PCE Working Group                                              Y. Tanaka
Internet-Draft                                                 Y. Kamite
Intended status: Standards Track                      NTT Communications
Expires: August 17, 2014                                        I. Minei
                                                                  Google
                                                                D. Dhody
                                                     Huawei Technologies
                                                            Feb 13, 2014


    Stateful PCE Extensions for Data Plane Switchover and Balancing
               draft-tanaka-pce-stateful-pce-data-ctrl-02

Abstract

   Stateful Path Computation Element (PCE) and its corresponding
   protocol extensions provide a mechanism that enables PCE to do
   stateful control of Multiprotocol Label Switching (MPLS) Traffic
   Engineering Label Switched Paths (TE LSP).  One application that
   stateful PCE can realize is data traffic reoptimization among the
   LSPs.  Data traffic traversed in a LSP can be switched to another
   PCE-initiated LSP.  Moreover, data traffic can be balanced to
   multiple PCE-initiated LSPs and may also be policed based on a
   signaling bandwidth of a PCE-Initiated LSP using stateful PCE.

   This document specifies the extensions to Path Computation Element
   Protocol (PCEP) that allow a stateful PCE to do switchover, balancing
   and policing of data traffic with PCE-initiated LSPs.  This document
   also specifies the extensions, usage and handling of stateful PCEP
   messages and the expected behavior of PCC as the RSVP-TE headend.

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 August 17, 2014.




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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
   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.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions used in this document  . . . . . . . . . . . . . .  4
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  PCEP Operation for Data Switchover and Balancing . . . . . . .  4
   5.  TLVs in LSP Objects  . . . . . . . . . . . . . . . . . . . . .  6
     5.1.  ASSOCIATION-GROUP TLV in LSP Objects . . . . . . . . . . .  6
     5.2.  DATA-CONTROL TLV in LSP Objects  . . . . . . . . . . . . .  8
     5.3.  DATA-REPORT TLV in LSP Objects . . . . . . . . . . . . . . 10
     5.4.  Advertising Support of Data Switchover and Balancing . . . 11
   6.  Operation Examples . . . . . . . . . . . . . . . . . . . . . . 11
     6.1.  Data switchover operation (100:0 => 0:100) . . . . . . . . 11
     6.2.  Load balancing operation (100:0 => 50:50)  . . . . . . . . 13
     6.3.  Load balancing operation (100:0 => 66:33)  . . . . . . . . 14
   7.  Redundant stateful PCEs  . . . . . . . . . . . . . . . . . . . 15
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
     8.1.  Malicious PCE  . . . . . . . . . . . . . . . . . . . . . . 16
     8.2.  Malicious PCC  . . . . . . . . . . . . . . . . . . . . . . 16
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
     9.1.  PCEP TLV Indicators  . . . . . . . . . . . . . . . . . . . 17
     9.2.  PCEP Error Objects . . . . . . . . . . . . . . . . . . . . 17
   10. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 17
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 17
     11.2. Informative References . . . . . . . . . . . . . . . . . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18








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1.  Introduction

   [I-D.ietf-pce-stateful-pce] describes the stateful Path Computation
   Elements (PCE) procedures and defines the extensions to PCEP to
   enable stateful control of LSPs between and across PCEP sessions,
   further it also describes mechanisms to effect LSP state
   synchronization between PCCs and PCEs, and PCE control of timing and
   sequence of path computations within and across PCEP sessions.  A PCE
   can update LSP settings (such as bandwidth, priority, path) using an
   update message (called PCUpd).

   [I-D.ietf-pce-pce-initiated-lsp] defines the extensions to PCEP to
   allow a PCE to instantiate new LSPs (called PCE-Initiated LSPs).
   Before these extensions, the LSP ingress point had to be
   preconfigured at the head end Label Edge Router (LER), the LSP
   control automatically delegated to the initiating stateful PCE and
   then its parameters (e.g., bandwidth, priority, path) could be
   modified via a PCUpd message.  The extensions for PCE-initiated LSPs
   eliminate the need for preconfiguration, and allow more flexible
   operations on the network.  Stateful-PCE with LSP instantiation is
   attracting attention as an enabler for Software Defined Networking
   (SDN) operation of MPLS networks.

