| RFC 0000 | PCEP Extensions for MPLS-TE LSP Automati | October 2019 |
| Dhody, et al. | Standards Track | [Page] |
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.¶
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/rfc0000.¶
Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must 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.¶
[RFC5440] describes the Path Computation Element Protocol (PCEP) as a communication mechanism between a Path Computation Client (PCC) and a Path Computation Element (PCE), or between PCE and PCE, that enables computation of Multi-Protocol Label Switching (MPLS) Traffic Engineering Label Switched Paths (TE LSPs).¶
[RFC8231] specifies extensions to PCEP to enable stateful control of MPLS TE LSPs. It describes two mode of operations - Passive stateful PCE and Active stateful PCE. Further, [RFC8281] describes the setup, maintenance and teardown of PCE-Initiated LSPs for the stateful PCE model. In this document, the focus is on Active stateful PCE where the LSPs are controlled by the PCE.¶
Over time, based on the varying traffic pattern, an LSP established with a certain bandwidth may require adjustment of the bandwidth reserved in the network dynamically. The head-end Label Switch Router (LSR) monitors the actual bandwidth demand of the established LSP and periodically computes new bandwidth. The head-end LSR adjusts the bandwidth reservation of the LSP based on the computed bandwidth automatically. This feature, when available in the head-end Label Switching Router (LSR) implementation, is common referred to as Auto-Bandwidth. The Auto-Bandwidth feature is described in detail in Section 4 of this document.¶
In the model considered in this document, the PCC (head-end of the LSP) collects the traffic rate samples flowing through the LSP and calculates the new adjusted bandwidth. The PCC reports the calculated bandwidth to be adjusted to the PCE. This is similar to the Passive stateful PCE model: while the Passive stateful PCE uses a path request/reply mechanism, the Active stateful PCE uses a report/update mechanism. In case of PCE-Initiated LSP, the PCC is requested during the LSP initiation to monitor and calculate the new adjusted bandwidth. [RFC8051] describes the use-case for Auto-Bandwidth adjustment for Passive and Active stateful PCE.¶
Another approach would be to send the measured values itself to the PCE, which is considered out of scope for this document.¶
This document defines the PCEP extensions needed to support an Auto-Bandwidth feature in an Active stateful PCE model where the LSP bandwidth to be adjusted is calculated on the PCC (head-end of the LSP). The use of PCE to calculate the bandwidth to be adjusted is out of scope of this document.¶
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.¶
The reader is assumed to be familiar with the terminology defined in [RFC5440], [RFC8231], and [RFC8281].¶
In this document, the PCC is considered to be the head end LSR of the LSP. Other types of PCC are not in scope.¶
The following auto-bandwidth terminology is defined in this document.¶
The PCEP extensions required for auto-bandwidth are summarized in the following table as well as in Figure 1.¶
| PCC Initiated | PCE Initiated |
|---|---|
|
PCC monitors the traffic 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. |
----------
| |
| PCE |
| |
----------
| ^
AUTO-BANDWIDTH CAPABILITY | | AUTO-BANDWIDTH CAPABILITY
| |
AUTO-BANDWIDTH ATTRIBUTES | | AUTO-BANDWIDTH ATTRIBUTES
| | (For Delegated LSPs)
| |
| | REQUESTED BANDWIDTH
v |
----------
| |
| PCC |
| |
----------
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:¶
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 [RFC3209].¶
This section describes the Auto-Bandwidth feature in a general way. When the Auto-Bandwidth feature is enabled, the measured traffic rate is periodically sampled at each Sample-Interval by the PCC, when the PCC is the head-end node of the LSP. The sample interval can be configured by an operator, with a default value of 5 minutes. A very low Sample-Interval could have some undesirable interactions with transport protocols (see Section 6.6).¶
The traffic rate samples are accumulated over the Adjustment-Interval period (in the Up or Down direction). The period can be configured by an operator, with a default value of 24 hours. The PCC in-charge of calculating the bandwidth to be adjusted can decide to adjust the bandwidth of the LSP to the highest traffic rate sample (MaxAvgBw) amongst the set of bandwidth samples collected over the Adjustment-Interval period (in the Up or Down direction) depending on the operator policy.¶
