RFC 9634

Operations, Administration, and Maintenance (OAM) for Deterministic Networking (DetNet) with the IP Data Plane

📅 published October 2024, from ietf

📄 RFC 9634: OAM for DetNet with the IP Data Plane 🎀

okay bestie, this one is a 2024 Informational RFC 🌸 from the IETF, so it's a "here's some useful info" doc and not a must-follow standard. 💅 It's written by G. Mirsky (Ericsson), M. Chen (Huawei), and D. Black (Dell EMC), and it was published in October 2024. 🦋 It doesn't obsolete or update any other RFCs, so it's a totally independent little gem ✨. Its ISSN is 2070-1721 🔥.

The whole vibe is: how do we use the existing IP OAM tools (the ones that check if a path is alive and how it's performing 🩺) inside DetNet networks 🧚 that run on the IP data plane? Spoiler: the answer is "reuse what we've got, but make sure the test packets get the exact same treatment as the real traffic" 💜.

Abstract ✨

okay so the abstract is super short 🫶: this doc talks about using the existing IP Operations, Administration, and Maintenance protocols and mechanisms in Deterministic Networking networks that use the IP data plane. 🌈 That's the whole pitch, bestie.

Status of This Memo 📌

this part is the official "what kind of doc is this" bit 🙈. It's not an Internet Standards Track spec, it's published for informational purposes 🍓. It is an IETF product with IETF consensus, reviewed publicly and approved by the IESG 💅. For the fancy stuff about which docs can become standards, check Section 2 of RFC 7841 🧐. You can track errata and leave feedback at https://www.rfc-editor.org/info/rfc9634 🔥.

Copyright Notice 💖

© 2024 IETF Trust and the authors, all rights reserved 💅. This doc is under BCP 78 and the IETF Trust's Legal Provisions (https://trustee.ietf.org/license-info) as of the publication date, so read those if you're using it, because they explain your rights ✨. If you pull code components out of this doc, they need the Revised BSD License text (Section 4.e of the Trust Legal Provisions) and they come with no warranty 🎀.

Table of Contents 🦋

Introduction 🌸
Conventions Used in This Document 🌸
- 2.1. Terminology 🌸
Active OAM for DetNet Networks with the IP Data Plane ✨
- 3.1. Mapping Active OAM and IP DetNet Flows 🧚
- 3.2. Active OAM Using IP-in-UDP Encapsulation 🧚
- 3.3. Active OAM Using DetNet-in-UDP Encapsulation 🧚
- 3.4. The Application of Y.1731/G.8013 Using GRE-in-UDP Encapsulation 🧚
Active OAM for DetNet IP Interworking with OAM for Non-IP DetNet Domains 🌈
IANA Considerations 🌈
Security Considerations 🌈
References 🌈
- 7.1. Normative References 🌈
- 7.2. Informative References 🌈

Authors' Addresses 💌

1. Introduction 🌸

okay so [RFC8655] is the one that introduces DetNet, the whole Deterministic Networking architecture 🧠. Super foundational, read it first bestie 💜.

Now OAM. 🩺 OAM is what detects and pinpoints defects in the network AND keeps an eye on performance. Some stuff, like failure detection, runs proactively in the background 🔥, while other stuff, like localizing a defect, is usually done on demand when someone needs it 💅. Both of those get done with a mix of active and hybrid OAM methods, per [RFC7799] 🦋.

[RFC9551] is the one listing the OAM functional requirements for DetNet and laying down the principles for OAM in DetNet networks running the IP data plane 🌷. You can compare those requirements against today's OAM tools to see the gaps and what needs improving so you can do proactive and on-demand path monitoring and service validation ✨. Very organized, very iconic.

And this document? It's about how we can use the existing IP OAM protocols and mechanisms in DetNet networks that use the IP data plane 💖. Reuse, don't reinvent, periodt 💅.

2. Conventions Used in This Document 🌸

2.1. Terminology 🌸

okay so the doc defines "DetNet OAM" as "a set of OAM protocols, methods, and tools for Deterministic Networking" 🎀.

Here are the key terms, bestie:

DetNet: Deterministic Networking 🧚
OAM: Operations, Administration, and Maintenance 🧚
ICMP: Internet Control Message Protocol 🧚
Underlay Network or Underlay Layer: the network that gives connectivity between DetNet nodes 🌈. MPLS networks that provide Label Switched Path (LSP) connectivity between DetNet nodes are an example of a DetNet IP network underlay layer 💜.
DetNet Node: a node that's an actor in the DetNet domain 👑. DetNet domain edge nodes and nodes doing the Packet Replication, Elimination, and Ordering Functions inside the domain are examples 🦋.

