< draft-ietf-raw-oam-support-02.txt   draft-ietf-raw-oam-support-03.txt >
RAW F. Theoleyre RAW F. Theoleyre
Internet-Draft CNRS Internet-Draft CNRS
Updates: draft-ietf-raw-oam-support-01 G. Papadopoulos Intended status: Informational G.Z. Papadopoulos
(if approved) IMT Atlantique Expires: 21 July 2022 IMT Atlantique
Intended status: Informational G. Mirsky G. Mirsky
Expires: December 5, 2021 ZTE Corp. Ericsson
CJ. Bernardos CJ. Bernardos
UC3M UC3M
June 3, 2021 17 January 2022
Operations, Administration and Maintenance (OAM) features for RAW Operations, Administration and Maintenance (OAM) features for RAW
draft-ietf-raw-oam-support-02 draft-ietf-raw-oam-support-03
Abstract Abstract
Some critical applications may use a wireless infrastructure. Some critical applications may use a wireless infrastructure.
However, wireless networks exhibit a bandwidth of several orders of However, wireless networks exhibit a bandwidth of several orders of
magnitude lower than wired networks. Besides, wireless transmissions magnitude lower than wired networks. Besides, wireless transmissions
are lossy by nature; the probability that a packet cannot be decoded are lossy by nature; the probability that a packet cannot be decoded
correctly by the receiver may be quite high. In these conditions, correctly by the receiver may be quite high. In these conditions,
providing high reliability and a low delay is challenging. This providing high reliability and a low delay is challenging. This
document lists the requirements of the Operation, Administration, and document lists the requirements of the Operation, Administration, and
Maintenance (OAM) features recommended to construct a predictable Maintenance (OAM) features are recommended to construct a predictable
communication infrastructure on top of a collection of wireless communication infrastructure on top of a collection of wireless
segments. This document describes the benefits, problems, and trade- segments. This document describes the benefits, problems, and trade-
offs for using OAM in wireless networks to achieve Service Level offs for using OAM in wireless networks to achieve Service Level
Objectives (SLO). Objectives (SLO).
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 5, 2021. This Internet-Draft will expire on 21 July 2022.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Requirements Language . . . . . . . . . . . . . . . . . . 6 1.3. Requirements Language . . . . . . . . . . . . . . . . . . 6
2. Role of OAM in RAW . . . . . . . . . . . . . . . . . . . . . 6 2. Role of OAM in RAW . . . . . . . . . . . . . . . . . . . . . 6
2.1. Link concept and quality . . . . . . . . . . . . . . . . 7 2.1. Link concept and quality . . . . . . . . . . . . . . . . 7
2.2. Broadcast Transmissions . . . . . . . . . . . . . . . . . 7 2.2. Broadcast Transmissions . . . . . . . . . . . . . . . . . 8
2.3. Complex Layer 2 Forwarding . . . . . . . . . . . . . . . 8 2.3. Complex Layer 2 Forwarding . . . . . . . . . . . . . . . 8
2.4. End-to-end delay . . . . . . . . . . . . . . . . . . . . 8 2.4. End-to-end delay . . . . . . . . . . . . . . . . . . . . 8
3. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Information Collection . . . . . . . . . . . . . . . . . 8 3.1. Information Collection . . . . . . . . . . . . . . . . . 9
3.2. Continuity Check . . . . . . . . . . . . . . . . . . . . 9 3.2. Continuity Check . . . . . . . . . . . . . . . . . . . . 9
3.3. Connectivity Verification . . . . . . . . . . . . . . . . 9 3.3. Connectivity Verification . . . . . . . . . . . . . . . . 9
3.4. Route Tracing . . . . . . . . . . . . . . . . . . . . . . 9 3.4. Route Tracing . . . . . . . . . . . . . . . . . . . . . . 9
3.5. Fault Verification/detection . . . . . . . . . . . . . . 10 3.5. Fault Verification/detection . . . . . . . . . . . . . . 10
3.6. Fault Isolation/identification . . . . . . . . . . . . . 10 3.6. Fault Isolation/identification . . . . . . . . . . . . . 10
4. Administration . . . . . . . . . . . . . . . . . . . . . . . 10 4. Administration . . . . . . . . . . . . . . . . . . . . . . . 10
4.1. Worst-case metrics . . . . . . . . . . . . . . . . . . . 11 4.1. Worst-case metrics . . . . . . . . . . . . . . . . . . . 11
4.2. Efficient data retrieval . . . . . . . . . . . . . . . . 11 4.2. Efficient measurement retrieval (Passive OAM) . . . . . . 11
4.3. Reporting OAM packets to the source . . . . . . . . . . . 12 4.3. Reporting OAM packets to the source (Active OAM) . . . . 12
5. Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . 12 5. Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.1. Soft transition after reconfiguration . . . . . . . . . . 13 5.1. Soft transition after reconfiguration . . . . . . . . . . 13
5.2. Predictive maintenance . . . . . . . . . . . . . . . . . 13 5.2. Predictive maintenance . . . . . . . . . . . . . . . . . 13
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 6. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 13
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
9. Informative References . . . . . . . . . . . . . . . . . . . 14 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 10. Informative References . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
Reliable and Available Wireless (RAW) is an effort that extends Reliable and Available Wireless (RAW) is an effort that extends
DetNet to approach end-to-end deterministic performances over a DetNet to approach end-to-end deterministic performances over a
network that includes scheduled wireless segments. In wired network that includes scheduled wireless segments. In wired
networks, many approaches try to enable Quality of Service (QoS) by networks, many approaches try to enable Quality of Service (QoS) by
implementing traffic differentiation so that routers handle each type implementing traffic differentiation so that routers handle each type
of packets differently. However, this differentiated treatment was of packets differently. However, this differentiated treatment was
expensive for most applications. expensive for most applications.
