Internet DRAFT - draft-xiong-pce-stateful-pce-bandwidth-scheduling
draft-xiong-pce-stateful-pce-bandwidth-scheduling
PCE WG Quan. Xiong
Internet-Draft Fangwei. Hu
Intended status: Standards Track Ran. Chen
Expires: June 8, 2017 ZTE Corporation
December 5, 2016
stateful pce bandwidth scheduling
draft-xiong-pce-stateful-pce-bandwidth-scheduling-01.txt
Abstract
The Path Computation Element Communication Protocol (PCEP) provides
mechanisms for Path Computation Elements (PCEs) to perform path
computations in response to Path Computation Clients (PCCs) requests.
The stateful PCE extensions allow stateful control of Multi-Protocol
Label Switching (MPLS) Traffic Engineering Label Switched Paths (TE
LSPs) using PCEP.
This document proposes a set of extensions for the stateful PCE, so
as to enable bandwidth scheduling for LSP and adjust the bandwidth
based on the customers' scheduled bandwidth requirement of a traffic
service in a centralized network environment. A bandwidth scheduled
LSP can be adjusted to the new bandwidth at its starting time and
adjusted back to the original bandwidth at its ending time.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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and may be updated, replaced, or obsoleted by other documents at any
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This Internet-Draft will expire on June 8, 2017.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
3. Bandwidth scheduling Overview . . . . . . . . . . . . . . . . 4
4. New function to support Bandwidth scheduling . . . . . . . . 4
5. Extensions to the PCEP . . . . . . . . . . . . . . . . . . . 5
5.1. Support of Bandwidth Scheduling Capability . . . . . . . 5
5.1.1. Stateful PCE Capability TLV . . . . . . . . . . . . . 5
5.2. Scheduled Bandwidth adjustment . . . . . . . . . . . . . 5
5.2.1. SCHED-BW-ADJUST-ATTRIBUTE TLV . . . . . . . . . . . . 6
5.2.2. The PCReq Message . . . . . . . . . . . . . . . . . . 8
5.2.3. The PCRpt Message . . . . . . . . . . . . . . . . . . 8
5.2.4. The PCUpd Message . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 9
7.2. SCHED-BW-ADJUST-CAPABLITY . . . . . . . . . . . . . . . . 9
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Informative References . . . . . . . . . . . . . . . . . 10
9.2. Normative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
[RFC5440] describes the Path Computation Element Protocol (PCEP)
which is used between a Path Computation Element (PCE) and a Path
Computation Client (PCC) (or other PCE) to enable computation of
Multi-protocol Label Switching (MPLS) for Traffic Engineering Label
Switched Path (TE LSP).[I-D.ietf-pce-stateful-pce] specifies a set of
extensions to PCEP to enable stateful control of MPLS TE LSPs.
[I-D.ietf-pce-pce-initiated-lsp] describes the setup, maintenance and
teardown of PCE-initiated LSPs for the stateful PCE model.
In some scenarios, an LSP established with certain bandwidth may
require to adjust its bandwidth to a particular value during a period
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of time so as to satisfy the network traffic requirement.
Traditionally, this can be supported by network management system
(NMS) operation through path pre-configuration on the agreed time or
accomplished through GMPLS protocol extensions by carrying the
related request information across the network. However, as the
[I-D.ietf-pce-stateful-pce-app] discussed, this does not provide
efficient network usage and will increase the complexity.
[I-D.ietf-pce-stateful-pce-app] describes the requirement of
bandwidth scheduling, so as to provide more efficient network
resource usage for traffic engineering, and allows network operators
to reserve resources in advance according to the agreements with
their customers, and allow them to transmit data with specified
starting time and duration.