Note that the highest traffic rate sample could be higher or lower than the current LSP bandwidth. Only if the difference between the current bandwidth demand (MaxAvgBw) and the current bandwidth reservation is greater than or equal to the Adjustment-Threshold the LSP bandwidth is adjusted (upsized) to the current bandwidth demand (MaxAvgBw). The Adjustment-Threshold could be an absolute value or a percentage. The threshold can be configured by an operator, with a default value of 5 percentage. Similarly, if the difference between the current bandwidth reservation and the current bandwidth demand (MaxAvgBw) is greater than or equal to the Down-Adjustment-Threshold (percentage or absolute value), the LSP bandwidth is adjusted (downsized) to the current bandwidth demand (MaxAvgBw). Some LSPs are less eventful while other LSPs may encounter a lot of changes in the traffic pattern. The thresholds and intervals for bandwidth adjustment are configured based on the traffic pattern of the LSP.¶
In order to avoid frequent re-signaling, an operator may set a longer adjustment-interval value (Up and/or Down). However, a longer Adjustment-Interval can result in an undesirable effect of masking sudden changes in traffic demands of an LSP. To avoid this, the Auto-Bandwidth feature may prematurely expire the adjustment interval and adjust the LSP bandwidth to accommodate the sudden bursts of increase in traffic demand as an overflow condition or decrease in traffic demand as an underflow condition. An operator needs to 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.¶
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).¶
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 AUTO-BANDWIDTH-CAPABILITY TLV is an optional TLV for use in the OPEN Object for Automatic Bandwidth Adjustment via PCEP capability advertisement. Its format is shown in the following figure:¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD2 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
AUTO-BANDWIDTH-CAPABILITY TLV format
¶
The Type of the TLV is (TBD2) and it has a fixed Length of 4 octets.¶
The value comprises a single field - Flags (32 bits). No flags are defined for this TLV in this document.¶
Unassigned bits are considered reserved. They MUST be set to 0 on transmission and MUST be ignored on receipt.¶
Advertisement of the AUTO-BANDWIDTH-CAPABILITY TLV implies support of auto-bandwidth adjustment, as well as the objects, TLVs and procedures defined in this document.¶
The AUTO-BANDWIDTH-ATTRIBUTES TLV provides the 'configurable knobs' of the feature and it can be included as an optional TLV in the LSPA Object (as described in [RFC5440]).¶
For PCE-Initiated LSP [RFC8281], this TLV is included in the LSPA Object with the PCInitiate message. For the PCC-Initiated delegated LSPs, this TLV is carried in the PCRpt message in LSPA Object. This TLV is also carried in the LSPA object with the PCUpd message to direct the PCC (LSP head-end) to make updates to auto-bandwidth attributes such as Adjustment-Interval.¶
The TLV is encoded in all PCEP messages for the LSP while the auto-bandwidth adjustment feature is enabled, the absence of the TLV indicates the PCEP speaker wishes to disable the feature. This TLV includes multiple AUTO-BANDWIDTH-ATTRIBUTES sub-TLVs. The AUTO-BANDWIDTH-ATTRIBUTES sub-TLVs are included if there is a change since the last information sent in the PCEP message. The default values for missing sub-TLVs apply for the first PCEP message for the LSP.¶
The format of the AUTO-BANDWIDTH-ATTRIBUTES TLV is shown in the following figure:¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD1 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// sub-TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
AUTO-BANDWIDTH-ATTRIBUTES TLV format
¶
Following sub-TLVs are defined in this document:¶
Type Len Name ------------------------------------------------------------------- 1 4 Sample-Interval sub-TLV 2 4 Adjustment-Interval sub-TLV 3 4 Down-Adjustment-Interval sub-TLV 4 4 Adjustment-Threshold sub-TLV 5 8 Adjustment-Threshold-Percentage sub-TLV 6 4 Down-Adjustment-Threshold sub-TLV 7 8 Down-Adjustment-Threshold-Percentage sub-TLV 8 4 Minimum-Bandwidth sub-TLV 9 4 Maximum-Bandwidth sub-TLV 10 8 Overflow-Threshold sub-TLV 11 8 Overflow-Threshold-Percentage sub-TLV 12 8 Underflow-Threshold sub-TLV 13 8 Underflow-Threshold-Percentage sub-TLV¶
Future specifications can define additional sub-TLVs.¶
The sub-TLVs are encoded to inform the PCEP peer of the various sampling and adjustment parameters. In case of a missing sub-TLV, as per the local policy, either the default value (as specified in this document) or some other operator configured value is used.¶
