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Versions: 00 01 02 03 04 05 06 07 RFC 5852

CCAMP Working Group                                          D. Caviglia
Internet-Draft                                             D. Ceccarelli
Intended status: Standards Track                             D. Bramanti
Expires: August 19, 2010                                        Ericsson
                                                                   D. Li
                                                     Huawei Technologies
                                                             S. Bardalai
                                                         Fujitsu Network
                                                       February 15, 2010


 RSVP-TE Signaling Extension For Management Plane To Control Plane LSP
             Handover In A GMPLS Enabled Transport Network.
                 draft-ietf-ccamp-pc-spc-rsvpte-ext-07

Abstract

   In a transport network scenario, where Data Plane connections are
   controlled either by a Generalized Multi-Protocol Label Switching
   (GMPLS) Control Plane (Soft Permanent Connections - SPC) or by a
   Management System (Permanent Connections - PC) may independently
   coexist, the ability of transforming an existing PC into a SPC and
   vice versa - without actually affecting Data Plane traffic being
   carried over it - is a requirement.  The requirements for the
   conversion between permanent connections and switched connections in
   a GMPLS Network are defined in [RFC5493].

   This memo describes an extension to GMPLS RSVP-TE signaling that
   enables the transfer of connection ownership between the Management
   and the Control Planes.  Such a transfer is referred to as a
   Handover.  This document defines all Handover related procedures.
   This includes the handling of failure conditions and subsequent
   reversion to original state.  A basic premise of the extension is
   that the handover procedures must never impact an already established
   Data plane connection.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any



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   time.  It is inappropriate to use Internet-Drafts as reference
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   The list of current Internet-Drafts can be accessed at
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   This Internet-Draft will expire on August 19, 2010.

Copyright Notice

   Copyright (c) 2010 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
     1.1.  Dedication . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Procedures . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     4.1.  MP to CP handover: LSP Ownership Transfer From
           Management Plane To Control Plane  . . . . . . . . . . . .  6
     4.2.  MP to CP Handover Procedure Failure Handling . . . . . . .  7
       4.2.1.  MP to CP Handover Failure - Path Failure . . . . . . .  7
         4.2.1.1.  MP to CP Handover Failure - Path message and
                   Data Plane Failure . . . . . . . . . . . . . . . .  7
         4.2.1.2.  MP to CP Handover Failure - Path message and
                   Communication failure  . . . . . . . . . . . . . .  8
       4.2.2.  MP to CP Handover Failure - Resv Error . . . . . . . .  9
         4.2.2.1.  MP to CP Handover Failure - Resv Error and
                   Data Plane failure . . . . . . . . . . . . . . . .  9
         4.2.2.2.  MP to CP Handover Failure - Resv Error and
                   Communication failure  . . . . . . . . . . . . . . 10
         4.2.2.3.  MP to CP Handover Failure - Node Graceful
                   Restart  . . . . . . . . . . . . . . . . . . . . . 12
     4.3.  CP to MP handover : LSP Ownership Transfer From
           Control Plane To Management Plane  . . . . . . . . . . . . 14
     4.4.  CP to MP Handover Procedure Failure  . . . . . . . . . . . 15
   5.  Minimum Information for MP to CP Handover  . . . . . . . . . . 17
   6.  RSVP Message Formats . . . . . . . . . . . . . . . . . . . . . 18
   7.  Objects Modification . . . . . . . . . . . . . . . . . . . . . 18
     7.1.  Administrative Status Object . . . . . . . . . . . . . . . 18
     7.2.  Error Spec Object  . . . . . . . . . . . . . . . . . . . . 18
   8.  Compatibility  . . . . . . . . . . . . . . . . . . . . . . . . 19
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 19
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
   11. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 20
   12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 20
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 21
     13.2. Informational References . . . . . . . . . . . . . . . . . 21
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21












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1.  Introduction

   In a typical traditional transport network scenario, Data Plane (DP)
   connections between two endpoints are controlled by means of a
   Network Management System (NMS) operating within the Management Plane
   (MP).  NMS/MP is the owner of such transport connections, being
   responsible of their set up, tear down and maintenance.

   The adoption of a Generalized MPLS (GMPLS) [RFC3945] Control Plane
   (CP) in a network that is already in service - controlled by NMS at
   MP level - introduces the need for a procedure able to coordinate a
   controlled handover of a data plane connection from MP to CP.

   In addition, the control handover in the opposite direction, from CP
   to MP should be possible as well.  The procedures described in this
   memo can be applied to a Label Switched Path (LSP) in any DP
   switching technology and any network architecture.