   In SDN, it is highly expected to support intelligent and interactive
   control of the amount of network traffic by means of a logically-
   centralized controller.  Optimizing the path and bandwidth of MPLS-TE
   LSP by using stateful PCE is a leading use case of SDN applications.
   A PCE is able to calculate an optimized route from the topology and
   bandwidth information in the Traffic Engineering Database (TED) and
   the LSP state database (LSPDB) and it can integrate with a controller
   that takes into account additional information such as historical
   trends and service orders to trigger some PCE actions.  For example,
   when data traffic on a LSP increases the bandwidth utilization and if
   there is no capacity left in the currently signaled path (i.e., no
   remaining bandwidth of links), a PCE is able to update the existing
   LSP's parameters (PCE-updated LSP) or create a totally new LSP (PCE-
   initiated LSP).

   The former method is oriented for keeping the existing instance of
   LSP tunnel.  Meanwhile, the latter method is oriented for adding a
   new instance of a LSP tunnel.

   Specifically regarding the latter method, PCE-initiated LSP, there
   are some operational scenarios in the network: one is that PCE
   instantiate a new LSP that have alternate route with increased-
   bandwidth LSP and performs switchover from old LSP.  Another is that
   PCE creates one or more additional LSPs and performs load balancing
   of data traffic.  Today, however, there is no detailed procedure



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   specified as to how to control data traffic switching from an old LSP
   to new PCE-Initiated LSP(s).

   For another example, when data traffic on a LSP increases its
   bandwidth utilization and if there is strict traffic contract, a PCE
   is able to force a PCC not to exceed the contract bandwidth.

   This document specifies the procedures that a stateful PCE can use to
   control data traffic switchover, load balancing with multiple PCE-
   Initiated LSPs and policing activation/deactivation.  This document
   also specifies the usage and handling of stateful PCEP messages and
   the expected behavior of PCC as an RSVP-TE headend.


2.  Conventions used in this document

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


3.  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, LSP State Request, LSP
   Update Request.

   This document uses the following terms defined in
   [I-D.ietf-pce-pce-initiated-lsp]: LSP Initiate Message.


4.  PCEP Operation for Data Switchover and Balancing

   There are two typical operations for explaining the functionality of
   data switchover and balancing.

   o  Whole data switchover, where a PCC switches all data traffic from
      one LSP tunnel to another.
   o  Load balancing of multi-instance LSP tunnels with different paths,
      where a PCC (headend) balances data traffic among two or more
      tunnels (ex fifty percent each, for two instances).

   Both operational cases are completed by the messaging over a single
   protocol, PCEP, keeping this as a simple and straightforward solution
   for MPLS networks.



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   A PCEP speaker indicates its ability to support PCE control over the
   data switchover and balancing 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 W (LSP-DATASWITCHOVER-BALANCE-CAPABILITY) flag is introduced.  A
   PCE can control the data switchover and loadbalancing 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 W flag.  (Refer Section 5.4)

   Data switchover and balancing for an MPLS-TE LSP is available once a
   PCEP session is established and then a PCC delegates its LSPs to a
   PCE.

   First step is LSP instantiation.  In this step, a PCE sends as many
   PCInitiate messages as PCE-Initiated LSP as per demand.  Once the PCC
   receives them and successfully establishes PCE-Initiated LSPs, it
   sends PCRpt messages in reply to the PCInitiate messages and
   delegates the newly established LSP to the PCE.  Message formats and
   behaviors of the PCC and the PCE are described in detail in
   [I-D.ietf-pce-pce-initiated-lsp].

