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RFC 7897

 
 
 

Domain Subobjects for the Path Computation Element Communication Protocol (PCEP)

Part 2 of 2, p. 17 to 35
Prev Section

 


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4.  Examples

   The examples in this section are for illustration purposes only to
   highlight how the new subobjects could be encoded.  They are not
   meant to be an exhaustive list of all possible use cases and
   combinations.

4.1.  Inter-Area Path Computation

   In an inter-area path computation where the ingress and the egress
   nodes belong to different IGP areas within the same AS, the domain
   sequence could be represented using an ordered list of area
   subobjects.

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    -----------------                              -----------------
   |                 |                            |                 |
   |          +--+   |                            |     +--+        |
   | +--+     |  |   |                            |     |  |        |
   | |  |     +--+   |                            |     +--+   +--+ |
   | +--+            |                            |            |  | |
   |                 |                            |            +--+ |
   |        +--+     |                            |                 |
   |        |  |     |                            |     +--+        |
   |        +--+     |                            |     |  |        |
   |                 | -------------------------- |     +--+        |
   |                +--+                       +--+                 |
   |                |  |         +--+          |  |                 |
   |Area 2          +--+         |  |          +--+  Area 4         |
    ----------------- |          +--+            | -----------------
                      |                          |
                      |                +--+      |
                      |    +--+        |  |      |
                      |    |  |        +--+      |
                      |    +--+                  |
                      |                          |
                      |                          |
                      |                          |
                      |                          |
                      |           +--+           |
                      |           |  |           |
                      |           +--+           |
    ----------------- |                          | ------------------
   |                 +--+                      +--+                  |
   |                 |  |                      |  |                  |
   |                 +--+    Area 0            +--+                  |
   |                 | -------------------------- |     +--+         |
   |          +--+   |                            |     |  |         |
   |          |  |   |                            |     +--+         |
   | +--+     +--+   |                            |                  |
   | |  |            |                            |            +--+  |
   | +--+            |                            |            |  |  |
   |                 |                            |            +--+  |
   |       +--+      |                            |                  |
   |       |  |      |                            |     +--+         |
   |       +--+      |                            |     |  |         |
   |                 |                            |     +--+         |
   |                 |                            |                  |
   | Area 1          |                            |  Area 5          |
    -----------------                              ------------------

                   Figure 1: Inter-Area Path Computation

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   The AS Number is 100.

   If the ingress is in area 2, the egress is in area 4, and transit is
   through area 0, here are some possible ways a PCC can encode the IRO:

     +---------+ +---------+ +---------+
     |IRO      | |Sub-     | |Sub-     |
     |Object   | |object   | |object   |
     |Header   | |Area 0   | |Area 4   |
     |         | |         | |         |
     |         | |         | |         |
     +---------+ +---------+ +---------+

     or

     +---------+ +---------+ +---------+ +---------+
     |IRO      | |Sub-     | |Sub-     | |Sub-     |
     |Object   | |object   | |object   | |object   |
     |Header   | |Area 2   | |Area 0   | |Area 4   |
     |         | |         | |         | |         |
     |         | |         | |         | |         |
     +---------+ +---------+ +---------+ +---------+

     or

     +---------+ +---------+ +---------+ +---------+ +---------+
     |IRO      | |Sub-     | |Sub-     | |Sub-     | |Sub-     |
     |Object   | |object AS| |object   | |object   | |object   |
     |Header   | |100      | |Area 2   | |Area 0   | |Area 4   |
     |         | |         | |         | |         | |         |
     |         | |         | |         | |         | |         |
     +---------+ +---------+ +---------+ +---------+ +---------+

   The domain sequence can further include encompassing AS information
   in the AS subobject.

4.2.  Inter-AS Path Computation

   In inter-AS path computation, where the ingress and egress belong to
   different ASes, the domain sequence could be represented using an
   ordered list of AS subobjects.  The domain sequence can further
   include decomposed area information in the area subobject.

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4.2.1.  Example 1

   As shown in Figure 2, where AS has a single area, the AS subobject in
   the domain sequence can uniquely identify the next domain and PCE.

