Internet DRAFT - draft-ietf-pce-stateful-pce-auto-bandwidth
draft-ietf-pce-stateful-pce-auto-bandwidth
PCE Working Group D. Dhody, Ed.
Internet-Draft Huawei Technologies
Intended status: Standards Track R. Gandhi, Ed.
Expires: March 29, 2020 Cisco Systems, Inc.
U. Palle
R. Singh
Individual Contributor
L. Fang
Expedia, Inc.
September 26, 2019
PCEP Extensions for MPLS-TE LSP Automatic Bandwidth Adjustment with
Stateful PCE
draft-ietf-pce-stateful-pce-auto-bandwidth-12
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 Stateful PCE extensions allow stateful control of Multi-Protocol
Label Switching (MPLS) Traffic Engineering Label Switched Paths (TE
LSPs) using PCEP.
The automatic bandwidth feature allows automatic and dynamic
adjustment of the TE LSP bandwidth reservation based on the volume of
traffic flowing through the LSP. This document describes PCEP
extensions for automatic bandwidth adjustment when employing an
Active Stateful PCE for both PCE-Initiated and PCC-Initiated LSPs.
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
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Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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Copyright Notice
Copyright (c) 2019 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 4
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
3. Requirements for PCEP Extensions . . . . . . . . . . . . . . . 7
4. Architectural Overview . . . . . . . . . . . . . . . . . . . . 8
4.1. Auto-Bandwidth Overview . . . . . . . . . . . . . . . . . 8
4.2. Auto-bandwidth Theory of Operation . . . . . . . . . . . . 9
4.3. Scaling Considerations . . . . . . . . . . . . . . . . . . 10
5. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . 10
5.1. Capability Advertisement . . . . . . . . . . . . . . . . . 10
5.1.1. AUTO-BANDWIDTH-CAPABILITY TLV . . . . . . . . . . . . 11
5.2. AUTO-BANDWIDTH-ATTRIBUTES TLV . . . . . . . . . . . . . . 12
5.2.1. Sample-Interval sub-TLV . . . . . . . . . . . . . . . 13
5.2.2. Adjustment Intervals . . . . . . . . . . . . . . . . . 14
5.2.2.1. Adjustment-Interval sub-TLV . . . . . . . . . . . 14
5.2.2.2. Down-Adjustment-Interval sub-TLV . . . . . . . . . 14
5.2.3. Adjustment Thresholds . . . . . . . . . . . . . . . . 15
5.2.3.1. Adjustment-Threshold sub-TLV . . . . . . . . . . . 15
5.2.3.2. Adjustment-Threshold-Percentage sub-TLV . . . . . 16
5.2.3.3. Down-Adjustment-Threshold sub-TLV . . . . . . . . 17
5.2.3.4. Down-Adjustment-Threshold-Percentage sub-TLV . . . 18
5.2.4. Minimum and Maximum Bandwidth Values . . . . . . . . . 19
5.2.4.1. Minimum-Bandwidth sub-TLV . . . . . . . . . . . . 19
5.2.4.2. Maximum-Bandwidth sub-TLV . . . . . . . . . . . . 19
5.2.5. Overflow and Underflow Conditions . . . . . . . . . . 20
5.2.5.1. Overflow-Threshold sub-TLV . . . . . . . . . . . . 20
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5.2.5.2. Overflow-Threshold-Percentage sub-TLV . . . . . . 21
5.2.5.3. Underflow-Threshold sub-TLV . . . . . . . . . . . 22
5.2.5.4. Underflow-Threshold-Percentage sub-TLV . . . . . . 23
5.3. BANDWIDTH Object . . . . . . . . . . . . . . . . . . . . . 24
5.4. The PCInitiate Message . . . . . . . . . . . . . . . . . . 24
5.5. The PCUpd Message . . . . . . . . . . . . . . . . . . . . 24
5.6. The PCRpt Message . . . . . . . . . . . . . . . . . . . . 24
5.7. The PCNtf Message . . . . . . . . . . . . . . . . . . . . 25
6. Manageability Considerations . . . . . . . . . . . . . . . . . 26
6.1. Control of Function and Policy . . . . . . . . . . . . . . 26
6.2. Information and Data Models . . . . . . . . . . . . . . . 26
6.3. Liveness Detection and Monitoring . . . . . . . . . . . . 27
6.4. Verify Correct Operations . . . . . . . . . . . . . . . . 27
6.5. Requirements On Other Protocols . . . . . . . . . . . . . 27
6.6. Impact On Network Operations . . . . . . . . . . . . . . . 27
7. Security Considerations . . . . . . . . . . . . . . . . . . . 28
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
8.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . . 28
8.2. AUTO-BANDWIDTH-CAPABILITY TLV Flag Field . . . . . . . . . 28
8.3. AUTO-BANDWIDTH-ATTRIBUTES Sub-TLV . . . . . . . . . . . . 29
8.4. Error Object . . . . . . . . . . . . . . . . . . . . . . . 29
8.5. Notification Object . . . . . . . . . . . . . . . . . . . 30
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31
9.1. Normative References . . . . . . . . . . . . . . . . . . . 31
9.2. Informative References . . . . . . . . . . . . . . . . . . 31
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 33
Contributors' Addresses . . . . . . . . . . . . . . . . . . . . . 33
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 34
1. Introduction
[RFC5440] describes the Path Computation Element Protocol (PCEP) as a
communication mechanism between a Path Computation Client (PCC) and a
Path Computation Element (PCE), or between PCE and PCE, that enables
computation of Multi-Protocol Label Switching (MPLS) Traffic
Engineering Label Switched Paths (TE LSPs).
[RFC8231] specifies extensions to PCEP to enable stateful control of
MPLS TE LSPs. It describes two mode of operations - Passive stateful
PCE and Active stateful PCE. Further, [RFC8281] describes the setup,
maintenance and teardown of PCE-Initiated LSPs for the stateful PCE
model. In this document, the focus is on Active stateful PCE where
the LSPs are controlled by the PCE.
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Over time, based on the varying traffic pattern, an LSP established
with a certain bandwidth may require adjustment of the bandwidth
reserved in the network dynamically. The head-end Label Switch
Router (LSR) monitors the actual bandwidth demand of the established
LSP and periodically computes new bandwidth. The head-end LSR
adjusts the bandwidth reservation of the LSP based on the computed
bandwidth automatically. This feature, when available in the head-
end Label Switching Router (LSR) implementation, is common referred
to as Auto-Bandwidth. The Auto-Bandwidth feature is described in
detail in Section 4 of this document.
In the model considered in this document, the PCC (head-end of the
LSP) collects the traffic rate samples flowing through the LSP and
calculates the new adjusted bandwidth. The PCC reports the
calculated bandwidth to be adjusted to the PCE. This is similar to
the Passive stateful PCE model: while the Passive stateful PCE uses a
path request/reply mechanism, the Active stateful PCE uses a
report/update mechanism. In case of PCE-Initiated LSP, the PCC is
requested during the LSP initiation to monitor and calculate the new
adjusted bandwidth. [RFC8051] describes the use-case for Auto-
Bandwidth adjustment for Passive and Active stateful PCE.
