PCE Working Group                                               D. Dhody
Internet-Draft                                                  U. Palle
Intended status: Standards Track           Huawei Technologies India Pvt
Expires: January 30, 2014                                            Ltd
                                                           July 29, 2013


  PCEP Extensions for MPLS-TE LSP Automatic Bandwidth Adjustment with
                              stateful PCE
             draft-dhody-pce-stateful-pce-auto-bandwidth-02

Abstract

   The Path Computation Element Communication Protocol (PCEP) provides
   mechanisms for Path Computation Elements (PCEs) to perform path
   computations in response to Path Computation Clients (PCCs) requests.
   The extensions described in [STATEFUL-PCE] provide stateful control
   of Multiprotocol Label Switching (MPLS) Traffic Engineering Label
   Switched Paths (TE LSP) via PCEP, for a model where the PCC delegates
   control over one or more locally configured LSPs to the PCE.

   This document describes the automatic bandwidth adjustment of such
   LSPs under the stateful PCE model.

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
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   This Internet-Draft will expire on January 30, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents



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   (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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Architectural Overview . . . . . . . . . . . . . . . . . . . .  4
     4.1.  Auto-Bandwidth Overview  . . . . . . . . . . . . . . . . .  4
     4.2.  Deploying Auto-Bandwidth Feature . . . . . . . . . . . . .  6
   5.  Extensions to the PCEP . . . . . . . . . . . . . . . . . . . .  6
     5.1.  AUTO-BANDWIDTH-ATTRIBUTE TLV . . . . . . . . . . . . . . .  6
     5.2.  BANDWIDTH Object . . . . . . . . . . . . . . . . . . . . .  8
     5.3.  The PCRpt Message  . . . . . . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   7.  Manageability Considerations . . . . . . . . . . . . . . . . .  8
     7.1.  Control of Function and Policy . . . . . . . . . . . . . .  8
     7.2.  Information and Data Models  . . . . . . . . . . . . . . .  8
     7.3.  Liveness Detection and Monitoring  . . . . . . . . . . . .  9
     7.4.  Verify Correct Operations  . . . . . . . . . . . . . . . .  9
     7.5.  Requirements On Other Protocols  . . . . . . . . . . . . .  9
     7.6.  Impact On Network Operations . . . . . . . . . . . . . . .  9
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
     8.1.  PCEP TLV Type Indicators . . . . . . . . . . . . . . . . .  9
     8.2.  BANDWIDTH Object . . . . . . . . . . . . . . . . . . . . .  9
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  9
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 10
     10.2. Informative References . . . . . . . . . . . . . . . . . . 10
   Appendix A.  Contributor Addresses . . . . . . . . . . . . . . . . 10














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1.  Introduction

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

   [STATEFUL-PCE] specifies extensions to PCEP to enable stateful
   control of MPLS TE LSPs.  In this document focus is on Active
   Stateful PCE where LSPs are configured on the PCC and control over
   them is delegated to the PCE.

   Over time, based on the varying traffic pattern, an LSP established
   with certain bandwidth may require to adjust the reserved bandwidth
   over time automatically.  Ingress Label Switch Router (LSR) samples
   the traffic rate at each sample-interval to determine the traffic
   information as Maximum Average Bandwidth (MaxAvgBw).  Further
   adjustment to the reserved bandwidth should be made at every
   adjustment-interval automatically.

   Enabling Auto-Bandwidth on a LSP results in the LSP automatically
   adjusting its bandwidth based on the actual traffic flowing through
   the LSP.  A LSP can therefore be setup with some arbitrary (or zero)
   bandwidth value such that the LSP automatically monitors the traffic
   flow and adjusts its bandwidth every adjustment-interval period.  The
   bandwidth adjustment uses the make-before-break signaling method so
   that there is no interruption to traffic flow.  This is described in
   detail in Section 4.1.

