TEAS Working Group                                         F. Zhang, Ed.
Internet-Draft                                                    Huawei
Intended status: Standards Track                O. Gonzalez de Dios, Ed.
Expires November 26, 2016 February 16, 2017                          Telefonica Global CTO
                                                              M. Hartley
                                                                  Z. Ali
                                                             C. Margaria

                                                            May 26,

                                                         August 16, 2016

           RSVP-TE Extensions for Collecting SRLG Information


   This document provides extensions for the Resource ReserVation
   Protocol-Traffic Engineering (RSVP-TE), including GMPLS, to support
   automatic collection of Shared Risk Link Group (SRLG) information for
   the TE link formed by a Label Switched Path (LSP).

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
     1.1.  Applicability Example: Dual Homing . . . . . . . . . . . .  3
   2.  Requirements Language  . . . . . . . . . . . . . . . . . . . .  5
   3.  RSVP-TE Requirements . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  SRLG Collection Indication . . . . . . . . . . . . . . . .  5
     3.2.  SRLG Collection  . . . . . . . . . . . . . . . . . . . . .  5
     3.3.  SRLG Update  . . . . . . . . . . . . . . . . . . . . . . .  5
     3.4.  SRLG ID definition . . . . . . . . . . . . . . . . . . . .  6
   4.  Encodings  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  SRLG Collection Flag . . . . . . . . . . . . . . . . . . .  6
     4.2.  RRO SRLG sub-object  . . . . . . . . . . . . . . . . . . .  6
   5.  Signaling Procedures . . . . . . . . . . . . . . . . . . . . .  8
     5.1.  SRLG Collection  . . . . . . . . . . . . . . . . . . . . .  8
     5.2.  SRLG Update  . . . . . . . . . . . . . . . . . . . . . . . 10
     5.3  Domain Boundaries . . . . . . . . . . . . . . . . . . . . . 10
     5.4.  Compatibility  . . . . . . . . . . . . . . . . . . . . . . 10
   6.  Manageability Considerations . . . . . . . . . . . . . . . . . 10
     6.1.  Policy Configuration . . . . . . . . . . . . . . . . . . . 10 11
     6.2.  Coherent SRLG IDs  . . . . . . . . . . . . . . . . . . . . 11
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
     8.1.  RSVP Attribute Bit Flags . . . . . . . . . . . . . . . . . 11
     8.2.  ROUTE_RECORD Object  . . . . . . . . . . . . . . . . . . . 12
     8.3.  Policy Control Failure Error subcodes  . . . . . . . . . . 12
   9.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12
   10.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . 12 13
   11.  References  . . . . . . . . . . . . . . . . . . . . . . . . . 13
     11.1.  Normative References  . . . . . . . . . . . . . . . . . . 13
     11.2.  Informative References  . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14

1.  Introduction

   It is important to understand which Traffic Engineering (TE) links in
   the network might be at risk from the same failures.  In this sense,
   a set of links can constitute a 'shared risk link group' (SRLG) if
   they share a resource whose failure can affect all links in the set

   On the other hand, as described in [RFC4206] and [RFC6107], H-LSP
   (Hierarchical LSP) or S-LSP (stitched LSP) can be used for carrying
   one or more other LSPs.  Both of the H-LSP and S-LSP can be formed as
   a TE link.  In such cases, it is important to know the SRLG
   information of the LSPs that will be used to carry further LSPs.

   This document provides a signaling mechanism to collect the SRLGs
   used by a LSP, which can then be advertized as properties of the TE-
   link formed by that LSP.

1.1.  Applicability Example: Dual Homing

   An interesting use case for the SRLG collection procedures defined in
   this document is achieving LSP diversity in a dual homing scenario.
   The use case is illustrated in Figure 1, when the overlay model is
   applied as defined in RFC 4208 [RFC4208] . In this example, the
   exchange of routing information over the User-Network Interface (UNI)
   is prohibited by operator policy.

