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Versions: (draft-lee-pce-lsp-stitching-hpce) 00 01 02

Path Computation Element Working Group                         O. Dugeon
Internet-Draft                                                 J. Meuric
Intended status: Standards Track                                  Orange
Expires: April 30, 2018                                 October 27, 2017


            PCEP Extension for Stateful Inter-Domain Tunnels
                draft-dugeon-pce-stateful-interdomain-00

Abstract

   The Path Computation Element (PCE) working group (WG) has produced a
   set of RFCs to standardize the behavior of the Path Computation
   Element as a tool to help MPLS-TE, GMPLS LSP tunnels and Segment
   Routing paths placement.  This also include the ability to compute
   inter-domain LSPs or Segment Routing path following a distributed or
   hierarchical approach.  In complement to the original stateless mode,
   a stateful mode has been added.  In particular, the new PCInitiate
   message allows a PCE to directly ask a PCC to setup an MPLS-TE, GMPLS
   LSP tunnel or a Segment Routing path.  However, once computed, the
   inter-domain LSPs or Segment Routing path are hard to setup in the
   underlying network.  Especially, in operational network, RSVP-TE
   signaling is not enable between AS border routers.  But, such RSVP-TE
   signaling is mandatory to setup contiguous LSP tunnels or to stitch
   or nest independent LSP tunnels to form the end-to-end inter-domain
   paths.  This document proposes to combine a Backward Recursive or
   Hierarchical method with PCInitiate message to setup independent
   paths per domain, and combine these different paths together in order
   to operated them as end-to-end inter-domain paths without the need of
   signaling session between AS border routers.  A new Stitching Label
   is defined and new LSP-TYPE code points are considered for that
   purpose.

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 RFC 2119 [RFC2119].

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 https://datatracker.ietf.org/drafts/current/.



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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on April 30, 2018.

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Table of Contents

   1.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  General assumptions . . . . . . . . . . . . . . . . . . .   4
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   5
   2.  Stitching Label . . . . . . . . . . . . . . . . . . . . . . .   7
     2.1.  Definition  . . . . . . . . . . . . . . . . . . . . . . .   7
     2.2.  Inter-domain LSP-TYPE . . . . . . . . . . . . . . . . . .   7
   3.  Backward Recursive PCInitiate procedure . . . . . . . . . . .   8
     3.1.  Mode of operation . . . . . . . . . . . . . . . . . . . .   8
     3.2.  Example . . . . . . . . . . . . . . . . . . . . . . . . .  10
     3.3.  Inter-domain LSP setup procedure completion failure . . .  12
   4.  Hierarchical PCInitiate procedure . . . . . . . . . . . . . .  13
     4.1.  Mode of operation . . . . . . . . . . . . . . . . . . . .  13
     4.2.  Inter-domain LSP setup procedure completion failure . . .  15
   5.  Inter-domain LSP Management . . . . . . . . . . . . . . . . .  16
     5.1.  Identification of inter-domain tunnels  . . . . . . . . .  16
     5.2.  Inter-domain LSP management . . . . . . . . . . . . . . .  16
     5.3.  Modification of inter-domain LSP  . . . . . . . . . . . .  17
     5.4.  Removal of inter-domain LSP . . . . . . . . . . . . . . .  17
   6.  Applicability . . . . . . . . . . . . . . . . . . . . . . . .  18
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
     7.1.  LSP-TYPE values . . . . . . . . . . . . . . . . . . . . .  19
     7.2.  PCEP-Error Object . . . . . . . . . . . . . . . . . . . .  19
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  19



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   10. Disclaimer  . . . . . . . . . . . . . . . . . . . . . . . . .  20
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  20
     11.2.  Informative References . . . . . . . . . . . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22

1.  Problem Statement

   Looking to the different RFCs that describe the PCE architecture and
   in particular PCE based architecture [RFC4655], PCE protocol
   [RFC5440], BRPC [RFC5441] and H-PCE [RFC6805], the Path Computation
   Element (PCE) is able to compute inter-domain paths in complement to
   intra-domain computation.  Such inter-domain paths could then serve
   as the Explicit Route Object input for the RSVP-TE signaling to setup
   the LSPs tunnel within the underlying network.  Three kinds of inter-
   domain paths could be established:

   o  Contiguous LSPs ([RFC3209] and [RFC3473]): The RSVP-TE signaling
      crosses the boundary between two domains, e.g. between two AS
      Border Routers (ASBRs) as if they were two routers of the same
      domain.  This kind of tunnel is not recommended mostly for
      security and scalability purpose.  In addition, the initiating
      domain imposes huge constraints on subsequent domains, because
      they undergo the tunnel request without being able to control it.

   o  Stitching LSPs ([RFC5150]): Each domain establishes in its own
      network the corresponding part of the inter-domain path
      independently.  Then, a second end-to-end RSVP-TE Path message is
      sent by the initiating domain to stitch the different tunnel parts
      to form the inter-domain path.  In fact, this second RSVP-TE Path
      message is used by border nodes to exchange the label that must be
      used by the previous domain to send the traffic in order that the
      MPLS packets follow the next LSP tunnel in the following domain.
      These labels are conveyed in the RSVP-TE Resv message.

   o  Nesting LSPs ([RFC4206]): This is similar to the stitching mode
      but, this time, with the possibility to setup tunnel hierarchy.
      For example, an LSP tunnel between two edge domains crossing a
      transit domain could be carried over a tunnel of a higher level in
      the transit domain.  Again, a second end-to-end RSVP-TE Path
      message is sent from the source to the destination.  Labels that
      must be used by the ASBRs of transit domains to identify flows to
      be nested are carried by the RSVP-TE Resv message.

