rfc9912v2.txt   rfc9912.txt 
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include Revised BSD License text as described in Section 4.e of the include Revised BSD License text as described in Section 4.e of the
Trust Legal Provisions and are provided without warranty as described Trust Legal Provisions and are provided without warranty as described
in the Revised BSD License. in the Revised BSD License.
Table of Contents Table of Contents
1. Introduction 1. Introduction
2. The RAW Problem 2. The RAW Problem
3. Terminology 3. Terminology
3.1. Abbreviations 3.1. Abbreviations
3.1.1. ARQ
3.1.2. FEC
3.1.3. HARQ
3.1.4. ETX
3.1.5. ISM
3.1.6. PER
3.1.7. PDR
3.1.8. RSSI
3.1.9. LQI
3.1.10. OAM
3.1.11. OODA
3.1.12. SNR
3.2. Link and Direction 3.2. Link and Direction
3.2.1. Flapping 3.2.1. Flapping
3.2.2. Uplink 3.2.2. Uplink
3.2.3. Downlink 3.2.3. Downlink
3.2.4. Downstream 3.2.4. Downstream
3.2.5. Upstream 3.2.5. Upstream
3.3. Path and Recovery Graphs 3.3. Path and Recovery Graphs
3.3.1. Path 3.3.1. Path
3.3.2. Recovery Graph 3.3.2. Recovery Graph
3.3.3. Forward and Crossing 3.3.3. Forward and Crossing
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generalized with protection path, which is the term mostly found in generalized with protection path, which is the term mostly found in
recent standards and used in this document. recent standards and used in this document.
RAW also reuses terminology defined for 6TiSCH in [6TiSCH-ARCHI] and RAW also reuses terminology defined for 6TiSCH in [6TiSCH-ARCHI] and
equates the 6TiSCH concept of a Track with that of a recovery graph. equates the 6TiSCH concept of a Track with that of a recovery graph.
3.1. Abbreviations 3.1. Abbreviations
RAW uses the following abbreviations. RAW uses the following abbreviations.
3.1.1. ARQ ARQ
Automatic Repeat Request. A well-known mechanism that enables an
Automatic Repeat Request. A well-known mechanism that enables an acknowledged transmission with retries to mitigate errors and
acknowledged transmission with retries to mitigate errors and loss. loss. ARQ may be implemented at various layers in a network. ARQ
ARQ may be implemented at various layers in a network. ARQ is is typically implemented per hop (not end to end) at Layer 2 in
typically implemented per hop (not end to end) at Layer 2 in wireless wireless networks. ARQ improves delivery on lossy wireless.
networks. ARQ improves delivery on lossy wireless. Additionally, Additionally, ARQ retransmission may be further limited by a
ARQ retransmission may be further limited by a bounded time to meet bounded time to meet end-to-end packet latency constraints.
end-to-end packet latency constraints. Additional details and Additional details and considerations for ARQ are detailed in
considerations for ARQ are detailed in [RFC3366]. [RFC3366].
3.1.2. FEC
Forward Error Correction. Adding redundant data to protect against a
partial loss without retries.
3.1.3. HARQ
Hybrid ARQ. A combination of FEC and ARQ.
3.1.4. ETX
Expected Transmission Count. A statistical metric that represents
the expected total number of packet transmissions (including
retransmissions) required to successfully deliver a packet along a
path, used by 6TiSCH [RFC6551].
3.1.5. ISM
Industrial, Scientific, and Medical. Refers to a group of radio
bands or parts of the radio spectrum (e.g., 2.4 GHz and 5 GHz) that
are internationally reserved for the use of radio frequency (RF)
energy intended for industrial, scientific, and medical requirements
(e.g., by microwaves, depth radars, and medical diathermy machines).
Cordless phones, Bluetooth and Low-Power Wireless Personal Area
Network (LoWPAN) devices, near-field communication (NFC) devices,
garage door openers, baby monitors, and Wi-Fi networks may all use
the ISM frequencies, although these low-power transmitters are not
considered to be ISM devices. In general, communications equipment
operating in ISM bands must tolerate any interference generated by
ISM applications, and users have no regulatory protection from ISM
device operation in these bands.
