PCEP Extension for DetNet Bounded Latency
draft-xiong-pce-detnet-bounded-latency-01
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| Authors | Quan Xiong , Peng Liu | ||
| Last updated | 2022-10-09 | ||
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draft-xiong-pce-detnet-bounded-latency-01
PCE Q. Xiong, Ed.
Internet-Draft ZTE Corporation
Intended status: Standards Track P. Liu
Expires: 12 April 2023 China Mobile
9 October 2022
PCEP Extension for DetNet Bounded Latency
draft-xiong-pce-detnet-bounded-latency-01
Abstract
In certain networks, such as Deterministic Networking (DetNet), it is
required to consider the bounded latency for path selection. This
document describes the extensions to PCEP to carry deterministic
latency constraints and distribute deterministic paths for end-to-end
path computation in DetNet service.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 12 April 2023.
Copyright Notice
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document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. METRIC Object . . . . . . . . . . . . . . . . . . . . . . 3
3.1.1. End-to-End Bounded Delay Metric . . . . . . . . . . . 3
3.1.2. End-to-End Bounded Jitter Metric . . . . . . . . . . 4
3.2. LSP Object . . . . . . . . . . . . . . . . . . . . . . . 5
3.3. Deterministic Path Object . . . . . . . . . . . . . . . . 5
3.3.1. Deadline Sub-TLV . . . . . . . . . . . . . . . . . . 6
3.3.2. Cycle Sub-TLV . . . . . . . . . . . . . . . . . . . . 7
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
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). PCEP Extensions for the Stateful PCE Model
[RFC8231] describes a set of extensions to PCEP to enable active
control of MPLS-TE and Generalized MPLS (GMPLS) tunnels. As depicted
in [RFC4655], a PCE MUST be able to compute the path of a TE LSP by
operating on the TED and considering bandwidth and other constraints
applicable to the TE LSP service request. The constraint parameters
are provided such as metric, bandwidth, delay, affinity, etc.
However these parameters can't meet the DetNet requirements.
According to [RFC8655], Deterministic Networking (DetNet) operates at
the IP layer and delivers service which provides extremely low data
loss rates and bounded latency within a network domain. The bounded
latency indicates the minimum and maximum end-to-end latency from
source to destination and bounded jitter (packet delay variation).
[I-D.xiong-detnet-large-scale-enhancements] has proposed the packet
treatment which should support new functions such as queuing
mechanisms to ensure the deterministic latency. The computing method
of end-to-end delay bounds is defined in
[I-D.ietf-detnet-bounded-latency]. It is the sum of the 6 delays in
DetNet bounded latency model. And these delays should be measured
and ccollected, but the related mechanisms are out of this document.
The end-to-end delay bounds can also be computed as the sum of non
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queuing delay bound and queuing delay bound along the path. The
upper bounds of non queuing delay are constant and depend on the
specific network and the value of queuing delay bound depends on the
queuing mechanisms deployed along the path.
As per [I-D.ietf-detnet-controller-plane-framework], explicit path
should be calculated and established in control plane to guarantee
the deterministic transimission. When the PCE is deployed, the path
computation should be applicable for DetNet networks. It is required
that bounded latency including minimum and maximum end-to-end latency
and bounded delay variation are considered during the deterministic
path selection for PCE. The bounded latency constriants should be
extended for PCEP. Moreover, the information along the deterministic
path should be provided to the PCC after the path conputation such as
queuing parameters.
This document describes the extensions to PCEP to carry deterministic
latency constraints and distribute deterministic paths for end-to-end
path computation in DetNet service.
1.1. 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 RFC 2119 [RFC2119].
2. Terminology
The terminology is defined as [RFC8655] and [RFC5440].
3. PCEP Extensions
3.1. METRIC Object
The METRIC object is defined in Section 7.8 of [RFC5440], comprising
metric-value and metric-type (T field), and a flags field, comprising
a number of bit flags (B bit and C bit). This document defines two
types for the METRIC object.
