Reliable and Available Wireless Architecture/Framework
draft-pthubert-raw-architecture-03
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| Authors | Pascal Thubert , Georgios Z. Papadopoulos , Rex Buddenberg | ||
| Last updated | 2020-05-25 (Latest revision 2020-05-18) | ||
| Replaced by | draft-ietf-raw-architecture, draft-ietf-raw-architecture | ||
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draft-pthubert-raw-architecture-03
RAW P. Thubert, Ed.
Internet-Draft Cisco Systems
Intended status: Informational G.Z. Papadopoulos
Expires: 26 November 2020 IMT Atlantique
R. Buddenberg
25 May 2020
Reliable and Available Wireless Architecture/Framework
draft-pthubert-raw-architecture-03
Abstract
Due to uncontrolled interferences, including the self-induced
multipath fading, deterministic networking can only be approached on
wireless links. The radio conditions may change -way- faster than a
centralized routing can adapt and reprogram, in particular when the
controller is distant and connectivity is slow and limited. RAW
separates the routing time scale at which a complex path is
recomputed from the forwarding time scale at which the forwarding
decision is taken for an individual packet. RAW operates at the
forwarding time scale. The RAW problem is to decide, within the
redundant solutions that are proposed by the routing, which will be
used for each individual packet to provide a DetNet service while
minimizing the waste of resources.
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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and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 26 November 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Related Work at The IETF . . . . . . . . . . . . . . . . . . 6
4. Use Cases and Requirements Served . . . . . . . . . . . . . . 6
4.1. Radio Access Protection . . . . . . . . . . . . . . . . . 7
4.2. End-to-End Protection in a Wireless Mesh . . . . . . . . 8
5. RAW Considerations . . . . . . . . . . . . . . . . . . . . . 8
5.1. Reliability and Availability . . . . . . . . . . . . . . 8
5.1.1. High Availability Engineering Principles . . . . . . 8
5.1.2. Applying Reliability Concepts to Networking . . . . . 11
5.1.3. Reliability in the Context of RAW . . . . . . . . . . 11
5.2. RAW Scope and Prerequisites . . . . . . . . . . . . . . . 13
5.3. Routing Time Scale vs. Forwarding Time Scale . . . . . . 14
6. RAW Architecture Elements . . . . . . . . . . . . . . . . . . 15
6.1. Wireless Tracks . . . . . . . . . . . . . . . . . . . . . 15
6.2. PAREO Functions . . . . . . . . . . . . . . . . . . . . . 16
6.2.1. Packet Replication . . . . . . . . . . . . . . . . . 17
6.2.2. Packet Elimination . . . . . . . . . . . . . . . . . 18
6.2.3. Promiscuous Overhearing . . . . . . . . . . . . . . . 18
6.2.4. Constructive Interference . . . . . . . . . . . . . . 18
7. RAW Architecture . . . . . . . . . . . . . . . . . . . . . . 19
7.1. PCE vs. PSE . . . . . . . . . . . . . . . . . . . . . . . 20
7.2. RAW OAM . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.3. Source-Routed vs. Distributed Forwarding Decision . . . . 22
7.4. Flow Identification . . . . . . . . . . . . . . . . . . . 23
8. Security Considerations . . . . . . . . . . . . . . . . . . . 24
8.1. Forced Access . . . . . . . . . . . . . . . . . . . . . . 24
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
12.1. Normative References . . . . . . . . . . . . . . . . . . 24
12.2. Informative References . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
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1. Introduction
Bringing determinism in a packet network means eliminating the
statistical effects of multiplexing that result in probabilistic
jitter and loss. This can be approached with a tight control of the
physical resources to maintain the amount of traffic within a
budgetted volume of data per unit of time that fits the physical
capabilities of the underlying technology, and the use of time-shared
resources (bandwidth and buffers) per circuit, and/or by shaping and/
or scheduling the packets at every hop.
Wireless networks operate on a shared medium where uncontrolled
interference, including the self-induced multipath fading, adds
another dimension to the statistical effects that affect the
delivery. Scheduling transmissions can alleviate those effects by
leveraging diversity in the spatial, time, code, and frequency
domains, and provide a Reliable and Available Wireless (RAW) service
while preserving energy and optimizing the use of the shared
spectrum.
Deterministic Networking is an attempt to mostly eliminate packet
loss for a committed bandwidth with a guaranteed worst-case end-to-
end latency, even when co-existing with best-effort traffic in a
shared network. This innovation is enabled by recent developments in
technologies including IEEE 802.1 TSN (for Ethernet LANs) and IETF
DetNet (for wired IP networks). It is getting traction in various
industries including manufacturing, online gaming, professional A/V,
cellular radio and others, making possible many cost and performance
optimizations.
The "Deterministic Networking Architecture" [RFC8655] is composed of
three planes: the Application (User) Plane, the Controller Plane, and
the Network Plane. RAW extends DetNet to focus on issues that are
mostly a concern on wireless links, and inherits the architecture and
the planes. A RAW Network Plane is thus a Network Plane inherited by
RAW from DetNet, composed of one or multiple hops of homogeneous or
heterogeneous technologies, e.g. a Wi-Fi6 Mesh or one-hop CBRS access
links federated by a 5G backhaul.
RAW networking aims at providing highly available and reliable end-
to-end performances in a network with scheduled wireless segments.
Uncontrolled interference and transmission obstacles may impede the
transmission, and techniques such as beamforming with Multi-User MIMO
can only alleviate some of those issues, so the term "deterministic"
is usually not associated with short range radios, in particular in
the ISM band. This uncertainty places limits to the amount of
traffic that can be transmitted on a link while conforming to a RAW
Service Level Agreement (SLA) that may vary rapidly.
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The wireless and wired media are fundamentally different at the
physical level, and while the generic "Deterministic Networking
Problem Statement" [RFC8557] applies to both the wired and the
wireless media, the methods to achieve RAW must extend those used to
support time-sensitive networking over wires, as a RAW solution has
to address less consistent transmissions, energy conservation and
shared spectrum efficiency.
