[Docs] [txt|pdf|xml|html] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-raghu-pce-lsp-control-request) 00 01

PCE Working Group                                            A. Raghuram
Internet-Draft                                                A. Goddard
Intended status: Standards Track                           C. Yadlapalli
Expires: December 20, 2018                                          AT&T
                                                              J. Karthik
                                                            S. Sivabalan
                                                               J. Parker
                                                     Cisco Systems, Inc.
                                                                D. Dhody
                                                     Huawei Technologies
                                                           June 18, 2018


   Ability for a stateful PCE to request and obtain control of a LSP
                 draft-ietf-pce-lsp-control-request-01

Abstract

   The stateful Path Computation Element (PCE) communication Protocol
   (PCEP) extensions provide stateful control of Multiprotocol Label
   Switching (MPLS) Traffic Engineering Label Switched Paths (TE LSP)
   via PCEP, for a model where a Path Computation Client (PCC) delegates
   control over one or more locally configured LSPs to a stateful PCE.
   There are use-cases in which a stateful PCE may wish to request and
   obtain control of one or more LSPs from a PCC.  This document
   describes a simple extension to stateful PCEP to achieve such an
   objective.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

Status of This Memo

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

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

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



Raghuram, et al.        Expires December 20, 2018               [Page 1]


Internet-Draft             LSP Control Request                 June 2018


   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 December 20, 2018.

Copyright Notice

   Copyright (c) 2018 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
   (https://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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  LSP Control Request Flag  . . . . . . . . . . . . . . . . . .   4
   4.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  SRP Object Flags  . . . . . . . . . . . . . . . . . . . .   6
   7.  Manageability Considerations  . . . . . . . . . . . . . . . .   6
     7.1.  Control of Function and Policy  . . . . . . . . . . . . .   6
     7.2.  Information and Data Models . . . . . . . . . . . . . . .   6
     7.3.  Liveness Detection and Monitoring . . . . . . . . . . . .   6
     7.4.  Verify Correct Operations . . . . . . . . . . . . . . . .   6
     7.5.  Requirements On Other Protocols . . . . . . . . . . . . .   6
     7.6.  Impact On Network Operations  . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Stateful PCEP extensions [RFC8231] specifies a set of extensions to
   PCEP [RFC5440] 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,



Raghuram, et al.        Expires December 20, 2018               [Page 2]


Internet-Draft             LSP Control Request                 June 2018


   delegation of control of LSPs to PCEs, and PCE control of timing and
   sequence of path computations within and across PCEP sessions.  The
   stateful PCEP defines the following two useful network operations:

   o  Delegation: As per [RFC8051], an operation to grant a PCE
      temporary rights to modify a subset of LSP parameters on one or
      more LSPs of a PCC.  LSPs are delegated from a PCC to a PCE and
      are referred to as "delegated" LSPs.

   o  Revocation: As per [RFC8231], an operation performed by a PCC on a
      previously delegated LSP.  Revocation revokes the rights granted
      to the PCE in the delegation operation.

   For Redundant Stateful PCEs (section 5.7.4. of [RFC8231]), during a
   PCE failure, one of the redundant PCE could request to take control
   over an LSP.  The redundant PCEs MAY use a local policy or a
   proprietary election mechanism to decide which PCE would take
   control.  In this case, a mechanism is needed for a stateful PCE to
   request control of one or more LSPs from a PCC, so that a newly
   elected primary PCE can request to take over control.

   In case of virtualized PCEs (vPCE) running as virtual network
   function (VNF), as the computation load in the network increases, a
   new instance of vPCE could be instantiated to balance the current
   load.  The PCEs could use proprietary algorithm to decide which LSPs
   to be assigned to the new vPCE.  Thus having a mechanism for the PCE
   to request control of some LSPs is needed.

   In some deployments, the operator would like to use stateful PCE for
   global optimization algorithms but would still like to keep the
   control of the LSP at the PCC.  In such cases, a stateful PCE could
   request to take control during the global optimization and return the
   delegation once done.

   Note that [RFC8231] specify a mechanism for a PCC to delegate an
   orphaned LSP to another PCE.  The mechanism defined in this document
   can be used in conjunction to [RFC8231].  Ultimately, it is the PCC
   that decides which PCE to delegate the orphaned LSP.

   This specification provides a simple extension, by using this a PCE
   can request control of one or more LSPs from any PCC over the
   stateful PCEP session.  The procedures for granting and relinquishing
   control of the LSPs are specified in accordance with the
   specification [RFC8231].