                            +---+    +---+
                            | P |....| P |
                            +---+    +---+
                           /              \
                      +-----+               +-----+
             +---+    | PE1 |               | PE3 |    +---+
             |CE1|----|     |               |     |----|CE2|
             +---+\   +-----+               +-----+   /+---+
                   \     |                     |     /
                    \ +-----+               +-----+ /
                     \| PE2 |               | PE4 |/
                      |     |               |     |
                      +-----+               +-----+
                            \              /
                            +---+    +---+
                            | P |....| P |
                            +---+    +---+

                    Figure 1: Dual Homing Configuration

   Single-homed customer edge (CE) devices are connected to a single
   provider edge (PE) device via a single UNI link (which could be a
   bundle of parallel links, typically using the same fiber cable). This
   single UNI link can constitute a single point of failure.  Such a
   single point of failure can be avoided if the CE device is connected
   to two PE devices via two UNI interfaces as depicted in Figure 1
   above for CE1 and CE2, respectively.

   For the dual-homing case, it is possible to establish two connections
   (LSPs) from the source CE device to the same destination CE device
   where one connection is using one UNI link to PE1, for example, and
   the other connection is using the UNI link to PE2.  In order to avoid
   single points of failure within the provider network, it is necessary
   to also ensure path (LSP) diversity within the provider network in
   order to achieve end-to-end diversity for the two LSPs between the
   two CE devices CE1 and CE2.  This use case describes how it is
   possible to achieve path diversity within the provider network based
   on collected SRLG information.  As the two connections (LSPs) enter
   the provider network at different PE devices, the PE device that
   receives the connection request for the second connection needs to
   know the additional path computation constraints such that the path
   of the second LSP is disjoint with respect to the already established
   first connection.

   As SRLG information is normally not shared between the provider
   network and the client network, i.e., between PE and CE devices, the
   challenge is how to solve the diversity problem when a CE is dual-
   homed.  The RSVP extensions for collecting SRLG information defined
   in this document make it possible to retrieve SRLG information for an
   LSP and hence solve the dual-homing LSP diversity problem.  For
   example, CE1 in Figure 1 may have requested an LSP1 to CE2 via PE1
   that is routed via PE3 to CE2.  CE1 can then subsequently request an
   LSP2 to CE2 via PE2 with the constraint that it needs to be maximally
   SRLG disjoint with respect to LSP1.  PE2, however, does not have any
   SRLG information associated with LSP1, which is needed as input for
   its constraint-based path computation function.  If CE1 is capable of
   retrieving the SRLG information associated with LSP1 from PE1, it can
   pass this discovered information to PE2 as part of the LSP2 setup
   request (RSVP PATH message) in an EXCLUDE_ROUTE Object (XRO) or
   Explicit Exclusion Route Subobject (EXRS) as described in [RFC4874],
   and PE2 can now calculate a path for LSP2 that is SRLG disjoint with
   respect to LSP1.  The SRLG information associated with LSP1 can be
   retrieved when LSP1 is established or at any time before LSP2 is

   When CE1 sends the setup request for LSP2 to PE2, it can also request
   the collection of SRLG information for LSP2 and send that information
   to PE1 by re-signaling LSP1 with SRLG-exclusion based on LSP2's
   discovered SRLGs.  This will ensure that the two paths for the two
   LSPs remain mutually diverse, which is important when the provider
   network is capable of restoring connections that failed due to a
   network failure (fiber cut) in the provider network.

   Note that the knowledge of SRLG information even for multiple LSPs
   does not allow a CE device to derive the provider network topology
   based on the collected SRLG information. It would, however, be
   possible for an entity controlling multiple CE devices to derive some
   information related to the topology. This document therefore allows
   PE devices to control the communication of SRLGs outside the provider
   network if desired.

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

3.  RSVP-TE Requirements

   The SRLG-collection process takes place in three stages:

   o  The LSP's ingress node requests that SRLG collection take place;

   o  SRLG data is added to the Path and Resv ROUTE_RECORD Objects
      (RROs) by all nodes during signaling;

   o  Changes to previously-signaled SRLG data are made by sending
      updated Path and Resv messages as required.

3.1.  SRLG Collection Indication

   The ingress node of the LSP needs be capable of indicating whether
   the SRLG information of the LSP is to be collected during the
   signaling procedure of setting up an LSP. There is no need for SRLG
   information to be collected without an explicit request for it being
   made by the ingress node.

