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Versions: (draft-ietf-ccamp-lsp-diversity) 00 01 02 03 04 05 06 07 08 09 10

   TEAS Working Group                                    Zafar Ali, Ed.
   Internet Draft                                   George Swallow, Ed.
   Intended status: Standard Track                        Cisco Systems
   Updates RFC4874                                        F. Zhang, Ed.
   Expires: September 03, 2018                                   Huawei
                                                         D. Beller, Ed.
                                                                  Nokia
                                                         March 02, 2018
   
      Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Path
                       Diversity using Exclude Route
   
                    draft-ietf-teas-lsp-diversity-10.txt
   
   
   Status of this Memo
   
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   Abstract
   
   Resource ReSerVation Protocol-Traffic Engineering provides support
   for the communication of exclusion information during label switched
   path (LSP) setup. A typical LSP diversity use case is for
   protection, where two LSPs should follow different paths through the
   network in order to avoid single points of failure, thus greatly
   improving service availability. This document specifies an approach
   which can be used for network scenarios where full knowledge of the
   path(s) is not necessarily known by use of an abstract identifier
   for the path. Three types of abstract identifiers are specified:
   client-based, Path Computation Engine (PCE)-based, network-based.
   This document specifies two new diversity subobjects for the RSVP
   eXclude Route Object (XRO) and the Explicit Exclusion Route
   Subobject (EXRS).
   
   For the protection use case, LSPs are typically created at a slow
   rate and exist for a long time, so that it is reasonable to assume
   that a given (reference) path currently existing, with a well-known
   identifier, will continue to exist and can be used as a reference
   when creating the new diverse path. Re-routing of the existing
   (reference)LSP, before the new path is established, is not
   considered.
   
   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].
   
   Table of Contents
   
   Terms and Abbreviations..........................................3
   1. Introduction..................................................3
      1.1. Client-Initiated Identifier..............................6
      1.2. PCE-allocated Identifier.................................7
      1.3. Network-Assigned Identifier..............................8
   2. RSVP-TE signaling extensions.................................10
      2.1. Diversity XRO Subobject.................................10
      2.2. Diversity EXRS Subobject................................17
      2.3. Processing rules for the Diversity XRO and EXRS
           subobjects..............................................17
   3. Security Considerations......................................21
   4. IANA Considerations..........................................22
      4.1. New XRO subobject types.................................22
      4.2. New EXRS subobject types................................22
      4.3. New RSVP error sub-codes................................22
   
   
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   5. Acknowledgements.............................................23
   6. References...................................................23
      6.1. Normative References....................................23
      6.2. Informative References..................................24
   
   
      Terms and Abbreviations
   
      Diverse LSP: a diverse Label-Switched Path (LSP) is an LSP that
      has a path that does not have any link or SRLG in common with the
      path of a given LSP. Diverse LSPs are meaningful in the context
      of protection or restoration.
   
      ERO: Explicit Route Object as defined in [RFC3209]
   
      EXRS: Explicit eXclusion Route Subobject as defined in [RFC4874]
   
      SRLG: Shared Risk Link Group as defined in [RFC4202]
   
      Reference Path: the reference path is the path of an existing
      LSP, to which the path of a diverse LSP shall be diverse.
   
      XRO: eXclude Route Object as defined in [RFC4874]
   
   1. Introduction
   
      Path diversity for multiple connections is a well-known
      operational requirement. Diversity constraints ensure that Label-
      Switched Paths (LSPs) can be established without sharing network
      resources, thus greatly reducing the probability of simultaneous
      connection failures.
   
      The source node can compute diverse paths for LSPs when it has
      full knowledge of the network topology and is permitted to signal
      an Explicit Route Object (ERO). However, there are scenarios where
      different nodes perform path computations, and therefore there is
      a need for relevant diversity constraints to be signaled to those
      nodes. These include (but are not limited to):
   
      .  LSPs with loose hops in the Explicit Route Object, e.g. inter-
        domain LSPs.
   
      .  Generalized Multi-Protocol Label Switching (GMPLS) User-
        Network Interface (UNI), where the core node may perform path
        computation [RFC4208].
   
   
   
   
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      [RFC4874] introduced a means of specifying nodes and resources to
      be excluded from a route, using the eXclude Route Object (XRO) and
      Explicit Exclusion Route Subobject (EXRS). It facilitates the
      calculation of diverse paths for LSPs based on known properties of
      those paths including addresses of links and nodes traversed, and
      Shared Risk Link Groups (SRLGs) of traversed links. Employing
      these mechanisms requires that the source node that initiates
      signaling knows the relevant properties of the path(s) from which
      diversity is desired. However, there are circumstances under which
      this may not be possible or desirable, including (but not limited
      to):
   
      .  Exclusion of a path which does not originate, terminate or
         traverse the source node of the diverse LSP, in which case the
         addresses of links and SRLGs of the path from which diversity
         is required are unknown to the source node.
   
      .  Exclusion of a path which is known to the source node of the
         diverse LSP for which the node has incomplete or no path
         information, e.g. due to operator policy. In this case, the
         source node is aware of the existence of the reference path but
         the information required to construct an XRO object to
         guarantee diversity from the reference path is not fully known.
         Inter-domain and GMPLS overlay networks can impose such
         restrictions.
   
