PCEP Extensions for LSP scheduling with stateful PCE
draft-ietf-pce-stateful-pce-lsp-scheduling-02
PCE Working Group H. Chen, Ed.
Internet-Draft Y. Zhuang, Ed.
Intended status: Standards Track Q. Wu
Expires: September 3, 2018 D. Dhody, Ed.
Huawei
D. Ceccarelli
Ericsson
March 2, 2018
PCEP Extensions for LSP scheduling with stateful PCE
draft-ietf-pce-stateful-pce-lsp-scheduling-02
Abstract
This document proposes a set of extensions needed to the stateful
Path Computation Element (PCE) communication Protocol (PCEP), so as
to enable Labeled Switched Path (LSP) scheduling for path computation
and LSP setup/deletion based on the actual network resource usage
duration of a traffic service in a centralized network environment as
stated in [I-D.ietf-teas-scheduled-resources].
Status of This Memo
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This Internet-Draft will expire on September 3, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 4
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
3. Motivation and Objectives . . . . . . . . . . . . . . . . . . 5
4. Architecture Overview . . . . . . . . . . . . . . . . . . . . 5
4.1. LSP scheduling Overview . . . . . . . . . . . . . . . . . 5
4.2. Support of LSP Scheduling . . . . . . . . . . . . . . . . 7
4.2.1. LSP Scheduling . . . . . . . . . . . . . . . . . . . 7
4.2.2. Periodical LSP Scheduling . . . . . . . . . . . . . . 7
4.3. Scheduled LSP creation . . . . . . . . . . . . . . . . . 8
4.4. Scheduled LSP Modifications . . . . . . . . . . . . . . . 10
4.5. Scheduled LSP activation and deletion . . . . . . . . . . 10
5. PCEP Objects and TLVs . . . . . . . . . . . . . . . . . . . . 11
5.1. Stateful PCE Capability TLV . . . . . . . . . . . . . . . 11
5.2. LSP Object . . . . . . . . . . . . . . . . . . . . . . . 12
5.2.1. SCHED-LSP-ATTRIBUTE TLV . . . . . . . . . . . . . . . 12
5.2.2. SCHED-PD-LSP-ATTRIBUTE TLV . . . . . . . . . . . . . 14
6. The PCEP Messages . . . . . . . . . . . . . . . . . . . . . . 15
6.1. The PCRpt Message . . . . . . . . . . . . . . . . . . . . 15
6.2. The PCUpd Message . . . . . . . . . . . . . . . . . . . . 15
6.3. The PCInitiate Message . . . . . . . . . . . . . . . . . 16
6.4. The PCReq message . . . . . . . . . . . . . . . . . . . . 16
6.5. The PCRep Message . . . . . . . . . . . . . . . . . . . . 16
6.6. The PCErr Message . . . . . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
8. Manageability Consideration . . . . . . . . . . . . . . . . . 17
8.1. Control of Function and Policy . . . . . . . . . . . . . 17
8.2. Information and Data Models . . . . . . . . . . . . . . . 17
8.3. Liveness Detection and Monitoring . . . . . . . . . . . . 17
8.4. Verify Correct Operations . . . . . . . . . . . . . . . . 17
8.5. Requirements On Other Protocols . . . . . . . . . . . . . 17
8.6. Impact On Network Operations . . . . . . . . . . . . . . 17
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
9.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 18
9.2. STATEFUL-PCE-CAPABILITY TLV Flag field . . . . . . . . . 18
9.3. Schedule TLVs Flag Field . . . . . . . . . . . . . . . . 18
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
11.1. Normative References . . . . . . . . . . . . . . . . . . 19
11.2. Informative References . . . . . . . . . . . . . . . . . 20
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Appendix A. Scheduled LSP information synchronization . . . . . 20
Appendix B. Contributor Addresses . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction
The Path Computation Element Protocol (PCEP) defined in [RFC5440] is
used between a Path Computation Element (PCE) and a Path Computation
Client (PCC) (or other PCE) to enable path computation of Multi-
protocol Label Switching (MPLS) Traffic Engineering Label Switched
Path (TE LSP).
Further, in order to support use cases described in [RFC8231]
specifies a set of extensions to PCEP to enable stateful control of
MPLS-TE and GMPLS LSPs via PCEP.
Traditionally, the usage and allocation of network resources,
especially bandwidth, can be supported by a Network Management System
operation such as path pre-establishment. However, this does not
provide efficient network usage since the established paths exclude
the possibility of being used by other services even when they are
not used for undertaking any service.
[I-D.ietf-teas-scheduled-resources] then provides a framework that
describes and discusses the problem and proposes an appropriate
architecture for the scheduled reservation of TE resources.
