MPLS Working Group X. Song
Internet-Draft Q. Xiong
Intended status: Standards Track ZTE Corp.
Expires: 30 November 2024 R. Gandhi
Cisco Systems, Inc.
29 May 2024
MPLS Network Action for Deterministic Latency
draft-sxg-mpls-mna-deterministic-latency-00
Abstract
This document specifies formats and principles for the MPLS Network
Action for Deterministic Latency to provide guaranteed latency
services. They are used to make scheduling decisions for time-
sensitive services running on Deterministic Network (DetNet) nodes
that operate within a single or multiple domains.
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 30 November 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
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
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
3. Enhanced Deterministic Network Requirements . . . . . . . . . 4
3.1. Queuing Delay . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Deterministic Latency . . . . . . . . . . . . . . . . . . 5
4. MPLS Extensions for Deterministic Latency . . . . . . . . . . 5
4.1. Enhanced DetNet MPLS Header for Deterministic Latency . . 5
4.2. Deterministic Latency Network Action . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
8. Normative References . . . . . . . . . . . . . . . . . . . . 9
9. Informative References . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
[RFC8655] defines Deterministic Network (DetNet) architecture. The
overall framework for DetNet data plane is introduced in [RFC8938].
Deterministic Networking (DetNet) operates at the IP layer and
delivers services with low data loss rates and bounded latency
guarantee within a network domain.
[RFC8964] introduces the DetNet MPLS data plane technology providing
a foundation of building blocks to enable PREOF (Packet Replication,
Elimination and Ordering Functions (PREOF)) functions to DetNet
service sub-layer and forwarding sub-layer. The DetNet service sub-
layer includes a DetNet Control Word (d-CW), service label (S-Label),
an aggregation label (A-Label) in special case of S-Label used for
aggregation. The DetNet forwarding sub-layer supports one or more
forwarding labels (F-Labels) used to forward a DetNet flow over MPLS
domains. The DetNet forwarding sub-layer provides corresponding
forwarding assurance with resource allocations and explicit routes.
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To support time-sensitive service with ultra-low loss rates and
deterministic latency, it is required to apply feasible scheduling
mechanisms to specific applications for deterministic networking. As
described in [RFC9320], the end-to-end bounded latency is considered
as the sum of non-queuing and queuing delay bounds along with the
queuing mechanisms.
The queuing mechanisms, as mentioned in [RFC9320] and [RFC8655],
which include Time Aware Shaping IEEE802.1Qbv, Asynchronous Traffic
Shaping IEEE802.1Qcr, cyclic-scheduling queuing mechanism proposed in
IEEE802.1Qch. In terms of delay guarantee for different
applications, to select the right scheduling/queuing mechanism
applied to a specific application is required. Based on the existing
DetNet MPLS encapsulations and mechanisms [RFC8964], the document
defines the encoding format for Deterministic Latency Network Action
(DLNA) option in MPLS data plane.
But with DetNet network scaling up or flows number increased in the
same work, some enhanced data plane requirements for DetNet network
are brought, which are described at the
[I-D.ietf-detnet-scaling-requirements]. This document follows the
enhanced data plane requirements and introduces the MPLS MNA solution
to address the requirements specified at section 4.2 of
[I-D.ietf-detnet-scaling-requirements]. The deterministic network
should support synchronized or asynchronized queuing mechanisms.
Different queuing mechanisms require different information to be
defined as the DetNet-specific metadata to help the functions of
ensuring deterministic latency, including regulation, queue
management, etc.
The use case Delay Budgets for Time Bound Applications is under
discussion at MPLS MNA [I-D.ietf-mpls-mna-usecases]. MPLS Network
Actions (MNA) are used to indicate actions for LSPs and/or MPLS
packets and to transfer data needed for these actions.
[I-D.ietf-mpls-mna-hdr] defines the MNA solution for carrying Network
Actions with Sub-Stack Data and associated Ancillary Data (AD) (i.e.,
in the MPLS label stack).
This document presents one MPLS MNA solution for Deterministic
Latency. It follows the MPLS MNA requirements specified at
[I-D.ietf-mpls-mna-requirements] and MPLS MNA header specifid at
[I-D.ietf-mpls-mna-hdr] to support basic DetNet service and DetNet
service with enhanced DetNet data plane requirements specified at
[I-D.ietf-detnet-scaling-requirements] .
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2. Conventions
2.1. 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.
2.2. Terminology
Refer to [RFC8655], [RFC8964], [I-D.ietf-mpls-mna-hdr] and [RFC9320]
for the key terms used in this document.
