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Versions: (draft-crabbe-pce-pce-initiated-lsp) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 8281

PCE Working Group                                              E. Crabbe
Internet-Draft                                              Google, Inc.
Intended status: Standards Track                                I. Minei
Expires: June 5, 2014                             Juniper Networks, Inc.
                                                            S. Sivabalan
                                                     Cisco Systems, Inc.
                                                                R. Varga
                                               Pantheon Technologies SRO
                                                        December 2, 2013


  PCEP Extensions for PCE-initiated LSP Setup in a Stateful PCE Model
                  draft-ietf-pce-pce-initiated-lsp-00

Abstract

   The Path Computation Element Communication Protocol (PCEP) provides
   mechanisms for Path Computation Elements (PCEs) to perform path
   computations in response to Path Computation Clients (PCCs) requests.

   The extensions described in [I-D.ietf-pce-stateful-pce] provide
   stateful control of Multiprotocol Label Switching (MPLS) Traffic
   Engineering Label Switched Paths (TE LSP) via PCEP, for a model where
   the PCC delegates control over one or more locally configured LSPs to
   the PCE.  This document describes the creation and deletion of PCE-
   initiated LSPs under the stateful PCE model.

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].

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."




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   This Internet-Draft will expire on June 5, 2014.

Copyright Notice

   Copyright (c) 2013 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
   carefully, as they describe your rights and restrictions with respect
   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.



































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Architectural Overview . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Motivation . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.2.  Operation overview . . . . . . . . . . . . . . . . . . . .  5
   4.  Support of PCE-initiated LSPs  . . . . . . . . . . . . . . . .  6
     4.1.  Stateful PCE Capability TLV  . . . . . . . . . . . . . . .  7
   5.  PCE-initiated LSP instantiation and deletion . . . . . . . . .  7
     5.1.  The LSP Initiate Message . . . . . . . . . . . . . . . . .  7
     5.2.  The R flag in the SRP Object . . . . . . . . . . . . . . .  8
     5.3.  LSP instantiation  . . . . . . . . . . . . . . . . . . . .  9
       5.3.1.  The Create flag  . . . . . . . . . . . . . . . . . . . 11
     5.4.  LSP deletion . . . . . . . . . . . . . . . . . . . . . . . 11
   6.  LSP delegation and cleanup . . . . . . . . . . . . . . . . . . 12
   7.  Implementation status  . . . . . . . . . . . . . . . . . . . . 12
   8.  IANA considerations  . . . . . . . . . . . . . . . . . . . . . 13
     8.1.  PCEP Messages  . . . . . . . . . . . . . . . . . . . . . . 13
     8.2.  LSP Object . . . . . . . . . . . . . . . . . . . . . . . . 13
     8.3.  PCEP-Error Object  . . . . . . . . . . . . . . . . . . . . 14
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
     9.1.  Malicious PCE  . . . . . . . . . . . . . . . . . . . . . . 14
     9.2.  Malicious PCC  . . . . . . . . . . . . . . . . . . . . . . 15
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 15
     11.2. Informative References . . . . . . . . . . . . . . . . . . 16
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17






















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1.  Introduction

   [RFC5440] describes the Path Computation Element Protocol PCEP.  PCEP
   defines the communication between a Path Computation Client (PCC) and
   a Path Control Element (PCE), or between PCE and PCE, enabling
   computation of Multiprotocol Label Switching (MPLS) for Traffic
   Engineering Label Switched Path (TE LSP) characteristics.

   Stateful pce [I-D.ietf-pce-stateful-pce] specifies a set of
   extensions to PCEP to enable stateful control of TE LSPs between and
   across PCEP sessions in compliance with [RFC4657].  It includes
   mechanisms to effect LSP state synchronization between PCCs and PCEs,
   delegation of control of LSPs to PCEs, and PCE control of timing and
   sequence of path computations within and across PCEP sessions and
   focuses on a model where LSPs are configured on the PCC and control
   over them is delegated to the PCE.

   This document describes the setup, maintenance and teardown of PCE-
   initiated LSPs under the stateful PCE model, without the need for
   local configuration on the PCC, thus allowing for a dynamic network
   that is centrally controlled and deployed.


