instance, referred to
   as GMPLS Multi-Layer Networks / Multi-Region Networks (MLN/MRN).

   This document defines extensions to GMPLS routing and signaling
   protocols so as to support the operation of GMPLS Multi-Layer /
   Multi-Region Networks.  It covers the elements of a single GMPLS
   control plane instance controlling multiple Label Switched Path (LSP)
   regions or layers within a single Traffic Engineering (TE) domain.

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/rfc6001.









Papadimitriou, et al.        Standards Track                    [Page 1]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


Copyright Notice

   Copyright (c) 2010 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.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

























Papadimitriou, et al.        Standards Track                    [Page 2]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


Table of Contents

   1. Introduction ....................................................3
      1.1. Conventions Used in This Document ..........................4
   2. Summary of the Requirements and Evaluation ......................4
   3. Interface Adjustment Capability Descriptor (IACD) ...............5
      3.1. Overview ...................................................5
      3.2. Interface Adjustment Capability Descriptor (IACD) ..........6
   4. Multi-Region Signaling ..........................................9
      4.1. XRO Subobjects ............................................10
   5. Virtual TE Link ................................................12
      5.1. Edge-to-Edge Association ..................................13
      5.2. Soft Forwarding Adjacency (Soft FA) .......................16
   6. Backward Compatibility .........................................18
   7. Security Considerations ........................................18
   8. IANA Considerations ............................................18
      8.1. RSVP ......................................................18
      8.2. OSPF ......................................................20
      8.3. IS-IS .....................................................20
   9. References .....................................................20
      9.1. Normative References ......................................20
      9.2. Informative References ....................................22
   Acknowledgments....................................................23
   Contributors ......................................................23

1.  Introduction

   Generalized Multi-Protocol Label Switching (GMPLS) [RFC3945] extends
   MPLS to handle multiple switching technologies: packet switching
   (PSC), Layer 2 switching (L2SC), Time-Division Multiplexing (TDM)
   Switching, wavelength switching (LSC) and fiber switching (FSC).  A
   GMPLS switching type (PSC, TDM, etc.) describes the ability of a node
   to forward data of a particular data plane technology, and uniquely
   identifies a control plane LSP region.  LSP regions are defined in
   [RFC4206].  A network comprised of multiple switching types (e.g.,
   PSC and TDM) controlled by a single GMPLS control plane instance is
   called a Multi-Region Network (MRN).

   A data plane layer is a collection of network resources capable of
   terminating and/or switching data traffic of a particular format.
   For example, LSC, TDM VC-11, and TDM VC-4-64c represent three
   different layers.  A network comprising transport nodes participating
   in different data plane switching layers controlled by a single GMPLS
   control plane instance is called a Multi-Layer Network (MLN).







Papadimitriou, et al.        Standards Track                    [Page 3]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   The applicability of GMPLS to multiple switching technologies
   provides the unified control and operations for both LSP provisioning
   and recovery.  This document covers the elements of a single GMPLS
   control plane instance controlling multiple layers within a given TE
   domain.  A TE domain is defined as group of Label Switching Routers
   (LSRs) that enforces a common TE policy.  A Control Plane (CP)
   instance can serve one, two, or more layers.  Other possible
   approaches, such as having multiple CP instances serving disjoint
   sets of layers, are outside the scope of this document.

   The next sections provide the procedural aspects in terms of routing
   and signaling for such environments as well as the extensions
   required to instrument GMPLS to provide the capabilities for MLN/MRN
   unified control.  The rationales and requirements for Multi-
   Layer/Region networks are set forth in [RFC5212].  These requirements
   are evaluated against GMPLS protocols in [RFC5339] and several areas
   where GMPLS protocol extensions are required are identified.

   This document defines GMPLS routing and signaling extensions so as to
   cover GMPLS MLN/MRN requirements.

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 [RFC2119].

   In addition, the reader is assumed to be familiar with [RFC3945],
   [RFC3471], [RFC4201], [RFC4202], [RFC4203], [RFC4206], and [RFC5307].

2.  Summary of the Requirements and Evaluation

   As identified in [RFC5339], most MLN/MRN requirements rely on
   mechanisms and procedures (such as local procedures and policies, or
   specific TE mechanisms and algorithms) that are outside the scope of
   the GMPLS protocols, and thus do not require any GMPLS protocol
   extensions.

   Four areas for extensions of GMPLS protocols and procedures have been
   identified in [RFC5339]:

   o GMPLS routing extensions for the advertisement of the internal
     adjustment capability of hybrid nodes.  See Section 3.2.2 of
     [RFC5339].







Papadimitriou, et al.        Standards Track                    [Page 4]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   o GMPLS signaling extensions for constrained multi-region signaling
     (Switching Capability inclusion/exclusion).  See Section 3.2.1 of
     [RFC5339].  An additional eXclude Route Object (XRO) Label
     subobject is also defined since it was absent from [RFC4874].

   o GMPLS signaling extensions for the setup/deletion of virtual TE
     links (as well as exact trigger for its actual provisioning).  See
     Section 3.1.1.2 of [RFC5339].

   o GMPLS routing and signaling extensions for graceful TE link
     deletion.  See Section 3.1.1.3 of [RFC5339].