With the scheduled reservation of TE resources, it allows network
operators to reserve resources in advance according to the agreements
with their customers, and allow them to transmit data with scheduling
such as specified starting time and duration, for example for a
scheduled bulk data replication between data centers. It enables the
activation of bandwidth usage at the time the service really being
used while letting other services obtain it in spare time. The
requirement of scheduled LSP provision is mentioned in [RFC8231] and
[RFC7399], so as to provide more efficient network resource usage for
traffic engineering, which hasn't been solved yet. Also, for
deterministic networks, the scheduled LSP can provide a better
network resource usage for guaranteed links. This idea can also be
applied in segment routing to schedule the network resources over the
whole network in a centralized manner as well.
With this in mind, this document proposes a set of extensions needed
to the stateful PCE, so as to enable LSP scheduling for path
computation and LSP setup/deletion based on the actual network
resource usage duration of a traffic service. A scheduled LSP is
characterized by a starting time and a duration. When the end of the
LSP life is reached, it is deleted to free up the resources for other
LSP (scheduled or not).
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2. Conventions used in 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.
2.1. Terminology
The following terminologies are re-used from existing PCE documents.
o Active Stateful PCE [RFC8231];
o Passive Stateful PCE [RFC8231];
o Delegation [RFC8231];
o PCE-Initiated LSP [RFC8281];
o PCC [RFC5440], [RFC8231];
o PCE [RFC5440], [RFC8231];
o TE LSP [RFC5440], [RFC8231];
o TED [RFC5440], [RFC8231];
o LSP DB [RFC8231];
In addition, this document defines the following terminologies.
Scheduled TE LSP: a LSP with the scheduling attributes,that carries
traffic flow demand at a starting time and last for a certain
duration. The PCE operates path computation per LSP availability
for the required time and duration.
Scheduled LSP DB: a database of scheduled LSPs
Scheduled TED: Traffic engineering database with the awareness of
scheduled resources for TE. This database is generated by the PCE
from the information in TED and scheduled LSP DB and allows
knowing, at any time, the amount of available resources (does not
include failures in the future).
Starting time(start-time): This value indicates when the scheduled
LSP is used and the corresponding LSP must be setup and active.
In other time(i.e., before the starting time or after the starting
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time plus Duration), the LSP can be inactive to include the
possibility of the resources being used by other services.
Duration: The value indicates the time duration that the LSP is
undertaken by a traffic flow and the corresponding LSP must be
setup and active. At the end of which, the LSP is teardown and
removed from the data base.
3. Motivation and Objectives
A stateful PCE can support better efficiency by using LSP scheduling
described in the use case of [RFC8231]. This requires the PCE to
maintain the scheduled LSPs and their associated resource usage, e.g.
bandwidth for Packet-switched network, as well as have the ability to
trigger signaling for the LSP setup/tear-down at the correct time.
Note that existing configuration tools can be used for LSP
scheduling, but as highlighted in section 3.1.3 of [RFC8231] as well
as discussions in [I-D.ietf-teas-scheduled-resources], doing this as
a part of PCEP in a centralized manner, has obvious advantages.
The objective of this document is to provide a set of extensions to
PCEP to enable LSP scheduling for LSPs creation/deletion under the
stateful PCE control, according to traffic services from customers,
so as to improve the usage of network resources.
4. Architecture Overview
4.1. LSP scheduling Overview
The LSP scheduling allows PCEs and PCCs to provide scheduled LSP for
customers' traffic services at its actual usage time, so as to
improve the network resource efficient utilization.
For stateful PCE supporting LSP scheduling, there are two types of
LSP databases used in this document. One is the LSP-DB defined in
PCEP [RFC8231], while the other is the scheduled LSP database (SLSP-
DB, see section 6). The SLSP-DB records scheduled LSPs and is used
as a complementary to the TED and LSP-DB. Note that the two types of
LSP databases can be implemented in one physical database or two
different databases. This document does not state any preference
here.
Furthermore, a scheduled TED can be generated from the scheduled LSP
DB, LSP DB and TED to indicate the network links and nodes with
resource availability information for now and future. The scheduled
TED should be maintained by all PCEs within the network environment.
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In case of implementing PCC-initiated scheduled LSPs, before a PCC
delegates a scheduled LSP, it MAY use the PCReq/PCRep messages to
learn the path for the scheduled LSP. A PCC MUST delegate a
scheduled LSP with information of its scheduling parameters,
including the starting time and the duration using PCRpt message.
Since the LSP is not yet signaled, at the time of delegation the LSP
would be in down state. Upon receiving the delegation of the
scheduled LSP, a stateful PCE SHALL check the scheduled TED for the
network resource availability on network nodes and computes a path
for the LSP with the scheduling information and update to the PCC as
per the active stateful PCE techniques [RFC8231].