Deterministic Networking (DetNet) [RFC8655] has proposed to provide a Deterministic Networking (DetNet) [RFC8655] has proposed to provide a
bounded end-to-end latency on top of the network infrastructure, bounded end-to-end latency on top of the network infrastructure,
comprising both Layer 2 bridged and Layer 3 routed segments. Their comprising both Layer 2 bridged and Layer 3 routed segments. Their
work encompasses the data plane, OAM, time synchronization, work encompasses the data plane, OAM, time synchronization,
management, control, and security aspects. management, control, and security aspects.
However, wireless networks create specific challenges. First of all, However, wireless networks create specific challenges. First of all,
radio bandwidth is significantly lower than for wired networks. In radio bandwidth is significantly lower than in wired networks. In
these conditions, the volume of signaling messages has to be very these conditions, the volume of signaling messages has to be very
limited. Even worse, wireless links are lossy: a Layer 2 limited. Even worse, wireless links are lossy: a Layer 2
transmission may or may not be decoded correctly by the receiver, transmission may or may not be decoded correctly by the receiver,
depending on a broad set of parameters. Thus, providing high depending on a broad set of parameters. Thus, providing high
reliability through wireless segments is particularly challenging. reliability through wireless segments is particularly challenging.
Wired networks rely on the concept of _links_. All the devices Wired networks rely on the concept of _links_. All the devices
attached to a link receive any transmission. The concept of a link attached to a link receive any transmission. The concept of a link
in wireless networks is somewhat different from what many are used to in wireless networks is somewhat different from what many are used to
in wireline networks. A receiver may or may not receive a in wireline networks. A receiver may or may not receive a
transmission, depending on the presence of a colliding transmission, transmission, depending on the presence of a colliding transmission,
the radio channel's quality, and the external interference. Besides, the radio channel's quality, and the external interference. Besides,
a wireless transmission is broadcast by nature: any _neighboring_ a wireless transmission is broadcast by nature: any _neighboring_
device may be able to decode it. This document includes detailed device may be able to decode it. This document includes detailed
information on what the implications for the OAM features are. information on the implications for the OAM features.
Last but not least, radio links present volatile characteristics. If Last but not least, radio links present volatile characteristics. If
the wireless networks use an unlicensed band, packet losses are not the wireless networks use an unlicensed band, packet losses are not
anymore temporally and spatially independent. Typically, links may anymore temporally and spatially independent. Typically, links may
exhibit a very bursty characteristic, where several consecutive exhibit a very bursty characteristic, where several consecutive
packets may be dropped, because of e.g. temporary external packets may be dropped because of, e.g., temporary external
interference. Thus, providing availability and reliability on top of interference. Thus, providing availability and reliability on top of
the wireless infrastructure requires specific Layer 3 mechanisms to the wireless infrastructure requires specific Layer 3 mechanisms to
counteract these bursty losses. counteract these bursty losses.
Operations, Administration, and Maintenance (OAM) Tools are of Operations, Administration, and Maintenance (OAM) Tools are of
primary importance for IP networks [RFC7276]. They define a toolset primary importance for IP networks [RFC7276]. They define a toolset
for fault detection, isolation, and performance measurement. for fault detection, isolation, and performance measurement.
The primary purpose of this document is to detail the specific The primary purpose of this document is to detail the specific
requirements of the OAM features recommended to construct a requirements of the OAM features recommended to construct a
skipping to change at page 4, line 21 skipping to change at page 4, line 21
1.1. Terminology 1.1. Terminology
In this document, the term OAM will be used according to its In this document, the term OAM will be used according to its
definition specified in [RFC6291]. We expect to implement an OAM definition specified in [RFC6291]. We expect to implement an OAM
framework in RAW networks to maintain a real-time view of the network framework in RAW networks to maintain a real-time view of the network
infrastructure, and its ability to respect the Service Level infrastructure, and its ability to respect the Service Level
Objectives (SLO), such as delay and reliability, assigned to each Objectives (SLO), such as delay and reliability, assigned to each
data flow. data flow.
We re-use here the same terminology as [detnet-oam]: We re-use here the same terminology as
[I-D.ietf-detnet-oam-framework]:
o OAM entity: a data flow to be monitored for defects and/or its * OAM entity: a data flow to be monitored for defects and/or its
performance metrics measured.; performance metrics measured.;
o Maintenance End Point (MEP): OAM devices crossed when entering/ * Test End Point (TEP): OAM devices crossed when entering/exiting
exiting the network. In RAW, it corresponds mostly to the source the network. In RAW, it corresponds mostly to the source or
or destination of a data flow. OAM message can be exchanged destination of a data flow. OAM message can be exchanged between
between two MEPs; two TEPs;
o Maintenance Intermediate endPoint (MIP): an OAM system along the * Monitoring endPoint (MonEP): an OAM system along the flow; a MonEP
flow; a MIP MAY respond to an OAM message generated by the MEP; MAY respond to an OAM message generated by the TEP;
o control/management/data plane: the control and management planes * control/management/data plane: the control and management planes
are used to configure and control the network (long-term). The are used to configure and control the network (long-term). The
data plane takes the individual decision. Relative to a data data plane takes the individual decision. Relative to a data
flow, the control and/or management plane can be out-of-band; flow, the control and/or management plane can be out-of-band;
o Active measurement methods (as defined in [RFC7799]) modify a * Active measurement methods (as defined in [RFC7799]) modify a
normal data flow by inserting novel fields, injecting specially normal data flow by inserting novel fields, injecting specially
constructed test packets [RFC2544]). It is critical for the constructed test packets [RFC2544]). It is critical for the
quality of information obtained using an active method that quality of information obtained using an active method that
generated test packets are in-band with the monitored data flow. generated test packets are in-band with the monitored data flow.