   Second step is LSP association.  After the PCE-Initiated LSP
   successfully established and delegated the PCE sends a PCUpd message
   that contains the ASSOCIATION-GROUP TLV in the LSP Object in order to
   assemble the members of an association group of LSPs to take over the
   traffic.  Once a PCC receives the PCUpd message with ASSOCIATION-
   GROUP TLV, the PCC sends back a PCRpt message that contains the
   ASSOCIATION-GROUP TLV with current operational status.

   [Editor's Note: The option of specifying the association at LSP
   instantiation time (as part of the PCInitiate message) will be
   evaluated in a future version of this document.]

   Third step is executing the data switchover and/or load balancing.
   In this step, the PCE sends a single PCUpd message which updates the
   operational status of the LSP from "up and carrying traffic" to just
   "up".  This Update request message for data plane switchover/
   balancing execution MUST contain DATA-CONTROL TLV in LSP Object.  The
   associated group of traffic origin and that of target to take over
   the traffic are listed in the DATA-CONTROL TLV.  The PCC (LSP
   headend) load-balances between LSPs in the same association group
   based on their respective bandwidths.  The switchover case is
   supported since there will be an association of a single LSP, so that
   LSP will get hundred percent of data traffic.

   The PCC MUST send a PCRpt message to the PCE in order to notify of
   the result of the data switchover/balancing.  The PCRpt message MUST



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   have the DATA-CONTROL TLV that indicates the actual assigned
   percentages of each member of association group after the execution
   of the data switchover/balancing operation.  The LSP object in the
   PCRpt will have the reserved PLSP-ID of 0.

   The final step is the deletion of old LSP.  It is OPTIONAL to carry
   out this step.  The PCE sends PCInitiate message requesting deletion
   of the LSP that does not carry data traffic anymore after data
   switchover/balancing execution.  Once the PCC tears down the LSP, a
   PCRpt message MUST be sent from the PCC to the PCE in order to notify
   that the LSP is no longer used.

   Note that, both RSVP-TE [RFC3209] Tunnel-ID and LSP-ID for PCE-
   Initiated LSP signaling is not allocated by a PCE.  A PCC locally
   assigns those IDs that are related to RSVP-TE parameters.  Therefore,
   the operations of data switchover and balancing specified in this
   document is the traffic control procedure across multiple RSVP-TE
   Tunnels (i.e., different Tunnel instances).  Data switchover method
   across LSPs within a single RSVP-TE Tunnel, which is the switchover
   in the middle of make-before-break reoptimization, is covered by
   [I-D.tanaka-pce-stateful-pce-mbb].


5.  TLVs in LSP Objects

5.1.  ASSOCIATION-GROUP TLV in LSP Objects

   This section defines ASSOCIATION-GROUP TLV in LSP Objects.  An
   ASSOCIATION-GROUP TLV is used in the LSP Object in PCUpd messages
   when a PCE creates an association group of LSPs on a PCC.  Further it
   is used in a LSP object in a PCRpt message to confirm the
   association.


    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=TBD            |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Association Group ID              |     Flags     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+






    0                   1                   2                   3



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    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=TBD            |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Association Group ID              |     Flags     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




                  Figure 1: ASSOCIATION-GROUP TLV format

   Flags and fields

      Association Group ID - 24 bits:   This field specifies a
         identifier of association group of LSPs.  The IDs are assigned
         by a PCE. 0x000000 and 0xFFFFFF is reserved for special use.
      Flags - 8 bit:   None defined.  MUST be set to zero.

   An association group is a group of LSPs that is referenced by a
   single identifier, by both the PCE and PCC.  This number is
   significant in the context of a single PCEP session.  An association
   group may have one or more LSPs.  Association groups with zero
   members are removed and the id can be reused.  The PCE is the entity
   managing association, and this is considered PCE's state that will be
   cleaned up when the State Timeout Interval expires.

   The status of the association group is active when the group is up
   and carrying data traffic.  Otherwise, it is inactive when the group
   does not carry any data traffic.  An LSP is able to associate with up
   to two association groups, unless both association groups are active
   at any given point in time.  This is done to allow a new LSP to be
   instantiated and assigned with a new inactive association group, the
   existing LSP is also associated with this group.  This allows
   switching to the new group.