3.1.6. PER
Packet Error Rate. The ratio of the number of packets received in
error to the total number of transmitted packets. A packet is
considered to be in error if even a single bit within the packet is
received incorrectly.
3.1.7. PDR
Packet Delivery Ratio (PDR). The ratio of the number of successfully FEC
delivered data packets to the total number of packets transmitted Forward Error Correction. Adding redundant data to protect
from the sender to the receiver. against a partial loss without retries.
3.1.8. RSSI HARQ
Hybrid ARQ. A combination of FEC and ARQ.
Received Signal Strength Indication. Also known as "Energy Detection ETX
Level". A measure of the incoherent (raw) RF power in a channel. Expected Transmission Count. A statistical metric that represents
The RF power can come from any source: other transmitters using the the expected total number of packet transmissions (including
same technology, other radio technology using the same band, or retransmissions) required to successfully deliver a packet along a
background radiation. For a single hop, RSSI may be used for LQI. path, used by 6TiSCH [RFC6551].
3.1.9. LQI ISM
Industrial, Scientific, and Medical. Refers to a group of radio
bands or parts of the radio spectrum (e.g., 2.4 GHz and 5 GHz)
that are internationally reserved for the use of radio frequency
(RF) energy intended for industrial, scientific, and medical
requirements (e.g., by microwaves, depth radars, and medical
diathermy machines). Cordless phones, Bluetooth and Low-Power
Wireless Personal Area Network (LoWPAN) devices, near-field
communication (NFC) devices, garage door openers, baby monitors,
and Wi-Fi networks may all use the ISM frequencies, although these
low-power transmitters are not considered to be ISM devices. In
general, communications equipment operating in ISM bands must
tolerate any interference generated by ISM applications, and users
have no regulatory protection from ISM device operation in these
bands.
Link Quality Indicator. An indication of the quality of the data PER
packets received by the receiver. It is typically derived from Packet Error Rate. The ratio of the number of packets received in
packet error statistics, with the exact method depending on the error to the total number of transmitted packets. A packet is
network stack being used. LQI values may be exposed to the considered to be in error if even a single bit within the packet
Controller Plane for each individual hop or cumulated along segments. is received incorrectly.
Outgoing LQI values can be calculated from coherent (demodulated)
PER, RSSI, and incoming LQI values.
3.1.10. OAM PDR
Packet Delivery Ratio (PDR). The ratio of the number of
successfully delivered data packets to the total number of packets
transmitted from the sender to the receiver.
Operations, Administration, and Maintenance. Covers the processes, RSSI
activities, tools, and standards involved with operating, Received Signal Strength Indication. Also known as "Energy
administering, managing, and maintaining any system. This document Detection Level". A measure of the incoherent (raw) RF power in a
uses the term in conformance with "Guidelines for the Use of the channel. The RF power can come from any source: other
'OAM' Acronym in the IETF" [RFC6291], and the system observed by the transmitters using the same technology, other radio technology
RAW OAM is the recovery graph. using the same band, or background radiation. For a single hop,
RSSI may be used for LQI.
3.1.11. OODA LQI
Link Quality Indicator. An indication of the quality of the data
packets received by the receiver. It is typically derived from
packet error statistics, with the exact method depending on the
network stack being used. LQI values may be exposed to the
Controller Plane for each individual hop or cumulated along
segments. Outgoing LQI values can be calculated from coherent
(demodulated) PER, RSSI, and incoming LQI values.
Observe, Orient, Decide, Act. A generic formalism to represent the OAM
operational steps in a control loop. In the context of RAW, OODA is Operations, Administration, and Maintenance. Covers the
applied to network control and convergence; see Section 6.2 for more. processes, activities, tools, and standards involved with
operating, administering, managing, and maintaining any system.