      This is illustrated in the Figure 1, where the overlay reference
      model from [RFC4208] is shown.
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
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      Overlay                                                  Overlay
      Network       +----------------------------------+       Network
    +---------+     |                                  |     +---------+
    |  +----+ |     |  +-----+    +-----+    +-----+   |     | +----+  |
    |  |    | | UNI |  |     |    |     |    |     |   | UNI | |    |  |
    | -+ EN1+-+-----+--+ CN1 +----+ CN2 +----+ CN3 +---+-----+-+ EN3+- |
    |  |    | |  +--+--+     |    |     |    |     |   | +---+-|    |  |
    |  +----+ |  |  |  +--+--+    +--+--+    +--+--+   | |   | +----+  |
    +---------+  |  |     |          |          |      | |   +---------+
                 |  |     |          |          |      | |
    +---------+  |  |  +--+--+       |       +--+--+   | |   +---------+
    |  +----+ |  |  |  |     |       +-------+     +-----+   | +----+  |
    |  |    +-+--+  |  | CN4 +---------------+ CN5 |   |     | |    |  |
    | -+ EN2+-+-----+--+     |               |     +---+-----+-+ EN4+- |
    |  |    | | UNI |  +-----+               +-----+   | UNI | |    |  |
    |  +----+ |     |                                  |     | +----+  |
    +---------+     +----------------------------------+     +---------+
      Overlay                 Core Network                     Overlay
      Network                                                  Network
   
                        Legend:   EN  -  Edge Node
                                  CN  -  Core Node
   
               Figure 1:  Overlay Reference Model [RFC4208]
   
   
      Figure 1 depicts two types of UNI connectivity: single-homed and
      dual-homed ENs (which also applies to higher order multi-homed
      connectivity). Single-homed EN devices are connected to a single
      CN device via a single UNI link. This single UNI link may
      constitute a single point of failure. UNI connection between EN1
      and CN1 is an example of singled-homed UNI connectivity.
   
      Such a single point of failure can be avoided when the EN device
      is connected to two different CN devices, as depicted for EN2 in
      Figure 1. For the dual-homing case, it is possible to establish
      two different UNI connections from the same source EN device to
      the same destination EN device. For example, two connections from
      EN2 to EN3 may use the two UNI links EN2-CN1 and EN2-CN4. To
      avoid single points of failure within the provider network, it is
      necessary to also ensure path (LSP) diversity within the core
      network.
   
   
   
   
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      In a network providing a set of UNI interfaces between ENs and
      CNs such as that shown in Figure 1, the CNs typically perform
      path computation. Information sharing across the UNI boundary is
      restricted based on the policy rules imposed by the core network.
      Typically, the core network topology information as well as LSP
      path information is not exposed to the ENs. In the network shown
      in Figure 1, consider a use case where an LSP from EN2 to EN4
      needs to be SRLG diverse from an LSP from EN1 to EN3. In this
      case, EN2 may not know SRLG attributes of the EN1- EN3 LSP and
      hence cannot construct an XRO to exclude these SRLGs. In this
      example EN2 cannot use the procedures described in [RFC4874].
      Similarly, an LSP from EN2 to EN3 traversing CN1 needs to be
      diverse from an LSP from EN2 to EN3 going via CN4. Again, in this
      case, exclusions based on [RFC4874] cannot be used.
   
      This document addresses these diversity requirements by
      introducing an approach of excluding the path taken by these
      particular LSP(s). The reference LSP(s) or route(s) from which
      diversity is required is/are identified by an abstract
      "identifier". The type of identifier to use is highly dependent
      on the core network operator's networking deployment scenario; it
      could be client-initiated (provided by the EN), provided by a PCE
      or allocated by the (core) network. This document defines three
      different types of identifiers corresponding to these three
      cases: a client-initiated identifier, a PCE allocated identifier
      and CN ingress node (UNI-N) allocated identifier (= network-
      assigned identifier).
   
   1.1. Client-Initiated Identifier
   
         The following fields MUST be used to represent the client-
         initiated identifier: IPv4/IPv6 tunnel sender address,
         IPv4/IPv6 tunnel endpoint address, Tunnel ID, and Extended
         Tunnel ID. Based on local policy, the client MAY also include
         the LSP ID to identify a specific LSP within the tunnel. These
         fields are defined in [RFC3209], sections 4.6.1.1 and 4.6.2.1.
   
      The usage of the client-initiated identifier is illustrated by
      Figure 1. Suppose a LSP from EN2 to EN4 needs to be diverse with
      respect to a LSP from EN1 to EN3. The LSP identifier of the EN1-
      EN3 LSP is LSP-IDENTIFIER1, where LSP-IDENTIFIER1 is defined by
      the tuple (tunnel-id = T1, LSP ID = L1, source address = EN1.RID
      (ROUTE Identifier), destination address = EN3.RID, extended
      tunnel-id = EN1.RID). Similarly, LSP identifier of the EN2-EN4
      LSP is LSP-IDENTIFIER2, where LSP-IDENTIFIER2 is defined by the
      tuple (tunnel-id = T2, LSP ID = L2, source address = EN2.RID,
      destination address = EN4.RID, extended tunnel-id = EN2.RID). The
   
   
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      EN1-EN3 LSP is signaled with an exclusion requirement from LSP-
      IDENTIFIER2, and the EN2-EN4 LSP is signaled with an exclusion
      requirement from LSP-IDENTIFIER1. In order to maintain diversity
      between these two connections within the core network, the core
      network SHOULD implement Crankback Signaling Extensions as
      defined in [RFC4920]. Note that crankback signaling is known to
      lead to slower setup times and sub-optimal paths under some
      circumstances as described by [RFC4920].
   