   The first three requirements are addressed in Sections 3, 4, and 5 of
   this document, respectively.  The fourth requirement is addressed in
   [RFC5710] with additional context provided by [RFC5817].

3.  Interface Adjustment Capability Descriptor (IACD)

   In the MRN context, nodes that have at least one interface that
   supports more than one switching capability are called hybrid nodes
   [RFC5212].  The logical composition of a hybrid node contains at
   least two distinct switching elements that are interconnected by
   "internal links" to provide adjustment between the supported
   switching capabilities.  These internal links have finite capacities
   that MUST be taken into account when computing the path of a multi-
   region TE-LSP.  The advertisement of the internal adjustment
   capability is required as it provides critical information when
   performing multi-region path computation.

3.1.  Overview

   In an MRN environment, some LSRs could contain multiple switching
   capabilities, such as PSC and TDM or PSC and LSC, all under the
   control of a single GMPLS instance.

   These nodes, hosting multiple Interface Switching Capabilities (ISCs)
   [RFC4202], are required to hold and advertise resource information on
   link states and topology, just like other nodes (hosting a single
   ISC).  They may also have to consider some portions of internal node
   resources use to terminate hierarchical LSPs, since in circuit-
   switching technologies (such as TDM, LSC, and FSC) LSPs require the
   use of resources allocated in a discrete manner (as predetermined by
   the switching type).  For example, a node with PSC+LSC hierarchical
   switching capability can switch a lambda LSP, but cannot terminate
   the Lambda LSP if there is no available (i.e., not already in use)
   adjustment capability between the LSC and the PSC switching
   components.  Another example occurs when L2SC (Ethernet) switching
   can be adapted in the Link Access Procedure-SDH (LAPS) X.86 and



Papadimitriou, et al.        Standards Track                    [Page 5]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   Generic Framing Procedure (GFP) for instance, before reaching the TDM
   switching matrix.  Similar circumstances can occur, for example, if a
   switching fabric that supports both PSC and L2SC functionalities is
   assembled with LSC interfaces enabling "lambda" encoding.  In the
   switching fabric, some interfaces can terminate Lambda LSPs and
   perform frame (or cell) switching whilst other interfaces can
   terminate Lambda LSPs and perform packet switching.

   Therefore, within multi-region networks, the advertisement of the so-
   called adjustment capability to terminate LSPs (not the interface
   capability since the latter can be inferred from the bandwidth
   available for each switching capability) provides the information to
   take into account when performing multi-region path computation.
   This concept enables a node to discriminate the remote nodes (and
   thus allows their selection during path computation) with respect to
   their adjustment capability, e.g., to terminate LSPs at the PSC or
   LSC level.

   Hence, we introduce the capability of discriminating the (internal)
   adjustment capability from the (interface) switching capability by
   defining an Interface Adjustment Capability Descriptor (IACD).

   A more detailed problem statement can be found in [RFC5339].

3.2.  Interface Adjustment Capability Descriptor (IACD)

   The Interface Adjustment Capability Descriptor (IACD) provides the
   information for the forwarding/switching capability.

   Note that the addition of the IACD as a TE link attribute does not
   modify the format of the Interface Switching Capability Descriptor
   (ISCD) defined in [RFC4202], and does not change how the ISCD sub-TLV
   is carried in the routing protocols or how it is processed when it is
   received [RFC4201], [RFC4203].

   The receiving LSR uses its Link State Database to determine the
   IACD(s) of the far end of the link.  Different Interface Adjustment
   Capabilities at two ends of a TE link are allowed.

3.2.1.  OSPF

   In OSPF, the IACD sub-TLV is defined as an optional sub-TLV of the TE
   Link TLV (Type 2, see [RFC3630]), with Type 25 and variable length.








Papadimitriou, et al.        Standards Track                    [Page 6]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   The IACD sub-TLV format is defined as follows:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Lower SC      | Lower Encoding| Upper SC      | Upper Encoding|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Max LSP Bandwidth at priority 0              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Max LSP Bandwidth at priority 1              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Max LSP Bandwidth at priority 2              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Max LSP Bandwidth at priority 3              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Max LSP Bandwidth at priority 4              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Max LSP Bandwidth at priority 5              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Max LSP Bandwidth at priority 6              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Max LSP Bandwidth at priority 7              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Adjustment Capability-specific information         |
   |                           (variable)                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Lower Switching Capability (SC) field (byte 1) - 8 bits

         Indicates the lower switching capability associated with the
         Lower Encoding field (byte 2).  The value of the Lower
         Switching Capability field MUST be set to the value of
         Switching Capability of the ISCD sub-TLV advertised for this TE
         link.  If multiple ISCD sub-TLVs are advertised for that TE
         link, the Lower Switching Capability (SC) value MUST be set to
         the value of SC to which the adjustment capacity is associated.