This document uses the term in conformance with "Guidelines for
the Use of the 'OAM' Acronym in the IETF" [RFC6291], and the
system observed by the RAW OAM is the recovery graph.
3.1.12. SNR OODA
Observe, Orient, Decide, Act. A generic formalism to represent the
operational steps in a control loop. In the context of RAW, OODA
is applied to network control and convergence; see Section 6.2 for
more.
Signal-to-Noise Ratio. Also known as "S/N Ratio". A measure used in SNR
science and engineering that compares the level of a desired signal Signal-to-Noise Ratio. Also known as "S/N Ratio". A measure used
to the level of background noise. SNR is defined as the ratio of in science and engineering that compares the level of a desired
signal power to noise power, often expressed in decibels. signal to the level of background noise. SNR is defined as the
ratio of signal power to noise power, often expressed in decibels.
3.2. Link and Direction 3.2. Link and Direction
This document uses the following terms relating to links and This document uses the following terms relating to links and
direction in the context of RAW. direction in the context of RAW.
3.2.1. Flapping 3.2.1. Flapping
In the context of RAW, a link flaps when the reliability of the In the context of RAW, a link flaps when the reliability of the
wireless connectivity drops abruptly for a short period of time, wireless connectivity drops abruptly for a short period of time,
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within the recovery graph. within the recovery graph.
In DetNet [DetNet-ARCHI] terms, a recovery graph has the following In DetNet [DetNet-ARCHI] terms, a recovery graph has the following
properties: properties:
* A recovery graph is a Layer 3 abstraction built upon IP links * A recovery graph is a Layer 3 abstraction built upon IP links
between routers. A router may form multiple IP links over a between routers. A router may form multiple IP links over a
single radio interface. single radio interface.
* A recovery graph has one ingress and one egress node, which * A recovery graph has one ingress and one egress node, which
operate as DetNet Edge nodes. operate as DetNet edge nodes.
* A recovery graph is reversible, meaning that packets can be routed * A recovery graph is reversible, meaning that packets can be routed
against the flow of data packets, e.g., to carry OAM measurements against the flow of data packets, e.g., to carry OAM measurements
or control messages back to the ingress. or control messages back to the ingress.
* The vertices of a recovery graph are DetNet Relay nodes that * The vertices of a recovery graph are DetNet relay nodes that
operate at the DetNet Service sub-layer and provide the PREOF operate at the DetNet Service sub-layer and provide the PREOF
functions. functions.
* The topological edges of a recovery graph are strict sequences of * The topological edges of a recovery graph are strict sequences of
DetNet Transit nodes that operate at the DetNet forwarding sub- DetNet transit nodes that operate at the DetNet forwarding sub-
layer. layer.
Figure 2 illustrates the generic concept of a recovery graph, between Figure 2 illustrates the generic concept of a recovery graph, between
an ingress node and an egress node. The recovery graph is composed an ingress node and an egress node. The recovery graph is composed
of forward protection paths, forward segments, and crossing segments of forward protection paths, forward segments, and crossing segments
(see the definitions of those terms in the next sections). The (see the definitions of those terms in the next sections). The
recovery graph contains at least two protection paths: a main path recovery graph contains at least two protection paths: a main path
and a backup path. and a backup path.