In other words, a test packet is required to cross the same In other words, a test packet is required to cross the same
network nodes and links and receive the same Quality of Service network nodes and links and receive the same Quality of Service
(QoS) treatment as a data packet. Active methods may implement (QoS) treatment as a data packet. Active methods may implement
one of these two strategies: one of these two strategies:
* In-band: control information follows the same path as the data - In-band: control information follows the same path as the data
packets. In other words, a failure in the data plane may packets. In other words, a failure in the data plane may
prevent the control information to reach the destination (e.g., prevent the control information from reaching the destination
end-device or controller). (e.g., end-device or controller).
* out-of-band: control information is sent separately from the - out-of-band: control information is sent separately from the
data packets. Thus, the behavior of control vs. data packets data packets. Thus, the behavior of control vs. data packets
may differ; may differ;
o Passive measurement methods [RFC7799] infer information by * Passive measurement methods [RFC7799] infer information by
observing unmodified existing flows. observing unmodified existing flows.
We also adopt the following terminology, which is particularly We also adopt the following terminology, which is particularly
relevant for RAW segments. relevant for RAW segments.
o piggybacking vs. dedicated control packets: control information * piggybacking vs. dedicated control packets: control information
may be encapsulated in specific (dedicated) control packets. may be encapsulated in specific (dedicated) control packets.
Alternatively, it may be piggybacked in existing data packets, Alternatively, it may be piggybacked in existing data packets,
when the MTU is larger than the actual packet length. when the MTU is larger than the actual packet length.
Piggybacking makes specifically sense in wireless networks, as the Piggybacking makes specifically sense in wireless networks, as the
cost (bandwidth and energy) is not linear with the packet size. cost (bandwidth and energy) is not linear with the packet size.
o router-over vs. mesh under: a control packet is either forwarded * router-over vs. mesh under: a control packet is either forwarded
directly to the layer-3 next hop (mesh under) or handled hop-by- directly to the layer-3 next hop (mesh under) or handled hop-by-
hop by each router. While the latter option consumes more hop by each router. While the latter option consumes more
resources, it allows to collect additionnal intermediary resources, it allows collecting additional intermediary
information, particularly relevant in wireless networks. information, particularly relevant in wireless networks.
o Defect: a temporary change in the network (e.g., a radio link * Defect: a temporary change in the network (e.g., a radio link
which is broken due to a mobile obstacle); which is broken due to a mobile obstacle);
o Fault: a definite change which may affect the network performance, * Fault: a definite change which may affect the network performance,
e.g., a node runs out of energy. e.g., a node runs out of energy.
o End-to-end delay: the time between the packet generation and its * End-to-end delay: the time between the packet generation and its
reception by the destination. reception by the destination.
1.2. Acronyms 1.2. Acronyms
OAM Operations, Administration, and Maintenance OAM Operations, Administration, and Maintenance
DetNet Deterministic Networking DetNet Deterministic Networking
PSE Path Selection Engine [I-D.pthubert-raw-architecture] PSE Path Selection Engine [I-D.pthubert-raw-architecture]
skipping to change at page 5, line 48 skipping to change at page 6, line 4
OAM Operations, Administration, and Maintenance OAM Operations, Administration, and Maintenance
DetNet Deterministic Networking DetNet Deterministic Networking
PSE Path Selection Engine [I-D.pthubert-raw-architecture] PSE Path Selection Engine [I-D.pthubert-raw-architecture]
QoS Quality of Service QoS Quality of Service
RAW Reliable and Available Wireless RAW Reliable and Available Wireless
SLO Service Level Objective SLO Service Level Objective
SNMP Simple Network Management Protocol SNMP Simple Network Management Protocol
SDN Software-Defined Network SDN Software-Defined Network
1.3. Requirements Language 1.3. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Role of OAM in RAW 2. Role of OAM in RAW
RAW networks expect to make the communications reliable and RAW networks expect to make the communications reliable and
predictable on top of a wireless network infrastructure. Most predictable over a wireless network infrastructure. Most critical
critical applications will define an SLO to be required for the data applications will define an SLO required for the data flows it
flows it generates. RAW considers network plane protocol elements generates. RAW considers network plane protocol elements such as OAM
such as OAM to improve the RAW operation at the service and the to improve the RAW operation at the service and the forwarding sub-
forwarding sub-layers. layers.
To respect strict guarantees, RAW relies on the Path Selection Engine To respect strict guarantees, RAW relies on the Path Selection Engine
(PSE) (as defined in [I-D.pthubert-raw-architecture] to monitor and (PSE) (as defined in [I-D.pthubert-raw-architecture] to monitor and
maintain the L3 network. A L2 scheduler may be used to allocate maintain the L3 network. An L2 scheduler may be used to allocate
transmission opportunities, based on the radio link characteristics, transmission opportunities, based on the radio link characteristics,
SLO of the flows, the number of packets to forward. The PSE exploits SLO of the flows, the number of packets to forward. The PSE exploits
the L2 ressources reserved by the scheduler, and organizes the L3 the L2 resources reserved by the scheduler and organizes the L3 paths
paths to introduce redundancy, fault tolerance, and create backup to introduce redundancy, fault tolerance and create backup paths.
paths. OAM represents the core of the pre-provisioning process by OAM represents the core of the pre-provisioning process by
supervising the network. It maintains maintains a global view of the supervising the network. It maintains a global view of the network
network resources, to detect defects, faults, over-provisionning, resources to detect defects, faults, over-provisioning, anomalies.
anomalies.