The development of RAW technologies has been lagging behind
deterministic efforts for wired systems both at the IEEE and the
IETF. But recent efforts at the IEEE and 3GPP indicate that wireless
is finally catching up at the lower layer and that it is now possible
for the IETF to extend DetNet for wireless segments that are capable
of scheduled wireless transmissions.
The intent for RAW is to provide DetNet elements that are specialized
for short range radios. From this inheritance, RAW stays agnostic to
the radio layer underneath though the capability to schedule
transmissions is assumed. How the PHY is programmed to do so, and
whether the radio is single-hop or meshed, are unknown at the IP
layer and not part of the RAW abstraction.
The establishment of a path is not in-scope for RAW. It may be the
product of a centralized Controller Plane as described for DetNet.
As opposed to wired networks, the action of installing a path over a
set of wireless links may be very slow relative to the speed at which
the radio conditions vary, and it makes sense in the wireless case to
provide redundant forwarding solutions along a complex path and to
leave it to the Network Plane to select which of those forwarding
solutions are to be used for a given packet based on the current
conditions.
RAW distinguishes the longer time scale at which routes are computed
from the the shorter forwarding time scale where per-packet decisions
are made. RAW operates within the Network Plane at the forwarding
time scale on one DetNet flow over a complex path called a Track.
The Track is preestablished and installed by means outside of the
scope of RAW; it may be strict or loose depending on whether each or
just a subset of the hops are observed and controlled by RAW.
The scope of the RAW WG comprises Network plane protocol elements
such as Operations, Administration and Maintenance (OAM) to observe
some or all hops along a Track, as well as the end-to-end packet
delivery, and in-band control to optimize the use of redundancy to
achieve the required SLA.
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2. Terminology
RAW reuses terminology defined for DetNet in the "Deterministic
Networking Architecture" [RFC8655], e.g., PREOF for Packet
Replication, Elimination and Ordering Functions.
RAW also reuses terminology defined for 6TiSCH in [6TiSCH-ARCHI] such
as the term Track. A Track as a complex path with associated PAREO
operations. The concept is abstract to the underlaying technology
and applies to any fully or partially wireless mesh, including, e.g.,
a Wi-Fi mesh. RAW specifies strict and loose Tracks depending on
whether the path is fully controlled by RAW or traverses an opaque
network where RAW cannot observe and control the individual hops.
RAW uses the term OAM as defined in [RFC6291].
RAW defines the following terms:
PAREO: Packet (hybrid) ARQ, Replication, Elimination and Ordering.
PAREO is a superset Of DetNet's PREOF that includes radio-specific
techniques such as short range broadcast, MUMIMO, constructive
interference and overhearing, which can be leveraged separately or
combined to increase the reliability.
Flapping: In the context of RAW, a link flaps when the reliability
of the wireless connectivity drops abruptly for a short period of
time, typically of a subsecond to seconds duration.
In the context of the RAW work, Reliability and Availability are
defined as follows:
Reliability: Reliability is a measure of the probability that an
item will perform its intended function for a specified interval
under stated conditions. For RAW, the service that is expected is
delivery within a bounded latency and a failure is when the packet
is either lost or delivered too late. RAW expresses reliability
in terms of Mean Time Between Failure (MTBF) and Maximum
Consecutive Failures (MCF). More in [NASA].
Availability: Availability is a measure of the relative amount of
time where a path operates in stated condition, in other words
(uptime)/(uptime+downtime). Because a serial wireless path may
not be good enough to provide the required availability, and even
2 parallel paths may not be over a longer period of time, the RAW
availability implies a path that is a lot more complex than what
DetNet typically envisages (a Track).
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3. Related Work at The IETF
RAW intersects with protocols or practices in development at the IETF
as follows:
* The Dynamic Link Exchange Protocol (DLEP) [RFC8175] from [MANET]
can be leveraged at each hop to derive generic radio metrics
(e.g., based on LQI, RSSI, queueing delays and ETX) on individual
hops.
* OAM work at [detnet] such as [DetNet-IP-OAM] for the case of the
IP Data Plane observes the state of DetNet paths, typically MPLS
and IPv6 pseudowires [DetNet-DP-FW], in the direction of the
traffic. RAW needs feedback that flows on the reverse path and
gathers instantaneous values from the radio receivers at each hop
to inform back the source and replicating relays so they can make
optimized forwarding decisions. The work named ICAN may be
related as well.
* [BFD] detect faults in the path between an ingress and an egress
forwarding engines, but is unaware of the complexity of a path
with replication, and expects bidirectionality. BFD considers
delivery as success whereas with RAW the bounded latency can be as
important as the delivery itself.
* [SPRING] and [BIER] define in-band signaling that influences the
routing when decided at the head-end on the path. There's already
one RAW-related draft at BIER [BIER-PREF] more may follow. RAW
will need new in-band signaling when the decision is distributed,
e.g., required chances of reliable delivery to destination within
latency. This signaling enables relays to tune retries and
replication to meet the required SLA.
* [CCAMP] defines protocol-independent metrics and parameters
(measurement attributes) for describing links and paths that are
required for routing and signaling in technology-specific
networks. RAW would be a source of requirements for CCAMP to
define metrics that are significant to the focus radios.
4. Use Cases and Requirements Served
In order to focus on real-worlds issues and assert the feasibility of
the proposed capabilities, RAW focuses on selected technologies that
can be scheduled at the lower layers: IEEE Std. 802.15.4 timeslotted
channel hopping (TSCH), 3GPP 5G ultra-reliable low latency
communications (URLLC), IEEE 802.11ax/be where 802.11be is extreme
high throughput (EHT), and L-band Digital Aeronautical Communications
System (LDACS). See [RAW-TECHNOS] for more.
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"Deterministic Networking Use Cases" [RFC8578] presents a number of
wireless use cases including Wireless, such as application to
Industrial Applications, Pro-Audio, and SmartGrid Automation.
[RAW-USE-CASES] adds a number of use cases that demonstrate the need
for RAW capabilities for new applications such as Pro-Gaming and
drones. The use cases can be abstracted in two families, Loose
Protection, e.g., protecting the first hop in Radio Access Protection
and Strict Protection, e.g., providing End-to-End Protection in a
wireless mesh.
4.1. Radio Access Protection
To maintain the required SLA at all times, a wireless Host may use
more than one Radio Access Network (RAN) in parallel.