------------------- forward direction ----------------------> ------------------- forward direction ---------------------->
a ==> b ==> C -=- F ==> G ==> h T1 a ==> b ==> C -=- F ==> G ==> h T1
/ \ / | \ / / \ / | \ /
I o n E -=- T2 I o n E -=- T2
\ / \ | / \ \ / \ | / \
p ==> q ==> R -=- T ==> U ==> v T3 p ==> q ==> R -=- T ==> U ==> v T3
I: Ingress I: Ingress
E: Egress E: Egress
T1, T2, T3: external targets T1, T2, T3: external targets
Uppercase: DetNet Relay nodes Uppercase: DetNet relay nodes
Lowercase: DetNet Transit nodes Lowercase: DetNet transit nodes
Figure 2: A Recovery Graph and Its Components Figure 2: A Recovery Graph and Its Components
Of note: Of note:
I ==> a ==> b ==> C: A forward segment to targets F and o I ==> a ==> b ==> C: A forward segment to targets F and o
C ==> o ==> T: A forward segment to target T (and/or U) C ==> o ==> T: A forward segment to target T (and/or U)
G | n | U: A crossing segment to targets G or U G | n | U: A crossing segment to targets G or U
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both directions, though a given packet may use the link in one both directions, though a given packet may use the link in one
direction only. A segment can be forward, in which case it is direction only. A segment can be forward, in which case it is
composed of forward links only, or it can be crossing, in which case composed of forward links only, or it can be crossing, in which case
it is composed of crossing links only. A protection path is always it is composed of crossing links only. A protection path is always
forward, meaning that it is composed of forward links and segments. forward, meaning that it is composed of forward links and segments.
3.3.4. Protection Path 3.3.4. Protection Path
A protection path is an end-to-end forward path between the ingress A protection path is an end-to-end forward path between the ingress
and egress nodes of a recovery graph. A protection path in a and egress nodes of a recovery graph. A protection path in a
recovery graph is expressed as a strict sequence of DetNet Relay recovery graph is expressed as a strict sequence of DetNet relay
nodes or as a loose sequence of DetNet Relay nodes that are joined by nodes or as a loose sequence of DetNet relay nodes that are joined by
segments in the recovery graph. Background information on the segments in the recovery graph. Background information on the
concepts related to protection paths can be found in [RFC4427] and concepts related to protection paths can be found in [RFC4427] and
[RFC6378]. [RFC6378].
3.3.5. Segment 3.3.5. Segment
A segment is a strict sequence of DetNet Transit nodes between two A segment is a strict sequence of DetNet transit nodes between two
DetNet Relay nodes; a segment of a recovery graph is composed DetNet relay nodes; a segment of a recovery graph is composed
topologically of two vertices of the recovery graph and one edge of topologically of two vertices of the recovery graph and one edge of
the recovery graph between those vertices. the recovery graph between those vertices.
3.4. Deterministic Networking 3.4. Deterministic Networking
This document reuses the terminology in Section 2 of [RFC8557] and This document reuses the terminology in Section 2 of [RFC8557] and
Section 4.1.2 of [DetNet-ARCHI] for deterministic networking and Section 4.1.2 of [DetNet-ARCHI] for deterministic networking and
deterministic networks. This document also uses the following terms. deterministic networks. This document also uses the following terms.
3.4.1. The DetNet Planes 3.4.1. The DetNet Planes
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between the reliability functions provided by the lower layer and the between the reliability functions provided by the lower layer and the
reliability functions provided by DetNet. That is, the LL API makes reliability functions provided by DetNet. That is, the LL API makes
cross-layer optimization possible for the reliability functions of cross-layer optimization possible for the reliability functions of
different layers depending on the actual exposure provided via the LL different layers depending on the actual exposure provided via the LL
API by the given RAW technology. The Dynamic Link Exchange Protocol API by the given RAW technology. The Dynamic Link Exchange Protocol
(DLEP) [DLEP] is an example of a protocol that can be used to (DLEP) [DLEP] is an example of a protocol that can be used to
implement the LL API. implement the LL API.
3.5. Reliability and Availability 3.5. Reliability and Availability
This document uses the following terms relating to reliability and In the context of the RAW work, reliability and availability are
availability in the context of the RAW work. defined as follows, along with the following other terms.
3.5.1. Service Level Agreement 3.5.1. Service Level Agreement
In the context of RAW, a Service Level Agreement (SLA) is a contract In the context of RAW, a Service Level Agreement (SLA) is a contract
between a provider (the network) and a client (the application flow) between a provider (the network) and a client (the application flow)
that defines measurable metrics such as latency boundaries, that defines measurable metrics such as latency boundaries,
consecutive losses, and Packet Delivery Ratio (PDR). consecutive losses, and Packet Delivery Ratio (PDR).