   In all case, RSVP-TE signaling must be exchanged between the
   different domains.  However, from an operational point of view,
   looking to different networks under the responsibility of different
   administrative entities, only BGP sessions are setup and configured



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   between ASBRs.  Technologically speaking, this is possible and many
   RFCs describe how to use RSVP-TE for inter-domain.  But, due to
   security, scalability, management and contract constraints, RSVP-TE
   is not exposed at the network boundary.  To circumvent some of the
   security issues, RSVP-TE can be carried inside an IPsec tunnel
   between ASBRs, but, this does not eliminate the scalability aspect
   nor the constraints imposed by setting up inter-domain paths.

   The purpose of this memo is to take the benefit of PCE Stateful
   [RFC8231] and PCE Initiated [I-D.ietf-pce-pce-initiated-lsp] modes to
   stitch or nest inter-domain paths directly using PCEP between
   domains' PCEs instead of using RSVP-TE signaling at the inter-domain,
   while keeping each operator free to independently setup their
   respective part of the inter-domain paths.  PCInitiated message is
   used in a Backward Recursive way like the PCReq message in BRPC
   [RFC5441], to recursively setup the end-to-end tunnel.  PCRep message
   is used to automatically stitch or nest the different local LSP
   tunnels.  And, PCRep in conjunction of PCUpd messages are used to
   maintain, modify and remove inter-domain paths.  This method is also
   applicable to Segment Routing to build inter-domain segment paths.

1.1.  General assumptions

   In the rest of this document, we used the same references as per BRPC
   [RFC5441] and make the following set of assumptions (see figure
   below):

   o  Domain refers to an IGP area or an Autonomous System (AS).

   o  Inter-domain path is used to refer to a path that cross two or
      more different domains as defined previously,

   o  At least, one PCE is deployed in each domain.  These PCE are all
      stateful active capable and could request to enforce LSP tunnels
      in their respective domain by means of PCInitiate messages.

   o  LSRs, including border nodes, are PCC enable and support stateful
      active mode.  PCEP sessions is established between these routers
      and their domains' PCE.

   o  Each PCE establishes a PCEP session with its respective neighbor
      domain's PCE.  The way a PCE discover its neighboring PCE is out
      of scope of this draft.  These information could be fulfill
      administratively or automatically discovered through, for example
      per draft 'BGP Extensions for Path Computation Element (PCE)
      Discovery' [I-D.dong-pce-discovery-proto-bgp],





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   o  PCEs are able to compute and end-o-end path as per BRPC procedure
      [RFC5441].

   o  Tunnels refer to LSPs setup by mean of RSVP-TE or Segment Path in
      a Segment Routing network.

                   +----------------+          +----------------+
                   |  Domain (B)    |          |  Domain (C)    |
                   |                |          |                |
                   |        /-------|---PCEP---|--------\       |
                   |       /        |          |         \      |
                   |   [PCE-B]      |          |       [PCE-C]  |
                   |    /         (BN)<------>(BN)              |
                   |   /            |  Inter   |                |
                   +---|--(BN)------+  Domain  +----------------+
                       |    ^          Link
                     PCEP   |
                       |    | Inter-domain Link
                       |    v
                   +---|--(BN)------+
                   |   |            |
                   |   | Domain (A) |
                   |   \            |
                   | [PCE-A]        |
                   |                |
                   |                |
                   +----------------+



         Example of the representation of 3 domains with 3 PCEs

1.2.  Terminology

   ABR: Area Border Routers.  Routers used to connect two IGP areas
   (areas in OSPF or levels in IS-IS).

   ASBR: Autonomous System Border Router.  Router used to connect
   together ASes of the same or different service providers via one or
   more inter-AS links.

   AS: Autonomous System

   Border Node (BN): a boundary node is either an ABR in the context of
   inter-area Traffic Engineering or an ASBR in the context of inter-AS
   Traffic Engineering.





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   Domains: Autonomous System (AS) or IGP Area.  An Autonomous System is
   composed by one or more IGP area.

   BNe(i): Entry BN of domain(i) connecting domain(i-1) to domain(i)
   along a determined sequence of domains.  Multiple entry BN(i) could
   be used to connect domain(i-1) to domain(i).

   BNo(i): Output BN of domain(i) connecting domain(i) to domain(i+1)
   along a determined sequence of domains.  Multiple exit BN(i) could be
   used to connect domain(i) to domain(i+1).

   Inter-domain path: A path that crosses two or more domains through a
   pair of Border Node (BNo, BNe).

   Local LSP tunnel: A LSP tunnel that do not cross a domain.  It is
   setup between entry BNe to output BNo, any source to output BNo or
   entry BNe to any destination of the same domain.  This LSP could be
   enforce by means of RSVP-TE signaling or Segment Routing labels
   stack.

   Local LSP tunnel(i): A local LSP tunnel of domain(i)

   IGP-TE: Interior Gateway Protocol with Traffic Engineering support.
   Both OSPF-TE and IS-IS-TE are identified in this category.

   Stitching Label (SL): A dedicated label that is used to stitch two
   RSVP-TE tunnels or two Segment Routing paths.

   SL(i): A Stitching Label that link domain(i) to domain(i-1).

   LK(i): A Link that connect BNo(i) to BNe(i+1).  Note that BNo(i)
   could be connected to BNe(i+1) by more than one link.  LK(i) serves
   to identify which of the multiple links will be used for the inter-
   domain LSP setup.

   PLSP-ID(i): A PLSP-ID that identify the local tunnel part of an
   inter-domain tunnel in the domain(i).

   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.

   PCE(i) is a PCE with the scope of domain(i).








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2.  Stitching Label

   This section introduce the concept of Stitching Label that allows
   stitching and nesting of local LSP tunnels in order to form inter-
   domain path that cross several different domains.

2.1.  Definition

   The operation of stitch or nest a local LSP tunnel(i) to a local LSP
   tunnel(i+1) in order to form and inter-domain path simply consist in
   defining the label that the output BNo(i) will use to send its
   traffic to the entry BNe(i+1).  Indeed, the entry BNe(i+1) needs to
   identify the incoming traffic i.e. IP packets, in order to know if
   this traffic must follow the local LSP tunnel(i+1) or not.
   Forwarding Equivalent Class (FEC) could be used for that purpose.
   But, when stitching or nesting tunnels, the FEC is reduce to the
   incoming label that the entry BNe(i+1) as chosen for the local LSP
   tunnel(i+1).