Deterministic Latency (DL): The bound of network latency and delay
variation between two DetNet endpoints.
Deterministic Latency Network Action (DLNA): Used to indicate
deterministic latency network action for MPLS data plane.
3. Enhanced Deterministic Network Requirements
3.1. Queuing Delay
[RFC8655] provides the architecture for deterministic networking
(DetNet) which enables the service delivery of DetNet flows with
extremely low packet loss rates and deterministic latency. The
forwarding sub-layer provides corresponding forwarding assurance but
can not provide the deterministic latency (including bounded latency,
low packet loss and in-order delivery). As described at [RFC9320],
the end-to-end bounded latency for one DetNet flow is the sum of
delay bound of non-queuing and queuing processing latency. The delay
bound for non-queuing processing may include output delay, link
delay, frame preemption delay, and processing delay, the delay bound
for queuing processing may include regulator delay, queuing delay.
It is assumed that the delay of non-queuing processing is fixed or be
ignorable, the delay of queuing processing is variable. To realize
the guarantee of bounded latency service it is important to select
right queuing methodology applied to specific applications and carry
necessary queuing delay information for computation of end-to-end
latency.
The existing switches and routers have the ability to classify
traffic and provide independent queuing mechanisms based on Class of
Service (CoS) that CoS is used in the Priority Code Point (PCP) field
of the 802.1Q, DSCP field in IPv4 header and Traffic Class field in
IPv6 field. CoS defines the priority levels of traffic and QoS uses
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these CoS values to handle traffic to optimize traffic transmission.
To achieve deterministic/bounded latency service requirements, the
queuing mechanisms, as mentioned in [RFC9320] and [RFC8655], Time
Aware Shaping IEEE802.1Qbv, Asynchronous Traffic Shaping
IEEE802.1Qcr, cyclic-scheduling queuing mechanism proposed in
IEEE802.1Qc are used in single or multiple domains network.
3.2. Deterministic Latency
The DetNet data plane encapsulation in transport network with MPLS
data plane is specified in [RFC8964]. There is a requirement to
provide deterministic latency option to address DetNet scaling
question and support the enhanced data plane requirements described
at [I-D.ietf-detnet-scaling-requirements]. The option should include
end-to-end and hop-by-hop processing of packets to be adaptive to
different queuing mechanisms in DetNet networks.
The DetNet routers in data plane perform MPLS forwarding functions
using a feasible way with sufficient network resources for the
incoming packets, and makes right selection on the queuing or
scheduling mechanisms applied for specific DetNet flows to satisfy
strict deterministic service criteria in the forwarding output port.
The information for the queuing or scheduling mechanisms are carried
in the MPLS header. Refer to [I-D.stein-srtsn], considering the time
latency information are processed per hop so the time latency
informations (such as deadline time, cycle identify, etc.) of each
DetNet node for DetNet flows are expected to be carried as a set of
lists of LSEs in MPLS data plane.
4. MPLS Extensions for Deterministic Latency
This document provides an optional MNA header to address enhanced
DetNet data plane requirements described at
[I-D.ietf-detnet-scaling-requirements] to support different
deterministic service categories such as bandwidth guarantee, bounded
latency, loss ratio guarantee, etc.
4.1. Enhanced DetNet MPLS Header for Deterministic Latency
To support deterministic/bounded latency service this document
introduces an MPLS MNA MPLS Network Action (MNA) option for
Deterministic Latency Network Action (DLNA). As shown in Figure 1,
the MNA label is inserted to indicate the presence of MPLS Network
Actions. The format for DLNA follows the DetNet data plane MPLS
encapsulation specified at [RFC8964] and MNA encapsulation specified
in [I-D.ietf-mpls-mna-hdr] and [I-D.ietf-mpls-mna-fwk], which is
comprised of a set of Label Stack Entries (LSEs) that carry the DLNA
Indicator and Ancillary Data to perform DLNA actions for MPLS
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packets.