Another approach would be to send the measured values itself to the
PCE, which is considered out of scope for this document.
This document defines the PCEP extensions needed to support an Auto-
Bandwidth feature in an Active stateful PCE model where the LSP
bandwidth to be adjusted is calculated on the PCC (head-end of the
LSP). The use of PCE to calculate the bandwidth to be adjusted is out
of scope of this document.
2. Conventions Used in This Document
2.1. 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.
2.2. Abbreviations
PCC: Path Computation Client.
PCE: Path Computation Element.
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PCEP: Path Computation Element Communication Protocol.
TE LSP: Traffic Engineering Label Switched Path.
2.3. Terminology
The reader is assumed to be familiar with the terminology defined in
[RFC5440], [RFC8231], and [RFC8281].
In this document, the PCC is considered to be the head end LSR of the
LSP. Other types of PCC are not in scope.
The following auto-bandwidth terminology is defined in this document.
Maximum Average Bandwidth (MaxAvgBw): The maximum average bandwidth
represents the current 'measured' traffic bandwidth demand of the
LSP during a time interval. This is the maximum value of the
traffic bandwidth rate samples (Bandwidth-Samples) in a given time
interval.
Adjusted Bandwidth: This is the Auto-Bandwidth 'computed' bandwidth
that is used to adjust the bandwidth reservation of the LSP.
Sample-Interval: The periodic time interval at which the measured
traffic rate of the LSP is collected as a Bandwidth-Sample.
Bandwidth-Sample: The bandwidth sample of the measured traffic rate
of the LSP collected at every Sample-Interval.
Maximum-Bandwidth: The maximum bandwidth that can be reserved for
the LSP.
Minimum-Bandwidth: The minimum bandwidth that can be reserved for
the LSP.
Up-Adjustment-Interval: The periodic time interval at which the
bandwidth adjustment should be made using the MaxAvgBw, when
MaxAvgBw is greater than the current bandwidth reservation of the
LSP.
Down-Adjustment-Interval: The periodic time interval at which the
bandwidth adjustment should be made using the MaxAvgBw, when
MaxAvgBw is less than the current bandwidth reservation of the
LSP.
Up-Adjustment-Threshold: This parameter is used to decide when the
LSP bandwidth should be adjusted. If the percentage or absolute
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difference between the current MaxAvgBw and the current bandwidth
reservation is greater than or equal to the threshold value, the
LSP bandwidth is adjusted (upsized) to the current bandwidth
demand (Adjusted Bandwidth) at the Up-Adjustment-Interval expiry.
Down-Adjustment-Threshold: This parameter is used to decide when the
LSP bandwidth should be adjusted. If the percentage or absolute
difference between the current bandwidth reservation and the
current MaxAvgBw is greater than or equal to the threshold value,
the LSP bandwidth is adjusted (downsized) to the current bandwidth
demand (Adjusted Bandwidth) at the Down-Adjustment-Interval
expiry.
Overflow-Count: This parameter is used to decide when the LSP
bandwidth should be adjusted when there is a sudden increase in
traffic demand. This value indicates how many times,
consecutively, the percentage or absolute difference between the
current MaxAvgBw and the current bandwidth reservation of the LSP
needs to be greater than or equal to the Overflow-Threshold value
in order to meet the overflow condition.
Overflow-Threshold: This parameter is used to decide when the LSP
bandwidth should be adjusted when there is a sudden increase in
traffic demand. If the percentage or absolute difference between
the current MaxAvgBw and the current bandwidth reservation of the
LSP is greater than or equal to the threshold value, the overflow
condition is said to be met. The LSP bandwidth is adjusted to the
current bandwidth demand bypassing the Up-Adjustment-Interval if
the overflow condition is met consecutively for the Overflow-
Count. The Overflow-Threshold needs to be greater than or equal to
the Up-Adjustment-Threshold.
Underflow-Count: This parameter is used to decide when the LSP
bandwidth should be adjusted when there is a sudden decrease in
traffic demand. This value indicates how many times
consecutively, the percentage or absolute difference between the
current MaxAvgBw and the current bandwidth reservation of the LSP
needs to be greater than or equal to the Underflow-Threshold value
in order to meet the underflow condition.
Underflow-Threshold: This parameter is used to decide when the LSP
bandwidth should be adjusted when there is a sudden decrease in
traffic demand. If the percentage or absolute difference between
the current MaxAvgBw and the current bandwidth reservation of the
LSP is greater than or equal to the threshold value, the underflow
condition is said to be met. The LSP bandwidth is adjusted to the
current bandwidth demand bypassing the Down-Adjustment-Interval if
the underflow condition is met consecutively for the Underflow-
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Count. The Underflow-Threshold needs to be greater than or equal
to the Down-Adjustment-Threshold.
Minimum-Threshold: When percentage-based thresholds are in use, they
are accompanied by this minimum threshold, which is used to
enforce that the magnitude of deviation of calculated LSP
bandwidth to be adjusted from the current bandwidth reservations
exceeds a specific non-percentage-based criterion (represented as
an absolute bandwidth value) before any adjustments are made. This
serves to suppress unnecessary auto-bandwidth adjustments and re-
signaling of the LSP at low bandwidth values.
3. Requirements for PCEP Extensions
The PCEP extensions required for auto-bandwidth are summarized in the
following table as well as in Figure 1.
+---------------------------------+---------------------------------+
| PCC Initiated | PCE Initiated |
+---------------------------------+---------------------------------+
| | |
| PCC monitors the traffic | At the time of initiation, |
| and reports the calculated | PCE request PCC to monitor |
| bandwidth to be adjusted | the traffic and report the |
| to the PCE. | calculated bandwidth to be |
| | adjusted to the PCE. |
| | |
| Extension is needed for PCC | Extension is needed for PCE |
| to pass on the adjustment | to pass on the adjustment |
| parameters at the time of | parameters at the time of |
| LSP Delegation. | LSP Initiation. |
| | |
+---------------------------------+---------------------------------+
Table 1: Requirements for Auto-Bandwidth PCEP extensions
----------
| |
| PCE |
| |
----------
| ^
AUTO-BANDWIDTH CAPABILITY | | AUTO-BANDWIDTH CAPABILITY
| |
AUTO-BANDWIDTH ATTRIBUTES | | AUTO-BANDWIDTH ATTRIBUTES
| | (For Delegated LSPs)
| |
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| | REQUESTED BANDWIDTH
v |
----------
| |
| PCC |
| |
----------
Figure 1: Overview of Auto-Bandwidth PCEP extensions
A PCEP speaker supporting this document must have a mechanism to
advertise the automatic bandwidth adjustment capability for both PCC-
Initiated and PCE-Initiated LSPs.
