Deterministic Networking specific MNA
draft-varmir-mpls-detnet-mna-00
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| Authors | Greg Mirsky , Balazs Varga | ||
| Last updated | 2024-07-22 | ||
| Replaced by | draft-songvar-mpls-mna-detnet | ||
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draft-varmir-mpls-detnet-mna-00
MPLS G. Mirsky
Internet-Draft B. Varga
Intended status: Standards Track Ericsson
Expires: 23 January 2025 22 July 2024
Deterministic Networking specific MNA
draft-varmir-mpls-detnet-mna-00
Abstract
In IETF the Deterministic Networking (DetNet) Working Group focuses
on deterministic data paths that can provide bounds on latency, loss,
and packet delay variation (jitter), and high reliability. This
document focuses on the MPLS Data Plane, namely, how to use MNA (MPLS
Network Action) for DetNet flows, when forwarded over an MPLS
technology-based network domain.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 23 January 2025.
Copyright Notice
Copyright (c) 2024 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/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.1. Terms Used in This Document . . . . . . . . . . . . . . . 3
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
2.3. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. DetNet-specific MNA . . . . . . . . . . . . . . . . . . . . . 3
4. DetNet information in NASes . . . . . . . . . . . . . . . . . 4
4.1. DetNet-specific NASes . . . . . . . . . . . . . . . . . . 4
4.2. Characteristics of DetNet NASes . . . . . . . . . . . . . 5
4.3. Examples of DetNet NASes . . . . . . . . . . . . . . . . 6
4.4. Aggregation Example . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
8. Normative References . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
DetNet work group has defined Packet Replication Function (PRF) and
Packet Elimination Function (PEF) to achieve extreme low packet loss.
In general, usage of these per packet replication and elimination
functions may result in out-of-order delivery of frames/packets
[RFC8655]. This characteristic of PRF/PEF was identified by IETF and
a Packet Ordering Function (POF) was defined [RFC9550]. The POF
function is a DetNet service sub-layer function similar to PRF and
PEF. All the DetNet service sub-layer functions are usually referred
as Packet Replication, Elimination and Ordering Functions (PREOF).
These DetNet service sub-layer related functions require ordering
information (e.g., sequence number). IETF DetNet WG has defined how
sequencing information (i.e., sequence number) travels with DetNet
packets using the d-CW [RFC8964], when PW (PseudoWire) technology is
used with an MPLS Data Plane.
The DetNet forwarding sub-layer related functions focus on ensuring
the bounded latency requirements and they may intend to use packet
specific latency information during the forwarding. No solution was
defined to add such latency specific information to the PW
encapsulated DetNet packets.
2. Terminology
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2.1. Terms Used in This Document
This document uses the terminology established in the DetNet
architecture [RFC8655]. The reader is assumed to be familiar with
that document and its terminology.
2.2. Abbreviations
The following abbreviations are used in this document:
DetNet Deterministic Networking
Flow-ID Flow Identifier
MNA MPLS Network Action
NAI Network Action Indicator
NAS Network Action Sub-Stack
LSE Label Stack Entry
PEF Packet Elimination Function
POF Packet Ordering Function
PREOF Packet Replication, Elimination and Ordering Functions
PRF Packet Replication Function
SeqNum Sequence Number
2.3. 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.
3. DetNet-specific MNA
There are three information elements that may be required during the
forwarding of DetNet packets:
1. Flow identifier (Flow-ID)
2. Sequence information (SeqNum)
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3. Latency information (LatencyInfo)
"1" and "2" are used by the DetNet service sub-layer (i.e., by
PREOF). "1" and "3" are used by the DetNet forwarding sub-layer to
ensure the bounded latency for a DetNet packet.
The usage of a DetNet-specific MNA solution allows using a single
encapsulation format for all DetNet specific parameters (Flow-ID,
SeqNum, LatencyInfo) as MNA data. DetNet-specific MNA allows more
fine-tuned and scalable handling of the latency bound requirement
together with service protection natively in MPLS. The MNA based
DetNet solution does not require any post-stack-data, contrary to the
mandatory d-CW used by PW technology.