Fault-tolerance also assumes that multiple paths have to be Fault tolerance also assumes that multiple paths must be provisioned
provisioned so that an end-to-end circuit keeps on existing whatever so that an end-to-end circuit remains operational regardless of the
the conditions. The Packet Replication and Elimination Function conditions. The Packet Replication and Elimination Function
([PREF-draft]) on a node is typically controlled by the PSE. OAM ([I-D.thubert-bier-replication-elimination]) on a node is typically
mechanisms can be used to monitor that PREOF is working correctly on controlled by the PSE. OAM mechanisms can be used to monitor that
a node and within the domain. PREOF is working correctly on a node and within the domain.
To be energy-efficient, reserving some dedicated out-of-band To be energy-efficient, out-of-band OAM SHOULD only be used to report
resources for OAM seems idealistic, and only in-band solutions are aggregated statistics (e.g., counters, histograms) from the nodes
considered here. using, e.g., SNMP or Netconf/Restconf using YANG-based data models.
The out-of-band OAM flow MAY use a dedicated control and management
channel, dedicated for this purpose.
RAW supports both proactive and on-demand troubleshooting. RAW supports both proactive and on-demand troubleshooting.
Proactively, it is necessary to detect anomalies, to report defects, Proactively, it is necessary to detect anomalies, report defects, or
or to reduce over-provisionning if it is not required. However, on- reduce over-provisioning if it is not required. However, on-demand
demand may also be required to identify the cause of a specific may also be required to identify the cause of a specific defect.
defect. Indeed, some specific faults may only be detected with a Indeed, some specific faults may only be detected with a global,
global, detailed view of the network, which is too expensive to detailed view of the network, which is too expensive to acquire in
acquire in the normal operating mode. the normal operating mode.
The specific characteristics of RAW are discussed below. The specific characteristics of RAW are discussed below.
2.1. Link concept and quality 2.1. Link concept and quality
In wireless networks, a _link_ does not exist physically. A device In wireless networks, a _link_ does not exist physically. A device
has a set of *neighbors* that correspond to all the devices that have has a set of *neighbors* that correspond to all the devices that have
a non null probability of receiving correctly its packets. We make a a non-null probability of receiving its packets correctly. We make a
distinction between: distinction between:
o point-to-point (p2p) link with one transmitter and one receiver. * point-to-point (p2p) link with one transmitter and one receiver.
These links are used to transmit unicast packets. These links are used to transmit unicast packets.
o point-to-multipoint (p2m) link associates one transmitter and a * point-to-multipoint (p2mp) link associates one transmitter and a
collection of receivers. For instance, broadcast packets assume collection of receivers. For instance, broadcast packets assume
the existence of p2m links to avoid duplicating a broadcast packet the existence of p2mp links to avoid duplicating a broadcast
to reach each possible radio neighbor. packet to reach each possible radio neighbor.
In scheduled radio networks, p2m and p2p links are commonly not In scheduled radio networks, p2mp and p2p links are commonly not
scheduled simultaneously to save energy, and/or to reduce the number scheduled simultaneously to save energy and/or to reduce the number
of collisions. More precisely, only one part of the neighbors may of collisions. More precisely, only one part of the neighbors may
wake-up at a given instant. wake up at a given instant.
Anycast are used in p2m links to improve the reliability. A Anycast is used in p2mp links to improve the reliability. A
collection of receivers are scheduled to wake-up simutaneously, so collection of receivers are scheduled to wake up simultaneously, so
that the transmission fails only if none of the receivers is able to that the transmission fails only if none of the receivers can decode
decode the packet. the packet.
Each wireless link is associated with a link quality, often measured Each wireless link is associated with a link quality, often measured
as the Packet Delivery Ratio (PDR), i.e., the probability that the as the Packet Delivery Ratio (PDR), i.e., the probability that the
receiver can decode the packet correctly. It is worth noting that receiver can decode the packet correctly. It is worth noting that
this link quality depends on many criteria, such as the level of this link quality depends on many criteria, such as the level of
external interference, the presence of concurrent transmissions, or external interference, the presence of concurrent transmissions, or
the radio channel state. This link quality is even time-variant. the radio channel state. This link quality is even time-variant.
For p2m links, we have consequently a collection of PDR (one value For p2mp links, consequently, we have a collection of PDR (one value
per receiver). Other more sophisticated, aggregated metrics exist per receiver). Other more sophisticated, aggregated metrics exist
for these p2m links, such as [anycast-property] for these p2mp links, such as [anycast-property]
2.2. Broadcast Transmissions 2.2. Broadcast Transmissions
In modern switching networks, the unicast transmission is delivered The unicast transmission is delivered exclusively to the destination
uniquely to the destination. Wireless networks are much closer to in modern switching networks. Wireless networks are much closer to
the ancient *shared access* networks. Practically, unicast and the traditional *shared access* networks. Practically, unicast and
broadcast frames are handled similarly at the physical layer. The broadcast frames are handled similarly at the physical layer. The
link layer is just in charge of filtering the frames to discard link layer is just in charge of filtering the frames to discard
irrelevant receptions (e.g., different unicast MAC address). irrelevant receptions (e.g., different unicast MAC addresses).
However, contrary to wired networks, we cannot be sure that a packet However, contrary to wired networks, we cannot ensure that a packet
is received by *all* the devices attached to the Layer 2 segment. It is received by *all* the devices attached to the Layer 2 segment. It
depends on the radio channel state between the transmitter(s) and the depends on the radio channel state between the transmitter(s) and the
receiver(s). In particular, concurrent transmissions may be possible receiver(s). In particular, concurrent transmissions may be possible
or not, depending on the radio conditions (e.g., do the different or not, depending on the radio conditions (e.g., do the different
transmitters use a different radio channel or are they sufficiently transmitters use a different radio channel or are they sufficiently
spatially separated?) spatially separated?)