   In this memo, we introduce the named of 'Stitching Label (SL)' to
   designate this label.  Such label is usually exchange between output
   BNo(i) and entry BNe(i+1) with the RSVP-TE signaling.  But, as we
   want to avoid to use RSVP-TE signaling due to operational
   constraints, this Stitching Label will be convey by PCEP protocol.
   In fact, the Explicit Route Object (ERO) and the Record Route Object
   (RRO) are defined in order to transport this Stitching Label in the
   RSVP-TE signaling.  As PCEP protocol used RSVP-TE Objects, and in
   particular the ERO and RRO, it is able to convey the Stitching Label
   without any modification of the PCEP protocol nor the PCE or RSVP-TE
   Objects.

   As per RFC4003 [RFC4003], the Stitching Label will be convey as a
   companion of an IP address.  In our case, this is one of the IP
   address of the link LK(i) which connects BNo(i) to BNe(i+1) and
   carries the traffic from the domain(i) to domain(i+1).  It is left to
   implementation to select which of the two IP address of the link
   LK(i) is used.

2.2.  Inter-domain LSP-TYPE

   However, even if PCEP could convey the Stitching Label, a PCC is not
   aware that a PCE requests or provides such label.  For that purpose,
   this memo propose to use the LSP-TYPE as defined in draft lsp setup
   type [I-D.ietf-pce-lsp-setup-type] with new values (See IANA section
   of this memo) defined as follow:

   o  TBD1: Inter-Domain Traffic engineering end-to-end path is setup
      using Backward Recursive or Hierarchical method.  This new LSP-



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      TYPE value MUST be set in a PCInitiate messages sends by a PCE(i)
      to its neighbor PCE(i+1) in the Backward Recursive method or by
      the Parent PCE to the Child PCE(i) to initiate a new inter-domain
      path.  In turn, neighbor PCE(i+1) or Child PCE(i) MUST return a
      Stitching Label SL with the IP address of the associated link in
      the RRO of the PCRpt message to PCE(i) or Parent PCE.

   o  TBD2: Inter-Domain Traffic engineering local path is setup using
      RSVP-TE.  This new LSP-TYPE value MUST be set in the PCInitiate
      message sends by a PCE(i) requesting to a PCC of domain(i) to
      initiate a new local LSP tunnel(i) which is part of an inter-
      domain path.  This LSP-TYPE value MUST be used by the PCE(i) only
      after receiving a PCInitiate message with an LSP-TYPE equal to
      TBD1 from a neighbor PCE(i+1) in the Backward Recursive method or
      Parent PCE in the Hierarchical method.  In turn, the PCC of
      domain(i) MUST return a Stitching Label SL with the IP address of
      associated link in the RRO of the PCRpt message.

   o  TBD3: Inter-Domain Traffic engineering local path is setup using
      Segment Routing.  This new LSP-TYPE value MUST be set in the
      PCInitiate message sends by a PCE(i) requesting to a PCC of
      domain(i) to initiate a new Segment Routing path which is part of
      and inter-domain Segment Routing path.  This LSP-TYPE value MUST
      be used by the PCE(i) only after receiving a PCInitiate message
      with an LSP-TYPE equal to TBD1 from a neighbor PCE(i+1).  In turn,
      the PCC MUST return a Stitching Label SL with the IP address of
      the associated link in the RRO of the PCRpt message.

3.  Backward Recursive PCInitiate procedure

   This section describes how to setup inter-domain paths than cross
   several different domains by using a Backward Recursive method which
   is compatible to inter-domain path computation by means of the BRPC
   procedure as describe in RFC5441 [RFC5441].

3.1.  Mode of operation

   This section describes how PCInitiate and PCRpt messages are combined
   between PCE in order to setup inter-domain paths between a source
   domain(1) to a destination domain(n).  S and D are respectively the
   source and destination of the inter-domain path.  Domain(1) and
   domain(n) are different and connected through 0 or more intermediate
   domains denoted domain(i) with i = (2, n-1).  Domains are directly
   connected when n = 2.

   First, the PCE(S) run standard BRPC algorithm as per RFC5441
   [RFC5441] with its neighbor PCEs in order to compute the inter-domain
   path from S to D, where S and D are respectively a node in the



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   domain(1) and domain(n).  Path Key confidentiality as per RFC5520
   [RFC5520] MAY be used to obfuscate the detailed ERO of the different
   domains(i).  The resulting ERO is of the form {S, PKS(1), BNo(1),
   ..., BNe(i), PKS(i), BNo(i), ..., BNe(n), PKS(n), D}. As subsequent
   domains are not aware about the final computed ERO in case of
   multiple VSPT, the final computed ERO MUST be send in the PCInitiate
   message to indicate to the subsequent PCEs which solution has been
   finally chosen.

   The complete procedure follow the different steps described below:

   Steps 1: Initialization

   Once ERO(S, D) computed, PCE(1) sends a PCInitiate message to PCE(2)
   containing and ERO equal to {S, PKS(1), BNo(1), ..., BNe(i), PKS(i),
   BNo(i), ..., BNe(n), PKS(n), D}, LSP-TYPE = TBD1 and End-Points
   Object = (S, D).  The ERO corresponds to the one PCE(1) as received
   from PCE(2) during the BRPC process.  In case of multiple EROs, i.e.
   VSPT > 1, PCE(1) has chosen one of them and used the selected one for
   the PCInitiate message.  PKS(i) could be replaced by the full ERO
   description if Path Key is not used by PCE(i).

   When PCE(i) receives a PCInitiate message from domain(i-1) with LSP-
   TYPE = TBD1 and ERO = {BNe(i), PKS(i), BNo(i), ..., BNe(n), PKS(n),
   D)}, it forwards the PCInitiate message to PCE(i+1) once remove its
   {BNe(i), PKS(i), BNo(i)} part from the ERO.  All PCE(i) propagate the
   PCInitiate message to PCE(i+1) up to PCE(n) i.e. to the domain(n).