Auto-bandwidth deployment considerations for PCEP extensions are
summarized below:
o It is necessary to identify and inform the PCC which LSPs have
enabled the Auto-Bandwidth feature. Not all LSPs in some
deployments would like their bandwidth to be dependent on the
real-time bandwidth usage; for some LSPs leaving the bandwidth
constant as set by the operator is preferred.
o In addition, an operator should be able to specify the auto-
bandwidth adjustment parameters (i.e. configuration knobs) to
control this feature (e.g. minimum/ maximum bandwidth range). The
PCC should be informed about these adjustment parameters.
4. Architectural Overview
4.1. Auto-Bandwidth Overview
The Auto-Bandwidth feature allows automatic and dynamic adjustment of
the reserved bandwidth of an LSP over time (i.e., without network
operator intervention) to accommodate the varying traffic demand of
the LSP. If the traffic flowing through the LSP is lower than the
configured or current reserved 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 reserved bandwidth of the LSP, it can
potentially cause congestion or packet loss in the network. The
initial LSP bandwidth can be set to an arbitrary value (including
zero). In practice, it can be set to an expected value based on
design and planning. The head-end Label Switch Router (LSR) monitors
the actual traffic flowing through the LSP and uses that information
to adjust the bandwidth reservation of the LSP in the network.
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Bandwidth adjustment must not cause disruption to the traffic flow
carried by the LSP. One way to achieve this is to use the
make-before-break signaling method [RFC3209].
4.2. Auto-bandwidth Theory of Operation
This section describes the Auto-Bandwidth feature in a general way.
When the Auto-Bandwidth feature is enabled, the measured traffic rate
is periodically sampled at each Sample-Interval by the PCC, when the
PCC is the head-end node of the LSP. The sample interval can be
configured by an operator, with a default value of 5 minutes. A very
low Sample-Interval could have some undesirable interactions with
transport protocols (see Section 6.6).
The traffic rate samples are accumulated over the Adjustment-Interval
period (in the Up or Down direction). The period can be configured
by an operator, with a default value of 24 hours. The PCC in-charge
of calculating the bandwidth to be adjusted can decide to adjust the
bandwidth of the LSP to the highest traffic rate sample (MaxAvgBw)
amongst the set of bandwidth samples collected over the
Adjustment-Interval period (in the Up or Down direction) depending on
the operator policy.
Note that the highest traffic rate sample could be higher or lower
than the current LSP bandwidth. Only if the difference between the
current bandwidth demand (MaxAvgBw) and the current bandwidth
reservation is greater than or equal to the Adjustment-Threshold the
LSP bandwidth is adjusted (upsized) to the current bandwidth demand
(MaxAvgBw). The Adjustment-Threshold could be an absolute value or a
percentage. The threshold can be configured by an operator, with a
default value of 5 percentage. Similarly, if the difference between
the current bandwidth reservation and the current bandwidth demand
(MaxAvgBw) is greater than or equal to the Down-Adjustment-Threshold
(percentage or absolute value), the LSP bandwidth is adjusted
(downsized) to the current bandwidth demand (MaxAvgBw). Some LSPs
are less eventful while other LSPs may encounter a lot of changes in
the traffic pattern. The thresholds and intervals for bandwidth
adjustment are configured based on the traffic pattern of the LSP.
In order to avoid frequent re-signaling, an operator may set a longer
adjustment-interval value (Up and/or Down). However, a longer
Adjustment-Interval can result in an undesirable effect of masking
sudden changes in traffic demands of an LSP. To avoid this, the
Auto-Bandwidth feature may prematurely expire the adjustment interval
and adjust the LSP bandwidth to accommodate the sudden bursts of
increase in traffic demand as an overflow condition or decrease in
traffic demand as an underflow condition. An operator needs to
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configure appropriate values for the Overflow-Threshold and/or
Underflow-Threshold parameters and they do not have default values
defined in this document.
All thresholds in this document could be represented in both absolute
value and percentage, and could be used together. This is provided
to accommodate the cases where the LSP bandwidth reservation may
become very large or very small over time. For example, an operator
may use the percentage threshold to handle small to large bandwidth
values and absolute values to handle very large bandwidth values.
The auto-bandwidth adjustment is made when either one of the two
thresholds, the absolute or percentage, is crossed.
When using the (adjustment/overflow/underflow) percentage thresholds,
if the LSP bandwidth changes rapidly at very low values, it may
trigger frequent auto-bandwidth adjustments due to the crossing of
the percentage thresholds. This can lead to unnecessary re-signaling
of the LSPs in the network. This is suppressed by setting the
minimum-threshold parameters along with the percentage thresholds.
The auto-bandwidth adjustment is only made if the LSP bandwidth
crosses both the percentage threshold and the minimum-threshold
parameters.
4.3. Scaling Considerations
It should be noted that any bandwidth change requires re-signaling of
an LSP, which can further trigger preemption of lower priority LSPs
in the network. When deployed under scale, this can lead to a
signaling churn in the network. The Auto-bandwidth application
algorithm is thus advised to take this into consideration before
adjusting the LSP bandwidth. Operators are advised to set the values
of various auto-bandwidth adjustment parameters appropriate for the
deployed LSP scale.
If a PCE gets overwhelmed, it can notify the PCC to temporarily
suspend the reporting of the new LSP bandwidth to be adjusted (see
Section 5.7 of this document). Similarly, if a PCC gets overwhelmed
due to signaling churn, it can notify the PCE to temporarily suspend
new LSP setup requests (see Section 5.7 of this document).
5. PCEP Extensions
5.1. Capability Advertisement
During PCEP Initialization Phase, PCEP speakers (PCE or PCC)
advertise their support of Automatic Bandwidth adjustment feature. A
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PCEP speaker includes the AUTO-BANDWIDTH-CAPABILITY TLV, in the OPEN
Object to advertise its support for PCEP Auto-Bandwidth extensions.
The presence of the AUTO-BANDWIDTH-CAPABILITY TLV in the OPEN Object
indicates that the Automatic Bandwidth feature is supported as
described in this document.
o The PCEP protocol extensions for Auto-Bandwidth adjustments MUST
NOT be used if one or both PCEP speakers have not included the
AUTO-BANDWIDTH-CAPABILITY TLV in their respective OPEN message.
o A PCEP speaker that does not recognize the extensions defined in
this document would simply ignore the TLVs as per [RFC5440].
o If a PCEP speaker that supports the extensions defined in this
document but did not advertise this capability, then upon receipt
of AUTO-BANDWIDTH-ATTRIBUTES TLV in the LSP Attributes (LSPA)
object, it SHOULD generate a PCErr with error-type 19 (Invalid
Operation), error-value TBD4 (Auto-Bandwidth capability was not
advertised) and ignore the AUTO-BANDWIDTH-ATTRIBUTES TLV.
