RAW WG CJ. Bernardos
Internet-Draft UC3M
Intended status: Standards Track A. Mourad
Expires: August 26, 2021 InterDigital
February 22, 2021
Terminal-based joint selection and configuration of MEC host and RAW
network
draft-bernardos-raw-joint-selection-raw-mec-00
Abstract
There are several scenarios involving multi-hop heterogeneous
wireless networks requiring reliable and available features combined
with multi-access edge computing, such as Industry 4.0. This
document discusses mechanisms to allow a terminal influencing the
selection of a MEC host for instantiation of the terminal-targeted
MEC applications and functions, and (re)configuring the RAW network
lying in between the terminal and the selected MEC host. This
document assumes IETF RAW and ETSI MEC integration, fostering
discussion about extensions at both IETF and ETSI MEC to better
support these scenarios.
Status of This Memo
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This Internet-Draft will expire on August 26, 2021.
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document authors. All rights reserved.
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Provisions Relating to IETF Documents
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Table of Contents
1. Introduction and Problem Statement . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Terminal-based joint selection and configuration of MEC host
and RAW network . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Extended User application look-up to support reliability
and availability information/capabilities . . . . . . . . 7
3.2. Extended Application context create to support
reliability and availability information/capabilities . . 9
3.3. Extended Application context update to support
reliability and availability information/capabilities . . 11
3.4. Receiving extended notification events . . . . . . . . . 12
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
5. Security Considerations . . . . . . . . . . . . . . . . . . . 13
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
7. Informative References . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction and Problem Statement
Wireless operates on a shared medium, and transmissions cannot be
fully deterministic due to uncontrolled interferences, including
self-induced multipath fading. RAW (Reliable and Available Wireless)
is an effort to provide Deterministic Networking on across a path
that include a wireless interface. RAW provides for high reliability
and availability for IP connectivity over a wireless medium. The
wireless medium presents significant challenges to achieve
deterministic properties such as low packet error rate, bounded
consecutive losses, and bounded latency. RAW extends the DetNet
Working Group concepts to provide for high reliability and
availability for an IP network utilizing scheduled wireless segments
and other media, e.g., frequency/time-sharing physical media
resources with stochastic traffic: IEEE Std. 802.15.4 timeslotted
channel hopping (TSCH), 3GPP 5G ultra-reliable low latency
communications (URLLC), IEEE 802.11ax/be, and L-band Digital
Aeronautical Communications System (LDACS), etc. Similar to DetNet,
RAW technologies aim at staying abstract to the radio layers
underneath, addressing the Layer 3 aspects in support of applications
requiring high reliability and availability.
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As introduced in [I-D.pthubert-raw-architecture], 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, amongst the
redundant solutions that are proposed by the Patch Computation
Element (PCE), which one 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 Packet (hybrid) ARQ,
Replication, Elimination and Ordering (PAREO), and scheduled
transmissions at a faster time scale.
Multi-access Edge Computing (MEC) -- formerly known as Mobile Edge
Computing -- capabilities deployed in the edge of the mobile network
can facilitate the efficient and dynamic provision of services to
mobile users. The ETSI ISG MEC working group, operative from end of
2014, intends to specify an open environment for integrating MEC
capabilities with service providers' networks, including also
applications from 3rd parties. These distributed computing
capabilities will make available IT infrastructure as in a cloud
environment for the deployment of functions in mobile access
networks.
One relevant exemplary scenario showing the need for an integration
of RAW and MEC is introduced next. One of the main (and distinct)
use cases of 5G is Ultra Reliable and Low Latency Communications
(URLLC). Among the many so-called "verticals" that require URLLC
features, the Industry 4.0 (also referred to as Wireless for
Industrial Applications) is probably the one with more short-term
potential. As identified in [I-D.ietf-raw-use-cases], this scenario
also calls for RAW solutions, as cables are not that suitable for the
robots and mobile vehicles typically used in factories. This is also
a very natural scenario for MEC deployments, as bounded, and very low
latencies are needed between the robots and physical actuators and
the control logic managing them.
