Keywords: Bandwidth optimization, PCEP Overwhelm, LSP re-optimization
Internet Engineering Task Force (IETF) D. Dhody, Ed.
Request for Comments: 8733 Huawei Technologies
Category: Standards Track R. Gandhi, Ed.
ISSN: 2070-1721 Cisco Systems, Inc.
U. Palle
R. Singh
Individual Contributor
L. Fang
Expedia Group, Inc.
February 2020
Path Computation Element Communication Protocol (PCEP) Extensions for
MPLS-TE Label Switched Path (LSP) Auto-Bandwidth Adjustment with
Stateful PCE
Abstract
The Path Computation Element Communication Protocol (PCEP) provides
mechanisms for Path Computation Elements (PCEs) to perform path
computations in response to Path Computation Client (PCC) requests.
Stateful PCE extensions allow stateful control of MPLS-TE Label
Switched Paths (LSPs) using PCEP.
The auto-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
auto-bandwidth adjustment when employing an active stateful PCE for
both PCE-initiated and PCC-initiated LSPs.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8733.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction
2. Conventions Used in This Document
2.1. Requirements Language
2.2. Abbreviations
2.3. Terminology
3. Requirements for PCEP Extensions
4. Architectural Overview
4.1. Auto-Bandwidth Overview
4.2. Auto-Bandwidth Theory of Operation
4.3. Scaling Considerations
5. PCEP Extensions
5.1. Capability Advertisement
5.1.1. AUTO-BANDWIDTH-CAPABILITY TLV
5.2. AUTO-BANDWIDTH-ATTRIBUTES TLV
5.2.1. Sample-Interval Sub-TLV
5.2.2. Adjustment-Intervals
5.2.2.1. Adjustment-Interval Sub-TLV
5.2.2.2. Down-Adjustment-Interval Sub-TLV
5.2.3. Adjustment-Thresholds
5.2.3.1. Adjustment-Threshold Sub-TLV
5.2.3.2. Adjustment-Threshold-Percentage Sub-TLV
5.2.3.3. Down-Adjustment-Threshold Sub-TLV
5.2.3.4. Down-Adjustment-Threshold-Percentage Sub-TLV
5.2.4. Minimum and Maximum-Bandwidth Values
5.2.4.1. Minimum-Bandwidth Sub-TLV
5.2.4.2. Maximum-Bandwidth Sub-TLV
5.2.5. Overflow and Underflow Conditions
5.2.5.1. Overflow-Threshold Sub-TLV
5.2.5.2. Overflow-Threshold-Percentage Sub-TLV
5.2.5.3. Underflow-Threshold Sub-TLV
5.2.5.4. Underflow-Threshold-Percentage Sub-TLV
5.3. BANDWIDTH Object
5.4. The PCInitiate Message
5.5. The PCUpd Message
5.6. The PCRpt Message
5.7. The PCNtf Message
6. Manageability Considerations
6.1. Control of Function and Policy
6.2. Information and Data Models
6.3. Liveness Detection and Monitoring
6.4. Verifying Correct Operations
6.5. Requirements for Other Protocols
6.6. Impact on Network Operations
7. Security Considerations
8. IANA Considerations
8.1. PCEP TLV Type Indicators
8.2. AUTO-BANDWIDTH-CAPABILITY TLV Flag Field
8.3. AUTO-BANDWIDTH-ATTRIBUTES Sub-TLV
8.4. Error Object
8.5. Notification Object
9. References
9.1. Normative References
9.2. Informative References
Acknowledgments
Contributors
Authors' Addresses
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 a PCE and a PCE, that
enables computation of MPLS-TE Label Switched Paths (LSPs).
[RFC8231] specifies extensions to PCEP to enable stateful control of
MPLS-TE LSPs. It describes two modes of operation: 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 the active stateful PCE,
where the LSPs are controlled by the PCE.
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 Switching
Router (LSR) monitors the actual bandwidth demand of the established
LSP and periodically computes new bandwidth. The head-end LSR
automatically adjusts the bandwidth reservation of the LSP based on
the computed bandwidth. This feature, when available in the head-end
LSR implementation, is commonly 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. With a 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 PCEs.