   [STATEFUL-PCE-APP] describes the usecase for auto-bandwidth
   adjustment for passive and active stateful PCE.  Active stateful PCE
   can use information such as historical trending data, application-
   specific information about expected demands or policy information, as
   well as knowledge of the actual desired flow volumes to make smarter
   bandwidth adjustment to delegated LSPs.

   This document defines extensions needed to support Auto-Bandwidth
   feature along with mechanism to provide traffic information of the
   LSPs in a stateful PCE model using PCEP.  At the same time this
   document does not exclude use of any other mechanism employed by
   stateful PCE to learn real time traffic information etc.

1.1.  Requirements Language

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



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2.  Terminology

   The following terminology is used in this document.

   Active Stateful PCE:  PCE that uses tunnel state information learned
      from PCCs to optimize path computations.  Additionally, it
      actively updates tunnel parameters in those PCCs that delegated
      control over their tunnels to the PCE.

   Delegation:  :An operation to grant a PCE temporary rights to modify
      a subset of tunnel parameters on one or more PCC's tunnels.
      Tunnels are delegated from a PCC to a PCE.

   PCC:  Path Computation Client: any client application requesting a
      path computation to be performed by a Path Computation Element.

   PCE:  Path Computation Element.  An entity (component, application,
      or network node) that is capable of computing a network path or
      route based on a network graph and applying computational
      constraints.

   TE LSP:  Traffic Engineering Label Switched Path.

   Note the additional terms defined in Section 4.1.

3.  Motivation

   An active stateful PCE can simply update the bandwidth for a
   delegated LSP via mechanisms described in [STATEFUL-PCE].  Note that
   further extension are needed to support -

   o  identify the LSP that would like to use this feature.

   o  specify the knobs to control parameters like bandwidth range etc.

   o  report the live traffic information.

   Extensions as specified in this document is one of the way for PCE to
   learn this information.  A stateful PCE MAY learn this information
   from other means like management tools.

4.  Architectural Overview

4.1.  Auto-Bandwidth Overview

   Auto-Bandwidth feature allows an LSP to automatically and dynamically
   adjust its reserved bandwidth over time, i.e. without network
   operator intervention.  The bandwidth adjustment uses the make-



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   before-break adaptive signaling method so that there is no
   interruption to traffic flow.

   The new bandwidth reservation is determined by sampling the actual
   traffic flowing through the LSP.  If the traffic flowing through the
   LSP is lower than the configured or current bandwidth of the LSP, the
   extra bandwidth is being reserved needlessly and being wasted.
   Conversely, if the actual traffic flowing through the LSP is higher
   than the configured or current bandwidth of the LSP, it can
   potentially cause congestion or packet loss.  With Auto-Bandwidth
   feature, the LSP bandwidth can be set to some arbitrary value (even
   zero) during initial setup time, and it will be periodically adjusted
   over time based on the actual bandwidth requirement.

   Note the following terms:

   Maximum Average Bandwidth (MaxAvgBw):  The maximum average bandwidth
      is the unit to measure the current traffic demand between a time
      interval.  This is the maximum value of the averaged traffic
      pattern in a particular time interval.

   Sample-Interval:  The time interval in which the traffic rate
      (MaxAvgBw) is collected as a sample.

   Adjustment-Interval:  The time interval in which the bandwidth
      adjustment should be made based on the MaxAvgBw.

   Minimum Bandwidth:  The minimum bandwidth that should be reserved for
      the LSP.

   Maximum Bandwidth:  The maximum bandwidth that can be reserved for
      the LSP.

   Report-Threshold:  This value indicates when the MaxAvgBw must be
      reported to stateful PCE via PCRpt message.  Only if the
      percentage difference between the current MaxAvgBw and the last
      MaxAvgBw is greater than or equal to the threshold percentage the
      LSP bandwidth is reported to PCE.

   Adjust-Threshold:  This value indicates when the bandwidth must be
      adjusted.  Only if the percentage difference between the current
      MaxAvgBw and the current bandwidth allocation is greater than or
      equal to the threshold percentage the LSP bandwidth is adjusted to
      the current bandwidth demand.