2.  Terminology

   This document uses the following terms defined in [RFC5440]: PCC,
   PCE, PCEP Peer.

   This document uses the following terms defined in
   [I-D.ietf-pce-stateful-pce]: Stateful PCE, Delegation, Redelegation
   Timeout, State Timeout Interval LSP State Report, LSP Update Request.

   The following terms are defined in this document:

   PCE-initiated LSP:  LSP that is instantiated as a result of a request
      from the PCE.

   The message formats in this document are specified using Routing
   Backus-Naur Format (RBNF) encoding as specified in [RFC5511].


3.  Architectural Overview

3.1.  Motivation

   [I-D.ietf-pce-stateful-pce] provides stateful control over LSPs that
   are locally configured on the PCC.  This model relies on the LER
   taking an active role in delegating locally configured LSPs to the



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   PCE, and is well suited in environments where the LSP placement is
   fairly static.  However, in environments where the LSP placement
   needs to change in response to application demands, it is useful to
   support dynamic creation and tear down of LSPs.  The ability for a
   PCE to trigger the creation of LSPs on demand can make possible agile
   software-driven network operation, and can be seamlessly integrated
   into a controller-based network architecture, where intelligence in
   the controller can determine when and where to set up paths.

   A possible use case is one of a software-driven network, where
   applications request network resources and paths from the network
   infrastructure.  For example, an application can request a path with
   certain constraints between two LSRs by contacting the PCE.  The PCE
   can compute a path satisfying the constraints, and instruct the head
   end LSR to instantiate and signal it.  When the path is no longer
   required by the application, the PCE can request its teardown.

   Another use case is one of dynamically adjusting aggregate bandwidth
   between two points in the network using multiple LSPs.  This
   functionality is very similar to auto-bandwidth, but allows for
   providing the desired capacity through multiple LSPs.  This approach
   overcomes two of the limitations auto-bandwidth can experience: 1)
   growing the capacity between the endpoints beyond the capacity of
   individual links in the path and 2) achieving good bin-packing
   through use of several small LSPs instead of a single large one.  The
   number of LSPs varies based on the demand, and LSPs are created and
   deleted dynamically to satisfy the bandwidth requirements.

   Another use case is that of demand engineering, where a PCE with
   visibility into both the network state and the demand matrix can
   anticipate and optimize how traffic is distributed across the
   infrastructure.  Such optimizations may require creating new paths
   across the infrastructure.

3.2.  Operation overview

   A PCC or PCE indicates its ability to support PCE provisioned dynamic
   LSPs during the PCEP Initialization Phase via a new flag in the
   STATEFUL-PCE-CAPABILITY TLV (see details in Section 4.1).

   The decision when to instantiate or delete a PCE-initiated LSP is out
   of the scope of this document.  To instantiate or delete an LSP, the
   PCE sends a new message, the Path Computation LSP Initiate Request
   (PCInitiate) message to the PCC.  The LSP Initiate Request MUST
   include the SRP and LSP objects, and the LSP object MUST include the
   Symbolic Path Name TLV and MUST have a PLSP-ID of 0.

   For an instantiation operation, the PCE MUST include the ERO and END-



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   POINTS object and may include various attributes as per [RFC5440].
   The PCC creates the LSP using the attributes communicated by the PCE,
   and local values for the unspecified parameters.  It assigns a unique
   PLSP-ID for the LSP and automatically delegates the LSP to the PCE.
   It also generates an LSP State Report (PCRpt) for the LSP, carrying
   the newly assigned PLSP-ID and indicating the delegation via the
   Delegate flag in the LSP object.  In addition to the Delegate flag,
   the PCC also sets the Create flag in the LSP object (see
   Section 5.3.1), to indicate that the LSP was created as a result of a
   PCinitiate message.  This PCRpt message MUST include the SRP object,
   with the SRP-id-number used in the SRP object of the PCInitate
   message.  The PCE may update the attributes of the LSP via subsequent
   PCUpd messages.  Subsequent LSP State Report and LSP Update Request
   for the LSP will carry the PCC-assigned PLSP-ID, which uniquely
   identifies the LSP.  See details in Section 5.3.