   Steps 2: Actions taken at the destination domain(n) by PCE(n)

   When PCInitiate message propagation reach the destination domain(n),
   PCE(n) retrieves the ERO from the PKS(n) if necessary and sends to
   BNe(n) a PCInitiate message with the ERO(n) = {BNe(n), ..., D}, LSP-
   TYPE= TBD2 and End-Points Object = {BN(n), D} in order to inform the
   PCC BNe(n) that this local LSP tunnel(n) is part of an inter-domain
   path.  When the PCC BNe(n) received the PCInitiate message from its
   PCE(n), it setup the local LSP tunnels from entry BNe(n) to D by
   means of RSVP-TE signaling with the given ERO(n).  Once the tunnel
   setup, it chooses a free label for the Stitching Label SL(n) and add
   a new entry in its MPLS LFIB with this SL(n) label.  Then, it sends a
   PCRpt message to its PCE(n) with an RRO equal to {[LK(n), SL(n)],
   RRO(n)} and PLSP-ID(n).  Once PCE(n) receives the PCRpt from the PCC
   BNe(n) with the RRO, PLSP-ID and LSP-TYPE = TBD2, it sends to the
   PCE(n-1) a PCRpt containing the RRO equal to {[LK(n), SL(n)]} and
   PLSP-ID(n).  PCE(n) MAY adds {BN(n), D} in the RRO as loose path.

   Steps i: Actions performed by all intermediate domains(i), for i = 2
   to n-1



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   1.  When the PCE(i) receives a PCRpt message from domain(i+1) with
       LSP-TYPE = TBD1, RRO = {[LK(i+1), SL(i+1)]} and PLSP-ID(i+1), it
       retrieves the ERO from the PKS(i) if necessary and sends to the
       PCC BNe(i) a PCInitiate message with ERO = {ERO(i), [LK(i+1),
       SL(i+1)]}, LSP-TYPE = TBD2 and End-Points Object = {BNe(i),
       BNo(i)} in order to inform the PCC BNe(i) that this local LSP
       tunnel(i) is part of an inter-domain path.

   2.  When the PCC BNe(i) received the PCInitiate message from its
       PCE(i), it setup the local LSP tunnels from BNe(i) to BNo(i) by
       means of RSVP-TE signaling with the given ERO(i).

   3.  When the BNo(i) receives an RSVP-TE Path message with an ERO =
       {x-1, [LK(i+1), SL(i+1)]} and End-Points Object = {BNe(i),
       BNo(i)}, it MUST install in its MPLS LFIB the SWAP instruction to
       label SL(i+1) with forward to LK(i+1) instead of the standard POP
       instruction.

   4.  Once the tunnel setup, it chooses a free label for the Stitching
       Label SL(i) and add a new entry in its MPLS LFIB with this SL(i)
       label.  Then, it sends a PCRpt message to its PCE(i) with an RRO
       equal to {[LK(i), SL(i)], RRO(i)} and PLSP-ID(i).

   5.  Once PCE(i) receives the PCRpt from the PCC BNe(i) with the RRO
       and LSP-TYPE = TBD2, it sends to the PCE(i-1) a PCRpt message
       containing the RRO equal to {[LK(i), SL(i)]} and the PLSP-ID(i).
       PCE(i) MAY adds {BNe(i), BNo(i)} in the RRO as loose path.

   Steps n: Actions performed at the source domain(1)

   Once PCE(1) received the PCRpt message from PCE(2) with the RRO
   containing the label SL(2), it sends a PCInitiate message to PCC node
   S with ERO equal to {ERO(1), [LK(2), SL(2)]}, LSP_TYPE = 0 and End-
   Points Object = {S, BNo(1)}. This time, the LSP_TYPE is equal to 0 as
   the PCC S does not need to return a Stitching Label SL i.e. it is the
   head-end of the inter-domain path.  Standard PCRpt message is sent
   back to PCE(1) by the PCC node S.

3.2.  Example

   In the figure below, two different domains S and D are interconnected
   through BN respectively BN-S and BN-D.  PE-S and PE-D are edge
   routers.  All routers in the figure are connected to their respective
   PCE through PCEP protocol.  In this example, PCE(S) would setup an
   inter-domain path between PE-S and PE-D acting as source and
   destination of the tunnel.  Intermediate routers between (PE-S, BN-
   S), (BN-D and PE-D) as well as RSVP-TE messages are not represented




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   to simplify the figure.  But they are all presents.  The following
   notation is used in the figure:

   o  PKS(D) = Path Key corresponding to the path from BN(D) to PE-D

   o  ERO(D) = Explicit Route Object corresponding to the path from
      BN(D) to PE-D retrieves from PKS(D)

   o  RRO(D) = Record Route Object of local LSP tunnel(D) from BN(D) to
      PE-D

   o  SL(D) = Stitching Label for local LSP tunnel from BN(D) to PE-D

   o  ERO(S) = Explicit Route Object corresponding to the path from PE-S
      to BN(S)

   o  RRO(S) = Record Route Object of local LSP tunnel(S) from PE-S to
      BN(S)

































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     PE-S      PCE-S                           BN-D      PCE-D
      |          |                              |          |
      |        [ -------- Standard BRPC exchange ------------]
      |          |                              |          |
      |          | PCInitiate(ERO={BN(D), PKS(D)}, LSP-TYPE = TBD1)
      |          | --------------------------------------> |
      |          |                              |          |
      |          |             PCInitiate(ERO = ERO(D), LSP-TYPE = TBD2)
      |          |                              | <------- |
      |          |                              |          |
      |          |         PCRpt(RRO = {SL(D), RRO(D)}, LSP-TYPE = TBD2)
      |          |                              |  ------> |
      |          |                              |          |
      |        PCRpt(RRO = {SL(D), PKS(D)}, LSP-TYPE = TBD1, PLSP-ID(D))
      |          | <-------------------------------------- |
      |          |                              |          |
      |  PCInitiate(ERO={ERO(S), SL(D), BN(D)}, LSP-TYPE = 0)
      | <------- |                              |          |
      |          |                              |          |
      |  PCRpt(RRO={RRO(S)}, LSP-TYPE = 0)      |          |
      | -------> |                              |          |
      |          |                              |          |

