Internet Engineering Task Force (IETF) G. Mirsky
Request for Comments: 9634 Ericsson
Category: Informational M. Chen
ISSN: 2070-1721 Huawei
D. Black
Dell EMC
August 2024
Operations, Administration, and Maintenance (OAM) for Deterministic
Networking (DetNet) with the IP Data Plane
Abstract
This document discusses the use of existing IP Operations,
Administration, and Maintenance protocols and mechanisms in
Deterministic Networking networks that use the IP data plane.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
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). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see 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/rfc9634.
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Table of Contents
1. Introduction
2. Conventions Used in This Document
2.1. Terminology
3. 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
4. Active OAM for DetNet IP Interworking with OAM for Non-IP
DetNet Domains
5. IANA Considerations
6. Security Considerations
7. References
7.1. Normative References
7.2. Informative References
Authors' Addresses
1. Introduction
[RFC8655] introduces and explains the Deterministic Networking
(DetNet) architecture.
Operations, Administration, and Maintenance (OAM) protocols are used
to detect and localize defects in the network as well as to monitor
network performance. Some OAM functions (e.g., failure detection)
work in the network proactively, while others (e.g., defect
localization) are usually performed on demand. These tasks are
achieved by a combination of active and hybrid OAM methods, as
defined in [RFC7799].
[RFC9551] lists the OAM functional requirements for DetNet and
defines the principles for OAM use within DetNet networks utilizing
the IP data plane. The functional requirements can be compared
against current OAM tools to identify gaps and potential enhancements
required to enable proactive and on-demand path monitoring and
service validation.
This document discusses the use of existing IP OAM protocols and
mechanisms in DetNet networks that use the IP data plane.
2. Conventions Used in This Document
2.1. Terminology
The term "DetNet OAM" as used in this document means "a set of OAM
protocols, methods, and tools for Deterministic Networking".
DetNet: Deterministic Networking
OAM: Operations, Administration, and Maintenance
ICMP: Internet Control Message Protocol
Underlay Network or Underlay Layer: The network that provides
connectivity between DetNet nodes. MPLS networks providing Label
Switched Path (LSP) connectivity between DetNet nodes are an
example of the DetNet IP network underlay layer.
DetNet Node: A node that is an actor in the DetNet domain. DetNet
domain edge nodes and nodes that perform the Packet Replication,
Elimination, and Ordering Functions within the domain are examples
of a DetNet node.
3. Active OAM for DetNet Networks with the IP Data Plane
OAM protocols and mechanisms act within the data plane of the
particular networking layer. Thus, it is critical that the data
plane encapsulation support OAM mechanisms and enable them to be
configured so that DetNet OAM packets follow the same path
(unidirectional or bidirectional) through the network and receive the
same forwarding treatment in the DetNet forwarding sub-layer as the
DetNet flow being monitored.
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 the ordered match to
the provisioned information set that, among other elements, includes
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 the well-known UDP
port numbers as the respective destination ports. For BFD, the UDP
destination port is specific to the BFD variant, e.g., multihop BFD
uses port 4784 [RFC5883].
Thus, a DetNet node must be able to associate an IP DetNet flow with
the particular test session to ensure that test packets experience
the same treatment as the DetNet flow packets. For example, in a
network where path selection and DetNet functionality are based on
3-tuples (destination and source IP addresses in combination with the
Differentiated Services Code Point value), that association can be
achieved by having the OAM traffic use the same 3-tuple as the
monitored IP DetNet flow. In such a scenario, an IP OAM session
between the same pair of IP nodes would share the network treatment
with the monitored IP DetNet flow regardless of whether ICMP, BFD, or
STAMP is used.
In IP networks, the majority of on-demand failure detection and
localization is achieved through the use of ICMP, utilizing Echo
Request and Echo Reply messages, along with a set of defined error
messages such as Destination Unreachable, which provide detailed
information through assigned code points. [RFC0792] and [RFC4443]
define ICMP for IPv4 and IPv6 networks, respectively. To utilize
ICMP effectively for these purposes within DetNet, DetNet nodes must
establish the association of ICMP traffic between DetNet nodes with
IP DetNet traffic. This entails ensuring that such ICMP traffic
traverses the same interfaces and receives QoS treatment that is
identical to the monitored DetNet IP flow. Failure to do so may
result in ICMP being unable to detect and localize failures specific
to the DetNet IP data plane.
