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Versions: (draft-dhody-ccamp-rsvp-te-domain-subobjects) 00 01 02 draft-ietf-teas-rsvp-te-domain-subobjects

CCAMP Working Group                                             D. Dhody
Internet-Draft                                                  U. Palle
Intended status: Experimental                               V. Kondreddy
Expires: January 2, 2015                             Huawei Technologies
                                                             R. Casellas
                                                                    CTTC
                                                            July 1, 2014


     Domain Subobjects for Resource ReserVation Protocol - Traffic
                         Engineering (RSVP-TE)
             draft-ietf-ccamp-rsvp-te-domain-subobjects-02

Abstract

   The Resource ReserVation Protocol - Traffic Engineering (RSVP-TE)
   specification and the Generalized Multiprotocol Label Switching
   (GMPLS) extensions to RSVP-TE allow abstract nodes and resources to
   be explicitly included in a path setup.  Further Exclude Routes
   extensions to RSVP-TE allow abstract nodes and resources to be
   explicitly excluded in a path setup.

   This document specifies new subobjects to include or exclude domains
   during path setup where domain is a collection of network elements
   within a common sphere of address management or path computational
   responsibility (such as an Interior Gateway Protocol (IGP) area or an
   Autonomous System (AS)).  Note that the use of AS as an abstract node
   representing domain is already defined in existing RSVP-TE
   specefications, albeit with a 2-Byte AS number.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 2, 2015.





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Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Subobjects for Domains  . . . . . . . . . . . . . . . . . . .   4
     3.1.  Domains . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Explicit Route Object (ERO)'s Subobjects  . . . . . . . .   5
       3.2.1.  Autonomous system . . . . . . . . . . . . . . . . . .   6
       3.2.2.  IGP Area  . . . . . . . . . . . . . . . . . . . . . .   6
       3.2.3.  Mode of Operation . . . . . . . . . . . . . . . . . .   7
     3.3.  Exclude Route Object (XRO)'s Subobjects . . . . . . . . .   8
       3.3.1.  Autonomous system . . . . . . . . . . . . . . . . . .   8
       3.3.2.  IGP Area  . . . . . . . . . . . . . . . . . . . . . .   8
       3.3.3.  Mode of Operation . . . . . . . . . . . . . . . . . .   9
     3.4.  Explicit Exclusion Route Subobject  . . . . . . . . . . .   9
   4.  Interaction with Path Computation Element (PCE) . . . . . . .   9
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
     5.1.  New Subobjects  . . . . . . . . . . . . . . . . . . . . .  10
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  13
     A.1.  Inter-Area LSP Path Setup . . . . . . . . . . . . . . . .  13
     A.2.  Inter-AS LSP Path Setup . . . . . . . . . . . . . . . . .  14
       A.2.1.  Example 1 . . . . . . . . . . . . . . . . . . . . . .  14
       A.2.2.  Example 2 . . . . . . . . . . . . . . . . . . . . . .  15







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1.  Introduction

   The RSVP-TE specification [RFC3209] and the GMPLS extensions to RSVP-
   TE [RFC3473] allow abstract nodes and resources to be explicitly
   included in a path setup using the Explicit Route Object (ERO).

   Further Exclude Routes extensions [RFC4874] allow abstract nodes or
   resources to be excluded from the whole path using the Exclude Route
   object (XRO).  To exclude certain abstract nodes or resources between
   a specific pair of abstract nodes present in an ERO, a Explicit
   Exclusion Route Subobject (EXRS) is used.

   [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 Label Switched Path (LSP).  It further
   defines a subobject for AS, but with a 2-Byte AS number only.

   This document extends the notion of abstract nodes by adding new
   subobjects for IGP Areas and 4-byte AS numbers (as per [RFC6793]).
   These subobjects MAY be included in Explicit Route Object (ERO),
   Exclude Route Object (XRO) or Explicit Exclusion Route Subobject
   (EXRS).

   In case of per-domain path computation [RFC5152], where the full path
   of an inter-domain TE LSP cannot be or is not determined at the
   ingress node, and signaling message may use domain identifiers.  The
   use of these new subobjects is illustrated in Appendix A.