              AS A                AS E                AS C
         <------------->      <---------->      <------------->

                  A4----------E1---E2---E3---------C4
                 /           /                       \
               /            /                          \
             /            /       AS B                   \
           /            /      <---------->                \
     Ingress------A1---A2------B1---B2---B3------C1---C2------Egress
           \                                    /          /
             \                                /          /
               \                            /          /
                 \                        /          /
                  A3----------D1---D2---D3---------C3

                              <---------->
                                  AS D

     * All ASes have one area (area 0)

                    Figure 2: Inter-AS Path Computation

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   If the ingress is in AS A, the egress is in AS C, and transit is
   through AS B, here are some possible ways a PCC can encode the IRO:

   +-------+ +-------+ +-------+
   |IRO    | |Sub-   | |Sub-   |
   |Object | |object | |object |
   |Header | |AS B   | |AS C   |
   |       | |       | |       |
   +-------+ +-------+ +-------+

   or

   +-------+ +-------+ +-------+ +-------+
   |IRO    | |Sub-   | |Sub-   | |Sub-   |
   |Object | |object | |object | |object |
   |Header | |AS A   | |AS B   | |AS C   |
   |       | |       | |       | |       |
   +-------+ +-------+ +-------+ +-------+

   or

   +-------+ +-------+ +-------+ +-------+ +-------+ +-------+ +-------+
   |IRO    | |Sub-   | |Sub-   | |Sub-   | |Sub-   | |Sub-   | |Sub-   |
   |Object | |object | |object | |object | |object | |object | |object |
   |Header | |AS A   | |Area 0 | |AS B   | |Area 0 | |AS C   | |Area 0 |
   |       | |       | |       | |       | |       | |       | |       |
   +-------+ +-------+ +-------+ +-------+ +-------+ +-------+ +-------+

   Note that to get a domain disjoint path, the ingress could also
   request the backup path with:

   +-------+ +-------+
   |XRO    | |Sub    |
   |Object | |Object |
   |Header | |AS B   |
   |       | |       |
   +-------+ +-------+

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   As described in Section 3.4.3, a domain subobject in IRO changes the
   domain information associated with the next set of subobjects till
   you encounter a subobject that changes the domain too.  Consider the
   following IRO:

   +-------+ +-------+ +-------+ +-------+ +-------+ +-------+
   |IRO    | |Sub-   | |Sub-   | |Sub-   | |Sub-   | |Sub-   |
   |Object | |object | |object | |object | |object | |object |
   |Header | |AS B   | |IP     | |IP     | |AS C   | |IP     |
   |       | |       | |B1     | |B3     | |       | |C1     |
   +-------+ +-------+ +-------+ +-------+ +-------+ +-------+

   On processing subobject "AS B", it changes the AS of the subsequent
   subobjects till we encounter another subobject "AS C" that changes
   the AS for its subsequent subobjects.

   Consider another IRO:

   +-------+ +-------+ +-------+ +-------+ +-------+
   |IRO    | |Sub-   | |Sub-   | |Sub-   | |Sub-   |
   |Object | |object | |object | |object | |object |
   |Header | |AS D   | |IP     | |IP     | |IP     |
   |       | |       | |D1     | |D3     | |C3     |
   +-------+ +-------+ +-------+ +-------+ +-------+

   Here as well, on processing "AS D", it changes the AS of the
   subsequent subobjects till you encounter another subobject "C3" that
   belongs in another AS and changes the AS for its subsequent
   subobjects.

   Further description for the boundary node and inter-AS link can be
   found in Section 4.3.

4.2.2.  Example 2

   In Figure 3, AS 200 is made up of multiple areas.