   Once instantiated, the delegation procedures for PCE-initiated LSPs
   are the same as for PCC initiated LSPs as described in
   [I-D.ietf-pce-stateful-pce].  This applies to the case of a PCE
   failure as well.  In order to allow for network cleanup without
   manual intervention, the PCC SHOULD support removal of PCE-initiated
   LSPs as one of the behaviors applied on expiration of the State
   Timeout Interval [I-D.ietf-pce-stateful-pce].  The behavior SHOULD be
   picked based on local policy, and can result either in LSP removal,
   or into reverting to operator-defined default parameters.  See
   details in Section 6.  A PCE may return a delegation to the PCC in
   order to facilitate re-delegation of its LSPs to an alternate PCE.

   To indicate a delete operation, the PCE MUST use the R flag in the
   SRP object in a PCUpd message.  As a result of the deletion request,
   the PCC MUST remove all state related to the LSP, and send a PCRpt
   with the R flag set in the LSP object for the removed state.  See
   details in Section 5.4.


4.  Support of PCE-initiated LSPs

   A PCC indicates its ability to support PCE provisioned dynamic LSPs
   during the PCEP Initialization phase.  The Open Object in the Open
   message contains the "Stateful PCE Capability" TLV, defined in
   [I-D.ietf-pce-stateful-pce].  A new flag, the I (LSP-INSTANTIATION-
   CAPABILITY) flag is introduced to indicate support for instantiation
   of PCE-initiated LSPs.  A PCE can initiate LSPs only for PCCs that
   advertised this capability and a PCC will follow the procedures
   described in this document only on sessions where the PCE advertised
   the I flag.





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4.1.  Stateful PCE Capability TLV

   The format of the STATEFUL-PCE-CAPABILITY TLV is shown in the
   following figure:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |               Type=16         |            Length=4           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              Flags                                      |I|S|U|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+

               Figure 1: STATEFUL-PCE-CAPABILITY TLV format

   The type of the TLV is defined in [I-D.ietf-pce-stateful-pce] and it
   has a fixed length of 4 octets.

   The value comprises a single field - Flags (32 bits).  The U and S
   bits are defined in [I-D.ietf-pce-stateful-pce].

   I (LSP-INSTANTIATION-CAPABILITY - 1 bit):  If set to 1 by a PCC, the
      I Flag indicates that the PCC allows instantiation of an LSP by a
      PCE.  If set to 1 by a PCE, the I flag indicates that the PCE will
      attempt to instantiate LSPs.  The LSP-INSTANTIATION-CAPABILITY
      flag must be set by both PCC and PCE in order to support PCE-
      initiated LSP instantiation.

   Unassigned bits are considered reserved.  They MUST be set to 0 on
   transmission and MUST be ignored on receipt.


5.  PCE-initiated LSP instantiation and deletion

   To initiate an LSP, a PCE sends a PCInitiate message to a PCC.  The
   message format, objects and TLVs are discussed separately below for
   the creation and the deletion cases.

5.1.  The LSP Initiate Message

   A Path Computation LSP Initiate Message (also referred to as
   PCInitiate message) is a PCEP message sent by a PCE to a PCC to
   trigger LSP instantiation or deletion.  The Message-Type field of the
   PCEP common header for the PCInitiate message is set to [TBD].  The
   PCInitiate message MUST include the SRP and the LSP objects, and may
   contain other objects, as discussed later in this section.  If either
   the SRP or the LSP object is missing, the PCC MUST send a PCErr as
   described in [I-D.ietf-pce-stateful-pce].  LSP instantiation is done



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   by sending an LSP Initiate Message with an LSP object with the
   reserved PLSP-ID 0.  LSP deletion is done by sending an LSP Initiate
   Message with an LSP object carrying the PLSP-ID of the LSP to be
   removed and an SRP object with the R flag set (see Section 5.2).

   The format of a PCInitiate message for LSP instantiation is as
   follows:


   <PCInitiate Message> ::= <Common Header>
                            <PCE-initiated-lsp-list>
Where:

   <PCE-initiated-lsp-list> ::= <PCE-initiated-lsp-request>[<PCE-initiated-lsp-list>]

   <PCE-initiated-lsp-request> ::= (<PCE-initiated-lsp-instantiation>|<PCE-initiated-lsp-deletion>)

   <PCE-initiated-lsp-instantiation> ::= <SRP>
                                         <LSP>
                                         <END-POINTS>
                                         <ERO>
                                         [<attribute-list>]

   <PCE-initiated-lsp-deletion> ::= <SRP>
                                    <LSP>

Where:
   <attribute-list> is defined in [RFC5440] and extended by PCEP extensions.

