Internet DRAFT - draft-tan-pce-detnet-high-reliability
draft-tan-pce-detnet-high-reliability
pce Working Group R. Tan
Internet-Draft T. Zhou
Intended status: Standards Track Huawei
Expires: 16 July 2023 12 January 2023
PCEP Extension for DetNet High Reliability
draft-tan-pce-detnet-high-reliability-00
Abstract
Real-time network performance information, like latency, delay
variation, packet loss and in order delivery, is becoming critical in
the path computation in some networks.
This document propose metric extensions to PCEP messages, to better
describe the path computation constraints and QoS requirements of
Deterministic Networking (DetNet) flows, especially the high
reliability requirements on packet loss and in order delivery.
PCEP Extensions defined in this document could be used not only for
DetNet, but also for other PCEP scenarios.
Status of This Memo
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This Internet-Draft will expire on 16 July 2023.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. PCEP Extenstions . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Extensions to METRIC Object . . . . . . . . . . . . . . . 3
2.1.1. End-to-End Loss Metric . . . . . . . . . . . . . . . 3
2.1.2. Consecutive Loss Metric . . . . . . . . . . . . . . . 4
2.1.3. Misordering Metric . . . . . . . . . . . . . . . . . 4
2.1.4. Metric Flags . . . . . . . . . . . . . . . . . . . . 4
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Normative References . . . . . . . . . . . . . . . . . . 5
5.2. Informative References . . . . . . . . . . . . . . . . . 6
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
[RFC5440] specifies the Path Computation Element Protocol (PCEP) for
communications between a PCC and a PCE. [RFC8231] describes a set of
extensions to PCEP to enable stateful control of MPLS-TE and GMPLS
LSPs via PCEP.
[RFC8655] provides the overall architecture for Deterministic
Networking (DetNet), and specifies the primary goals of DetNet QoS,
which can be expressed in terms of minimum and maximum end-to-end
latency from source to destination, timely delivery, bounded jitter,
packet loss ratio of the nodes and links, and an upper bound on out-
of-order packet delivery. It is important that the QoS requirements
be met when computing path for DetNet flows.
[I-D.ietf-detnet-controller-plane-framework] provides a framework
overview for the DetNet controller plane. The DetNet control plane
model could be distributed, fully centralized or hybrid. In
centralized control plane model, PCEP could be used as a
communication protocol between the controller and DetNet nodes.
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1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
1.2. Terminology
The abbreviations used in this document are:
PCC: Path Computation Client; any client application requesting a
path computation to be performed by a Path Computation Element.
PCE: Path Computation Element; an entity (component, application, or
network node) that is capable of computing a network path or route
based on a network graph and applying computational constraints.
PCEP: Path Computation Element Protocol; a protocol for
communications between a PCC and a PCE.
DetNet: Deterministic Networking
2. PCEP Extenstions
2.1. Extensions to METRIC Object
[RFC5440] defines METRIC Object to indicate an optimization or bound
constraint on the path cost when computing path for Label Switched
Lsps (LSPs). [RFC8233] defines the extension to PCEP METRIC object
to carry latency, delay variation, packet loss as constraints for
path computation. This document propose three new metric type, and
two bit flags.
2.1.1. End-to-End Loss Metric
All though path loss metric type (T=14) was defined in [RFC8233], the
corresponding matric value of METRIC Object is described as the sum
of "Unidirectional Link Loss" along the path, which does not count in
the packet loss arises in the nodes along the path.
This document propose a new metric type, end-to-end loss metric,
which counts in both link and node loss along the path. It could
describe the end-to-end packet loss metric more precisely. It
expresses the maximum Packet Loss Rate (PLR) requirement for the
DetNet flow between the Ingress and Egress(es).
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Metric Type T=TBD1: End-to-End Loss metric
PCCs MAY use this METRIC object in PCReq/PCRpt messages to carry end-
to-end packet loss metric constraint for path computation; PCEs MAY
use this METRIC object in PCRep/PCInitiate/PCUpd messages to express
the computed value of end-to-end packet loss metric of the computed
path.
2.1.2. Consecutive Loss Metric
As per [RFC9016], consecutive packet loss tolerance in a certain
period could be considered as constraint when computing path for
DetNet flows. This document specifies a new metric type, Consecutive
Loss, to describe the consecutive packet loss along the path.
Metric Type T=TBD2: Consecutive Loss metric
PCCs MAY use this METRIC object in PCReq/PCRpt messages to carry
consecutive packet loss metric constraint for path computation; PCEs
MAY use this METRIC object in PCRep/PCInitiate/PCUpd messages to
express the computed value of consecutive packet loss metric of the
computed path.
2.1.3. Misordering Metric
As per [RFC8655], packet misordering should be considered as
constraint when computing path for DetNet flows. This document
specifies a new metric type, Misordering tolerance, to describe the
misordering packets counts along the path.
Metric Type T=TBD3: Misordering metric
PCCs MAY use this METRIC object in PCReq/PCRpt messages to carry
packet misordering metric constraint for path computation; PCEs MAY
use this METRIC object in PCRep/PCInitiate/PCUpd messages to express
the computed value of packet misordering metric of the computed path.
2.1.4. Metric Flags
As per [RFC5440], a "Flags" field (8 bits) is defined in METRIC
Object. The flags filed is comprised of several bit flags, currently
B (Bound) and C (Computed) bits have been defined.
2.1.4.1. Low Bound
As per [RFC5440], an abstract B bit flag was defined in METRIC
Object, and in most case it describes the up bound value of the
corresponding metric type.
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As per [RFC8655], both minimum and maximum end-to-end latency could
be used to express the QoS requirements of DetNet flows.
This document propose a new bit, Low Bound, which is defined in Flags
field of METRIC Object, to specify that the metric value is a low
bound constraint.
L bit: Low bound of a metric type
PCCs MAY use L bit flag of METRIC object in PCReq/PCRpt messages to
request a path that the metric value of the path MUST be larger or
equal to the value specified in related METRIC object.
2.1.4.2. Margin
In some DetNet scenario, allowance methods could be used to mitigate
the negative impact caused by rapid value variations of certain
metric of DetNet nodes and links.
This document propose a new bit, Margin, which is defined in Flags
field of METRIC Object, to describe that the metric value is a margin
value.
M bit: Margin of a metric type
A METRIC object with M bit set MAY be used along with another METRIC
object with the same metric type and B or L bit set. PCCs MAY use M
bit flag of METRIC object in PCReq/PCRpt messages to express the
requirement that a margin of the metric value specified in the METRIC
object with M bit set could be tolerated when computing a path.
3. IANA Considerations
TBD.
4. Security Considerations
The security considerations described in [RFC5440] and [RFC8655]
apply to the extensions defined in this document as well. This
document does not raise new security issues.
5. References
5.1. Normative References
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[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>.
[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>.
[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] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
[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>.
[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>.
5.2. Informative References
[RFC9016] Varga, B., Farkas, J., Cummings, R., Jiang, Y., and D.
Fedyk, "Flow and Service Information Model for
Deterministic Networking (DetNet)", RFC 9016,
DOI 10.17487/RFC9016, March 2021,
<https://www.rfc-editor.org/info/rfc9016>.
[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-03, 30 December 2022,
<https://www.ietf.org/archive/id/draft-ietf-detnet-
controller-plane-framework-03.txt>.
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Acknowledgements
Authors' Addresses
Ren Tan
Huawei
China
Email: tanren@huawei.com
Tianran Zhou
Huawei
China
Email: zhoutianran@huawei.com
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