   To create a new association group on a PCC, a PCE sends a PCUpd
   message which contains the LSP Object(e.g.  PLSP-ID=100) and
   ASSOCIATION-GROUP TLV (Association Group ID=10) in the LSP object.
   Next, a PCE sends the another PCUpd message with another LSP
   Object(e.g.  PLSP-ID=200) and ASSOIATION-GROUP TLV(Association Group
   ID=10).  As a result, the PCC and PCE both recognize that Association
   Group ID 10 represents PLSP-ID=100 and 200.

   To remove a specific PLSP-ID from the association group, a PCE sends
   PCUpd message which contains the LSP Object(PLSP-ID=100) and
   ASSOCIATION-GROUP TLV (Association Group ID=0x0000).  Then a PCC
   removes the PLSP-ID 100 from any inactive association group on the



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   PCC.

   To flush all association groups on a PCC, a PCE sends a PCUpd message
   which contains the LSP Object(PLSP-ID=0x0000) and ASSOCIATION-GROUP
   TLV(Association Group ID=0x0000).  Then a PCC flushes all association
   groups.  A traffic handling behavior of a PCC when it flushes the
   active association group is left for a future version of this
   document.

   To associate a PLSP-ID with the existing inactive association group,
   A PCE sends a PCUpd message which contains the PLSP-ID and the
   existing Association Group ID.  A PCE is not allowed to add any
   PLSP-ID to the active association group in order to avoid rebalancing
   traffic without data-ctrl requests.  If the PCUpd message contains a
   PLSP-ID and the active Association Group ID, the PCC MUST send out a
   PCErr with error value TBD to indicate an invalid operation.

   When the LSP of the active association group is torn down by a reason
   of either network failure or administrative down-request from the
   PCE, a PCC MUST remove the PLSP-ID from the group and rebalance the
   traffic based on the respective bandwidths of the rest of LSPs.
   After rebalancing, The PCC MUST report the actual percentage to the
   PCE using PCRpt with DATA-REPORT TLV (Section 5.3).

   Note that a PCE is able to associate not only PCE-Initiated LSP but
   also existing LSP(i.e., PCE-updated LSP) with any association group
   on a PCC.

   The definition of PCRpt messages when a PCC creates/removes/flushes
   an association group will be clarified in the future version of this
   draft.  Redundant stateful PCE section needs the PCRpt in order to
   sync the association group IDs and actual percentages of balancing.

5.2.  DATA-CONTROL TLV in LSP Objects

   This section defines DATA-CONTROL TLV in LSP Objects.  A DATA-CONTROL
   TLV is used in the LSP Object in PCUpd messages when a PCE makes a
   PCC to execute traffic switchover or load balancing.  It is also
   mandatory in a LSP object in a PCRpt message with DATA-REPORT TLV to
   notify the results of execution.











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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Type=TBD            |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Origin Association Group ID            | Flags   |  O  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Target Association Group ID            | Flags |P|  O  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                     Figure 2: DATA-CONTROL TLV format

   Flags and fields

      Origin Association Group ID - 24 bits:   data traffic origin
      Target Association Group ID - 24 bits:   for taking over whole
         data traffic from origin.
      P (Policing - 1 bit:   This flag is used when a PCE makes a PCC
         apply traffic policer.  If this flag is set 1, traffic
         exceeding the bandwidth of the LSP is discarded on the PCC
         after traffic switchover execution.  Otherwise, the PCC does
         not apply any traffic policer and traffic on a target
         association group will not be discarded.
      O (Operational - 3 bits):   This flag represents the requested
         operational status for each Origin Association Group ID and
         Target Association Group ID by a PCE when this TLV is used in a
         PCUpd message.  It is also used as a status report in a PCRpt
         message.  The meanings of the values are defined in
         [I-D.ietf-pce-stateful-pce].