All sub-TLVs are optional and any unrecognized sub-TLV MUST be ignored. If a sub-TLV of the same type appears more than once, only the first occurrence is processed and all others MUST be ignored.¶
The following sub-sections describe the sub-TLVs which are currently defined to be carried within the AUTO-BANDWIDTH-ATTRIBUTES TLV.¶
The Sample-Interval sub-TLV specifies a time interval in seconds at which traffic samples are collected at the PCC.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=1 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sample-Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sample-Interval sub-TLV format
¶
The Type is 1, Length is 4 octets, and the value comprises of -¶
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.¶
The Adjustment-Interval sub-TLV specifies a time interval in seconds at which bandwidth adjustment should be made in upward or downward direction. This sub-TLV specify the value for Up-Adjustment-Interval and Down-Adjustment-Interval when they are the same and the Down-Adjustment-Interval sub-TLV is not included.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=2 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Adjustment-Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Adjustment-Interval sub-TLV format
¶
The Type is 2, Length is 4 octets, and the value comprises of -¶
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.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=3 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Down-Adjustment-Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Down-Adjustment-Interval sub-TLV format
¶
The Type is 3, Length is 4 octets, and the value comprises of -¶
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.¶
The Adjustment-Threshold sub-TLV is used to decide when the LSP bandwidth should be adjusted in upward or downward direction. This sub-TLV specify the absolute value for Up-Adjustment-Threshold and Down-Adjustment-Threshold when they are the same and the Down-Adjustment-Threshold sub-TLV is not included.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=4 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Adjustment-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Adjustment-Threshold sub-TLV format
¶
The Type is 4, Length is 4 octets, and the value comprises of -¶
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.¶
The Adjustment-Threshold-Percentage sub-TLV is used to decide when the LSP bandwidth should be adjusted in upward or downward direction. This sub-TLV specify the percentage value for Up-Adjustment-Threshold and Down-Adjustment-Threshold when they are the same and the Down-Adjustment-Threshold-Percentage sub-TLV is not included.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=5 | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Percentage |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Adjustment-Threshold-Percentage sub-TLV format
¶
The Type is 5, Length is 8 octets, and the value comprises of -¶
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.¶
The Down-Adjustment-Threshold sub-TLV is used to decide when the LSP bandwidth should be adjusted when MaxAvgBw is lesser than the current bandwidth reservation. This parameter overrides the Adjustment-Threshold for the downward trend. This sub-TLV is used only when there is a need for different threshold in the upward and downward directions.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=6 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Down-Adjustment-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Down-Adjustment-Threshold sub-TLV format
¶
The Type is 6, Length is 4 octets, and the value comprises of -¶
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.¶
The Down-Adjustment-Threshold-Percentage sub-TLV is used to decide when the LSP bandwidth should be adjusted when MaxAvgBw is lesser than the current bandwidth reservation. This parameter overrides the Adjustment-Threshold-Percentage for the downward trend. This sub-TLV is used only when there is a need for different threshold percentage in the upward and downward directions.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=7 | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Percentage |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Down-Adjustment-Threshold-Percentage sub-TLV format
¶
The Type is 7, Length is 8 octets, and the value comprises of -¶
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.¶