3.5.2. Service Level Objective 3.5.2. Service Level Objective
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+-----------------------+ +-----------------------+ +-----------------------+ +-----------------------+
| Lower layers | | Lower layers | | Lower layers | | Lower layers |
+-----------------------+ +-----------------------+ +-----------------------+ +-----------------------+
v ^ v ^
\_________________________/ \_________________________/
Figure 3: Extended DetNet Data Plane Protocol Stack Figure 3: Extended DetNet Data Plane Protocol Stack
5.1. The RAW Planes 5.1. The RAW Planes
The RAW nodes are DetNet Relay nodes that operate in the RAW Network The RAW nodes are DetNet relay nodes that operate in the RAW Network
Plane and are capable of additional diversity mechanisms and Plane and are capable of additional diversity mechanisms and
measurement functions related to the radio interface. RAW leverages measurement functions related to the radio interface. RAW leverages
an Operational Plane orientation function (that typically operates an Operational Plane orientation function (that typically operates
inside the ingress Edge nodes) to dynamically adapt the path of the inside the ingress edge nodes) to dynamically adapt the path of the
packets and optimize the resource usage. packets and optimize the resource usage.
In the case of centralized routing operations, the RAW Controller In the case of centralized routing operations, the RAW Controller
Plane Function (CPF) interacts with RAW nodes over a Southbound API. Plane Function (CPF) interacts with RAW nodes over a Southbound API.
It consumes data and information from the network and generates It consumes data and information from the network and generates
knowledge and wisdom to help steer the traffic optimally inside a knowledge and wisdom to help steer the traffic optimally inside a
recovery graph. recovery graph.
DetNet Routing DetNet Routing
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protocols such as Bidirectional Forwarding Detection (BFD) [RFC5880] protocols such as Bidirectional Forwarding Detection (BFD) [RFC5880]
and Simple Two-way Active Measurement Protocol (STAMP) [RFC8762], and Simple Two-way Active Measurement Protocol (STAMP) [RFC8762],
respectively, or via a control protocol exchange with the lower layer respectively, or via a control protocol exchange with the lower layer
(e.g., DLEP [DLEP]). It may then be processed and exported through (e.g., DLEP [DLEP]). It may then be processed and exported through
OAM messaging or via a YANG data model and exposed to the Controller OAM messaging or via a YANG data model and exposed to the Controller
Plane. Plane.
5.3. RAW and DetNet 5.3. RAW and DetNet
RAW leverages the DetNet forwarding sub-layer and requires the RAW leverages the DetNet forwarding sub-layer and requires the
support of OAM in DetNet Transit nodes (see Figure 3 of support of OAM in DetNet transit nodes (see Figure 3 of
[DetNet-ARCHI]) for the dynamic acquisition of link capacity and [DetNet-ARCHI]) for the dynamic acquisition of link capacity and
state to maintain a strict RAW service end to end over a DetNet state to maintain a strict RAW service end to end over a DetNet
Network. In turn, DetNet and thus RAW may benefit from or leverage Network. In turn, DetNet and thus RAW may benefit from or leverage
functionality such as that provided by TSN at the lower layers. functionality such as that provided by TSN at the lower layers.
RAW extends DetNet to improve the protection against link errors such RAW extends DetNet to improve the protection against link errors such
as transient flapping that are far more common in wireless links. as transient flapping that are far more common in wireless links.
Nevertheless, for the most part, the RAW methods are applicable to Nevertheless, for the most part, the RAW methods are applicable to
wired links as well, e.g., when energy savings are desirable and the wired links as well, e.g., when energy savings are desirable and the
available path diversity exceeds 1+1 linear redundancy. available path diversity exceeds 1+1 linear redundancy.