5.1.1. AUTO-BANDWIDTH-CAPABILITY TLV
The AUTO-BANDWIDTH-CAPABILITY TLV is an optional TLV for use in the
OPEN Object for Automatic Bandwidth Adjustment via PCEP capability
advertisement. Its format is shown in the following figure:
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=TBD2 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
AUTO-BANDWIDTH-CAPABILITY TLV format
The Type of the TLV is (TBD2) and it has a fixed Length of 4 octets.
The value comprises a single field - Flags (32 bits). No flags are
defined for this TLV in this document.
Unassigned bits are considered reserved. They MUST be set to 0 on
transmission and MUST be ignored on receipt.
Advertisement of the AUTO-BANDWIDTH-CAPABILITY TLV implies support of
auto-bandwidth adjustment, as well as the objects, TLVs and
procedures defined in this document.
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5.2. AUTO-BANDWIDTH-ATTRIBUTES TLV
The AUTO-BANDWIDTH-ATTRIBUTES TLV provides the 'configurable knobs'
of the feature and it can be included as an optional TLV in the LSPA
Object (as described in [RFC5440]).
For PCE-Initiated LSP [RFC8281], this TLV is included in the LSPA
Object with the PCInitiate message. For the PCC-Initiated delegated
LSPs, this TLV is carried in the PCRpt message in LSPA Object. This
TLV is also carried in the LSPA object with the PCUpd message to
direct the PCC (LSP head-end) to make updates to auto-bandwidth
attributes such as Adjustment-Interval.
The TLV is encoded in all PCEP messages for the LSP while the auto-
bandwidth adjustment feature is enabled, the absence of the TLV
indicates the PCEP speaker wishes to disable the feature. This TLV
includes multiple AUTO-BANDWIDTH-ATTRIBUTES sub-TLVs. The
AUTO-BANDWIDTH-ATTRIBUTES sub-TLVs are included if there is a change
since the last information sent in the PCEP message. The default
values for missing sub-TLVs apply for the first PCEP message for the
LSP.
The format of the AUTO-BANDWIDTH-ATTRIBUTES TLV is shown in the
following figure:
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=TBD1 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// sub-TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
AUTO-BANDWIDTH-ATTRIBUTES TLV format
Type: TBD1
Length: The Length field defines the length of the value portion
in octets as per [RFC5440].
Value: This comprises one or more sub-TLVs.
Following sub-TLVs are defined in this document:
Type Len Name
-------------------------------------------------------------------
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1 4 Sample-Interval sub-TLV
2 4 Adjustment-Interval sub-TLV
3 4 Down-Adjustment-Interval sub-TLV
4 4 Adjustment-Threshold sub-TLV
5 8 Adjustment-Threshold-Percentage sub-TLV
6 4 Down-Adjustment-Threshold sub-TLV
7 8 Down-Adjustment-Threshold-Percentage sub-TLV
8 4 Minimum-Bandwidth sub-TLV
9 4 Maximum-Bandwidth sub-TLV
10 8 Overflow-Threshold sub-TLV
11 8 Overflow-Threshold-Percentage sub-TLV
12 8 Underflow-Threshold sub-TLV
13 8 Underflow-Threshold-Percentage sub-TLV
Future specifications can define additional sub-TLVs.
The sub-TLVs are encoded to inform the PCEP peer of the various
sampling and adjustment parameters. In case of a missing sub-TLV, as
per the local policy, either the default value (as specified in this
document) or some other operator configured value is used.
All sub-TLVs are optional and any unrecognized sub-TLV MUST be
ignored. If a sub-TLV of the same type appears more than once, only
the first occurrence is processed and all others MUST be ignored.
The following sub-sections describe the sub-TLVs which are currently
defined to be carried within the AUTO-BANDWIDTH-ATTRIBUTES TLV.
5.2.1. Sample-Interval sub-TLV
The Sample-Interval sub-TLV specifies a time interval in seconds at
which traffic samples are collected at the PCC.
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=1 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sample-Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sample-Interval sub-TLV format
The Type is 1, Length is 4 octets, and the value comprises of -
o Sample-Interval: The 4-octet time interval for bandwidth sample
collection. The valid range is from 1 to 604800 (7 days), in
seconds. The default value is 300 seconds. Due care needs to be
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taken in case of a very low Sample-Interval, as it can have some
undesirable interactions with transport protocols (see Section
6.6). The sample-interval parameter MUST NOT be greater than the
(down) adjustment-interval. In case of an invalid value, the Sub-
TLV MUST be ignored and the previous value is maintained.
5.2.2. Adjustment Intervals
The sub-TLVs in this section are encoded to inform the PCEP peer the
adjustment interval parameters. The Adjustment-Interval sub-TLV
specifies the time interval for both upward (Up-Adjustment-Interval)
and downward (Down-Adjustment-Interval) trends. An implementation MAY
require to set a different adjustment interval values for when the
bandwidth usage trend is downwards from when it is moving upwards. In
that case, the operator could use the Down-Adjustment-Interval sub-
TLV which overrides the Adjustment-Interval value for Down-
Adjustment-Interval.
5.2.2.1. Adjustment-Interval sub-TLV
The Adjustment-Interval sub-TLV specifies a time interval in seconds
at which bandwidth adjustment should be made in upward or downward
direction. This sub-TLV specify the value for Up-Adjustment-Interval
and Down-Adjustment-Interval when they are the same and the Down-
Adjustment-Interval sub-TLV is not included.
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=2 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Adjustment-Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Adjustment-Interval sub-TLV format
The Type is 2, Length is 4 octets, and the value comprises of -
o Adjustment-Interval: The 4-octet time interval for bandwidth
adjustments. The valid range is from 1 to 604800 (7 days), in
seconds. The default value is 86400 seconds (1 day). The
adjustment-interval parameter MUST NOT be less than the
sample-interval, otherwise the Sub-TLV MUST be ignored and the
previous value is maintained.
5.2.2.2. Down-Adjustment-Interval sub-TLV
The Down-Adjustment-Interval sub-TLV specifies a time interval in
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seconds at which bandwidth adjustment should be made when MaxAvgBw is
less than the current bandwidth reservation of the LSP. This
parameter overrides the Adjustment-Interval for the downward trend.
This sub-TLV is used only when there is a need for different
adjustment intervals in the upward and downward directions.
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=3 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Down-Adjustment-Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Down-Adjustment-Interval sub-TLV format
The Type is 3, Length is 4 octets, and the value comprises of -
o Down-Adjustment-Interval: The 4-octet time interval for downward
bandwidth adjustments. The valid range is from 1 to 604800 (7
days), in seconds. The default value equals the adjustment-
interval. The down-adjustment-interval parameter MUST NOT be less
than the sample-interval, otherwise the Sub-TLV MUST be ignored
and the previous value is maintained.