   1.2. PCE-allocated Identifier
   
      In scenarios where a PCE is deployed and used to perform path
      computation, the core edge node (e.g., node CN1 in Figure 1)
      could consult a PCE to allocate identifiers, which are used to
      signal path diversity constraints. In other deployment scenarios,
      a PCE is deployed at a network node(s) or a PCE is part of a
      Network Management System (NMS). In all these cases, the PCE is
      consulted and the Path-Key as defined in [RFC5520] can be used in
      RSVP signaling as the identifier to ensure diversity.
   
      An example of specifying LSP diversity using a Path-Key is shown
      in Figure 2, where a simple network with two domains is shown. It
      is desired to set up a pair of path-disjoint LSPs from the source
      in Domain 1 to the destination in Domain 2, but the domains keep
      strict confidentiality about all path and topology information.
   
      The first LSP is signaled by the source with ERO {A, B, loose Dst}
      and is set up with the path {Src, A, B, U, V, W, Dst}. However,
      when sending the Record Route Object (RRO) out of Domain 2, node
      U would normally strip the path and replace it with a loose hop
      to the destination. With this limited information, the source is
      unable to include enough detail in the ERO of the second LSP to
      avoid it taking, for example, the path {Src, C, D, X, V, W, Dst}
      for path-disjointness.
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
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          ---------------------    -----------------------------
         | Domain 1            |  |                    Domain 2 |
         |                     |  |                             |
         |        ---    ---   |  |   ---    ---     ---        |
         |       | A |--| B |--+--+--| U |--| V |---| W |       |
         |      / ---    ---   |  |   ---    ---     --- \      |
         |  ---/               |  |          /       /    \---  |
         | |Src|               |  |         /       /     |Dst| |
         |  ---\               |  |        /       /      /---  |
         |      \ ---    ---   |  |   --- /   --- /  --- /      |
         |       | C |--| D |--+--+--| X |---| Y |--| Z |       |
         |        ---    ---   |  |   ---     ---    ---        |
         |                     |  |                             |
          ---------------------    -----------------------------
   
                Figure 2: A Simple Multi-Domain Network
   
      In order to support LSP diversity, node U consults the PCE and
      replaces the path segment {U, V, W} in the RRO with a Path Key
      subobject. The PCE function assigns an "identifier" and puts it
      into the Path Key field of the Path Key subobject. The PCE ID in
      the message indicates that this replacement operation was
      performed by node U.
   
      With this additional information, the source node is able to
      signal the subsequent LSPs with the ERO set to {C, D, exclude
      Path Key(EXRS), loose Dst}. When the signaling message reaches
      node X, it can consult the PCE function associated with node U to
      expand the Path Key in order to calculate a path that is diverse
      with respect to the first LSP. Alternatively, the source node
      could use an ERO of {C, D, loose Dst} and include an XRO
      containing the Path Key.
   
      This mechanism can work with all the Path Key resolution
      mechanisms, as detailed in [RFC5553] section 3.1. A PCE, co-
      located or not, may be used to resolve the Path Key, but the node
      (i.e., a Label Switching Router (LSR)) can also use the Path Key
      information to index a Path Segment previously supplied to it by
      the entity that originated the Path Key, for example the LSR that
      inserted the Path Key in the RRO or a management system.
   
   
   1.3. Network-Assigned Identifier
   
      There are scenarios in which the network provides diversity-
      related information for a service that allows the client device
      to include this information in the signaling message. If the
   
   
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      Shared Resource Link Group (SRLG) identifier information is both
      available and shareable (by policy) with the ENs, the procedure
      defined in [RFC8001] can be used to collect SRLG identifiers
      associated with an LSP (LSP1). When a second LSP (LSP2) needs to
      be diverse with respect to LSP1, the EN constructing the RSVP
      signaling message for setting up LSP2 can insert the SRLG
      identifiers associated with LSP1 as diversity constraints into
      the XRO using the procedure described in [RFC4874]. However, if
      the core network SRLG identifiers are either not available or not
      shareable with the ENs based on policies enforced by core
      network, existing mechanisms cannot be used.
   
      In this draft, a signaling mechanism is defined where information
      signaled to the CN via the UNI does not require shared knowledge
      of core network SRLG information. For this purpose, the concept
      of a Path Affinity Set (PAS) is defined for abstracting SRLG
      information. The motive behind the introduction of the PAS is to
      minimize the exchange of diversity information between the core
      network (CNs) and the client devices (ENs). The PAS contains an
      abstract SRLG identifier associated with a given path rather than
      a detailed SRLG list. The PAS is a single identifier that can be
      used to request diversity and associate diversity. The means by
      which the processing node determines the path corresponding to
      the PAS is beyond the scope of this document.
   
      A CN on the core network boundary interprets the specific PAS
      identifier (e.g. "123") as meaning to exclude the core network
      SRLG information (or equivalent) that has been allocated by LSPs
      associated with this PAS identifier value. For example, if a Path
      exists for the LSP with the PAS identifier "123", the CN would
      use local knowledge of the core network SRLGs associated with the
      LSPs tagged with PAS attribute "123" and use those SRLGs as
      constraints for path computation. If a PAS identifier is used as
      an exclusion identifier in the connection request, the CN (UNI-N)
      in the core network is assumed to be able to determine the
      existing core network SRLG information and calculate a path that
      meets the determined diversity constraints.
   