4. DetNet information in NASes
4.1. DetNet-specific NASes
The MPLS MNA encapsulation is used between DetNet Relay nodes.
DetNet specific parameters used during forwarding are: (1) Flow-ID,
(2) SeqNum and (3) LatencyInfo. For each of them, a specific NAS can
be defined to carry the related variable in an MPLS MNA network:
1. PREOF specific NAS (e.g., SeqNum)
2. Latency specific NAS (e.g., LatencyClass)
3. Flow specific NAS (i.e., Flow-ID)
Note: DetNet aggregate flows can be described with the same set of
parameters.
DetNet functions use these NASes as follow:
* DetNet PREOF requires Flow-ID+SeqNum parameters. They are used
only at DetNet Relay nodes implementing the service sub-layer.
* DetNet latency bound related functions use Flow-ID+LatencyInfo,
for selecting proper queuing hop-by-hop along the transmission
path. They are used at DetNet Transit nodes implementing the
forwarding sub-layer.
Using these NASes in DetNet scenarios results in the following MPLS
encapsulation format example, that ensures placing all DetNet
parameters in the NASes:
* LSP(s) = F-Label(s): used for describing the forwarding path.
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* MNA Sub-Stack Indicator.
* NAS-3: (NAI: Flow-ID, Ancillary Data (AD): i.e., Flow-ID).
* NAS-2: (NAI: Latency, Ancillary Data (AD): e.g., LatencyClass).
* NAS-1: (NAI: SeqNum, Ancillary Data (AD): i.e., SeqNum (16/28
bits)).
* Payload.
Note: that using PW (S-Label) in the label stack is optional, it is
not precluded by the method described in this document, and not shown
in the above example.
4.2. Characteristics of DetNet NASes
Characteristics of the DetNet specific NASes are as follows:
* Encoding a Network Action: Different Operation Codes are used for
the above DetNet specific NASes.
* Scope is encoded implicitly, all DetNet NAIs (Network Action
Indicator) have a predefined scope.
- All DetNet specific NAI use "Select" mode, so usage of these
NAIs may be restricted for DetNet-aware nodes if the operator
intends to do so.
- Optional scope for the NAIs:
o NAI: Flow-ID can have Hop-by-hop (HBH) scope.
o NAI: Latency can have Hop-by-hop (HBH) scope.
o NAI: SeqNum can have Ingress-to-Egress (I2E) scope.
* Recognition action:
- NAI: Flow-ID is used for flow identification, and this NAI must
be ignored if unrecognized.
- NAI: Latency is used by every node along the path those perform
latency related action (e.g., queuing). This NAI must be
ignored if unrecognized.
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- NAI: SegNum is used only by the last node on the path defined
by the F-Label(s) and perform the PREOF action. If this NAI is
unrecognized the packet may be dropped.
* Encoding of Post-Stack Data: N/A for these NASes.
Via using the "Select" mode for the DetNet specific NASes, the
network operation can emulate the MS-PW (Multi-Segment PW) pop-push
characteristics on the S-Label. There is no need to define at
ingress the whole forwarding graph across the MPLS network.
Furthermore, "Select" mode allows that the payload is an MPLS packet
using the same label stack (as used by the MNA).
4.3. Examples of DetNet NASes
The figures show some possible DetNet specific NAS formats and their
usage.