RAW adds sub-layer functions that operate in the DetNet Operational RAW adds sub-layer functions that operate in the DetNet Operational
Plane, which is part of the Network Plane. The RAW orientation Plane, which is part of the Network Plane. The RAW orientation
function may run only in the DetNet Edge nodes (ingress Edge node or function may run only in the DetNet edge nodes (ingress edge node or
End System), or it can also run in DetNet Relay nodes when the RAW End System), or it can also run in DetNet relay nodes when the RAW
operations are distributed along the recovery graph. The RAW Service operations are distributed along the recovery graph. The RAW Service
sub-layer includes the PLR, which decides the DetNet path for the sub-layer includes the PLR, which decides the DetNet path for the
future packets of a flow along the DetNet path, Maintenance End future packets of a flow along the DetNet path, Maintenance End
Points (MEPs) on edge nodes, and Maintenance Intermediate Points Points (MEPs) on edge nodes, and Maintenance Intermediate Points
(MIPs) within. The MEPs trigger, and learn from, OAM observations (MIPs) within. The MEPs trigger, and learn from, OAM observations
and feed the PLR for its next decision. and feed the PLR for its next decision.
As illustrated in Figure 5, RAW extends the DetNet Stack (see As illustrated in Figure 5, RAW extends the DetNet Stack (see
Figure 4 of [DetNet-ARCHI] and Figure 3) with additional Figure 4 of [DetNet-ARCHI] and Figure 3) with additional
functionality at the DetNet Service sub-layer for the actuation of functionality at the DetNet Service sub-layer for the actuation of
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can be used to push reliability and timing hints, like suggesting X can be used to push reliability and timing hints, like suggesting X
retries (min, max) within a time window or sending unicast (one next retries (min, max) within a time window or sending unicast (one next
hop) or multicast (for overhearing). In the other direction up the hop) or multicast (for overhearing). In the other direction up the
stack, the RAW PLR needs hints about the radio conditions such as L2 stack, the RAW PLR needs hints about the radio conditions such as L2
triggers (e.g., RSSI, LQI, or ETX) over all the wireless hops. triggers (e.g., RSSI, LQI, or ETX) over all the wireless hops.
RAW uses various OAM functionalities at the different layers. For RAW uses various OAM functionalities at the different layers. For
instance, the OAM function in the DetNet Service sub-layer may instance, the OAM function in the DetNet Service sub-layer may
perform Active and/or Hybrid OAM to estimate the link and path perform Active and/or Hybrid OAM to estimate the link and path
availability, either end to end or limited to a segment. The RAW availability, either end to end or limited to a segment. The RAW
functions may be present in the Service sub-layer in DetNet Edge and functions may be present in the Service sub-layer in DetNet edge and
Relay nodes. relay nodes.
+-----------------+ +-------------------+ +-----------------+ +-------------------+
| Routing | | OAM Control | | Routing | | OAM Control |
+-----------------+ +-------------------+ +-----------------+ +-------------------+
Controller Plane Controller Plane
+-+-+-+-+-+-+-+-+ Southbound Interface -+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ Southbound Interface -+-+-+-+-+-+-+-+-+-+-+-+
Network Plane Network Plane
| |
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| Repair (PLR) | | End Point (MEP) | . | Repair (PLR) | | End Point (MEP) | .
+-----------------+ +-------------------+ | +-----------------+ +-------------------+ |
. .
| |
Figure 5: RAW Function Placement (Centralized Routing Case) Figure 5: RAW Function Placement (Centralized Routing Case)
There are two main proposed models to deploy RAW and DetNet: strict There are two main proposed models to deploy RAW and DetNet: strict
(Figure 6) and loose (Figure 7). In the strict model, illustrated in (Figure 6) and loose (Figure 7). In the strict model, illustrated in
Figure 6, RAW operates over a continuous DetNet service end to end Figure 6, RAW operates over a continuous DetNet service end to end
between the ingress and the egress Edge nodes or End Systems. between the ingress and the egress edge nodes or End Systems.