Another approach would be to send the measured values themselves 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
PCEP: Path Computation Element Communication Protocol
TE: Traffic Engineering
LSP: 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 PCCs 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
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, that 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, that 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-
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 ensure
that the magnitude of deviation of the 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
resignaling 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 | At the time of initiation, the PCE |
| traffic and reports the | requests that the PCC monitor the |
| calculated bandwidth to | traffic and report the calculated |
| be adjusted to the PCE. | bandwidth to be adjusted to the PCE. |
+-------------------------+--------------------------------------+
| Extension is needed for | Extension is needed for the PCE to |
| the PCC to pass on the | pass on the adjustment parameters at |
| adjustment parameters | the time of LSP initiation. |
| at the time of LSP | |
| delegation. | |
+-------------------------+--------------------------------------+
Table 1: Requirements for Auto-Bandwidth PCEP Extensions
----------
| |
| PCE |
| |
----------
| ^
AUTO-BANDWIDTH CAPABILITY | | AUTO-BANDWIDTH CAPABILITY
| |
AUTO-BANDWIDTH ATTRIBUTES | | AUTO-BANDWIDTH ATTRIBUTES
| | (For Delegated LSPs)
| |
| | 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 auto-bandwidth adjustment capability for both PCC-
initiated and PCE-initiated LSPs.
Auto-bandwidth deployment considerations for PCEP extensions are
summarized below:
* 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 real-
time bandwidth usage; for some LSPs, leaving the bandwidth
constant as set by the operator is preferred.
* 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 is 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 LSR monitors the actual traffic
flowing through the LSP and uses that information to adjust the
bandwidth reservation of the LSP in the network.
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. The LSP is adjusted (upsized) to the
current bandwidth demand (MaxAvgBW) 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 Adjustment-Threshold could be an absolute value or a percentage.
The threshold can be configured by an operator, with a default value
of 5 percent. 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 resignaling, an operator may set a longer
Adjustment-Interval value (Up and/or Down). However, a longer
Adjustment-Interval can result in the undesirable effect of masking
sudden changes in the traffic demands of an LSP. To avoid this, the
auto-bandwidth feature may force the Adjustment-Interval to
prematurely expire 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 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 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 resignaling
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 resignaling 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.
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 the PCEP initialization phase, PCEP speakers (PCE or PCC)
advertise their support of the auto-bandwidth adjustment feature. A
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 auto-bandwidth feature is supported as described
in this document.
* 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.
* A PCEP speaker that does not recognize the extensions defined in
this document would simply ignore the TLVs as per [RFC5440].
* If a PCEP speaker 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) and
Error-value 14 (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 auto-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=36 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: AUTO-BANDWIDTH-CAPABILITY TLV Format
The TLV Type is 36, and it has a fixed Length of 4 octets.
The value comprises a single field: Flag (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.
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 a 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 Path Computation State Report
(PCRpt) message in the LSPA object. This TLV is also carried in the
LSPA object with the Path Computation Update Request (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=37 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// sub-TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: AUTO-BANDWIDTH-ATTRIBUTES TLV Format
Type: 37
Length: The Length field defines the length of the value portion in
bytes as per [RFC5440].
Value: This comprises one or more sub-TLVs.
