Terminal-based joint selection and configuration of MEC host and RAW network
draft-bernardos-raw-joint-selection-raw-mec-01

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Authors Carlos Bernardos  , Alain Mourad 
Last updated 2021-09-09
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RAW WG                                                     CJ. Bernardos
Internet-Draft                                                      UC3M
Intended status: Standards Track                               A. Mourad
Expires: March 14, 2022                                     InterDigital
                                                      September 10, 2021

  Terminal-based joint selection and configuration of MEC host and RAW
                                network
             draft-bernardos-raw-joint-selection-raw-mec-01

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 March 14, 2022.

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   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   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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Internet-Draft         Joint RAW and MEC selection        September 2021

   [I-D.bernardos-raw-mec]
              Bernardos, C. J. and A. Mourad, "Extensions to enable
              wireless reliability and availability in multi- access
              edge deployments", draft-bernardos-raw-mec-02 (work in
              progress), July 2021.

   [I-D.ietf-raw-use-cases]
              Papadopoulos, G. Z., Thubert, P., Theoleyre, F., and C. J.
              Bernardos, "RAW use cases", draft-ietf-raw-use-cases-02
              (work in progress), July 2021.

   [I-D.pthubert-raw-architecture]
              Thubert, P., Papadopoulos, G. Z., and L. Berger, "Reliable
              and Available Wireless Architecture/Framework", draft-
              pthubert-raw-architecture-09 (work in progress), July
              2021.

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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