3. Active OAM for DetNet Networks with the IP Data Plane ✨

okay this is the main event 🔥. OAM protocols and mechanisms act inside the data plane of a given networking layer 🧚. So it's critical that the data plane encapsulation supports OAM mechanisms and can be configured so that DetNet OAM packets take the same path (unidirectional or bidirectional) through the network 🛤️, and get the same forwarding treatment in the DetNet forwarding sub-layer as the DetNet flow being monitored 💅. Main character energy, the test packets have to be treated like the real thing 👑.

The DetNet data plane encapsulation in a transport network with IP encapsulations is specified in Section 6 of [RFC8939] 🌸. For the IP underlay network, DetNet flows are identified by an ordered match against a provisioned information set 🔍. That set includes, among other elements, the IP protocol type, source port number, and destination port number 🎀.

Active IP OAM protocols like Bidirectional Forwarding Detection (BFD) [RFC5880] or the Simple Two-way Active Measurement Protocol (STAMP) [RFC8762] use UDP transport, and they use well-known UDP port numbers as their destination ports 🦋. For BFD, the UDP destination port depends on the BFD variant. For example, multihop BFD uses port 4784 [RFC5883] 🧚.

So a DetNet node must be able to tie an IP DetNet flow to the particular test session, so the test packets get the same treatment as the DetNet flow packets 💖. Here's an example: in a network where path selection and DetNet functionality are based on 3-tuples (destination and source IP addresses plus the Differentiated Services Code Point value) 🌈, you can make that association by having the OAM traffic use the same 3-tuple as the monitored IP DetNet flow 🫶. In that setup, an IP OAM session between the same pair of IP nodes shares the network treatment with the monitored IP DetNet flow, no matter whether ICMP, BFD, or STAMP is used 💅. Iconic.

In IP networks, most on-demand failure detection and localization is done with ICMP 🩺. It uses Echo Request and Echo Reply messages, plus a set of defined error messages like Destination Unreachable, which give detailed info through assigned code points ✨. [RFC0792] and [RFC4443] define ICMP for IPv4 and IPv6 networks respectively 🌸. To use ICMP well for these purposes inside DetNet, DetNet nodes must associate ICMP traffic between DetNet nodes with IP DetNet traffic 🔥. That means the ICMP traffic must traverse the same interfaces and get QoS treatment identical to the monitored DetNet IP flow 💜. If that doesn't happen, ICMP might not be able to detect and localize failures specific to the DetNet IP data plane 🙈. Not ideal, bestie.

3.1. Mapping Active OAM and IP DetNet Flows 🧚

IP OAM protocols are used to detect failures (for example, BFD [RFC5880]) and performance degradation (for example, STAMP [RFC8762]) that affect an IP DetNet flow 🔍. For active OAM to be useful, it's essential that specially built OAM packets traverse the same set of nodes and links, and get the same network QoS treatment, as the monitored data flow (like a DetNet flow) 💅.

When the UDP destination port number used by the OAM protocol is assigned by IANA, picking the UDP source port carefully may help the OAM traffic be co-routed with the monitored IP DetNet flow in multipath environments, like Link Aggregation Group or Equal Cost Multipath 🛤️. The trick is using a UDP source port value that makes the OAM traffic and the monitored IP DetNet flow hash to the same path, based on the packet header hashes used for path selection 🌈. Just know this assumes forwarding equipment along the multipath makes consistent hashing decisions, which might not always be true in a heterogeneous environment 🙈. (That also applies to the encapsulation techniques in Sections 3.2 and 3.3 🎀.)

For accurate OAM results when detecting failures and monitoring IP DetNet performance, it's essential that test packets not only follow the same path as the monitored IP DetNet flow, but also get the same treatment from the nodes 👑. That treatment includes shaping, filtering, policing, and the availability of pre-allocated resources, just like the real IP DetNet packet experiences 💖. You can make that correlation between the particular IP OAM session and the monitored IP DetNet flow using DetNet provisioning information, for example [RFC9633] 🧚. Each IP OAM protocol session is presented as a DetNet application with related service and forwarding sub-layers 🦋. The forwarding sub-layer of the IP OAM session is identical to the forwarding sub-layer of the monitored IP DetNet flow, except for the information in the "ip-header" grouping item as defined in [RFC9633] 🌈.