... ..
RAN 1 ----- ... .. ...
/ . .. ....
+--------+ / . .... +-----------+
|Wireless|- . ..... | Service |
| Device |-***-- RAN 2 -- . Internet ....---| / |
|(STA/UE)|- .. ..... |Application|
+--------+ $$$ . ....... +-----------+
\ ... ... .....
RAN n -------- ... .....
*** = flapping at this time $$$ expensive
Figure 1: Radio Access Protection
The RANs may be heterogeneous, e.g., 3GPP 5G [RAW-5G] and Wi-Fi
[RAW-TECHNOS] for high-speed communication, in which case a Layer-3
abstraction becomes useful to select which of the RANs are used at a
particular point of time, and the amount of traffic that is
distributed over each RAN.
The idea is that the rest of the path to the destination(s) is
protected separately (e.g., uses non-congruent paths, leverages
DetNet / TSN, etc...) and is a lot more reliable, e.g., wired. In
that case, RAW observes the reliability of the end-to-end operation
through each of the RANs but only observes and controls the wireless
operation the first hop.
A variation of that use case has a pair of wireless Hosts connected
over a wired core / backbone network. In that case, RAW observes and
controls the ingress and egress RANs, while neglecting the hops in
the core. The resulting loose Track may be instanciated, e.g., using
tunneling or loose source routing between the RANs.
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4.2. End-to-End Protection in a Wireless Mesh
In radio technologies that support mesh networking (e.g., Wi-Fi and
TSCH), a Track is a complex path with distributed PAREO capabilities.
In that case, RAW operates through the multipath and makes decisions
either at the Ingress or at every hop (more in Section 6.1).
A-------B-------C-----D
/ \ / / \
Ingress ----M-------N--zzzzz--- Egress
\ \ / /
P--zzz--Q-------------R
zzz = flapping now
Figure 2: End-to-End Protection
The Protection may be imposed by the source based on end-to-end OAM,
or performed hop-by-hop, in which case the OAM must enables the
intermediate Nodes to estimate the quality of the rest of the
feasible paths in the remainder of the Track to the destination.
5. RAW Considerations
5.1. Reliability and Availability
5.1.1. High Availability Engineering Principles
The reliability criteria of a critical system pervade through its
elements, and if the system comprises a data network then the data
network is also subject to the inherited reliability and availability
criteria. It is only natural to consider the art of high
availability engineering and apply it to wireless communicaitons in
the context of RAW.
There are three principles [pillars] of high availability
engineering:
1. elimination of single points of failure
2. reliable crossover
3. prompt detection of failures as they occur.
These principles are common to all high availability systems, not
just ones with Internet technology at the center. Examples of both
non-Internet and Internet are included.
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5.1.1.1. Elimination of Single Points of Failure
Physical and logical components in a system happen to fail, either as
the effect of wear and tear, when used beyond acceptable limits, or
due to a software bug. It is necessary to decouple component failure
from system failure to avoid the latter. This allows failed
components to be restored while the rest of the system continues to
function.
IP Routers leverage routing protocols to compute alternate routes in
case of a failure. There is a rather open-ended issue over alternate
routes -- for example, when links are cabled through the same
conduit, they form a shared risk link group (SRLG), and will share
the same fate if the bundle is cut. The same effect can happen with
virtual links that end up in a same physical transport through the
games of encapsulation. In a same fashion, an interferer or an
obstacle may affect multiple wireless transmissions at the same time,
even between different sets of peers.
Intermediate network Nodes such as routers, switches and APs, wire
bundles and the air medium itself can become single points of
failure. For High Availability, it is thus required to use
physically link- and Node-disjoint paths; in the wireless space, it
is also required to use the highest possible degree of diversity in
the transmissions over the air to combat the additional causes of
transmission loss.
From an economics standpoint, executing this principle properly
generally increases capitalization expense because of the redundant
equipment. In a constrained network where the waste of energy and
bandwidth should be minimized, an excessive use of redundant links
must be avoided; for RAW this means that the extra bandwidth must be
used wisely and with parcimony.
5.1.1.2. Reliable Crossover
Having a backup equipment has a limited value unless it can be
reliably switched into use within the down-time parameters. IP
Routers execute reliable crossover continuously because the routers
will use any alternate routes that are available [RFC0791]. This is
due to the stateless nature of IP datagrams and the dissociation of
the datagrams from the forwarding routes they take. The "IP Fast
Reroute Framework" [FRR] analyzes mechanisms for fast failure
detection and path repair for IP Fast-Reroute, and discusses the case
of multiple failures and SRLG. Examples of FRR techniques include
Remote Loop-Free Alternate [RLFA-FRR] and backup label-switched path
(LSP) tunnels for the local repair of LSP tunnels using RSVP-TE
[RFC4090].
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Deterministic flows, on the contrary, are attached to specific paths
where dedicated resources are reserved for each flow. This is why
each DetNet path must inherently provide sufficient redundancy to
provide the guaranteed SLA at all times. The DetNet PREOF typically
leverages 1+1 redundancy whereby a packet is sent twice, over non-
congruent paths. This avoids the gap during the fast reroute
operation, but doubles the traffic in the network.
In the case of RAW, the expectation is that multiple transient faults
may happen in overlapping time windows, in which case the 1+1
redundancy with delayed reestablishment of the second path will not
provide the required guarantees. The Data Plane must be configured
with a sufficient degree of redundancy to select an alternate
redundant path immediately upon a fault, without the need for a slow
intervention from the controller plane.
5.1.1.3. Prompt Notification of Failures
The execution of the two above principles is likely to render a
system where the user will rarely see a failure. But someone needs
to in order to direct maintenance.
There are many reasons for system monitoring (FCAPS for fault,
configuration, accounting, performance, security is a handy mental
checklist) but fault monitoring is sufficient reason.
"An Architecture for Describing Simple Network Management Protocol
(SNMP) Management Frameworks" [STD 62] describes how to use SNMP to
observe and correct long-term faults.
"Overview and Principles of Internet Traffic Engineering" [TE]
discusses the importance of measurement for network protection, and
provides abstract an method for network survivability with the
analysis of a traffic matrix as observed by SNMP, probing techniques,
FTP, IGP link state advertisements, and more.