      Lower Encoding (byte 2) - 8 bits

         Contains one of the LSP Encoding Type values specified in
         Section 3.1.1 of [RFC3471] and updates.

      Upper Switching Capability (SC) field (byte 3) - 8 bits

         Indicates the upper switching capability.  The Upper Switching
         Capability field MUST be set to one of the values defined in
         [RFC4202].




Papadimitriou, et al.        Standards Track                    [Page 7]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


      Upper Encoding (byte 4) - 8 bits

         Set to the encoding of the available adjustment capacity and to
         0xFF when the corresponding SC value has no access to the wire,
         i.e., there is no ISC sub-TLV for this upper switching
         capability.  The adjustment capacity is the set of resources
         associated to the upper switching capability.

      Max LSP Bandwidth

         The Maximum LSP Bandwidth is encoded as a list of eight 4-octet
         fields in the IEEE floating point format [IEEE], with priority
         0 first and priority 7 last.  The units are bytes per second.
         Processing MUST follow the rules specified in [RFC4202].

      The Adjustment Capability-specific information - variable

         This field is defined so as to leave the possibility for future
         addition of technology-specific information associated to the
         adjustment capability.

         Other fields MUST be processed as specified in [RFC4202] and
         [RFC4203].

   The bandwidth values provide an indication of the resources still
   available to perform insertion/extraction for a given adjustment at a
   given priority (resource pool concept: set of shareable available
   resources that can be assigned dynamically).

   Multiple IACD sub-TLVs MAY be present within a given TE Link TLV.

   The presence of the IACD sub-TLV as part of the TE Link TLV does not
   modify the format/messaging and the processing associated to the ISCD
   sub-TLV defined in [RFC4203].

3.2.2.  IS-IS

   In IS-IS, the IACD sub-TLV is an optional sub-TLV of the Extended IS
   Reachability TLV (see [RFC5305]) with Type 27.

   The IACD sub-TLV format is identical to the OSPF sub-TLV format
   defined in Section 3.2.1.  The fields of the IACD sub-TLV have the
   same processing and interpretation rules as defined in Section 3.2.1.

   Multiple IACD sub-TLVs MAY be present within a given extended IS
   reachability TLV.





Papadimitriou, et al.        Standards Track                    [Page 8]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   The presence of the IACD sub-TLV as part of the extended IS
   reachability TLV does not modify format/messaging and processing
   associated to the ISCD sub-TLV defined in [RFC5307].

4.  Multi-Region Signaling

   Section 6.2 of [RFC4206] specifies that when a region boundary node
   receives a Path message, the node determines whether or not it is at
   the edge of an LSP region with respect to the Explicit Route Object
   (ERO) carried in the message.  If the node is at the edge of a
   region, it must then determine the other edge of the region with
   respect to the Explicit Route Object (ERO), using the IGP database.
   The node then extracts from the ERO the sub-sequence of hops from
   itself to the other end of the region.

   The node then compares the sub-sequence of hops with all existing
   Forwarding Agency LSPs (FA-LSPs) originated by the node:

   o If a match is found, that FA-LSP has enough unreserved bandwidth
     for the LSP being signaled, and the Generalized PID (G-PID) of the
     FA-LSP is compatible with the G-PID of the LSP being signaled, the
     node uses that FA-LSP as follows.  The Path message for the
     original LSP is sent to the egress of the FA-LSP.  The previous hop
     (PHOP) in the message is the address of the node at the head-end of
     the FA-LSP.  Before sending the Path message, the ERO in that
     message is adjusted by removing the subsequence of the ERO that
     lies in the FA-LSP, and replacing it with just the endpoint of the
     FA-LSP.

   o If no existing FA-LSP is found, the node sets up a new FA-LSP.
     That is, it initiates a new LSP setup just for the FA-LSP.

     Note: compatible G-PID implies that traffic can be processed by
     both ends of the FA-LSP without dropping traffic after its
     establishment.

   Applying the procedure of [RFC4206] in an MRN environment MAY lead to
   the setup of single-hop FA-LSPs between each pair of nodes.
   Therefore, considering that the path computation is able to take into
   account richness of information with regard to the SC available on
   given nodes belonging to the path, it is consistent to provide enough
   signaling information to indicate the SC to be used and over which
   link.  Particularly, in case a TE link has multiple SCs advertised as
   part of its ISCD sub-TLVs, an ERO does not provide a mechanism to
   select a particular SC.






Papadimitriou, et al.        Standards Track                    [Page 9]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   In order to limit the modifications to existing RSVP-TE procedures
   ([RFC3473] and referenced), this document defines a new subobject of
   the eXclude Route Object (XRO), see [RFC4874], called the Switching
   Capability subobject.  This subobject enables (when desired) the
   explicit identification of at least one switching capability to be
   excluded from the resource selection process described above.