This scenario includes a wireless domain, involving multiple MEC
platforms to ensure low latency to applications, by being able to
host MEC applications in several locations, and dynamically migrate
the apps as the terminals move around and the serving MEC platform
might no longer be capable of meeting the latency requirements.
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This document discussess mechanisms to allow the UE to influence/
control jointly the RAW and MEC components deployed in the end-to-end
path.
-----------
| PCE |
-----+-----
|
--+--
( )
( )
( )
--+--
|
-----------
| RAW PSE |
-----+-----
|
____________________+__________________________________
| *( ( o ) ) |
| RAW * * ^ |
| network ****** * / \ |
| ******* * / \ ----- |
| * ** ------- |app| |
| * * | RAW | ------- |
| ( ( o ) )* * |node |-| MEC | |
| ----- ^ *( ( o ) ) ------- ------- |
| |app| / \ ^ * |
| ----- / \ / \ ** |
| |app| ------- / \ *( ( o ) ) |
| ------- | RAW | ------- ^ (o |
| | MEC |------|node | | RAW | / \ -\---- |
| ------- ------- |node | / \ |term| |
| o) o) ------- ------- -0--0- |
| ----/- ----/- | RAW | |
| |term| |term| |node | |
| -0--0- -0--0- ------- |
|_______________________________________________________|
Figure 1: Exemplary scenario depicting MEC and RAW in an industrial
environments
Figure 1 depicts an exemplary scenario that integrates a 3GPP 5G
network, with ETSI MEC deployed at the edge, and an IETF RAW-capable
wireless multi-hop backhaul segment connecting the RAN and the MEC
hosts and UPFs. This setup can be used for example in a factory
where multiple robots and AGVs are wirelessly connected, and
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controlled via remote apps. Control applications running in the edge
(implemented as MEC applications) require bounded low latencies and a
guaranteed availability, despite the mobility of the terminals and
the changing wireless conditions. An heterogeneous wireless mesh
network is used to provide connectivity inside the factory.
[I-D.bernardos-raw-mec] explores already the integration of RAW and
MEC. The current document goes a bit further, proposing solutions to
allow terminal-based selection of the MEC platform where to
instantiate an app taking into account RAW aspects.
2. Terminology
The following terms used in this document are defined by the ETSI MEC
ISG, and the IETF:
MEC host. The mobile edge host is an entity that contains a
mobile edge platform and a virtualization infrastructure which
provides compute, storage, and network resources, for the purpose
of running mobile edge applications.
MEC platform. The mobile edge platform is the collection of
essential functionalities required to run mobile edge applications
on a particular virtualization infrastructure and enable them to
provide and consume mobile edge services.
MEPM. MEC Platform Manager.
MEC applications. Mobile edge applications are instantiated on
the virtualization infrastructure of the mobile edge host based on
configuration requests validated by the mobile edge management.
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.
PSE. The Path Selection Engine (PSE) 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.
UALCMP. The User Application LifeCycle Management Proxy (UALCMP)
exposes the Mx2 API to the device application. It allows the
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device application to request the following application lifecycle
management operations from the MEC system: query the available
applications, instantiation and deletion of an application and
update of an existing application context.
3. Terminal-based joint selection and configuration of MEC host and RAW
network
This document defines extensions to: (i) enable a terminal to
discover any RAW-enabled network on the path between the terminal and
the MEC app host, and the RAW network associated capabilities; (ii)
enable the terminal to request desired reliability and availability
requirements to be met simultaneously by the MEC+RAW system; and,
(iii) enable direct notifications from the RAW network to the
terminal, to help with end-to-end application-level optimization.
Most of the required extensions are related to ETSI MEC components
and interfaces, and therefore are out of the scope of the IETF.
However, we still briefly describe them for completeness, putting the
main focus on the IETF RAW components and interactions.
Figure 2 shows the components and interfaces impacted by the
extensions described in this document. The MEC UALCMP is logically
extended with a RAW controller (RAW ctrl) functionality, to enable a
terminal to learn about the RAW and MEC capabilities of the 5G
network it is attached to, and specify its requirements in terms of
availability and reliability for joint MEC app instantiation and RAW
network configuration.