2.3. Complex Layer 2 Forwarding 2.3. Complex Layer 2 Forwarding
Multiple neighbors may receive a transmission. Thus, anycast Layer 2 Multiple neighbors may receive a transmission. Thus, anycast Layer 2
forwarding helps to maximize the reliability by assigning multiple forwarding helps to maximize reliability by assigning multiple
receivers to a single transmission. That way, the packet is lost receivers to a single transmission. That way, the packet is lost
only if *none* of the receivers decode it. Practically, it has been only if *none* of the receivers decode it. Practically, it has been
proven that different neighbors may exhibit very different radio proven that different neighbors may exhibit very different radio
conditions, and that reception independency may hold for some of them conditions, and that reception independence may hold for some of them
[anycast-property]. [anycast-property].
2.4. End-to-end delay 2.4. End-to-end delay
In a wireless network, additionnal transmissions opportunities are In a wireless network, additional transmissions opportunities are
provisionned to accomodate packet losses. Thus, the end-to-end delay provisioned to accommodate packet losses. Thus, the end-to-end delay
consists of: consists of:
o Transmission delay, which is fixed and depends mainly on the data * Transmission delay, which is fixed and depends mainly on the data
rate, and the presence or absence of an acknowledgement. rate, and the presence or absence of an acknowledgement.
o Residence time, corresponds to the buffering delay and depends on * Residence time, corresponds to the buffering delay and depends on
the schedule. To account for retransmisisons, the residence time the schedule. To account for retransmissions, the residence time
is equal to the difference between the time of last reception from is equal to the difference between the time of last reception from
the previous hop (among all the retransmisions) and the time of the previous hop (among all the retransmissions) and the time of
emission of the last retransmission. emission of the last retransmission.
3. Operation 3. Operation
OAM features will enable RAW with robust operation both for OAM features will enable RAW with robust operation both for
forwarding and routing purposes. forwarding and routing purposes.
3.1. Information Collection 3.1. Information Collection
The model to exchange information should be the same as for DetNet The model for exchanging information should be the same as for a
network, for the sake of inter-operability. YANG may typically DetNet network to ensure inter-operability. YANG may typically
fulfill this objective. fulfill this objective.
However, RAW networks imply specific constraints (e.g., low However, RAW networks imply specific constraints (e.g., low
bandwidth, packet losses, cost of medium access) that may require to bandwidth, packet losses, cost of medium access) that may require to
minimize the volume of information to collect. Thus, we discuss in minimize the volume of information to collect. Thus, we discuss in
Section 4.2 different ways to collect information, i.e., transfer Section 4.2 different ways to collect information, i.e., transfer the
physically the OAM information from the emitter to the receiver. OAM information physically from the emitter to the receiver. This
corresponds to passive OAM as defined in [RFC7799]
3.2. Continuity Check 3.2. Continuity Check
Similarly to DetNet, we need to verify that the source and the Similarly to DetNet, we need to verify that the source and the
destination are connected (at least one valid path exists) destination are connected (at least one valid path exists)
3.3. Connectivity Verification 3.3. Connectivity Verification
As in DetNet, we have to verify the absence of misconnection. We As in DetNet, we have to verify the absence of misconnection. We
focus here on the RAW specificities. focus here on the RAW specificities.
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3.4. Route Tracing 3.4. Route Tracing
Wireless networks are broadcast by nature: a radio transmission can Wireless networks are broadcast by nature: a radio transmission can
be decoded by any radio neighbor. In multihop wireless networks, be decoded by any radio neighbor. In multihop wireless networks,
several paths exist between two endpoints. In hub networks, a device several paths exist between two endpoints. In hub networks, a device
may be covered by several Access Points. We should choose the most may be covered by several Access Points. We should choose the most
efficient path or AP, concerning specifically the reliability, and efficient path or AP, concerning specifically the reliability, and
the delay. the delay.
Thus, multipath routing / multi-attachment can be considered to make Thus, multipath routing / multi-attachment can be viewed as making
the network fault-tolerant. Even better, we can exploit the the network more fault-tolerant. Even better, we can exploit the
broadcast nature of wireless networks to exploit: we may have broadcast nature of wireless networks: we may have multiple
multiple Maintenance Intermediate Endpoints (MIP) for each of this Monitoring Endpoints (MonEP) for each of these kinds of hop. While
kind of hop. While it may be reasonable in the multi-attachment it may be reasonable in the multi-attachment case, the complexity
case, the complexity quickly increases with the path length. Indeed, quickly increases with the path length. Indeed, each Maintenance
each Maintenance Intermediate Endpoint has several possible next hops Intermediate Endpoint has several possible next hops in the
in the forwarding plane. Thus, all the possible paths between two forwarding plane. Thus, all the possible paths between two
maintenance endpoints should be retrieved, which may quickly become maintenance endpoints should be retrieved, which may quickly become
intractable if we apply a naive approach. intractable if we apply a naive approach.
3.5. Fault Verification/detection 3.5. Fault Verification/detection
Wired networks tend to present stable performances. On the contrary, Wired networks tend to present stable performances. On the contrary,
wireless networks are time-variant. We must consequently make a wireless networks are time-variant. We must consequently make a
distinction between _normal_ evolutions and malfunction. distinction between normal evolutions and malfunction.
3.6. Fault Isolation/identification 3.6. Fault Isolation/identification
The network has isolated and identified the cause of the fault. The network has isolated and identified the cause of the fault.