   Including this subobject as part of the XRO that explicitly indicates
   which SCs have to be excluded (before initiating the procedure
   described here above) over a specified TE link, solves the ambiguous
   choice among SCs that are potentially used along a given path and
   give the possibility to optimize resource usage on a multi-region
   basis.  Note that implicit SC inclusion is easily supported by
   explicitly excluding other SCs (e.g., to include LSC, it is required
   to exclude PSC, L2SC, TDM, and FSC).

   The approach followed here is to concentrate exclusions in XRO and
   inclusions in ERO.  Indeed, the ERO specifies the topological
   characteristics of the path to be signaled.  Usage of Explicit
   Exclusion Route Subobjects (EXRSs) would also lead in the exclusion
   over certain portions of the LSP during the FA-LSP setup.  Thus, it
   is more suited to extend generality of the elements excluded by the
   XRO but also prevent complex consistency checks as well as
   transpositions between EXRS and XRO at FA-LSP head-ends.

4.1.  XRO Subobjects

   The contents of an EXCLUDE_ROUTE object defined in [RFC4874] are a
   series of variable-length data items called subobjects.

   This document defines the Switching Capability (SC) subobject of the
   XRO (Type 35), its encoding, and processing.  It also complements the
   subobjects defined in [RFC4874] with a Label subobject (Type 3).

4.1.1.  SC Subobject

   XRO subobject Type 35: Switching Capability

    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=35   |    Length     |   Attribute   | Switching Cap |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      L (1 bit)

         0 indicates that the attribute specified MUST be excluded.




Papadimitriou, et al.        Standards Track                   [Page 10]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


         1 indicates that the attribute specified SHOULD be avoided.

      Type (7 bits)

         The Type of the XRO SC subobject is 35.

      Length (8 bits)

         The total length of the subobject in bytes (including the Type
         and Length fields).  The Length of the XRO SC subobject is 4.

      Attribute (8 bits)

         0 reserved value.

         1 indicates that the specified SC SHOULD be excluded or avoided
           with respect to the preceding numbered (Type 1 or Type 2) or
           unnumbered interface (Type) subobject.

      Switching Cap (8 bits)

         Switching Capability value to be excluded.

   The Switching Capability subobject MUST follow the set of one or more
   numbered or unnumbered interface subobjects to which this subobject
   refers.

   In the case of a loose-hop ERO subobject, the XRO subobject MUST
   precede the loose-hop subobject identifying the tail-end
   node/interface of the traversed region(s).

4.1.2.  Label Subobject

   The encoding of the XRO Label subobject is identical to the Label ERO
   subobject defined in [RFC3473] with the exception of the L bit.  The
   XRO Label subobject is defined as follows:

   XRO Subobject Type 3: Label Subobject

    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=3     |    Length     |U|   Reserved  |   C-Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Label                             |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




Papadimitriou, et al.        Standards Track                   [Page 11]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


      L (1 bit)

         0 indicates that the attribute specified MUST be excluded.

         1 indicates that the attribute specified SHOULD be avoided.

      Type (7 bits)

         The Type of the XRO Label subobject is 3.

      Length (8 bits)

         The total length of the subobject in bytes (including the Type
         and Length fields).  The Length is always divisible by 4.

      U (1 bit)

         See [RFC3471].

      C-Type (8 bits)

         The C-Type of the included Label Object.  Copied from the Label
         Object (see [RFC3471]).

      Label

         See [RFC3471].

   XRO Label subobjects MUST follow the numbered or unnumbered interface
   subobjects to which they refer, and, when present, MUST also follow
   the Switching Capability subobject.

   When XRO Label subobjects are following the Switching Capability
   subobject, the corresponding label values MUST be compatible with the
   SC capability to be explicitly excluded.

5.  Virtual TE Link

   A virtual TE link is defined as a TE link between two upper-layer
   nodes that is not associated with a fully provisioned FA-LSP in a
   lower layer [RFC5212].  A virtual TE link is advertised as any TE
   link, following the rules in [RFC4206] defined for fully provisioned
   TE links.  A virtual TE link represents thus the potentiality to set
   up an FA-LSP in the lower layer to support the TE link that has been
   advertised.  In particular, the flooding scope of a virtual TE link
   is within an IGP area, as is the case for any TE link.





Papadimitriou, et al.        Standards Track                   [Page 12]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   Two techniques can be used for the setup, operation, and maintenance
   of virtual TE links.  The corresponding GMPLS protocols extensions
   are described in this section.  The procedures described in this
   section complement those defined in [RFC4206] and [HIER-BIS].

5.1.  Edge-to-Edge Association

   This approach, that does not require state maintenance on transit
   LSRs, relies on extensions to the GMPLS RSVP-TE Call procedure (see
   [RFC4974]).  This technique consists of exchanging identification and
   TE attributes information directly between TE link endpoints through
   the establishment of a call between terminating LSRs.  These TE link
   endpoints correspond to the LSP head-end and tail-end points of the
   LSPs that will be established.  The endpoints MUST belong to the same
   (LSP) region.