   This memo describes an extension to GMPLS Resource reSerVation
   Protocol - Traffic Engineering (RSVP-TE) [RFC3471], [RFC3473]
   signaling that enables the handover of connection ownership between
   the Management and the Control Planes.  All handover related
   procedures are defined below.  This includes the handling of failure
   conditions and subsequent reversion to original state.  A basic
   premise of the extension is that the handover procedures must never
   impact the exchange of user data on LSPs that are already established
   in the DP.

1.1.  Dedication

   We would like to dedicate this work to our friend and colleague Dino
   Bramanti, who passed away at the early age of 38.  Dino has been
   involved in this work since its beginning.


2.  Terminology

   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].


3.  Motivation

   The main motivation behind this work is the definition of a simple
   and very low impact procedure that satisfies the requirements defined
   in [RFC5493].  Such a procedure is aimed at giving the transport
   network operators the chance to handover the ownership of existing



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   LSPs provisioned by NMS from the MP to the CP without disrupting user
   traffic flowing on them.  Handover from MP to CP (i.e. when existing
   DP connection ownership and control is passed from MP to CP) has been
   defined as a mandatory requirement, while the opposite operation, CP
   to MP handover, has been considered as a nice-to-have feature that
   can be seen as an emergency procedure to disable the CP and take the
   manual control of the LSP.  For more details on requirements and
   motivations please refer to [RFC5493].


4.  Procedures

   The modification defined in this document refers only to the
   ADMIN_STATUS Object, that is, the message flow is left unmodified for
   both LSP set-up and deletion.  Moreover a new Error Value is defined
   to identify the failure of a Handover procedure.

   The following paragraphs give detailed description of the "MP to CP
   handover" and "CP to MP handover" procedures, based on the usage a
   newly defined bit called H bit.

   Just as when setting up an LSP using the CP [RFC3473], the Path
   message may contain full information about the explicit route
   including the links and labels traversed by the LSP.  This
   information is encoded in the Explicit Route Object (ERO), and must
   be supplied by the MP using details recorded when the LSP was
   provisioned, or collected by the MP by inspecting the nodes along the
   path.

   Alternatively, and also just as when setting up an LSP using the CP
   [RFC3473] the ERO may include less information such that the details
   of the next hop have to be determined by each node along the LSP as
   it processes the Path message.  This approach may be desirable when
   the full information is not available to the MP or cannot be passed
   to the head-end node when initiating the handover from MP to CP.

   This section (Section 4) describes the general procedures and
   protocol extensions for MP to CP handover, and uses the case of a
   fully detailed ERO to describe the mechanism.  Section 5 describes
   how each node behaves in the case of a limited amount of information
   in the ERO.

   Note that when handover is being performed for a bidirectional LSP
   and the ERO contains full information including labels, the ERO
   SHOULD include both upstream and downstream labels.  Per Section
   5.1.1 of [RFC3473], the labels are indicated on an output basis; this
   means that the labels are used by the upstream node to create the
   LABEL_SET Object and, for bidirectional LSPs, the UPSTREAM_LABEL



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   Object used in the outgoing Path message.

4.1.  MP to CP handover: LSP Ownership Transfer From Management Plane To
      Control Plane

   The MP to CP handover procedure MUST create an RSVP-TE session along
   the path of the LSP to be moved from MP to CP, associating it to the
   existing cross-connected resources owned by the MP (e.g. lambdas,
   time slots or reserved bandwidth) and at the same time transferring
   their ownership to the CP.

   The operator instructs the ingress node to handover control of the
   LSP from the MP to the CP.  In this handover mode, it supplies the
   exact path of the LSP including any resource reservation and label
   information.

   The ingress MUST check that no corresponding Path state exists and
   that corresponding Data Plane state does exist.  If there is an
   error, this MUST be reported to the operator and further protocol
   action MUST NOT be taken.

   The ingress signals the LSP using a Path message with the H bit and R
   bit set in the ADMIN_STATUS object.  In this mode of handover, the
   Path message also carries an ERO that includes Label subobjects
   indicating the labels used by the LSP at each hop.  The ingress MUST
   start the Expiration timer (see Section 4.2.1.2 for expiration of
   this timer).  Such timer SHOULD be configurable per LSP and have a
   default value of 30 seconds.

   Each Label Switching Router (LSR) that receives a Path message with
   the H bit set checks to see whether there is any matching Path state.