   The SRP object is used to correlate between initiation requests sent
   by the PCE and the error reports and state reports sent by the PCC.
   Every request from the PCE receives a new SRP-ID-number.  This number
   is unique per PCEP session and is incremented each time an operation
   (initiation, update, etc) is requested from the PCE.  The value of
   the SRP-ID-number MUST be echoed back by the PCC in PCErr and PCRpt
   messages to allow for correlation between requests made by the PCE
   and errors or state reports generated by the PCC.  Details of the SRP
   object and its use can be found in [I-D.ietf-pce-stateful-pce].

5.2.  The R flag in the SRP Object

   The format of the SRP object is shown Figure 2:









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              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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Flags                              |R|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        SRP-ID-number                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      //                      Optional TLVs                          //
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                      Figure 2: The SRP Object format

   The type object is defined in [I-D.ietf-pce-stateful-pce].

   A new flag is defined to indicate a delete operation initiated by the
   PCE:

   R (LSP-REMOVE - 1 bit):  If set to 1, it indicates a removal request
      initiated by the PCE.

5.3.  LSP instantiation

   LSP instantiation is done by sending an LSP Initiate Message with an
   LSP object with the reserved PLSP-ID 0.  The LSP is set up using
   RSVP-TE, extensions for other setup methods are outside the scope of
   this draft.

   Receipt of a PCInitiate Message with a non-zero PLSP-ID and the R
   flag in the SRP object set to zero results in a PCErr message of type
   19 (Invalid Operation) and value 8 (non-zero PLSP-ID in LSP
   initiation request).

   The END-POINTS Object is mandatory for an instantiation request of an
   RSVP-signaled LSP.  It contains the source and destination addresses
   for provisioning the LSP.  If the END-POINTS Object is missing, the
   PCC MUST send a PCErr message with Error-type=6 (Mandatory Object
   missing) and Error-value=3 (END-POINTS Object missing).

   The ERO Object is mandatory for an instantiation request.  It
   contains the ERO for the LSP.  If the ERO Object is missing, the PCC
   MUST send a PCErr message with Error-type=6 (Mandatory Object
   missing) and Error-value=9 (ERO Object missing).

   The LSP Object MUST include the SYMBOLIC-PATH-NAME TLV, which will be
   used to correlate between the PCC-assigned PLSP-ID and the LSP.  If



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   the TLV is missing, the PCC MUST send a PCErr message with Error-
   type=6(Mandatory object missing) and Error-value=14 (SYMBOLIC-PATH-
   NAME TLV missing).  The symbolic name used for provisioning PCE-
   initiated LSPs must not have conflict with the LSP name of any
   existing LSP in the PCC.  (Existing LSPs may be either statically
   configured, or initiated by another PCE).  If there is conflict with
   the LSP name, the PCC MUST send a PCErr message with Error-type=23
   (Bad Parameter value) and Error-value=1 (SYMBOLIC-PATH-NAME in use).
   The only exception to this rule is for LSPs for which the State
   timeout timer is running (see Section 6).

   The PCE MAY include various attributes as per [RFC5440].  The PCC
   MUST use these values in the LSP instantiation, and local values for
   unspecified parameters.  After the LSP setup, the PCC MUST send a
   PCRpt to the PCE, reflecting these values.  The SRP object in the
   PCRpt message MUST echo the value of the PCInitiate message that
   triggered the setup.  LSPs that were instantiated as a result of a
   PCInitiate message MUST have the C flag set in the LSP object.

   If the PCC determines that the LSP parameters proposed in the
   PCInitiate message are unacceptable, it MUST trigger a PCErr with
   error-type=TBD (PCE instantiation error) and error-value=1
   (Unacceptable instantiation parameters).  If the PCC encounters an
   internal error during the processing of the PCInitiate message, it
   MUST trigger a PCErr with error-type=TBD (PCE instantiation error)
   and error-value=2 (Internal error).