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                  |
                  |  +-------------+                +----------------+
                  |  |Area 2       |                |Area 4          |
                  |  |         +--+|                |          +--+  |
                  |  |         |  ||                |          | B|  |
                  |  |  +--+   +--+|                |   +--+   +--+  |
                  |  |  |  |       |                |   |  |         |
                  |  |  +--+       |                |   +--+         |
                  |  |        +--+ |                |          +--+  |
                  |  |        |  | |                |          |  |  |
                  |  |        +--+ |                |   +--+   +--+  |
                  |  |  +--+       |+--------------+|   |  |         |
                  |  |  |  |       +--+          +--+   +--+         |
   +-------------+|  |  +--+       |  |          |  |                |
   |             ||  |             +--+          +--+                |
   |         +--+||  +-------------+|              |+----------------+
   |         |  |||                 |     +--+     |
   |         +--+||                 |     |  |     |
   |    +--+     ||                 |     +--+     |
   |    |  |  +---+                +--+            |
   |    +--+  |   |----------------|  |            |
   |          +---+   Inter-AS     +--+   +--+     |
   |+--+         ||    Links        |     |  |     |
   ||A |      +---+                +--+   +--+     |
   |+--+      |   |----------------|  |            |
   |          +---+                +--+   +--+     |
   |    +--+     ||  +------------+ |     |  |     |+----------------+
   |    |  |     ||  |Area 3      +--+    +--+   +--+ Area 5         |
   |    +--+     ||  |            |  |           |  |                |
   |             ||  |            +--+           +--+                |
   |         +--+||  |       +--+ | |  Area 0      ||   +--+         |
   |         |  |||  |       |  | | +--------------+|   |  |         |
   |         +--+||  |       +--+ |                 |   +--+         |
   |             ||  |            |                 |          +--+  |
   |Area 0       ||  |   +--+     |                 |   +--+   |  |  |
   +-------------+|  |   |  |     |                 |   |  |   +--+  |
                  |  |   +--+  +--+                 |   +--+         |
                  |  |         |  |                 |                |
                  |  |         +--+                 |          +--+  |
                  |  |   +--+     |                 |          | C|  |
                  |  |   |  |     |                 |          +--+  |
                  |  |   +--+     |                 |                |
                  |  |            |                 |                |
                  |  +------------+                 +----------------+
                  |
       AS 100     |  AS 200
                  |
                    Figure 3: Inter-AS Path Computation

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   For LSP (A-B), where ingress A is in (AS 100, area 0), egress B is in
   (AS 200, area 4), and transit is through (AS 200, area 0), here are
   some possible ways a PCC can encode the IRO:

   +-------+ +-------+ +-------+ +-------+
   |IRO    | |Sub-   | |Sub-   | |Sub-   |
   |Object | |object | |object | |object |
   |Header | |AS 200 | |Area 0 | |Area 4 |
   |       | |       | |       | |       |
   +-------+ +-------+ +-------+ +-------+

   or

   +-------+ +-------+ +-------+ +-------+ +-------+ +-------+
   |IRO    | |Sub-   | |Sub-   | |Sub-   | |Sub-   | |Sub-   |
   |Object | |object | |object | |object | |object | |object |
   |Header | |AS 100 | |Area 0 | |AS 200 | |Area 0 | |Area 4 |
   |       | |       | |       | |       | |       | |       |
   +-------+ +-------+ +-------+ +-------+ +-------+ +-------+

   For LSP (A-C), where ingress A is in (AS 100, area 0), egress C is in
   (AS 200, area 5), and transit is through (AS 200, area 0), here are
   some possible ways a PCC can encode the IRO:

   +-------+ +-------+ +-------+ +-------+
   |IRO    | |Sub-   | |Sub-   | |Sub-   |
   |Object | |object | |object | |object |
   |Header | |AS 200 | |Area 0 | |Area 5 |
   |       | |       | |       | |       |
   +-------+ +-------+ +-------+ +-------+

   or

   +-------+ +-------+ +-------+ +-------+ +-------+ +-------+
   |IRO    | |Sub-   | |Sub-   | |Sub-   | |Sub-   | |Sub-   |
   |Object | |object | |object | |object | |object | |object |
   |Header | |AS 100 | |Area 0 | |AS 200 | |Area 0 | |Area 5 |
   |       | |       | |       | |       | |       | |       |
   +-------+ +-------+ +-------+ +-------+ +-------+ +-------+

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4.3.  Boundary Node and Inter-AS Link

   A PCC or PCE can include additional constraints covering which
   boundary nodes (ABR or ASBR) or border links (inter-AS link) to be
   traversed while defining a domain sequence.  In which case, the
   boundary node or link can be encoded as a part of the domain
   sequence.

   Boundary nodes (ABR/ASBR) can be encoded using the IPv4 or IPv6
   prefix subobjects, usually with a loopback address of 32 and a prefix
   length of 128, respectively.  An inter-AS link can be encoded using
   the IPv4 or IPv6 prefix subobjects or unnumbered interface
   subobjects.