3.1.1. End-to-End Bounded Delay Metric
[RFC8233] has proposed the Path Delay metric type of the METRIC
object to represent the sum of the Link Delay metric of all links
along a P2P path. This document proposes the End-to-End Bounded
Delay metric in PCEP to represent the sum of Output delay, Link
delay, Frame preemption delay, Processing delay, Regulation delay and
Queuing delay as defined in [I-D.ietf-detnet-bounded-latency] along a
deterministic path. Or the End-to-End Bounded Delay metric can be
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encoded as the sum of non queuing delay bound and queuing delay bound
along the deterministic path. The extensions for End-to-End Bounded
Delay Metric are as following shown:
* T=TBD1: End-to-End Bounded Delay Metric.
* The value of End-to-End Bounded Delay Metric is the encoding in
units of microseconds with 32 bits.
* The B bit MUST be set to suggest a maximum bound for the end-to-
end delay of deterministic path. The end-to-end delay must be
less than or equal to the value.
A PCC MAY use the End-to-End Bounded Latency metric in a Path
Computation Request (PCReq) message to request a deterministic path
meeting the end-to-end latency requirement. A PCE MAY use the End-
to-End Bounded Latency metric in a Path Computation Reply (PCRep)
message along with a NO-PATH object in the case where the PCE cannot
compute a path meeting this constraint. A PCE can also use this
metric to send the computed end-to-end bounded latency to the PCC.
3.1.2. End-to-End Bounded Jitter Metric
[RFC8233] has proposed the Path Delay Variation metric type of the
METRIC object to represent the sum of the Link Delay Variation metric
of all links along the path. This document proposes the End-to-end
Bounded Jitter metric in PCEP to represent the difference between the
end-to-end upper bounded latecny and the end-to-end lower bounded
latecny along a deterministic path. The extensions for End-to-End
Bounded Jitter Metric are as following shown:
* T=TBD2: End-to-End Bounded Jitter Metric.
* The value of End-to-End Bounded Jitter Metric is the encoding in
units of microseconds with 32 bits.
* The B bit MUST be set to suggest a maximum bound for the end-to-
end jitter of deterministic path. The end-to-end jitter must be
less than or equal to the value.
A PCC MAY use the End-to-End Bounded Jitter metric in a PCReq message
to request a deterministic path meeting the end-to-end delay
variation requirement. A PCE MAY use the End-to-End Bounded Jitter
metric in a PCRep message along with a NO-PATH object in the case
where the PCE cannot compute a path meeting this constraint. A PCE
can also use this metric to send the computed end-to-end bounded
Jitter to the PCC.
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3.2. LSP Object
The LSP Object is defined in Section 7.3 of [RFC8231]. This document
defiend a new flag (D-flag) to present the deterministic path for the
LSP-EXTENDED-FLAG TLV carried in LSP Object as defined in
[I-D.ietf-pce-lsp-extended-flags].
D (Request for Deterministic Path) : If the bit is set to 1, it
indicates that the PCC requests PCE to compute the deterministic
path. A PCE would also set this bit to 1 to indicate that the
deterministic path is included by PCE and encoded in the PCRep, PCUpd
or PCInitiate message.
3.3. Deterministic Path Object
The Explicit Route Object (ERO) is defined in [RFC5440] to encode the
path of a TE LSP through the network. SR-ERO subobject is used for
SR-TE path which consists of one or more SIDs as defined in
[RFC8664]. SRV6-ERO subobject is used for SRv6 path as defined in
[I-D.ietf-pce-segment-routing-ipv6].
As defined in [I-D.ietf-detnet-bounded-latency], the end-to-end delay
bounds can be presented as the sum of non queuing delay bound and
queuing delay bound along the path. The upper bounds of non queuing
delay are constant and depend on the specific network, but the value
of queuing delay bound depends on the queuing mechanisms deployed
along the deterministic path. So to meet the requirements of the
end-to-end delay, the PCE should select a queuing mechanism and
configure the related parameters to the PCC. This document defines
Deterministic Path Object (DPO) to distribute the deterministic
latency information through DetNet networks.
DPO Object-Class is TBD3.
DPO Object-Type is TBD4.
The format of the DPO object body is 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Deterministic Latency Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Deterministic Latency Information sub-TLV(variable) (optional)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Figure 1: DPO Object Format
Deterministic Latency Type (16bits): indicates the type of queuing
algorithm and each type represents the corresponding queuing
mechanisms. The type can be defined refer to the queuing mechanisms
which have been discussed such as [I-D.ietf-detnet-bounded-latency].
More types can be defined due to the new queuing mechanisms.
1: indicates the Time Aware Shaping [IIEEE802.1Qbv].