   A PCC MUST relay to the PCE errors it encounters in the setup of PCE-
   initiated LSP by sending a PCErr with error-type=TBD (PCE
   instantiation error) and error-value=3 (RSVP signaling error).  The
   PCErr MUST echo the SRP-id-number of the PCInitiate message.  The
   PCEP-ERROR object SHOULD include the RSVP Error Spec TLV (if an ERROR
   SPEC was returned to the PCC by a downstream node).  After the LSP is
   set up, errors in RSVP signaling are reported in PCRpt messages, as
   described in [I-D.ietf-pce-stateful-pce].

   A PCC SHOULD be able to place a limit on either the number of LSPs or
   the percentage of resources that are allocated to honor PCE-initiated
   LSP requests.  As soon as that limit is reached, the PCC MUST send a
   PCErr message of type 19 (Invalid Operation) and value TBD "PCE-
   initiated limit reached" and is free to drop any incoming PCInitiate
   messages without additional processing.

   Similarly, the PCE SHOULD be able to place a limit on either the
   number of LSP initiation requests pending for a particular PCC, or on
   the time it waits for a response (positive or negative) to a
   PCInitiate request from a PCC and MAY take further action (such as
   closing the session or removing all its LSPs) if this limit is



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   reached.

   On succesful completion of the LSP instantiation, the PCC assigns a
   PLSP-ID, and immediately delegates the LSP to the PCE by sending a
   PCRpt with the Delegate flag set.  The PCRpt MUST include the SRP-ID-
   number of the PCInitiate request that triggered its creation.  PCE-
   initiated LSPs are identified with the Create flag in the LSP Object.

5.3.1.  The Create flag

   The LSP object is defined in [I-D.ietf-pce-stateful-pce] and included
   here for easy reference.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                PLSP-ID                |   Flags |C|  O|A|R|S|D|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     //                        TLVs                                 //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 3: The LSP Object format

   A new flag, the Create (C) flag is introduced.  On a PCRpt message,
   the C Flag set to 1 indicates that this LSP was created via a
   PCInitiate message.  The C Flag MUST be set to 1 on each PCRpt
   message for the duration of existence of the LSP.  The Create flag
   allows PCEs to be aware of which LSPs were PCE-initiated (a state
   that would otherwise only be known by the PCC and the PCE that
   initiated them).

5.4.  LSP deletion

   PCE-initiated removal of a PCE-initiated LSP is done by setting the R
   (remove) flag in the SRP Object in the PCInitiate message from the
   PCE.  The LSP is identified by the PLSP-ID in the LSP object.  If the
   PLSP-ID is unknown, the PCC MUST generate a PCErr with error type 19,
   error value 3, "Unknown PLSP-ID".  A PLSP-ID of zero removes all LSPs
   that were initiated by the PCE.  If the PLSP-ID specified in the
   PCInitiate message is not delegated to the PCE, the PCC MUST send a
   PCErr message indicating "LSP is not delegated" (Error code 19, error
   value 1 ([I-D.ietf-pce-stateful-pce]).  If the PLSP-ID specified in
   the PCInitiate message was not created by the PCE, the PCC MUST send
   a PCErr message indicating "LSP is not PCE initiated" (Error code 19,
   error value TBD).  Following the removal of the LSP, the PCC MUST
   send a PCRpt as described in [I-D.ietf-pce-stateful-pce].  The SRP
   object in the PCRpt MUST include the SRP-ID-number from the



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   PCInitiate message that triggered the removal.  The R flag in the SRP
   object SHOULD be set.


6.  LSP delegation and cleanup

   PCE-initiated LSPs are automatically delegated by the PCC to the PCE
   upon instantiation.  The PCC MUST delegate the LSP to the PCE by
   setting the delegation bit to 1 in the PCRpt that includes the
   assigned PLSP-ID.  All subsequent messages from the PCC must have the
   delegation bit set to 1.  The PCC cannot revoke the delegation for
   PCE-initiated LSPs for an active PCEP session.  Sending a PCRpt
   message with the delegation bit set to 0 results in a PCErr message
   of type 19 (Invalid Operation) and value TBD "Delegation for PCE-
   initiated LSP cannot be revoked".  The PCE MAY further react by
   closing the session.

