MPLS Sub-Stack Encapsulation for Deterministic Latency Action
draft-sx-detnet-mpls-queue-03
The information below is for an old version of the document.
| Document | Type |
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|---|---|---|---|
| Authors | Xueyan Song , Quan Xiong | ||
| Last updated | 2022-11-06 | ||
| Replaced by | draft-sx-mpls-detnet-bounded-latency | ||
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draft-sx-detnet-mpls-queue-03
DetNet Working Group X. Song
Internet-Draft Q. Xiong
Intended status: Standards Track ZTE Corp.
Expires: 10 May 2023 6 November 2022
MPLS Sub-Stack Encapsulation for Deterministic Latency Action
draft-sx-detnet-mpls-queue-03
Abstract
This document specifies formats and principals for the MPLS header
which contains the Deterministic Latency Action (DLA) information,
designed for use over a DetNet network with MPLS data plane. It
enables guaranteed delay support and makes scheduling decisions for
time-sensitive service running on DetNet nodes that operate within a
constrained network domain.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 10 May 2023.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
3. DetNet queue encapsulation with MPLS data plane . . . . . . . 3
3.1. Queuing delay . . . . . . . . . . . . . . . . . . . . . . 4
3.2. DetNet MPLS Encapsulation with Delay Option . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
As specified in [RFC8655] and [RFC8938], Deterministic Networking
(DetNet) operates at the IP layer and delivers service with low data
loss rates and bounded latency guarantee within a network domain.
As defined in [RFC8964], the DetNet MPLS data plane provides a
foundation of building blocks to enable PREOF (Packet Replication,
Elimination and Ordering Functions (PREOF)) functions to DetNet
service 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 IETF existing functions using resource
allocations and explicit routes. But these functions can not provide
the deterministic latency (including bounded latency, low packet loss
and in-order delivery) assurance.
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 [I-D.ietf-detnet-bounded-latency], the end-to-end
bounded latency is considered as the sum of non-queuing and queuing
delay bounds along with the queuing mechanisms. The value for non-
queuing delay bounds (which consist of packet output delay, link
delay, frame preemption delay and processing delay) is relative with
the physical capability of on-used networks and can be considered to
be stable. The unstable latency delay bounds are mainly from queuing
delay and regulation delay. The regulation delay is mainly from
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regulation policy. To simplify the question this draft assumes there
is no regulation policy. So the question is left to address the
selection for queuing mechanisms and queuing delay information
encapsulation in data plane.
The queuing mechanisms, as mentioned in
[I-D.ietf-detnet-bounded-latency] 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, 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 draft defines the encoding format for Deterministic
Latency Action (DLA) carried in MPLS sub-stack.
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.jags-mpls-mna-hdr] and
[I-D.ietf-detnet-bounded-latency] for the key terms used in this
document.
Deterministic Latency (DL):the bound of network latency and delay
variation between two DetNet endpoints. It may includes parameters
such as bounded latency, bounded delay variation, etc.
Deterministic Latency Action (DLA): used to indicate deterministic
latency actions for MPLS Sub-Stack.
3. DetNet queue encapsulation with MPLS data plane
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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
[I-D.ietf-detnet-bounded-latency], 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 DetNet data plane encapsulation in transport network with MPLS
data plane is specified in [RFC8964]. This document provides
additional encapsulation for the DLA in MPLS data plane.
3.2. DetNet MPLS Encapsulation with Delay Option
The DetNet MPLS header follows [RFC8964], as showed the below figure
1, the SP-Lable (SPL) is added to indicate Deterministic Latency
Action (DLA).
