Internet DRAFT - draft-varga-detnet-service-sub-layer-oam
draft-varga-detnet-service-sub-layer-oam
DetNet B. Varga
Internet-Draft J. Farkas
Intended status: Informational G. Mirsky
Expires: 26 January 2023 Ericsson
25 July 2022
Deterministic Networking (DetNet): OAM Functions for The Service Sub-
Layer
draft-varga-detnet-service-sub-layer-oam-03
Abstract
Operation, Administration, and Maintenance (OAM) tools are essential
for a deterministic network. The DetNet architecture [RFC8655] has
defined two sub-layers: (1) DetNet service sub-layer and (2) DetNet
forwarding sub-layer. OAM mechanisms exist for the DetNet forwarding
sub-layer. Nonetheless, OAM for the service sub-layer might require
new extensions to the existing OAM protocols. This draft presents an
analysis of OAM procedures for the DetNet service sub-layer
functions.
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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This Internet-Draft will expire on 26 January 2023.
Copyright Notice
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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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Terms Used in This Document . . . . . . . . . . . . . . . 3
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
2.3. Requirements Language . . . . . . . . . . . . . . . . . . 4
3. DetNet Service Sub-layer OAM Challenges . . . . . . . . . . . 4
3.1. Illustrative example . . . . . . . . . . . . . . . . . . 4
3.2. DetNet Service Sub-layer Specifics for OAM . . . . . . . 5
3.3. Information Needed during DetNet OAM Packet Processing . 6
3.4. A Possible Format of DetNet Associated Channel Header
(d-ACH) . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Requirements on OAM for DetNet Service Sub-layer . . . . . . 6
5. DetNet PING . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 7
5.2. OAM processing at the DetNet service sub-layer . . . . . 7
5.2.1. Relay node with PRF . . . . . . . . . . . . . . . . . 7
5.2.2. Relay node with PEF . . . . . . . . . . . . . . . . . 8
5.2.3. Relay node with POF . . . . . . . . . . . . . . . . . 9
5.2.4. Relay node without PREOF . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7.1. DetNet MPLS OAM Flags Registry . . . . . . . . . . . . . 10
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
The DetNet Working Group has defined two sub-layers: (1) DetNet
service sub-layer, at which a DetNet service (e.g., service
protection) is provided and (2) DetNet forwarding sub-layer, which
optionally provides resource allocation for DetNet flows over paths
provided by the underlying network. In [RFC8655] new DetNet-specific
functions have been defined for the DetNet service sub-layer, namely
PREOF (a collective name for Packet Replication, Elimination, and
Ordering Functions).
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Framework of Operations, Administration and Maintenance (OAM) for
Deterministic Networking (DetNet) is described in
[I-D.ietf-detnet-oam-framework]. OAM for the DetNet MPLS data plane
is described in [I-D.ietf-detnet-mpls-oam] and OAM for the DetNet IP
data plane is described in [I-D.ietf-detnet-mpls-oam].
This draft has been submitted as an individual contribution to OAM
discussions, in particular, to kick-off Working Group discussions on
introducing OAM functions for the DetNet service sub-layer. It is
also up to the Working Group discussions to which draft parts of this
contribution may go, if any.
The OAM functions for the DetNet service sub-layer allow, for
example, to recognize/discover DetNet relay nodes, to get information
about their configuration, and to check their operation or status.
Furthermore, the OAM functions for the DetNet service sub-layer need
to meet new challenges (see section Section 3) and requirements (see
section Section 4) introduced by PREOF.
An approach described in this draft introduces a new OAM shim layer
to achieve OAM for the DetNet service sub-layer. In the rest of the
draft, this approach is referred to as "DetNet PING", which is an in-
band OAM approach, i.e., the OAM packets follow precisely the same
path as the data packets of the corresponding DetNet flow(s) The OAM
packets provide DetNet service sub-layer specific information, like:
* Identity of a DetNet service sub-layer node.
* Discover Ingress/Egress flow-specific configuration of a DetNet
service sub-layer node.
* Detect the status of the flow-specific service sub-layer function.
DetNet PING applies both to IP and MPLS DetNet data planes.
2. Terminology
2.1. Terms Used in This Document
This document uses the terminology established in the DetNet
architecture [RFC8655], and 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.
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PEF Packet Elimination Function.
POF Packet Ordering Function.
PREOF Packet Replication, Elimination and Ordering Functions.