   Once the call is established, the resulting association populates the
   local Traffic Engineering DataBase (TEDB) and the resulting virtual
   TE link is advertised as any other TE link.  The latter can then be
   used to attract traffic.  When an upper-layer/region LSP tries to
   make use of this virtual TE link, one or more FA LSPs MUST be
   established using the procedures defined in [RFC4206] to make the
   virtual TE link "real" and allow it to carry traffic by nesting the
   upper-layer/region LSP.

   In order to distinguish usage of such call from the call and
   associated procedures defined in [RFC4974], a CALL_ATTRIBUTES object
   is introduced.

5.1.1.  CALL_ATTRIBUTES Object

   The CALL_ATTRIBUTES object is used to signal attributes required in
   support of a call, or to indicate the nature or use of a call.  It is
   modeled on the LSP_ATTRIBUTES object defined in [RFC5420].  The
   CALL_ATTRIBUTES object MAY also be used to report call operational
   state on a Notify message.

   The CALL_ATTRIBUTES object class is 202 of the form 11bbbbbb.  This
   C-Num value (see [RFC2205], Section 3.10) ensures that LSRs that do
   not recognize the object pass it on transparently.

   One C-Type is defined, C-Type = 1 for Call Attributes.  This object
   is OPTIONAL and MAY be placed on Notify messages to convey additional
   information about the desired attributes of the call.







Papadimitriou, et al.        Standards Track                   [Page 13]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   CALL_ATTRIBUTES class = 202, C-Type = 1

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                      Call Attributes TLVs                   //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Call Attributes TLVs are encoded as described in Section 5.1.3.

5.1.2.  Processing

   If an egress (or intermediate) LSR does not support the object, it
   forwards it unexamined and unchanged.  This facilitates the exchange
   of attributes across legacy networks that do not support this new
   object.

5.1.3.  Call Attributes TLVs

   Attributes carried by the CALL_ATTRIBUTES object are encoded within
   TLVs named Call Attributes TLVs.  One or more Call Attributes TLVs
   MAY be present in each object.

   There are no ordering rules for Call Attributes TLVs, and no
   interpretation SHOULD be placed on the order in which these TLVs are
   received.

   Each Call Attributes TLV carried by the CALL_ATTRIBUTES object is
   encoded as follows:

    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              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                            Value                            //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         The identifier of the TLV.






Papadimitriou, et al.        Standards Track                   [Page 14]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


      Length

         Indicates the total length of the TLV in octets.  That is, the
         combined length of the Type, Length, and Value fields, i.e.,
         four plus the length of the Value field in octets.

         The entire TLV MUST be padded with between zero and three
         trailing zeros to make it four-octet aligned.  The Length field
         does not count any padding.

      Value

         The data field for the TLV padded as described above.

   Assignment of Call Attributes TLV types MUST follow the rules
   specified in Section 8 (IANA Considerations).

5.1.4.  Call Attributes Flags TLV

   The Call Attributes TLV of Type 1 defines the Call Attributes Flags
   TLV.  The Call Attributes Flags TLV MAY be present in a
   CALL_ATTRIBUTES object.

   The Call Attributes Flags TLV value field is an array of units of 32
   flags numbered from the most significant bit as bit zero.  The Length
   field for this TLV MUST therefore always be a multiple of 4 bytes,
   regardless of the number of bits carried and no padding is required.

   Unassigned bits are considered reserved and MUST be set to zero on
   transmission by the originator of the object.  Bits not contained in
   the Call Attributes Flags TLV MUST be assumed to be set to zero.  If
   the Call Attributes Flags TLV is absent, either because it is not
   contained in the CALL_ATTRIBUTES object or because this object is
   itself absent, all processing MUST be performed as though the bits
   were present and set to zero.  In other terms, assigned bits that are
   not present either because the Call Attributes Flags TLV is
   deliberately foreshortened or because the TLV is not included MUST be
   treated as though they are present and are set to zero.

5.1.5.  Call Inheritance Flag

   This document introduces a specific Call Inheritance Flag at position
   bit 0 (most significant bit) in the Call Attributes Flags TLV.  This
   flag indicates that the association initiated between the endpoints
   belonging to a call results into a (virtual) TE link advertisement.






Papadimitriou, et al.        Standards Track                   [Page 15]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   The Call Inheritance Flag MUST be set to 1 in order to indicate that
   the established association is to be translated into a TE link
   advertisement.  The value of this flag SHALL by default be set to 1.
   Setting this flag to 0 results in a hidden TE link or in deleting the
   corresponding TE link advertisement (by setting the corresponding
   Opaque LSA Age to MaxAge) if the association had been established
   with this flag set to 1.  In the latter case, the corresponding FA-
   LSP SHOULD also be torn down to prevent unused resources.