   A PCE MAY return a delegation to the PCC, to allow for LSP transfer
   between PCEs.  Doing so MUST trigger the State Timeout Interval timer
   ([I-D.ietf-pce-stateful-pce]).

   In case of PCEP session failure, control over PCE-initiated LSPs
   reverts to the PCC at the expiration of the redelegation timeout.  To
   obtain control of a PCE-initiated LSP, a PCE (either the original or
   one of its backups) sends a PCInitiate message, including just the
   SRP and LSP objects, and carrying the PLSP-ID of the LSP it wants to
   take control of.  Receipt of a PCInitiate message with a non-zero
   PLSP-ID normally results in the generation of a PCErr.  If the State
   Timeout timer is running, the PCC MUST NOT generate an error and
   redelegate the LSP to the PCE.  The State Timeout timer is stopped
   upon the redelegation.  After obtaining control of the LSP, the PCE
   may remove it using the procedures described in this document.

   The State Timeout timer ensures that a PCE crash does not result in
   automatic and immediate disruption for the services using PCE-
   initiated LSPs.  PCE-initiated LSPs are not be removed immediately
   upon PCE failure.  Instead, they are cleaned up on the expiration of
   this timer.  This allows for network cleanup without manual
   intervention.  The PCC SHOULD support removal of PCE-initiated LSPs
   as one of the behaviors applied on expiration of the State Timeout
   Interval [I-D.ietf-pce-stateful-pce].  The behavior SHOULD be picked
   based on local policy, and can result either in LSP removal, or into
   reverting to operator-defined default parameters.


7.  Implementation status

   This section to be removed by the RFC editor.



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   This section records the status of known implementations of the
   protocol defined by this specification at the time of posting of this
   Internet-Draft, and is based on a proposal described in RFC 6982.
   The description of implementations in this section is intended to
   assist the IETF in its decision processes in progressing drafts to
   RFCs.  Please note that the listing of any individual implementation
   here does not imply endorsement by the IETF.  Furthermore, no effort
   has been spent to verify the information presented here that was
   supplied by IETF contributors.  This is not intended as, and must not
   be construed to be, a catalog of available implementations or their
   features.  Readers are advised to note that other implementations may
   exist.

   According to RFC 6982, "this will allow reviewers and working groups
   to assign due consideration to documents that have the benefit of
   running code, which may serve as evidence of valuable experimentation
   and feedback that have made the implemented protocols more mature.
   It is up to the individual working groups to use this information as
   they see fit".

   Two vendors are implementing the extensions described in this draft
   and have included the functionality in releases that will be shipping
   in the near future.  An additional entity is working on implementing
   these extensions in the scope of research projects.


8.  IANA considerations

8.1.  PCEP Messages

   This document defines the following new PCEP messages:

       Value     Meaning               Reference
         12       Initiate             This document

8.2.  LSP Object

   The following values are defined in this document for the Flags field
   in the LSP Object.

       Bit    Description           Reference

       24     Create                This document








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8.3.  PCEP-Error Object

   This document defines new Error-Type and Error-Value for the
   following new error conditions:

    Error-Type  Meaning
       6        Mandatory Object missing
                 Error-value=13: LSP cleanup TLV missing
                 Error-value=14: SYMBOLIC-PATH-NAME TLV missing
       19       Invalid operation
                 Error-value=6:  PCE-initiated LSP limit reached
                 Error-value=7:  Delegation for PCE-initiated LSP cannot
                                 be revoked
                 Error-value=8:  Non-zero PLSP-ID in LSP initiation
                                 request
       23       Bad parameter value
                 Error-value=1:  SYMBOLIC-PATH-NAME in use
       24       LSP instantiation error
                 Error-value=1:  Unacceptable instantiation parameters
                 Error-value=2:  Internal error
                 Error-value=3:  RSVP signaling error


9.  Security Considerations

   The security considerations described in [I-D.ietf-pce-stateful-pce]
   apply to the extensions described in this document.  Additional
   considerations related to a malicious PCE are introduced.