   It may be preferable for the SRLG collection request to be understood
   by all nodes along the LSP's path, or it may be more important for
   the LSP to be established successfully even if it traverses nodes
   that cannot supply SRLG information or have not implemented the
   procedures specified in this document. It is desirable for the
   ingress node to make the SRLG collection request in a manner that
   best suits its own policy.

3.2.  SRLG Collection

   If requested, the SRLG information is collected during the setup of
   an LSP.  SRLG information is added by each hop to the Path RRO during
   Path message processing. The same information is also added to the
   Resv RRO during Resv processing at each hop.

3.3.  SRLG Update
   When the SRLG information of an existing LSP for which SRLG
   information was collected during signaling changes, the relevant
   nodes of the LSP need to be capable of updating the SRLG information
   of the LSP.  This means that the signaling procedure needs to be
   capable of updating the new SRLG information.

3.4.  SRLG ID definition

   The identifier of an SRLG (SRLG ID) is defined as a 32-bit quantity
   in [RFC4202]. This definition is used in this document.

4.  Encodings

4.1.  SRLG Collection Flag

   In order to indicate to nodes that SRLG collection is desired, this
   document defines a new flag in the Attribute Flags TLV (see RFC 5420
   [RFC5420]), which MAY be carried
   [RFC5420]). This document defines a new SRLG collection flag in the
   Attribute Flags TLV (see RFC 5420 [RFC5420]). A node that wishes to
   indicate that SRLG collection is desired MUST set this flag in an
   Attribute Flags TLV in an LSP_REQUIRED_ATTRIBUTES Object if
   collection is to be mandatory, or an LSP_ATTRIBUTES Object: Object if
   collection is desired but not mandatory.

   o  Bit Number (specified in Section 8.1): SRLG Collection flag

   The SRLG Collection flag is meaningful on a Path message.  If the
   SRLG Collection flag is set to 1, it means that the SRLG information
   SHOULD be reported to the ingress and egress node along the setup of
   the LSP.

   The rules for the processing of the Attribute Flags TLV are not

4.2.  RRO SRLG sub-object

   This document defines a new RRO sub-object (ROUTE_RECORD sub-object)
   to record the SRLG information of the LSP.  Its format is modeled on
   the RRO sub-objects defined in RFC 3209 [RFC3209].

       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    |D|          Reserved           |
      |                 SRLG ID 1 (4 octets)                          |
      ~                           ......                              ~
      |                 SRLG ID n (4 octets)                          |

   Type (8 bits)

   The type of the sub-object.  The value is specified in Section 8.2.

   Length (8 bits)

   The Length field contains the total length of the sub-object in
   octets, including the Type and Length fields.  The Length depends on
   the number of SRLG IDs.

   Direction bit (D-bit) (1 bit)

   If not set, the SRLGs contained in this sub-object apply to the
   downstream direction. If set, they apply to the upstream direction.

   Reserved (15 bits)

   This 15-bit field is reserved.  It SHOULD be set to zero on
   transmission and MUST be ignored on receipt.

   SRLG ID (4 octets)

   This field contains one SRLG ID.  There is one SRLG ID field per SRLG
   collected.  There MAY be multiple SRLG ID fields in an SRLG sub-

   A node MUST NOT push a SRLG sub-object in the RECORD_ROUTE without
   also pushing either a IPv4 sub-object, a IPv6 sub-object, a
   Unnumbered Interface ID sub-object or a Path Key sub-object.

   As described in RFC 3209 [RFC3209], the RECORD_ROUTE object is
   managed as a stack.  The SRLG sub-object SHOULD MUST be pushed by the node
   before the node IP address or link identifier.  The SRLG-sub-object
   SHOULD be pushed after the Attribute sub-object, if present, and
   after the LABEL sub-object, if requested. It MUST be pushed within
   the hop to which it applies.

   RFC 5553 [RFC5553] describes mechanisms to carry a PKS (Path Key Sub-
   object) in the RRO so as to facilitate confidentiality in the
   signaling of inter-domain TE LSPs, and allows the path segment that
   needs to be hidden (that is, a Confidential Path Segment (CPS)) to be
   replaced in the RRO with a PKS.  If the CPS contains SRLG Sub-
   objects, these MAY be retained in the RRO by adding them again after
   the PKS Sub-object in the RRO.  The CPS is defined in RFC 5520

   The rules for the processing of the LSP_REQUIRED_ATTRIBUTES,
   LSP_ATTRIBUTE and ROUTE_RECORD Objects are not changed.