The following sub-TLVs are defined in this document:
+------+-----+--------------------------------------+
| Type | Len | Name |
+======+=====+======================================+
| 1 | 4 | Sample-Interval |
+------+-----+--------------------------------------+
| 2 | 4 | Adjustment-Interval |
+------+-----+--------------------------------------+
| 3 | 4 | Down-Adjustment-Interval |
+------+-----+--------------------------------------+
| 4 | 4 | Adjustment-Threshold |
+------+-----+--------------------------------------+
| 5 | 8 | Adjustment-Threshold-Percentage |
+------+-----+--------------------------------------+
| 6 | 4 | Down-Adjustment-Threshold |
+------+-----+--------------------------------------+
| 7 | 8 | Down-Adjustment-Threshold-Percentage |
+------+-----+--------------------------------------+
| 8 | 4 | Minimum-Bandwidth |
+------+-----+--------------------------------------+
| 9 | 4 | Maximum-Bandwidth |
+------+-----+--------------------------------------+
| 10 | 8 | Overflow-Threshold |
+------+-----+--------------------------------------+
| 11 | 8 | Overflow-Threshold-Percentage |
+------+-----+--------------------------------------+
| 12 | 8 | Underflow-Threshold |
+------+-----+--------------------------------------+
| 13 | 8 | Underflow-Threshold-Percentage |
+------+-----+--------------------------------------+
Table 2: Sub-TLV Types of the AUTO-BANDWIDTH-
ATTRIBUTES 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 the 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 subsections describe the sub-TLVs that are currently
defined as being 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 in
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Sample-Interval Sub-TLV Format
The Type is 1, the Length is 4 octets, and the value comprises the
following:
Sample-Interval: The 4-octet time interval for the 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
taken in a case with 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 the case in which an
invalid value is present, the sub-TLV MUST be ignored and the
previous value will be maintained.
5.2.2. Adjustment-Intervals
The sub-TLVs in this section are encoded to inform the PCEP peer of
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 that a different Adjustment-Interval value be set when
the bandwidth usage trend is moving downwards from the one used 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
in which a bandwidth adjustment should be made in an upward or
downward direction. This sub-TLV specifies the value for Up-
Adjustment-Interval and Down-Adjustment-Interval when they are the
same and when 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Adjustment-Interval Sub-TLV Format
The Type is 2, the Length is 4 octets, and the value comprises the
following:
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 will be maintained.
5.2.2.2. Down-Adjustment-Interval Sub-TLV
The Down-Adjustment-Interval sub-TLV specifies a time interval in
seconds in which a 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Down-Adjustment-Interval Sub-TLV Format
The Type is 3, the Length is 4 octets, and the value comprises the
following:
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 will be 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) trends. 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 trends. 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
thresholds are set, the adjustment will not be made until at least
one Sample-Interval has passed simply because no sample will be made
on which to base a comparison with a threshold.
5.2.3.1. Adjustment-Threshold Sub-TLV
The Adjustment-Threshold sub-TLV is used to decide when the LSP
bandwidth should be adjusted in an upward or downward direction.
This sub-TLV specifies the absolute value for Up-Adjustment-Threshold
and Down-Adjustment-Threshold when they are the same and when 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Adjustment-Threshold Sub-TLV Format
The Type is 4, the Length is 4 octets, and the value comprises the
following:
Adjustment-Threshold: The absolute Adjustment-Threshold bandwidth
difference value, encoded in IEEE floating point format (see
[IEEE.754.1985]) and 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 the case in which an invalid value is present, the sub-TLV MUST be
ignored and the previous value will be 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 an upward or downward
direction. This sub-TLV specifies the percentage value for Up-
Adjustment-Threshold and Down-Adjustment-Threshold when they are the
same and when 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Adjustment-Threshold-Percentage Sub-TLV Format
The Type is 5, the Length is 8 octets, and the value comprises the
following:
Reserved: MUST be set to zero on transmission and MUST be ignored on
receipt.
Percentage: The Adjustment-Threshold value (7 bits), encoded in a
percentage (an integer from 1 to 100). The value 0 is considered
to be invalid. The default value is 5 percent.
Minimum-Threshold: The absolute Minimum-Threshold bandwidth value,
encoded in IEEE floating point format (see [IEEE.754.1985]) and
expressed in bytes per second. The increase or decrease of the
LSP bandwidth MUST be at 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 or
above the Minimum-Threshold, the LSP bandwidth is adjusted to the
current bandwidth demand (MaxAvgBw).