      - If matching Path state is found with the H bit set, this is a
      Path refresh and should be treated accordingly [RFC3473].
      - If matching Path state is found with the H bit clear, this is an
      error and MUST be treated according to the error case description
      in Section 4.2.1.1
      - If no Path state is found, the LSR goes on to check whether
      there is any matching Data Plane state.
      - If no matching Data Plane state is found (including only
      partially matching Data Plane state), this is an error or a race
      condition.  It MUST be handled according to the description in
      Section 4.2.1.1
      - If matching Data Plane state is found, the LSR MUST save the
      Path state (including the set H bit), and MUST forward the Path
      message to the egress.  The LSR MUST retain any MP state
      associated with the LSP at this point.




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   An egress LSR MUST act as any other LSR, except that there is no
   downstream node to which to forward the Path message.  If all checks
   are passed, the egress MUST respond with a Resv with the H bit set.

   A transit LSR MUST process each Resv according to the normal rules of
   [RFC3473].

   When an ingress LSR receives a Resv message carrying the H bit set,
   it checks the Expiration Timer.

   - If the timer is not running, the Resv is treated as a refresh and
   no special action is taken [RFC3473].

   - If the timer is running, the ingress MUST cancel the timer and
   SHOULD notify the operator that the first stage of handover is
   complete.  The ingress MUST send a Path message that is no different
   from the previous message except that the H bit MUST be clear.

   The Path message with the H bit clear will travel the length of the
   LSP and will result in the return of a Resv with the H bit clear
   according to normal processing [RFC3473].  As a result, the H bit
   will be cleared in the stored Path state at each transit LSR and at
   the egress LSR.  Each LSR SHOULD release any associated MP state
   associated with the LSP when it receives the Path message with H bit
   clear, but MAY retain the information according to local policy for
   use in future MP processing.

   When the ingress receives a Resv with the H bit clear, the handover
   is completed.  The ingress SHOULD notify the operator that the
   handover is correctly completed.

4.2.  MP to CP Handover Procedure Failure Handling

   In the case of MP to CP Handover, two different failure scenarios can
   happen: Path Failure and Resv Failure.  Moreover, each failure can be
   due to two different causes: DP failure or Communication Failure.  In
   any case the LSP ownership MUST be immediately rolled back to the one
   previous to the handover procedure.  A section for each combination
   will be analyzed in the following.

4.2.1.  MP to CP Handover Failure - Path Failure

4.2.1.1.  MP to CP Handover Failure - Path message and Data Plane
          Failure

   In this paragraph we will analyze the case where the handover
   procedure fails during the Path message processing.




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     |      Path      |                |                |
     |--------------->|      Path      |                |
     |                |---------------X|                |
     |                |    PathErr     |                |
     |    PathErr     |<---------------|                |
     |<---------------|                |                |
     |                |                |                |
   Ingress LER      LSR A            LSR B       Egress LER

                 Figure 1: MP2CP - Path Msg and DP Failure

   If an error occurs, the node detecting the error MUST respond to the
   received Path message with a PathErr message, and MUST abort the
   handover procedure.  The PathErr message SHOULD have the
   Path_State_Removed flag set [RFC3473], but implementations MAY retain
   their local state and wait for Path state timeout as per normal RSVP
   processing.

   Nodes receiving a PathErr message MUST follow standard PathErr
   message processing and the associated DP resources MUST NOT be
   impacted.  If the local CP state indicates that a Handover is in
   progress (based on the H bit in the Path message) the LSR MUST revert
   the LSP ownership to the MP.

4.2.1.2.  MP to CP Handover Failure - Path message and Communication
          failure

   Other possible scenarios are shown in the following pictures and are
   based on the inability to reach a node along the path of the LSP.

   The below scenario postulates the usage of a reliable message
   delivery based on the mechanism defined in [RFC2961].



     |      Path      |                |                |
     |--------------->|      Path      |                |
     |                |---------------X|                |
     |                |---------------X|                |
     |                |      ...       |                |
     |                |---------------X|                |
     |                |                |                |
   Ingress LER      LSR A            LSR B       Egress LER

      Figure 2: MP2CP - Path Msg and Communication Failure (reliable
                                 delivery)

   The Path message sent from LSR A towards LSR B is lost or does not



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   reach the destination for any reason.  As a reliable delivery
   mechanism is implemented, LSR A retransmits the Path message for a
   configurable number of times and if no ack is received the handover
   procedure will be aborted (via the Expiration timer).