Those measurements are needed in the context of RAW to inform the
controller and make the long term reactive decision to rebuild a
complex path. But RAW itself operates in the Network Plane at a
faster time scale. To act on the Data Plane, RAW needs live
information from the Operational Plane , e.g., using Bidirectional
Forwarding Detection [BFD] and its variants (bidirectional and remote
BFD) to protect a link, and OAM techniques to protect a path.
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5.1.2. Applying Reliability Concepts to Networking
The terms Reliaility and Availability are defined for use in RAW in
Section 2 and the reader is invited to read [NASA] for more details
on the general definition of Reliability. Practically speaking a
number of nines is often used to indicate the reliability of a data
link, e.g., 5 nines indicate a Packet Delivery Ratio (PDR) of
99.999%.
This number is typical in a wired environment where the loss is due
to a random event such as a solar particle that affects the
transmission of a particular frame, but does not affect the previous
or next frame, nor frames transmitted on other links. Note that the
QoS requirements in RAW may include a bounded latency, and a packet
that arrives too late is a fault and not considered as delivered.
For a periodic networking pattern such as an automation control loop,
this number is proportional to the Mean Time Between Failures (MTBF).
When a single fault can have dramatic consequences, the MTBF
expresses the chances that the unwanted fault event occurs. In data
networks, this is rarely the case. Packet loss cannot never be fully
avoided and the systems are built to resist to one loss, e.g., using
redundancy with Retries (HARQ) or Packet Replication and Elimination
(PRE), or, in a typical control loop, by linear interpolation from
the previous measuremnents.
But the linear interpolation method can not resist multiple
consecutive losses, and a high MTBF is desired as a guarantee that
this will not happen, IOW that the number of losses-in-a-row can be
bounded. In that case, what is really desired is a Maximum
Consecutive Failures (MCF). If the number of losses in a row passes
the MCF, the control loop has to abort and the system, e.g., the
production line, may need to enter an emergency stop condition.
Engineers that build automated processes may use the network
reliability expressed in nines or as an MTBF as a proxy to indicate
an MCF, e.g., as described in section 7.4 of the "Deterministic
Networking Use Cases" [RFC8578].
5.1.3. Reliability in the Context of RAW
In contrast with wired networks, errors in transmission are the
predominent source of packet loss in wireless networks.
The root cause for the loss may be of multiple origins, calling for
the use of different forms of diversity:
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Multipath Fading: A destructive interference by a reflection of the
original signal.
A radio signal may be received directly (line-of-sight) and/or as
a reflection on a physical structure (echo). The reflections take
a longer path and are delayed by the extra distance divided by the
speed of light in the medium. Depending on the frequency, the
echo lands with a different phase which may add up to
(constructive interference) or cancel the direct signal
(destructive interference).
The affected frequencies depend on the relative position of the
sender, the receiver, and all the reflecting objects in the
environment. A given hop will suffer from multipath fading for
multiple packets in a row till the something moves that changes
the reflection patterns.
Co-channel Interference: Energy in the spectrum used for the
transmission confuses the receiver.
The wireless medium itself is a Shared Risk Link Group (SRLG) for
nearby users of the same spectrum, as an interference may affect
multiple co-channel transmissions between different peers within
the interference domain of the interferer, possibly even when they
use different technologies.
Obstacle in Fresnel Zone: The optimal transmission happens when the
Fresnel Zone between the sender and the receiver is free of
obstacles.
As long as a physical object (e.g., a metallic trolley between
peers) that affects the transmission is not removed, the quality
of the link is affected.
In an environment that is rich of metallic structures and mobile
objects, a single radio link will provide a fuzzy service, meaning
that it cannot be trusted to transport the traffic reliably over a
long period of time.
Transmission losses are typically not independent, and their nature
and duration are unpredictable; as long as a physical object (e.g., a
metallic trolley between peers) that affects the transmission is not
removed, or as long as the interferer (e.g., a radar) keeps
transmitting, a continuous stream of packets will be affected.
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The key technique to combat those unpredictable losses is diversity.
Different forms of diversity are necessary to combat different causes
of loss and the use of diversity must be maximised to optimize the
PDR.
A single packet may be sent at different times (time diversity) over
diverse paths (spatial diversity) that rely on diverse radio channels
(frequency diversity) and diverse PHY technologies, e.g., narrowband
vs. spread spectrum, or diverse codes. Using time diversity will
defeat short-term interferences; spatial diversity combats very local
causes such as multipath fading; narrowband and spread spectrum are
relatively innocuous to one another and can be used for diversity in
the presence of the other.
5.2. RAW Scope and Prerequisites
A prerequisite to the RAW work is that an end-to-end routing function
computes a complex sub-topology along which forwarding can happen
between a source and one or more destinations. The concept of Track
is specified in the 6TiSCH Architecture [6TiSCH-ARCHI] to represent
that complex sub-topology. Tracks provide a high degree of
redundancy and diversity and enable the DetNet PREOF, network coding,
and possibly RAW specific techniques such as PAREO, leveraging
frequency diversity, time diversity, and possibly other forms of
diversity as well.
How the routing operation (e.g., PCE) in the Controlloer Plane
computes the Track is out of scope for RAW. The scope of the RAW
operation is one Track, and the goal of the RAW operation is to
optimize the use of the Track at the forwarding timescale to maintain
the expected SLA while optimizing the usage of constrained resources
such as energy and spectrum.
Another prerequisite is that an IP link can be established over the
radio with some guarantees in terms of service reliability, e.g., it
can be relied upon to transmit a packet within a bounded latency and
provides a guaranteed BER/PDR outside rare but existing transient
outage windows that can last from split seconds to minutes. The
radio layer can be programmed with abstract parameters, and can
return an abstract view of the state of the Link to help the Network
Layer forwarding decision (think DLEP from MANET).
How the radio interface manages its lower layers is out of control
and out of scope for RAW. In the same fashion, the non-RAW portion
along a loose Track is by definition out of control and out of scope
for RAW. Whether it is a single hop or a mesh is also unknown and
out of scope.