2: indicates the Credit-Based Shaper[IEEE802.1Q-2014].
3: indicates the Asynchronous Traffic Shaping [IEEE802.1Qcr].
4: indicates the Cyclic Queuing and Forwarding [IEEE802.1Qch].
5: indicates the Deadline Based Forwarding
[I-D.peng-detnet-deadline-based-forwarding] and [I-D.stein-srtsn].
6: indicates the Multiple Cyclic Buffers Queuing Mechanism
[I-D.dang-queuing-with-multiple-cyclic-buffers].
7: indicates the ADN mechanism defined in
[I-D.joung-detnet-asynch-detnet-framework].
Deterministic Latency Infomation Sub-TLV (variable): indicuates the
corresponding Deterministic Latency Parameters. The current Sub-TLVs
including Deadline Sub-TLV and Cycle Sub-TLV are proposed as
following sections.
3.3.1. Deadline Sub-TLV
Deadline Sub-TLV is optional for the Queuing Information Structure.
The deadline-based queue mechanism has been proposed in [draft-stein-
srtsn] and [I-D.peng-detnet-deadline-based-forwarding]. The
deadlines along the path should be computed at PCE and configured to
the PCC, and then inserted into the packet headers. When the Queuing
Algorithm Type is set to indicate the deadline-based queuing
mechanisms, the Deadline Sub-TLV should be used to carry the deadline
parameters.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Deadline |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Deadline Sub-TLV
Type (16bits): TBD3, indicates the type of Deadline Sub-TLV.
Length (16bits): indicated the length of Deadline Sub-TLV.
Deadline (32bits): indicates the deadline time for a node to forward
a DetNet flow.
3.3.2. Cycle Sub-TLV
Cycle Sub-TLV is optional for the Queuing Information Structure. The
cyclic-based queue mechanism has been proposed in [IEEE802.1Qch] and
improved in [draft-dang-queuing-with-multiple-cyclic-buffers]. The
clycle along the path should be computed at PCE and configured to the
PCC, and then inserted into the packet headers. When the Queuing
Algorithm Type is set to indicate the cycle-based queuing mechanisms,
the Cycle Sub-TLV should be used to carry the cycle parameters.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cycle Profile ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cycle ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Cycle Sub-TLV
Type (16bits): TBD4, indicates the type of Cycle Sub-TLV.
Length (16bits): indicated the length of Cycle Sub-TLV.
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Cycle Profile ID (32bits): indicates the profile ID which the cyclic
queue applied at a node.
Cycle ID (32bits): indicates the Cycle ID for a node to forward a
DetNet flow.
4. Acknowledgements
TBA
5. IANA Considerations
TBA
6. Security Considerations
TBA
7. References
7.1. Normative References
[I-D.dang-queuing-with-multiple-cyclic-buffers]
Liu, B. and J. Dang, "A Queuing Mechanism with Multiple
Cyclic Buffers", Work in Progress, Internet-Draft, draft-
dang-queuing-with-multiple-cyclic-buffers-00, 22 February
2021, <https://www.ietf.org/archive/id/draft-dang-queuing-
with-multiple-cyclic-buffers-00.txt>.
[I-D.ietf-detnet-bounded-latency]
Finn, N., Boudec, J. L., Mohammadpour, E., Zhang, J., and
B. Varga, "DetNet Bounded Latency", Work in Progress,
Internet-Draft, draft-ietf-detnet-bounded-latency-10, 8
April 2022, <https://www.ietf.org/archive/id/draft-ietf-
detnet-bounded-latency-10.txt>.
[I-D.ietf-detnet-controller-plane-framework]
Malis, A. G., Geng, X., Chen, M. (., Qin, F., and B.
Varga, "Deterministic Networking (DetNet) Controller Plane
Framework", Work in Progress, Internet-Draft, draft-ietf-
detnet-controller-plane-framework-02, 28 June 2022,
<https://www.ietf.org/archive/id/draft-ietf-detnet-
controller-plane-framework-02.txt>.
[I-D.ietf-pce-lsp-extended-flags]
"LSP Extended Flags", July 2021, <https://www.rfc-
editor.org/info/draft-ietf-pce-lsp-extended-flags>.