In the case in which an invalid value is present, the sub-TLV MUST be
ignored and the previous value will be 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 less 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 a 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Down-Adjustment-Threshold Sub-TLV Format
The Type is 6, the Length is 4 octets, and the value comprises the
following:
Down-Adjustment-Threshold: The absolute Down-Adjustment-Threshold
bandwidth value, encoded in IEEE floating point format (see
[IEEE.754.1985]) and 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 the 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 the case in which an invalid value is present, the sub-TLV MUST be
ignored and the previous value will be 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 less 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 a 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: Down-Adjustment-Threshold-Percentage Sub-TLV Format
The Type is 7, the Length is 8 octets, and the value comprises the
following:
Reserved: MUST be set to zero on transmission and MUST be ignored on
receipt.
Percentage: The Down-Adjustment-Threshold value (7 bits), encoded in
a percentage (an integer from 1 to 100). The value 0 is
considered to be invalid. The default value equals the
Adjustment-Threshold-Percentage.
Minimum-Threshold: The absolute Minimum-Threshold bandwidth value,
encoded in IEEE floating point format (see [IEEE.754.1985]) and
expressed in bytes per second. The decrease of the LSP bandwidth
MUST be at or above the Minimum-Threshold before the 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 or
above the Minimum-Threshold, the LSP bandwidth is adjusted to the
current bandwidth demand (MaxAvgBw).
In the case in which an invalid value is present, the sub-TLV MUST be
ignored and the previous value will be maintained.
5.2.4. Minimum and Maximum-Bandwidth Values
5.2.4.1. Minimum-Bandwidth Sub-TLV
The Minimum-Bandwidth sub-TLV specifies 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: Minimum-Bandwidth Sub-TLV Format
The Type is 8, the Length is 4 octets, and the value comprises the
following:
Minimum-Bandwidth: The 4-octet bandwidth value encoded in IEEE
floating point format (see [IEEE.754.1985]) and 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 the case in which an invalid value is present, the sub-TLV MUST be
ignored and the previous value will be maintained.
5.2.4.2. Maximum-Bandwidth Sub-TLV
The Maximum-Bandwidth sub-TLV specifies 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
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: Maximum-Bandwidth Sub-TLV Format
The Type is 9, the Length is 4 octets, and the value comprises the
following:
Maximum-Bandwidth: The 4-octet bandwidth value encoded in IEEE
floating point format (see [IEEE.754.1985]) and 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 the case in which an invalid value is present, the sub-TLV MUST be
ignored and the previous value will be maintained.
5.2.5. Overflow and Underflow Conditions
The sub-TLVs in this section are encoded to inform the PCEP peer of
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 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13: Overflow-Threshold Sub-TLV Format
The Type is 10, the Length is 8 octets, and the value comprises the
following:
Reserved: MUST be set to zero on transmission and MUST be ignored on
receipt.
Count: The Overflow-Count value (5 bits), encoded in an 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 is to be immediately adjusted to the current
bandwidth demand, bypassing the (up) Adjustment-Interval.
Overflow-Threshold: The absolute Overflow-Threshold bandwidth value,
encoded in IEEE floating point format (see [IEEE.754.1985]) and
expressed in bytes per second. Refer to Section 3.1.2 of
[RFC3471] for a table of commonly used values. If the difference
between the current MaxAvgBw and the current bandwidth reservation
is greater than or equal to the threshold value, the overflow
condition is met.
In the case in which an invalid value is present, the sub-TLV MUST be
ignored and the previous value will be 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: Overflow-Threshold-Percentage Sub-TLV Format
The Type is 11, the Length is 8 octets, and the value comprises the
following:
Percentage: The Overflow-Threshold value (7 bits), encoded in a
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.
Reserved: MUST be set to zero on transmission and MUST be ignored on
receipt.
Count: The Overflow-Count value (5 bits), encoded in an 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 is to be immediately adjusted to the current
bandwidth demand, bypassing the (up) Adjustment-Interval.
Minimum-Threshold: The absolute Minimum-Threshold bandwidth value,
encoded in IEEE floating point format (see [IEEE.754.1985]) and
expressed in bytes per second. The increase of the LSP bandwidth
MUST be at or above the Minimum-Threshold before the bandwidth
adjustment is made.
In the case in which an invalid value is present, the sub-TLV MUST be
ignored and the previous value will be 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: Underflow-Threshold Sub-TLV Format
The Type is 12, the Length is 8 octets, and the value comprises the
following:
Reserved: MUST be set to zero on transmission and MUST be ignored on
receipt.