Note that the active stateful PCE can update to the PCC with the path
for the scheduled LSP at any time. However, the PCC should not
signal the LSP over the path once receiving these messages since the
path is not activated yet until its starting time.
For a multiple PCE environment, in order to synchronize the scheduled
LSP DB, the mechanism as described in [I-D.litkowski-pce-state-sync]
are used to synchronize between PCEs. The scheduled TED is
determined from the synchronized SLSP-DB. The PCE with delegation
for the scheduled LSP would report the scheduled LSP to other PCEs,
any future update to the scheduled LSP is also updated to other PCEs.
This way the state of all scheduled LSPs are synchronized among the
PCEs. [RFC7399] discusses some synchronization issues and
considerations, that are also applicable to the scheduled databases.
The scheduled LSP can also be initiated by PCE itself. In case of
implementing PCE-initiated scheduled LSP, the stateful PCE shall
check the network resource availability for the traffic and computes
a path for the scheduled LSP and initiate a scheduled LSP at the PCC
and synchronize the scheduled LSP to other PCEs. Note that, the PCC
could be notified immediately or at the starting time of the
scheduled LSP based on the local policy. In case of former SCHED-
LSP-ATTRIBUTE MUST be included in the message where as for the latter
SCHED-LSP-ATTRIBUTE SHOULD NOT be included.
In both modes, for activation of scheduled LSPs, the PCC could
initiate the setup of scheduled LSP at the start time by itself or
wait for the PCE to update the PCC to initiate the setup of LSP.
Similarly on the scheduling usage expires, the PCC could initiate the
removal by itself or wait for the PCE to request the removal of the
LSP. This is based on the Flag set in SCHED-LSP-ATTRIBUTE TLV. The
state of the scheduled LSP is synchronized to other PCEs using the
existing mechanism in [RFC8231] and [I-D.litkowski-pce-state-sync].
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4.2. Support of LSP Scheduling
4.2.1. LSP Scheduling
For a scheduled LSP, a user configures it with an arbitrary
scheduling duration time from Ta to time Tb, which may be represented
as [Ta, Tb].
When an LSP is configured with arbitrary scheduling duration [Ta,
Tb], a path satisfying the constraints for the LSP in the scheduling
duration is computed and the LSP along the path is set up to carry
traffic from time Ta to time Tb.
4.2.2. Periodical LSP Scheduling
In addition to LSP Scheduling at an arbitrary time period, there are
also periodical LSP Scheduling.
A periodical LSP Scheduling represents Scheduling LSP every time
interval. It has a scheduling duration such as [Ta, Tb], a number of
repeats such as 10 (repeats 10 times), and a repeat cycle/time
interval such as a week (repeats every week). The scheduling
interval: "[Ta, Tb] repeats n times with repeat cycle C" represents
n+1 scheduling intervals as follows:
[Ta, Tb], [Ta+C, Tb+C], [Ta+2C, Tb+2C], ..., [Ta+nC, Tb+nC]
When an LSP is configured with a scheduling interval such as "[Ta,
Tb] repeats 10 times with a repeat cycle a week" (representing 11
scheduling intervals), a path satisfying the constraints for the LSP
in each of the scheduling intervals represented by the periodical
scheduling interval is computed and the LSP along the path is set up
to carry traffic in each of the scheduling intervals.
4.2.2.1. Elastic Time LSP Scheduling
In addition to the basic LSP scheduling at an arbitrary time period,
another option is elastic time intervals, which is represented as
within -P and Q, where P and Q is an amount of time such as 300
seconds. P is called elastic range lower bound and Q is called
elastic range upper bound.
For a simple time interval such as [Ta, Tb] with an elastic range,
elastic time interval: "[Ta, Tb] within -P and Q" means a time period
from (Ta+X) to (Tb+X), where -P <= X <= Q. Note that both Ta and Tb
may be shifted the same X.
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When an LSP is configured with elastic time interval "[Ta, Tb] within
-P and Q", a path is computed such that the path satisfies the
constraints for the LSP in the time period from (Ta+X) to (Tb+X)
and |X| is the minimum value from 0 to max(P, Q). That is that
[Ta+X, Tb+X] is the time interval closest to time interval [Ta, Tb]
within the elastic range. The LSP along the path is set up to carry
traffic in the time period from (Ta+X) to (Tb+X).
Similarly, for a recurrent time interval with an elastic range,
elastic time interval: "[Ta, Tb] repeats n times with repeat cycle C
within -P and Q" represents n+1 simple elastic time intervals as
follows:
[Ta+X0, Tb+X0], [Ta+C+X1, Tb+C+X1], ..., [Ta+nC+Xn, Tb+nC+Xn]
where -P <= Xi <= Q, i = 0, 1, 2, ..., n.
