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

   TEAS Working Group                                    Zafar Ali, Ed.
   Internet Draft                                   George Swallow, Ed.
   Intended status: Standard Track                        Cisco Systems
   Updates RFC4874                                        F. Zhang, Ed.
   Expires: May 17, 2018                                         Huawei
                                                         D. Beller, Ed.
                                                                  Nokia
                                                      November 13, 2017
   
      Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Path
                       Diversity using Exclude Route
   
                    draft-ietf-teas-lsp-diversity-09.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. This document specifies two new diversity
   subobjects for the RSVP eXclude Route Object (XRO) and the Explicit
   Exclusion Route Subobject (EXRS). Three different mechanisms are
   defined to accomplish LSP diversity in the provider or core network:
   the signaled diversity type indicates whether diversity is based on
   client, path computation engine (PCE), or network assigned
   identifiers.
   The solution described in this document is based on the assumption
   that LSPs are requested sequentially, i.e., the time period between
   the LSP setup requests for the two LSPs may be relatively long (in
   the order of days, weeks, months). Re-routing the LSP that was
   established first and may have existed for some time 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
   
   1. Introduction..................................................3
      1.1. Client-Initiated Identifier..............................5
      1.2. PCE-allocated Identifier.................................6
      1.3. Network-Assigned Identifier..............................7
   2. RSVP-TE signaling extensions..................................9
      2.1. Diversity XRO Subobject..................................9
      2.2. Diversity EXRS Subobject................................16
      2.3. Processing rules for the Diversity XRO and EXRS
           subobjects..............................................16
   3. Security Considerations......................................20
   4. IANA Considerations..........................................20
      4.1. New XRO subobject types.................................20
      4.2. New EXRS subobject types................................21
      4.3. New RSVP error sub-codes................................21
   5. Acknowledgements.............................................22
   6. References...................................................22
      6.1. Normative References....................................22
      6.2. Informative References..................................23
   
   
   
   
   
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   1. Introduction
   
      Path diversity for multiple connections is a well-known Service
      Provider 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. 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 (ERO), e.g.
        inter-domain LSPs.
   
      .  Generalized Multi-Protocol Label Switching (GMPLS) User-
        Network Interface (UNI), where the core node may perform path
        computation [RFC4208].
   
      [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.
   
   
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      This is exemplified in the Figure 1, where the overlay reference
      model from [RFC4208] is shown.
   
   
      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.
   
      A single point of failure caused by a single-homed UNI 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
   
   
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      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.
   
      In a UNI network 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 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 the notion of excluding the path taken by particular
      LSP(s). The reference LSP(s) or route(s) from which diversity is
      required is/are identified by an "identifier". The type of
      identifier to use is highly dependent on the networking
      deployment scenario; it could be client-initiated, allocated by
      the (core) network or managed by a PCE. 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.
   
   1.1. Client-Initiated Identifier
   
         The following fields MUST be used to represent the client-
         controlled identifier: IPv4/IPv6 tunnel sender address,
         IPv4/IPv6 tunnel endpoint address, Tunnel ID, and Extended
         Tunnel ID. The client MAY also include 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.ROUTE Identifier (RID), destination address = EN3.RID,
      extended tunnel-id = EN1.RID). Similarly, LSP identifier of the
      EN2-EN3 LSP is LSP-IDENTIFIER2, where LSP-IDENTIFIER12 is defined
      by the tuple (tunnel-id = T2, LSP IS = L1, source address =
   
   
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      EN2.RID, destination address = EN4.RID, extended tunnel-id =
      EN2.RID). The EN1-EN3 LSP is signaled with an exclusion
      requirement from LSP-IDENTIFIER2, and the EN2-EN3 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
      [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 scenarios, a PCE is
      deployed at network node(s) or a PCE is part of a Network
      Management System (NMS). In all these cases, 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 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 improve the situation, node U performs the PCE
      function and replaces the path segment {U, V, W} in the RRO with
      a Path Key subobject. The Path Key subobject assigns an
      "identifier" to the key. The PCE ID in the message indicates that
      it was node U that made the replacement.
   