Count: The Underflow-Count value (5 bits), encoded in an 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 is to be immediately adjusted to the current
bandwidth demand, bypassing the Down-Adjustment-Interval.
Underflow-Threshold: The absolute Underflow-Threshold bandwidth
value, encoded in IEEE floating point format (see [IEEE.754.1985])
and expressed in bytes per second. Refer to Section 3.1.2 of
[RFC3471] for a table of commonly used values. If the difference
between the current MaxAvgBw and the current bandwidth reservation
is greater than or equal to the threshold value, the underflow
condition is met.
In the case in which an invalid value is present, the sub-TLV MUST be
ignored and the previous value will be 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: Underflow-Threshold-Percentage Sub-TLV Format
The Type is 13, the Length is 8 octets, and the value comprises the
following:
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.
Reserved: MUST be set to zero on transmission and MUST be ignored on
receipt.
Count: The Underflow-Count value (5 bits), encoded in an 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 is to be immediately adjusted to the current
bandwidth demand, bypassing the Down-Adjustment-Interval.
Minimum-Threshold: The absolute Minimum-Threshold bandwidth value,
encoded in IEEE floating point format (see [IEEE.754.1985]) and
expressed in bytes per second. The decrease of the LSP bandwidth
MUST be at or above the Minimum-Threshold before the bandwidth
adjustment is made.
In the case in which an invalid value is present, the sub-TLV MUST be
ignored and the previous value will be maintained.
5.3. BANDWIDTH Object
As per [RFC5440], the BANDWIDTH object (Object-Class value 5) is
defined with two Object-Type values as follows:
Requested Bandwidth: The BANDWIDTH Object-Type value is 1.
Reoptimization Bandwidth: The bandwidth of an existing TE LSP for
which a reoptimization is requested. The 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 the
BANDWIDTH Object-Type as 1. The reporting of the 'reoptimization
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 the auto-bandwidth feature enabled,
AUTO-BANDWIDTH-ATTRIBUTES TLV MUST be included in the LSPA object
with the PCInitiate message.
The Routing Backus-Naur Form (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 the auto-bandwidth feature enabled, the
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
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 the local values for the
unspecified parameters. After the successful instantiation of the
LSP, the 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 an 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 cannot be
handled in a timely fashion.
Upon receipt of an 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 while in an overwhelmed state, it MUST be ignored.
* When a PCEP speaker is overwhelmed, it SHOULD notify its peer by
sending a PCNtf message with Notification-type = 5 (Auto-Bandwidth
Overwhelm State) and Notification-value = 1 (Entering Auto-
Bandwidth Overwhelm State). Optionally, an OVERLOADED-DURATION
TLV [RFC5440] MAY be included to specify the time period during
which no further PCEP messages related to auto-bandwidth
adjustment should be sent.
* 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
= 5 (Auto-Bandwidth Overwhelm State) and Notification-value = 2
(Clearing Auto-Bandwidth Overwhelm State). A PCEP speaker SHOULD
send such notification to all peers if a Notification message
(Notification-type = 5, Notification-value = 1) was sent earlier.
This message is not sent if 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 the auto-bandwidth feature is deployed, a PCE can send this
notification to a PCC when it reports frequent auto-bandwidth
adjustments. If a PCC is overwhelmed with resignaling, it can also
notify the PCE to not adjust the LSP bandwidth while in the 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 LSPs to another PCE could cause further
overloading.
6. Manageability Considerations
6.1. Control of Function and Policy
The auto-bandwidth feature SHOULD be controlled on a per-LSP basis
(at the 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, and Adjustment-Threshold
(up/down), SHOULD be configurable by an operator.
