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