Raghuram, et al.        Expires December 20, 2018               [Page 3]


Internet-Draft             LSP Control Request                 June 2018


2.  Terminology

   The following terminologies are used in this document:

   PCC:  Path Computation Client.

   PCE:  Path Computation Element

   PCEP:  Path Computation Element communication Protocol.

   PCRpt:  Path Computation State Report message.

   PCUpd:  Path Computation Update Request message.

   PLSP-ID:  A PCEP-specific identifier for the LSP.

3.  LSP Control Request Flag

   The Stateful PCE Request Parameters (SRP) object is defined in
   [RFC8231], it includes a Flags field.  [RFC8281] defines a R (LSP-
   REMOVE) flag.

   A new flag, the "LSP Control Request Flag" (C), is introduced in the
   SRP object.  On a PCUpd message, a PCE sets the C Flag to 1 to
   indicate that, it wishes to gain control of LSP(s).  The LSP is
   identified by the LSP object.  A PLSP-ID of value other than 0 and
   0xFFFFF is used to identify the LSP for which the PCE requests
   control.  The PLSP-ID value of 0 indicates that the PCE is requesting
   control of all LSPs originating from the PCC that it wishes to
   delegate.  The flag has no meaning in the PCRpt and PCInitiate
   message and MUST be set to 0 on transmission and MUST be ignored on
   receipt.

4.  Operation

   During normal operation, a PCC that wishes to delegate the control of
   an LSP sets the D Flag (delegate) to 1 in all PCRpt messages
   pertaining to the LSP.  The PCE confirms the delegation by setting D
   Flag to 1 in all PCUpd messages pertaining to the LSP.  The PCC
   revokes the control of the LSP from the PCE by setting D Flag to 0 in
   PCRpt messages pertaining to the LSP.  If the PCE wishes to
   relinquish the control of the LSP, it sets D Flag to 0 in all PCUpd
   messages pertaining to the LSP.

   If a PCE wishes to gain control over an LSP, it sends a PCUpd message
   with C Flag set to 1 in SRP object.  The LSP for which the PCE
   requests control is identified by the PLSP-ID.  The PLSP-ID of 0
   indicates that the PCE wants control over all LSPs originating from



Raghuram, et al.        Expires December 20, 2018               [Page 4]


Internet-Draft             LSP Control Request                 June 2018


   the PCC.  If the LSP(s) is/are already delegated to the PCE making
   the request, the PCC ignores the C Flag.  A PCC can decide to
   delegate the control of the LSP at its own discretion.  If the PCC
   grants or denies the control, it sends PCRpt message with D Flag set
   to 1 and 0 respectively in accordance with according with stateful
   PCEP [RFC8231] . If the PCC does not grant the control, it MAY choose
   to not respond, and the PCE may choose to retry requesting the
   control preferably using exponentially increasing timer.  A PCE
   ignores the C Flag on the PCRpt message.  Note that, the PCUpd
   message with C flag set is received for a currently non-delegated LSP
   (for which the PCE is requesting delegation), this MUST NOT trigger
   the error handling as specified in [RFC8231] (a PCErr with Error-
   type=19 (Invalid Operation) and error-value 1 (Attempted LSP Update
   Request for a non-delegated LSP)).

   In case multiple PCEs request control over an LSP, and if the PCC is
   willing to grant the control, the LSP MUST be delegated to only one
   PCE chosen by the PCC based on its local policy.

   It should be noted that a legacy implementation of PCC, that does not
   understand the C flag in PCUpd message, would simply ignore the flag
   (and the request to grant control over the LSP).  At the same time it
   would trigger the error condition as specified in [RFC8231] (a PCErr
   with Error-type=19 (Invalid Operation) and error-value 1 (Attempted
   LSP Update Request for a non-delegated LSP)).

   [RFC8281] describes the setup, maintenance and teardown of PCE-
   initiated LSPs under the stateful PCE model.  It also specify how a
   PCE MAY obtain control over an orphaned LSP that was PCE-initiated.
   A PCE implementation can apply the mechanism described in this
   document in conjunction with those in [RFC8281].

5.  Security Considerations

   The security considerations listed in [RFC8231] apply to this
   document as well.  However, this document also introduces a new
   attack vectors.  An attacker may flood the PCC with request to
   delegate all its LSPs at a rate which exceeds the PCC's ability to
   process them, either by spoofing messages or by compromising the PCE
   itself.  The PCC can simply ignore these messages with no extra
   actions.  Securing the PCEP session using mechanism like Transport
   Layer Security (TLS) [RFC8253] is RECOMMENDED.