+---------------------------+
| DetNet App-Flow |
| Payload Packet |
+---------------------------+--\
| DetNet Control Word | |
+---------------------------+ |
| S-Label | | DetNet
+---------------------------+ | Data Plane
| DLNA | | MPLS Encapsulation
+---------------------------+ |
| MNA Label | |
+---------------------------+ |
| F-Label(s) | /
+---------------------------+--/
| Data-Link |
+---------------------------+
| Physical |
+---------------------------+
Figure 1: Enhanced DetNet MPLS Header for Deterministic Latency
As defined in [RFC8964], the DetNet functionality PREOF (Packet
Replication, Elimination and Ordering Functions) is supported through
d-CW,S-label and F-label. The queue mechanism for DetNet networks is
expected to use the existing COS mechanism, such as PCP for VLAN,
DSCP for IPv4, Traffic Class for IPv6. The S-lable is at the bottom
of MPLS label stack and normally followed by d-CW (DetNet Control-
Word, i.e., sequence number). The S-label is used to identify DetNet
service-type. F-lable(s) identify explicit route and allocated
resources for DetNet nodes, the route schedule and resource
reservation are achieved via provision by controller. D-CW (i.e.,
sequence number) is used for ordering function of DetNet packets. To
support backward compatibility, the aspects (DetNet d-CW, S-label,
F-label and A-label) are kept shown in MPLS sub-stack but outside of
MPLS MNA sub-stack. The base DetNet data plane MPLS encapsulation
follows specification at [RFC8964]. For base DetNet services, it's
assumed that the requirements can be satisfied via deploying CoS
mechanisms (i.e., PCP for VLAN, DSCP for IPv4 and Traffic Class for
IPv6) to DetNet network nodes.
For enhanced DetNet services, it is expected to deploy enhanced
queueing mechanisms and the queueing information may be carried in
data packets. The enhanced DetNet data plane requirements are
specified in [I-D.ietf-detnet-scaling-requirements]. To support
enhanced deterministic services, strict queuing technologies may be
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required for DetNet devices. Its related latency requirements may
involve different categories: (1) Industrial, tight jitter, strict
latency limit; (2) Industrial, strict latency limit; (3) Non-
periodic, relative loose latency requirements; (4) Best effort. And
different network implementations require different SLA requirements
with different queueing mechanisms implemented in single or multiple
network domains.
4.2. Deterministic Latency Network Action
The Deterministic Latency Network Action Sub-Stack format for MNA is
shown in Figure 2. The network action follows LSE format C to carry
DLNA Opcode and LSE format D for Additional Data as specified in
[I-D.ietf-mpls-mna-hdr].
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |R|IHS|S| Res |U| NASL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DLNA Opcode | Reserved |DLNA Flag|S| Res | NAL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| Deterministic Latency Data |S| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| Deterministic Latency Data |S| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: DLNA Sub-Stack
As specified at [I-D.ietf-mpls-mna-hdr], The header for MPLS Sub-
Stack Network Action encodes:
R (1 bit) : Reserved bit. This MUST be transmitted as zero and
ignored upon receipt.
IHS (2 bits) : The processing scope of the sub-stack.
S (1 bit) : The Bottom of Stack [RFC3032].
Res (3 bits) : Reserved bits. These MUST be transmitted as zeros and
ignored upon receipt.
U (1 bit): Unknown Action Handling.
NASL (4 bits) : The Network Action Sub-Stack Length (NASL). The
number of additional LSEs in the sub-stack, not including the leading
Format A LSE and the Format B LSE.
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DLNA Opcode (7 bits): This is the first 7-bit value in the Label
Field. The value is used to indicate DLNA network action with Data
and to be assigned by IANA as value TBA1.
DLNA Flags (5 bits): A bit map that specifies the type of enhanced
Deterministic latency. The supported Deterministic latency type is
listed in Table 1.
+=====+============================+
| Bit | Deterministic Latency Type |
+=====+============================+
| 0 | Reserved |
+-----+----------------------------+
| 1 | Latency Bound |
+-----+----------------------------+
| 2 | Queuing Delay Bound |
+-----+----------------------------+
Table 1: Deterministic Latency Type
Deterministic Latency Data (60 bits): The ancillary data LSEs for the
Deterministic Latency Type.
The Deterministic Latency Data speicification refers to [RFC9320] and
[I-D.ietf-detnet-dataplane-taxonomy], which introduces DetNet Bounded
Latency Model. To support deterministic latency services the latency
variation across the DetNet-aware or DetNet-unaware islands should be
bounded and computable. The Deterministic Latency Bound of End-to-
End and each nodes along with the DetNet flows should be included.
The additional parameters specification is for further study and
follow the latest discussion at DetNet working group.