     +----------------------+                  +----------------------+
     |                      |                  |                      |
     |       +------+       |     PCEP         |       +------+       |
     | +---->|PCE(S)|<-------------------------------->|PCE(D)|       |
     | |     +------+       |                  |       +------+       |
     | |         ^          |                  |        ^  ^          |
     | |         |          |                  |        |  |          |
     | |PCEP     |          |                  |        |  |          |
     | |         |PCEP      |                  |   PCEP |  | PCEP     |
     | v         |          |                  |        |  |          |
   (PE-S)        +------> (BN-S) <---------> (BN-D)<----+  +----> (PE-D)
     |                      |  Inter-Domain    |                      |
     |     Domain (S)       |   Link           |   Domain (D)         |
     +----------------------+                  +----------------------+

    [--- LSP Tunnel (S) ---][---- SL label ----][--- LSP Tunnel (D) ---]

   Example of inter-domain path setup between two domains


3.3.  Inter-domain LSP setup procedure completion failure

   In case of error during LSP setup, PCRpt and or PCError messages MUST
   be used to signal the problem to the neighbor PCE domain backward.
   In particular, if new LSP-TYPE values defined in this memo are not



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   supported by the neighbor PCE or the PCC, the PCE, receptively the
   PCC, MUST return a PCErr message with Error-Type = 21 (Traffic
   engineering path setup error) and Error-Value = 1 (Unsupported path
   setup type) to its neighbor PCE.  If a PCE(i) receives a PCInitiate
   message from its peer PCE(i-1) without LSP-TYPE set to TBD1 or LSP-
   TYPE set to a value different from TBD1, it MUST return a PCErr
   message with Error-Type = 21 (Traffic engineering path setup error)
   and Error-Value = 1 (Unsupported path setup type) to its peer
   PCE(i-1).

   If a PCC or a PCE don't return an RRO or an RRO without the Stitching
   Label SL with the IP address of the associated link following a
   PCInitiate message with LSP-TYPE set to TBD1, the PCE MUST return a
   PCErr message with Error-Type = 21 (Traffic engineering path setup
   error) and Error-Value = TBD4 (No Mandatory Stitching Label is
   present in the RRO).

   In case of completion failure, the PCE(i) MUST propagate the PCErr
   message up to the PCE(1).  In turn, PCE(1) MUST send a PCInitate
   message (R flag set in the SRP Object as per draft pce initiated lsp
   [I-D.ietf-pce-pce-initiated-lsp]) to delete this inter-domain path to
   its neighbor PCEs.  PCE(i) MUST propagate the PCInitiate message and
   remove their local LSP tunnel by means of PCInitiate message to their
   PCC BNe(i) and send back PCRpt message to PCE(i-1).

   In case of error in domain(i+1), PCE(i) MAY add the AS number of
   domain(i+1) in the RRO to identify the faulty domain.

4.  Hierarchical PCInitiate procedure

   This section describes how to setup inter-domain paths than cross
   several different domains by using a Hierarchical method which is
   compatible to inter-domain path computation as describe in RFC6805
   [RFC6805].

4.1.  Mode of operation

   This section describes how PCInitiate and PCRpt messages are combined
   between PCE in order to setup inter-domain paths between a source
   domain(1) to a destination domain(n).  S and D are respectively the
   source and destination of the inter-domain path.  Domain(1) and
   domain(n) are different and connected through 0 or more intermediate
   domains denoted domain(i) with i = (2, n-1).  Domains are directly
   connected when n = 2.

   First, the Parent PCE contacts its Child PCE as per RFC6805 [RFC6805]
   in order to compute the inter-domain path from S to D, where S and D
   are respectively a node in the domain(1) and domain(n).  Path Key



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   confidentiality as per RFC5520 [RFC5520] MAY be used to obfuscate the
   detailed ERO of the different domains(i).  The resulting ERO is of
   the form (S, PKS(1), BNo(1), ..., BNe(i), PKS(i), BNo(i), ...,
   BNe(n), PKS(n), D).

   The complete procedure follow the different steps described below:

   Step 1: Initialization

   Parent PCE sens a PCInitiate message to with an ERO = {PKS(n)} and
   End-Points = {BNe(n), D}. Then, PCE(n) retrieves the ERO from the
   PKS(n) if necessary and sends to BNe(n) a PCInitiate message with the
   ERO(n) = {BNe(n), ..., D}, LSP-TYPE= TBD2 and End-Points Object =
   {BN(n), D} in order to inform the PCC BNe(n) that this local LSP
   tunnel(n) is part of an inter-domain path.  When the PCC BNe(n)
   received the PCInitiate message from its PCE(n), it setup the local
   LSP tunnel from entry BNe(n) to D by means of RSVP-TE signaling with
   the given ERO(n).  Once the tunnel setup, it chooses a free label for
   the Stitching Label SL(n) and add a new entry in its MPLS LFIB with
   this SL(n) label.  Then, it sends a PCRpt message to its PCE(n) with
   an RRO equal to {[LK(n), SL(n)], RRO(n)} and PLSP-ID(n).  Once PCE(n)
   receives the PCRpt from the PCC BNe(n) with the RRO, PLSP-ID and LSP-
   TYPE = TBD2, it sends to its Parent PCE a PCRpt containing the RRO
   equal to {[LK(n), SL(n)]} and PLSP-ID(n).  PCE(n) MAY adds {BN(n), D}
   in the RRO as loose path.