   In the next scenario RSVP-TE messages are sent without reliable
   message delivery, that is, no [RFC2961] MessageID procedure is used.




        |      Path      |                |                |
        |--------------->|      Path      |                |
        |                |----------X     |                |
        |                |                |                |
   TIMER EXPIRES         |                |                |
        |   Path Tear    |   Path Tear    |   Path Tear    |
        |--------------->|--------------->|--------------->|
        |                |                |                |
      Ingress LER      LSR A            LSR B       Egress LER

     Figure 3: MP2CP - Path Msg and Communication Failure (no reliable
                                 delivery)

   If the Resv message is not received before the expiration of the
   Expiration timer the handover procedure is aborted as described in
   Section 4.2.1.1.  Please note that any node that has forwarded a Path
   (LSR A), i.e. has installed local path state, will send a PathTear
   when that state is removed (accordingly to [RFC2205]).

4.2.2.  MP to CP Handover Failure - Resv Error

4.2.2.1.  MP to CP Handover Failure - Resv Error and Data Plane failure

   In the case of failure occurrence during the Resv message processing,
   (in case there has been any change in the data plane during the
   signaling) the node MUST send a PathErr message [RFC2205] in the
   upstream direction.  The PathErr message is constructed and processed
   as defined above in Section 4.2.1.1.  The failure detection node MUST
   also send a PathTear message downstream.  The PathTear message is
   constructed and processed as defined above in Section 4.2.1.1.










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     |      Path      |      Path      |      Path      |
     |--------------->|--------------->|--------------->|
     |                |                |      Resv      |
     |                |      Resv      |<---------------|
     |                |X---------------|                |
     |    PathErr     |    PathTear    |    PathTear    |
     |<---------------|--------------->|--------------->|
     |                |                |                |
   Ingress LER      LSR A            LSR B       Egress LER

                Figure 4: MP2CP - Resv Error and DP Failure

   In the case shown in Figure 4, the failure occurs in LSR A. A
   PathTear message is sent towards B and a PathErr message (with
   ErrorCode set to "Handover Procedure Failure") is sent in the
   upstream direction.  The PathErr and PathTear messages remove the
   Path state established by the Path messages along the nodes of the
   LSP and abort the handover procedure.

   Please note that the failure occurred after the handover procedure
   was successfully completed in LSR B, but Handover state will still be
   maintained locally as, per Section 4.1, a Path message with the H bit
   clear will have not yet been sent or received.  A node that receives
   a PathTear when it has Path state with the H bit set MUST remove Path
   state, but MUST NOT change data plane state.  It MUST return LSP
   ownership to the MP.

4.2.2.2.  MP to CP Handover Failure - Resv Error and Communication
          failure

   When a Resv message cannot reach one or more of the upstream nodes,
   the procedure is quite similar to the one previously seen about the
   Path message.  Even in this case it is possible to distinguish two
   different scenarios.

   In the first scenario we consider the utilization of a reliable
   message delivery based on the mechanism defined in [RFC2961].  After
   a correct forwarding of the Path message along the nodes of the LSP,
   the Egress LSR sends a Resv message in the opposite direction.  It
   might happen that the Resv message does not reach the ingress Label
   Edge Router (LER) or an LSR, say LSR A. LSR B MUST send a Resv
   message again for a configurable number of times and then, if the
   delivery does not succeed, the adoption procedure will be aborted
   (via the Expiration timer).







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     |      Path      |      Path      |      Path      |
     |--------------->|--------------->|--------------->|
     |                |                |      Resv      |
     |                |      Resv      |<---------------|
     |                |      X---------|                |
     |                |      X---------|                |
     |                |      ...       |                |
     |                |      X---------|                |
     |                |                |                |
   Ingress
         LSR A            LSR B       Egress LER

     Figure 5: MP2CP - Resv Error and Communication Failure (reliable
                                 delivery)

   Considering that the Resv message did not manage to reach LSR A, it
   is highly probable that the PathErr would fail too.  Due to this
   fact, the Expiration timer is used on the Ingress LER after sending
   the path and on LSR A after forwarding it.  When the timer expires,
   if no Resv or PathErr message is received, the handover procedure is
   aborted as described in Section 4.2.1.1 and the LSP ownership
   returned to the Management Plane.

   Figure 6, on the other hand, shows the scenario in which no reliable
   delivery mechanism is implemented.




           |      Path      |      Path      |      Path      |
           |--------------->|--------------->|--------------->|
           |                |                |      Resv      |
           |                |      Resv      |<---------------|
           |                |      X---------|                |
   TIMER EXPIRES            |                |                |
           |   Path Tear    |   Path Tear    |   Path Tear    |
           |--------------->|--------------->|--------------->|
           |                |                |                |
      Ingress LER      LSR A            LSR B       Egress LER

    Figure 6: MP2CP - Resv Error and Communication Failure (no reliable
                                 delivery)

   If non Resv message is received before the Expiration timer expires,
   the ingress LER follows the same procedure defined in Section 4.1.






