PCEP Extensions for MPLS-TE LSP Automatic Bandwidth Adjustment with Stateful PCE

PCEP Extensions for MPLS-TE LSP Automatic Bandwidth Adjustment with Stateful PCE Huawei Technologies

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PCE Working Group example 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.

Introduction 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). 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, 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. 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. 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.

Conventions Used in This Document

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 when, and only when, they appear in all capitals, as shown here.

Abbreviations

PCC:: Path Computation Client.
PCE:: Path Computation Element.
PCEP:: Path Computation Element Communication Protocol.
TE LSP:: Traffic Engineering Label Switched Path.

Terminology The reader is assumed to be familiar with the terminology defined in , , and . 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 bandwidthrepresents 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, 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-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.

Requirements for PCEP Extensions The PCEP extensions required for auto-bandwidth are summarized in the following table as well as in Figure 1. Requirements for Auto-Bandwidth PCEP extensions

PCC Initiated	PCE Initiated
PCC monitors the traffic and reports the calculated bandwidth to be adjusted to the PCE. Extension is needed for PCC to pass on the adjustment parameters at the time of LSP Delegation.	At the time of initiation, PCE request PCC to monitor the traffic and report the calculated bandwidth to be adjusted to the PCE. Extension is needed for PCE to pass on the adjustment parameters at the time of LSP Initiation.

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:

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.
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.

Architectural Overview

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. 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 .

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 ). 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 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.

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).

PCEP Extensions

Capability Advertisement During PCEP Initialization Phase, PCEP speakers (PCE or PCC) advertise their support of Automatic 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 Automatic 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 .
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.

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: 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.

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 ). For PCE-Initiated LSP , 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:

Type:: TBD1
Length:: The Length field defines the length of the value portion in octets as per .
Value:: This comprises one or more sub-TLVs.

Following sub-TLVs are defined in this document: 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.

Sample-Interval sub-TLV The Sample-Interval sub-TLV specifies a time interval in seconds at which traffic samples are collected at the PCC. The Type is 1, Length is 4 octets, and the value comprises of -

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 taken in case of a very low Sample-Interval, as it can have some undesirable interactions with transport protocols (see ). 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.

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.

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. The Type is 2, Length is 4 octets, and the value comprises of -

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.

Down-Adjustment-Interval sub-TLV The Down-Adjustment-Interval sub-TLV specifies a time interval in 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. The Type is 3, Length is 4 octets, and the value comprises of -

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.

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.

Adjustment-Threshold sub-TLV 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. The Type is 4, Length is 4 octets, and the value comprises of -

Adjustment-Threshold:: The absolute Adjustment-Threshold bandwidth difference value, encoded in IEEE floating point format (see []), expressed in bytes per second. The default adjustment-threshold value is not set. Refer to Section 3.1.2 of 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.

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. The Type is 5, Length is 8 octets, and the value comprises of -

Reserved:: MUST be set to zero on transmission and MUST be ignored on receipt.
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.
Minimum-Threshold:: The absolute Minimum-Threshold bandwidth value, encoded in IEEE floating point format (see []), 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.

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. The Type is 6, Length is 4 octets, and the value comprises of -

Down-Adjustment-Threshold:: The absolute Down-Adjustment-Threshold bandwidth value, encoded in IEEE floating point format (see []), expressed in bytes per second. The default value equals the adjustment-threshold. Refer to Section 3.1.2 of 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.

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. The Type is 7, Length is 8 octets, and the value comprises of -

Reserved:: MUST be set to zero on transmission and MUST be ignored on receipt.
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.
Minimum-Threshold:: The absolute Minimum-Threshold bandwidth value, encoded in IEEE floating point format (see []), 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. 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.

Minimum and Maximum Bandwidth Values

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. The Type is 8, Length is 4 octets, and the value comprises of -

Minimum-Bandwidth:: The 4-octet bandwidth value encoded in IEEE floating point format (see []), expressed in bytes per second. The default minimum-bandwidth value is set to 0. Refer to Section 3.1.2 of for a table of commonly used values.