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5.3. Routing Time Scale vs. Forwarding Time Scale
With DetNet, the Controller Plane Function that handles the routing
computation and maintenance (the PCE) can be centralized and can
reside outside the network. In a wireless mesh, the path to the PCE
can be expensive and slow, possibly going across the whole mesh and
back. Reaching to the PCE can also be slow in regards to the speed
of events that affect the forwarding operation at the radio layer.
Due to that cost and latency, the Controller Plane is not expected to
be sensitive/reactive to transient changes. The abstraction of a
link at the routing level is expected to use statistical metrics that
aggregate the behavior of a link over long periods of time, and
represent its properties as shades of gray as opposed to numerical
values such as a link quality indicator, or a boolean value for
either up or down.
+----------------+
| Controller |
| [PCE] |
+----------------+
^
|
Slow
|
_-._-._-._-._-._-. | ._-._-._-._-._-._-._-._-._-._-._-._-
_-._-._-._-._-._-._-. | _-._-._-._-._-._-._-._-._-._-._-._-
|
Expensive
|
.... | .......
.... . | . .......
.... v ...
.. A-------B-------C---D ..
... / \ / / \ ..
. I ----M-------N--***-- E ..
.. \ \ / / ...
.. P--***--Q----------R ....
.. ....
. <----- Fast -------> ....
....... ....
.................
*** = flapping at this time
Figure 3: Time Scales
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In the case of wireless, the changes that affect the forwarding
decision can happen frequently and often for short durations, e.g., a
mobile object moves between a transmitter and a receiver, and will
cancel the line of sight transmission for a few seconds, or a radar
measures the depth of a pool and interferes on a particular channel
for a split second.
There is thus a desire to separate the long term computation of the
route and the short term forwarding decision. In that model, the
routing operation computes a complex Track that enables multiple Non-
Equal Cost Multi-Path (N-ECMP) forwarding solutions, and leaves it to
the Data Plane to make the per-packet decision of which of these
possibilities should be used.
In the wired world, and more specifically in the context of Traffic
Engineering (TE), an alternate path can be used upon the detection of
a failure in the main path, e.g., using OAM in MPLS-TP or BFD over a
collection of SD-WAN tunnels. RAW formalizes a forwarding time scale
that is an order(s) of magnitude shorter than the controller plane
routing time scale, and separates the protocols and metrics that are
used at both scales. Routing can operate on long term statistics
such as delivery ratio over minutes to hours, but as a first
approximation can ignore flapping. On the other hand, the RAW
forwarding decision is made at the scale of the packet rate, and uses
information that must be pertinent at the present time for the
current transmission(s).
6. RAW Architecture Elements
A RAW Network Plane may be strict or loose, depending on whether RAW
observes and takes actions on all hops or not. For instance, the
packets between two wireless entities may be relayed over a wired
infrastructure such as a Wi-Fi extended service set (ESS) or a 5G
Core; in that case, RAW observes and control the transmission over
the wireless first and last hops, as well as end-to-end metrics such
as latency, jitter, and delivery ratio. This operation is loose
since the structure and properties of the wired infrastructure are
ignored, and may be either controlled by other means such as DetNet/
TSN, or neglected in the face of the wireless hops.
6.1. Wireless Tracks
The "6TiSCH Architecture" [6TiSCH-ARCHI] introduces the concept of
Track a possibly complex path with the PAREO functions operated
within. RAW extends the concept to any wireless mesh technology,
including, e.g., Wi-Fi.
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A simple Track is composed of a direct sequence of reserved hops to
ensure the transmission of a single packet from a source Node to a
destination Node across a multihop path.
A Complex Track is designed as a directed acyclic graph from a source
Node towards a destination Node to support multi-path forwarding. By
employing PRE functions [RFC8655], several paths may be computed, and
these paths may be more or less independent. For example, a complex
Track may branch off and rejoin over non-congruent paths (branches).
6.2. PAREO Functions
RAW may control whether and how to use packet replication and
elimination (PRE), Automatic Repeat reQuest (ARQ), Hybrid ARQ (HARQ)
that includes Forward Error Correction (FEC) and coding, and other
wireless-specific techniques such as overhearing and constructive
interferences, in order to increase the reliabiility and availability
of the end-to-end transmission.
Collectively, those function are called PAREO for Packet (hybrid)
ARQ, Replication, Elimination and Ordering. By tuning dynamically
the use of PAREO functions, RAW avoids the waste of critical
resources such as spectrum and energy while providing that the
guaranteed SLA, e.g., by adding redundancy only when a spike of loss
is observed.
In a nutshell, PAREO establishes several paths in a network to
provide redundancy and parallel transmissions to bound the end-to-end
delay to traverse the network. Optionally, promiscuous listening
between paths is possible, such that the Nodes on one path may
overhear transmissions along the other path. Considering the
scenario shown in Figure 4, many different paths are possible for S
to reach R. A simple way to benefit from this topology could be to
use the two independent paths via Nodes A, C, E and via B, D, F. But
more complex paths are possible by interleaving transmissions from
the lower level of the path to the upper level.
(A) -- (C) -- (E)
/ \
ingress | | | egress
\ /
(B) -- (D) -- (F)
Figure 4: A Ladder Shape with Two Parallel Paths
PAREO may also take advantage of the shared properties of the
wireless medium to compensate for the potential loss that is incurred
with radio transmissions.
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For instance, when the source sends to Node A, Node B may listen
promiscuously and get a second chance to receive the frame without an
additional transmission. Note that B would not have to listen if it
already received that particular frame at an earlier timeslot in a
dedicated transmission towards B.
The PAREO model can be implemented in both centralized and
distributed scheduling approaches. In the centralized approach, a
Path Computation Element (PCE) scheduler calculates a Track and
schedules the communication. In the distributed approach, the Track
is computed within the network, and signaled in the packets, e.g.,
using BIER-TE, Segment Routing, or a Source Routing Header.
6.2.1. Packet Replication
By employing a Packet Replication procedure, a Node forwards a copy
of each data packet to more than one successor. To do so, each Node
(i.e., ingress and intermediate Node) sends the data packet multiple
times as separate unicast transmissions. For instance, in Figure 5,
the ingress Node is transmitting the packet to both successors, nodes
A and B, at two different times.