If a user wants to keep the same repeat cycle between any two
adjacent time intervals, elastic time interval: "[Ta, Tb] repeats n
times with repeat cycle C within -P and Q SYNC" may be used, which
represents n+1 simple elastic time intervals as follows:
[Ta+X, Tb+X], [Ta+C+X, Tb+C+X], ..., [Ta+nC+X, Tb+nC+X]
where -P <= X <= Q.
4.2.2.2. Graceful Periods
Besides the stated time scheduling, a user may want to have some
graceful periods for each or some of the time intervals for the LSP.
Two graceful periods may be configured for a time interval. One is
the graceful period before the time interval, called grace-before,
which extends the lifetime of the LSP for grace-before (such as 30
seconds) before the time interval. The other is the one after the
time interval, called grace-after, which extends the lifetime of the
LSP for grace-after (such as 60 seconds) after the time interval.
When an LSP is configured with a simple time interval such as [Ta,
Tb] with graceful periods such as grace-before GB and grace-after GA,
a path is computed such that the path satisfies the constraints for
the LSP in the time period from Ta to Tb. The LSP along the path is
set up to carry traffic in the time period from (Ta-GB) to (Tb+GA).
During graceful periods from (Ta-GB) to Ta and from Tb to (Tb+GA),
the LSP is up to carry traffic (maybe in best effort).
4.3. Scheduled LSP creation
In order to realize PCC-Initiated scheduled LSP in a centralized
network environment, a PCC has to separate the setup of a LSP into
two steps. The first step is to request/delegate and get a LSP but
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not signal it over the network. The second step is to signal the
scheduled LSP over the LSRs (Labeled switched Router) at its starting
time.
For PCC-Initiated scheduled LSPs, a PCC can delegate the scheduled
LSP by sending a path computation report (PCRpt) message by including
its demanded resources with the scheduling information to a stateful
PCE. Note the PCC MAY use the PCReq/PCRep with scheduling
information before delegating.
Upon receiving the delegation via PCRpt message, the stateful PCE
computes the path for the scheduled LSP per its starting time and
duration based on the network resource availability stored in
scheduled TED (see section 4.1).
The stateful PCE will send a PCUpd message with the scheduled path
information as well as the scheduled resource information for the
scheduled LSP to the PCC. The PCE SHOULD add the scheduled LSP into
its scheduled LSP DB and update its scheduled TED. The PCE SHOULD
also synchronize to other PCEs within the network if there is any, so
as to keep their scheduling information synchronized as per
[I-D.litkowski-pce-state-sync].
For PCE-Initiated Scheduled LSP, the stateful PCE can compute a path
for the scheduled LSP per requests from network management systems
automatically based on the network resource availability in the
scheduled TED, send a PCInitiate message with the path information
back to the PCC. Based on the local policy, the PCInitiate message
could be sent immediately to ask PCC to create a scheduled LSP (as
per this document) or the PCInitiate message could be sent at the
start time to the PCC to create a normal LSP (as per [RFC8281]).
In both modes:
o The stateful PCE is required to update its local scheduled LSP DB
and scheduled TED with the scheduled LSP. Besides, it shall send
a PCRpt message with the scheduled LSP to other PCEs within the
network, so as to achieve the scheduling traffic engineering
information synchronization as per [I-D.litkowski-pce-state-sync].
o Upon receiving the PCUpd message or PCInitiate message for the
scheduled LSP from PCEs with a found path, the PCC knows that it
is a scheduled path for the LSP and does not trigger signaling for
the LSP setup on LSRs.
o The stateful PCE can update the Scheduled LSP parameters on any
network events using the PCUpd message to PCC. These changes are
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also synchronized to other PCEs as per
[I-D.litkowski-pce-state-sync].
o Based on the configuration (and the C flag in scheduled TLVs),
when it is time (i.e., at the start time) for the LSP to be set
up, either the PCC triggers the LSP to be signaled or the
delegated PCE sends a PCUpd message to the head end LSR providing
the updated path to be signaled (with A flag set to indicate LSP
activation).
4.4. Scheduled LSP Modifications
After a scheduled LSP is configured, a user may change its parameters
including the requested time as well as the bandwidth.
In PCC-Initiated case, the PCC can send a PCRpt message for the
scheduled LSP with updated parameters as well as scheduled
information included in the SCHED-LSP-ATTRIBUTE TLV (see
Section 5.2.1) or SCHED-PD-LSP-ATTRIBUTE TLV (see Section 5.2.2)
carried in the LSP Object. The PCE would take the updated resources
and schedule into considerations and update the new path for the
scheduled LSP to the PCC as well as synchronize to other PCEs in the
network. In case path cannot be set based on new requirements the
same should be conveyed by the use of empty ERO in the PCEP messages.