6.  IANA Considerations

   This document requests IANA actions to allocate code points for the
   protocol elements defined in this document.




Raghuram, et al.        Expires December 20, 2018               [Page 5]


Internet-Draft             LSP Control Request                 June 2018


6.1.  SRP Object Flags

   The SRP object is defined in [RFC8231] and the registry to manage the
   Flag field of the SRP object is requested in [RFC8281].  IANA is
   requested to make the following allocation in the aforementioned
   registry.

       Bit            Description                      Reference
       TBD            LSP Control Request Flag (c-bit) This document

7.  Manageability Considerations

   All manageability requirements and considerations listed in [RFC5440]
   and [RFC8231] apply to PCEP protocol extensions defined in this
   document.  In addition, requirements and considerations listed in
   this section apply.

7.1.  Control of Function and Policy

   A PCE or PCC implementation SHOULD allow the operator to configure
   the policy based on which it honor the request to control the LSPs.
   Further, the operator MAY be to be allowed to trigger the LSP control
   request at the PCE.

7.2.  Information and Data Models

   The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to
   include mechanism to trigger the LSP control request.

7.3.  Liveness Detection and Monitoring

   Mechanisms defined in this document do not imply any new liveness
   detection and monitoring requirements in addition to those already
   listed in [RFC5440].

7.4.  Verify Correct Operations

   Mechanisms defined in this document do not imply any new operation
   verification requirements in addition to those already listed in
   [RFC5440] and [RFC8231].

7.5.  Requirements On Other Protocols

   Mechanisms defined in this document do not imply any new requirements
   on other protocols.






Raghuram, et al.        Expires December 20, 2018               [Page 6]


Internet-Draft             LSP Control Request                 June 2018


7.6.  Impact On Network Operations

   Mechanisms defined in [RFC5440] and [RFC8231] also apply to PCEP
   extensions defined in this document.  Further, the mechanism
   described in this document can help the operator to request control
   of the LSPs at a particular PCE.

8.  Acknowledgements

   Thanks to Jonathan Hardwick to remind the authors to not use
   suggested values in IANA section.

9.  References

9.1.  Normative References

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

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

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

   [RFC8281]  Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for PCE-Initiated LSP Setup in a Stateful PCE
              Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
              <https://www.rfc-editor.org/info/rfc8281>.

9.2.  Informative References








Raghuram, et al.        Expires December 20, 2018               [Page 7]


Internet-Draft             LSP Control Request                 June 2018


   [I-D.ietf-pce-pcep-yang]
              Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A
              YANG Data Model for Path Computation Element
              Communications Protocol (PCEP)", draft-ietf-pce-pcep-
              yang-07 (work in progress), March 2018.

   [RFC4657]  Ash, J., Ed. and J. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol Generic
              Requirements", RFC 4657, DOI 10.17487/RFC4657, September
              2006, <https://www.rfc-editor.org/info/rfc4657>.

   [RFC8051]  Zhang, X., Ed. and I. Minei, Ed., "Applicability of a
              Stateful Path Computation Element (PCE)", RFC 8051,
              DOI 10.17487/RFC8051, January 2017,
              <https://www.rfc-editor.org/info/rfc8051>.

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

Authors' Addresses

   Aswatnarayan Raghuram
   AT&T
   200 S Laurel Aevenue
   Middletown, NJ  07748
   USA

   Email: ar2521@att.com


   Al Goddard
   AT&T
   200 S Laurel Aevenue
   Middletown, NJ  07748
   USA

   Email: ag6941@att.com











Raghuram, et al.        Expires December 20, 2018               [Page 8]


Internet-Draft             LSP Control Request                 June 2018


   Chaitanya Yadlapalli
   AT&T
   200 S Laurel Aevenue
   Middletown, NJ  07748
   USA

   Email: cy098d@att.com


   Jay Karthik
   Cisco Systems, Inc.
   125 High Street
   Boston, Massachusetts  02110
   USA

   Email: jakarthi@cisco.com


   Siva Sivabalan
   Cisco Systems, Inc.
   2000 Innovation Drive
   Kanata, Ontario  K2K 3E8
   Canada

   Email: msiva@cisco.com


   Jon Parker
   Cisco Systems, Inc.
   2000 Innovation Drive
   Kanata, Ontario  K2K 3E8
   Canada

   Email: jdparker@cisco.com


   Dhruv Dhody
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   Email: dhruv.ietf@gmail.com








Raghuram, et al.        Expires December 20, 2018               [Page 9]


Html markup produced by rfcmarkup 1.127, available from https://tools.ietf.org/tools/rfcmarkup/