===> (A) => (C) => (E) ===
// \\// \\// \\
ingress //\\ //\\ egress
\\ // \\ // \\ //
===> (B) => (D) => (F) ===
Figure 5: Packet Replication
An example schedule is shown in Table 1. This way, the transmission
leverages with the time and spatial forms of diversity.
+---------+------+------+------+------+------+------+------+
| Channel | 0 | 1 | 2 | 3 | 4 | 5 | 6 |
+=========+======+======+======+======+======+======+======+
| 0 | S->A | S->B | B->C | B->D | C->F | E->R | F->R |
+---------+------+------+------+------+------+------+------+
| 1 | | A->C | A->D | C->E | D->E | D->F | |
+---------+------+------+------+------+------+------+------+
Table 1: Packet Replication: Sample schedule
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6.2.2. Packet Elimination
The replication operation increases the traffic load in the network,
due to packet duplications. This may occur at several stages inside
the Track, and to avoid an explosion of the number of copies, a
Packet Elimination procedure must be applied as well. To this aim,
once a Node receives the first copy of a data packet, it discards the
subsequent copies.
The logical functions of Replication and Elimination may be
collocated in an intermediate Node, the Node first eliminating the
redundant copies and then sending the packet exactly once to each of
the selected successors.
6.2.3. Promiscuous Overhearing
Considering that the wireless medium is broadcast by nature, any
neighbor of a transmitter may overhear a transmission. By employing
the Promiscuous Overhearing operation, the next hops have additional
opportunities to capture the data packets. In Figure 6, when Node A
is transmitting to its DP (Node C), the AP (Node D) and its sibling
(Node B) may decode this data packet as well. As a result, by
employing corellated paths, a Node may have multiple opportunities to
receive a given data packet. This feature not only enhances the end-
to-end reliability but also it reduces the end-to-end delay and
increases energy efficiency.
===> (A) ====> (C) ====> (E) ====
// ^ | \\ \\
ingress | | \\ egress
\\ | v \\ //
===> (B) ====> (D) ====> (F) ====
Figure 6: Unicast with Overhearing
6.2.4. Constructive Interference
Constructive Interference can be seen as the reverse of Promiscuous
Overhearing, and refers to the case where two senders transmit the
exact same signal in a fashion that the emitted symbols add up at the
receiver and permit a reception that would not be possible with a
single sender at the same PHY mode and the same power level.
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Constructive Interference was proposed on 5G, Wi-Fi7 and even tested
on IEEE Std 802.14.5. The hard piece is to synchronize the senders
to the point that the signals are emitted at slightly different time
to offset the difference of propagation delay that corresponds to the
difference of distance of the transmitters to the receiver at the
speed of light to the point that the symbols are superposed long
enough to be recognizable.
7. RAW Architecture
RAW inherits the conceptual model described in section 4 of the
DetNet Architecture [RFC8655].
A Controller Plane Function (CPF) called the Path Computation Element
(PCE) [RFC4655] interacts with RAW Nodes over a Southbound API. The
RAW Nodes are DetNet relays that are capable of additional diversity
mechanisms and measurement functions related to the radio interface,
in particular the PAREO diversity mechanisms.
The PCE defines a complex Track between an Ingress End System and an
Egress End System, and indicates to the RAW Nodes where the PAREO
operations may be actioned in the Network Plane. The Track may be
loosely expressed in order to traverse a non-RAW subnetwork. In that
case, the expectation is that the non-RAW subnetwork can be neglected
in the RAW computation, that is, considered infinitely fast, reliable
and/or available in comparison with the links between RAW nodes.
CPF CPF CPF CPF
Southbound API
_-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-
_-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-
RAW --z RAW --z RAW --z RAW
z-- Node z-- Node z-- Node z-- Node --z
Ingress --z / / z-- Egress
End \ \ End
Node ---z / / ..... z-- Node
z-- RAW --z RAW ( non-RAW ) --- RAW ---z
Node z-- Node --- ( Nodes ) Node
...
--z wireless wired
z-- link --- link
Figure 7: RAW Nodes
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The Link-Layer metrics are reported to the PCE in a time-aggregated,
e.g., statistical fashion. Example Link-Layer metrics include
typical Link bandwidth (the medium speed depends dynamically on the
PHY mode and the number of users sharing the spectrum) and average
availability and reliability figures such as Packet Delivery Ratio
(PDR) over long periods of time.
Based on those metrics, the PCE installs the Track with enough
redundant forwarding solutions to ensure that the Network Plane can
reliably deliver the packets within a System Level Agreement (SLA)
associated to the flow. The SLA defines end-to-end reliability and
availability figures, where reliability may be expressed a successful
delivery within a bounded delay. Once a Track is established, end-
to-end subpath and overall reliability and availability metrics are
also reported to the PCE to assure that the SLA is continuously met
and to have it recompute the Track if not.
Depending on the SLA, the Track or a leg of the Track may include
non-RAW Nodes, either interleaved inside the Track, or more typically
till the Egress End Node. RAW observes the Lower-Layer Links between
RAW nodes (typically, radio links) and the end-to-end Network Layer
subpath to decide at all times which of the PAREO diversity is
actioned by which RAW Nodes.
7.1. PCE vs. PSE
Section 5.3 shows that the time scale at which RAW operates is not
that of the Controller Plane that needs to deal with a possibly large
whole network and make global optimization across multiple flows that
may contend for limited resources.
RAW separates the path computation time scale at which a complex path
is recomputed from the path selection time scale at which the
forwarding decision is taken for one or a few packets. RAW operates
at the path selection time scale. The RAW problem is to decide,
within the redundant solutions that are proposed by the PCE, which
will be used for each packet to provide a Reliable and Available
service while minimizing the waste of constrained resources.
To that effect, RAW defines the Path Selection Engine (PSE) that is
the counter-part of the PCE to perform rapid local adjustments of the
forwarding tables within the diversity that the PCE has selected for
the Track. The PSE enables to exploit the richer forwarding
capabilities with PAREO and scheduled transmissions at a faster time
scale over the smaller domain that is the Track, in either a loose or
a strict fashion.