5.2.3. Adjustment Thresholds
The sub-TLVs in this section are encoded to inform the PCEP peer of
the adjustment threshold parameters. An implementation MAY include
both sub-TLVs for the absolute value and the percentage, in which
case the bandwidth is adjusted when either of the adjustment
threshold conditions are met. The Adjustment-Threshold sub-TLV
specifies the threshold for both upward (Up-Adjustment-Threshold) and
downward (Down-Adjustment-Threshold) trend. If the operator would
like to use a different adjustment threshold during the downward
trend, the Down-Adjustment-Threshold sub-TLV is included. Similarly,
the Adjustment-Threshold-Percentage sub-TLV specifies the threshold
percentage for both upward and downward trend. If the operator would
like to use a different adjustment threshold percentage during the
downward trend, the Down-Adjustment-Threshold-Percentage sub-TLV is
included. It is worth noting that regardless of how the threshold
are set, the adjustment will not be made until at least one sample-
interval simply because no sample will be made on which to base a
comparison with a threshold.
5.2.3.1. Adjustment-Threshold sub-TLV
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The Adjustment-Threshold sub-TLV is used to decide when the LSP
bandwidth should be adjusted in upward or downward direction. This
sub-TLV specify the absolute value for Up-Adjustment-Threshold and
Down-Adjustment-Threshold when they are the same and the Down-
Adjustment-Threshold sub-TLV is not included.
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=4 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Adjustment-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Adjustment-Threshold sub-TLV format
The Type is 4, Length is 4 octets, and the value comprises of -
o Adjustment-Threshold: The absolute Adjustment-Threshold bandwidth
difference value, encoded in IEEE floating point format (see
[IEEE.754.1985]), expressed in bytes per second. The default
adjustment-threshold value is not set. Refer to Section 3.1.2 of
[RFC3471] for a table of commonly used values.
If the modulus of difference between the current MaxAvgBw and the
current bandwidth reservation is greater than or equal to the
threshold value, the LSP bandwidth is adjusted to the current
bandwidth demand (MaxAvgBw).
In case of an invalid value, the Sub-TLV MUST be ignored and the
previous value is maintained.
5.2.3.2. Adjustment-Threshold-Percentage sub-TLV
The Adjustment-Threshold-Percentage sub-TLV is used to decide when
the LSP bandwidth should be adjusted in upward or downward direction.
This sub-TLV specify the percentage value for Up-Adjustment-Threshold
and Down-Adjustment-Threshold when they are the same and the Down-
Adjustment-Threshold-Percentage sub-TLV is not included.
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=5 | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Percentage |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum-Threshold |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Adjustment-Threshold-Percentage sub-TLV format
The Type is 5, Length is 8 octets, and the value comprises of -
o Reserved: MUST be set to zero on transmission and MUST be ignored
on receipt.
o Percentage: The Adjustment-Threshold value (7 bits), encoded in
percentage (an integer from 1 to 100). The value 0 is considered
to be invalid. The default value is 5 percent.
o Minimum-Threshold: The absolute Minimum-Threshold bandwidth value,
encoded in IEEE floating point format (see [IEEE.754.1985]),
expressed in bytes per second. The increase or decrease of the
LSP bandwidth MUST be at least or above the minimum-threshold
before the bandwidth adjustment is made. The default value is 0.
If the percentage absolute difference between the current MaxAvgBw
and the current bandwidth reservation is greater than or equal to the
threshold percentage, and the difference in the bandwidth is at least
or above the Minimum-Threshold, the LSP bandwidth is adjusted to the
current bandwidth demand (MaxAvgBw).
In case of an invalid value, the Sub-TLV MUST be ignored and the
previous value is maintained.
5.2.3.3. Down-Adjustment-Threshold sub-TLV
The Down-Adjustment-Threshold sub-TLV is used to decide when the LSP
bandwidth should be adjusted when MaxAvgBw is lesser than the current
bandwidth reservation. This parameter overrides the Adjustment-
Threshold for the downward trend. This sub-TLV is used only when
there is a need for different threshold in the upward and downward
directions.
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=6 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Down-Adjustment-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Down-Adjustment-Threshold sub-TLV format
The Type is 6, Length is 4 octets, and the value comprises of -
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o Down-Adjustment-Threshold: The absolute Down-Adjustment-Threshold
bandwidth value, encoded in IEEE floating point format (see
[IEEE.754.1985]), expressed in bytes per second. The default
value equals the adjustment-threshold. Refer to Section 3.1.2 of
[RFC3471] for a table of commonly used values.
If the difference between current bandwidth reservation and the
current MaxAvgBw is greater than or equal to the threshold value, the
LSP bandwidth is adjusted to the current bandwidth demand (MaxAvgBw).
In case of an invalid value, the Sub-TLV MUST be ignored and the
previous value is maintained.
5.2.3.4. Down-Adjustment-Threshold-Percentage sub-TLV
The Down-Adjustment-Threshold-Percentage sub-TLV is used to decide
when the LSP bandwidth should be adjusted when MaxAvgBw is lesser
than the current bandwidth reservation. This parameter overrides the
Adjustment-Threshold-Percentage for the downward trend. This sub-TLV
is used only when there is a need for different threshold percentage
in the upward and downward directions.
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=7 | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Percentage |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Down-Adjustment-Threshold-Percentage sub-TLV format
The Type is 7, Length is 8 octets, and the value comprises of -
o Reserved: MUST be set to zero on transmission and MUST be ignored
on receipt.
o Percentage: The Down-Adjustment-Threshold value (7 bits), encoded
in percentage (an integer from 1 to 100). The value 0 is
considered to be invalid. The default value equals the
adjustment-threshold-percentage.
o Minimum-Threshold: The absolute Minimum-Threshold bandwidth value,
encoded in IEEE floating point format (see [IEEE.754.1985]),
expressed in bytes per second. The decrease of the LSP bandwidth
MUST be at least or above the minimum-threshold before the
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bandwidth adjustment is made. The default value equals the
minimum-threshold for the adjustment-threshold-percentage.
If the percentage difference between the current bandwidth
reservation and the current MaxAvgBw is greater than or equal to the
threshold percentage, and the difference in the bandwidth is at least
or above the Minimum-Threshold, the LSP bandwidth is adjusted to the
current bandwidth demand (MaxAvgBw).
In case of an invalid value, the Sub-TLV MUST be ignored and the
previous value is maintained.
5.2.4. Minimum and Maximum Bandwidth Values
5.2.4.1. Minimum-Bandwidth sub-TLV
The Minimum-Bandwidth sub-TLV specify the minimum bandwidth allowed
for the LSP, and is expressed in bytes per second. The LSP bandwidth
cannot be adjusted below the minimum bandwidth value.
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=8 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum-Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Minimum-Bandwidth sub-TLV format
The Type is 8, Length is 4 octets, and the value comprises of -
o Minimum-Bandwidth: The 4-octet bandwidth value encoded in IEEE
floating point format (see [IEEE.754.1985]), expressed in bytes
per second. The default minimum-bandwidth value is set to 0.
Refer to Section 3.1.2 of [RFC3471] for a table of commonly used
values.