   For Figure 1, an ABR (say, 203.0.113.1) to be traversed can be
   specified in IRO as:

        +---------+ +---------+ +---------++---------+ +---------+
        |IRO      | |Sub-     | |Sub-     ||Sub-     | |Sub-     |
        |Object   | |object   | |object   ||object   | |object   |
        |Header   | |Area 2   | |IPv4     ||Area 0   | |Area 4   |
        |         | |         | |203.0.   ||         | |         |
        |         | |         | |112.1    ||         | |         |
        +---------+ +---------+ +---------++---------+ +---------+

   For Figure 3, an inter-AS link (say, 198.51.100.1 - 198.51.100.2) to
   be traversed can be specified as:

          +---------+  +---------+ +---------+ +---------+
          |IRO      |  |Sub-     | |Sub-     | |Sub-     |
          |Object   |  |object AS| |object   | |object AS|
          |Header   |  |100      | |IPv4     | |200      |
          |         |  |         | |198.51.  | |         |
          |         |  |         | |100.2    | |         |
          +---------+  +---------+ +---------+ +---------+

4.4.  PCE Serving Multiple Domains

   A single PCE can be responsible for multiple domains; for example,
   PCE function deployed on an ABR could be responsible for multiple
   areas.  A PCE that can support adjacent domains can internally handle
   those domains in the domain sequence without any impact on the other
   domains in the domain sequence.

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4.5.  P2MP

   [RFC7334] describes an experimental inter-domain P2MP path
   computation mechanism where the path domain tree is described as a
   series of domain sequences; an example is shown in the figure below:

                           +----------------+
                           |                |Domain D1
                           |        R       |
                           |                |
                           |        A       |
                           |                |
                           +-B------------C-+
                            /              \
                           /                \
                          /                  \
          Domain D2      /                    \ Domain D3
          +-------------D--+             +-----E----------+
          |                |             |                |
          |  F             |             |                |
          |          G     |             |       H        |
          |                |             |                |
          |                |             |                |
          +-I--------------+             +-J------------K-+
           /\                             /              \
          /  \                           /                \
         /    \                         /                  \
        /      \                       /                    \
       /        \                     /                      \
      /          \                   /                        \
     / Domain D4  \      Domain D5  /              Domain D6   \
   +-L-------------W+       +------P---------+      +-----------T----+
   |                |       |                |      |                |
   |                |       |  Q             |      |   U            |
   |  M        O    |       |         S      |      |                |
   |                |       |                |      |          V     |
   |          N     |       |   R            |      |                |
   +----------------+       +----------------+      +----------------+

                       Figure 4: Domain Tree Example

   The domain tree can be represented as a series of domain sequences:

   o  Domain D1, Domain D3, Domain D6

   o  Domain D1, Domain D3, Domain D5

   o  Domain D1, Domain D2, Domain D4

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   The domain sequence handling described in this document could be
   applied to the P2MP path domain tree.

4.6.  Hierarchical PCE

   In case of H-PCE [RFC6805], the parent PCE can be requested to
   determine the domain sequence and return it in the path computation
   reply, using the ERO.  For the example in Section 4.6 of [RFC6805],
   the domain sequence can possibly appear as:

   +---------+ +---------+ +---------+ +---------+
   |ERO      | |Sub-     | |Sub-     | |Sub-     |
   |Object   | |object   | |object   | |object   |
   |Header   | |Domain 1 | |Domain 2 | |Domain 3 |
   |         | |         | |         | |         |
   |         | |         | |         | |         |
   +---------+ +---------+ +---------+ +---------+

   or

   +---------+ +---------+ +---------+
   |ERO      | |Sub-     | |Sub-     |
   |Object   | |object   | |object   |
   |Header   | |BN 21    | |Domain 3 |
   |         | |         | |         |
   |         | |         | |         |
   +---------+ +---------+ +---------+

5.  Other Considerations

5.1.  Relationship to PCE Sequence

   Instead of a domain sequence, a sequence of PCEs MAY be enforced by
   policy on the PCC, and this constraint can be carried in the PCReq
   message (as defined in [RFC5886]).