The Minimum-Bandwidth sub-TLV specify the minimum bandwidth allowed for the LSP, and is expressed in bytes per second. The LSP bandwidth cannot be adjusted below the minimum bandwidth value.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=8 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum-Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Minimum-Bandwidth sub-TLV format
¶
The Type is 8, Length is 4 octets, and the value comprises of -¶
In case of an invalid value, the Sub-TLV MUST be ignored and the previous value is maintained.¶
The Maximum-Bandwidth sub-TLV specify the maximum bandwidth allowed for the LSP, and is expressed in bytes per second. The LSP bandwidth cannot be adjusted above the maximum bandwidth value.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=9 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum-Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Maximum-Bandwidth sub-TLV format
¶
The Type is 9, Length is 4 octets, and the value comprises of -¶
In case of an invalid value, the Sub-TLV MUST be ignored and the previous value is maintained.¶
The sub-TLVs in this section are encoded to inform the PCEP peer the overflow and underflow threshold parameters. An implementation MAY include sub-TLVs for an absolute value and/or a percentage for the threshold, in which case the bandwidth is immediately adjusted when either of the threshold conditions is met consecutively for the given count (as long as the difference in the bandwidth is at least or above the Minimum-Threshold). By default, the threshold values for overflow and underflow conditions are not set.¶
The Overflow-Threshold sub-TLV is used to decide if the LSP bandwidth should be adjusted immediately.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=10 | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Overflow-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Overflow-Threshold sub-TLV format
¶
The Type is 10, Length is 8 octets, and the value comprises of -¶
In case of an invalid value, the Sub-TLV MUST be ignored and the previous value is maintained.¶
The Overflow-Threshold-Percentage sub-TLV is used to decide if the LSP bandwidth should be adjusted immediately.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=11 | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Percentage | Reserved | Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Overflow-Threshold-Percentage sub-TLV format
¶
The Type is 11, Length is 8 octets, and the value comprises of -¶
In case of an invalid value, the Sub-TLV MUST be ignored and the previous value is maintained.¶
The Underflow-Threshold sub-TLV is used to decide if the LSP bandwidth should be adjusted immediately.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=12 | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Underflow-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Underflow-Threshold sub-TLV format
¶
The Type is 12, Length is 8 octets, and the value comprises of -¶
In case of an invalid value, the Sub-TLV MUST be ignored and the previous value is maintained.¶
The Underflow-Threshold-Percentage sub-TLV is used to decide if the LSP bandwidth should be adjusted immediately.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=13 | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Percentage | Reserved | Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum-Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Underflow-Threshold-Percentage sub-TLV format
¶
The Type is 13, Length is 8 octets, and the value comprises of -¶
In case of an invalid value, the Sub-TLV MUST be ignored and the previous value is maintained.¶
As per [RFC5440], the BANDWIDTH object (Object-Class value 5) is defined with two Object-Type values as following:¶
The PCC reports the calculated bandwidth to be adjusted (MaxAvgBw) to the Stateful PCE using the existing 'Requested Bandwidth' with BANDWIDTH Object-Type as 1. The reporting of the 're-optimization bandwidth' with BANDWIDTH Object-Type as 2 is not required as the Stateful PCE is aware of the existing LSP bandwidth.¶
A PCInitiate message is a PCEP message sent by a PCE to a PCC to trigger LSP instantiation or deletion [RFC8281].¶
For the PCE-Initiated LSP with Auto-Bandwidth feature enabled, AUTO-BANDWIDTH-ATTRIBUTES TLV MUST be included in the LSPA object with the PCInitiate message.¶
The Routing Backus-Naur Format (RBNF) definition of the PCInitiate message [RFC8281] is unchanged by this document.¶
A PCUpd message is a PCEP message sent by a PCE to a PCC to update the LSP parameters [RFC8231].¶
For PCE-Initiated LSPs with Auto-Bandwidth feature enabled, AUTO-BANDWIDTH-ATTRIBUTES TLV MUST be included in the LSPA object with the PCUpd message. The PCE can send this TLV to direct the PCC to change the auto-bandwidth parameters.¶