In case of an invalid value, the Sub-TLV MUST be ignored and the
previous value is maintained.
5.2.4.2. Maximum-Bandwidth sub-TLV
The Maximum-Bandwidth sub-TLV specify the maximum bandwidth allowed
for the LSP, and is expressed in bytes per second. The LSP bandwidth
cannot be adjusted above the maximum bandwidth value.
0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=9 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum-Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Maximum-Bandwidth sub-TLV format
The Type is 9, Length is 4 octets, and the value comprises of -
o Maximum-Bandwidth: The 4-octet bandwidth value encoded in IEEE
floating point format (see [IEEE.754.1985]), expressed in bytes
per second. The default maximum-bandwidth value is not set.
Refer to Section 3.1.2 of [RFC3471] for a table of commonly used
values.
In case of an invalid value, the Sub-TLV MUST be ignored and the
previous value is maintained.
5.2.5. Overflow and Underflow Conditions
The sub-TLVs in this section are encoded to inform the PCEP peer the
overflow and underflow threshold parameters. An implementation MAY
include sub-TLVs for an absolute value and/or a percentage for the
threshold, in which case the bandwidth is immediately adjusted when
either of the threshold conditions is met consecutively for the given
count (as long as the difference in the bandwidth is at least or
above the Minimum-Threshold). By default, the threshold values for
overflow and underflow conditions are not set.
5.2.5.1. Overflow-Threshold sub-TLV
The Overflow-Threshold sub-TLV is used to decide if the LSP bandwidth
should be adjusted immediately.
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=10 | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Overflow-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Overflow-Threshold sub-TLV format
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The Type is 10, Length is 8 octets, and the value comprises of -
o Reserved: MUST be set to zero on transmission and MUST be ignored
on receipt.
o Count: The Overflow-Count value (5 bits), encoded in integer. The
value 0 is considered to be invalid. The number of consecutive
samples for which the overflow condition MUST be met for the LSP
bandwidth to be immediately adjusted to the current bandwidth
demand, bypassing the (up) adjustment-interval.
o Overflow-Threshold: The absolute Overflow-Threshold bandwidth
value, 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. If the
difference of the current MaxAvgBw from the current bandwidth
reservation is greater than or equal to the threshold value, the
overflow condition is met.
In case of an invalid value, the Sub-TLV MUST be ignored and the
previous value is maintained.
5.2.5.2. Overflow-Threshold-Percentage sub-TLV
The Overflow-Threshold-Percentage sub-TLV is used to decide if the
LSP bandwidth should be adjusted immediately.
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=11 | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Percentage | Reserved | Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Overflow-Threshold-Percentage sub-TLV format
The Type is 11, Length is 8 octets, and the value comprises of -
o Percentage: The Overflow-Threshold value (7 bits), encoded in
percentage (an integer from 1 to 100). The value 0 is considered
to be invalid. If the percentage increase of the current MaxAvgBw
from the current bandwidth reservation is greater than or equal to
the threshold percentage, the overflow condition is met.
o Reserved: MUST be set to zero on transmission and MUST be ignored
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on receipt.
o Count: The Overflow-Count value (5 bits), encoded in integer. The
value 0 is considered to be invalid. The number of consecutive
samples for which the overflow condition MUST be met for the LSP
bandwidth to be immediately adjusted to the current bandwidth
demand, bypassing the (up) adjustment-interval.
o Minimum-Threshold: The absolute Minimum-Threshold bandwidth value,
encoded in IEEE floating point format (see [IEEE.754.1985]),
expressed in bytes per second. The increase of the LSP bandwidth
MUST be at least or above the minimum-threshold before the
bandwidth adjustment is made.
In case of an invalid value, the Sub-TLV MUST be ignored and the
previous value is maintained.
5.2.5.3. Underflow-Threshold sub-TLV
The Underflow-Threshold sub-TLV is used to decide if the LSP
bandwidth should be adjusted immediately.
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=12 | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Underflow-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Underflow-Threshold sub-TLV format
The Type is 12, Length is 8 octets, and the value comprises of -
o Reserved: MUST be set to zero on transmission and MUST be ignored
on receipt.
o Count: The Underflow-Count value (5 bits), encoded in integer.
The value 0 is considered to be invalid. The number of
consecutive samples for which the underflow condition MUST be met
for the LSP bandwidth to be immediately adjusted to the current
bandwidth demand, bypassing the down-adjustment-interval.
o Underflow-Threshold: The absolute Underflow-Threshold bandwidth
value, encoded in IEEE floating point format (see
[IEEE.754.1985]), expressed in bytes per second. Refer to Section
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3.1.2 of [RFC3471] for a table of commonly used values. If the
difference of the current MaxAvgBw from the current bandwidth
reservation is greater than or equal to the threshold value, the
underflow condition is met.
In case of an invalid value, the Sub-TLV MUST be ignored and the
previous value is maintained.
5.2.5.4. Underflow-Threshold-Percentage sub-TLV
The Underflow-Threshold-Percentage sub-TLV is used to decide if the
LSP bandwidth should be adjusted immediately.
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=13 | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Percentage | Reserved | Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Underflow-Threshold-Percentage sub-TLV format
The Type is 13, Length is 8 octets, and the value comprises of -
o Percentage: The Underflow-Threshold value (7 bits), encoded in
percentage (an integer from 1 to 100). The value 0 is considered
to be invalid. If the percentage decrease of the current MaxAvgBw
from the current bandwidth reservation is greater than or equal to
the threshold percentage, the underflow condition is met.
o Reserved: MUST be set to zero on transmission and MUST be ignored
on receipt.
o Count: The Underflow-Count value (5 bits), encoded in integer.
The value 0 is considered to be invalid. The number of
consecutive samples for which the underflow condition MUST be met
for the LSP bandwidth to be immediately adjusted to the current
bandwidth demand, bypassing the down-adjustment-interval.
o Minimum-Threshold: The absolute Minimum-Threshold bandwidth value,
encoded in IEEE floating point format (see [IEEE.754.1985]),
expressed in bytes per second. The decrease of the LSP bandwidth
MUST be at least or above the minimum-threshold before the
bandwidth adjustment is made.
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In case of an invalid value, the Sub-TLV MUST be ignored and the
previous value is maintained.
5.3. BANDWIDTH Object
As per [RFC5440], the BANDWIDTH object (Object-Class value 5) is
defined with two Object-Type values as following:
o Requested Bandwidth: BANDWIDTH Object-Type value is 1.
o Re-optimization Bandwidth: Bandwidth of an existing TE LSP for
which a re-optimization is requested. BANDWIDTH Object-Type value
is 2.
The PCC reports the calculated bandwidth to be adjusted (MaxAvgBw) to
the Stateful PCE using the existing 'Requested Bandwidth' with
BANDWIDTH Object-Type as 1. The reporting of the 're-optimization
bandwidth' with BANDWIDTH Object-Type as 2 is not required as the
Stateful PCE is aware of the existing LSP bandwidth.