PRF Packet Replication Function.
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 Service Sub-layer OAM Challenges
3.1. Illustrative example
This section introduces an example that is used to explain the DetNet
Service Sub-layer OAM challenges. Figure 1 shows a DetNet flow on
which PREOF functions are applied during forwarding from source to
destination.
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<------------------------ App Flow ----------------------->
/-------------- DetNet domain -----------------/
<-------------- DetNet flow ----------------->
P6
P1 P4 +------------+
+--------------E1----+ | P7 |
+----+ | | +---R3---+ | P9 +----+
|src |------R1 +---+ | E3----O1---+ dst|
+----+ | P2 | P3 E2-------+ +----+
+----------R2 P5 | P8
+-----------------+
<----- P1 ----> <- P4 -> <--- P6 ----> <-P9->
<-- P2 --> <P3> <- P4 -> <P7> <- P8 -> <-P9->
<-- P2 --> <----- P5 ------> <- P8 -> <-P9->
|------------ G1 DetNet graph ---------------->
R: replication point (PRF) P: forwarding sub-layer path
E: elimination point (PEF) G: service sub-layer graph
O: ordering function (POF)
Figure 1: PREOF scenario in a DetNet network
DetNet service sub-layer nodes are interconnected by DetNet
forwarding sub-layer paths. DetNet forwarding sub-layer path (e.g.,
P1 = R1->E1 path, P4 = E1->R3 path) may contain multiple transit
nodes. A DetNet forwarding sub-layer path is used by a member flow
and terminated by relay nodes (see [RFC8655] for relay node
definition).
A DetNet service sub-layer graph includes all relay nodes and the
interconnecting forwarding sub-layer paths. This graph can be also
called as "PREOF graph" and it describes the compound flow as a
whole.
3.2. DetNet Service Sub-layer Specifics for OAM
Several DetNet Service Sub-layer specifics have to be considered for
OAM.
1. The service sub-layer graph is segmented into multiple parts, as
forwarding sub-layer paths are terminated at DetNet relay nodes.
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2. These are particular characteristics of DetNet PW:
1. PREOF acts as per-packet protection. PEF is a brand-new
functionality at network layer, due to the per-packet merge
action.
2. All paths are active and forward traffic. These paths may
have a different number of hops.
3. Mandatory usage of a sequence number.
The above specifics have to be considered in combination with the
requirement that DetNet OAM and DetNet data flows MUST receive the
same treatment. OAM packets MUST follow precisely the same graph as
the monitored DetNet flow(s).
3.3. Information Needed during DetNet OAM Packet Processing
This section collects some questions that have been already discussed
by the DetNet WG and/or require further discussions by the WG. The
section is structured in the form of a question list.
Question-1: Injecting OAM traffic in a DetNet flow? A DetNet data
flow has a continuous Sequence Number. In order not to spoil that,
the injected OAM packets require OAM-specific Sequence Number added.
(See also Section Section 5.)
Question-2: How to process OAM packets by DetNet service sub-layer
nodes? In order to cover the DetNet forwarding graph by OAM, PREOF
has to be executed in an OAM specific manner (i.e., PREOF uses a
separate SeqNum space for OAM. See details in Section 5.
Note: the question list is non-exhaustive.
3.4. A Possible Format of DetNet Associated Channel Header (d-ACH)
[Editor's note: The content of this section has been discussed and
the outcome of the discussion has been documented in
[I-D.ietf-detnet-mpls-oam].]
4. Requirements on OAM for DetNet Service Sub-layer
[Editor's note: The content of this section has been discussed and
the outcome of the discussion has been documented in
[I-D.ietf-detnet-oam-framework].]
5. DetNet PING
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5.1. Overview
The "DetNet PING" approach uses two types of OAM packets: (1) DetNet-
Echo-Request and (2) DetNet-Echo-Reply. Their encapsulation is
identical to that of the corresponding DetNet data flow, so they
follow precisely the same path as the packets of the corresponding
DetNet data flow. They target DetNet service sub-layer entities, so
they may not be recognized as OAM packets by entities not
implementing DetNet service sub-layer for a packet flow (e.g.,
transit nodes). Other entities treat them as packets belonging to
the corresponding DetNet data flow.
The following relay node roles can be distinguished:
1. DetNet PING originator node,
2. Intermediate DetNet service sub-layer node,
3. DetNet PING targeted node.
An originator node sends (generates) DetNet-Echo-Request packet(s).