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+---------------+------------------------+-------------------+
| | PCE (Not in Scope) | PSE (In Scope) |
+===============+========================+===================+
| Operation | Centralized | Source-Routed or |
| | | Distributed |
+---------------+------------------------+-------------------+
| Communication | Slow, expensive | Fast, local |
+---------------+------------------------+-------------------+
| Time Scale | Long (hours, days) | Short (seconds, |
| | | sub-second) |
+---------------+------------------------+-------------------+
| Network Size | Large, many Tracks to | Small, within one |
| | optimize globally | Track |
+---------------+------------------------+-------------------+
| Considered | Averaged, Statistical, | Instant values / |
| Metrics | Shade of grey | boolean condition |
+---------------+------------------------+-------------------+
Table 2: PCE vs. PSE
7.2. RAW OAM
The RAW OAM operation in the Network Plane observes a subset of the
links along that redundant path and the RAW PSE makes the decision on
which PAREO function in actioned at which RAW Node, for a packet or a
small collection of packets.
... ..
RAN 1 ----- ... .. ...
/ . .. ....
+-------+ / . .. .... +------+
|Ingress|- . ..... |Egress|
| End |------ RAN 2 -- . Internet ....---| End |
|System |- .. ..... |System|
+-------+ \ . ...... +------+
\ ... ... .....
RAN n -------- ... .....
<------------------> <-------------------->
Observed by OAM Opaque to OAM
Figure 8: Observed Links in Radio Access Protection
In the case of a End-to-End Protection in a Wireless Mesh, the Track
is strict and congruent with the path so all links are observed.
Conversely, in the case of Radio Access Protection, the Track is
Loose and in that case only the first hop is observed; the rest of
the path is abstracted and considered infinitely reliable.
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In the case of the Radio Access Protection, only the first hop is
protected; the loss of a packet that was sent over one of the
possible first hops is attributed to that first hop, even if a
particular loss effectively happens farther down the path.
The Links that are not observed by OAM are opaque to it, meaning that
the OAM information is carried across and possibly echoed as data,
but there is no information capture in intermediate nodes. In the
example above, the Internet is opaque and not controlled by RAW;
still the RAW OAM measures the end-to-end latency and delivery ratio
for packets sent via each if RAN 1, RAN 2 and RAN 3, and determines
whether a packet should be sent over either or a collection of those
access links.
7.3. Source-Routed vs. Distributed Forwarding Decision
Within a large routed topology, the route-over mesh operation builds
a particular complex Track with one source and one or more
destinations; within the Track, packets may follow different paths
and may be subject to RAW forwarding operations that include
replication, elimination, retries, overhearing and reordering.
The RAW forwarding decisions include the selection of points of
replication and elimination, how many retries can take place, and a
limit of validity for the packet beyond which the packet should be
destroyed rather than forwarded uselessly further down the Track.
The decision to apply the RAW techniques must be done quickly, and
depends on a very recent and precise knowledge of the forwarding
conditions within the complex Track. There is a need for an
observation method to provide the RAW Data Plane with the specific
knowledge of the state of the Track for the type of flow of interest
(e.g., for a QoS level of interest). To observe the whole Track in
quasi real time, RAW considers existing tools such as L2-triggers,
DLEP, BFD and leverages in-band and out-of-band OAM to capture and
repotr that information to the SRE.
One possible way of making the RAW forwarding decisions within a
Track is to position a unique SRE at the ingress and express its
decision in-band in the packet, which requires new loose or strict
signaling. To control the RAW forwarding operation along a Track for
the individual packets, RAW leverages and extends known techniques
such as DetNet tagging, Segment Routing (SRv6) or BIER-TE such as
done with [BIER-PREF].
The alternate way is to operate the SRE in each forwarding Node,
which makes the RAW forwarding decisions for a packet on its own,
based on its knowledge of the expectation (timeliness and
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reliability) for that packet and a recent observation of the rest of
the way across the possible paths based on OAM. Information about
the desired service should be placed in the packet and matched with
the forwarding Node's capabilities and policies.
In either case, a per-flow state is installed in all intermediate
Nodes to recognize the flow and determine the forwarding policy to be
applied.
7.4. Flow Identification
Section 4.7 of the DetNet Architecture [RFC8655] ties the app-flow
identification which is an appliation layer concept with the network
path identification that depends on the networking technology by
"exporting of flow identification", e.g., to a MPLS label.
With RAW, this exporting operation is injective but not bijective.
e.g., a flow is fully placed within one RAW Track, but not all
packets along that Track are necessarily part of the same flow. For
instance, out-of-band OAM packets must circulate in the exact same
fashion as the flows that they observe. It results that the flow
identification that maps to to app-flow at the network layer must be
separate from the path identification that is used to forward a
packet.
Flow 1 (6-tuple) ----+
|
Flow 2 (6-tuple) ---+ |
| |
OAM -----------+ | |
| | |
| | |
| | | | |
| v v v |
| |
+---------+---------+
|
|
+------------> Track 1
(IP address, instanceId)
Figure 9: Flow Injection
Section 3.4 of the DetNet data-plane framework [DetNet-DP-FW]
indicates that for a DetNet IP Data Plane, a flow is identified by an
IPv6 6-tuple. With RAW, that 6-tuple is not what indicates the
Track, in other words, the flow ID is not the Track ID.
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For instance, the 6TiSCH Architecture [6TiSCH-ARCHI] uses a
combination of the address of the Ingress End System and an instance
identifier in a Hop-by-hop option to indicate a Track. Packets that
are tagged with the same (address, instance ID) tuple will experience
the same forwarding behavior regardless of the IPv6 6-tuple, and
regardless of whether they transport application flows or OAM.
8. Security Considerations
RAW uses all forms of diversity including radio technology and
physical path to increase the reliability and availability in the
face of unpredictable conditions. While this is not done
specifically to defeat an attacker, the amount of diversity used in
RAW makes an attack harder to achieve.
8.1. Forced Access
RAW will typically select the cheapest collection of links that
matches the requested SLA, for instance, leverage free WI-Fi vs. paid
3GPP access. By defeating the cheap connectivity (e.g., PHY-layer
interference) the attacker can force an End System to use the paid
access and increase the cost of the transmission for the user.