9.1.  Malicious PCE

   The LSP instantiation mechanism described in this document allows a
   PCE to generate state on the PCC and throughout the network.  As a
   result, it introduces a new attack vector: an attacker may flood the
   PCC with LSP instantiation requests and consume network and LSR
   resources, either by spoofing messages or by compromising the PCE
   itself.

   A PCC can protect itself from such an attack by imposing a limit on
   either the number of LSPs or the percentage of resources that are
   allocated to honor PCE-initiated LSP requests.  As soon as that limit
   is reached, the PCC MUST send a PCErr message of type 19 (Invalid
   Operation) and value 3 "PCE-initiated LSP limit reached" and is free
   to drop any incoming PCInitiate messages for LSP instantiation
   without additional processing.

   Rapid flaps triggered by the PCE can also be an attack vector.  This
   will be discussed in a future version of this document.



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9.2.  Malicious PCC

   The LSP instantiation mechanism described in this document requires
   the PCE to keep state for LSPs that it instantiates and relies on the
   PCC responding (with either a state report or an error message) to
   requests for LSP instantiation.  A malicious PCC or one that reached
   the limit of the number of PCE-initiated LSPs, can ignore PCE
   requests and consume PCE resources.  A PCE can protect itself by
   imposing a limit on the number of requests pending, or by setting a
   timeout and it MAY take further action such as closing the session or
   removing all the LSPs it initiated.


10.  Acknowledgements

   We would like to thank Jan Medved, Ambrose Kwong, Ramon Casellas,
   Dhruv Dhody, and Raveendra Trovi for their contributions to this
   document.


11.  References

11.1.  Normative References

   [I-D.ietf-pce-stateful-pce]
              Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP
              Extensions for Stateful PCE",
              draft-ietf-pce-stateful-pce-07 (work in progress),
              October 2013.

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

   [RFC2205]  Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
              Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
              Functional Specification", RFC 2205, September 1997.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, December 2001.

   [RFC4090]  Pan, P., Swallow, G., and A. Atlas, "Fast Reroute
              Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
              May 2005.

   [RFC5088]  Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
              "OSPF Protocol Extensions for Path Computation Element
              (PCE) Discovery", RFC 5088, January 2008.



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   [RFC5089]  Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
              "IS-IS Protocol Extensions for Path Computation Element
              (PCE) Discovery", RFC 5089, January 2008.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

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

   [RFC5511]  Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
              Used to Form Encoding Rules in Various Routing Protocol
              Specifications", RFC 5511, April 2009.

11.2.  Informative References

   [RFC2702]  Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J.
              McManus, "Requirements for Traffic Engineering Over MPLS",
              RFC 2702, September 1999.

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031, January 2001.

   [RFC3346]  Boyle, J., Gill, V., Hannan, A., Cooper, D., Awduche, D.,
              Christian, B., and W. Lai, "Applicability Statement for
              Traffic Engineering with MPLS", RFC 3346, August 2002.

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              September 2003.

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

   [RFC4657]  Ash, J. and J. Le Roux, "Path Computation Element (PCE)
              Communication Protocol Generic Requirements", RFC 4657,
              September 2006.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, October 2008.

   [RFC5394]  Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash,
              "Policy-Enabled Path Computation Framework", RFC 5394,
              December 2008.

   [RFC5557]  Lee, Y., Le Roux, JL., King, D., and E. Oki, "Path



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              Computation Element Communication Protocol (PCEP)
              Requirements and Protocol Extensions in Support of Global
              Concurrent Optimization", RFC 5557, July 2009.

   [RFC6982]  Sheffer, Y. and A. Farrel, "Improving Awareness of Running
              Code: The Implementation Status Section", RFC 6982,
              July 2013.


Authors' Addresses

   Edward Crabbe
   Google, Inc.
   1600 Amphitheatre Parkway
   Mountain View, CA  94043
   US

   Email: edc@google.com


   Ina Minei
   Juniper Networks, Inc.
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089
   US

   Email: ina@juniper.net


   Siva Sivabalan
   Cisco Systems, Inc.
   170 West Tasman Dr.
   San Jose, CA  95134
   US

   Email: msiva@cisco.com


   Robert Varga
   Pantheon Technologies SRO
   Mlynske Nivy 56
   Bratislava  821 05
   Slovakia

   Email: robert.varga@pantheon.sk






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