3.1. Mapping Active OAM and IP DetNet Flows
IP OAM protocols are used to detect failures (e.g., BFD [RFC5880])
and performance degradation (e.g., STAMP [RFC8762]) that affect an IP
DetNet flow. For active OAM to be useful, it is essential to ensure
that specially constructed OAM packets traverse the same set of nodes
and links and receive the same network QoS treatment as the monitored
data flow, e.g., a DetNet flow. When the UDP destination port number
used by the OAM protocol is assigned by IANA, judicious selection of
the UDP source port may help achieve co-routedness of OAM with the
monitored IP DetNet flow in multipath environments, e.g., Link
Aggregation Group or Equal Cost Multipath, via the use of a UDP
source port value that results in the OAM traffic and the monitored
IP DetNet flow hashing to the same path based on the packet header
hashes used for path selection. This does assume that 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 described in
Sections 3.2 and 3.3.) To ensure the accuracy of OAM results in
detecting failures and monitoring the performance of IP DetNet, it is
essential that test packets not only traverse the same path as the
monitored IP DetNet flow but also receive the same treatment by the
nodes, e.g., shaping, filtering, policing, and availability of the
pre-allocated resources, as experienced by the IP DetNet packet.
That correlation between the particular IP OAM session and the
monitored IP DetNet flow can be achieved by using DetNet provisioning
information (e.g., [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 information in the "ip-header" grouping item as
defined in [RFC9633].
3.2. Active OAM Using IP-in-UDP Encapsulation
As described above, active IP OAM is realized through several
protocols. Some protocols use UDP transport, while ICMP is a
network-layer protocol. The amount of operational work 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 ensure
that 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
such a case, the DetNet domain for the test packet is seen as a
single IP link. As a result, transit DetNet IP nodes cannot be
traced using the usual traceroute procedure, and a modification of
the traceroute may be required.
3.3. Active OAM Using DetNet-in-UDP Encapsulation
Active OAM in IP DetNet can be realized using DetNet-in-UDP
encapsulation. Using a DetNet-in-UDP tunnel between IP DetNet nodes
ensures that active OAM test packets follow the same path through the
network as the monitored IP DetNet flow packets and receive the same
forwarding treatment in the DetNet forwarding sub-layer (see
Section 4.1.2 of [RFC8655]) as the IP DetNet flow being monitored.
[RFC9566] describes how DetNet with the MPLS-over-UDP/IP data plane
[RFC9025] can be used to support Packet Replication, Elimination, and
Ordering Functions (PREOF) to potentially lower packet loss, improve
the probability of on-time packet delivery, and ensure in-order
packet delivery in IP DetNet's service sub-layer. To ensure that an
active OAM test packet follows the path of the monitored DetNet flow
in the DetNet service sub-layer, the encapsulation shown in Figure 1
is 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
Where:
* DetNet ACH is - 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] has defined the method of encapsulating GRE (Generic
Routing Encapsulation) headers in UDP. GRE-in-UDP encapsulation can
be used for IP DetNet OAM, as it eases the task of mapping an OAM
test session to a particular IP DetNet flow that is identified by an
N-tuple. Matching a GRE-in-UDP tunnel to the monitored IP DetNet
flow enables the use of Y.1731/G.8013 [ITU.Y1731] as a comprehensive
toolset of OAM. The Protocol Type field in the GRE header must be
set to 0x8902, assigned by IANA to the IEEE 802.1ag Connectivity
Fault Management (CFM) protocol / ITU-T Recommendation Y.1731.
Y.1731/G.8013 supports the necessary functions required for IP DetNet
OAM, i.e., 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 in which the IP data plane provides DetNet service could be
used in conjunction with a Time-Sensitive Networking (TSN) network
and a DetNet domain with the MPLS data plane to deliver end-to-end
service. In such scenarios, the ability to detect defects and
monitor performance using OAM is essential. [RFC9546] identifies 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]. In addition, 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
This document describes the applicability of the existing Fault
Management and Performance Monitoring IP OAM protocols. It does not
raise any security concerns or issues in addition to 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, August 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