   The Notify message used for establishing the association is defined
   as per [RFC4974].  Additionally, the Notify message MUST carry an
   LSP_TUNNEL_INTERFACE_ID Object, that allows identifying unnumbered
   FA-LSPs ([RFC3477], [RFC4206], [HIER-BIS]) and numbered FA-LSPs
   ([RFC4206], [HIER-BIS]).

5.2.  Soft Forwarding Adjacency (Soft FA)

   The Soft Forwarding Adjacency (Soft FA) approach consists of setting
   up the FA LSP at the control plane level without actually committing
   resources in the data plane.  This means that the corresponding LSP
   exists only in the control plane domain.  Once such an FA is
   established, the corresponding TE link can be advertised following
   the procedures described in [RFC4206].

   There are two techniques to set up Soft FAs:

   o The first one consists in setting up the FA LSP by precluding
     resource commitment during its establishment.  These are known as
     pre-planned LSPs.

   o The second technique consists in making use of path-provisioned
     LSPs only.  In this case, there is no associated resource demand
     during the LSP establishment.  This can be considered as the RSVP-
     TE equivalent of the Null service type specified in [RFC2997].

5.2.1.  Pre-Planned LSP Flag

   The LSP ATTRIBUTES object and Attributes Flags TLV are defined in
   [RFC5420].  The present document defines a new flag, the Pre-Planned
   LSP flag, in the existing Attributes Flags TLV (numbered as Type 1).

   The position of this flag is bit 6 in accordance with IANA
   assignment.  This flag, part of the Attributes Flags TLV, follows
   general processing of [RFC5420] for LSP_REQUIRED_ATTRIBUTE object.
   That is, LSRs that do not recognize the object reject the LSP setup
   effectively saying that they do not support the attributes requested.
   Indeed, the newly defined attribute requires examination at all
   transit LSRs along the LSP being established.



Papadimitriou, et al.        Standards Track                   [Page 16]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   The Pre-Planned LSP flag can take one of the following values:

   o When set to 0, this means that the LSP MUST be fully provisioned.
     Absence of this flag (hence corresponding TLV) is therefore
     compliant with the signaling message processing per [RFC3473]).

   o When set to 1, this means that the LSP MUST be provisioned in the
     control plane only.

   If an LSP is established with the Pre-Planned flag set to 1, no
   resources are committed at the data plane level.

   The operation of committing data plane resources occurs by re-
   signaling the same LSP with the Pre-Planned flag set to 0.  It is
   RECOMMENDED that no other modifications are made to other RSVP
   objects during this operation.  That is each intermediate node,
   processing a flag transiting from 1 to 0 shall only be concerned with
   the commitment of data plane resources and no other modification of
   the LSP properties and/or attributes.

   If an LSP is established with the Pre-Planned flag set to 0, it MAY
   be re-signaled by setting the flag to 1.

5.2.2.  Path Provisioned LSPs

   There is a difference between an LSP that is established with 0
   bandwidth (path provisioning) and an LSP that is established with a
   certain bandwidth value not committed at the data plane level (i.e.,
   pre-planned LSP).

   Mechanisms for provisioning (pre-planned or not) LSP with 0 bandwidth
   is straightforward for PSC LSP: in the SENDER_TSPEC/FLOWSPEC object,
   the Peak Data Rate field of IntServ objects (see [RFC2210]) MUST be
   set to 0.  For L2SC LSP: the Committed Information Rate (CIR), Excess
   Information Rate (EIR), Committed Burst Size (CBS), and Excess Burst
   Size (EBS) values MUST be set to 0 in the Type 2 sub-TLV of the
   Ethernet Bandwidth Profile TLV.  In both cases, upon LSP resource
   commitment, actual traffic parameter values are used to perform
   corresponding resource reservation.

   However, mechanisms for provisioning (pre-planned or not) a TDM or
   LSC LSP with 0 bandwidth is currently not possible because the
   exchanged label value is tightly coupled with resource allocation
   during LSP signaling (e.g., see [RFC4606] for a SONET/SDH LSP).  For
   TDM and LSC LSP, a NULL Label value is used to prevent resource
   allocation at the data plane level.  In these cases, upon LSP
   resource commitment, actual label value exchange is performed to
   commit allocation of timeslots/ wavelengths.



Papadimitriou, et al.        Standards Track                   [Page 17]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


6.  Backward Compatibility

   New objects and procedures defined in this document are running
   within a given TE domain, defined as group of LSRs that enforces a
   common TE policy.  Thus, the extensions defined in this document are
   expected to run in the context of a consistent TE policy.
   Specification of a consistent TE policy is outside the scope of this
   document.

   In such TE domains, we distinguish between edge LSRs and intermediate
   LSRs.  Edge LSRs MUST be able to process Call Attributes as defined
   in Section 5.1 if this is the method selected for creating edge-to-
   edge associations.  In that domain, intermediate LSRs are by
   definition transparent to the Call processing.