This document proposes bandwidth scheduling and provides scheduled
bandwidth adjustment for LSP, so as to adjust the bandwidth to the
new value at the starting time and return to the original bandwidth
after the duration time. With the scheduled reservation of TE
resources, it allows network operators to require scheduled bandwidth
adjustment and resource according to the agreements with their
customers, and allow them to transmit data with scheduled bandwidth
such as specified starting time and ending time.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2.1. Terminology
The terminology is defined as [RFC5440] and
[I-D.ietf-pce-stateful-pce-app] except the following which proposed
in this document:
Scheduled Bandwidth (Bandwidth Scheduling): a LSP with the scheduling
bandwidth, that carries the demand bandwidth at a starting time and
adjust to its original bandwidth at an ending time.
Starting time: This value indicates the time when the scheduled
bandwidth is adjusted to the new value.
Ending time: The value indicates the time when the scheduled
bandwidth is adjusted to the original value.
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3. Bandwidth scheduling Overview
The bandwidth scheduling allows PCEs and PCCs to provide scheduled
bandwidth adjustment for customers' traffic services at its
particular usage time, so as to improve the network control of
traffic flowing.
For a passive stateful PCE, it can support this application with
better efficiency and PCCs need to send request to PCEs for bandwidth
scheduling including its scheduling parameters.
For an active stateful PCE, the PCE can trigger the scheduled
requests in a centralized manner, as specified in
[I-D.ietf-pce-pce-initiated-lsp], by notifying the PCCs to modify the
paths and adjust the bandwidth. And the scheduled bandwidth
information is then configured by NMS or customers.
Then the stateful PCE must reserve the network resource for the
traffic and computes a path for the scheduled bandwidth. This
requires the PCE to maintain the LSPs, scheduled bandwidth parameters
and their associated resource usage, as well as the ability of head-
ends to trigger signaling for LSP adjustment at the correct time
which uses the make-before-break signaling method so that there is no
interruption to the traffic flow.
In both cases, this requires resource reservation and time
synchronization between PCEs and PCCs which is to be discussed in the
future.
4. New function to support Bandwidth scheduling
Several new functions are required in PCEP to support stateful PCEs.
A function can be initiated either from a PCC towards a PCE (C-E) or
from a PCE towards a PCC (E-C).
The new functions are:
Capability advertisement (E-C,C-E): both the PCC and the PCE must
announce during PCEP session establishment that they support PCEP
Stateful PCE bandwidth scheduling extensions defined in this
document.
LSP Path Computation Request (C-E): for PCC-Initiated bandwidth
scheduling, a PCC can send a request within a path computation
request message to PCE with the extensions defined in this document.
LSP State Report (C-E): for PCC-Initiated bandwidth scheduling, LSP
creation and bandwidth scheduling request can be separated and the
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PCC can send a report message including its bandwidth scheduling
information to PCE with the extensions defined in this document.
LSP Update Request (E-C): when the time expires, the PCE SHALL send a
update message with the path result to adjust the bandwidth of the
LSP.
5. Extensions to the PCEP
5.1. Support of Bandwidth Scheduling Capability
5.1.1. Stateful PCE Capability TLV
The STATEFUL-PCE-CAPABILITY TLV MUST support bandwidth scheduling in
Open Object which contained in Open message, as defined in
[I-D.ietf-pce-stateful-pce] and updated in [I-D.ietf-pce-pce-initiate
d-lsp],[I-D.ietf-pce-stateful-sync-optimizations]. In this document,
a new flag bit A (SCHED-BW-ADJUST-CAPABLITY) is defined for the
STATEFUL- PCE-CAPABILITY TLV to indicate the capability of bandwidth
scheduling.
The format of STATEFUL-PCE-CAPABILITY TLV is shown as follow. I, S
and U is defined in other documents which mentioned above.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=[TBD] | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |A|I|S|U|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1 SCHED-BW-ADJUST-CAPABILITY Flags format
A (SCHED-BW-ADJUST-CAPABLITY - 1 bit): If set to 1 by a PCC, the A
Flag indicates that the PCC allows bandwidth scheduling; if set to 1
by a PCE, the A Flag indicates that the PCE is capable of bandwidth
scheduling. The A bit MUST be set by both PECP peers in order to
support bandwidth scheduling for path computation.