      When a CN satisfies a connection setup for a (SRLG) diverse
      signaled path, the CN may optionally record the core network SRLG
      information for that connection in terms of CN based parameters
      and associates that with the EN addresses in the Path message.
      Specifically, for Layer 1 Virtual Private Networks (L1VPNs), Port
      Information Tables (PIT) [RFC5251] can be leveraged to translate
      between client (EN) addresses and core network addresses.
   
   
   
   
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      The means to distribute the PAS information within the core
      network is beyond the scope of this document. For example, the
      PAS and the associated SRLG information can be distributed within
      the core network by an Interior Gateway Protocol (IGP) or by
      other means such as configuration. Regardless of means used to
      distribute the PAS information, the information is kept inside
      the core network and is not shared with the overlay network (see
      Figure 1).
   
   
   
   2. RSVP-TE signaling extensions
   
      This section describes the signaling extensions required to
      address the aforementioned requirements and use cases.
   
   2.1. Diversity XRO Subobject
   
      New Diversity XRO subobjects are defined below for the IPv4 and
      IPv6 address families. Most of the fields in the IPv4 and IPv6
      Diversity XRO subobjects are common and are described following
      the definition of the two subobjects.
   
   
   
      IPv4 Diversity XRO subobject 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |L|  XRO Type   |     Length    |DI Type|A-Flags|E-Flags| Resvd |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           IPv4 Diversity Identifier Source Address            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Diversity Identifier Value                   |
      //                            ...                              //
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   
   
   
   
   
   
   
   
   
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      Similarly, the IPv6 Diversity XRO subobject 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |L|  XRO Type   |     Length    |DI Type|A-Flags|E-Flags| Resvd |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           IPv6 Diversity Identifier source address            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         IPv6 Diversity Identifier source address (cont.)      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         IPv6 Diversity Identifier source address (cont.)      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         IPv6 Diversity Identifier source address (cont.)      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Diversity Identifier Value                   |
      //                            ...                              //
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   
   
        L:
             The L-flag is used in the same way as for the XRO
             subobjects defined in [RFC4874], i.e.,
   
             0 indicates that the diversity constraints MUST be
             satisfied.
   
             1 indicates that the diversity constraints SHOULD be
             satisfied.
   
        XRO Type
   
             The value is set to TBA1 for the IPv4 Diversity XRO
             subobject (value to be assigned by IANA). The value is set
             to TBA2 for the IPv6 Diversity XRO subobject (value to be
             assigned by IANA).
   
   
        Length
   
   
   
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             Per [RFC4874], the Length contains the total length of the
             IPv4/IPv6 subobject in bytes, including the XRO Type and
             Length fields. The Length is variable, depending on the
             diversity identifier value.
   
        Diversity Identifier Type (DI Type)
   
             Diversity Identifier Type (DI Type) indicates the way the
             reference LSP(s) or route(s) with which diversity is
             required is identified in the IPv4/IPv6 Diversity
             subobjects. The following three DI type values are defined
             in this document:
   
                DI Type value   Definition
                -------------   --------------------------------
                      1         Client Initiated Identifier
                      2         PCE Allocated Identifier
                      3         Network Assigned Identifier
   
        Attribute Flags (A-Flags):
   
            The Attribute Flags (A-Flags) are used to communicate
            desirable attributes of the LSP being signaled in the IPv4/
            IPv6 Diversity subobjects. Each flag acts independently.
            Any combination of flags is permitted.
   
            0x01 = Destination node exception
   
               Indicates that the exclusion does not apply to the
               destination node of the LSP being signaled.
   
            0x02 = Processing node exception
   
               Indicates that the exclusion does not apply to the
               node(s) performing ERO expansion for the LSP being
               signaled. An ingress UNI-N node is an example of such a
               node.
   
            0x04 = Penultimate node exception
   
               Indicates that the penultimate node of the LSP being
               signaled MAY be shared with the excluded path even when
               this violates the exclusion flags. This flag is useful,
               for example, when an EN is not dual-homed (like EN4 in
               Figure 1 where all LSPs have to go through CN5).
   
   
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               The penultimate node exception flag is typically set
               when the destination node is single homed (e.g. EN1 or
               EN4 in Figure 1). In such a case, LSP diversity can only
               be accomplished inside the core network up to the egress
               node and the penultimate hop must be the same for the
               LSPs.
   
            0x08 = LSP ID to be ignored
   
               This flag is used to indicate tunnel level exclusion.
               Specifically, this flag is used to indicate that if
               diversity identifier contains LSP ID field, the LSP ID
               is to be ignored and the exclusion applies to any LSP
               matching the rest of the diversity identifier.
   
        Exclusion Flags (E-Flags):
   
             The Exclusion Flags are used to communicate the desired
             type(s) of exclusion requested in the IPv4/IPv6 diversity
             subobjects. The following flags are defined. Any
             combination of these flags is permitted. Please note that
             the exclusion specified by these flags may be modified by
             the value of the Attribute-flags. For example, node
             exclusion flag is ignored for the "Penultimate node" if
             the "Penultimate node exception" flag of the Attribute-
             flags is set.
   
             0x01 = SRLG exclusion
   
                  Indicates that the path of the LSP being signaled is
                  requested to be SRLG disjoint with respect to the
                  excluded path specified by the IPv4/IPv6 Diversity
                  XRO subobject.
   
             0x02 = Node exclusion
   
                  Indicates that the path of the LSP being signaled is
                  requested to be node-diverse from the excluded path
                  specified by the IPv4/IPv6 Diversity XRO subobject.
   
             0x04 = Link exclusion
   
   
   
   
   
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                  Indicates that the path of the LSP being signaled is
                  requested to be link-diverse from the path specified
                  by the IPv4/IPv6 Diversity XRO subobject.
   