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4.2.  Deploying Auto-Bandwidth Feature

   The traffic rate is repeatedly sampled at each sample-interval (which
   can be configured by the user and the default value as 5 minutes).
   The sampled traffic rates are accumulated over the adjustment-
   interval period(which can be configured by the user and the default
   value as 24 hours).

   The ingress LSR reports the traffic information to the stateful PCE
   via the PCRpt message, to avoid multiple reports, the Report-
   Threshold percentage is used.  Only if the percentage difference
   between the current MaxAvgBw and the last MaxAvgBw is greater than or
   equal to the threshold percentage the LSP bandwidth is reported to
   PCE.

   Stateful PCE will adjust the bandwidth of the LSP to the highest
   sampled traffic rate amongst the set of samples taken over the
   adjustment-interval.  Note that the highest sampled traffic rate
   could be higher or lower than the current LSP bandwidth.  Only if the
   current MaxAvgBw and the current bandwidth allocation is greater than
   or equal to the Adjust-Threshold percentage the LSP bandwidth is
   adjusted to the current bandwidth demand.

   Also to avoid multiple LSP re-signaling, sometimes operator set up
   longer adjustment intervals.  However long adjustment-interval can
   also result in an undesirable effect of masking sudden changes in
   traffic patterns.  To avoid this, the stateful PCE MAY pre-maturely
   expire the adjustment-interval to accommodate sudden bursts in
   traffic.

5.  Extensions to the PCEP

5.1.  AUTO-BANDWIDTH-ATTRIBUTE TLV

   The AUTO-BANDWIDTH-ATTRIBUTE TLV can be included as an optional TLV
   in the LSP object as described in [STATEFUL-PCE].  Whenever the LSP
   with Auto-Bandwidth feature enabled is delegated, AUTO-BANDWIDTH-
   ATTRIBUTE TLV MUST be carried in PCRpt message.

   The format of the AUTO-BANDWIDTH-ATTRIBUTE TLV is shown in the
   following figure:










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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=12           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     Minimum Bandwidth                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     Maximum Bandwidth                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Threshold     |           Reserved                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                    AUTO-BANDWIDTH-ATTRIBUTE TLV format

   The type of the TLV is [TBD] and it has a fixed length of 12 octets.

   The value contains the following fields:

   Minimum Bandwidth (32 bits):  The minimum bandwidth allowed is
      encoded in IEEE floating point format (see [IEEE.754.1985]),
      expressed in bytes per second.  Refer to Section 3.1.2 of
      [RFC3471] for a table of commonly used values.

   Maximum Bandwidth (32 bits):  The maximum bandwidth allowed is
      encoded in IEEE floating point format (see [IEEE.754.1985]),
      expressed in bytes per second.  Refer to Section 3.1.2 of
      [RFC3471] for a table of commonly used values.

   Threshold (8 bits):  The Adjust-Threshold value is encoded in
      percentage.  Only if the percentage difference between the current
      MaxAvgBw and the current bandwidth allocation is greater than or
      equal to the threshold percentage the LSP bandwidth is adjusted to
      the current bandwidth demand.

   Reserved (24 bits):  These bits MUST be set to zero on transmission
      and MUST be ignored on receipt.

   If the above parameters are not specified by the user, based on the
   local policy at Ingress (PCC) the default value can be encoded.

   If no default value is specified at Ingress, value 'zero' can be
   encoded for the particular field.  The stateful PCE can then apply
   its own default value based on the local policy.







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5.2.  BANDWIDTH Object

   As per [RFC5440], the BANDWIDTH object is defined with two Object-
   Type values:

   o  Requested Bandwidth: BANDWIDTH Object-Type is 1.

   o  Re-optimization Bandwidth: Bandwidth of an existing TE LSP for
      which a reoptimization is requested.  BANDWIDTH Object-Type is 2.