   Note that PCE Sequence can be used along with domain sequence, in
   which case PCE Sequence MUST have higher precedence in selecting the
   next PCE in the inter-domain path computation procedures.

5.2.  Relationship to RSVP-TE

   [RFC3209] already describes the notion of abstract nodes, where an
   abstract node is a group of nodes whose internal topology is opaque
   to the ingress node of the LSP.  It further defines a subobject for
   AS but with a 2-byte AS number.

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   [RFC7898] extends the notion of abstract nodes by adding new
   subobjects for IGP areas and 4-byte AS numbers.  These subobjects can
   be included in ERO, XRO, or EXRS in RSVP-TE.

   In any case, subobject types defined in RSVP-TE are identical to the
   subobject types defined in the related documents in PCEP.

6.  IANA Considerations

6.1.  New Subobjects

   IANA maintains the "Path Computation Element Protocol (PCEP) Numbers"
   registry at <http://www.iana.org/assignments/pcep>.  Within this
   registry, IANA maintains two sub-registries:

   o  IRO Subobjects

   o  XRO Subobjects

   IANA has made identical additions to those registries as follows:

   Value   Description        Reference
   -----   ----------------   -------------------
   5       4-byte AS number   RFC 7897, [RFC7898]
   6       OSPF Area ID       RFC 7897, [RFC7898]
   7       IS-IS Area ID      RFC 7897, [RFC7898]

   Further, IANA has added a reference to this document to the new RSVP
   numbers that are registered by [RFC7898], as shown on
   <http://www.iana.org/assignments/rsvp-parameters>.

7.  Security Considerations

   The protocol extensions defined in this document do not substantially
   change the nature of PCEP.  Therefore, the security considerations
   set out in [RFC5440] apply unchanged.  Note that further security
   considerations for the use of PCEP over TCP are presented in
   [RFC6952].

   This document specifies a representation of the domain sequence and
   new subobjects, which could be used in inter-domain PCE scenarios as
   explained in [RFC5152], [RFC5441], [RFC6805], [RFC7334], etc.  The
   security considerations set out in each of these mechanisms remain
   unchanged by the new subobjects and domain sequence representation in
   this document.

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   But the new subobjects do allow finer and more specific control of
   the path computed by a cooperating PCE(s).  Such control increases
   the risk if a PCEP message is intercepted, modified, or spoofed
   because it allows the attacker to exert control over the path that
   the PCE will compute or to make the path computation impossible.
   Consequently, it is important that implementations conform to the
   relevant security requirements of [RFC5440].  These mechanisms
   include:

   o  Securing the PCEP session messages using TCP security techniques
      (Section 10.2 of [RFC5440]).  PCEP implementations SHOULD also
      consider the additional security provided by the TCP
      Authentication Option (TCP-AO) [RFC5925] or Transport Layer
      Security (TLS) [PCEPS].

   o  Authenticating the PCEP messages to ensure the messages are intact
      and sent from an authorized node (Section 10.3 of [RFC5440]).

   o  PCEP operates over TCP, so it is also important to secure the PCE
      and PCC against TCP denial-of-service attacks.  Section 10.7.1 of
      [RFC5440] outlines a number of mechanisms for minimizing the risk
      of TCP-based denial-of-service attacks against PCEs and PCCs.

   o  In inter-AS scenarios, attacks may be particularly significant
      with commercial- as well as service-level implications.

   Note, however, that the domain sequence mechanisms also provide the
   operator with the ability to route around vulnerable parts of the
   network and may be used to increase overall network security.

8.  Manageability Considerations

8.1.  Control of Function and Policy

   The exact behavior with regards to desired inclusion and exclusion of
   domains MUST be available for examination by an operator and MAY be
   configurable.  Manual configurations are needed to identify which
   PCEP peers understand the new domain subobjects defined in this
   document.

8.2.  Information and Data Models

   A MIB module for management of the PCEP is being specified in a
   separate document [RFC7420].  This document does not imply any new
   extension to the current MIB module.

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8.3.  Liveness Detection and Monitoring

   Mechanisms defined in this document do not imply any new liveness
   detection and monitoring requirements aside from those already listed
   in [RFC5440].