   
             0x08 = reserved
   
                  This flag is reserved. It MUST be set to zero on
                  transmission, and MUST be ignored on receipt for both
                  IPv4/IPv6 Diversity XRO subobjects.
   
        Resvd
   
             This field is reserved. It MUST be set to zero on
             transmission, and MUST be ignored on receipt for both
             IPv4/IPv6 Diversity XRO subobjects.
   
   
        IPv4 / IPv6 Diversity Identifier source address:
   
            This field MUST be set to the IPv4/IPv6 address of the node
            that assigns the diversity identifier. Depending on the
            diversity identifier type, the diversity identifier source
            may be a client node, PCE entity or network node.
            Specifically:
   
           o  When the diversity identifier type is set to "IPv4/IPv6
              Client Initiated Identifier", the value MUST be set to
              IPv4/IPv6 tunnel sender address of the reference LSP
              against which diversity is desired. IPv4/IPv6 tunnel
              sender address is as defined in [RFC3209].
   
           o  When the diversity identifier type is set to "IPv4/IPv6
              PCE Allocated Identifier", the value MUST be set to the
              IPv4/IPv6 address of the node that assigned the Path Key
              identifier and that can return an expansion of the Path
              Key or use the Path Key as exclusion in a path
              computation. The Path Key is defined in [RFC5553]. The
              PCE-ID is carried in the Diversity Identifier Source
              Address field of the subobject.
   
           o  When the diversity identifier type is set to "IPv4/IPv6
              Network Assigned Identifier", the value MUST be set to the
   
   
   
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              IPv4/IPv6 address of the node allocating the Path Affinity
              Set (PAS).
   
        Diversity Identifier Value:
   
            Encoding for this field depends on the diversity identifier
            type, as defined in the following.
   
            When the diversity identifier type is set to "Client
            Initiated Identifier" in the IPv4 Diversity XRO subobject,
            the diversity identifier value MUST be 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 IPv4 tunnel end point address                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Must Be Zero         |     Tunnel ID                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Extended Tunnel ID                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Must Be Zero         |            LSP ID             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   
   
            The IPv4 tunnel end point address, Tunnel ID, Extended
            Tunnel ID and LSP ID are as defined in [RFC3209].
   
            When the diversity identifier type is set to "Client
            Initiated Identifier" in the IPv6 Diversity XRO subobject,
            the diversity identifier value MUST be 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 IPv6 tunnel end point address                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             IPv6 tunnel end point address (cont.)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             IPv6 tunnel end point address (cont.)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             IPv6 tunnel end point address (cont.)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Must Be Zero         |     Tunnel ID                 |
   
   
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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Extended Tunnel ID                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Extended Tunnel ID (cont.)                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Extended Tunnel ID (cont.)                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Extended Tunnel ID (cont.)                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Must Be Zero         |            LSP ID             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   
   
            The IPv6 tunnel end point address, Tunnel ID, IPv6 Extended
            Tunnel ID and LSP ID are as defined in [RFC3209].
   
            When the diversity identifier type is set to "PCE Allocated
            Identifier" in IPv4 or IPv6 Diversity XRO subobject, the
            diversity identifier value MUST be 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Must Be Zero          |           Path Key            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   
   
            The Path Key is defined in [RFC5553].
   
            When the diversity identifier type is set to "Network
            Assigned Identifier" in IPv4 or IPv6 Diversity XRO
            subobject, the diversity identifier value MUST be 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Path Affinity Set (PAS) identifier                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   
   
             The Path Affinity Set (PAS) identifier field is a 32-bit
             value that is scoped by, i.e., is only meaningful when
             used in combination with, the Diversity Identifier source
             address field. There are no restrictions on how a node
   
   
   
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             selects a PAS identifier value. Section 1.3 defines the
             PAS term and provides context on how values may be
             selected.
   
   
   2.2. Diversity EXRS Subobject
   
      [RFC4874] defines the EXRS ERO subobject. An EXRS is used to
      identify abstract nodes or resources that must not or should not
      be used on the path between two inclusive abstract nodes or
      resources in the explicit route. An EXRS contains one or more
      subobjects of its own, called EXRS subobjects [RFC4874].
   
      An EXRS MAY include a Diversity subobject as specified in this
      document. The same type values TBA1 and TBA2 MUST be used.
   
   2.3. Processing rules for the Diversity XRO and EXRS subobjects
   
      The procedure defined in [RFC4874] for processing the XRO and
      EXRS is not changed by this document. The processing rules for
      the Diversity XRO and EXRS subobjects are similar unless the
      differences are explicitly described. Similarly, IPv4 and IPv6
      Diversity XRO subobjects and IPv4 and IPv6 Diversity EXRS
      subobjects follow the same processing rules.
   
      If the processing node cannot recognize the Diversity XRO/EXRS
      subobject, the node is expected to follow the procedure defined
      in [RFC4874].
   
      An XRO/EXRS object MAY contain multiple Diversity subobjects of
      the same DI Type. E.g., in order to exclude multiple Path Keys, a
      node MAY include multiple Diversity XRO subobjects each with a
      different Path Key. Similarly, in order to exclude the routes
      taken by multiple LSPs, a node MAY include multiple Diversity
      XRO/EXRS subobjects each with a different LSP identifier.
      Likewise, to exclude multiple PAS identifiers, a node MAY include
      multiple Diversity XRO/EXRS subobjects each with a different PAS
      identifier. However, all Diversity subobjects in an XRO/EXRS MUST
      contain the same Diversity Identifier Type. If a Path message
      contains an XRO/EXRS with multiple Diversity subobjects of
      different DI Types, the processing node MUST return a PathErr
      with the error code "Routing Problem" (24) and error sub-code
      "XRO/EXRS Too Complex" (68/69).
   