   An LSP Object in a PCUpd message MUST have DATA-CONTROL TLV when a
   PCE operates data switchover and balancing on a PCC.  DATA-CONTROL
   TLV is sub-TLV of an LSP Object and is used in both a PCUpd and a
   PCRpt message.

   An operation of data switchover/balancing is the action of
   transferring traffic from an origin association group to a target
   association group.  A PCUpd message with reserved LSP Object (PLSP-
   ID=0x00000) and DATA-CONTROL TLV (a set of an origin and a target
   association group) MUST triggers data switchover/balancing execution.

   Traffic policer is able to be applied in both traffic switchover case
   and load-balancing case.






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5.3.  DATA-REPORT TLV in LSP Objects

   This section defines DATA-REPORT TLV in LSP Objects.  A DATA-REPORT
   TLV is used in the LSP Object in PCRpt message to notify the results
   of execution with the DATA-CONTROL TLV.


    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=TBD            |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Member 1 (PLSP-ID )              |  Flags  |  Percentage |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Member 2 (PLSP-ID )              |  Flags  |  Percentage |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                                                              //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Member N (PLSP-ID )              |  Flags  |  Percentage |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                     Figure 3: DATA-REPORT TLV format

   Flags and fields

      Member(PLSP-ID) - 20 bit:  This TLV is only used in a PCRpt
         message and represents actual percentages of load balancing per
         respective PLSP-ID after load balancing execution.  Member
         field fills PLSP-ID that is member of target association group.
         As per [I-D.ietf-pce-stateful-pce].
      Flags - 5 bit:   None defined.  MUST be set to zero.
      Percentage - 7 bits:   This field specifies actual percentage of
         load balancing as a closest integer, with 100% as the max
         allowed value.

   A PCC replies to a PCE a PCRpt message as an acknowledgment of data
   switchover/balancing result.  The PCRpt message MUST have reserved
   LSP Object(PLSP-ID=0x00000) and DATA-CONTROL TLV with DATA-REPORT TLV
   inside.

   The PCC load-balances between LSPs in the same association group
   based on their respective bandwidths.If one of the LSPs goes down by
   network failure, the traffic would load-balance correctly over the
   others.  If a PCE updates the bandwidth of the LSP, the traffic would



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   rebalance after a PCC completes the signaling.  If one of the LSPs is
   signaled with zero bandwidth, no traffic would be transferred to the
   LSP.  If all LSPs of the association group are signaled with zero
   bandwidth, the traffic would load-balance equally.  In switchover
   case, the hundred percent traffic will be transferred to the LSP even
   if the LSP is zero bandwidth.

   The traffic on the existing LSP is able to load-balance over both the
   existing LSP itself and new PCE-Initiated LSPs, by means of that the
   existing LSP belongs to both the origin association group and that of
   target.

5.4.  Advertising Support of Data Switchover and Balancing

   New flags are defined for the STATEFUL-PCE-CAPABILITY TLV defined in
   [I-D.ietf-pce-stateful-pce].

   W (LSP-DATASWITCHOVER-BALANCE-CAPABILITY - 1 bit):  if set to 1 by a
      PCEP speaker, it indicates that the PCEP speaker allows data
      switchover and balancing.


6.  Operation Examples

   For easy understanding this section introduces typical operation
   examples of data switchover/balancing.

6.1.  Data switchover operation (100:0 => 0:100)

   A PCE instructs a PCC to switchover 100% traffic from association
   group ID 1 to association group ID 2.  A PCE sends single PCUpd
   message containing the mandatory LSP Objects with DATA-CONTROL TLV.

   Expected PCUpd, PCRpt messages to create association group and to
   trigger data switchover follow.
