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4.2.2.3.  MP to CP Handover Failure - Node Graceful Restart

   In the case of node restart and graceful restart is enabled then one
   of the following scenarios will happen.

   Case I - Finite Restart Time

   In this case, the Restart Time (see [RFC3473]) is finite, i.e., not a
   value of 0xffffffff.  In the sequence diagram below, assume LSR A
   restarts.  If the ingress LER does not receive the Resv message in
   time it MUST abort the handover process by generating a PathTear
   message downstream.  Also, if LSR A does not complete the restart
   process within the restart time interval then LSR B MUST start
   tearing down all LSPs between LSR A and LSR B and this includes the
   LSP that is being used to carry out the handover of MP resources to
   CP.  LSP B MUST generate a PathTear message downstream and a PathErr
   message upstream.  Both LSR B and the egress LER MUST NOT release the
   DP resources because in both nodes the H bit is set in the local Path
   state.




     |      Path      |      Path      |      Path      |
     |--------------->|--------------->|--------------->|
     |                |                |      Resv      |
     |                |      Resv      |<---------------|
     |                X      X---------|                |
     |   PathTear                      |                |
     |-------X                   Restart Timer          |
     |                              Expires             |
     |                     PathErr     |    PathTear    |
     |                        X--------|--------------->|
     |                                 |                |
     |                X                |                |
     |                |                |                |
   Ingress LER      LSR A            LSR B       Egress LER

             Figure 7: MP2CP - Node graceful restart - Case I

   Case II - Infinite Restart Time

   In this case, the Restart Time (see [RFC3473]) indicates that the
   restart of the sender's control plane may occur over an indeterminate
   interval, i.e., is 0xffffffff.  The sequence is quite similar to the
   previous one.  In this sequence the restart timer will not expire in
   LSR B since it is run infinitely.  Instead after LSR A restarts LSR B
   MUST start the recovery timer.  The recovery timer will expire since



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   there will be no Path message with the RECOVERY LABEL received from
   LSR A given the ingress node had already removed the local Path state
   after it aborts the handover process.  Thus LSR B MUST tear-down the
   specific LSP that is being used to convert the MP resources to CP by
   generating a PathTear message downstream and PathErr message
   upstream.  Similarly to the previous case both LSR B and the egress
   LER MUST NOT release the DP resources because the H bit is set in the
   local Path state.




     |      Path      |      Path      |      Path      |
     |--------------->|--------------->|--------------->|
     |                |                |      Resv      |
     |                |      Resv      |<---------------|
     |                X      X---------|                |
     |   PathTear                      |                |
     |-------X                         |                |
     |                                 |                |
     |                X                |                |
     |                |                |                |
     |                |          Recovery Timer         |
     |                |             Expires             |
     |    PathErr     |    PathErr     |    PathTear    |
     |<---------------|<---------------|--------------->|
     |                |                |                |
   Ingress LER      LSR A            LSR B       Egress LER

             Figure 8: MP2CP - Node graceful restart - Case II

   Case III

   In this case, the ingress LER does not abort the handover process.
   When LSR A restarts, the ingress LER detects the restart and MUST re-
   generate the Path message with the H bit set in order to re-start the
   handover.

   When LSR B receives the Path message, it sees the H-bit set on the
   message and also sees that it has the H-bit set in its own state and
   that it has sent the Resv.  But it is also aware that LSR A has
   restarted and could have sent a Path message with a RECOVERY LABEL
   object.  LSR B may attempt to resume the handover process or may
   abort the handover.  This choice is made according to local policy.

   If resuming the handover, LSR B MUST treat the received Path message
   as a retransmission, and MUST retransmit its Resv.  If aborting
   handover, LSR B MUST return a PathErr and MUST send a PathTear



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   downstream.  In both cases, LSR B MUST NOT modify the DP state.




     |      Path      |      Path      |      Path      |
     |--------------->|--------------->|--------------->|
     |                |                |      Resv      |
     |                |      Resv      |<---------------|
     |                X      X---------|                |
     |                                 |                |
     |                X                |                |
     |                |                |                |
     |      Path      |      Path      |                |
     |--------------->|--------------->|                |
     |    PathErr     |    PathErr     |    PathTear    |
     |<---------------|<---------------|--------------->|
     |                |                |                |
   Ingress LER      LSR A            LSR B       Egress LER

            Figure 9: MP2CP - Node graceful restart - Case III

4.3.  CP to MP handover : LSP Ownership Transfer From Control Plane To
      Management Plane

   Let's now consider the case of LSP Ownership Transfer From Control
   Plane To Management Plane.  Also in this section we will analyze the
   handover procedure success and failure.