   Further, the domain identifier may simply act as delimiter to specify
   where the domain boundary starts and ends.

   This is a companion document to Path Computation Element Protocol
   (PCEP) extensions for the domain sequence [PCE-DOMAIN].

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.  Terminology

   The following terminology is used in this document.

   AS:  Autonomous System.

   Domain:  As per [RFC4655], any collection of network elements within
      a common sphere of address management or path computational



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      responsibility.  Examples of domains include Interior Gateway
      Protocol (IGP) areas and Autonomous Systems (ASs).

   ERO:  Explicit Route Object

   EXRS:  Explicit Exclusion Route Subobject

   IGP:  Interior Gateway Protocol.  Either of the two routing
      protocols, Open Shortest Path First (OSPF) or Intermediate System
      to Intermediate System (IS-IS).

   IS-IS:  Intermediate System to Intermediate System.

   OSPF:  Open Shortest Path First.

   PCE:  Path Computation Element.  An entity (component, application,
      or network node) that is capable of computing a network path or
      route based on a network graph and applying computational
      constraints.

   PCEP:  Path Computation Element Protocol.

   RSVP:  Resource Reservation Protocol

   TE LSP:  Traffic Engineering Label Switched Path.

   XRO:  Exclude Route Object

3.  Subobjects for Domains

3.1.  Domains

   [RFC4726] and [RFC4655] define domain as a separate administrative or
   geographic environment within the network.  A domain may be further
   defined as a zone of routing or computational ability.  Under these
   definitions a domain might be categorized as an AS or an IGP area.

   As per [RFC3209], an abstract node is a group of nodes whose internal
   topology is opaque to the ingress node of the LSP.  Using this
   concept of abstraction, an explicitly routed LSP can be specified as
   a sequence of IP prefixes or a sequence of Autonomous Systems.  In
   this document we extend the notion to include IGP area and 4-Byte AS
   number.

   The sub-objects MAY appear in RSVP-TE, notably in -






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   o  Explicit Route Object (ERO): As per [RFC3209], an explicit route
      is a particular path in the network topology including abstract
      nodes (domains).

   o  Exclude Route Object (XRO): As per [RFC4874], an exclude route
      identifies a list of abstract nodes (domains) that should not be
      traversed along the path of the LSP being established.

   o  Explicit Exclusion Route Subobject (EXRS): As per [RFC4874], used
      to specify exclusion of certain abstract nodes between a specific
      pair of nodes.  EXRS are a subobject carried inside the ERO.
      These subobjects are used to specify the domains that must be
      excluded between two abstract nodes.

3.2.  Explicit Route Object (ERO)'s Subobjects

   As stated in [RFC3209], an explicit route is a particular path in the
   network topology.  In addition to the ability to identify specific
   nodes along the path, an explicit route can identify a group of nodes
   (abstract nodes) that must be traversed along the path.

   Some subobjects are defined in [RFC3209], [RFC3473], [RFC3477],
   [RFC4874] and [RFC5553] but new subobjects related to domains are
   needed.

   The following subobject types are used in ERO.

                Type   Subobject
                 1     IPv4 prefix
                 2     IPv6 prefix
                 3     Label
                 4     Unnumbered Interface ID
                 32    Autonomous system number (2 Byte)
                 33    Explicit Exclusion (EXRS)
                 34    SRLG
                 64    IPv4 Path Key
                 65    IPv6 Path Key

   This document extends the above list to support 4-Byte AS numbers and
   IGP Areas.

                Type   Subobject
                 TBD   Autonomous system number (4 Byte)
                 TBD   OSPF Area id
                 TBD   ISIS Area id






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3.2.1.  Autonomous system

   [RFC3209] already defines 2-Byte AS number.

   To support 4-Byte AS numbers as per [RFC6793], the following
   subobject is defined:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |L|    Type     |     Length    |         Reserved              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          AS-ID (4 bytes)                      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   L: The L bit is an attribute of the subobject as defined in
      [RFC3209].

   Type:  (TBA by IANA) indicating a 4-Byte AS Number.

   Length:  8 (Total length of the subobject in bytes).

   Reserved:  Zero at transmission, ignored at receipt.