      With this additional information, the source 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 node U to expand the Path Key and know how to
      avoid the path of the first LSP. Alternatively, the source 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
      Shared Resource Link Group (SRLG) identifier information is both
      available and shareable (by policy) with the ENs, the procedure
   
   
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      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 identifier "123", the CN would use
      local knowledge of the core network SRLGs associated with the
      "123" LSPs and use those SRLGs as constraints for path
      computation. If a PAS identifier is included for exclusion 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.
   
      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
   
   
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      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
      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 as for the XRO subobjects defined in
             [RFC4874], i.e.,
   
             0 indicates that the attribute specified MUST be excluded.
   
             1 indicates that the attribute specified SHOULD be avoided.
   
        XRO Type
   
             The value is set to TBA1 for the IPv4 diversity XRO
             subobject (value to be assigned by IANA). Similarly, the
             value is set to TBA2 for the IPv6 diversity XRO subobject
             (value to be assigned by IANA).
   
   
        Length
   
             Per [RFC4874], the Length contains the total length of the
             IPv4/IPv6 subobject in bytes, including the Type and
   
   
   
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             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. The following flags are defined.
            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.
   
               The penultimate node exception flag is typically set
               when the destination node is single homed (e.g. EN1 or
   
   
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               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-diverse from 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
   
                  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.
   
   
   
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             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 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
              IPv4/IPv6 address of the node allocating the Path Affinity
              Set (PAS).
   
        Diversity Identifier Value:
   
   
   
   
   
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            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                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Extended Tunnel ID                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Extended Tunnel ID (cont.)                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   
   
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      |                   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
             selects a PAS identifier value. Section 1.3 defines the
             PAS term and provides context on how values may be
             selected.
   
   
   
   
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   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 Diversity subobject as specified in this
      document. The same type values TBA1 and TBA2 SHALL 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 recognize the Diversity XRO/ EXRS
      subobject but does not support the DI type, it MUST return a
      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
   
   
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      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. Typically, the ingress node
      of a domain sends a path computation request from ingress node to
      egress node including diversity constraints to a PCE or the
      ingress node is capable to calculate the path for a 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.
             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).
   
   
   
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      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 "IPv4/IPv6 Client
         Initiated Identifiers", the processing node MUST 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 "IPv4/IPv6 PCE
         Allocated Identifiers", 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 IPv4/IPv6 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 "IPv4/IPv6 Network
         Assigned Identifiers", 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
         with the error code "Routing Problem" (24) and error sub-code
         "Route blocked by Exclude Route" (67).
   
      If the L-flag of the XRO diversity subobject or EXRS diversity
      subobject is set, the processing node proceeds as follows:
   
   
   
   
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      -  If the Diversity Identifier Type is set to "IPv4/IPv6 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 "IPv4/IPv6 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
         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
   
   
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         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
      above those identified in [RFC5920], [RFC2205], [RFC3209],
      [RFC3473] and [RFC4874].
   
      The diversity mechanism defined in this document, relies on the
      new diversity subobject that is carried in the XRO or EXRS,
      respectively. In section 7 of [RFC4874], it is stated that the
      XRO could be considered for removal from the Path message due to
      security concerns for example at administrative boundaries. In
      this case, the diversity subobject would also be removed. Hence,
      the diversity subobject MUST be kept while other subobjects may
      be removed.
   
   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
   
   
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      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.
      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:
   
   
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      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.
   
      [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.
   
      [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.
   
   
   
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      [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.
   
      [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
   
   
   
   
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      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
   
      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
   
   
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      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
      Nokia
      Email: Dieter.Beller@nokia.com
   
      George Swallow
      Cisco Systems
      Email: swallow@cisco.com
   
      Fatai Zhang
      Huawei Technologies
      Email: zhangfatai@huawei.com
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
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