While DetNet already expects to identify malfunctions, some problems While DetNet already expects to identify malfunctions, some problems
are specific to wireless networks. We must consequently collect are specific to wireless networks. We must consequently collect
metrics and implement algorithms tailored for wireless networking. metrics and implement algorithms tailored for wireless networking.
For instance, the decrease in the link quality may be caused by For instance, the decrease in the link quality may be caused by
several factors: external interference, obstacles, multipath fading, several factors: external interference, obstacles, multipath fading,
mobility. It it fundamental to be able to discriminate the different mobility. It is fundamental to be able to discriminate the different
causes to make the right decision. causes to make the right decision.
4. Administration 4. Administration
The RAW network has to expose a collection of metrics to support an The RAW network has to expose a collection of metrics to support an
operator making proper decisions, including: operator making proper decisions, including:
o Packet losses: the time-window average and maximum values of the * Packet losses: the time-window average and maximum values of the
number of packet losses have to be measured. Many critical number of packet losses have to be measured. Many critical
applications stop to work if a few consecutive packets are applications stop working if a few consecutive packets are
dropped; dropped;
o Received Signal Strength Indicator (RSSI) is a very common metric * Received Signal Strength Indicator (RSSI) is a very common metric
in wireless to denote the link quality. The radio chipset is in in wireless to denote the link quality. The radio chipset is in
charge of translating a received signal strength into a normalized charge of translating a received signal strength into a normalized
quality indicator; quality indicator;
o Delay: the time elapsed between a packet generation / enqueuing * Delay: the time elapsed between a packet generation / enqueuing
and its reception by the next hop; and its reception by the next hop;
o Buffer occupancy: the number of packets present in the buffer, for * Buffer occupancy: the number of packets present in the buffer, for
each of the existing flows. each of the existing flows.
o Battery lifetime: the expected remaining battery lifetime of the * Battery lifetime: the expected remaining battery lifetime of the
device. Since many RAW devices might be battery powered, this is device. Since many RAW devices might be battery-powered, this is
an important metric for an operator to take proper decisions. an important metric for an operator to make proper decisions.
o Mobility: if a device is known to be mobile, this might be * Mobility: if a device is known to be mobile, this might be
considered by an operator to take proper decisions. considered by an operator to take proper decisions.
These metrics should be collected per device, virtual circuit, and These metrics should be collected per device, virtual circuit, and
path, as detnet already does. However, we have to face in RAW to a path, as DetNet already does. However, in RAW, we have to deal with
finer granularity: them at a finer granularity:
o per radio channel to measure, e.g., the level of external * per radio channel to measure, e.g., the level of external
interference, and to be able to apply counter-measures (e.g., interference, and to be able to apply counter-measures (e.g.,
blacklisting). blacklisting).
o per physical radio technology / interface if a device has multiple * per physical radio technology / interface, if a device has
NIC. multiple NICs.
o per link to detect misbehaving link (assymetrical link, * per link to detect misbehaving link (asymmetrical link,
fluctuating quality). fluctuating quality).
o per resource block: a collision in the schedule is particularly * per resource block: a collision in the schedule is particularly
challenging to identify in radio networks with spectrum reuse. In challenging to identify in radio networks with spectrum reuse. In
particular, a collision may not be systematic (depending on the particular, a collision may not be systematic (depending on the
radio characteristics and the traffic profile). radio characteristics and the traffic profile).
4.1. Worst-case metrics 4.1. Worst-case metrics
RAW inherits the same requirements as DetNet: we need to know the RAW inherits the same requirements as DetNet: we need to know the
distribution of a collection of metrics. However, wireless networks distribution of a collection of metrics. However, wireless networks
are known to be highly variable. Changes may be frequent, and may are known to be highly variable. Changes may be frequent, and may
exhibit a periodical pattern. Collecting and analyzing this amount exhibit a periodical pattern. Collecting and analyzing this amount
of measurements is challenging. of measurements is challenging.
Wireless networks are known to be lossy, and RAW has to implement Wireless networks are known to be lossy, and RAW has to implement
strategies to improve reliability on top of unreliable links. strategies to improve reliability on top of unreliable links.
Reliability is typically achieved through Automatic Repeat Request Reliability is typically achieved through Automatic Repeat Request
(ARQ), and Forward Error Correction (FEC). Since the different flows (ARQ), and Forward Error Correction (FEC). Since the different flows
have not the same SLO, RAW must adjust the ARQ and FEC based on the don't have the same SLO, RAW must adjust the ARQ and FEC based on the
link and path characteristics. link and path characteristics.
4.2. Efficient data retrieval 4.2. Efficient measurement retrieval (Passive OAM)
We have to minimize the number of statistics / measurements to We have to minimize the number of statistics / measurements to
exchange: exchange:
o energy efficiency: low-power devices have to limit the volume of * energy efficiency: low-power devices have to limit the volume of
monitoring information since every bit consumes energy. monitoring information since every bit consumes energy.
o bandwidth: wireless networks exhibit a bandwidth significantly * bandwidth: wireless networks exhibit a bandwidth significantly
lower than wired, best-effort networks. lower than wired, best-effort networks.
o per-packet cost: it is often more expensive to send several * per-packet cost: it is often more expensive to send several
packets instead of combining them in a single link-layer frame. packets instead of combining them in a single link-layer frame.