DetNet-Echo-Request packet contains an OAM specific "PINGSeqNum",
which can be used by the DetNet service sub-layer of relay nodes.
Note that "PINGSeqNum" is originator specific.
An intermediate DetNet service sub-layer node executes DetNet flow-
specific service sub-layer functionality. Packet processing may be
done in an OAM specific manner (see details in Section 5.2).
A targeted node answers with DetNet-Echo-Reply packet for each
DetNet-Echo-Request. DetNet-Echo-Reply packet provides DetNet
service sub-layer specific information on (i) identities of DetNet
service sub-layer node (e.g., Node-ID, local Flow-ID), (ii) ingress/
egress flow related configuration (e.g., in/out member flow specific
information (including forwarding sub-layer specifics)), and (iii)
status of service sub-layer function (e.g., local PxF-ID, Action-
Type=x, operational status, value of key state variable(s), function
related counters).
5.2. OAM processing at the DetNet service sub-layer
Detailed OAM packet processing rules of various DetNet relay nodes
are described in the following sections.
5.2.1. Relay node with PRF
A DetNet relay node with PRF processes DetNet OAM packets in a
stateless manner.
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If the relay node with PRF is the target of a DetNet-Echo-Request
packet, then the DetNet-Echo-Request packet MUST NOT be further
forwarded, and a DetNet Echo-Reply packet MUST be generated. If the
relay node with PRF is not the target of a DetNet Echo-Request
packet, then the DetNet Echo-Request packet MUST be sent over all
DetNet flow specific member flow paths (i.e., it is replicated).
A DetNet Echo-Reply packet MUST contain the following information:
* Identities related to the DetNet service sub-layer node (e.g.,
Node-ID, local Flow-ID),
* Ingress/Egress flow related configuration (e.g., in/out member
flow specific information (including forwarding sub-layer
specifics)),
* Status of service sub-layer function (e.g., local PRF-ID, Action-
Type=Replication, operational status, value of the flow related
key state variable (e.g., "GenSeqNum" in [IEEE8021CB]).
A DetNet Echo-Reply packet MAY contain the following information:
* PRF related local counters.
5.2.2. Relay node with PEF
A DetNet relay node with PEF processes DetNet OAM packets in a
stateful manner.
If the relay node with PEF is the target of DetNet-Echo-Request
packet, then the DetNet Echo-Request packet MUST NOT be further
forwarded and an DetNet Echo-Reply packet MUST be generated. If the
relay node with PEF is not the target of DetNet Echo-Request packet,
then elimination MUST be executed on the DetNet Echo-Request
packet(s) using the OAM specific "PINGSeqNum" in the packet. So only
a single DetNet Echo-Request packet is forwarded and all further
replicas (having the same originator's sequence number) MUST be
discarded.
Note, PEF MAY use a simplified elimination algorithm for DetNet Echo-
Request packets (e.g., "MatchRecoveryAlgorithm" in [IEEE8021CB]) as
OAM is a slow protocol.
A DetNet-Echo-Reply packet MUST contain the following information:
* Identities related to the DetNet service sub-layer node (e.g.,
Node-ID, local Flow-ID),
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* Ingress/Egress flow related configuration (e.g., in/out member
flow specific information (including forwarding sub-layer
specifics)) ,
* Status of service sub-layer function (e.g., local PEF-ID, Action-
Type=Elimination, operational status, value of the flow related
key state variable (e.g., "RecovSeqNum" in [IEEE8021CB]).
A DetNet Echo-Reply packet MAY contain the following information:
* PEF-related local counters.
5.2.3. Relay node with POF
A DetNet relay node with POF processes DetNet OAM packets in a
stateless manner.
If the relay node with POF is the target of DetNet Echo-Request
packet, then the DetNet Echo-Request packet MUST NOT be further
forwarded and a DetNet Echo-Reply packet MUST be generated. If the
relay node with POF is not the target of DetNet-Echo-Request packet,
then the DetNet Echo-Request packet(s) MUST be forwarded without any
POF-specific action.
A DetNet Echo-Reply packet MUST contain the following information:
* Identities of the DetNet service sub-layer node (e.g., Node-ID,
local Flow-ID),
* Ingress/Egress flow related configuration (e.g., in/out member
flow specific information (including forwarding sub-layer
specifics)) ,
* Status of service sub-layer function (e.g., local POF-ID, Action-
Type=Ordering, operational status, value of the flow related key
state variable (e.g., "POFLastSent" in [I-D.varga-detnet-pof]).