8.4.  Verify Correct Operations

   Mechanisms defined in this document do not imply any new operation
   verification requirements aside from those already listed in
   [RFC5440].

8.5.  Requirements on Other Protocols

   In case of per-domain path computation [RFC5152], where the full path
   of an inter-domain TE LSP cannot be determined (or is not determined)
   at the ingress node, a signaling message can use the domain
   identifiers.  The subobjects defined in this document SHOULD be
   supported by RSVP-TE.  [RFC7898] extends the notion of abstract nodes
   by adding new subobjects for IGP areas and 4-byte AS numbers.

   Apart from this, mechanisms defined in this document do not imply any
   requirements on other protocols aside from those already listed in
   [RFC5440].

8.6.  Impact on Network Operations

   The mechanisms described in this document can provide the operator
   with the ability to exert finer and more specific control of the path
   computation by inclusion or exclusion of domain subobjects.  There
   may be some scaling benefit when a single domain subobject may
   substitute for many subobjects and can reduce the overall message
   size and processing.

   Backward compatibility issues associated with the new subobjects
   arise when a PCE does not recognize them, in which case PCE responds
   according to the rules for a malformed object as per [RFC5440].  For
   successful operations, the PCEs in the network would need to be
   upgraded.

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9.  References

9.1.  Normative References

   [ISO10589] International Organization for Standardization,
              "Information technology -- Telecommunications and
              information exchange between systems -- Intermediate
              System to Intermediate System intra-domain routeing
              information exchange protocol for use in conjunction with
              the protocol for providing the connectionless-mode network
              service (ISO 8473)", ISO/IEC 10589:2002, Second Edition,
              2002.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <http://www.rfc-editor.org/info/rfc3209>.

   [RFC3473]  Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Resource ReserVation Protocol-
              Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
              DOI 10.17487/RFC3473, January 2003,
              <http://www.rfc-editor.org/info/rfc3473>.

   [RFC3477]  Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links
              in Resource ReSerVation Protocol - Traffic Engineering
              (RSVP-TE)", RFC 3477, DOI 10.17487/RFC3477, January 2003,
              <http://www.rfc-editor.org/info/rfc3477>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <http://www.rfc-editor.org/info/rfc5440>.

   [RFC5441]  Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux,
              "A Backward-Recursive PCE-Based Computation (BRPC)
              Procedure to Compute Shortest Constrained Inter-Domain
              Traffic Engineering Label Switched Paths", RFC 5441,
              DOI 10.17487/RFC5441, April 2009,
              <http://www.rfc-editor.org/info/rfc5441>.

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   [RFC5521]  Oki, E., Takeda, T., and A. Farrel, "Extensions to the
              Path Computation Element Communication Protocol (PCEP) for
              Route Exclusions", RFC 5521, DOI 10.17487/RFC5521, April
              2009, <http://www.rfc-editor.org/info/rfc5521>.

   [RFC6805]  King, D., Ed. and A. Farrel, Ed., "The Application of the
              Path Computation Element Architecture to the Determination
              of a Sequence of Domains in MPLS and GMPLS", RFC 6805,
              DOI 10.17487/RFC6805, November 2012,
              <http://www.rfc-editor.org/info/rfc6805>.

   [RFC7896]  Dhody, D., "Update to the Include Route Object (IRO)
              Specification in the Path Computation Element
              Communication Protocol (PCEP)", RFC 7896,
              DOI 10.17487/RFC7896, June 2016,
              <http://www.rfc-editor.org/info/rfc7896>.

   [RFC7898]  Dhody, D., Palle, U., Kondreddy, V., and R. Casellas,
              "Domain Subobjects for Resource Reservation Protocol -
              Traffic Engineering (RSVP-TE)", RFC 7898,
              DOI 10.17487/RFC7898, June 2016,
              <http://www.rfc-editor.org/info/rfc7898>.

9.2.  Informative References

   [PCEPS]    Lopez, D., Dios, O., Wu, W., and D. Dhody, "Secure
              Transport for PCEP", Work in Progress,
              draft-ietf-pce-pceps-09, November 2015.

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,
              <http://www.rfc-editor.org/info/rfc4655>.