In conclusion, we have to take care of power and bandwidth In conclusion, we have to take care of power and bandwidth
consumption. The following techniques aim to reduce the cost of such consumption. The following techniques aim to reduce the cost of such
maintenance: maintenance:
on-path collection: some control information is inserted in the * on-path collection: some control information is inserted in the
data packets if they do not fragment the packet (i.e., the MTU is data packets if they do not fragment the packet (i.e., the MTU is
not exceeded). Information Elements represent a standardized way not exceeded). Information Elements represent a standardized way
to handle such information. IP hop by hop extension headers may to handle such information. IP hop by hop extension headers may
help to collect metrics all along the path; help to collect metrics all along the path;
flags/fields: we have to set-up flags in the packets to monitor to * flags/fields: we have to set-up flags in the packets to monitor to
be able to monitor the forwarding process accurately. A sequence be able to monitor the forwarding process accurately. A sequence
number field may help to detect packet losses. Similarly, path number field may help to detect packet losses. Similarly, path
inference tools such as [ipath] insert additional information in inference tools such as [ipath] insert additional information in
the headers to identify the path followed by a packet a the headers to identify the path followed by a packet a
posteriori. posteriori.
hierarchical monitoring: localized and centralized mechanisms have * hierarchical monitoring: localized and centralized mechanisms have
to be combined together. Typically, a local mechanism should to be combined together. Typically, a local mechanism should
contiuously monitor a set of metrics and trigger distant OAM continuously monitor a set of metrics and trigger remote OAM
exchances only when a fault is detected (but possibly not exchanges only when a fault is detected (but possibly not
identified). For instance, local temporary defects must not identified). For instance, local temporary defects must not
trigger expensive OAM transmissions. Besides, the wireless trigger expensive OAM transmissions. Besides, the wireless
segments represent often the weakest parts of a path: the volume segments often represent the weakest parts of a path: the volume
of control information they produce has to be fixed accordingly. of control information they produce has to be fixed accordingly.
4.3. Reporting OAM packets to the source Several passive techniques can be combined. For instance, the DetNet
forwarding sublayer MAY combine In-band Network Telemetry (INT) with
P4, iOAM and iPath to compute and report different statistics in the
track (e.g., number of link-layer retransmissions, link reliability).
TODO: statistics are collected when a packet goes from the source to 4.3. Reporting OAM packets to the source (Active OAM)
the destination. However, it has to be also reported by the source.
Problem: resource may not be reserved bidirectionnaly. Even worse:
the inverse path may not exist.
Reporting everything exhaustively to the source may in most cases too The Test EndPoint will collect measurements from the OAM probes
exensive. Thus, devices may take local decisions when possible, and received in the monitored track. However, the aggregated statistics
receive end-to-end information when possible. must then be reported to the other Test Endpoint that injected the
probes. Unfortunately, the monitored track MAY be unidirectional.
In this case, the statistics have to be reported out-of-band
(through, e.g., a dedicated control or management channel).
It is worth noting that Active OAM and Passive OAM techniques are not
mutually exclusive. In particular, Active OAM is useful when a
statistic cannot be acquired accurately passively.
5. Maintenance 5. Maintenance
Maintenance needs to facilitate the maintenance (repairs and Maintenance needs to facilitate the maintenance (repairs and
upgrades). In wireless networks, repairs are expected to occur much upgrades). In wireless networks, repairs are expected to occur much
more frequently, since the link quality may be highly time-variant. more frequently, since the link quality may be highly time-variant.
Thus, maintenance represents a key feature for RAW. Thus, maintenance represents a key feature for RAW.
5.1. Soft transition after reconfiguration 5.1. Soft transition after reconfiguration
skipping to change at page 13, line 21 skipping to change at page 13, line 32
make a distinction between a metric that changed because of a legal make a distinction between a metric that changed because of a legal
network change (e.g., flow redirection) and an unexpected event network change (e.g., flow redirection) and an unexpected event
(e.g., a fault). (e.g., a fault).
5.2. Predictive maintenance 5.2. Predictive maintenance
RAW needs to implement self-optimization features. While the network RAW needs to implement self-optimization features. While the network
is configured to be fault-tolerant, a reconfiguration may be required is configured to be fault-tolerant, a reconfiguration may be required
to keep on respecting long-term objectives. Obviously, the network to keep on respecting long-term objectives. Obviously, the network
keeps on respecting the SLO after a node's crash, but a keeps on respecting the SLO after a node's crash, but a
reconfiguration is required to handle the future faults. In other reconfiguration is required to handle future faults. In other words,
words, the reconfiguration delay MUST be strictly smaller than the the reconfiguration delay MUST be strictly smaller than the inter-
inter-fault time. fault time.
The network must continuously retrieve the state of the network, to The network must continuously retrieve the state of the network, to
judge about the relevance of a reconfiguration, quantifying: judge about the relevance of a reconfiguration, quantifying:
the cost of the sub-optimality: resources may not be used * the cost of the sub-optimality: resources may not be used
optimally (e.g., a better path exists); optimally (e.g., a better path exists);
the reconfiguration cost: the controller needs to trigger some * the reconfiguration cost: the controller needs to trigger some
reconfigurations. For this transient period, resources may be reconfigurations. For this transient period, resources may be
twice reserved, and control packets have to be transmitted. twice reserved, and control packets have to be transmitted.
Thus, reconfiguration may only be triggered if the gain is Thus, reconfiguration may only be triggered if the gain is
significant. significant.
6. IANA Considerations 6. Requirements
This section lists requirements for OAM in a RAW domain:
1. Each Test and Monitoring Endpoint device MUST expose a list of
available metrics per track. It MUST at least provide the end-
to-end Packet Delivery Ratio, end-to-end latency, and Maximum
Consecutive Failures (MCF).
2. PREOF functions MUST guarantee order preservation in the
(sub)track.
3. OAM nodes MUST provide aggregated statistics to reduce the volume
of traffic for measurements. They MAY send a compressed
distribution of measurements, or MIN / MAX values over a time
interval.
4. Monitoring Endpoints SHOULD support route tracing with passive
OAM techniques.
7. IANA Considerations
This document has no actionable requirements for IANA. This section This document has no actionable requirements for IANA. This section
can be removed before the publication. can be removed before the publication.