The Maximum-Bandwidth (and Minimum-Bandwidth) should be set to an
acceptable limit to avoid having an 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, it is important to ensure 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 the PCEP is
defined in [RFC7420]. Additionally, the YANG module defined in
[PCE-PCEP-YANG] provides both configuration of PCEP as well as
operational management. These could be enhanced to provide controls
and indicators for support of the auto-bandwidth feature. Support
for various configuration knobs as well as counters of messages sent/
received containing the TLVs defined in this document 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. Verifying 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 the case in which an invalid value is present, the sub-TLV would
get ignored and the previous value will be maintained. In such a
case, the implementation SHOULD log the event.
6.5. Requirements for Other Protocols
The mechanisms defined in this document do not add any new
requirements for 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 the auto-bandwidth feature. For each
LSP enabled with the auto-bandwidth feature, there is an extra load
on the PCC, as it needs to monitor the traffic and report the
calculated bandwidth to be adjusted to the PCE. The PCE further
recomputes paths based on the requested bandwidth and updates the
path to the PCC, which, in turn, triggers the resignaling of the
path. All these steps add extra load and churn in the network; thus,
the operator needs to take due care while enabling these 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 notifications to be sent
when a PCEP speaker is overwhelmed or when the rate of messages
reaches a threshold.
Due care is required by the operator if a Sample-Interval value
significantly smaller than the default (5 minutes) is used, as 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 down
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 has made the
following allocations from the "PCEP TLV Type Indicators" subregistry
of the "Path Computation Element Protocol (PCEP) Numbers" registry as
follows:
+-------+---------------------------+-----------+
| Value | Description | Reference |
+=======+===========================+===========+
| 36 | AUTO-BANDWIDTH-CAPABILITY | [RFC8733] |
+-------+---------------------------+-----------+
| 37 | AUTO-BANDWIDTH-ATTRIBUTES | [RFC8733] |
+-------+---------------------------+-----------+
Table 3: PCEP TLV Type Indicators
8.2. AUTO-BANDWIDTH-CAPABILITY TLV Flag Field
IANA has created a subregistry 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:
* Bit number (counting from bit 0 as the most significant bit)
* Capability description
* Defining RFC
The initial contents of the subregistry are empty, with all bits
marked unassigned.
8.3. AUTO-BANDWIDTH-ATTRIBUTES Sub-TLV
This document specifies the AUTO-BANDWIDTH-ATTRIBUTES sub-TLVs. IANA
has created an "AUTO-BANDWIDTH-ATTRIBUTES Sub-TLV Types" subregistry
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 has initialized the registry with the following
values. All other values in the registry should be marked as
"Unassigned".
IANA has set the Registration Procedure for this registry to read as
follows:
+-------------+------------------------+
| Range | Registration Procedure |
+=============+========================+
| 0-65503 | IETF Review |
+-------------+------------------------+
| 65504-65535 | Experimental Use |
+-------------+------------------------+
Table 4: Registration Procedure for
the "AUTO-BANDWIDTH-ATTRIBUTES Sub-
TLV" Registry
This document defines the following types:
+----------+--------------------------------------+-----------+
| Type | Name | Reference |
+==========+======================================+===========+
| 0 | Reserved | [RFC8733] |
+----------+--------------------------------------+-----------+
| 1 | Sample-Interval | [RFC8733] |
+----------+--------------------------------------+-----------+
| 2 | Adjustment-Interval | [RFC8733] |
+----------+--------------------------------------+-----------+
| 3 | Down-Adjustment-Interval | [RFC8733] |
+----------+--------------------------------------+-----------+
| 4 | Adjustment-Threshold | [RFC8733] |
+----------+--------------------------------------+-----------+
| 5 | Adjustment-Threshold-Percentage | [RFC8733] |
+----------+--------------------------------------+-----------+
| 6 | Down-Adjustment-Threshold | [RFC8733] |
+----------+--------------------------------------+-----------+
| 7 | Down-Adjustment-Threshold-Percentage | [RFC8733] |
+----------+--------------------------------------+-----------+