   The scenario is still a DP connection between two nodes acting as
   ingress and egress for a LSP, but in this case the CP has the
   ownership and control of the LSP.  The CP to MP handover procedure
   MUST delete the existing RSVP-TE session information and MUST NOT
   affect the cross-connected resources, but just move their ownership
   to the MP.

   In other words, after LSP ownership transfer from CP to MP, the LSP
   is no longer under control of RSVP-TE, which is no more able to "see"
   the LSP itself.  The CP to MP handover procedure MUST be a standard
   LSP deletion procedure as described in Section 7.2.1 of [RFC3473].
   The procedure is initiated at the ingress node of the LSP by a MP
   entity.  Ingress node and MP exchange the relevant information for
   this task and then propagate it over CP by means of RSVP-TE tear down
   signaling as described below.

   The ingress node MUST send a Path message in the downstream direction
   with Handover and Reflect bits set in the ADMIN_STATUS Object.  No
   action is taken over the DP and transit LSRs must forward such



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   message towards the egress node.  All of the nodes MUST keep track of
   the procedure storing the H bit in their local Path and Resv states.
   Then every node waits for the H bit to be received within the related
   Resv message.  After the Resv message is received by the ingress LER,
   it MUST send a PathTear message in order to clear the whole LSP
   information recorded on the RSVP-TE data structures of the nodes.
   Downstream nodes processing a PathTear message which follows a Path
   message with the H bit set, MUST NOT remove any associated data plane
   state.  In other words, a normal LSP tear down signaling is exchanged
   between nodes traversed by the LSP, but H bit set in the Path message
   indicates that no DP action has to correspond to CP signaling.

4.4.  CP to MP Handover Procedure Failure

   Failures during CP to MP handover procedure MUST NOT result in the
   removal of any associated data plane state.  To that end, when a Resv
   message containing an ADMIN_STATUS Object with the H bit is not
   received during the period of time described in Section 7.2.2. of
   [RFC3473] different processing is required.  While the H bit is set
   in the Path state, a node MUST NOT send a PathTear when a failure is
   detected.  Instead, the failure is reported upstream using a PathErr.
   The only node that can send a PathTear is the ingress node, and it
   can only do this as a step in the procedures specified in this
   document.  This applies to both MP to CP and CP to MP handover.  The
   ingress node MAY choose to report the failure in the CP to MP
   handover procedure via the MP.

   The CP to MP handover procedure can fail also due to two causes:
   PathTear lost or node down.  In the former case, if the LSP is not
   under MP control after the Expiration Timer elapses, a manual
   intervention from the network operator is requested, while in the
   latter case different scenarios may happen:

   - CASE I - Path message and node down



           |      Path      |      Path      X                |
           |--------------->|--------------X                  |
           |                |                                 |
           |                |                X                |
           |                |                |                |
           |                |                |                |
      Ingress LER      LSR A            LSR B       Egress LER

              Figure 10: Case I - Path message and node down

   Per [RFC3473] section 7.2.2 the ingress node should wait for a



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   configurable amount of time (30 seconds by default) and then send a
   PathTear message.  In this case the normal deletion procedure MUST
   NOT be followed.  When the Expiration timer elapses a manual
   intervention from network operator is requested and normal, i.e., pre
   CP to MP handover, LSP processing continues.

   - CASE II - Resv message and node down



           |      Path      |      Path      |      Path      |
           |--------------->|--------------->|--------------->|
           |                |                |      Resv      |
           |                |      Resv      |<---------------|
           |                X      X---------|                |
           |                                 |                |
           |                X                |                |
           |                |                |                |
      Ingress LER      LSR A            LSR B       Egress LER

              Figure 11: Case II - Resv message and node down

   The procedure to be followed is the same depicted in CASE I. The
   network operator can ask for the automatic CP to MP procedure again
   after the failed node comes back up.  Per [RFC3473] section 7.2 the
   nodes will forward the new Path and Resv messages correctly.