5.2. Scheduled Bandwidth adjustment
In order to realize bandwidth scheduling in a centralized network
environment, it has to separate the process into two steps. The
first step is to send request to PCEs, so as to configure the
scheduled parameters and reserve the resource over the network. The
second step is to trigger the adjustment to PCCs to re-signal the LSP
with the scheduled bandwidth over the network at its starting time
and ending time.
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To realize PCC-Initiated bandwidth scheduling, the PCC MAY send the
bandwidth scheduling request to PCE. Alternatively, the PCE-
Initiated bandwidth scheduling request is triggered by NMS or users.
If the bandwidth scheduling request is accepted, the stateful PCE MAY
compute a path based on the scheduled bandwidth and adjust the
bandwidth of that LSP at its scheduled time by send a PCUpd message
with path computation result and SCHED-BW-ADJUST-ATTRIBUTE TLV.
When the ending time expires, the PCE shall send a PCUpd message with
the original path and bandwidth of the LSP to adjust back.
The PCC which received the message SHOULD minimize the traffic
interruption, and MAY use the make-before-break procedures in order
to achieve this bandwidth adjustment.
5.2.1. SCHED-BW-ADJUST-ATTRIBUTE TLV
The LSP object is defined in [I-D.ietf-pce-stateful-pce]. This
document adds an optional SCHED-BW-ADJUST-ATTRIBUTE TLV.
The SCHED-BW-ADJUST-ATTRIBUTE TLV in the LSP object indicates that
this LSP is requesting scheduled bandwidth parameters. The LSP
Object with that TLV carried in the PCReq message, the PCRpt message
and the PCUpd message MUST be presented for each LSP which requires
scheduled bandwidth.
The SCHED-BW-ADJUST-ATTRIBUTE TLV can be included as an optional TLV
within the LSP object for Bandwidth scheduling for the requesting
traffic service.
This TLV SHOULD be included only if both PCEP peers have set the A
(SCHED-BW-ADJUST-CAPABILITY bit) in STATEFUL-PCE-CAPABILITY TLV
carried in open message.
The format of the SCHED-BW-ADJUST-ATTRIBUTE TLV is shown in the
following figure:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Starting Time |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Ending Time |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2 SCHED-BW-ADJUST-ATTRIBUTE TLV format
The time format including starting time and ending time is YYYY-MM-
DD-HH-MM and it indicates year, month, date, hour and minute
respectively as follows.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Year |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Month | Date |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hour | Minute |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3 Time TLV format
o The type of the TLV is [TBD]. The fields in the format are:
o Starting Time (32 * 3 bits): This value in minutes, indicates when
the bandwidth of LSP is adjusted to the scheduled bandwidth.
o Ending Time (32 * 3 bits): The value in minutes, indicates when
the scheduled bandwidth is adjusted to the original value.
o Bandwidth (32 bits): The value indicates the scheduled bandwidth
which the LSP is adjusted during the period of time and its detail
format see [RFC5440].
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Note, that the values of starting time and ending time is from the
perspective of the PCEP peer that is sending the message, also note
the unit of time is minutes, and thus the time spent on transmission
on wire can be easily ignored.
5.2.2. The PCReq Message
For PCC-Initiated bandwidth scheduling, a PCC can choose to send
request within a path computation request (PCReq) message or not.
If a PCC send a PCReq message with SCHED-BW-ADJUST-ATTRIBUTE TLV in
LSP object, the PCE MUST compute a path for that LSP and check the
scheduled request, reserve the resource and store the scheduled
information. If that is satisfied, the PCE SHALL sends a PCRep
message with the SCHED-LSP-ATTRIBUTE TLV, as well as the LSP Object
and path result back to the requesting PCC.
If failures happen or no resource available for the current path, the
requesting PCE SHALL return a PCRep message with NO PATH back to the
PCC.