   In case the Soft FA method is used for the creation of virtual TE
   links, edge and intermediate LSRs MUST support processing of the LSP
   ATTRIBUTE object per Section 5.2.

7.  Security Considerations

   This document does not introduce any new security considerations from
   the ones already detailed in [RFC5920] that describes the MPLS and
   GMPLS security threats, the related defensive techniques, and the
   mechanisms for detection and reporting.  Indeed, the applicability of
   the proposed GMPLS extensions is limited to single TE domain.  Such a
   domain is under the authority of a single administrative entity.  In
   this context, multiple switching layers comprised within such TE
   domain are under the control of a single GMPLS control plane
   instance.

   Nevertheless, Call initiation, as depicted in Section 5.1, MUST
   strictly remain under control of the TE domain administrator.  To
   prevent any abuse of Call setup, edge nodes MUST ensure isolation of
   their call controller (i.e., the latter is not reachable via external
   TE domains).  To further prevent man-in-the-middle attacks, security
   associations MUST be established between edge nodes initiating and
   terminating calls.  For this purpose, Internet Key Exchange (IKE)
   protocol [RFC5996] MUST be used for performing mutual authentication
   and establishing and maintaining these security associations.

8.  IANA Considerations

8.1.  RSVP

   IANA has made the following assignments in the "Class Names, Class
   Numbers, and Class Types" section of the "RSVP PARAMETERS" registry
   available from http://www.iana.org.



Papadimitriou, et al.        Standards Track                   [Page 18]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   This document introduces a new class named CALL_ATTRIBUTES, which has
   been created in the 11bbbbbb range with the following definition:

   Class Number  Class Name                         Reference
   ------------  -----------------------            ---------
   202           CALL ATTRIBUTES                    [RFC6001]

                 Class Type (C-Type):

                 1   Call Attributes                [RFC6001]

   IANA has established a "Call Attributes TLV" registry.  The following
   types are defined:

   TLV Value  Name                                  Reference
   ---------  -------------------------             ---------
   0          Reserved                              [RFC6001]
   1          Call Attributes Flags TLV             [RFC6001]

   The values should be allocated based on the following allocation
   policy as defined in [RFC5226].

   Range         Registration Procedures
   -----         ------------------------
   0-32767       RFC Required
   32768-65535   Reserved for Private Use

   IANA has established a "Call Attributes Flags" registry.  The
   following flags are defined:

   Bit Number  32-bit Value  Name                   Reference
   ----------  ------------  ---------------------  ---------
   0           0x80000000    Call Inheritance Flag  [RFC6001]

   The values should be allocated based on the "RFC Required" policy as
   defined in [RFC5226].

   This document introduces a new Flag in the Attributes Flags TLV
   defined in [RFC5420]:

   Bit Number  Name                   Reference
   ----------  --------------------   ---------
   6           Pre-Planned LSP Flag   [RFC6001]

   This document introduces two new subobjects for the EXCLUDE_ROUTE
   object [RFC4874], C-Type 1.





Papadimitriou, et al.        Standards Track                   [Page 19]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   Subobject Type   Subobject Description
   --------------   -------------------------
   3                Label
   35               Switching Capability (SC)

8.2.  OSPF

   IANA maintains the "Open Shortest Path First (OSPF) Traffic
   Engineering TLVs" registries including the "Types for sub-TLVs of TE
   link TLV (Value 2)" registry.

   This document defines the following sub-TLV of TE link TLV (Value 2).

   Value  Sub-TLV
   -----  -------------------------------------------------
   25     Interface Adjustment Capability Descriptor (IACD)

8.3.  IS-IS

   This document defines the following new sub-TLV type of top-level TLV
   22 that has been reflected in the ISIS sub-TLV registry for TLV 22,
   141, and 222:

   Type  Description                                        Length
   ----  -------------------------------------------------  ------
   27    Interface Adjustment Capability Descriptor (IACD)  Var.

9.  References

9.1.  Normative References

   [IEEE]     IEEE, "IEEE Standard for Binary Floating-Point
              Arithmetic", Standard 754-1985, 1985.

   [RFC2205]  Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
              Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
              Functional Specification", RFC 2205, September 1997.

   [RFC2210]  Wroclawski, J., "The Use of RSVP with IETF Integrated
              Services", RFC 2210, September 1997.

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

   [RFC2997]  Bernet, Y., Smith, A., and B. Davie, "Specification of the
              Null Service Type", RFC 2997, November 2000.





Papadimitriou, et al.        Standards Track                   [Page 20]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   [RFC3471]  Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Functional Description", RFC
              3471, January 2003.

   [RFC3473]  Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Resource ReserVation Protocol-
              Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
              January 2003.

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

   [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.

   [RFC4201]  Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling
              in MPLS Traffic Engineering (TE)", RFC 4201, October 2005.

   [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.

   [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.