      If the processing node recognizes the Diversity XRO/EXRS
      subobject but does not support the DI type, it MUST return a
   
   
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      PathErr with the error code "Routing Problem" (24) and error sub-
      code "Unsupported Diversity Identifier Type" (TBA3).
   
      In case of DI type "Client Initiated Identifier", all nodes along
      the path SHOULD process the diversity information signaled in the
      XRO/EXRS Diversity subobjects to verify that the signaled
      diversity constraint is satisfied. If a diversity violation is
      detected, crankback signaling MAY be initiated.
   
      In case of DI type "PCE Allocated Identifier" and "Network
      Assigned Identifier", the nodes in the domain that perform path
      computation SHOULD process the diversity information signaled in
      the XRO/EXRS Diversity subobjects as follows. In the PCE case,
      the ingress node of a domain sends a path computation request for
      a path from ingress node to egress node including diversity
      constraints to a PCE. Or,in the PAS case, the ingress node is
      capable to calculate the path for the new LSP from ingress node
      to the egress node taking the diversity constraints into account.
      The calculated path is then carried in the explicit route object
      (ERO). Hence, the transit nodes in a domain and the domain egress
      node SHOULD NOT process the signaled diversity information unless
      path computation is performed.
   
      While processing EXRS object, if a loose hop expansion results in
      the creation of another loose hop in the outgoing ERO, the
      processing node MAY include the EXRS in the newly created loose
      hop for further processing by downstream nodes.
   
      The Attribute-flags affect the processing of the Diversity
      XRO/EXRS subobject as follows:
   
           o When the "Processing node exception" flag is set, the
             exclusion MUST be ignored for the node processing the XRO
             or EXRS subobject.
   
           o When the "Destination node exception" flag is set, the
             exclusion MUST be ignored for the destination node in
             processing the XRO subobject. The destination node
             exception for the EXRS subobject applies to the explicit
             node identified by the ERO subobject that identifies the
             next abstract node. When the "destination node exception"
             flag is set in the EXRS subobject, exclusion MUST be
             ignored for the said node (i.e., the next abstract node).
   
           o When the "Penultimate node exception" flag is set in the
             XRO subobject, the exclusion MUST be ignored for the
             penultimate node on the path of the LSP being established.
   
   
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             The penultimate node exception for the EXRS subobject
             applies to the node before the explicit node identified by
             the ERO subobject that identifies the next abstract node.
             When the "penultimate node exception" flag is set in the
             EXRS subobject, the exclusion MUST be ignored for the said
             node (i.e., the node before the next abstract node).
   
      If the L-flag of the Diversity XRO subobject or Diversity EXRS
      subobject is not set, the processing node proceeds as follows.
   
      -  If the Diversity Identifier Type is set to "Client Initiated
         Identifier", the processing node MUST ensure that the path
         calculated/expanded for the signaled LSP is diverse from the
         route taken by the LSP identified in the Diversity Identifier
         Value field.
   
      -  If the Diversity Identifier Type is set to "PCE Allocated
         Identifier", the processing node MUST ensure that any path
         calculated for the signaled LSP is diverse from the route
         identified by the Path Key. The processing node MAY use the PCE
         identified by the Diversity Identifier Source Address in the
         subobject for route computation. The processing node MAY use
         the Path Key resolution mechanisms described in [RFC5553].
   
      -  If the Diversity Identifier Type is set to "Network Assigned
         Identifier", the processing node MUST ensure that the path
         calculated for the signaled LSP is diverse with respect to the
         values associated with the PAS identifier and Diversity
         Identifier source address fields.
   
      -  Regardless of whether the path computation is performed
         locally or at a remote node (e.g., PCE), the processing node
         MUST ensure that any path calculated for the signaled LSP is
         diverse from the requested Exclusion Flags.
   
      -  If the excluded path referenced in the XRO subobject is
         unknown to the processing node, the processing node SHOULD
         ignore the Diversity XRO subobject and SHOULD proceed with the
         signaling request. After sending the Resv for the signaled LSP,
         the processing node MUST return a PathErr with the error code
         "Notify Error" (25) and error sub-code TBA4 "Route of XRO LSP
         identifier unknown" (value to be assigned by IANA) for the
         signaled LSP.
   
      -  If the processing node fails to find a path that meets the
         requested constraint, the processing node MUST return a PathErr
   
   
   
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         with the error code "Routing Problem" (24) and error sub-code
         "Route blocked by Exclude Route" (67).
   
      If the L-flag of the Diversity XRO subobject or Diversity EXRS
      subobject is set, the processing node proceeds as follows:
   
      -  If the Diversity Identifier Type is set to " Client Initiated
         Identifiers", the processing node SHOULD ensure that the path
         calculated/ expended for the signaled LSP is diverse from the
         route taken by the LSP identified in the Diversity Identifier
         Value field.
   
      -  If the Diversity Identifier Type is set to " PCE Allocated
         Identifiers", the processing node SHOULD ensure that the path
         calculated for the signaled LSP is diverse from the route
         identified by the Path Key.
   