5.  Signaling Procedures

   The ingress node of the LSP MUST be capable of indicating whether the
   SRLG information of the LSP is to be collected during the signaling
   procedure of setting up an LSP.

5.1.  SRLG Collection

   Per RFC 3209 [RFC3209], an ingress node initiates the recording of
   the route information of an LSP by adding a RRO to a Path message. If
   an ingress node also desires SRLG recording, it MUST set the SRLG
   Collection Flag in the Attribute Flags TLV which MAY be carried
   either in an LSP_REQUIRED_ATTRIBUTES Object when the collection is
   mandatory, or in an LSP_ATTRIBUTES Object when the collection is
   desired, but not mandatory.

   A node SHOULD MUST NOT add SRLG information without an explicit request for
   it being made by the ingress node in the Path message.

   When a node receives a Path message which carries an
   LSP_REQUIRED_ATTRIBUTES Object with the SRLG Collection Flag set, if
   local policy determines that the SRLG information is not to be
   provided to the endpoints, it MUST return a PathErr message with:
   o  Error Code 2 (policy) and
   o  Error subcode "SRLG Recording Rejected" (see Section 8.3 for
   to reject the Path message.

   When a node receives a Path message which carries an LSP_ATTRIBUTES
   Object with the SRLG Collection Flag set, if local policy determines
   that the SRLG information is not to be provided to the endpoints, the
   Path message SHOULD MUST NOT be rejected due to the SRLG recording
   restriction and the Path message SHOULD MUST be forwarded without any SRLG
   sub-object(s) added to the RRO of the corresponding outgoing Path

   If local policy permits the recording of the SRLG information, the
   processing node SHOULD add local SRLG information, as defined below,
   to the RRO of the corresponding outgoing Path message.  The
   processing node MAY add multiple SRLG sub-objects to the RRO if
   necessary.  It then forwards the Path message to the next node in the
   downstream direction. The processing node MUST retain a record of the
   SRLG recording request for reference during Resv processing described

   If the addition of SRLG information to the RRO would result in the
   RRO exceeding its maximum possible size or becoming too large for the
   Path message to contain it, the requested SRLGs MUST NOT be added. If
   the SRLG collection request was contained in an
   LSP_REQUIRED_ATTRIBUTES Object, the processing node MUST behave as
   specified by RFC 3209 [RFC3209] and drop the RRO from the Path
   message entirely.  If the SRLG collection request was contained in an
   LSP_ATTRIBUTES Object, the processing node MAY omit some or all of
   the requested SRLGs from the RRO; otherwise it MUST behave as
   specified by [RFC3209] and drop the RRO from the Path message
   entirely. Subsequent processing of the LSP proceeds as further
   specified in RFC 3209 [RFC3209].

   Following the steps described above, the intermediate nodes of the
   LSP can collect the SRLG information in the RRO during the processing
   of the Path message hop by hop.  When the Path message arrives at the
   egress node, the egress node receives SRLG information in the RRO.

   Per RFC 3209 [RFC3209], when issuing a Resv message for a Path
   message which contains an RRO, an egress node initiates the RRO
   process by adding an RRO to the outgoing Resv message.  The
   processing for RROs contained in Resv messages then mirrors that of
   the Path messages.

   When a node receives a Resv message for an LSP for which SRLG
   Collection was specified in the corresponding Path message, then when
   local policy allows recording SRLG information, the node MUST add
   SRLG information to the RRO of the corresponding outgoing Resv
   message as specified below.  When the Resv message arrives at the
   ingress node, the ingress node can extract the SRLG information from
   the RRO in the same way as the egress node.

   Note that a link's SRLG information for the upstream direction cannot
   be assumed to be the same as that in the downstream.

   o  For Path and Resv messages for a unidirectional LSP, a node SHOULD
      include SRLG sub-objects in the RRO for the downstream data link

   o  For Path and Resv messages for a bidirectional LSP, a node SHOULD
      include SRLG sub-objects in the RRO for both the upstream data
      link and the downstream data link from the local node.  In this
      case, the node MUST include the information in the same order for
      both Path messages and Resv messages.  That is, the SRLG sub-
      object for the upstream link is added to the RRO before the SRLG
      sub-object for the downstream link.