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------------
| MEC host |
------+-----
------------ ---------- |
| User | | Mobile | ------+---------------------
| App. LCM +---+ edge | | MEC host |
| Proxy | | orch. | | ----------------- |
------------ ---------- | + ------ ------ | |
| RAW | | ----- | | ME | |RAW | | |
| ctrl| -----------+ |app+..+ |serv| |ctrl| | |
---+--- | | ----- | ------ ------ | |
| +--+--+ | |app+..+ MEC platform | |
| | RAW | | ----- ----------------- |
+-----.+ PSE | ----------------------------
+-+-+-+
| | ( ( o ) ) ( ( o ) )
| | ^ ^
| | / \ / \
| | / \ / \
| | ------- -------
| +-----------| RAW |-------+ RAW |
+-------------+node | |node |
------- -------
Figure 2: Block diagram
The RAW ctrl - RAW PSE interface was first introduced in
[I-D.bernardos-raw-mec].
3.1. Extended User application look-up to support reliability and
availability information/capabilities
Here we specify how the terminal/UE is augmented with the additional
capability of discovering a RAW network on the path to the hosts of
its target MEC applications, and obtaining information about
reliability and availability configuration in the RAW network.
Figure 3 shows an exemplary signaling flow diagram.
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+--------------+
+----------+ | MEC host |
+--+ | UALCMP | +---+ +----+ +----+ +----+ | +----+ |
|UE| +---+----+-+ |RAW| |MEAO| |RAW | |RAW | | +---+ |RAW | |
+--+ | |RAW | |PSE| +----+ |node| |node| | |MEP| |ctrl| |
| | |ctrl| +---+ | +----+ +----+ | +---+ +----+ |
| | +----+ | | | | +---|------|---+
| | | |<...RAW........>| | | |
| | | |<...signalling.........>| | |
| | | | | | | | |
|1.GET ../app_list | | | | | |
|....>| | | | | | | |
| |........MEC...........>|.....MEC................>| |
| |<.......signalling.....|<....signalling..........| |
| | | | | | | | |
| |2.RAW info req.| | | | | |
| |...>|.........>| | | | | |
| |<...|<.........| | | | | |
| | | | | | | | |
|2.200 OK | | | | | | |
|(Application List) | | | | | |
| | | | | | | | |
Figure 3: Extended User application look-up
We next explain each of the steps illustrated in the figure:
1. An application that requires use of a MEC app with specific
reliability/availability requirements is started at the UE. The
UE can either make use of a GET request to the MEC UALCMP
extended to indicate that the UE is interested in reliability and
availability information, or the UALCMP can decide to include
this information based on policies. Either way, the UALCMP
authorizes the request from the UE. The MEC system retrieves the
list of UE applications available to the requesting UE (this
might require interaction with other MEC system level components
such as MEAO as depicted optionally in the figure).
2. The UALCMP requests information related to reliability and
availability from the RAW PSE through the RAW ctrl logical
component.
3. The UALCMP returns the 200 OK response to the device application,
following ETSI MEC standards, but with its message body extended
to include RAW parameters (namely, Reliability and availability
characteristics of the application and its connectivity), such
as:
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* The assured round trip time in milliseconds supported by the
MEC system for the MEC application instance.
* The assured connection bandwidth in kbit/s for the use of the
MEC application instance.
* The assured jitter in milliseconds supported by the MEC system
for the MEC application instance.
* The maximum percentage of packets failed.
* The assured number of redundant paths supported by the MEC
system for the MEC application instance.
3.2. Extended Application context create to support reliability and
availability information/capabilities
Here we specify how the UE is augmented with the capability to
request the creation of a MEC app including requirements about
reliability and availability.