   AS-ID:  The 4-Byte AS Number.  Note that if 2-Byte AS numbers are in
      use, the low order bits (16 through 31) should be used and the
      high order bits (0 through 15) should be set to zero.

3.2.2.  IGP Area

   Since the length and format of Area-id is different for OSPF and
   ISIS, the following two subobjects are defined:

   For OSPF, the area-id is a 32 bit number.  The subobject is encoded
   as follows:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |L|    Type     |     Length    |         Reserved              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    OSPF Area Id (4 bytes)                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   L: The L bit is an attribute of the subobject as defined in
      [RFC3209].




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   Type:  (TBA by IANA) indicating a 4-Byte OSPF Area ID.

   Length:  8 (Total length of the subobject in bytes).

   Reserved:  Zero at transmission, ignored at receipt.

   OSPF Area Id:  The 4-Byte OSPF Area ID.

   For IS-IS, the area-id is of variable length and thus the length of
   the subobject is variable.  The Area-id is as described in IS-IS by
   ISO standard [ISO10589].  The subobject is encoded as follows:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |L|    Type     |     Length    |  Area-Len     |  Reserved     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     //                        IS-IS Area ID                        //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   L: The L bit is an attribute of the subobject as defined in
      [RFC3209].

   Type:  (TBA by IANA) indicating IS-IS Area ID.

   Length:  Variable.  As per [RFC3209], the total length of the
      subobject in bytes, including the L, Type and Length fields.  The
      Length MUST be at least 4, and MUST be a multiple of 4.

   Area-Len:  Variable (Length of the actual (non-padded) IS-IS Area
      Identifier in octets; Valid values are from 2 to 11 inclusive).

   Reserved:  Zero at transmission, ignored at receipt.

   IS-IS Area Id:  The variable-length IS-IS area identifier.  Padded
      with trailing zeroes to a four-byte boundary.

3.2.3.  Mode of Operation

   The new subobjects to support 4-Byte AS and IGP (OSPF / ISIS) Area
   MAY also be used in the ERO to specify an abstract node (a group of
   nodes whose internal topology is opaque to the ingress node of the
   LSP).

   All the rules of processing (for example Next Hop Selection, L bit
   processing, unrecognized subobjects etc) are as per the [RFC3209].



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3.3.  Exclude Route Object (XRO)'s Subobjects

   As stated in [RFC4874], the exclude route identifies a list of
   abstract nodes that should not be traversed along the path of the LSP
   being established.

   Some subobjects are defined in [RFC3209], [RFC3477], [RFC4874] and
   [RFC6001] but new subobjects related to domains are needed.

   The following subobject types are used in XRO.


                Type   Subobject
                 1     IPv4 prefix
                 2     IPv6 prefix
                 3     Label
                 4     Unnumbered Interface ID
                 32    Autonomous system number (2 Byte)
                 34    SRLG

   This document extends the above list to support 4-Byte AS numbers and
   IGP Areas.

                Type   Subobject
                 TBD   Autonomous system number (4 Byte)
                 TBD   OSPF Area id
                 TBD   ISIS Area id

3.3.1.  Autonomous system

   [RFC3209] and [RFC4874] already define a 2-Byte AS number.

   To support 4-Byte AS numbers as per [RFC6793], a subobject is with
   the same format as defined in Section 3.2.1 with following
   difference:

   The meaning of the L bit (similar to [RFC4874]).

   0: indicates that the abstract node (AS) specified MUST be excluded.

   1: indicates that the abstract node (AS) specified SHOULD be avoided.

3.3.2.  IGP Area

   Since the length and format of Area-id is different for OSPF and
   ISIS, the following two subobjects are defined:





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   For OSPF, the area-id is a 32 bit number.  Subobjects for OSPF and
   IS-IS are of the same format as defined in Section 3.2.2 with
   following difference:

   The meaning of the L bit (similar to [RFC4874]).

   0: indicates that the abstract node (OSPF or IS-IS Area) specified
      MUST be excluded.

   1: indicates that the abstract node (OSPF or IS-IS Area) specified
      SHOULD be avoided.

3.3.3.  Mode of Operation

   The new subobjects to support 4-Byte AS and IGP (OSPF / ISIS) Area
   MAY also be used in the XRO to specify exclusion of an abstract node
   (a group of nodes whose internal topology is opaque to the ingress
   node of the LSP).