5.4. The PCInitiate Message
A PCInitiate message is a PCEP message sent by a PCE to a PCC to
trigger LSP instantiation or deletion [RFC8281].
For the PCE-Initiated LSP with Auto-Bandwidth feature enabled, AUTO-
BANDWIDTH-ATTRIBUTES TLV MUST be included in the LSPA object with the
PCInitiate message.
The Routing Backus-Naur Format (RBNF) definition of the PCInitiate
message [RFC8281] is unchanged by this document.
5.5. The PCUpd Message
A PCUpd message is a PCEP message sent by a PCE to a PCC to update
the LSP parameters [RFC8231].
For PCE-Initiated LSPs with Auto-Bandwidth feature enabled, AUTO-
BANDWIDTH-ATTRIBUTES TLV MUST be included in the LSPA object with the
PCUpd message. The PCE can send this TLV to direct the PCC to change
the auto-bandwidth parameters.
The RBNF definition of the PCUpd message [RFC8231] is unchanged by
this document.
5.6. The PCRpt Message
The PCRpt message [RFC8231] is a PCEP message sent by a PCC to a PCE
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to report the status of one or more LSPs.
For PCE-Initiated LSPs [RFC8281], the PCC creates the LSP using the
attributes communicated by the PCE, and using the local values for
the unspecified parameters. After the successful instantiation of
the LSP, PCC automatically delegates the LSP to the PCE and generates
a PCRpt message to provide the status report for the LSP.
For both PCE-Initiated and PCC-Initiated LSPs, when the LSP is
delegated to a PCE for the very first time as well as after the
successful delegation, the BANDWIDTH object of type 1 is used to
specify the requested bandwidth in the PCRpt message.
The RBNF definition of the PCRpt message [RFC8231] is unchanged by
this document.
5.7. The PCNtf Message
As per [RFC5440], the PCEP Notification message (PCNtf) can be sent
by a PCEP speaker to notify its peer of a specific event.
A PCEP speaker (PCE or PCC) SHOULD notify its PCEP peer (PCC or PCE)
when it is in overwhelmed state due to the auto-bandwidth feature.
An implementation needs to make an attempt to send this notification
(when overwhelmed by auto-bandwidth adjustments) unless sending this
notification would only serve to increase the load further. Note that
when the notification is not received the PCEP speaker would continue
to request bandwidth adjustments even when they could not be handled
in a timely fashion.
Upon receipt of auto-bandwidth overwhelm notification, the peer
SHOULD NOT send any PCEP messages related to auto-bandwidth
adjustment. If a PCEP message related to auto-bandwidth adjustment
is received during in overwhelmed state, it MUST be ignored.
o When a PCEP speaker is overwhelmed, it SHOULD notify its peer by
sending a PCNtf message with Notification-Type = TBD3 (Auto-
bandwidth Overwhelm State) and Notification-Value = 1 (Entering
auto-bandwidth overwhelm state). Optionally, OVERLOADED-DURATION
TLV [RFC5440] MAY be included that specifies the time period
during which no further PCEP messages related to auto-bandwidth
adjustment should be sent.
o When the PCEP speaker is no longer in the overwhelm state and is
available to process the auto-bandwidth adjustments, it SHOULD
notify its peers by sending a PCNtf message with Notification Type
= TBD3 (Auto-bandwidth Overwhelm State) and Notification Value = 2
(Clearing auto-bandwidth overwhelm state). A PCEP speaker SHOULD
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send such notification to all peers to with a Notification message
(Notification-Type=TBD3, Notification-Value=1) was sent earlier
unless an OVERLOADED-DURATION TLV was included and the PCEP
speakers wishes for the peer to wait for the expiration of that
period of time before receiving further PCEP messages related to
auto-bandwidth adjustment.
When Auto-Bandwidth feature is deployed, a PCE can send this
notification to PCC when a PCC is reporting frequent auto-bandwidth
adjustments. If a PCC is overwhelmed with re-signaling, it can also
notify the PCE to not adjust the LSP bandwidth while in overwhelm
state.
Some dampening notification procedure (as per [RFC5440]) to avoid
oscillations of the overwhelm state is RECOMMENDED. On receipt of an
auto-bandwidth overwhelm notification from the PCE, a PCC should
consider the impact on the entire network. Moving the delegations of
auto-bandwidth enabled LSP to another PCE could cause further
overloading.
6. Manageability Considerations
6.1. Control of Function and Policy
The Auto-Bandwidth feature SHOULD be controlled per LSP (at PCC
(head-end of the LSP) or PCE) and the values for auto-bandwidth
parameters e.g. sample-interval, adjustment-interval (up/down),
minimum-bandwidth, maximum-bandwidth, adjustment-threshold (up/down)
SHOULD be configurable by an operator.
The Maximum-Bandwidth (and Minimum-Bandwidth) should be set to
acceptable limit to avoid impact on the rest of the MPLS-TE domain.
The operator should make sure that the Overflow-Threshold is greater
than or at least equal to the Up-Adjustment-Threshold. And similarly,
make sure that the Underflow-Threshold is greater than or at least
equal to the Down-Adjustment-Threshold.
6.2. Information and Data Models
A MIB module for gathering operational information about PCEP is
defined in [RFC7420]. Additionally, the YANG module defined in
[I-D.ietf-pce-pcep-yang] provides for both configuration of PCEP as
well as operational management. These could be enhanced to provide
controls and indicators for support of auto-bandwidth feature.
Support for various configuration knobs as well as counters of
messages sent/received containing the TLVs defined in this document
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could be added.
6.3. Liveness Detection and Monitoring
The mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in [RFC5440].
6.4. Verify Correct Operations
The mechanisms defined in this document do not imply any new
operation verification requirements in addition to those already
listed in [RFC5440].
In case of an invalid value, the Sub-TLV would get ignored and the
previous value would be maintained. In such case the implementation
SHOULD log the event.
6.5. Requirements On Other Protocols
The mechanisms defined in this document do not add any new
requirements on other protocols.
6.6. Impact On Network Operations
In order to avoid any unacceptable impact on network operations, an
implementation SHOULD allow a limit to be placed on the number of
LSPs that can be enabled with auto-bandwidth feature. For each LSP
enabled with auto-bandwidth feature there is an extra load on PCC, as
it needs to monitor the traffic and report the calculated bandwidth
to be adjusted to the PCE. The PCE further re-compute paths based on
the requested bandwidth and update the path to the PCC, which in
turns triggers the re-signaling of the path. All these steps adds
extra load and churn in the network and thus operator needs to take
due care while enabling this features on a number of LSPs.
An implementation MAY allow a limit to be placed on the rate of auto-
bandwidth related messages sent by a PCEP speaker and received by a
peer. An implementation SHOULD also allow sending a notification
when a PCEP speaker is overwhelmed or the rate of messages reach a
threshold.