If failures happen or no resource reservation for scheduled bandwidth
request, the requesting PCE SHALL return a PCErr message with PCEP-
ERROR object back to the PCC.
5.2.3. The PCRpt Message
For PCC-Initiated, creation and bandwidth scheduling request can be
separated. If a LSP is already set up, the PCC can choose report
(PCRpt) message including its bandwidth scheduling information and
delegation to a stateful PCE.
Upon receiving the delegation via PCRpt message, the stateful PCE
computes the path for the LSP per its starting time and ending time
based on bandwidth scheduling parameters.
If failures happen or no resource reservation for scheduled bandwidth
request, the requesting PCE SHALL return a PCErr message with PCEP-
ERROR object back to the PCC.
5.2.4. The PCUpd Message
When the starting time or ending time expires, if the scheduled
bandwidth request from PCCs or NMS can be satisfied and an available
path is computed, the stateful PCE SHALL send a PCUpd Message
including path computation result and the SCHED-BW-ADJUST-ATTRIBUTE
TLV in the LSP Object body to the PCC, so as to adjust the bandwidth
of the LSP.
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Moreover, the stateful PCE can update the scheduled bandwidth
parameters at any time based on bandwidth requirement from customer
using the PCUpd message including SCHED-BW-ADJUST-ATTRIBUTE TLV in
the LSP Object body.
6. Security Considerations
TBD
7. IANA Considerations
7.1. PCEP TLV Type Indicators
This document defines the following new PCEP TLV; IANA is requested
to make the following allocations from this registry.
+--------+----------------------------+------------------+
| Value | Meaning | Reference |
+--------+----------------------------+------------------+
| TBD | SCHED-BW-ADJUST-ATTRIBUTE | [this document] |
+--------+----------------------------+------------------+
Table 1
7.2. SCHED-BW-ADJUST-CAPABLITY
This document requests that a registry is created to manage the Flags
field in the STATEFUL-PCE-CAPABILITY TLV in the OPEN object. New
values are to be assigned by Standards Action [RFC5226].
+------+------------------------------------+------------------+
| Bit | Description | Reference |
+------+------------------------------------+------------------+
| TBD | SCHED-BW-ADJUST-CAPABILITY (A-bit) | [this document] |
+------+------------------------------------+------------------+
Table 2
8. Acknowledgements
TBD.
9. References
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9.1. Informative References
[I-D.ietf-pce-stateful-pce-app]
Zhang, X. and I. Minei, "Applicability of a Stateful Path
Computation Element (PCE)", draft-ietf-pce-stateful-pce-
app-08 (work in progress), October 2016.
9.2. Normative References
[I-D.ietf-pce-pce-initiated-lsp]
Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
Extensions for PCE-initiated LSP Setup in a Stateful PCE
Model", draft-ietf-pce-pce-initiated-lsp-07 (work in
progress), July 2016.
[I-D.ietf-pce-stateful-pce]
Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP
Extensions for Stateful PCE", draft-ietf-pce-stateful-
pce-18 (work in progress), December 2016.
[I-D.ietf-pce-stateful-sync-optimizations]
Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X.,
and D. Dhody, "Optimizations of Label Switched Path State
Synchronization Procedures for a Stateful PCE", draft-
ietf-pce-stateful-sync-optimizations-06 (work in
progress), October 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://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,
<http://www.rfc-editor.org/info/rfc5440>.
Authors' Addresses
Quan Xiong
ZTE Corporation
No.6 Huashi Park Rd
Wuhan, Hubei 430223
China
Phone: +86 27 83531060
Email: xiong.quan@zte.com.cn
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Fangwei Hu
ZTE Corporation
No.889 Bibo Rd
Shanghai 201203
China
Phone: +86 21 68896273
Email: hu.fangwei@zte.com.cn
Ran Chen
ZTE Corporation
No.50 Software Avenue,Yuhuatai District
Nanjing, Jiangsu Province 210012
China
Phone: +86 025 88014636
Email: chen.ran@zte.com.cn
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