      If SRLG data is added for both the upstream and downstream links,
      the two sets of SRLG data MUST be added in separate SRLG sub-
      objects. A single SRLG sub-object MUST NOT contain a mixture of
      upstream and downstream SRLGs. When adding a SRLG sub-object to an
      RRO, the D-bit MUST be set appropriately to indicate the direction
      of the SRLGs. If an SRLG ID applies in both directions, it SHOULD
      be added to both the upstream and downstream SRLG sub-objects.

   Based on the above procedure, the endpoints can get the SRLG
   information automatically.  Then the endpoints can for instance
   advertise it as a TE link to the routing instance based on the
   procedure described in [RFC6107] and configure the SRLG information
   of the Forwarding Adjacency (FA) automatically.

5.2.  SRLG Update

   When the SRLG information of a link is changed, the endpoints of LSPs
   using that link need to be made aware of the changes.  When a change
   to the set of SRLGs associated with a link occurs, the procedures
   defined in Section 4.4.3 of RFC 3209 [RFC3209] MUST be used to
   refresh the SRLG information for each affected LSP if the SRLG change
   is to be communicated to other nodes according to the local node's
   policy.  If local policy is that the SRLG change SHOULD be suppressed
   or would result in no change to the previously signaled SRLG-list,
   the node SHOULD NOT send an update.

5.3  Domain Boundaries

   If mandated by local policy, policy as specified by the network operator, a
   node MAY remove SRLG information from any RRO in a Path or Resv
   message being processed. It MAY add a summary of the removed SRLGs or
   map them to other SRLG values. However, this SHOULD NOT be done
   unless explicitly mandated by local policy.

5.4.  Compatibility

   A node that does not recognize the SRLG Collection Flag in the
   Attribute Flags TLV is expected to proceed as specified in RFC 5420
   [RFC5420].  It is expected to pass the TLV on unaltered if it appears
   in a LSP_ATTRIBUTES object, or reject the Path message with the
   appropriate Error Code and Value if it appears in a

   A node that does not recognize the SRLG RRO sub-object is expected to
   behave as specified in RFC 3209 [RFC3209]: unrecognized sub-objects
   are to be ignored and passed on unchanged.

6.  Manageability Considerations
6.1.  Policy Configuration

   In a border node of inter-domain or inter-layer network, the
   following SRLG processing policy MUST be capable of being configured:

   o  Whether the node is allowed to participate in SRLG collection.

   o  Whether the node should collection and
      notify changes to collected SRLG information to endpoint nodes as
      described in section 5.2.

   o  Whether the SRLG IDs of the domain or specific layer network can
      be exposed to the nodes outside the domain or layer network, or
      whether they SHOULD be summarized, mapped to values that are
      comprehensible to nodes outside the domain or layer network, or
      removed entirely as described in section 5.3.

   A node using RFC 5553 [RFC5553] and PKS MAY apply the same policy.

6.2.  Coherent SRLG IDs

   In a multi-layer multi-domain scenario, SRLG IDs can be configured by
   different management entities in each layer/domain.  In such
   scenarios, maintaining a coherent set of SRLG IDs is a key
   requirement in order to be able to use the SRLG information properly.
   Thus, SRLG IDs SHOULD be unique.  Note that current procedure is
   targeted towards a scenario where the different layers and domains
   belong to the same operator, or to several coordinated administrative
   groups.  Ensuring the aforementioned coherence of SRLG IDs is beyond
   the scope of this document.

   Further scenarios, where coherence in the SRLG IDs cannot be
   guaranteed are out of the scope of the present document and are left
   for further study.

7.  Security Considerations

   This document builds on the mechanisms defined in [RFC3473], which
   also discusses related security measures.  In addition, [RFC5920]
   provides an overview of security vulnerabilities and protection
   mechanisms for the GMPLS control plane.  The procedures defined in
   this document permit the transfer of SRLG data between layers or
   domains during the signaling of LSPs, subject to policy at the layer
   or domain boundary.  It is recommended that domain/layer boundary
   policies take the implications of releasing SRLG information into
   consideration and behave accordingly during LSP signaling.