+---------------------------+
| DetNet App-Flow |
| Payload Packet |
+---------------------------+--\
| DetNet Control Word | |
+---------------------------+ |
| S-Label | | DetNet Data Plane
+---------------------------+ | MPLS Encapsulation
| SP-Lable | |
+---------------------------+ |
| F-Label(s) | |
+---------------------------+--/
| Data-Link |
+---------------------------+
| Physical |
+---------------------------+
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Figure 1: DetNet MPLS Header
The SP-L (Special Purpose-Label) may be B-SPL [RFC9017], new-SPL,
extended SPL [RFC9017]. This draft follows the MNA (MPLS Network
Action) solution specified in [I-D.jags-mpls-mna-hdr] and
[I-D.ietf-mpls-mna-fwk], and uses b-SPL to indicate the presence of
the MPLS Network Action Sub-Stack (NASS). The value for the bSPL
value is to be assigned by IANA and follows the assignment in
[I-D.jags-mpls-mna-hdr]. The SP-Label field is formatted as below
figure.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NASI Label = bSPL (TBA1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: SP-Label Format
NASI Label:
A new bSPL value is to be assigned by IANA. It is used to indicate
the presence of the MPLS Network Action Sub-Stack (NASS). The
assignment for this field value refers to [I-D.jags-mpls-mna-hdr].
The MPLS sub-stack encoding format for DetNet Latency Action (DLA) is
showed as figure 3. The format provides DetNet Latency Network
Action Indicator (NAI) indicates the specific DLA. Its detailed
information is carried in Ancillary Data.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode | Flag-Based NAI |R|NAL|S| 0 |IHS| NASL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| Ancillary Data |S| Ancillary Data|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| Ancillary Data |S| Ancillary Data|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: MPLS LSE Format for DLA
NAI-Opcode:
This is the first 8-bit value in the Label Field. The value is used
to indicate DLA and to be assigned by IANA. It ranges from 0 to 255.
Flag-Based NAIs:
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The Flag-Based NAIs field carries flags for DetNet Queuing
mechanisms.
R bit:
R bit in the TC field is Reserved for future use.
NAL (Network Action Length):
The 2-bit field in TC is used to carry the number of additional LSEs
used to carry the Ancillary Data for the Network Action. The NAL
value for DetNet MUST set to 2.
S bit:
Indicator for bottom of MPLS stack.
P,H (Post-Stack Network Action Presence and Post-Stack Hop-By-hop
processing Indicator) bit:
This is 2-bit flag, where "P" bit indicates the presence of Post-
Stack Network Actions and "H" bit indicates the presence of Post-
Stack Hop-By-Hop and/or Select processing scope options. While
encoding the Post-Stack NAs, the HBH/Select scope NAs MUST be encoded
first (closer to the BOS) and then I2E. The DetNet Queuing Option is
proposed to use in-stack encoding, the P,H field is set to 0.
IHS (I2E, HBH, and Select Scope):
This 2-bit value indicates the scope of In-Stack NAIs. DetNet
Queuing Option is considered to be processed by HBH, so the value is
set to 01 refers to table 1 in [I-D.jags-mpls-mna-hdr].
NASL (Network Action Sub-Stack Length):
This is a 4-bit field in the TTL. This indicates the total length of
the current NASS.
The first bit in the Label field of the second and third LSE MUST be
set to "1". As specified in [I-D.jags-mpls-mna-hdr] this is to
prevent aliasing the label field with other bSPLs on the legacy
routers.
Ancillary Data:
The 19-bit Label field and 4-bit TC field and 8-bit TTL field (except
S bit) in the additional LSEs are used to carry the Ancillary Data
for specific DetNet queuing delay information.
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The Flag-Based NAIs field is designed as follow:
0 1 2 3 4 5 6 7 0 1 2 3 4
+-+-+-+-+-+-+-+-+-+-+-+-+
|T|P|C| |
+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Flag-based NAIs
T Flag: 1 bit, TAS (Time Aware Shaping) [IIEEE802.1Qbv] queuing
indicator. If the flag is set 1, the TAS is used for the DetNet
flows, the can be correlated with the special label encapsulated in
figure 2, or be mapped with F-Label (s) or S-Label showed in figure
1.
P Flag: 1 bit, Credit-Based Shaper [IEEE802.1q-2014] queuing
indicator.