In PCE-Initiated case, the Stateful PCE would recompute the path
based on updated parameters as well as scheduled information. In
case it has already conveyed to the PCC this information by sending a
PCInitiate message, it should update the path and other scheduling
and resource information by sending a PCUpd message.
In any case, the scheduled databases SHALL be updated and the PCE
MUST synchronize this information to other PCEs as per
[I-D.litkowski-pce-state-sync].
4.5. Scheduled LSP activation and deletion
In PCC-Initiated case, based on the configuration (and the C flag in
scheduled TLVs), when it is time (i.e., at the start time) for the
LSP to be set up, either the PCC triggers the LSP to be signaled or
the delegated PCE sends a PCUpd message to the head end LSR providing
the updated path to be signaled (with A flag set to indicate LSP
activation). The PCC would report the status of the active LSP as
per the procedures in [RFC8231] and at this time the LSP MUST be
considered as part of the LSP-DB. The A flag MUST be set in the
scheduled TLVs to indicate that the LSP is active now. After the
scheduled duration expires, based on the C flag, the PCC triggers the
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LSP deletion on it self or the delegated PCE sends a PCUpd message to
the PCC to delete the LSP as per the procedures in [RFC8231].
In PCE-Initiated case, based on the local policy, if the scheduled
LSP is already conveyed to the PCC at the time of creation, the
handling of LSP activation and deletion is handled in the same way as
PCC-Initiated case as per the setting of C flag. In other case, the
PCE would send the PCInitiate message at the start time to the PCC to
create a normal LSP without the scheduled TLVs and remove the LSP
after the duration expires as per [RFC8281].
Additionally, the scheduled databases SHALL be updated and
synchronization to other PCEs MUST be done as per
[I-D.litkowski-pce-state-sync].
5. PCEP Objects and TLVs
5.1. Stateful PCE Capability TLV
After a TCP connection for a PCEP session has been established, a PCC
and a PCE indicates its ability to support LSP scheduling during the
PCEP session establishment phase. For a multiple-PCE environment,
the PCEs should also establish PCEP session and indicate its ability
to support LSP scheduling among PCEP peers. The Open Object in the
Open message contains the STATEFUL-PCE-CAPABILITY TLV defined in
[RFC8231]. Note that the STATEFUL- PCE-CAPABILITY TLV is defined in
[RFC8231] and updated in [RFC8281] and [RFC8232]". In this document,
we define a new flag bit B (SCHED-LSP-CAPABLITY) flag for the
STATEFUL- PCE-CAPABILITY TLV to indicate the support of LSP
scheduling and another flag bit PD (PD-LSP-CAPABLITY) to indicate the
support of LSP periodical scheduling.
B (LSP-SCHEDULING-CAPABILITY - 1 bit) [Bit Position - TBD3]: If set
to 1 by a PCC, the B Flag indicates that the PCC allows LSP
scheduling; if set to 1 by a PCE, the B Flag indicates that the
PCE is capable of LSP scheduling. The B bit MUST be set by both
PCEP peers in order to support LSP scheduling for path
computation.
PD (PD-LSP-CAPABLITY - 1 bit): [Bit Position - TBD4] If set to 1 by
a PCC, the PD Flag indicates that the PCC allows LSP scheduling
periodically; if set to 1 by a PCE, the PD Flag indicates that the
PCE is capable of periodical LSP scheduling. The PD bit MUST be
set by both PCEP peers in order to support periodical LSP
scheduling for path computation.
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5.2. LSP Object
The LSP object is defined in [RFC8231]. This document add an
optional SCHED-LSP-ATTRIBUTE TLV for normal LSP scheduling and an
optional SCHED-PD-LSP-ATTRIBUTE TLV for periodical LSP scheduling.
The presence of SCHED-LSP-ATTRIBUTE TLV in the LSP object indicates
that this LSP is requesting scheduled parameters while the SCHED-PD-
LSP-ATTRIBUTE TLV indicates that this scheduled LSP is periodical.
The scheduled LSP attribute TLV MUST be present in LSP Object for
each scheduled LSP carried in the PCEP messages. For periodical
LSPs, the SCHED-PD-LSP-ATTRIBUTE TLV can be used in LSP Object for
each periodic scheduled LSP carried in the PCEP messages.
5.2.1. SCHED-LSP-ATTRIBUTE TLV
The SCHED-LSP-ATTRIBUTE TLV can be included as an optional TLV within
the LSP object for LSP scheduling for the requesting traffic service.