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    PCE                         PCC(Ingress)     Egress
   [LSP Association for existing LSP]
     |                           |                |
     | --PCUpd ----------------->|                |
     |   LSP Obj: PLSP-ID=1      |                |
     |   + ASSOC-G: Assoc-G-ID 10|                |
     |                           |                |
     |<--PCRpt ----------------- |                |
     |   LSP Obj: PLSP-ID=1      |                |
     |   + ASSOC-G: Assoc-G-ID 10|                |

   [LSP Creation]
     |                           |                |
     | --PCInitiate ------------>|                |
     |                           | --Path ------->|
     |                           |<------- Resv-- | Establish a new
     |<--PCRpt ----------------- |                | PCE-Initiated LSP
     |   LSP Obj: PLSP-ID=2      |                |
     |                           |                |

   [LSP Association for PCE-Initiated LSP]
     |                           |                |
     | --PCUpd ----------------->|                |
     |   LSP Obj: PLSP-ID=2      |                |
     |   + ASSOC-G: Assoc-G-ID 20|                |
     |                           |                |
     |<--PCRpt ----------------- |                |
     |   LSP Obj: PLSP-ID=2      |                |
     |   + ASSOC-G: Assoc-G-ID 20|                |
     |                           |                |

   [Switchover Execution]
     |                           |                |
     | --PCUpd ----------------->|                |
     |   LSP Obj: PLSP-ID=0x0000 |                |
     |   + D-CTRL:               |        :       |
     |    Origin Assoc-G-ID 10(O=up)      :       |
     |    Target Assoc-G-ID 20(O=active)  :       |
     |                           |))))))))))))))))| Switchover
     |                           |}}}}}}}}}}}}}}}}| Execution
     |<--PCRpt------------------ |        :       |
     |   LSP Obj: PLSP-ID=0x0000 |        :       |
     |   + D-CTRL:               |        :       |
     |    Origin Assoc-G-ID 10(O=up)              |
     |    Target Assoc-G-ID 20(O=active)          |
     |   + D-REPORT:             |                |
     |    PLSP-ID 2, 100%        |                |
     |                           |                |



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                  Figure 4: Switchover Operation Example

6.2.  Load balancing operation (100:0 => 50:50)

   The scenario is one where the starting state is a single LSP (of
   bandwidth 100 M) is carrying the traffic.  To enable better bin-
   packing, the PCE may want to create two smaller LSPs instead, each of
   50M, and load balance the traffic over them.  To accomplish this, two
   association groups are used, the first (say association group ID 10)
   contains the LSP carrying the traffic, and the second (say
   association group ID 30) contains the two new smaller LSPs.  Expected
   PCUpd, PCRpt messages to create association group and to trigger
   load-balance follow (The instantiation of the original LSP of
   bandwidth 100M and its association into group ID 10 is not shown)

    PCE                         PCC(Ingress)     Egress

   [LSP Creation]
     |                           |                |
     | --PCInitiate x2---------->|                |
     |      BW: 50M              | --Path x2----->|
     |                           |<-----Resv x2-- | Establish two new
     |<--PCRpt ----------------- |                | PCE-Initiated LSP
     |   LSP Obj: PLSP-ID=3      |                |
     |<--PCRpt ----------------- |                |
     |   LSP Obj: PLSP-ID=4      |                |
     |                           |                |


   [LSP Association for PCE-Initiated LSPs]
     |                           |                |
     | --PCUpd ----------------->|                | Create new
     |   LSP Obj: PLSP-ID=3      |                | Association Group
     |   + ASSOC-G: Assoc-G-ID 30|                | for PCE-Initiated
     |                           |                | LSP
     |<--PCRpt ----------------- |                |
     |   LSP Obj: PLSP-ID=3      |                |
     |   + ASSOC-G: Assoc-G-ID 30|                |
     |                           |                |
     | --PCUpd ----------------->|                | Add a new LSP
     |   LSP Obj: PLSP-ID=4      |                | to Association Group
     |   + ASSOC-G: Assoc-G-ID 30|                |
     |                           |                |
     |<--PCRpt ----------------- |                |
     |   LSP Obj: PLSP-ID=4      |                |
     |   + ASSOC-G: Assoc-G-ID 30|                |