+--------------+
+----------+ | MEC host |
+--+ | UALCMP | +---+ +----+ +----+ +----+ | +----+ |
|UE| +---+----+-+ |RAW| |MEAO| |RAW | |RAW | | +---+ |RAW | |
+--+ | |RAW | |PSE| +----+ |node| |node| | |MEP| |ctrl| |
| | |ctrl| +---+ | +----+ +----+ | +---+ +----+ |
| | +----+ | | | | +---|------|---+
| | | |<..RAW.........>| | | |
| | | |<..signalling..........>| | |
| | | | | | | | |
|1.POST ../app_context| | | | | |
|....>| | | | | | | |
| |..MEC signalling......>|..MEC signalling........>| |
| | | | | | | 2.MEC-to-RAW
| | | | | | | |.....>|
| | | |<..2.RAW................................|
| | |<.........|....signalling.>| | | |
| | | |.......................>| | |
| | | | | | | |<.....|
| |<......MEC.signalling..|<........MEC signalling..| |
| | | | | | | | |
|3.201 Created | | | | | |
|(AppContext) | | | | | |
| | | | | | | | |
Figure 4: Application context create
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Figure 4 shows an exemplary signaling flow diagram. We next explain
each of the steps illustrated in the figure:
1. The UE submits the POST request to the UALCMP. The message body
contains the data structure for the application context to be
created, which is extended to include reliability and
availability attributes:
* The assured round trip time in milliseconds supported by the
MEC system for the MEC application instance.
* The assured connection bandwidth in kbit/s for the use of the
MEC application instance.
* The assured jitter in milliseconds supported by the MEC system
for the MEC application instance.
* The maximum percentage of packets failed.
* The assured number of redundant paths supported by the MEC
system for the MEC application instance.
The UALCMP authorizes the request from the device application.
The request is forwarded to the MEC system level management,
which makes the decision on granting the context creation
request. The MEC orchestrator triggers the creation of the
application context in the MEC system, including the information
about reliability and availability requirements. The UALCMP
request the context creation to the MEAO, this request including
the reliability and availability requirements of the application.
The MEAO selects where to instantiate the application (meaning
the MEC host and MEC platform), so it can meet all the
requirements.
2. The MEP request to the local RAW ctrl to establish the
connectivity between the app and the UE meeting the indicated
reliability and availability requirements. This involves
additional steps between the RAW ctrl, the RAW PSE and the RAW
nodes that are part of the established path(s), as described in
[I-D.bernardos-raw-mec].
3. The UALCMP returns the 201 Created response to the UE with the
message body containing the data structure of the created
application context.
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3.3. Extended Application context update to support reliability and
availability information/capabilities
Here we specify how the UE is augmented with the capability to
request the update of the context of a MEC app including requirements
about reliability and availability. One example would be
communicating new reliability/availability requirements.
+--------------+
+----------+ | MEC host |
+--+ | UALCMP | +---+ +----+ +----+ +----+ | +----+ |
|UE| +---+----+-+ |RAW| |MEAO| |RAW | |RAW | | +---+ |RAW | |
+--+ | |RAW | |PSE| +----+ |node| |node| | |MEP| |ctrl| |
| | |ctrl| +---+ | +----+ +----+ | +---+ +----+ |
| | +----+ | | | | +---|------|---+
| | | |<..RAW.........>| | | |
| | | |<..signalling..........>| | |
| | | | | | | | |
|1.PUT ../app_contexts| | | | | |
| {contextID} (AppContext) | | | | |
|....>| | | | | | | |
| |..MEC signalling......>|..MEC signalling........>| |
| | | | | | | 2.MEC-to-RAW
| | | | | | | |.....>|
| | | |<..2.RAW................................|
| | |<.........|...signalling..>| | | |
| | | |.......................>| | |
| | | | | | | |<.....|
| |<......MEC.signalling..|<........MEC signalling..| |
| | | | | | | | |
|3.204 No Content | | | | | |
|<....| | | | | | | |
| | | | | | | | |
Figure 5: Application context update
Figure 5 shows an exemplary signaling flow diagram. We next explain
each of the steps illustrated in the figure:
1. An application running on the UE making use of a MEC app might
change its requirements for the MEC app and associated
reliability and availability (for example, in an Industry 4.0
scenario, a robot control app might be required less latency to
improve its precision). The UE updates a specific application
context by sending a PUT request to the resource within the MEC
system that represents it, with the message body containing the
modified data structure of AppContext in which only the callback
reference and/or application location constraints, and/or the
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application reliability and availability requirements (e.g.,
assured bandwidth, latency and reliability) may be updated.