Due care is required by the operator if a Sample-Interval value
significantly smaller than the default (5 minute) is used, as a small
Sample-Interval values, e.g., 1 minute or less, could cause
undesirable interactions with transport protocols. These undesirable
interactions result from providing insufficient time for transport
protocol reactions to a prior bandwidth adjustment to settle out
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before bandwidth samples are taken for the next bandwidth adjustment.
7. Security Considerations
This document defines AUTO-BANDWIDTH-CAPABILITY TLV and AUTO-
BANDWIDTH-ATTRIBUTES sub-TLVs which do not add any substantial new
security concerns beyond those already discussed in [RFC8231] and
[RFC8281] for stateful PCE operations. As per [RFC8231], it is
RECOMMENDED that these PCEP extensions only be activated on
authenticated and encrypted sessions across PCEs and PCCs belonging
to the same administrative authority, using Transport Layer Security
(TLS) [RFC8253], as per the recommendations and best current
practices in BCP 195 [RFC7525] (unless explicitly set aside in
[RFC8253]).
Incorrect auto-bandwidth parameters in the AUTO-BANDWIDTH-ATTRIBUTES
sub-TLVs could have an adverse effect on the LSP as well as on the
network.
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 the "PCEP TLV Type Indicators"
sub-registry of the PCEP Numbers registry, as follows:
Value Name Reference
-----------------------------------------------------------------
TBD2 AUTO-BANDWIDTH-CAPABILITY [This document]
TBD1 AUTO-BANDWIDTH-ATTRIBUTES [This document]
8.2. AUTO-BANDWIDTH-CAPABILITY TLV Flag Field
IANA is requested to create a sub-registry to manage the Flag field
of the AUTO-BANDWIDTH-CAPABILITY TLV within the "Path Computation
Element Protocol (PCEP) Numbers" registry.
New bit numbers are to be assigned by Standards Action [RFC8126].
Each bit should be tracked with the following qualities:
o Bit number (counting from bit 0 as the most significant bit)
o Capability description
o Defining RFC
The initial contents of the sub-registry are empty, with all bits
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marked unassigned
8.3. AUTO-BANDWIDTH-ATTRIBUTES Sub-TLV
This document specifies the AUTO-BANDWIDTH-ATTRIBUTES Sub-TLVs. IANA
is requested to create an "AUTO-BANDWIDTH-ATTRIBUTES Sub-TLV Types"
sub-registry within the "Path Computation Element Protocol (PCEP)
Numbers" registry to manage the type indicator space for sub-TLVs of
the AUTO-BANDWIDTH-ATTRIBUTES TLV. The valid range of values in the
registry is 0-65535. IANA is requested to initialize the registry
with the following values. All other values in the registry should
be marked as "Unassigned".
IANA is requested to set the registration procedure for this registry
to read as follows:
0-65503 IETF Review
65504-65535 Experimental Use
This document defines the following types:
Type Name Reference
-----------------------------------------------------------------
0 Reserved [This document]
1 Sample-Interval sub-TLV [This document]
2 Adjustment-Interval sub-TLV [This document]
3 Down-Adjustment-Interval sub-TLV [This document]
4 Adjustment-Threshold sub-TLV [This document]
5 Adjustment-Threshold-Percentage sub-TLV [This document]
6 Down-Adjustment-Threshold sub-TLV [This document]
7 Down-Adjustment-Threshold-Percentage sub-TLV [This document]
8 Minimum-Bandwidth sub-TLV [This document]
9 Maximum-Bandwidth sub-TLV [This document]
10 Overflow-Threshold sub-TLV [This document]
11 Overflow-Threshold-Percentage sub-TLV [This document]
12 Underflow-Threshold sub-TLV [This document]
13 Underflow-Threshold-Percentage sub-TLV [This document]
14- Unassigned [This document]
65503
8.4. Error Object
This document defines a new Error-Value for PCErr message of Error-
Type 19 (Invalid Operation) [RFC8231]. IANA is requested to allocate
new error-value within the "PCEP-ERROR Object Error Types and Values"
subregistry of the PCEP Numbers registry, as follows:
Error-Type Meaning & error values Reference
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-----------------------------------------------------------------
19 Invalid Operations
Error-Value = TBD4: [This document]
Auto-Bandwidth Capability
was not Advertised
8.5. Notification Object
IANA is requested to allocate new Notification Type and Notification
Values within the "Notification Object" sub-registry of the PCEP
Numbers registry, as follows:
Type Meaning Reference
-----------------------------------------------------------------
TBD3 Auto-Bandwidth Overwhelm State [This document]
Notification-value=1: Entering Auto-Bandwidth
overwhelm state
Notification-value=2: Clearing Auto-Bandwidth
overwhelm state
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9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440, March
2009.
[RFC7525] Sheffer, Y., Holz, R. and P. Saint-Andre, "Recommendations
for Secure Use of Transport Layer Security (TLS) and
Datagram Transport Layer Security (DTLS)", BCP 195, RFC
7525, DOI 10.17487/RFC7525, May 2015.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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, "Pah
Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", RFC 8231, DOI
10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/infor/rfc8231>.
[RFC8253] Lopez, D., Dios, O., Wu, W., and D. Dhody, "PCEPS: Usage
of TLS to Provide a Secure Transport for the Path
Computation Element Communication Protocol (PCEP)", RFC
8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>.
[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>.
[IEEE.754.1985] Institute of Electrical and Electronics Engineers,
"Standard for Binary Floating-Point Arithmetic", IEEE
Standard 754, August 1985.
9.2. Informative References
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[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Functional Description", RFC 3471,
January 2003.
[RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
Hardwick, "Path Computation Element Communication Protocol
(PCEP) Management Information Base (MIB) Module", RFC
7420, December 2014.
[RFC8051] Zhang, X. and I. Minei, "Applicability of a Stateful Path
Computation Element (PCE)", RFC 8051, January 2017.
[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
(work in progress).
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Acknowledgments
Authors would like to thank Robert Varga, Venugopal Reddy, Reeja
Paul, Sandeep Boina, Avantika, JP Vasseur, Himanshu Shah, Jonathan
Hardwick and Adrian Farrel for their useful comments and suggestions.
Thanks to Daniel Franke, Joe Clarke, David Black, and Erik Kline for
the directorate reviews.
Thanks to Mirja Kuhlewind, Barry Leiba, Benjamin Kaduk, and Roman
Danyliw for the IESG review.
Contributors' Addresses
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
SKKU
Email: younglee.tx@gmail.com
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Authors' Addresses
Dhruv Dhody (editor)
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: dhruv.ietf@gmail.com
Rakesh Gandhi (editor)
Cisco Systems, Inc.
Canada
Email: rgandhi@cisco.com
Udayasree Palle
Individual Contributor
Email: udayasreereddy@gmail.com
Ravi Singh
Individual Contributor
Email: ravi.singh.ietf@gmail.com
Luyuan Fang
Expedia, Inc.
USA
Email: luyuanf@gmail.com
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