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   [Load Balancing Execution]
     | --PCUpd------------------>|                |
     |   LSP Obj: PLSP-ID=0x0000 |                |
     |   + D-CTRL:               |        :       |
     |    Origin Assoc-G-ID 10(O=up)      :       |
     |    Target Assoc-G-ID 30(O=active)  :       |
     |                           |))))))))))))))))| Balancing
     |                           |)})})})})})})})}| Execution
     |                           |        :       |
     |<--PCRpt------------------ |        :       |
     |   LSP Obj: PLSP-ID=0x0000 |        :       |
     |   + D-CTRL:               |        :       |
     |    Origin Assoc-G-ID 10(O=up)              |
     |    Target Assoc-G-ID 30(O=active)          |
     |   + D-REPORT:             |                |
     |    PLSP-ID 3, 50%         |                |
     |    PLSP-ID 4, 50%         |                |
     |                           |                |




                 Figure 5: Load-Balance Operation Example

6.3.  Load balancing operation (100:0 => 66:33)

   The scenario is one where the starting state is a single LSP (of
   bandwidth 100 M) is carrying the traffic.  But as the data traffic
   load increases another 50 M is required.  The PCE may want to create
   another LSP of 50 M, and load balance the traffic over the existing
   and new LSP.  To accomplish this, two association groups are used,
   the first (say association group ID 10) contains the LSP carrying the
   traffic, and the second (say association group ID 40) contains the
   new initiated LSP as well as the original LSP.  Expected PCUpd, PCRpt
   messages to create association group and to trigger load-balance
   follow (The instantiation of the original LSP of bandwidth 100M and
   its association into group ID 10 is not shown)

    PCE                         PCC(Ingress)     Egress

   [LSP Creation]
     |                           |                |
     | --PCInitiate ------------>|                |
     |      BW: 50M              | --Path ------->|
     |                           |<-----Resv ---- | Establish new
     |<--PCRpt ----------------- |                | PCE-Initiated LSP
     |   LSP Obj: PLSP-ID=5      |                |
     |                                            |



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   [LSP Association for PCE-Initiated LSPs]
     |                           |                |
     | --PCUpd ----------------->|                | Create new
     |   LSP Obj: PLSP-ID=5      |                | Association Group
     |   + ASSOC-G: Assoc-G-ID 40|                | for PCE-Initiated
     |                           |                | LSP
     |<--PCRpt ----------------- |                |
     |   LSP Obj: PLSP-ID=5      |                |
     |   + ASSOC-G: Assoc-G-ID 40|                |
     |                           |                |
     | --PCUpd ----------------->|                | Add the old LSP
     |   LSP Obj: PLSP-ID=1      |                | to the Association
     |   + ASSOC-G: Assoc-G-ID 40|                | Group
     |                           |                |
     |<--PCRpt ----------------- |                |
     |   LSP Obj: PLSP-ID=1      |                |
     |   + ASSOC-G: Assoc-G-ID 40|                |


   [Load Balancing Execution]
     | --PCUpd------------------>|                |
     |   LSP Obj: PLSP-ID=0x0000 |                |
     |   + D-CTRL:               |        :       |
     |    Origin Assoc-G-ID 10(O=up)      :       |
     |    Target Assoc-G-ID 40(O=active)  :       |
     |                           |))))))))))))))))| Balancing
     |                           |)})})})})})})})}| Execution
     |                           |        :       |
     |<--PCRpt------------------ |        :       |
     |   LSP Obj: PLSP-ID=0x0000 |        :       |
     |   + D-CTRL:               |        :       |
     |    Origin Assoc-G-ID 10(O=up)              |
     |    Target Assoc-G-ID 40(O=active)          |
     |   + D-REPORT:             |                |
     |    PLSP-ID 1, 66%         |                |
     |    PLSP-ID 5, 33%         |                |
     |                           |                |




                 Figure 6: Load-Balance Operation Example


7.  Redundant stateful PCEs

   Association group IDs are unique within a PCEP session across the
   primary PCE and the PCC.  A backup PCE has to synchronize the



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   association group IDs, PCE that created the association group and
   balancing percentages in advance of the failure on the primary PCE.
   One practical method to synchronize is a PCC replicates each PCRpt
   message for the backup PCEP session.  A backup PCE is able to receive
   the association group IDs from ASSOCIATION-GROUP TLV and the result
   of balancing percentages from DATA-REPORT TLV.