The RBNF definition of the PCUpd message [RFC8231] is unchanged by this document.¶
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 using the local values for the unspecified parameters. After the successful instantiation of the LSP, PCC automatically delegates the LSP to the PCE and generates a PCRpt message to provide the status report for the LSP.¶
For both PCE-Initiated and PCC-Initiated LSPs, when the LSP is delegated to a PCE for the very first time as well as after the successful delegation, the BANDWIDTH object of type 1 is used to specify the requested bandwidth in the PCRpt message.¶
The RBNF definition of the PCRpt message [RFC8231] is unchanged by this document.¶
As per [RFC5440], the PCEP Notification message (PCNtf) can be sent by a PCEP speaker to notify its peer of a specific event.¶
A PCEP speaker (PCE or PCC) SHOULD notify its PCEP peer (PCC or PCE) when it is in overwhelmed state due to the auto-bandwidth feature. An implementation needs to make an attempt to send this notification (when overwhelmed by auto-bandwidth adjustments) unless sending this notification would only serve to increase the load further. Note that when the notification is not received the PCEP speaker would continue to request bandwidth adjustments even when they could not be handled in a timely fashion.¶
Upon receipt of auto-bandwidth overwhelm notification, the peer SHOULD NOT send any PCEP messages related to auto-bandwidth adjustment. If a PCEP message related to auto-bandwidth adjustment is received during in overwhelmed state, it MUST be ignored.¶
When Auto-Bandwidth feature is deployed, a PCE can send this notification to PCC when a PCC is reporting frequent auto-bandwidth adjustments. If a PCC is overwhelmed with re-signaling, it can also notify the PCE to not adjust the LSP bandwidth while in overwhelm state.¶
Some dampening notification procedure (as per [RFC5440]) to avoid oscillations of the overwhelm state is RECOMMENDED. On receipt of an auto-bandwidth overwhelm notification from the PCE, a PCC should consider the impact on the entire network. Moving the delegations of auto-bandwidth enabled LSP to another PCE could cause further overloading.¶
The Auto-Bandwidth feature SHOULD be controlled per LSP (at PCC (head-end of the LSP) or PCE) and the values for auto-bandwidth parameters e.g. sample-interval, adjustment-interval (up/down), minimum-bandwidth, maximum-bandwidth, adjustment-threshold (up/down) SHOULD be configurable by an operator.¶
The Maximum-Bandwidth (and Minimum-Bandwidth) should be set to acceptable limit to avoid impact on the rest of the MPLS-TE domain.¶
The operator should make sure that the Overflow-Threshold is greater than or at least equal to the Up-Adjustment-Threshold. And similarly, make sure that the Underflow-Threshold is greater than or at least equal to the Down-Adjustment-Threshold.¶
A MIB module for gathering operational information about PCEP is defined in [RFC7420]. Additionally, the YANG module defined in [PCE-PCEP-YANG] provides for both configuration of PCEP as well as operational management. These could be enhanced to provide controls and indicators for support of auto-bandwidth feature. Support for various configuration knobs as well as counters of messages sent/received containing the TLVs defined in this document could be added.¶
The mechanisms defined in this document do not imply any new liveness detection and monitoring requirements in addition to those already listed in [RFC5440].¶
The mechanisms defined in this document do not imply any new operation verification requirements in addition to those already listed in [RFC5440].¶
In case of an invalid value, the Sub-TLV would get ignored and the previous value would be maintained. In such case the implementation SHOULD log the event.¶
The mechanisms defined in this document do not add any new requirements on other protocols.¶
In order to avoid any unacceptable impact on network operations, an implementation SHOULD allow a limit to be placed on the number of LSPs that can be enabled with auto-bandwidth feature. For each LSP enabled with auto-bandwidth feature there is an extra load on PCC, as it needs to monitor the traffic and report the calculated bandwidth to be adjusted to the PCE. The PCE further re-compute paths based on the requested bandwidth and update the path to the PCC, which in turns triggers the re-signaling of the path. All these steps adds extra load and churn in the network and thus operator needs to take due care while enabling this features on a number of LSPs.¶