| 8 | Minimum-Bandwidth | [RFC8733] |
+----------+--------------------------------------+-----------+
| 9 | Maximum-Bandwidth | [RFC8733] |
+----------+--------------------------------------+-----------+
| 10 | Overflow-Threshold | [RFC8733] |
+----------+--------------------------------------+-----------+
| 11 | Overflow-Threshold-Percentage | [RFC8733] |
+----------+--------------------------------------+-----------+
| 12 | Underflow-Threshold | [RFC8733] |
+----------+--------------------------------------+-----------+
| 13 | Underflow-Threshold-Percentage | [RFC8733] |
+----------+--------------------------------------+-----------+
| 14-65503 | Unassigned | [RFC8733] |
+----------+--------------------------------------+-----------+
Table 5: Initial Contents of the "AUTO-BANDWIDTH-ATTRIBUTES
Sub-TLV" Registry
8.4. Error Object
This document defines a new Error-value for PCErr message of Error-
Type 19 (Invalid Operation) [RFC8231]. IANA has allocated a new
Error-value within the "PCEP-ERROR Object Error Types and Values"
subregistry of the "Path Computation Element Protocol (PCEP) Numbers"
registry as follows:
+------------+-----------+--------------------+-----------+
| Error-Type | Meaning | Error-value | Reference |
+============+===========+====================+===========+
| 19 | Invalid | 14: Auto-Bandwidth | [RFC8733] |
| | Operation | capability was not | |
| | | advertised | |
+------------+-----------+--------------------+-----------+
Table 6: Addition to the "PCEP-ERROR Object Error Types
and Values" Registry
8.5. Notification Object
IANA has allocated a new Notification-type and Notification-values
within the "Notification Object" subregistry of the "Path Computation
Element Protocol (PCEP) Numbers" registry as follows:
+-------------------+----------------+--------------------+---------+
| Notification-type | Name | Notification-value |Reference|
+===================+================+====================+=========+
| 5 | Auto-Bandwidth | 0: Unassigned |[RFC8733]|
| |Overwhelm State | | |
+-------------------+----------------+--------------------+---------+
| | | 1: Entering Auto- |[RFC8733]|
| | |Bandwidth Overwhelm | |
| | | State | |
+-------------------+----------------+--------------------+---------+
| | | 2: Clearing Auto- |[RFC8733]|
| | |Bandwidth Overwhelm | |
| | | State | |
+-------------------+----------------+--------------------+---------+
Table 7: Additions to the "Notification Object" Registry
9. References
9.1. Normative References
[IEEE.754.1985]
IEEE, "Standard for Binary Floating-Point Arithmetic",
DOI 10.1109/IEEESTD.1985.82928, IEEE Standard 754, October
1985, <https://doi.org/10.1109/IEEESTD.1985.82928>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
[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, <https://www.rfc-editor.org/info/rfc7525>.
[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, "Path
Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", RFC 8231,
DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>.
[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>.
[RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for PCE-Initiated LSP Setup in a Stateful PCE
Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
<https://www.rfc-editor.org/info/rfc8281>.
9.2. Informative References
[PCE-PCEP-YANG]
Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A
YANG Data Model for Path Computation Element
Communications Protocol (PCEP)", Work in Progress,
Internet-Draft, draft-ietf-pce-pcep-yang-13, 31 October
2019,
<https://tools.ietf.org/html/draft-ietf-pce-pcep-yang-13>.
[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., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description",
RFC 3471, DOI 10.17487/RFC3471, January 2003,
<https://www.rfc-editor.org/info/rfc3471>.
[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, DOI 10.17487/RFC7420, December 2014,
<https://www.rfc-editor.org/info/rfc7420>.
[RFC8051] Zhang, X., Ed. and I. Minei, Ed., "Applicability of a
Stateful Path Computation Element (PCE)", RFC 8051,
DOI 10.17487/RFC8051, January 2017,
<https://www.rfc-editor.org/info/rfc8051>.
Acknowledgments
The 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 Kühlewind, Barry Leiba, Benjamin Kaduk, and Roman
Danyliw for the IESG review.
Contributors
He Zekun
Tencent Holdings Ltd.
Shenzhen
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
Samsung
Email: younglee.tx@gmail.com
Authors' Addresses
Dhruv Dhody (editor)
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore 560066
Karnataka
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 Group, Inc.
United States of America
Email: luyuanf@gmail.com