C Flag: 1 bit, CQF [IEEE802.1Qch] queuing indicator.
Note: For one specific DetNet flow, there is one or more choices for
queuing mechanisms selection, the queuing mechanisms can be used
respectively or combined with each other.
If the flag field is set 1 it will associate its AD (Ancillary Data)
for specific queuing delay information. The encapsulation for AD is
showed as TLV format.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Special Queuing Ancillary Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Ancillary data for queuing delay
The encapsulation for specific queuing delay information follows the
requirements and framework of MPLS MNA discussed in MPLS WG.
The encapsulation for Special Queuing Ancillary Data field is
specific for queuing mechanisms. For example, the deadline queuing
may carry deadline delay information, refer to
[I-D.peng-6man-deadline-option].The cyclic-scheduling queuing may
carry cycle ID related information, refer to
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[I-D.dang-queuing-with-multiple-cyclic-buffers]. The detailed format
depends on the discussion on the corresponding drafts and left for
FFS.
4. IANA Considerations
This document describes a new IANA-managed registry to identify
DetNet application processing. The registration procedure is "IETF
Review" [RFC8126]. The registry name is "NAI-Opcode" and assigned
for DLA Indicator, as defined in Table 1.
+============+=============+===============+
| Value | Description | Reference |
+============+=============+===============+
| Unassigned | NAI-Opcode | this document |
+------------+-------------+---------------+
Table 1: DLA Indicator
This document describes a new IANA-managed registry to identify
DetNet MPLS Queue Flags Bits. The registration procedure is "IETF
Review" [RFC8126]. The registry name is "Flag-based-NAIs". There is
12-bit Flag field, as defined in Table 2.
+==============+============+=============+===============+
| Bit Position | Symbol | Description | Reference |
+==============+============+=============+===============+
| 0 | T | TAS Flag | this document |
+--------------+------------+-------------+---------------+
| 1 | P | CBS Flag | this document |
+--------------+------------+-------------+---------------+
| 2 | C | CQF Flag | this document |
+--------------+------------+-------------+---------------+
| 3-11 | Unassigned | Unassigned | this document |
+--------------+------------+-------------+---------------+
Table 2: Flags for DLA Indicator
5. 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.
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6. Acknowledgements
The authors would like to acknowledge Shaofu Peng for his thorough
review and very helpful comments.
7. References
7.1. 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>.
[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>.
[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>.
[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>.
[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>.
[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>.
[RFC9017] Andersson, L., Kompella, K., and A. Farrel, "Special-
Purpose Label Terminology", RFC 9017,
DOI 10.17487/RFC9017, April 2021,
<https://www.rfc-editor.org/info/rfc9017>.
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7.2. Informative 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-mpls-mna-fwk]
Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS
Network Actions Framework", Work in Progress, Internet-
Draft, draft-ietf-mpls-mna-fwk-02, 21 October 2022,
<https://www.ietf.org/archive/id/draft-ietf-mpls-mna-fwk-
02.txt>.
[I-D.jags-mpls-mna-hdr]
Rajamanickam, J., Gandhi, R., Zigler, R., Song, H., and K.
Kompella, "MPLS Network Action (MNA) Header Encodings",
Work in Progress, Internet-Draft, draft-jags-mpls-mna-hdr-
03, 5 November 2022, <https://www.ietf.org/archive/id/
draft-jags-mpls-mna-hdr-03.txt>.
[I-D.peng-6man-deadline-option]
Peng, S., Tan, B., and P. Liu, "Deadline Option", Work in
Progress, Internet-Draft, draft-peng-6man-deadline-option-
01, 11 July 2022, <https://www.ietf.org/archive/id/draft-
peng-6man-deadline-option-01.txt>.
[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>.
Authors' Addresses
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Xueyan Song
ZTE Corp.
Nanjing
China
Email: song.xueyan2@zte.com.cn
Quan Xiong
ZTE Corp.
Wuhan
China
Email: xiong.quan@zte.com.cn
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