   - CASE III - PathTear message and node down



           |      Path      |      Path      |      Path      |
           |--------------->|--------------->|--------------->|
           |      Resv      |      Resv      |      Resv      |
           |<---------------|<---------------|<---------------|
           |    PathTear    |                |                |
           |--------------->|    PathTear    X                |
           |                |------------X                    |
           |                |                X                |
           |                |                |                |
      Ingress LER      LSR A            LSR B       Egress LER

           Figure 12: Case III - PathTear message and node down

   This scenario can be managed as a normal PathTear lost described
   above in this section.





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5.  Minimum Information for MP to CP Handover

   As described in Section 4, it is also possible for the ERO to contain
   less than the full set of path information for the LSP being handed
   over.  This arises when only a minimal set of information is handed
   to the CP by the MP at the LSP's head end.  Instead of collecting all
   of the LSP information (including the labels) and formatting it into
   an ERO, as described in Section 4, it is possible to start with a
   minimum amount of information.  The full ERO method and the
   partial/no ERO method are not mutually exclusive; support of both
   methods are required.

   At the ingress node, the information needed to specify the LSP is the
   outgoing interface ID, upstream label and downstream label of this
   interface and the egress node ID.  The remaining information about an
   existing LSP can then be collected hop by hop, as the signaling is
   going on, by looking up the cross-connection table in DP at each node
   along the LSP path.

   Starting from the information available at ingress LER about the
   outgoing interface ID of that ingress node, the incoming interface ID
   of next hop can be found by looking up the link resource table/
   database in the LER itself.

   The Path message is hence built with the LABEL_SET Object ([RFC3473])
   and the UPSTREAM_LABEL Object ([RFC3473]), where the upstream label
   and downstream label of ingress outgoing interface of the LSP are
   included in these two objects.  In addition to above mentioned
   objects, the Path message MUST include the ADMIN_STATUS Object with H
   bit set, as already defined in previous chapters for the detailed ERO
   based way of proceeding.  Such handover Path is sent to the incoming
   interface of next hop.  When this Path message reaches the second
   node along the LSP path, the information about incoming interface ID
   and the upstream and downstream labels of this interface is extracted
   from it and it is used to find next hop outgoing interface ID and the
   upstream/downstream labels by looking up the DP cross-connection
   table.

   After having determined in this way the parameters describing the
   LSPs next hop, the outgoing Path message to be sent is built
   replacing the LABEL_SET Object and UPSTREAM_LABEL Object content with
   the looked-up values of upstream and downstream labels.

   By repeating this procedure for each transit node along the LSP, it
   is possible to make the handover Path message reach the egress node,
   exactly following the LSP that is in place over DP.  The ERO MAY in
   this case be included in the Path message as an optional object, and
   MAY be filled with the LSP relevant information down to either the



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   port level with interface ID or the Label level with upstream and
   downstream labels.  The ERO can be used to check the consistency of
   resource in DP down to the port level or label level at each
   intermediate node along the LSP path.

   Where the DP path continues beyond the egress, by indicating the
   Egress label at the head-end of an LSP, the traffic can be directed
   to the right destination.  The GMPLS Signaling Procedure for Egress
   Control is described in [RFC4003]


6.  RSVP Message Formats

   This memo does not introduce any modification in RSVP messages object
   composition.


7.  Objects Modification

   The modifications required concern two RSVP objects: the ADMIN_STATUS
   and the ERROR_SPEC Object.

7.1.  Administrative Status Object

   This memo introduces a new flag into the ADMIN_STATUS object.  The
   ADMIN_STATUS Object is defined in [RFC3473].  This document uses the
   H bit of the ADMIN_STATUS Object.  The bit is bit number (TBD by
   IANA) (25).

7.2.  Error Spec Object

   It is possible that a failure, such as the loss of DCN connection or
   the restart of a node, occurs during the LSP ownership handing over.
   In this case the LSP handover procedure is interrupted, the ownership
   of the LSP must remain with the ownership prior to the initiation of
   the handover procedure.  It is important that the transaction failure
   does not affect the DP.  The LSP is kept in place and no traffic hit
   occurs.

   The failure is signaled by PathErr in the upstream direction and
   PathTear Messages in the downstream direction.  The PathErr messages
   include an ERROR_SPEC Object specifying the causes of the failure.

   This memo introduces a new Error Code (with different Error Values)
   into the ERROR_SPEC Object, defined in [RFC2205].

   The defined Error Code is "Handover Procedure Failure", and its value
   is (TBD by IANA)(35).  For this Error Code the following Error Values



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   are defined:

      1 = Cross-connection mismatch

      2 = Other failure


8.  Compatibility

   The main requirement for Handover procedure to work is that all nodes
   along the path MUST support the extension defined in this draft.
   This requirement translates to an administrative requirement as it is
   not enforced at the protocol level.  As defined, non-supporting nodes
   will simply propagate the H bit without setting local state.  This
   may result in an impact on data traffic during the handover
   procedure.