   Steps i: Actions performed for all intermediate domains(i), for i =
   n-1 to 2

   1.  Parent PCE sends a PCInitiate message to Child PCE(i) with LSP-
       TYPE = TBD1, ERO = {PKS(i), [LK(i+1), SL(i+1)]} and End-Points =
       {BNe(i), BNo(i)}

   2.  Then, PCE(i) retrieves the ERO from the PKS(i) if necessary and
       sends to the PCC BNe(i) a PCInitiate message with ERO = {ERO(i),
       [LK(i+1), SL(i+1)]}, LSP-TYPE = TBD2 and End-Points Object =
       {BNe(i), BNo(i)} in order to inform the PCC BNe(i) that this
       local LSP tunnel(i) is part of an inter-domain path.

   3.  When the PCC BNe(i) received the PCInitiate message from its
       PCE(i), it setup the local LSP tunnel from BNe(i) to BNo(i) by
       means of RSVP-TE signaling with the given ERO(i).

   4.  When the BNo(i) receives an RSVP-TE Path message with an ERO =
       {x-1, [LK(i+1), SL(i+1)]} and End-Points Object = {BNe(i),
       BNo(i)}, it MUST install in its MPLS LFIB the SWAP instruction to
       label SL(i+1) with forward to LK(i+1) instead of the standard POP
       instruction.



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   5.  Once the tunnel setup, it chooses a free label for the Stitching
       Label SL(i) and add a new entry in its MPLS L(F)IB with this
       SL(i) label.  Then, PCC BNe(i) sends a PCRpt message to its
       PCE(i) with an RRO equal to {[LK(i), SL(i)], RRO(i)} and PLSP-
       ID(i).

   6.  Once PCE(i) receives the PCRpt from the PCC BNe(i) with the RRO
       and LSP-TYPE = TBD2, it sends to its Parent PCE a PCRpt message
       containing the RRO equal to {[LK(i), SL(i)]} and the PLSP-ID(i).
       PCE(i) MAY adds {BNe(i), BNo(i)} in the RRO as loose path.

   7.  Once Parent PCE receives the PCRpt from the Child PCE(i), it
       stores the corresponding PLSP-ID for this inter-domain tunnel
       part

   Steps n: Actions performed to the source domain(1)

   Finally, Parent PCE sends a last PCInitiate message to Child PCE(1)
   with LSP-TYPE = TBD1, ERO = {PKS(1), [LK(2), SL(2)]} and End-Points =
   {S, BNo(1)}. In turn, Child PCE(1) sends a PCInitiate message to PCC
   node S with ERO equal to {ERO(1), [LK(2), SL(2)]}, LSP_TYPE = 0 and
   End-Points Object = {S, BNo(1)}. This time, the LSP_TYPE is equal to
   0 as the PCC S does not need to return a Stitching Label SL, i.e. it
   is the head-end of the inter-domain path.  Standard PCRpt message is
   sent back to PCE(1) by the PCC node S.  In turn, Child PCE(1) send a
   final PCRpt message to the Parent PCE with the PSLP-ID(1).  PCE(1)
   MAY adds {S, BNo(1)} in the RRO as loose path.

4.2.  Inter-domain LSP setup procedure completion failure

   In case of error during LSP setup, PCRpt and or PCError messages MUST
   be used to signal the problem to the Parent PCE.  In particular, if
   new LSP-TYPE values defined in this memo are not supported by the
   Child PCE or the PCC, the Child PCE, receptively the PCC, MUST return
   a PCErr message with Error-Type = 21 (Traffic engineering path setup
   error) and Error-Value = 1 (Unsupported path setup type) to its
   Parent PCE.  If Child PCE(i) receives a PCInitiate message from its
   Parent PCE without LSP-TYPE set to TBD1 or LSP-TYPE set to a value
   different from TBD1, it MUST return a PCErr message with Error-Type =
   21 (Traffic engineering path setup error) and Error-Value = 1
   (Unsupported path setup type) to its Parent PCE.

   If a Child PCE or a PCC don't return an RRO or an RRO without the
   Stitching Label SL with the IP address of the associated link
   following a PCInitiate message with LSP-TYPE set to TBD1, the Parent
   PCE, respectively the Child PCE, MUST return a PCErr message with
   Error-Type = 21 (Traffic engineering path setup error) and Error-
   Value = TBD4 (No Mandatory Stitching Label is present in the RRO).



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   In case of completion failure, the Parent PCE MUST MUST send a
   PCInitate message (R flag set in the SRP Object as per draft pce
   initiated lsp [I-D.ietf-pce-pce-initiated-lsp]) to delete this inter-
   domain path to the Child PCEs that already setup their respective
   part of the inter-domain tunnel.  Child PCE(i) MUST remove their
   local LSP tunnel by means of PCInitiate message with R flag set to 1
   to their PCC BNe(i) and send back PCRpt message to the Parent PCE.

5.  Inter-domain LSP Management

   This section describe how inter-domain LSPs could be manage.

5.1.  Identification of inter-domain tunnels

   First, in order to manage inter-domain tunnels composed by the
   stitching or nesting of local tunnels, it is important to identify
   them.  For this purpose, PLSP-ID managed by PCEs are combined to one
   provided by PCCs to form global identifier as follow:

   o  PCE(i) in the Backward Recursive method or the Child PCE in
      Hierarchical method MUST create a new unique PLSP-ID for this
      inter-domain LSP part and MUST send it in the PCRpt message, to
      the PCE(i-1), respectively the Parent PCE.  In addition this new
      PLSP-ID MUST be associated to the one received from the PCC that
      instantiate the local tunnel part for further reference.

   o  In Hierarchical mode, Parent PCE MUST store and associate the
      different PLSP-ID(i)s received from the different Child PCE(i)s in
      order to identify the different part of the inter-domain paths.

   o  In Backward Recursive method, PCE(i) MUST store and associate its
      PLSP-ID(i) and the PLSP-ID(i+1) it received from the PCE(i+1).
      PCE(n) i.e. the last one in the chain, don't need to perform such
      association.