An implementation MAY allow a limit to be placed on the rate of auto-bandwidth related messages sent by a PCEP speaker and received by a peer. An implementation SHOULD also allow sending a notification when a PCEP speaker is overwhelmed or the rate of messages reach a threshold.¶
Due care is required by the operator if a Sample-Interval value significantly smaller than the default (5 minute) is used, as a small Sample-Interval values, e.g., 1 minute or less, could cause undesirable interactions with transport protocols. These undesirable interactions result from providing insufficient time for transport protocol reactions to a prior bandwidth adjustment to settle out before bandwidth samples are taken for the next bandwidth adjustment.¶
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.¶
This document defines the following new PCEP TLVs; IANA is requested to make the following allocations from the "PCEP TLV Type Indicators" sub-registry of the PCEP Numbers registry, as follows:¶
Value Name Reference ----------------------------------------------------------------- TBD2 AUTO-BANDWIDTH-CAPABILITY [This document] TBD1 AUTO-BANDWIDTH-ATTRIBUTES [This document]¶
IANA is requested to create a sub-registry to manage the Flag field of the AUTO-BANDWIDTH-CAPABILITY TLV within the "Path Computation Element Protocol (PCEP) Numbers" registry.¶
New bit numbers are to be assigned by Standards Action [RFC8126]. Each bit should be tracked with the following qualities:¶
The initial contents of the sub-registry are empty, with all bits marked unassigned¶
This document specifies the AUTO-BANDWIDTH-ATTRIBUTES Sub-TLVs. IANA is requested to create an "AUTO-BANDWIDTH-ATTRIBUTES Sub-TLV Types" sub-registry within the "Path Computation Element Protocol (PCEP) Numbers" registry to manage the type indicator space for sub-TLVs of the AUTO-BANDWIDTH-ATTRIBUTES TLV. The valid range of values in the registry is 0-65535. IANA is requested to initialize the registry with the following values. All other values in the registry should be marked as "Unassigned".¶
IANA is requested to set the registration procedure for this registry to read as follows:¶
0-65503 IETF Review
65504-65535 Experimental Use
This document defines the following types:
Type Name Reference
-----------------------------------------------------------------
0 Reserved [This document]
1 Sample-Interval sub-TLV [This document]
2 Adjustment-Interval sub-TLV [This document]
3 Down-Adjustment-Interval sub-TLV [This document]
4 Adjustment-Threshold sub-TLV [This document]
5 Adjustment-Threshold-Percentage sub-TLV [This document]
6 Down-Adjustment-Threshold sub-TLV [This document]
7 Down-Adjustment-Threshold-Percentage sub-TLV [This document]
8 Minimum-Bandwidth sub-TLV [This document]
9 Maximum-Bandwidth sub-TLV [This document]
10 Overflow-Threshold sub-TLV [This document]
11 Overflow-Threshold-Percentage sub-TLV [This document]
12 Underflow-Threshold sub-TLV [This document]
13 Underflow-Threshold-Percentage sub-TLV [This document]
14- Unassigned [This document]
65503
¶
This document defines a new Error-Value for PCErr message of Error-Type 19 (Invalid Operation) [RFC8231]. IANA is requested to allocate new error-value within the "PCEP-ERROR Object Error Types and Values" subregistry of the PCEP Numbers registry, as follows:¶
Error-Type Meaning & error values Reference
-----------------------------------------------------------------
19 Invalid Operations
Error-Value = TBD4: [This document]
Auto-Bandwidth Capability
was not Advertised
¶
IANA is requested to allocate new Notification Type and Notification Values within the "Notification Object" sub-registry of the PCEP Numbers registry, as follows:¶
Type Meaning Reference
-----------------------------------------------------------------
TBD3 Auto-Bandwidth Overwhelm State [This document]
Notification-value=1: Entering Auto-Bandwidth
overwhelm state
Notification-value=2: Clearing Auto-Bandwidth
overwhelm state
¶
Authors would like to thank Robert Varga, Venugopal Reddy, Reeja Paul, Sandeep Boina, Avantika, JP Vasseur, Himanshu Shah, Jonathan Hardwick and Adrian Farrel for their useful comments and suggestions.¶
Thanks to Daniel Franke, Joe Clarke, David Black, and Erik Kline for the directorate reviews.¶
Thanks to Mirja Kuhlewind, Barry Leiba, Benjamin Kaduk, and Roman Danyliw for the IESG review.¶
He Zekun Tencent Holdings Ltd, Shenzhen P.R.China Email: kinghe@tencent.com Xian Zhang Huawei Technologies Research Area F3-1B, Huawei Industrial Base, Shenzhen, 518129 China Phone: +86-755-28972645 Email: zhang.xian@huawei.com Young Lee SKKU Email: younglee.tx@gmail.com¶