This TLV SHOULD be included only if both PCEP peers have set the B
(LSP-SCHEDULING-CAPABILITY bit) in STATEFUL-PCE-CAPABILITY TLV
carried in open message.
The format of the SCHED-LSP-ATTRIBUTE 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R|C|A| Flags | Reserved (0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start-Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GrB | GrA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Elastic-Lower-Bound | Elastic-Upper-Bound |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The type of the TLV is [TBD1] and the TLV has a fixed length of 20
octets.
The fields in the format are:
Flags (8 bits): Flowing flags are defined in this document
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R (1 bit): Set to 1 to indicate the Start-Time is a relative
time, which is relative to the current time; set to 0 to
indicate the the Start-Time is an absolute time.
C (1 bit): Set to 1 to indicate the PCC is responsible to setup
and remove the scheduled LSP based on the Start-Time and
duration.
A (1 bit): Set to 1 to indicate the scheduled LSP has been
activated and should be considered as part of LSP-DB (instead
of Scheduled LSP-DB).
Reserved (24 bits): This field MUST be set to zero on transmission
and MUST be ignored on receipt.
Start-Time (32 bits): This value in seconds, indicates when the
scheduled LSP is used to carry traffic and the corresponding LSP
must be setup and activated.
Duration (32 bits): The value in seconds, indicates the duration
that the LSP is undertaken by a traffic flow and the corresponding
LSP must be up to carry traffic. At the expiry of this duration,
the LSP is tear down and deleted.
The Start-Time indicates a calendar time (e.g.,2018/12/13 8:29:58),
at or before which the scheduled LSP must be set up. The value of
the Start-Time represents the number of seconds since 00:00 hours,Jan
1, 1970 UTC when R bit is set to 0. When R bit is set to 1, it
represents the number of seconds from the current time.
In addition, it contains an non zero grace-before and grace-after if
graceful periods are configured. It includes an non zero elastic
range lower bound and upper bound if there is an elastic range
configured.
o GrB (Grace-Before -16 bits): The graceful period time length in
seconds before the starting time.
o GrA (Grace-After -16 bits): The graceful period time length in
seconds after time interval [starting time, starting time +
duration].
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o Elastic-Lower-Bound (16 bits): The maximum amount of time in
seconds that time interval can shift to lower/left.
o Elastic-Upper-Bound (16 bits): The maximum amount of time in
seconds that time interval can shift to upper/right.
5.2.2. SCHED-PD-LSP-ATTRIBUTE TLV
The periodical LSP is a special case of LSP scheduling. The traffic
service happens in a series of repeated time intervals. The SCHED-
PD-LSP-ATTRIBUTE TLV can be included as an optional TLV within the
LSP object for this periodical LSP scheduling.
This TLV SHOULD be included only if both PCEP peers have set the B
(LSP-SCHEDULING-CAPABILITY bit) and PD (PD-LSP-CAPABLITY bit) in
STATEFUL-PCE-CAPABILITY TLV carried in open message.
The format of the SCHED-PD-LSP-ATTRIBUTE 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 (TBD2) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R|C|A| Flags | Opt | NR | Reserved (0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start-Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Repeat-time-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GrB | GrA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Elastic-Lower-Bound | Elastic-Upper-Bound |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The type of the TLV is [TBD2] and the TLV has a fixed length of 24
octets. The description, format and meaning of the Flags (R, C and A
bit), Start-Time, Duration, GrB, GrA, Elastic-Lower-Bound and
Elastic-Upper-Bound fields remains same as SCHED-LSP-ATTRIBUTE TLV.
The following fields are new :
Opt: (4 bits) Indicates options to repeat.
Options = 1: repeat every day;
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Options = 2: repeat every week;
Options = 3: repeat every month;
Options = 4: repeat every year;
Options = 5: repeat every Repeat-time-length.
NR:(4 bits) The number of repeats. In each of repeats, LSP carries
traffic. If value is set to 0xFFFF, it indicates forever.
Reserved (16 bits): This field MUST be set to zero on transmission
and MUST be ignored on receipt.
Repeat-time-length:(32 bits) The time length in seconds after which
LSP starts to carry traffic again for the Duration.
6. The PCEP Messages
6.1. The PCRpt Message
Path Computation State Report (PCRpt) is a PCEP message sent by a PCC
to a PCE to report the status of one or more LSPs as per [RFC8231].
Each LSP State Report in a PCRpt message MAY contain the actual LSP's
path, bandwidth, operational and administrative status, etc. An LSP
Status Report carried on a PCRpt message is also used in delegation
or revocation of control of an LSP to/from a PCE. In case of
scheduled LSP, the scheduled TLVs MUST be carried in the LSP object
and the ERO conveys the intended path for the scheduled LSP. The
scheduled LSP MUST be delegated to a PCE. This message is also used
to synchronize the scheduled LSPs to other PCE as described in
[I-D.litkowski-pce-state-sync].