3.2. Active OAM Using IP-in-UDP Encapsulation 🧚

okay so as we said, active IP OAM is done through several protocols 🩺. Some use UDP transport, while ICMP is a network-layer protocol 🌸. The operational work of mapping IP OAM protocols to the monitored DetNet flow can be reduced by using an IP/UDP tunnel [RFC2003] to carry IP test packets 🎀. Then, to make sure OAM packets traverse the same set of nodes and links, the IP/UDP tunnel must be mapped to the monitored DetNet flow 💜.

Note that in this case, the DetNet domain for the test packet looks like a single IP link 🙈. So transit DetNet IP nodes can't be traced with the usual traceroute procedure, and you may need to modify traceroute 🛠️. Plot twist, bestie, but that's the tea 🫖.

To be continued in part 2 🌷✨. Stay tuned, bestie 💖.

3.3. Active OAM Using DetNet-in-UDP Encapsulation

okay so active OAM in IP DetNet can be done with DetNet-in-UDP encapsulation 🎀 and bestie, this is lowkey genius because the tunnel makes sure your OAM test packets take the exact same path through the network as the IP DetNet flow packets they're monitoring 🛣️✨. They also get the same forwarding treatment in the DetNet forwarding sub-layer (see Section 4.1.2 of [RFC8655]) as the flow being watched, so they're literally living the same life 💅.

[RFC9566] explains how DetNet with the MPLS-over-UDP/IP data plane [RFC9025] can support Packet Replication, Elimination, and Ordering Functions (PREOF) 🌈. The vibe is that these can potentially lower packet loss, improve the odds of on-time delivery, and make sure packets arrive in order in the IP DetNet service sub-layer 📦. So to make sure an active OAM test packet follows the path of the monitored DetNet flow in the DetNet service sub-layer, the encapsulation in Figure 1 gets used 🧚.

     +---------------------------------+
     |                                 |
     |         DetNet App-Flow         |
     |       (original IP) Packet      |
     |                                 |
     +---------------------------------+ <--\
     |            DetNet ACH           |    |
     +---------------------------------+    +--> PREOF-capable
     |       Service-ID (S-Label)      |    |    DetNet IP data
     +---------------------------------+    |    plane encapsulation
     |            UDP Header           |    |
     +---------------------------------+    |
     |            IP Header            |    |
     +---------------------------------+ <--/
     |            Data-Link            |
     +---------------------------------+
     |             Physical            |
     +---------------------------------+

         Figure 1: DetNet Associated Channel Header Format

DetNet ACH: the DetNet Associated Channel Header, as defined in [RFC9546] 🦋.
PREOF: Packet Replication, Elimination, and Ordering Functions used in the DetNet service sub-layer, as defined in [RFC8655] 🫶.

3.4. The Application of Y.1731/G.8013 Using GRE-in-UDP Encapsulation

[RFC8086] defined a way to put GRE (Generic Routing Encapsulation) headers inside UDP 🍓. GRE-in-UDP can be used for IP DetNet OAM because it makes it way easier to map an OAM test session to one particular IP DetNet flow, which is identified by an N-tuple 🔥. Once a GRE-in-UDP tunnel is matched to the monitored IP DetNet flow, you can use Y.1731/G.8013 [ITU.Y1731] as a full toolset for OAM 🧰. The Protocol Type field in the GRE header MUST be set to 0x8902, which IANA assigned to the IEEE 802.1ag Connectivity Fault Management (CFM) protocol / ITU-T Recommendation Y.1731 💜. Y.1731/G.8013 has everything IP DetNet OAM needs, namely continuity checks, one-way packet loss, and packet delay measurements ✨.

4. Active OAM for DetNet IP Interworking with OAM for Non-IP DetNet Domains

A domain where the IP data plane provides DetNet service could be paired with a Time-Sensitive Networking (TSN) network and a DetNet domain with the MPLS data plane to deliver end-to-end service 🌸. In those setups, detecting defects and monitoring performance with OAM is ESSENTIAL 😭. [RFC9546] names two OAM interworking models, peering and tunneling 👑. Interworking between DetNet domains with IP and MPLS data planes is analyzed in Section 4.2 of [RFC9546] 🧠. On top of that, the OAM interworking requirements and recommendations that apply between a DetNet domain with the MPLS data plane and an adjacent TSN network also apply between a DetNet domain with the IP data plane and an adjacent TSN network 💖.