   [RFC4606]  Mannie, E. and D. Papadimitriou, "Generalized Multi-
              Protocol Label Switching (GMPLS) Extensions for
              Synchronous Optical Network (SONET) and Synchronous
              Digital Hierarchy (SDH) Control", RFC 4606, August 2006.

   [RFC4874]  Lee, CY., Farrel, A., and S. De Cnodder, "Exclude Routes -
              Extension to Resource ReserVation Protocol-Traffic
              Engineering (RSVP-TE)", RFC 4874, April 2007.








Papadimitriou, et al.        Standards Track                   [Page 21]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   [RFC4974]  Papadimitriou, D. and A. Farrel, "Generalized MPLS (GMPLS)
              RSVP-TE Signaling Extensions in Support of Calls", RFC
              4974, August 2007.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

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

   [RFC5307]  Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS Extensions
              in Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 5307, October 2008.

   [RFC5420]  Farrel, A., Ed., Papadimitriou, D., Vasseur, JP., and A.
              Ayyangarps, "Encoding of Attributes for MPLS LSP
              Establishment Using Resource Reservation Protocol Traffic
              Engineering (RSVP-TE)", RFC 5420, February 2009.

   [RFC5996]  Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
              "Internet Key Exchange Protocol Version 2 (IKEv2)", RFC
              5996, September 2010.

9.2.  Informative References

   [HIER-BIS] Shiomoto, K., Ed., and A. Farrel, "Procedures for
              Dynamically Signaled Hierarchical Label Switched Paths",
              Work in Progress, February 2010.

   [RFC5212]  Shiomoto, K., Papadimitriou, D., Le Roux, JL., Vigoureux,
              M., and D. Brungard, "Requirements for GMPLS-Based Multi-
              Region and Multi-Layer Networks (MRN/MLN)", RFC 5212, July
              2008.

   [RFC5339]  Le Roux, JL., Ed., and D. Papadimitriou, Ed., "Evaluation
              of Existing GMPLS Protocols against Multi-Layer and Multi-
              Region Networks (MLN/MRN)", RFC 5339, September 2008.

   [RFC5710]  Berger, L., Papadimitriou, D., and JP. Vasseur, "PathErr
              Message Triggered MPLS and GMPLS LSP Reroutes", RFC 5710,
              January 2010.

   [RFC5817]  Ali, Z., Vasseur, JP., Zamfir, A., and J. Newton,
              "Graceful Shutdown in MPLS and Generalized MPLS Traffic
              Engineering Networks", RFC 5817, April 2010.





Papadimitriou, et al.        Standards Track                   [Page 22]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


   [RFC5920]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, July 2010.

Acknowledgments

   The authors would like to thank Mr. Wataru Imajuku for the
   discussions on adjustment between regions.

Contributors

   Eiji Oki
   University of Electro-Communications
   1-5-1 Chofugaoka
   Chofu, Tokyo 182-8585, Japan
   EMail: oki@ice.uec.ac.jp

   Ichiro Inoue
   NTT Network Service Systems Laboratories
   3-9-11 Midori-cho
   Musashino-shi, Tokyo 180-8585, Japan
   Phone: +81 422 596076
   EMail: ichiro.inoue@lab.ntt.co.jp

   Emmanuel Dotaro
   Alcatel-Lucent France
   Route de Villejust
   91620 Nozay, France
   Phone: +33 1 69634723
   EMail: emmanuel.dotaro@alcatel-lucent.fr

   Gert Grammel
   Alcatel-Lucent SEL
   Lorenzstrasse, 10
   70435 Stuttgart, Germany
   EMail: gert.grammel@alcatel-lucent.de
















Papadimitriou, et al.        Standards Track                   [Page 23]

RFC 6001          GMPLS Protocol Extensions for MLN/MRN     October 2010


Authors' Addresses

   Dimitri Papadimitriou
   Alcatel-Lucent
   Copernicuslaan 50
   B-2018 Antwerpen, Belgium
   Phone: +32 3 2408491
   EMail: dimitri.papadimitriou@alcatel-lucent.com

   Martin Vigoureux
   Alcatel-Lucent
   Route de Villejust
   91620 Nozay, France
   Phone: +33 1 30772669
   EMail: martin.vigoureux@alcatel-lucent.fr

   Kohei Shiomoto
   NTT
   3-9-11 Midori-cho
   Musashino-shi, Tokyo 180-8585, Japan
   Phone: +81 422 594402
   EMail: shiomoto.kohei@lab.ntt.co.jp

   Deborah Brungard
   ATT
   Rm. D1-3C22 - 200 S. Laurel Ave.
   Middletown, NJ 07748, USA
   Phone: +1 732 4201573
   EMail: dbrungard@att.com

   Jean-Louis Le Roux
   France Telecom
   Avenue Pierre Marzin
   22300 Lannion, France
   Phone: +33 2 96053020
   EMail: jean-louis.leroux@rd.francetelecom.com















Papadimitriou, et al.        Standards Track                   [Page 24]