In the loose model, illustrated in Figure 7, RAW may traverse a In the loose model, illustrated in Figure 7, RAW may traverse a
section of the network that is not serviced by DetNet. RAW OAM may section of the network that is not serviced by DetNet. RAW OAM may
observe the end-to-end traffic and make the best of the available observe the end-to-end traffic and make the best of the available
resources, but it may not expect the DetNet guarantees over all resources, but it may not expect the DetNet guarantees over all
paths. For instance, the packets between two wireless entities may paths. For instance, the packets between two wireless entities may
be relayed over a wired infrastructure, in which case RAW observes be relayed over a wired infrastructure, in which case RAW observes
and controls the transmission over the wireless first and last hops, and controls the transmission over the wireless first and last hops,
as well as end-to-end metrics such as latency, jitter, and delivery as well as end-to-end metrics such as latency, jitter, and delivery
ratio. This operation is loose since the structure and properties of ratio. This operation is loose since the structure and properties of
the wired infrastructure are ignored and may be either controlled by the wired infrastructure are ignored and may be either controlled by
other means such as DetNet/TSN or neglected in the face of the other means such as DetNet/TSN or neglected in the face of the
wireless hops. wireless hops.
A minimal forwarding sub-layer service is provided at all DetNet A minimal forwarding sub-layer service is provided at all DetNet
nodes to ensure that the OAM information flows. DetNet Relay nodes nodes to ensure that the OAM information flows. DetNet relay nodes
may or may not support RAW services, whereas the DetNet Edge nodes may or may not support RAW services, whereas the DetNet edge nodes
are required to support RAW in any case. DetNet guarantees, such as are required to support RAW in any case. DetNet guarantees, such as
bounded latency, are provided end to end. RAW extends the DetNet bounded latency, are provided end to end. RAW extends the DetNet
Service sub-layer to optimize the use of resources. Service sub-layer to optimize the use of resources.
--------------------Flow Direction----------------------------------> --------------------Flow Direction---------------------------------->
+---------+ +---------+
| RAW | | RAW |
| Control | | Control |
+---------+ +---------+ +---------+ +---------+ +---------+ +---------+
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Node Node Node Node
<------------------End-to-End DetNet Service-----------------------> <------------------End-to-End DetNet Service----------------------->
Figure 6: RAW over DetNet (Strict Model) Figure 6: RAW over DetNet (Strict Model)
In the loose model (illustrated in Figure 7), RAW operates over a In the loose model (illustrated in Figure 7), RAW operates over a
partial DetNet service where typically only the ingress and the partial DetNet service where typically only the ingress and the
egress End Systems support RAW. The DetNet domain may extend beyond egress End Systems support RAW. The DetNet domain may extend beyond
the ingress node, or there may be a DetNet domain starting at an the ingress node, or there may be a DetNet domain starting at an
ingress Edge node at the first hop after the End System. ingress edge node at the first hop after the End System.
In the loose model, RAW cannot observe the hops in the network, and In the loose model, RAW cannot observe the hops in the network, and
the path beyond the first hop is opaque; RAW can still observe the the path beyond the first hop is opaque; RAW can still observe the
end-to-end behavior and use Layer 3 measurements to decide whether to end-to-end behavior and use Layer 3 measurements to decide whether to
replicate a packet and select the first-hop interface(s). replicate a packet and select the first-hop interface(s).
--------------------Flow Direction----------------------------------> --------------------Flow Direction---------------------------------->
+---------+ +---------+
| RAW | | RAW |
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a full recovery graph or the DetNet path that is being used at this a full recovery graph or the DetNet path that is being used at this
time. As packets may be load balanced, replicated, eliminated, and/ time. As packets may be load balanced, replicated, eliminated, and/
or fragmented for Network Coding FEC, the RAW in-situ operation needs or fragmented for Network Coding FEC, the RAW in-situ operation needs
to be able to signal which operation occurred to an individual to be able to signal which operation occurred to an individual
packet. packet.
Active RAW OAM may be needed to observe the unused segments and Active RAW OAM may be needed to observe the unused segments and
evaluate the desirability of a rerouting decision. evaluate the desirability of a rerouting decision.