7. Security Considerations 8. Security Considerations
This section will be expanded in future versions of the draft. This section will be expanded in future versions of the draft.
8. Acknowledgments 9. Acknowledgments
TBD TBD
9. Informative References 10. Informative References
[anycast-property] [anycast-property]
Teles Hermeto, R., Gallais, A., and F. Theoleyre, "Is Teles Hermeto, R., Gallais, A., and F. Theoleyre, "Is
Link-Layer Anycast Scheduling Relevant for IEEE Link-Layer Anycast Scheduling Relevant for IEEE
802.15.4-TSCH Networks?", 2019, 802.15.4-TSCH Networks?", 2019,
<https://doi.org/10.1109/LCNSymposium47956.2019.9000679>. <https://doi.org/10.1109/LCNSymposium47956.2019.9000679>.
[detnet-oam] [I-D.ietf-detnet-oam-framework]
Theoleyre, F., Papadopoulos, G. Z., Mirsky, G., and C. J. Mirsky, G., Theoleyre, F., Papadopoulos, G. Z., Bernardos,
Bernardos, "Operations, Administration and Maintenance C. J., Varga, B., and J. Farkas, "Framework of Operations,
(OAM) features for detnet", 2020, Administration and Maintenance (OAM) for Deterministic
<https://tools.ietf.org/html/draft-theoleyre-detnet-oam- Networking (DetNet)", Work in Progress, Internet-Draft,
support>. draft-ietf-detnet-oam-framework-05, 14 October 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-detnet-
oam-framework-05>.
[I-D.pthubert-raw-architecture] [I-D.pthubert-raw-architecture]
Thubert, P., Papadopoulos, G. Z., and R. Buddenberg, Thubert, P., Papadopoulos, G. Z., and L. Berger, "Reliable
"Reliable and Available Wireless Architecture/Framework", and Available Wireless Architecture/Framework", Work in
draft-pthubert-raw-architecture-05 (work in progress), Progress, Internet-Draft, draft-pthubert-raw-architecture-
November 2020. 09, 7 July 2021, <https://datatracker.ietf.org/doc/html/
draft-pthubert-raw-architecture-09>.
[I-D.thubert-bier-replication-elimination]
Thubert, P., Eckert, T., Brodard, Z., and H. Jiang, "BIER-
TE extensions for Packet Replication and Elimination
Function (PREF) and OAM", Work in Progress, Internet-
Draft, draft-thubert-bier-replication-elimination-03, 3
March 2018, <https://datatracker.ietf.org/doc/html/draft-
thubert-bier-replication-elimination-03>.
[ipath] Gao, Y., Dong, W., Chen, C., Bu, J., Wu, W., and X. Liu, [ipath] Gao, Y., Dong, W., Chen, C., Bu, J., Wu, W., and X. Liu,
"iPath: path inference in wireless sensor networks.", "iPath: path inference in wireless sensor networks.",
2016, <https://doi.org/10.1109/TNET.2014.2371459>. 2016, <https://doi.org/10.1109/TNET.2014.2371459>.
[PREF-draft]
Thubert, P., Eckert, T., Brodard, Z., and H. Jiang, "BIER-
TE extensions for Packet Replication and Elimination
Function (PREF) and OAM", 2018,
<https://tools.ietf.org/html/draft-thubert-bier-
replication-elimination>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for [RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544, Network Interconnect Devices", RFC 2544,
DOI 10.17487/RFC2544, March 1999, DOI 10.17487/RFC2544, March 1999,
<https://www.rfc-editor.org/info/rfc2544>. <https://www.rfc-editor.org/info/rfc2544>.
skipping to change at page 15, line 30 skipping to change at page 16, line 16
"Deterministic Networking Architecture", RFC 8655, "Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019, DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>. <https://www.rfc-editor.org/info/rfc8655>.
Authors' Addresses Authors' Addresses
Fabrice Theoleyre Fabrice Theoleyre
CNRS CNRS
Building B Building B
300 boulevard Sebastien Brant - CS 10413 300 boulevard Sebastien Brant - CS 10413
Illkirch - Strasbourg 67400 67400 Illkirch - Strasbourg
FRANCE France
Phone: +33 368 85 45 33 Phone: +33 368 85 45 33
Email: theoleyre@unistra.fr Email: fabrice.theoleyre@cnrs.fr
URI: http://www.theoleyre.eu URI: http://www.theoleyre.eu
Georgios Z. Papadopoulos Georgios Z. Papadopoulos
IMT Atlantique IMT Atlantique
Office B00 - 102A Office B00 - 102A
2 Rue de la Chataigneraie 2 Rue de la Chataigneraie
Cesson-Sevigne - Rennes 35510 35510 Cesson-Sevigne - Rennes
FRANCE France
Phone: +33 299 12 70 04 Phone: +33 299 12 70 04
Email: georgios.papadopoulos@imt-atlantique.fr Email: georgios.papadopoulos@imt-atlantique.fr
Greg Mirsky Greg Mirsky
ZTE Corp. Ericsson
Email: gregimirsky@gmail.com
Email: gregory.mirsky@ztetx.com
Carlos J. Bernardos Carlos J. Bernardos
Universidad Carlos III de Madrid Universidad Carlos III de Madrid
Av. Universidad, 30 Av. Universidad, 30
Leganes, Madrid 28911 28911 Leganes, Madrid
Spain Spain
Phone: +34 91624 6236 Phone: +34 91624 6236
Email: cjbc@it.uc3m.es Email: cjbc@it.uc3m.es
URI: http://www.it.uc3m.es/cjbc/ URI: http://www.it.uc3m.es/cjbc/
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