      -  If the Diversity Identifier Type is set to "IPv4/IPv6 Network
         Assigned Identifiers", the processing node SHOULD ensure that
         the path calculated for the signaled LSP is diverse with
         respect to the values associated with the PAS identifier and
         Diversity Identifier source address fields.
   
      -  If the processing node fails to find a path that meets the
         requested constraint, it SHOULD proceed with signaling using a
         suitable path that meets the constraint as far as possible.
         After sending the Resv for the signaled LSP, it MUST return a
         PathErr message with error code "Notify Error" (25) and error
         sub-code TBA5 "Failed to satisfy Exclude Route" (value: to be
         assigned by IANA) to the source node.
   
      If, subsequent to the initial signaling of a diverse LSP, an
      excluded path referenced in the XRO subobject becomes known to
      the processing node, or a change in the excluded path becomes
      known to the processing node, the processing node MUST re-
      evaluate the exclusion and diversity constraints requested by the
      diverse LSP to determine whether they are still satisfied.
   
      -  In case the L-flag was not set in the initial setup message,
         the exclusion and diversity constraints were satisfied at the
         time of the initial setup. If the processing node re-evaluating
         the exclusion and diversity constraints for a diverse LSP
         detects that the exclusion and diversity constraints are no
         longer met, it MUST send a PathErr message for the diverse LSP
         with the error code "Routing Problem" (24) and error sub-code
         "Route blocked by Exclude Route" (67). The Path_State_Removed
         flag (PSR) [RFC3473] MUST NOT be set. A source node receiving a
   
   
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         PathErr message with this error code and sub-code combination
         SHOULD take appropriate actions and move the diverse LSP to a
         new path that meets the original constraints.
   
      -  In case the L-flag was set in the initial setup message, the
         exclusion and diversity constraints may or may not be satisfied
         at any given time. If the exclusion constraints for a diverse
         LSP were satisfied before and if the processing node re-
         evaluating the exclusion and diversity constraints for a
         diverse LSP detects that exclusion and diversity constraints
         are no longer met, it MUST send a PathErr message for the
         diverse LSP with the error code error code "Notify Error" (25)
         and error sub-code TBA5 "Failed to satisfy Exclude Route"
         (value: to be assigned by IANA). The PSR flag MUST NOT be set.
         The source node MAY take no consequent action and keep the LSP
         along the path that does not meet the original constraints.
         Similarly, if the exclusion constraints for a diverse LSP were
         not satisfied before and if the processing node re-evaluating
         the exclusion and diversity constraints for a diverse LSP
         detects that the exclusion constraints are met, it MUST send a
         PathErr message for the diverse LSP with the error code "Notify
         Error" (25) and a new error sub- code TBA6 "Compliant path
         exists" (value: to be assigned by IANA). The PSR flag MUST NOT
         be set. A source node receiving a PathErr message with this
         error code and sub-code combination MAY move the diverse LSP to
         a new path that meets the original constraints.
   
   
   
   3. Security Considerations
   
      This document does not introduce any additional security issues
      in addition to those identified in [RFC5920], [RFC2205],
      [RFC3209], [RFC3473], [RFC2747], [RFC4874], [RFC5520], and
      [RFC5553].
   
      The diversity mechanisms defined in this document, rely on the
      new diversity subobject that is carried in the XRO or EXRS,
      respectively. In section 7 of [RFC4874], it is noted some
      administrative boundaries may remove the XRO due to security
      concerns on explicit route information exchange. However, when
      the diversity subobjects specified in this document are used,
      removing at the administrative boundary an XRO containing these
      diversity subobjects would result in the request for diversity
      being dropped at the boundary, and path computation would be
      unlikely to produce the requested diverse path. As such,
      diversity subobjects MUST be retained in an XRO crossing an
   
   
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      administrative boundary, even if other subobjects are removed.
      This retention would be based on operator policy. The use of
      diversity subobjects are based on mutual agreement. This avoids
      the need to share the identity of network resources when
      supporting diversity.
   
   4. IANA Considerations
   
      IANA is requested to administer the assignment of new values
      defined in this document and summarized in this section.
   
   4.1. New XRO subobject types
   
      IANA registry: RSVP PARAMETERS
      Subsection: Class Names, Class Numbers, and Class Types
   
      This document defines two new subobjects for the EXCLUDE_ROUTE
      object [RFC4874], C-Type 1. (see:
      http://www.iana.org/assignments/rsvp-parameters/rsvp-
      parameters.xhtml#rsvp-parameters-94)
   
       +--------------------------+----------------+
       | Subobject Description    | Subobject Type |
       +--------------------------+----------------+
       | IPv4 Diversity subobject |    TBA1        |
       | IPv6 Diversity subobject |    TBA2        |
       +--------------------------+----------------+
   
   
   4.2. New EXRS subobject types
   
      The Diversity XRO subobjects are also defined as new EXRS
      subobjects. (EXPLICIT_ROUTE see:
      http://www.iana.org/assignments/rsvp-parameters/rsvp-
      parameters.xhtml#rsvp-parameters-24). The same numeric subobject
      type values TBA1 and TBA2 are being requested for the two new
      EXRS subobjects.
   
   
   4.3. New RSVP error sub-codes
   
      IANA registry: RSVP PARAMETERS
      Subsection: Error Codes and Globally Defined Error Value Sub-
      Codes.
   