8.  IANA Considerations

8.1.  RSVP Attribute Bit Flags
   IANA has created a registry and manages the space of the Attribute
   bit flags of the Attribute Flags TLV, as described in section 11.3 of
   RFC 5420 [RFC5420], in the "Attribute Flags" section of the "Resource
   Reservation Protocol-Traffic Engineering (RSVP-TE) Parameters"
   registry located in http://www.iana.org/assignments/rsvp-te-

   This document introduces a new Attribute Bit Flag:

      Bit No     Name        Attribute   Attribute   ERO  RRO  Reference
                             Flags Path  Flags Resv
      ---------  ----------  ----------  ----------- ---  ---  ---------
      TBD; suggested       SRLG        Yes         No          No   Yes  This I-D
      suggested  Collection
      value: 12  Flag

8.2.  ROUTE_RECORD Object

   IANA manages the "RSVP PARAMETERS" registry located at
   http://www.iana.org/assignments/rsvp-parameters. This document
   introduces a new RRO sub-object:

      Value                    Description             Reference
      ---------------------    -------------------     ---------
      TBD; suggested           SRLG sub-object         This I-D
      value: 34

8.3.  Policy Control Failure Error subcodes

   IANA manages the assignments in the "Error Codes and Globally-Defined
   Error Value Sub-Codes" section of the "RSVP PARAMETERS" registry
   located at http://www.iana.org/assignments/rsvp-parameters.

   This document introduces a new Policy Control Failure Error sub-code:

      Value                   Description               Reference
      ---------------------   -----------------------   ---------
      TBD; suggested          SRLG Recording Rejected   This I-D
       value: 21

9.  Contributors

   Dan Li
   F3-5-B RD Center
   Bantian, Longgang District, Shenzhen  518129
   Email: danli@huawei.com

10.  Acknowledgements

   The authors would like to thank Dieter Beller, Vishnu Pavan Beeram,
   Lou Berger, Deborah Brungard, Igor Bryskin, Ramon Casellas, Niclas
   Comstedt, Alan Davey, Elwyn Davies, Dhruv Dhody, Himanshu Shah and
   Xian Zhang for their useful comments and improvements to this

11.  References

11.1.  Normative References

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

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

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

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

   [RFC5420]  Farrel, A., 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.

   [RFC5520]  Bradford, R., Vasseur, JP., and A. Farrel, "Preserving
              Topology Confidentiality in Inter-Domain Path Computation
              Using a Path-Key-Based Mechanism", RFC 5520, April 2009.

   [RFC5553]  Farrel, A., Bradford, R., and JP. Vasseur, "Resource
              Reservation Protocol (RSVP) Extensions for Path Key
              Support", RFC 5553, May 2009.

11.2.  Informative References

   [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.

   [RFC4208]  Swallow, G., Drake, J., Ishimatsu, H., and Y. Rekhter,
              "Generalized Multiprotocol Label Switching (GMPLS) User-
              Network Interface (UNI): Resource ReserVation Protocol-
              Traffic Engineering (RSVP-TE) Support for the Overlay
              Model", RFC 4208, October 2005.

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

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

   [RFC6107]  Shiomoto, K. and A. Farrel, "Procedures for Dynamically
              Signaled Hierarchical Label Switched Paths", RFC 6107,
              February 2011.

Authors' Addresses

   Fatai Zhang (editor)
   F3-5-B RD Center
   Bantian, Longgang District, Shenzhen  518129
   Email: zhangfatai@huawei.com

   Oscar Gonzalez de Dios (editor)
   Telefonica Global CTO
   Distrito Telefonica, edificio sur, Ronda de la Comunicacion 28045
   Madrid  28050
   Phone: +34 913129647
   Email: oscar.gonzalezdedios@telefonica.com

   Cyril Margaria
   Suite 4001, 200 Somerset Corporate Blvd.
   Bridgewater, NJ  08807
   Email: cyril.margaria@gmail.com

   Matt Hartley
   Email: mhartley@cisco.com
   Zafar Ali
   Email: zali@cisco.com