   Further reference to the inter-domain tunnel will use this PLSP-
   ID(i).  In Backward Recursive method, PCE(i) MUST replace the PLSP-
   ID(i) by PLSP-ID(i+1) in the PCUpd message before propagating it to
   PCE(i+1) and PCE(i) MUST replace the PLSP-ID(i+1) by PLSP-ID(i) in
   the PCRpt message before propagating it to the PCE(i-1).  In
   Hierarchical method, Parent PCE MUST use the corresponding PLSP-ID(i)
   of the Child PCE(i).

5.2.  Inter-domain LSP management

   For the Backward Recursive method, each domain manages their
   respective local LSP tunnel part of an inter-domain path
   independently of each other.  In particular, Stitching Label(i) is



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   managed by domain(i) and is of interest of domain(i-1) only.  Thus,
   Stitching Label SL(i) is not supposed to be propagated to other
   domains.  The same behavior apply to PLSP-ID(i).  In Hierarchical
   method, the Parent PCE MUST ensure the correct distribution of
   Stitching Label SL(i) to Child PCE(i-1.  The PLSP-ID(i) is kept for
   the usage of the Parent PCE and thus is not propagated.

   If a PCE(i) needs to modify its local LSP tunnel(i) with PCUpd
   message to the PCC BNe(i), once PCRpt message received by the PCC
   BNe(i), it MUST sends a new PCRpt message to its neighbor PCE(i-1) in
   Backward Recursive method, respectively to Parent PCE in Hierarchical
   method, to advertise it of the modification.  In particular.  In this
   case PLSP-ID(i) is used to identify the inter-domain tunnel.
   PCE(i-1), respectively the Parent PCE, MUST propagate the PCRpt
   message if the modification imply the previous domain e.g. if the
   PCRpt indicates that the Stitching Label SL(i) has changed.

   PCE(1), respectively Parent PCE, could modify the inter-domain path.
   For that purpose, it MUST sends a PCUpd message to its neighbor PCEs,
   respectively Child PCE, using the PLSP-ID it received.  Each PCE(i)
   MUST process PCUpd message the same way they process PCInitiate
   message as define in section 3.1 for Backward Recursive method and in
   section 4.1 for Hierarchical method.

   In case a failure appear in domain(i), e.g. tunnel becoming down,
   PCE(i) MUST sends a PCRpt message to its neighbor PCE(i-1),
   respectively its Parent PCE to advertise it of the problem in its
   local part of the inter-domain path.  Once PCE(1), respectively
   Parent PCE, receives this PCRpt message indicating that the tunnel is
   down, it is up to the PCE(1), respectively Parent PCE to take
   appropriate correction e.g. start a new path computation to update
   the ERO.

5.3.  Modification of inter-domain LSP

   Modification of local LSP tunnel, BNe(i) and BNo(i) is left for
   further study.

5.4.  Removal of inter-domain LSP

   Deletion of inter-domain LSP is only possible by the inter-domain
   tunnel initiator.  For Backward Recursive method, PCInitiate message
   with R flag set to 1 and PLSP-ID set accordingly to section 5.1, is
   sent by PCE(1) to PCE(n) through PCE(i) and process the same way as
   describe in section 3.1.  For Hierarchical method, PCInitiate message
   with R flag set to 1 is sent by the Parent PCE to each Child PCE(i)
   with corresponding PLSP-ID(i) and process accordingly to section 4.1.




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6.  Applicability

   The newly introduce Stitching Label SL serves to stitch or nest part
   of local LSP tunnels to form an inter-domain path.  Each domain is
   free to decide if the tunnel is stitched or nested.  For example, a
   domain(i) may decided to nest the incoming local LSP tunnel into a
   higher hierarchy of tunnel for Traffic Engineering purpose.  A PCE(i)
   may also decided to group local LSP tunnels part of inter-domain
   paths into a higher hierarchical tunnel to carry all these local LSP
   tunnels from one BNe(i) to one BNo(i).

   To use Segment Routing instead of RSVP-TE to setup the local LSP
   tunnels as defined in draft pce segment routing
   [I-D.ietf-pce-segment-routing], PCE(i) MUST send PCInitiate message
   with LSP-TYPE = TBD3 instead of TBD2 to advertise their respective
   PCC that the local LSP tunnels is enforce by means of Segment
   Routing.  Stitching Label SL(i) will be inserted in the label stack
   in order to become the top label in the stack when the packet reach
   BNe(i+1): BNe(i) MUST install in its MPLS LFIB a SWAP instruction to
   the replace the incoming Stitching Label SL(i) by the label stack
   given by the ERO(i) plus the Stitching Label SL(i+1) as the last
   label in the stack.  The Stitching Label SL(i) serves as entry FEC
   for BNe(i) to identify the packets that follow the next Segment Path.
   When packet reach BNo(i), the last label in the stack before the
   label SL(i+1) corresponds to the SID that design BNe(i+1).  This
   inter-domain SID could be obtain as per draft Egress Peer Engineering
   [I-D.ietf-idr-bgpls-segment-routing-epe].

   The Stitching Label SL could serves to stitch Segment Path and RSVP-
   TE tunnel.  Indeed, each domain is free to enforce its part of the
   inter-domain path with the underlying mechanism it chosen.  Stitching
   Label SL will be part of the label stack in order to become the top
   label in the stack when reaching the BNe(i+1).  This Stitching Label
   could be swap as usual if the next domain uses RSVP-TE tunnel.  When
   the previous domain uses a RSVP-TE tunnel, the Stitching Label will
   serve as key for the BNe(i+1) to determine which label stack it must
   push on top of the packet for a Segment Routing path.

   During the instantiation procedure, if PCE(i) decides to reuse a
   local tunnel which is not yet part of an inter-domain tunnel, it
   SHOULD send a PCUpd message with LSP-TYPE = TBD2 to the PCC BNe(i) in
   order to request a Stitching Label SL(i) and new ERO(i) to include
   the Stitching Label SL(i+1) and the associated link to the previous
   ERO.