5. IANA Considerations

This document has no IANA actions 🌷.

6. Security Considerations

okay this part is serious bestie 💀 This document describes how the existing Fault Management and Performance Monitoring IP OAM protocols apply here 🔐. It does not raise any security concerns or issues beyond those common to networking or already documented in [RFC0792], [RFC4443], [RFC5880], and [RFC8762] for the referenced DetNet and OAM protocols 🚨.

7. References

7.1. Normative References

[RFC0792]  Postel, J., "Internet Control Message Protocol", STD 5,
           RFC 792, DOI 10.17487/RFC0792, September 1981,
           <https://www.rfc-editor.org/info/rfc792>.

[RFC2003]  Perkins, C., "IP Encapsulation within IP", RFC 2003,
           DOI 10.17487/RFC2003, October 1996,
           <https://www.rfc-editor.org/info/rfc2003>.

[RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
           Control Message Protocol (ICMPv6) for the Internet
           Protocol Version 6 (IPv6) Specification", STD 89,
           RFC 4443, DOI 10.17487/RFC4443, March 2006,
           <https://www.rfc-editor.org/info/rfc4443>.

[RFC8086]  Yong, L., Ed., Crabbe, E., Xu, X., and T. Herbert, "GRE-
           in-UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086,
           March 2017, <https://www.rfc-editor.org/info/rfc8086>.

[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>.

[RFC8939]  Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S.
           Bryant, "Deterministic Networking (DetNet) Data Plane:
           IP", RFC 8939, DOI 10.17487/RFC8939, November 2020,
           <https://www.rfc-editor.org/info/rfc8939>.

[RFC9025]  Varga, B., Ed., Farkas, J., Berger, L., Malis, A., and S.
           Bryant, "Deterministic Networking (DetNet) Data Plane:
           MPLS over UDP/IP", RFC 9025, DOI 10.17487/RFC9025, April
           2021, <https://www.rfc-editor.org/info/rfc9025>.

[RFC9546]  Mirsky, G., Chen, M., and B. Varga, "Operations,
           Administration, and Maintenance (OAM) for Deterministic
           Networking (DetNet) with the MPLS Data Plane", RFC 9546,
           DOI 10.17487/RFC9546, February 2024,
           <https://www.rfc-editor.org/info/rfc9546>.

[RFC9633]  Geng, X., Ryoo, Y., Fedyk, D., Rahman, R., and Z. Li,
           "Deterministic Networking (DetNet) YANG Data Model",
           RFC 9633, DOI 10.17487/RFC9633, October 2024,
           <https://www.rfc-editor.org/info/rfc9633>.

7.2. Informative References

[ITU.Y1731]
           ITU-T, "Operation, administration and maintenance (OAM)
           functions and mechanisms for Ethernet-based networks",
           ITU-T Recommendation G.8013/Y.1731, June 2023.

[RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
           (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
           <https://www.rfc-editor.org/info/rfc5880>.

[RFC5883]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
           (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,
           June 2010, <https://www.rfc-editor.org/info/rfc5883>.

[RFC7799]  Morton, A., "Active and Passive Metrics and Methods (with
           Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
           May 2016, <https://www.rfc-editor.org/info/rfc7799>.

[RFC8762]  Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple
           Two-Way Active Measurement Protocol", RFC 8762,
           DOI 10.17487/RFC8762, March 2020,
           <https://www.rfc-editor.org/info/rfc8762>.

[RFC9551]  Mirsky, G., Theoleyre, F., Papadopoulos, G., Bernardos,
           CJ., Varga, B., and J. Farkas, "Framework of Operations,
           Administration, and Maintenance (OAM) for Deterministic
           Networking (DetNet)", RFC 9551, DOI 10.17487/RFC9551,
           March 2024, <https://www.rfc-editor.org/info/rfc9551>.

[RFC9566]  Varga, B., Farkas, J., and A. Malis, "Deterministic
           Networking (DetNet) Packet Replication, Elimination, and
           Ordering Functions (PREOF) via MPLS over UDP/IP",
           RFC 9566, DOI 10.17487/RFC9566, April 2024,
           <https://www.rfc-editor.org/info/rfc9566>.

Authors' Addresses

Greg Mirsky
Ericsson
Email: gregimirsky@gmail.com


Mach(Guoyi) Chen
Huawei
Email: mach.chen@huawei.com


David Black
Dell EMC
176 South Street
Hopkinton, MA 01748
United States of America
Email: david.black@dell.com

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