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[I-D.ietf-pce-segment-routing-ipv6]
Li(Editor), C., Negi, M. S., Sivabalan, S., Koldychev, M.,
Kaladharan, P., and Y. Zhu, "Path Computation Element
Communication Protocol (PCEP) Extensions for Segment
Routing leveraging the IPv6 dataplane", Work in Progress,
Internet-Draft, draft-ietf-pce-segment-routing-ipv6-14, 10
July 2022, <https://www.ietf.org/archive/id/draft-ietf-
pce-segment-routing-ipv6-14.txt>.
[I-D.joung-detnet-asynch-detnet-framework]
Joung, J., Ryoo, J., Cheung, T., Li, Y., and P. Liu,
"Asynchronous Deterministic Networking Framework for
Large-Scale Networks", Work in Progress, Internet-Draft,
draft-joung-detnet-asynch-detnet-framework-00, 26 June
2022, <https://www.ietf.org/archive/id/draft-joung-detnet-
asynch-detnet-framework-00.txt>.
[I-D.peng-6man-deadline-option]
Peng, S. and B. Tan, "Deadline Option", Work in Progress,
Internet-Draft, draft-peng-6man-deadline-option-00, 11
January 2022, <https://www.ietf.org/archive/id/draft-peng-
6man-deadline-option-00.txt>.
[I-D.peng-detnet-deadline-based-forwarding]
Peng, S., Tan, B., and P. Liu, "Deadline Based
Deterministic Forwarding", Work in Progress, Internet-
Draft, draft-peng-detnet-deadline-based-forwarding-01, 1
March 2022, <https://www.ietf.org/archive/id/draft-peng-
detnet-deadline-based-forwarding-01.txt>.
[I-D.stein-srtsn]
Stein, Y. (., "Segment Routed Time Sensitive Networking",
Work in Progress, Internet-Draft, draft-stein-srtsn-01, 29
August 2021, <https://www.ietf.org/archive/id/draft-stein-
srtsn-01.txt>.
[I-D.xiong-detnet-large-scale-enhancements]
Xiong, Q. and Z. Du, "DetNet Enhancements for Large-Scale
Deterministic Networks", Work in Progress, Internet-Draft,
draft-xiong-detnet-large-scale-enhancements-00, 24
February 2022, <https://www.ietf.org/archive/id/draft-
xiong-detnet-large-scale-enhancements-00.txt>.
[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>.
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[RFC4655] "A Path Computation Element (PCE)-Based Architecture",
August 2006, <https://www.rfc-editor.org/info/RFC4655>.
[RFC4915] "Multi-Topology (MT) Routing in OSPF", June 2007,
<https://www.rfc-editor.org/info/RFC4915>.
[RFC5120] "M-ISIS: Multi Topology (MT) Routing in Intermediate
System to Intermediate Systems (IS-ISs)", February 2008,
<https://www.rfc-editor.org/info/RFC5120>.
[RFC5440] "Path Computation Element (PCE) Communication Protocol
(PCEP)", March 2009,
<https://www.rfc-editor.org/info/RFC5440>.
[RFC6549] "OSPFv2 Multi-Instance Extensions", March 2012,
<https://www.rfc-editor.org/info/RFC6549>.
[RFC7752] "North-Bound Distribution of Link-State and Traffic
Engineering (TE) Information Using BGP", March 2016,
<https://www.rfc-editor.org/info/RFC7752>.
[RFC8174] "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key
Words", May 2017,
<https://www.rfc-editor.org/info/RFC8174>.
[RFC8231] "Path Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", September 2017,
<https://www.rfc-editor.org/info/RFC8231>.
[RFC8233] Dhody, D., Wu, Q., Manral, V., Ali, Z., and K. Kumaki,
"Extensions to the Path Computation Element Communication
Protocol (PCEP) to Compute Service-Aware Label Switched
Paths (LSPs)", RFC 8233, DOI 10.17487/RFC8233, September
2017, <https://www.rfc-editor.org/info/rfc8233>.
[RFC8655] "DetNet Architecture", June 2017,
<https://www.rfc-editor.org/info/RFC8655>.
[RFC8664] "SR-PCE", August 2020,
<https://www.rfc-editor.org/info/RFC8664>.
Authors' Addresses
Quan Xiong (editor)
ZTE Corporation
China
Email: xiong.quan@zte.com.cn
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Peng Liu
China Mobile
Beijing
China
Email: liupengyjy@chinamobile.com
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