   Inter-layer scenario is left for further study.





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7.  IANA Considerations

7.1.  LSP-TYPE values

   Draft pce lsp setup type [I-D.ietf-pce-lsp-setup-type] defines the
   PATH-SETUP-TYPE TLV and requests that IANA creates a registry to
   manage the value of the PATH_SETUP_TYPE TLV's PST field.  IANA is
   requested to allocate a new code point in the PCEP PATH_SETUP_TYPE
   TLV PST field registry, as follows:

   +-------+-----------------------------------------------+-----------+
   | Value | Description                                   | Reference |
   +-------+-----------------------------------------------+-----------+
   | TBD1  | Inter-Domain Traffic engineering end-to-end   | This      |
   |       | path is setup using Backward Recursive method | Document  |
   | TBD2  | Inter-Domain Traffic engineering local path   | This      |
   |       | is setup using RSVP-TE                        | Document  |
   | TBD3  | Inter-Domain Traffic engineering local path   | This      |
   |       | is setup using Segment Routing                | Document  |
   +-------+-----------------------------------------------+-----------+

7.2.  PCEP-Error Object

   IANA is requested to allocate code-points in the PCEP-ERROR Object
   Error Values registry for a new error-value or Error-Type 21 Invalid
   traffic engineering path setup:

        +-------------+------------------------------------------+
        | Error-Value | Description                              |
        +-------------+------------------------------------------+
        | TBD4        | Missing Mandatory Stitching Label in RRO |
        +-------------+------------------------------------------+

8.  Security Considerations

   No modification of PCE protocol (PCEP) has been requested by this
   draft which not introduce any issue regarding security.  Concerning
   the PCEP session between PCEs, authors recommend to use the secure
   version of PCEP as defined in draft secure transport for PCEP
   [RFC8253] or use any other secure tunnel mechanism e.g.  IPsec tunnel
   to transport PCEP session between PCE.

9.  Acknowledgements

   The authors want to thanks PCE's WG members.






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10.  Disclaimer

   This work has been performed in the framework of the H2020-ICT-2014
   project 5GEx (Grant Agreement no. 671636), which is partially funded
   by the European Commission.  This information reflects the
   consortium's view, but neither the consortium nor the European
   Commission are liable for any use that may be done of the information
   contained therein.

11.  References

11.1.  Normative References

   [I-D.ietf-pce-lsp-setup-type]
              Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J.
              Hardwick, "Conveying path setup type in PCEP messages",
              draft-ietf-pce-lsp-setup-type-04 (work in progress), April
              2017.

   [I-D.ietf-pce-pce-initiated-lsp]
              Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
              Extensions for PCE-initiated LSP Setup in a Stateful PCE
              Model", draft-ietf-pce-pce-initiated-lsp-11 (work in
              progress), October 2017.

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

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

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://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,
              <https://www.rfc-editor.org/info/rfc5441>.





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   [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,
              <https://www.rfc-editor.org/info/rfc6805>.

   [RFC8231]  Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for Stateful PCE", RFC 8231,
              DOI 10.17487/RFC8231, September 2017,
              <https://www.rfc-editor.org/info/rfc8231>.

11.2.  Informative References

   [I-D.dong-pce-discovery-proto-bgp]
              Dong, J., Chen, M., Dhody, D., Tantsura, J., Kumaki, K.,
              and T. Murai, "BGP Extensions for Path Computation Element
              (PCE) Discovery", draft-dong-pce-discovery-proto-bgp-07
              (work in progress), July 2017.

   [I-D.ietf-idr-bgpls-segment-routing-epe]
              Previdi, S., Filsfils, C., Patel, K., Ray, S., and J.
              Dong, "BGP-LS extensions for Segment Routing BGP Egress
              Peer Engineering", draft-ietf-idr-bgpls-segment-routing-
              epe-13 (work in progress), June 2017.

   [I-D.ietf-pce-segment-routing]
              Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
              and J. Hardwick, "PCEP Extensions for Segment Routing",
              draft-ietf-pce-segment-routing-10 (work in progress),
              October 2017.

   [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,
              <https://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,
              <https://www.rfc-editor.org/info/rfc3473>.

   [RFC4003]  Berger, L., "GMPLS Signaling Procedure for Egress
              Control", RFC 4003, DOI 10.17487/RFC4003, February 2005,
              <https://www.rfc-editor.org/info/rfc4003>.





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Internet-Draft      PCE Stateful Inter-Domain Tunnels       October 2017


   [RFC4206]  Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
              Hierarchy with Generalized Multi-Protocol Label Switching
              (GMPLS) Traffic Engineering (TE)", RFC 4206,
              DOI 10.17487/RFC4206, October 2005,
              <https://www.rfc-editor.org/info/rfc4206>.

   [RFC5150]  Ayyangar, A., Kompella, K., Vasseur, JP., and A. Farrel,
              "Label Switched Path Stitching with Generalized
              Multiprotocol Label Switching Traffic Engineering (GMPLS
              TE)", RFC 5150, DOI 10.17487/RFC5150, February 2008,
              <https://www.rfc-editor.org/info/rfc5150>.

   [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,
              <https://www.rfc-editor.org/info/rfc5520>.

   [RFC8253]  Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
              "PCEPS: Usage of TLS to Provide a Secure Transport for the
              Path Computation Element Communication Protocol (PCEP)",
              RFC 8253, DOI 10.17487/RFC8253, October 2017,
              <https://www.rfc-editor.org/info/rfc8253>.

Authors' Addresses

   Olivier Dugeon
   Orange
   2, Avenue Pierre Marzin
   Lannion  22307
   France

   Email: olivier.dugeon@orange.com


   Julien Meuric
   Orange
   2, Avenue Pierre Marzin
   Lannion  22307
   France

   Email: julien.meuric@orange.com









Dugeon & Meuric          Expires April 30, 2018                [Page 22]


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