6.2. The PCUpd Message
Path Computation Update Request (PCUpd) is a PCEP message sent by a
PCE to a PCC to update LSP parameters, on one or more LSPs as per
[RFC8231]. Each LSP Update Request on a PCUpd message MUST contain
all LSP parameters that a PCE wishes to be set for a given LSP. In
case of scheduled LSP, the scheduled TLVs MUST be carried in the LSP
object and the ERO conveys the intended path for the scheduled LSP.
In case no path can be found, an empty ERO is used. The A bit is
used in PCUpd message to indicate the activation of the scheduled LSP
in case the PCE is responsible for the activation (as per the C bit).
This message is also used to synchronize the scheduled LSPs to other
PCE as described in [I-D.litkowski-pce-state-sync].
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6.3. The PCInitiate Message
An LSP Initiate Request (PCInitiate) message is a PCEP message sent
by a PCE to a PCC to trigger LSP instantiation or deletion as per
[RFC8281]. In case of scheduled LSP, based on the local policy, PCE
MAY convey the scheduled LSP to the PCC by including the scheduled
TLVs in the LSP object. Or the PCE would initiate the LSP only at
the start time of the scheduled LSP as per the [RFC8281] without the
use of scheduled TLVs.
6.4. The PCReq message
The Path Computation Request (PCReq) message is a PCEP message sent
by a PCC to a PCE to request a path computation [RFC5440] and it MAY
contain the LSP object to identify the LSP for which the path
computation is requested. In case of scheduled LSP, the scheduled
TLVs MUST be carried in the LSP object in PCReq message to request
the path computation based on scheduled TED and LSP-DB. A PCC MAY
use PCReq message to obtain the scheduled path before delegating the
LSP.
6.5. The PCRep Message
The Path Computation Reply (PCRep) message is a PCEP message sent by
a PCE to a PCC in reply to a path computation request [RFC5440]. A
PCRep message can contain either a set of computed paths if the
request can be satisfied, or a negative reply if not. The negative
reply may indicate the reason why no path could be found. In case of
scheduled LSP, the scheduled TLVs MUST be carried in the LSP object
in PCRep message to indicate the path computation based on scheduled
TED and LSP-DB. A PCC and PCE MAY use PCReq and PCRep message to
obtain the scheduled path before delegating the LSP.
6.6. The PCErr Message
[Editor's Note - Error Handling will be taken up in the next revision
of the draft]
7. Security Considerations
This document defines LSP-SCHEDULING-CAPABILITY TLV and SCHED- LSP-
ATTRIBUTE TLV which does not add any new security concerns beyond
those discussed in [RFC5440] and [RFC8231]. But in some deployments
the scheduling information could provide details about the network
operations that could be deemed as extra sensitive. Additionally,
snooping of PCEP messages with such data or using PCEP messages for
network reconnaissance may give an attacker sensitive information
about the operations of the network. Thus, such deployment should
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employ suitable PCEP security mechanisms like TCP Authentication
Option (TCP-AO) [RFC5925] or [RFC8253]. The procedure based on
Transport Layer Security (TLS) in [RFC8253] is considered a security
enhancement and thus is much better suited for the sensitive service-
aware information.
8. Manageability Consideration
8.1. Control of Function and Policy
The LSP-Scheduling feature MUST BE controlled per tunnel by the
active stateful PCE, the values for parameters like starting time,
duration SHOULD BE configurable by customer applications and based on
the local policy at PCE.
8.2. Information and Data Models
An implementation SHOULD allow the operator to view the capability
defined in this document. To serve this purpose, the PCEP YANG
module [I-D.ietf-pce-pcep-yang] could be extended.
8.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in [RFC5440].
8.4. Verify Correct Operations
Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in
[RFC5440].
8.5. Requirements On Other Protocols
Mechanisms defined in this document do not imply any new requirements
on other protocols.
8.6. Impact On Network Operations
Mechanisms defined in this document do not have any impact on network
operations in addition to those already listed in [RFC5440].
9. IANA Considerations
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9.1. PCEP TLV Type Indicators
This document defines the following new PCEP TLV. IANA maintains a
sub-registry "PCEP TLV Type Indicators" in the "Path Computation
Element Protocol (PCEP) Numbers" registry. IANA is requested to make
the following allocations from this sub-registry.