8.  Security Considerations

   This document defines extensions to PCEP to control load balancing of
   traffic across multiple LSPs or to completely switch traffic from one
   LSP to another.  The nature of these extensions results in more
   information being available for a hypothetical adversary and a number
   of additional attack surfaces which must be protected.  As a general
   precaution, it is RECOMMENDED that these PCEP extensions only be
   activated on authenticated and encrypted sessions across PCEs and
   PCCs belonging to the same administrative authority

   In addition to the security considerations and recommendations
   described in [I-D.ietf-pce-stateful-pce], the following also apply.

8.1.  Malicious PCE

   A malicious PCE may flap the traffic between several LSPs, creating
   shifting patterns in the network and excessive load on the PCC.  A
   PCC may protect itself from such an attack by enforcing a limit on
   the number of data-control requests per unit of time and MAY take
   additional steps ranging from delegation revocation to closing the
   PCEP session.

8.2.  Malicious PCC

   Because the PCE keeps state regarding LSP associations for all the
   PCCs, it is RECOMMENDED that the PCE have a bound on the amount of
   state each PCC can occupy, and in the context of this draft, the
   number of associations on a PCC and the number of associations each
   LSP may be part of.  Otherwise, a malicious PCC may create an
   unbounded number of associations.  Additionally, a malicious PCC may
   purposely fail data-control messages in order to force the PCE to
   continuously resend them and create artificial load on the PCE.  The
   PCE may protect itself from these situations by placing a limit on
   the number of failures and closing the PCEP session.


9.  IANA Considerations





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9.1.  PCEP TLV Indicators

   This document defines the following new PCEP TLVs:

     Value     Meaning              Reference
       TBD     DATA-CONTROL         This document
       TBD     DATA-REPORT          This document


9.2.  PCEP Error Objects

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

   Error-Type  Meaning
       6       Mandatory Object missing
                Error-value=TBD:  DATA-CONTROL TLV missing.
                Error-value=TBD:  DATA-REPORT TLV missing.

       19      Invalid operation
                Error-value=TBD:  No association group existing.
                Error-value=TBD:  No association group specified.
                Error-value=TBD:  No PLSP can be added to
                                  the active association group.



10.  Acknowledgments

   Many thanks to Adrian Farrel for their ideas and suggestions.


11.  References

11.1.  Normative References

   [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-00 (work in
              progress), December 2013.

   [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.




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

   [RFC4872]  Lang, J., Rekhter, Y., and D. Papadimitriou, "RSVP-TE
              Extensions in Support of End-to-End Generalized Multi-
              Protocol Label Switching (GMPLS) Recovery", RFC 4872,
              May 2007.

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

11.2.  Informative References

   [I-D.tanaka-pce-stateful-pce-mbb]
              Tanaka, Y. and Y. Kamite, "Make-Before-Break MPLS-TE LSP
              restoration and reoptimization procedure using Stateful
              PCE", draft-tanaka-pce-stateful-pce-mbb-02 (work in
              progress), October 2013.

   [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.


Authors' Addresses

   Yosuke Tanaka
   NTT Communications Corporation
   Granpark Tower
   3-4-1 Shibaura, Minato-ku
   Tokyo  108-8118
   Japan

   Email: yosuke.tanaka@ntt.com


   Yuji Kamite
   NTT Communications Corporation
   Granpark Tower
   3-4-1 Shibaura, Minato-ku
   Tokyo  108-8118
   Japan

   Email: y.kamite@ntt.com






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   Ina Minei
   Google
   US

   Email: inaminei@google.com


   Dhruv Dhody
   Huawei Technologies
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   Email: dhruv.ietf@gmail.com





































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