   The new BANDWIDTH object type 3 [TBD] is used to specify the MaxAvgBw
   determined from the existing TE LSP Traffic flow at every sample-
   interval.  The Report-Threshold percentage is used to determine if
   there is a need to report the current MaxAvgBw.

5.3.  The PCRpt Message

   When the delegated LSP is enabled with the Auto-Bandwidth adjustment
   feature, a PCC MAY include the BANDWIDTH object of type 3 [TBD] in
   the PCRpt message.  The definition of the PCRpt message (see
   [STATEFUL-PCE]) is unchanged.

   When LSP is delegated to a PCE for the very first time, BANDWIDTH
   object of type 1 is used to specify the requested bandwidth in the
   PCRpt message.  To report the traffic flow information (as the
   MaxAvgBw) the BANDWIDTH object of type 3 [TBD] is encoded in further
   PCRpt meessage.

6.  Security Considerations

   TBD.

7.  Manageability Considerations

7.1.  Control of Function and Policy

   The Auto-Bandwidth feature MUST BE controlled per tunnel at Ingress
   (PCC), the values for parameters like sample-interval, adjustment-
   interval, minimum-bandwidth, maximum-bandwidth, report-threshold,
   adjust-threshold SHOULD BE configurable by user.

   TBD.

7.2.  Information and Data Models

   TBD.





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7.3.  Liveness Detection and Monitoring

   TBD.

7.4.  Verify Correct Operations

   TBD.

7.5.  Requirements On Other Protocols

   TBD.

7.6.  Impact On Network Operations

   TBD.

8.  IANA Considerations

8.1.  PCEP TLV Type Indicators

   This document defines the following new PCEP TLVs; IANA is requested
   to make the following allocations from this registry.


          Value     Meaning                     Reference
          TBD       AUTO-BANDWIDTH-ATTRIBUTE    [This I.D.]

8.2.  BANDWIDTH Object

   This document defines new object type for the BANDWIDTH object; IANA
   is requested to make the following allocations from this registry.


     Object-Class Value   Name                               Reference
          5             BANDWIDTH                            [This I.D.]
                         Object-Type
                           3: MaxAvgBw determined from
                           the existing TE LSP Traffic
                           flow.

9.  Acknowledgments

   We would like to thank Venugopal Reddy, Reeja Paul, Sandeep Boina and
   Avantika for their useful comments and suggestions.

10.  References





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10.1.  Normative References

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

10.2.  Informative References

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

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

   [IEEE.754.1985]     IEEE, "Standard for Binary Floating-Point
                       Arithmetic".

   [STATEFUL-PCE]      Crabbe, E., Medved, J., Minei, I., and R. Varga,,
                       "PCEP Extensions for Stateful PCE
                       (draft-ietf-pce-stateful-pce)", June 2013.

   [STATEFUL-PCE-APP]  Zhang, X. and I. Minei, "Applicability of
                       Stateful Path Computation Element (PCE)
                       (draft-zhang-pce-stateful-pce-app)", May 2013.

Appendix A.  Contributor Addresses























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   He Zekun
   Tencent Holdings Ltd,
   Shenzhen P.R.China

   Email: kinghe@tencent.com

   Xian Zhang
   Huawei Technologies
   Research Area F3-1B,
   Huawei Industrial Base,
   Shenzhen, 518129, China

   Phone: +86-755-28972645
   Email: zhang.xian@huawei.com

   Young Lee
   Huawei Technologies
   1700 Alma Drive, Suite 100
   Plano, TX  75075
   US

   Phone: +1 972 509 5599 x2240
   Fax:   +1 469 229 5397
   EMail: leeyoung@huawei.com

Authors' Addresses

   Dhruv Dhody
   Huawei Technologies India Pvt Ltd
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: dhruv.dhody@huawei.com


   Udayasree Palle
   Huawei Technologies India Pvt Ltd
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: udayasree.palle@huawei.com








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