2. Through interactions with the RAW ctrl, the RAW PSE is indicated
to perform the required updates in the RAW network (via
signalling with RAW nodes).
3. The UALCMP returns a "204 No Content" response.
3.4. Receiving extended notification events
Here we specify how the UE can receive updates about the RAW
connectivity experienced by a MEC application, so it can react in
time (e.g., implementing changes at the application level or
selecting another point of attachment/slice).
+--------------+
+----------+ | MEC host |
+--+ | UALCMP | +---+ +----+ +----+ +----+ | +----+ |
|UE| +---+----+-+ |RAW| |MEAO| |RAW | |RAW | | +---+ |RAW | |
+--+ | |RAW | |PSE| +----+ |node| |node| | |MEP| |ctrl| |
| | |ctrl| +---+ | +----+ +----+ | +---+ +----+ |
| | +----+ | | | | +---|------|---+
| | | |<..RAW.........>| | | |
| | | |<..signalling..........>| | |
| | | | | | | | |
| | | Event occurs (e.g., it is no longer | |
| | | to keep assured RAW conditions) | |
| | | | | | | | |
| | | |1.MEC-to-RAW | | | |
| | | |.......................................>|
| | | | | | | |<.....|
| |<......MEC signalling..|<........MEC signalling..| |
| | | | | | | | |
|2.POST ../callback_ref | | | | |
| ({Notification}) | | | | | |
|<....| | | | | | | |
|3.204 No Content | | | | | |
|....>| | | | | | | |
| | | | | | | | |
Figure 6: Receiving notification events
Figure 5 shows an exemplary signaling flow diagram. We next explain
each of the steps illustrated in the figure:
1. If a change of the assured RAW conditions happens (which is
detected via RAW OAM mechanisms, out of the scope of this
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document, and then notified to the MEC platform), this event
reaches the MEC orchestrator, and finally the UALCMP.
2. The UALCMP sends a POST message to the callback reference address
provided by the device application as part of application context
creation, with the message body containing the {Notification}
data structure. The variable {Notification} is replaced with the
data type specified for different notification events as
specified in ETSI MEC standards, extended to include a
modification to the RAW conditions offered to the user
application instance:
* Updated assured round trip time in milliseconds supported by
the MEC system for the MEC application instance.
* Updated assured connection bandwidth in kbit/s for the use of
the MEC application instance.
* Updated maximum percentage of packets failed.
* Updated assured jitter in milliseconds supported by the MEC
system for the MEC application instance.
* Updated assured number of redundant paths supported by the MEC
system for the MEC application instance.
3. The device application sends a "204 No Content" response to the
UALCMP.
4. IANA Considerations
TBD.
5. Security Considerations
TBD.
6. Acknowledgments
The work in this draft will be further developed and explored under
the framework of the H2020 5Growth (Grant 856709).
7. Informative References
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[I-D.bernardos-raw-mec]
Bernardos, C. and A. Mourad, "Extensions to enable
wireless reliability and availability in multi- access
edge deployments", draft-bernardos-raw-mec-01 (work in
progress), January 2021.
[I-D.ietf-raw-use-cases]
Papadopoulos, G., Thubert, P., Theoleyre, F., and C.
Bernardos, "RAW use cases", draft-ietf-raw-use-cases-00
(work in progress), October 2020.
[I-D.pthubert-raw-architecture]
Thubert, P., Papadopoulos, G., and R. Buddenberg,
"Reliable and Available Wireless Architecture/Framework",
draft-pthubert-raw-architecture-05 (work in progress),
November 2020.
Authors' Addresses
Carlos J. Bernardos
Universidad Carlos III de Madrid
Av. Universidad, 30
Leganes, Madrid 28911
Spain
Phone: +34 91624 6236
Email: cjbc@it.uc3m.es
URI: http://www.it.uc3m.es/cjbc/
Alain Mourad
InterDigital Europe
Email: Alain.Mourad@InterDigital.com
URI: http://www.InterDigital.com/
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