   All the rules of processing are as per the [RFC4874].

3.4.  Explicit Exclusion Route Subobject

   As per [RFC4874], the Explicit Exclusion Route defines 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.
   EXRS is an ERO subobject that contains one or more subobjects of its
   own, called EXRS subobjects.

   The EXRS subobject may carry any of the subobjects defined for XRO,
   thus the new subobjects to support 4-Byte AS and IGP (OSPF / ISIS)
   Area MAY also be used in the EXRS.  The meanings of the fields of the
   new XRO subobjects are unchanged when the subobjects are included in
   an EXRS, except that scope of the exclusion is limited to the single
   hop between the previous and subsequent elements in the ERO.

   All the rules of processing are as per the [RFC4874].

4.  Interaction with Path Computation Element (PCE)

   The domain subobjects to be used in Path Computation Element Protocol
   (PCEP) are referred to in [PCE-DOMAIN].  Note that the new domain
   subobjects follow the principle that subobjects used in PCEP
   [RFC5440] are identical to the subobjects used in RSVP-TE and thus
   are interchangeable between PCEP and RSVP-TE.






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5.  IANA Considerations

5.1.  New Subobjects

   IANA registry: RSVP PARAMETERS

   Subsection: Class Names, Class Numbers, and Class Types

   IANA is requested to add further subobjects to the existing entry
   for:

          20    EXPLICIT_ROUTE
          232   EXCLUDE_ROUTE

          Subobject Type                          Reference
          TBA       4-Byte AS number              [This I.D.]
          TBA       OSPF Area ID                  [This I.D.]
          TBA       IS-IS Area ID                 [This I.D.]


6.  Security Considerations

   Security considerations for MPLS-TE and GMPLS signaling are covered
   in [RFC3209] and [RFC3473].  This document does not introduce any new
   messages or any substantive new processing, and so those security
   considerations continue to apply.

   The route exclusion security consideration are covered in [RFC4874]
   and continue to apply.

7.  Acknowledgments

   We would like to thank Adrian Farrel, Lou Berger, George Swallow,
   Chirag Shah, Reeja Paul Sandeep Boina and Avantika for their useful
   comments and suggestions.

8.  References

8.1.  Normative References

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

8.2.  Informative References

   [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.



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

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

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655, August 2006.

   [RFC4726]  Farrel, A., Vasseur, J., and A. Ayyangar, "A Framework for
              Inter-Domain Multiprotocol Label Switching Traffic
              Engineering", RFC 4726, November 2006.

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

   [RFC5152]  Vasseur, JP., Ayyangar, A., and R. Zhang, "A Per-Domain
              Path Computation Method for Establishing Inter-Domain
              Traffic Engineering (TE) Label Switched Paths (LSPs)", RFC
              5152, February 2008.

   [RFC5440]  Vasseur, JP. and JL. Le Roux, "Path Computation Element
              (PCE) Communication Protocol (PCEP)", RFC 5440, March
              2009.

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

   [RFC6001]  Papadimitriou, D., Vigoureux, M., Shiomoto, K., Brungard,
              D., and JL. Le Roux, "Generalized MPLS (GMPLS) Protocol
              Extensions for Multi-Layer and Multi-Region Networks (MLN/
              MRN)", RFC 6001, October 2010.

   [RFC6793]  Vohra, Q. and E. Chen, "BGP Support for Four-Octet
              Autonomous System (AS) Number Space", RFC 6793, December
              2012.

   [PCE-DOMAIN]
              Dhody, D., Palle, U., and R. Casellas, "Standard
              Representation Of Domain Sequence. (draft-ietf-pce-pcep-
              domain-sequence)", July 2014.






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   [ISO10589]
              ISO, "Intermediate system to Intermediate system routing
              information exchange protocol for use in conjunction with
              the Protocol for providing the Connectionless-mode Network
              Service (ISO 8473)", ISO/IEC 10589:2002, 1992.














































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Appendix A.  Examples

   These examples are for illustration purposes only, to show how the
   new subobjects may be encoded.