Finally, the RAW Service sub-layer Service Assurance may observe the Finally, the RAW Service sub-layer Service Assurance may observe the
individual PREOF operation of a DetNet Relay node to ensure that it individual PREOF operation of a DetNet relay node to ensure that it
is conforming; this might require injecting an OAM packet at an is conforming; this might require injecting an OAM packet at an
upstream point inside the recovery graph and extracting that packet upstream point inside the recovery graph and extracting that packet
at another point downstream before it reaches the egress. at another point downstream before it reaches the egress.
This observation feeds the RAW PLR that makes the decision on which This observation feeds the RAW PLR that makes the decision on which
path is used at which RAW node, for one packet or a small continuous path is used at which RAW node, for one packet or a small continuous
series of packets. series of packets.
In the case of end-to-end protection in a wireless mesh, the recovery In the case of end-to-end protection in a wireless mesh, the recovery
graph is strict and congruent with the path so all links are graph is strict and congruent with the path so all links are
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The recovery graph computation is out of scope, but RAW expects that The recovery graph computation is out of scope, but RAW expects that
the CPF that installs the recovery graph also provides related the CPF that installs the recovery graph also provides related
knowledge in the form of metadata about the links, segments, and knowledge in the form of metadata about the links, segments, and
possible DetNet paths. That metadata can be a pre-digested possible DetNet paths. That metadata can be a pre-digested
statistical model and may include prediction of future flaps and statistical model and may include prediction of future flaps and
packet loss, as well as recommended actions when that happens. packet loss, as well as recommended actions when that happens.
The metadata may include: The metadata may include:
* A set of pre-determined DetNet paths that are prepared to match * A set of pre-determined DetNet paths that are prepared to match
expected link-degradation profiles, so the DetNet Relay nodes can expected link-degradation profiles, so the DetNet relay nodes can
take reflex rerouting actions when facing a degradation that take reflex rerouting actions when facing a degradation that
matches one such profile; and matches one such profile; and
* Link-quality statistics history and pre-trained models (e.g., to * Link-quality statistics history and pre-trained models (e.g., to
predict the short-term variation of quality of the links in a predict the short-term variation of quality of the links in a
recovery graph). recovery graph).
The recovery graph is installed with measurable objectives that are The recovery graph is installed with measurable objectives that are
computed by the CPF to achieve the RAW SLA. The objectives can be computed by the CPF to achieve the RAW SLA. The objectives can be
expressed as any of the maximum number of packets lost in a row, expressed as any of the maximum number of packets lost in a row,
skipping to change at line 1693 skipping to change at line 1673
| | graphs to optimize | of protection paths | | | graphs to optimize | of protection paths |
| | globally | | | | globally | |
+===============+-------------------------+---------------------+ +===============+-------------------------+---------------------+
| Considered | Averaged, statistical, | Instantaneous | | Considered | Averaged, statistical, | Instantaneous |
| Metrics | shade of grey | values / boolean | | Metrics | shade of grey | values / boolean |
| | | condition | | | | condition |
+===============+-------------------------+---------------------+ +===============+-------------------------+---------------------+
Table 1: Centralized Decision Versus PLR Table 1: Centralized Decision Versus PLR
The PLR sits in the DetNet forwarding sub-layer of Edge and Relay The PLR sits in the DetNet forwarding sub-layer of edge and relay
nodes. The PLR operates on the packet flow, learning the recovery nodes. The PLR operates on the packet flow, learning the recovery
graph and path-selection information from the packet and possibly graph and path-selection information from the packet and possibly
making a local decision and retagging the packet to indicate so. On making a local decision and retagging the packet to indicate so. On
the other hand, the PLR interacts with the lower layers (through the other hand, the PLR interacts with the lower layers (through
triggers and DLEP) and with its peers (through OAM) to obtain up-to- triggers and DLEP) and with its peers (through OAM) to obtain up-to-
date information about its links and the quality of the overall date information about its links and the quality of the overall
recovery graph, respectively, as illustrated in Figure 11. recovery graph, respectively, as illustrated in Figure 11.
| |
Packet | going Packet | going
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