Value Meaning Reference
TBD1 SCHED-LSP-ATTRIBUTE This document
TBD2 SCHED-PD-LSP-ATTRIBUTE This document
9.2. STATEFUL-PCE-CAPABILITY TLV Flag field
This document defines new bits in the Flags field in the STATEFUL-
PCE-CAPABILITY TLV in the OPEN object. IANA maintains a sub-registry
"STATEFUL-PCE-CAPABILITY TLV Flag Field" in the "Path Computation
Element Protocol (PCEP) Numbers" registry. IANA is requested to make
the following allocations from this sub-registry.
The following values are defined in this document:
Bit Description Reference
TBD3 LSP-SCHEDULING-CAPABILITY (B-bit) This document
TBD4 PD-LSP-CAPABLITY (PD-bit) This document
9.3. Schedule TLVs Flag Field
IANA is requested to create a new sub-registry, named "Schedule TLVs
Flag Field", within the "Path Computation Element Protocol (PCEP)
Numbers" registry to manage the Flag field in the SCHED-LSP-ATTRIBUTE
and SCHED-PD-LSP-ATTRIBUTE TLVs. New values are assigned by
Standards Action [RFC8126]. Each bit should be tracked with the
following qualities:
o Bit number (counting from bit 0 as the most significant bit)
o Capability description
o Defining RFC
The following values are defined in this document:
Bit Description Reference
0 R-bit This document
1 C-bit This document
2 A-bit This document
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10. Acknowledgments
The authors of this document would also like to thank Rafal Szarecki,
Adrian Farrel, Cyril Margaria for the review and comments.
11. References
11.1. Normative References
[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>.
[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>.
[RFC8232] 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", RFC 8232,
DOI 10.17487/RFC8232, September 2017,
<https://www.rfc-editor.org/info/rfc8232>.
[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>.
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11.2. Informative References
[I-D.ietf-pce-pcep-yang]
Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A
YANG Data Model for Path Computation Element
Communications Protocol (PCEP)", draft-ietf-pce-pcep-
yang-06 (work in progress), January 2018.
[I-D.ietf-teas-scheduled-resources]
Zhuangyan, Z., Wu, Q., Chen, H., and A. Farrel, "Framework
for Scheduled Use of Resources", draft-ietf-teas-
scheduled-resources-06 (work in progress), February 2018.
[I-D.litkowski-pce-state-sync]
Litkowski, S., Sivabalan, S., and D. Dhody, "Inter
Stateful Path Computation Element communication
procedures", draft-litkowski-pce-state-sync-02 (work in
progress), August 2017.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <https://www.rfc-editor.org/info/rfc5925>.
[RFC7399] Farrel, A. and D. King, "Unanswered Questions in the Path
Computation Element Architecture", RFC 7399,
DOI 10.17487/RFC7399, October 2014,
<https://www.rfc-editor.org/info/rfc7399>.
[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>.
Appendix A. Scheduled LSP information synchronization
As for a stateful PCE, it maintains a database of LSPs (LSP-DB) that
are active in the network, so as to reveal the available network
resources and place new LSPs more cleverly.
With the scheduled LSPs, they are not activated while creation, but
should be considered when operating future path computation. Hence,
a scheduled LSP Database (SLSP-DB) is suggested to maintain all
scheduled LSP information.
The information of SLSP-DB MUST be shared and synchronized among all
PCEs within the centralized network by using PCRpt and PCUpd message
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with scheduled LSP information as per the mechanism described in
[I-D.litkowski-pce-state-sync].
The PCE should generate and maintain a scheduled TED based on LSP DB,
scheduled LSP DB and TED, which is used to indicate the network
resource availability on network nodes for LSP path computation.
Appendix B. Contributor Addresses
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Xufeng Liu
Ericsson
USA
Email: xliu@kuatrotech.com
Mehmet Toy
Verizon
USA
Email: mehmet.toy@verizon.com
Vic Liu
China Mobile
No.32 Xuanwumen West Street, Xicheng District
Beijing, 100053
China
Email: liu.cmri@gmail.com
Lei Liu
Fujitsu
USA
Email: lliu@us.fujitsu.com
Khuzema Pithewan
Infinera
Email: kpithewan@infinera.com
Zitao Wang
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: wangzitao@huawei.com
Xian Zhang
Huawei Technologies
Research Area F3-1B,
Huawei Industrial Base,
Shenzhen, 518129, China
Email: zhang.xian@huawei.com
Authors' Addresses
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Huaimo Chen (editor)
Huawei
Boston, MA
USA
Email: huaimo.chen@huawei.com
Yan Zhuang (editor)
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: zhuangyan.zhuang@huawei.com
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: bill.wu@huawei.com
Dhruv Dhody (editor)
Huawei
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: dhruv.ietf@gmail.com
Daniele Ceccarelli
Ericsson
Via A. Negrone 1/A
Genova - Sestri Ponente
Italy
Email: daniele.ceccarelli@ericsson.com
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