A.1.  Inter-Area LSP Path Setup

   In an inter-area LSP path setup where the ingress and the egress
   belong to different IGP areas within the same AS, the domain
   subobjects MAY be represented using an ordered list of IGP area
   subobjects in an ERO.

                                   D2 Area D
                                   |
                                   |
                                   D1
                                   |
                                   |
                           ********BD1******
                           *       |       *
                           *       |       *                Area C
     Area A                *       |       *
                           *       |       *
     Ingress------A1-----ABF1------B1------BC1------C1------Egress
                         / *       |       *
                       /   *       |       *
                     /     * Area  | B     *
                   F1      *       |       *
                 /         ********BE1******
               /                   |
             /                     |
            F2                     E1
                                   |
    Area F                         |
                                   E2 Area E

     * All IGP Area in one AS (AS 100)

                Figure 1: Domain Corresponding to IGP Area

   As per Figure 1, the signaling at Ingress MAY be -

   ERO:(A1, ABF1, Area B, Area C, Egress); or

   ERO:(A1, ABF1, AS 100, Area B, AS 100, Area C, Egress).






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   The AS subobject is optional and it MAY be skipped.  An RSVP-TE
   implementation should be able to understand both notations and there
   is no change in the processing rules as mentioned in [RFC3209].

A.2.  Inter-AS LSP Path Setup

A.2.1.  Example 1

   In an inter-AS LSP path setup where the ingress and the egress belong
   to different AS, the domain subobjects MAY be represented using an
   ordered list of AS subobjects in an ERO.


              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 AS have one area (area 0)

                   Figure 2: Domain Corresponding to AS

   As per Figure 2, the signaling at Ingress MAY be -

   ERO:(A1, A2, AS B, AS C, Egress); or

   ERO:(A1, A2, AS B, Area 0, AS C, Area 0, Egress).

   Each AS has a single IGP area (area 0), Area subobject is optional
   and it MAY be skipped as AS is enough to uniquely identify a domain.
   An RSVP-TE implementation should be able to understand both notations
   and there is no change in the processing rules as mentioned in
   [RFC3209].





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   Note that to get a domain disjoint path, the ingress may also signal
   the backup path with -

   XRO:(AS B)

A.2.2.  Example 2

   As shown in Figure 3, where AS 200 is made up of multiple areas, the
   signaling MAY include both AS and Area subobject to uniquely identify
   a domain.









































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                 Ingress         *
                    |          *
                    |        *
                    X1     *
                    |  \ *
                    |  * \
                    |*     \
                  * |        \    Inter-AS
         AS 100 *   |          \  Link
              *     |            \
            *       |              \
          *         |                \
                    |                 D2 Area D
         AS 200     |                 |
                    |                 |
              Inter |                 D1
                -AS |                 |
               Link |                 |
                    A3        ********BD1******
                    |         *       |       *
                    |         *       |       *                Area C
                    |  Area A *       |       *
                    |         *       |       *
            A2------A1------AB1------B1------BC1------C1------Egress
                              *       |       *
                              *       |       *
                              *       |       *
                              * Area  | B     *
                              ********BE1******
                                      |
                                      |
                                      E1
                                      |
                                      |
                                      E2 Area E


               Figure 3: Domain Corresponding to AS and Area

   As per Figure 3, the signaling at Ingress MAY be -

   ERO:(X1, AS 200, Area D, Area B, Area C, Egress).

   The combination of both an AS and an Area uniquely identifies a
   domain, note that an Area domain identifier always belongs to the
   previous AS that appears before it or, if no AS subobjects are
   present, it is assumed to be the current AS.  Also note that there




Dhody, et al.            Expires January 2, 2015               [Page 16]


Internet-Draft                DOMAIN SUBOBJ                    July 2014


   are no changes in the processing rules as mentioned in [RFC3209] with
   respect to subobjects.

Authors' Addresses

   Dhruv Dhody
   Huawei Technologies
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: dhruv.ietf@gmail.com


   Udayasree Palle
   Huawei Technologies
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: udayasree.palle@huawei.com


   Venugopal Reddy Kondreddy
   Huawei Technologies
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: venugopalreddyk@huawei.com


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

   EMail: ramon.casellas@cttc.es












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