9. IANA Considerations
This document has no IANA actions.
10. Contributors
Xavi Vilajosana: Wireless Networks Research Lab, Universitat Oberta
de Catalunya
Rex Buddenberg:
Remous-Aris Koutsiamanis: IMT Atlantique
Nicolas Montavont: IMT Atlantique
11. Acknowledgments
TBD
12. References
12.1. Normative References
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[6TiSCH-ARCHI]
Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", Work in Progress, Internet-Draft,
draft-ietf-6tisch-architecture-28, 29 October 2019,
<https://tools.ietf.org/html/draft-ietf-6tisch-
architecture-28>.
[RAW-TECHNOS]
Thubert, P., Cavalcanti, D., Vilajosana, X., and C.
Schmitt, "Reliable and Available Wireless Technologies",
Work in Progress, Internet-Draft, draft-thubert-raw-
technologies-04, 6 January 2020,
<https://tools.ietf.org/html/draft-thubert-raw-
technologies-04>.
[RAW-USE-CASES]
Papadopoulos, G., Thubert, P., Theoleyre, F., and C.
Bernardos, "RAW use cases", Work in Progress, Internet-
Draft, draft-bernardos-raw-use-cases-03, 8 March 2020,
<https://tools.ietf.org/html/draft-bernardos-raw-use-
cases-03>.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[BFD] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
[RFC6291] Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
D., and S. Mansfield, "Guidelines for the Use of the "OAM"
Acronym in the IETF", BCP 161, RFC 6291,
DOI 10.17487/RFC6291, June 2011,
<https://www.rfc-editor.org/info/rfc6291>.
[RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases",
RFC 8578, DOI 10.17487/RFC8578, May 2019,
<https://www.rfc-editor.org/info/rfc8578>.
[RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B.
Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175,
DOI 10.17487/RFC8175, June 2017,
<https://www.rfc-editor.org/info/rfc8175>.
Thubert, et al. Expires 26 November 2020 [Page 25]
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[RFC8557] Finn, N. and P. Thubert, "Deterministic Networking Problem
Statement", RFC 8557, DOI 10.17487/RFC8557, May 2019,
<https://www.rfc-editor.org/info/rfc8557>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
12.2. Informative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
[TE] Awduche, D., Chiu, A., Elwalid, A., Widjaja, I., and X.
Xiao, "Overview and Principles of Internet Traffic
Engineering", RFC 3272, DOI 10.17487/RFC3272, May 2002,
<https://www.rfc-editor.org/info/rfc3272>.
[STD 62] Harrington, D., Presuhn, R., and B. Wijnen, "An
Architecture for Describing Simple Network Management
Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
DOI 10.17487/RFC3411, December 2002,
<https://www.rfc-editor.org/info/rfc3411>.
[RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
DOI 10.17487/RFC4090, May 2005,
<https://www.rfc-editor.org/info/rfc4090>.
[FRR] Shand, M. and S. Bryant, "IP Fast Reroute Framework",
RFC 5714, DOI 10.17487/RFC5714, January 2010,
<https://www.rfc-editor.org/info/rfc5714>.
[RLFA-FRR] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N.
So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)",
RFC 7490, DOI 10.17487/RFC7490, April 2015,
<https://www.rfc-editor.org/info/rfc7490>.
[BIER-PREF]
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://tools.ietf.org/html/draft-thubert-
bier-replication-elimination-03>.
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[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-mirsky-detnet-ip-oam-02, 23 March
2020, <https://tools.ietf.org/html/draft-mirsky-detnet-ip-
oam-02>.
[DetNet-DP-FW]
Varga, B., Farkas, J., Berger, L., Malis, A., and S.
Bryant, "DetNet Data Plane Framework", Work in Progress,
Internet-Draft, draft-ietf-detnet-data-plane-framework-06,
6 May 2020, <https://tools.ietf.org/html/draft-ietf-
detnet-data-plane-framework-06>.
[RAW-5G] Farkas, J., Dudda, T., Shapin, A., and S. Sandberg, "5G -
Ultra-Reliable Wireless Technology with Low Latency", Work
in Progress, Internet-Draft, draft-farkas-raw-5g-00, 1
April 2020,
<https://tools.ietf.org/html/draft-farkas-raw-5g-00>.
[NASA] Adams, T., "RELIABILITY: Definition & Quantitative
Illustration", <https://kscddms.ksc.nasa.gov/Reliability/
Documents/150814-3bWhatIsReliability.pdf>.
[MANET] IETF, "Mobile Ad hoc Networking",
<https://dataTracker.ietf.org/doc/charter-ietf-manet/>.
[detnet] IETF, "Deterministic Networking",
<https://dataTracker.ietf.org/doc/charter-ietf-detnet/>.
[SPRING] IETF, "Source Packet Routing in Networking",
<https://dataTracker.ietf.org/doc/charter-ietf-spring/>.
[BIER] IETF, "Bit Indexed Explicit Replication",
<https://dataTracker.ietf.org/doc/charter-ietf-bier/>.
[BFD] IETF, "Bidirectional Forwarding Detection",
<https://dataTracker.ietf.org/doc/charter-ietf-bfd/>.
[CCAMP] IETF, "Common Control and Measurement Plane",
<https://dataTracker.ietf.org/doc/charter-ietf-ccamp/>.
Authors' Addresses
Pascal Thubert (editor)
Cisco Systems, Inc
Building D
Thubert, et al. Expires 26 November 2020 [Page 27]
Internet-Draft RAW Architecture/Framework May 2020
45 Allee des Ormes - BP1200
06254 MOUGINS - Sophia Antipolis
France
Phone: +33 497 23 26 34
Email: pthubert@cisco.com
Georgios Z. Papadopoulos
IMT Atlantique
Office B00 - 114A
2 Rue de la Chataigneraie
35510 Cesson-Sevigne - Rennes
France
Phone: +33 299 12 70 04
Email: georgios.papadopoulos@imt-atlantique.fr
Rex Buddenberg
CA
United States of America
Email: buddenbergr@gmail.com
Thubert, et al. Expires 26 November 2020 [Page 28]