9.  Security Considerations

   The procedures described in this document rely completely on RSVP-TE
   messages and mechanism.  The use of H bit set in ADMIN_STATUS Object
   basically informs the receiving entity that no operations are to be
   done over DP as consequence of such special signaling flow.  Using
   specially flagged signaling messages we want to limit the function of
   setup and tear down messages to CP, making them not effective over
   related DP resource usage.

   However the handover procedures allow the control plane to be used to
   take an LSP out of the control of the Management Plane.  This could
   cause considerable disruption and could introduce a new security
   concern.  As a consequence the use of GMPLS security techniques is
   more important.  For RSVP-TE Security please refer to [RFC3473],
   while for GMPLS security framework please refer to [sec-fwk].


10.  IANA Considerations

   IANA has been asked to manage the bit allocations for the
   ADMIN_STATUS Object ([RFC3473]).  This document requires the
   allocation of the Handover bit: the H bit.  IANA is requested to
   allocate a bit for this purpose.

Bit Number  Hex Value    Name                                 Reference
----------  -----------  -----------------------------------  ---------
25          0x00000040   Handover (H)                         [This.I-D]





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   IANA has also been asked to allocate a new error code:

     35  Handover failure

         This Error Code has the following globally-defined Error
         Value sub-code:

             1 =  Cross-connection mismatch
             2 =  Other failure


11.  Acknowledgments

   We wish to thank Adrian Farrel, Lou Berger, Alan Elder, and Ben
   Campbell for their assistance and precious advices to prepare this
   draft for publication.  We also wish to thank Nicola Ciulli
   (Nextworks) who contributed to the initial stage of this draft.


12.  Contributors

      Shan Zhu
      Fujitsu Network Communications Inc.
      2801 Telecom Parkway,
      Richardson, Texas 75082 USA
      Email: Shan.Zhu@us.fujitsu.com
      Tel: +1-972-479-2041

      Igor Bryskin
      ADVA Optical Networking Inc
      7926 Jones Branch Drive
      Suite 615
      McLean, VA - 22102
      Email: ibryskin@advaoptical.com

      Francesco Fondelli
      Ericsson
      Via Negrone 1/A
      Genova - 16145
      Email: francesco.fondelli@ericsson.com

      Lou Berger
      LabN Consulting, LLC
      Phone: +1 301 468 9228
      EMail: lberger@labn.net


13.  References



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13.1.  Normative References

   [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.

   [RFC2961]  Berger, L., Gan, D., Swallow, G., Pan, P., Tommasi, F.,
              and S. Molendini, "RSVP Refresh Overhead Reduction
              Extensions", RFC 2961, April 2001.

   [RFC3471]  Berger, L., "Generalized Multi-Protocol Label Switching
              (GMPLS) Signaling Functional Description", RFC 3471,
              January 2003.

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

   [RFC3945]  Mannie, E., "Generalized Multi-Protocol Label Switching
              (GMPLS) Architecture", RFC 3945, October 2004.

   [RFC4003]  Berger, L., "GMPLS Signaling Procedure for Egress
              Control", RFC 4003, February 2005.

13.2.  Informational References

   [RFC5493]  Caviglia, D., Bramanti, D., Li, D., and D. McDysan,
              "Requirements for the Conversion between Permanent
              Connections and Switched Connections in a Generalized
              Multiprotocol Label Switching (GMPLS) Network", RFC 5493,
              April 2009.

   [sec-fwk]  Fang, L., "Security Framework for MPLS and GMPLS
              Networks", July 2009.














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Authors' Addresses

   Diego Caviglia
   Ericsson
   Via A. Negrone 1/A
   Genova - Sestri Ponente
   Italy

   Email: diego.caviglia@ericsson.com


   Daniele Ceccarelli
   Ericsson
   Via A. Negrone 1/A
   Genova - Sestri Ponente
   Italy

   Email: daniele.ceccarelli@ericsson.com


   Dino Bramanti
   Ericsson



   Dan Li
   Huawei Technologies
   F3-5-B R&D Center, Huawei Base
   Shenzhen 518129
   P.R.China

   Email: danli@huawei.com


   Snigdho Bardalai
   Fujitsu Network
   2801 Telecom Parkway
   Richrdson, Texas 75082
   USA

   Email: Snigdho.Bardalai@us.fujitsu.com










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