A DetNet Echo-Reply packet MAY contain the following information:
* POF-related local counters.
5.2.4. Relay node without PREOF
A DetNet relay node without PREOF processes DetNet OAM packets in a
stateless manner.
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If the relay node without PREOF is the target of DetNet Echo-Request
packet, then the DetNet Echo-Request packet MUST NOT be further
forwarded and an DetNet Echo-Reply packet MUST be generated. If the
relay node without PREOF is not the target of DetNet-Echo-Request
packet, then the DetNet-Echo-Request packet(s) MUST be forwarded (as
any data packets of the related DetNet flow).
A DetNet Echo-Reply packet MUST contain the following information:
* Identities of the DetNet service sub-layer node (e.g., Node-ID,
local Flow-ID),
* Ingress/Egress flow-related configuration (e.g., in/out member
flow specific information (including forwarding sub-layer
specifics)) .
6. Security Considerations
Tbd.
7. IANA Considerations
7.1. DetNet MPLS OAM Flags Registry
[Editor's note: The content of this section has been discussed and
the outcome of the discussion has been documented in
[I-D.ietf-detnet-mpls-oam].]
8. Acknowledgements
Authors extend their appreciation to Janos Szabo and Gyorgy Miklos
for their insightful comments and productive discussion that helped
to improve the document.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", DOI 10.17487/RFC2119, BCP 14,
RFC 2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4928] Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal
Cost Multipath Treatment in MPLS Networks", BCP 128,
RFC 4928, DOI 10.17487/RFC4928, June 2007,
<https://www.rfc-editor.org/info/rfc4928>.
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[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", RFC 8126,
DOI 10.17487/RFC8126, BCP 26, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", DOI 10.17487/RFC8174, RFC 8174, BCP 14,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture",
DOI 10.17487/RFC8655, RFC 8655, 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>.
9.2. Informative References
[I-D.ietf-detnet-ip-oam]
Mirsky, G., Chen, M., and D. Black, "Operations,
Administration and Maintenance (OAM) for Deterministic
Networks (DetNet) with IP Data Plane", Work in Progress,
Internet-Draft, draft-ietf-detnet-ip-oam-04, February
2022, <https://www.ietf.org/archive/id/draft-ietf-detnet-
ip-oam-04.txt>.
[I-D.ietf-detnet-mpls-oam]
Mirsky, G., Chen, M., Varga, B., and J. Farkas,
"Operations, Administration and Maintenance (OAM) for
Deterministic Networks (DetNet) with MPLS Data Plane",
Work in Progress, Internet-Draft, draft-ietf-detnet-mpls-
oam-07, March 2022, <https://www.ietf.org/archive/id/
draft-ietf-detnet-mpls-oam-07.txt>.
[I-D.ietf-detnet-oam-framework]
Mirsky, G., Theoleyre, F., Papadopoulos, G. Z., Bernardos,
C. J., Varga, B., and J. Farkas, "Framework of Operations,
Administration and Maintenance (OAM) for Deterministic
Networking (DetNet)", Work in Progress, Internet-Draft,
draft-ietf-detnet-oam-framework-06, 13 June 2022,
<https://www.ietf.org/archive/id/draft-ietf-detnet-oam-
framework-06.txt>.
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[I-D.varga-detnet-pof]
Varga, B., Farkas, J., Kehrer, S., and T. Heer,
"Deterministic Networking (DetNet): Packet Ordering
Function", Work in Progress, Internet-Draft, draft-varga-
detnet-pof-03, 25 April 2022,
<https://www.ietf.org/archive/id/draft-varga-detnet-pof-
03.txt>.
[IEEE8021CB]
IEEE, "IEEE Standard for Local and metropolitan area
networks -- Frame Replication and Elimination for
Reliability", DOI 10.1109/IEEESTD.2017.8091139, October
2017,
<https://standards.ieee.org/standard/802_1CB-2017.html>.
Authors' Addresses
Balázs Varga
Ericsson
Budapest
Magyar Tudosok krt. 11.
1117
Hungary
Email: balazs.a.varga@ericsson.com
János Farkas
Ericsson
Budapest
Magyar Tudosok krt. 11.
1117
Hungary
Email: janos.farkas@ericsson.com
Greg Mirsky
Ericsson
Email: gregimirsky@gmail.com
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