   
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      For Error Code "Routing Problem" (24) (see [RFC3209]) the
      following sub-codes are defined. (see:
      http://www.iana.org/assignments/rsvp-parameters/rsvp-
      parameters.xhtml#rsvp-parameters-105)
   
   
       +-------------+----------------------------+---------------+
       | Error Value | Description                | Reference     |
       | Sub-codes   |                            |               |
       +-------------+----------------------------+---------------+
       | TBA3        | Unsupported Diversity      | This document |
       |             | Identifier Type            |               |
       +-------------+----------------------------+---------------+
   
      For Error Code "Notify Error" (25) (see [RFC3209]) the following
      sub-codes are defined. (see:
      http://www.iana.org/assignments/rsvp-parameters/rsvp-
      parameters.xhtml#rsvp-parameters-105)
   
   
       +-------------+----------------------------+---------------+
       | Error Value | Description                | Reference     |
       | Sub-codes   |                            |               |
       +-------------+----------------------------+---------------+
       | TBA4        | Route of XRO LSP           | This document |
       |             | identifier unknown         |               |
       | TBA5        | Failed to satisfy          | This document |
       |             | Exclude Route              |               |
       | TBA6        | Compliant path exists      | This document |
       +-------------+----------------------------+---------------+
   
   
   5. Acknowledgements
   
      The authors would like to thank Xihua Fu for his contributions.
      The authors also would like to thank Luyuan Fang and Walid Wakim
      for their review comments.
   
   6. References
   
   6.1. Normative References
   
      [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.
   
   
   
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      [RFC2205] Braden, R. (Ed.), Zhang, L., Berson, S., Herzog, S. and
                S. Jamin, "Resource ReserVation Protocol -- Version 1
                Functional Specification", RFC 2205, September 1997.
   
      [RFC2747] Baker, F., Lindell, B. and M. Talwar, "RSVP
                Cryptographic Authentication", RFC 2747, January 2000.
   
      [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, Ed., K, Rekhter, Y, Ed., "Routing Extensions
                in Support of Generalized Multi-Protocol Label
                Switching (GMPLS)", RFC 4202, 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.
   
      [RFC4920] Farrel, A., Ed., Satyanarayana, A., Iwata, A., Fujita,
                N., and G. Ash, "Crankback Signaling Extensions for
                MPLS and GMPLS RSVP-TE", RFC 4920, July 2007.
   
      [RFC5553] Farrel, A., Ed., Bradford, R., and JP. Vasseur,
                "Resource Reservation Protocol (RSVP) Extensions for
                Path Key Support", RFC 5553, May 2009.
   
   
   
   6.2. Informative References
   
      [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.
   
      [RFC5520] Bradford, R., Ed., Vasseur, JP., and A. Farrel,
                "Preserving Topology Confidentiality in Inter-Domain
                Path Computation Using a Path-Key-Based Mechanism", RFC
                5520, April 2009.
   
   
   
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      [RFC8001] F. Zhang, D. Li, O. Gonzalez de Dios, C. Margaria,
                "RSVP-TE Extensions for Collecting SRLG Information",
                RFC 8001, January 2017.
   
      [RFC2205] Braden, R. (Ed.), Zhang, L., Berson, S., Herzog, S. and
                S. Jamin, "Resource ReserVation Protocol -- Version 1
                Functional Specification", RFC 2205, September 1997.
   
      [RFC5251] Fedyk, D. (Ed.), Rekhter, Y. (Ed.), Papadimitriou, D.,
                Rabbat, R., and Berger, L., "Layer 1 VPN Basic Mode",
                RFC 5251, July 2008.
   
      [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
                Networks", RFC 5920, July 2010.
   
   
   
   Contributors' Addresses
   
      Igor Bryskin
      Huawei Technologies
      Email: Igor.Bryskin@huawei.com
   
      Daniele Ceccarelli
      Ericsson
      Email: Daniele.Ceccarelli@ericsson.com
   
      Dhruv Dhody
      Huawei Technologies
      Email: dhruv.ietf@gmail.com
   
      Oscar Gonzalez de Dios
      Telefonica I+D
      Email: ogondio@tid.es
   
      Don Fedyk
      Hewlett-Packard Enterprise
      Email: don.fedyk@hpe.com
   
      Clarence Filsfils
      Cisco Systems, Inc.
      Email: cfilsfil@cisco.com
   
   
   
   
   
   
   
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      Gabriele Maria Galimberti
      Cisco Systems
      Email: ggalimbe@cisco.com
   
      Ori Gerstel
      SDN Solutions Ltd.
      Email: origerstel@gmail.com
   
      Matt Hartley
      Cisco Systems
      Email: mhartley@cisco.com
   
      Kenji Kumaki
      KDDI Corporation
      Email: ke-kumaki@kddi.com
   
      Ruediger Kunze
      Deutsche Telekom AG
      Email: Ruediger.Kunze@telekom.de
   
      Lieven Levrau
      Nokia
      Email: Lieven.Levrau@nokia.com
   
      Cyril Margaria
      cyril.margaria@gmail.com
   
      Julien Meuric
      France Telecom Orange
      Email: julien.meuric@orange.com
   
      Yuji Tochio
      Fujitsu
      Email: tochio@jp.fujitsu.com
   
      Xian Zhang
      Huawei Technologies
      Email: zhang.xian@huawei.com
   
   Authors' Addresses
   
      Zafar Ali
      Cisco Systems.
      Email: zali@cisco.com
   
      Dieter Beller
   
   
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      Nokia
      Email: Dieter.Beller@nokia.com
   
      George Swallow
      Cisco Systems
      Email: swallow@cisco.com
   
      Fatai Zhang
      Huawei Technologies
      Email: zhangfatai@huawei.com
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
                           Expires September 2018             [Page 27]
   

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