DetNet Latency NAS: Format-B provides enough bits to encode e.g.,
several LatencyClass-es. For longer latency related parameters
(e.g., time stamp) Format C/C+D can be used.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label (MNA bSPL) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode | Data (Latency Info) |R|IHS|S| Res |U| NASL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: An Example of the DetNet Latency Information Encoding
Using LSE Format B
DetNet SeqNum NAS: Depending on the location of the SeqNum parameter
within the MNA part of the MPLS stack a Format B+C/C/C+D is needed
(contains 28/16 bits of the SeqNum). In these formats there are
unused "Data bits" to carry additional FLAGs related to the SeqNum.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label (MNA bSPL) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode | Data (SeqNum) |R|IHS|S| Res |U| NASL=1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode | Data (cont.) |S| Data | NAL=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: An Example of the DetNet Sequence Number Encoding Using
LSE Formats B and C
DetNet Flow-ID NAS: Depending on the location of the Flow-ID a Format
C/B+C is needed (contains 20 bits of the ID).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label (MNA bSPL) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode | Data (Flow-ID) |R|IHS|S| Res |U| NASL=1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode | Data (cont.) |S| Data | NAL=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: An Example of the DetNet LFlow Identifier Encoding
Using LSE Formats B and C
Figure 4 below shows an MNA which contains all the DetNet specific
NASes. MNA-6 contains the DetNet Latency parameter being encoded in
Format-B. MNA-7 contains the DetNet Flow-ID, a 20 bits Flow-ID is
encoded in Format C. MNA-8 contains the DetNet SeqNum in Format C
with a 16 bits sequence number.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label (MNA bSPL) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode (6)| Data (Latency Info) |R|IHS|S| Res |U| NASL=2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode (7)| Data (Flow-ID) |S| (FID) | NAL=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode (8)| Data (SeqNum) |S| 0 | NAL=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Figure 4: An Example of the Combined DetNet Parameters Encoding
Using MNA
4.4. Aggregation Example
Figure 5 shows an aggregation example, where multiple DetNet flows
are aggregated in a single aggregate. NAS-A part contains the
aggregate specific DetNet NASes, and NAS-F contains the flow specific
NASes of the data packet.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label (MNA bSPL) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode (x)| Data (Aggr-Latency-Info)|R|IHS|S| Res |U| NASL=2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode (y)| Data (Aggr-Flow-ID) |S| (FID) | NAL=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode (z)| Data (Aggr-SeqNum) |S| 0 | NAL=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label (MNA bSPL) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode (x)| Data (Latency Info) |R|IHS|S| Res |U| NASL=2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode (y)| Data (Flow-ID) |S| (FID) | NAL=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode (z)| Data (SeqNum) |S| 0 | NAL=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: An Example of the DetNet Aggregate Flow Parameters
Encoding Using MNA
Note1: Opcodes are to be allocated by IANA during the
standardization.
Note2: NAS-x denotes the NAS containing the DetNet parameter. "x"
just a number on the figure to denote that they contain different
information.
Note3: Aggregation re-uses the same Options code points for the
aggregated and specific flows. The interpretation is based on the
order of NASes. During de-aggregation of flows the MNA containing
the aggregate parameters are removed from the label stack (poped).
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5. Security Considerations
This specification desribes the realization of DetNet over MPLS data
plane using MNA approach. As a result, it inherits security
considerations of [RFC8964] and [I-D.ietf-mpls-mna-hdr].
6. IANA Considerations
IANA is requested to assign a new Opcode values from the Network
Action Opcodes Registry as follows:
+=======+=====================+===============+
| Value | Description | Reference |
+=======+=====================+===============+
| TBA1 | Flow Identifier | This document |
+-------+---------------------+---------------+
| TBA2 | Sequence Number | This document |
+-------+---------------------+---------------+
| TBA3 | Latency Information | This document |
+-------+---------------------+---------------+
Table 1: DetNet Parameters in MNA
7. Acknowledgements
Authors extend their appreciation to Joel Halpern, Janos Farkas, and
Ferenc Fejes for their insightful comments and contributions.
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-
07, 17 June 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-mpls-mna-hdr-07>.
[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>.
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[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>.
[RFC9550] Varga, B., Ed., Farkas, J., Kehrer, S., and T. Heer,
"Deterministic Networking (DetNet): Packet Ordering
Function", RFC 9550, DOI 10.17487/RFC9550, March 2024,
<https://www.rfc-editor.org/info/rfc9550>.
Authors' Addresses
Greg Mirsky
Ericsson
Email: gregimirsky@gmail.com
Balazs Varga
Ericsson
Email: balazs.a.varga@ericsson.com
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