   [RFC4726]  Farrel, A., Vasseur, J., and A. Ayyangar, "A Framework for
              Inter-Domain Multiprotocol Label Switching Traffic
              Engineering", RFC 4726, DOI 10.17487/RFC4726, November
              2006, <http://www.rfc-editor.org/info/rfc4726>.

   [RFC4873]  Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel,
              "GMPLS Segment Recovery", RFC 4873, DOI 10.17487/RFC4873,
              May 2007, <http://www.rfc-editor.org/info/rfc4873>.

   [RFC4874]  Lee, CY., Farrel, A., and S. De Cnodder, "Exclude Routes -
              Extension to Resource ReserVation Protocol-Traffic
              Engineering (RSVP-TE)", RFC 4874, DOI 10.17487/RFC4874,
              April 2007, <http://www.rfc-editor.org/info/rfc4874>.

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   [RFC5152]  Vasseur, JP., Ed., Ayyangar, A., Ed., and R. Zhang, "A
              Per-Domain Path Computation Method for Establishing Inter-
              Domain Traffic Engineering (TE) Label Switched Paths
              (LSPs)", RFC 5152, DOI 10.17487/RFC5152, February 2008,
              <http://www.rfc-editor.org/info/rfc5152>.

   [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,
              DOI 10.17487/RFC5520, April 2009,
              <http://www.rfc-editor.org/info/rfc5520>.

   [RFC5886]  Vasseur, JP., Ed., Le Roux, JL., and Y. Ikejiri, "A Set of
              Monitoring Tools for Path Computation Element (PCE)-Based
              Architecture", RFC 5886, DOI 10.17487/RFC5886, June 2010,
              <http://www.rfc-editor.org/info/rfc5886>.

   [RFC5925]  Touch, J., Mankin, A., and R. Bonica, "The TCP
              Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
              June 2010, <http://www.rfc-editor.org/info/rfc5925>.

   [RFC6793]  Vohra, Q. and E. Chen, "BGP Support for Four-Octet
              Autonomous System (AS) Number Space", RFC 6793,
              DOI 10.17487/RFC6793, December 2012,
              <http://www.rfc-editor.org/info/rfc6793>.

   [RFC6952]  Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Issues According to the Keying
              and Authentication for Routing Protocols (KARP) Design
              Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013,
              <http://www.rfc-editor.org/info/rfc6952>.

   [RFC7334]  Zhao, Q., Dhody, D., King, D., Ali, Z., and R. Casellas,
              "PCE-Based Computation Procedure to Compute Shortest
              Constrained Point-to-Multipoint (P2MP) Inter-Domain
              Traffic Engineering Label Switched Paths", RFC 7334,
              DOI 10.17487/RFC7334, August 2014,
              <http://www.rfc-editor.org/info/rfc7334>.

   [RFC7420]  Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
              Hardwick, "Path Computation Element Communication Protocol
              (PCEP) Management Information Base (MIB) Module",
              RFC 7420, DOI 10.17487/RFC7420, December 2014,
              <http://www.rfc-editor.org/info/rfc7420>.

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Acknowledgments

   The authors would like to especially thank Adrian Farrel for his
   detailed reviews as well as providing text to be included in the
   document.

   Further, we would like to thank Pradeep Shastry, Suresh Babu, Quintin
   Zhao, Fatai Zhang, Daniel King, Oscar Gonzalez, Chen Huaimo,
   Venugopal Reddy, Reeja Paul, Sandeep Boina, Avantika Sergio Belotti,
   and Jonathan Hardwick for their useful comments and suggestions.

   Thanks to Jonathan Hardwick for shepherding this document.

   Thanks to Deborah Brungard for being the responsible AD.

   Thanks to Amanda Baber for the IANA review.

   Thanks to Joel Halpern for the Gen-ART review.

   Thanks to Klaas Wierenga for the SecDir review.

   Thanks to Spencer Dawkins and Barry Leiba for comments during the
   IESG review.

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Authors' Addresses

   Dhruv Dhody
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   Email: dhruv.ietf@gmail.com


   Udayasree Palle
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   Email: udayasree.palle@huawei.com


   Ramon Casellas
   CTTC
   Av. Carl Friedrich Gauss n7
   Castelldefels, Barcelona  08860
   Spain

   Email: ramon.casellas@cttc.es