Status of This Memo

This is an Internet Standards Track document.¶

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.¶

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc9025.¶

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Table of Contents

1. Introduction

Deterministic Networking (DetNet) is a service that can be offered by a network to DetNet flows. DetNet provides these flows extremely low packet loss rates and assured maximum end-to-end delivery latency. General background and concepts of DetNet can be found in [RFC8655].¶

To carry DetNet MPLS flows with full functionality at the DetNet layer over an IP network, the following components are required (these are a subset of the requirements for MPLS encapsulation listed in [RFC8964]):¶

1. A method for identifying DetNet flows to the processing element.¶
2. A method for carrying the DetNet sequence number.¶
3. A method for distinguishing DetNet Operations, Administration, and Maintenance (OAM) packets from DetNet data packets.¶
4. A method for carrying queuing and forwarding indication.¶

These requirements are satisfied by the DetNet over MPLS Encapsulation described in [RFC8964] and they are partly satisfied (i.e., IP flows can be identified; however, no DetNet sequence number is carried) by the DetNet IP data plane defined in [RFC8939].¶

This document specifies use of the MPLS DetNet encapsulation over an IP network. The approach is modeled on the operation of MPLS over an IP Packet Switched Network (PSN) using UDP encapsulation [RFC7510]. It maps the MPLS data plane encapsulation described in [RFC8964] to the DetNet IP data plane defined in [RFC8939].¶

[RFC7510] specifies that "MPLS-in-UDP MUST NOT be used over the general Internet, or over non-cooperating network operators, to carry traffic that is not congestion controlled." This constraint does apply to the use of RFC 7510 in a DetNet network because DetNet is constrained to operate within a single administrative control or within a closed group of administrative control.¶

3. DetNet MPLS Operation over DetNet IP PSNs

This document builds on the specification of MPLS over UDP defined in [RFC7510]. It may partly or entirely replace the F-Label(s) used in [RFC8964] with UDP and IP headers. The UDP and IP header information is used to identify DetNet flows, including member flows, per [RFC8939]. The resulting encapsulation is shown in Figure 1. There may be zero or more F-Labels between the S-Label and the UDP header.¶

Note that this encapsulation works equally well with IPv4, IPv6, and IPv6-based Segment Routing [RFC8754].¶

+---------------------------------+
|                                 |
|         DetNet App-Flow         |
|         Payload  Packet         |
|                                 |
+---------------------------------+ <--\
|       DetNet Control Word       |    |
+---------------------------------+    +--> DetNet data plane
|             S-Label             |    |    MPLS encapsulation
+---------------------------------+    |
|          [ F-Label(s) ]         |    |
+---------------------------------+ <--+
|           UDP Header            |    |
+---------------------------------+    +--> DetNet data plane
|           IP Header             |    |    IP encapsulation
+---------------------------------+ <--/
|           Data-Link             |
+---------------------------------+
|           Physical              |
+---------------------------------+

S-Labels, A-Labels (when present), d-CW, and zero or more F-Labels are used as defined in [RFC8964] and are not modified by this document.¶

4. DetNet Data Plane Procedures

To support outgoing DetNet MPLS over UDP encapsulation, an implementation MUST support the provisioning of UDP and IP header information in addition to or in place of F-Label(s). Note, when the PRF is performed at the MPLS service sub-layer, there will be multiple member flows, and each member flow will require the provisioning of their own UDP and IP header information. The headers for each outgoing packet MUST be formatted according to the configuration information and as defined in [RFC7510], and the UDP Source Port value MUST be set to uniquely identify the DetNet flow. The packet MUST then be handled as a DetNet IP packet, per [RFC8939]. This includes QoS-related traffic treatment.¶

To support the receive processing defined in this document, an implementation MUST also support the provisioning of received UDP and IP header information. The provisioned information MUST be used to identify incoming app flows based on the combination of S-Label and incoming encapsulation header information. Normal receive processing as defined in [RFC8964], including PEF and POF, can then take place.¶

5. Management and Control Information Summary

The following summarizes the minimum set of information that is needed to configure DetNet MPLS over UDP/IP:¶

• Label information (A-Labels, S-Labels, and F-Labels) to be mapped to UDP/IP flows. Note that, for example, a single S-Label can map to multiple sets of UDP/IP information when PREOF is used.¶
• IPv4 or IPv6 source address field¶
• IPv4 or IPv6 destination address field¶
• DSCP Field in either IPv4 Type of Service or IPv6 Traffic Class Fields¶
• UDP Source Port¶
• UDP Destination Port¶
• Use/non-use of UDP checksum¶

This information MUST be provisioned per DetNet flow via configuration, e.g., via the controller [RFC8655] or management plane. Not using the UDP checksum has to be evaluated on a case-by-case basis for a given network scenario based on the exception criteria defined in [RFC7510], particularly when IPv6 is used.¶

It is the responsibility of the DetNet Controller Plane to properly provision both flow identification information and the flow-specific resources needed to provide the traffic treatment needed to meet each flow's service requirements. This applies for both aggregated and individual flows.¶

7. IANA Considerations

This document has no IANA actions.¶

Acknowledgements

The authors wish to thank Pat Thaler, Norman Finn, Loa Anderson, David Black, Rodney Cummings, Ethan Grossman, Tal Mizrahi, David Mozes, Craig Gunther, George Swallow, Yuanlong Jiang, and Carlos J. Bernardos for their various contributions to this work.¶

Contributors

This document is derived from an earlier draft that was edited by Jouni Korhonen (jouni.nospam@gmail.com), and as such, he contributed to and authored text in this document.¶

Authors' Addresses