5. IANA Considerations
This document requests one new IANA-managed code-point for
Deterministic Latency processing. IANA maintains the "Network Action
Opcodes" registry when created from IANA request in
[I-D.ietf-mpls-mna-hdr]. IANA is requested to allocate a value for
MPLS Network Action Opcode for Deterministic Latency Network Action
from this registry:
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+=======+=============+===============+
| Value | Description | Reference |
+=======+=============+===============+
| TBA1 | DLNA Opcode | This document |
+-------+-------------+---------------+
Table 2: MPLS Network Action Opcode
for Deterministic Latency
6. Security Considerations
Security considerations for DetNet are covered in the DetNet
Architecture RFC8655 and DetNet Security Considerations [RFC9055].
MPLS security considerations are covered in [RFC8964], [RFC3031],
[RFC3032]. These security considerations also apply to this
document. The MNA security considerations speicified at
[I-D.ietf-mpls-mna-hdr] and [I-D.ietf-mpls-mna-hdr] are also
applicable to the procedures defined in this document.
7. Acknowledgements
The authors would like to acknowledge Shaofu Peng for his thorough
review and very helpful comments.
8. Normative References
[I-D.ietf-mpls-mna-hdr]
Rajamanickam, J., Gandhi, R., Zigler, R., Song, H., and K.
Kompella, "MPLS Network Action (MNA) Sub-Stack Solution",
Work in Progress, Internet-Draft, draft-ietf-mpls-mna-hdr-
05, 1 May 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-mpls-mna-hdr-05>.
[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>.
[RFC8964] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
S., and J. Korhonen, "Deterministic Networking (DetNet)
Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
2021, <https://www.rfc-editor.org/info/rfc8964>.
9. Informative References
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[I-D.ietf-detnet-dataplane-taxonomy]
Joung, J., Geng, X., Peng, S., and T. T. Eckert,
"Dataplane Enhancement Taxonomy", Work in Progress,
Internet-Draft, draft-ietf-detnet-dataplane-taxonomy-00,
24 May 2024, <https://datatracker.ietf.org/doc/html/draft-
ietf-detnet-dataplane-taxonomy-00>.
[I-D.ietf-detnet-scaling-requirements]
Liu, P., Li, Y., Eckert, T. T., Xiong, Q., Ryoo, J.,
zhushiyin, and X. Geng, "Requirements for Scaling
Deterministic Networks", Work in Progress, Internet-Draft,
draft-ietf-detnet-scaling-requirements-06, 22 May 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-detnet-
scaling-requirements-06>.
[I-D.ietf-mpls-mna-fwk]
Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS
Network Actions (MNA) Framework", Work in Progress,
Internet-Draft, draft-ietf-mpls-mna-fwk-08, 7 May 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-mpls-
mna-fwk-08>.
[I-D.ietf-mpls-mna-requirements]
Bocci, M., Bryant, S., and J. Drake, "Requirements for
Solutions that Support MPLS Network Actions (MNA)", Work
in Progress, Internet-Draft, draft-ietf-mpls-mna-
requirements-15, 28 May 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-mpls-
mna-requirements-15>.
[I-D.ietf-mpls-mna-usecases]
Saad, T., Makhijani, K., Song, H., and G. Mirsky, "Use
Cases for MPLS Network Action Indicators and MPLS
Ancillary Data", Work in Progress, Internet-Draft, draft-
ietf-mpls-mna-usecases-07, 20 May 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-mpls-
mna-usecases-07>.
[I-D.stein-srtsn]
Stein, Y. J., "Segment Routed Time Sensitive Networking",
Work in Progress, Internet-Draft, draft-stein-srtsn-01, 29
August 2021, <https://datatracker.ietf.org/doc/html/draft-
stein-srtsn-01>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>.
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[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>.
[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>.
[RFC8938] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane
Framework", RFC 8938, DOI 10.17487/RFC8938, November 2020,
<https://www.rfc-editor.org/info/rfc8938>.
[RFC9055] Grossman, E., Ed., Mizrahi, T., and A. Hacker,
"Deterministic Networking (DetNet) Security
Considerations", RFC 9055, DOI 10.17487/RFC9055, June
2021, <https://www.rfc-editor.org/info/rfc9055>.
[RFC9320] Finn, N., Le Boudec, J.-Y., Mohammadpour, E., Zhang, J.,
and B. Varga, "Deterministic Networking (DetNet) Bounded
Latency", RFC 9320, DOI 10.17487/RFC9320, November 2022,
<https://www.rfc-editor.org/info/rfc9320>.
Authors' Addresses
Xueyan Song
ZTE Corp.
China
Email: song.xueyan2@zte.com.cn
Quan Xiong
ZTE Corp.
China
Email: xiong.quan@zte.com.cn
Rakesh Gandhi
Cisco Systems, Inc.
Canada
Email: rgandhi@cisco.com
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