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Network Working Group                                          X. de Foy
Internet-Draft                                                 A. Rahman
Intended status: Informational          InterDigital Communications, LLC
Expires: 11 January 2021                                    10 July 2020


                Impact of Mobility on Discovery in COIN
                 draft-defoy-coinrg-mobile-discovery-00

Abstract

   Service, data and resource discovery is an important aspect of
   computing in the network.  While this aspect has been studied,
   including in COINRG, this document looks more specifically at the
   influence of mobile devices on COIN discovery.  Related research
   challenges are described and discussed.

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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   This Internet-Draft will expire on 11 January 2021.

Copyright Notice

   Copyright (c) 2020 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
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   provided without warranty as described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Challenges  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Scalability . . . . . . . . . . . . . . . . . . . . . . .   3
       2.1.1.  Challenge Description . . . . . . . . . . . . . . . .   3
       2.1.2.  Discussion  . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Multiple Interfaces and Data Networks . . . . . . . . . .   4
       2.2.1.  Challenge Description . . . . . . . . . . . . . . . .   4
       2.2.2.  Discussion  . . . . . . . . . . . . . . . . . . . . .   5
     2.3.  Service Continuity  . . . . . . . . . . . . . . . . . . .   5
       2.3.1.  Challenge Description . . . . . . . . . . . . . . . .   6
       2.3.2.  Discussion  . . . . . . . . . . . . . . . . . . . . .   6
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   4.  Acknowledgment  . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Informative References  . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Discovery in COIN relates to edge services including computing
   resources, computing services and data.  In this document, we focus
   on the influence of mobile devices on discovery in COIN, both when
   mobile devices are consuming or producing edge computing services.
   We use the following terms:

   *  Edge computing service: a general concept including offering
      computing and storage resources to other devices or to a platform,
      through an API that enables allocating computing/storage
      resources, onboarding a program, running a program; offering a
      computing service such as an API to a software program running on
      the device; or offering a data service such as a data stream or an
      API to access data generated by, or stored on, the device.

   *  Edge computing service provider: a device or platform providing
      such a service.  We especially consider cases where a mobile
      device acts as a provider.

   *  Edge computing service consumer: a (possibly mobile) device
      discovering, requesting and obtaining access to such a service.

   *  Network provider: an entity providing network connectivity to the
      mobile devices discussed in this draft.  It can be a 5G network
      operator, or an enterprise or home network operator.

   This document is related, and aims to be complementary, to
   [I-D.mcbride-edge-data-discovery-overview], which studies data
   discovery in COIN environments.



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   Service and resource discovery has been studied more generally for
   distributed edge computing.  For example [Varghese] identifies
   challenges including scaling, support for heterogeneous environments,
   support for real-time benchmarking.  As examples of system designs,
   [Gedeon] describes a distributed brokering system for discovery, and
   [Mastorakis] describes an ICN-based discovery scheme.

2.  Challenges

   Due to the mobility of service/data/resource providers and consumers,
   service discovery is typically used more often when involving mobile
   devices (i.e. not only during initial service setup, but continuously
   during service operation), and failures can lead to less stable
   services.  Mobility also brings specific challenges to service
   discovery in edge computing, in term of scalability, support for
   multiple and frequently changing network interfaces, and service
   continuity.

2.1.  Scalability

2.1.1.  Challenge Description

   From its distributed nature, edge computing generally improves
   scalibility of services/data/resources.  However, this puts more
   demand on mobile networks.  Scalability is a concern with discovery
   involving wireless mobile devices, especially because of the scarce
   nature of the wireless medium: mobile devices should use as little
   resources as practical to determine whether a service or resource is
   present, or to advertise their own service/resource.  Additionally,
   multicast over wireless is also expensive, as described in section
   2.2 of [RFC7558].  Moreover, even beyond the first wireless hop,
   dense deployments of mobile devices can result in high churn, which
   may generate an unwanted constant traffic activity for edge computing
   related service discovery in edge networks.

2.1.2.  Discussion

   A common strategy to increase service discovery scalability for
   wireless devices is to use pre-attachment or pre-connection discovery
   methods, as an initial stage for service discovery.  These methods
   provide information to the mobile device, to help narrow down the
   number of access points or data networks that are eligible to access
   the service.








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   *  One example is 802.11aq [IEEE-802.11aq], where hashes or bloom
      filters summarizing service names can be advertised by access
      points, prior to attachment; the mobile device can also send a
      service-specific request through the access point, also prior to
      attachment. 802.11aq uses service names as defined in [RFC6335].

   *  A 5G mobile device will be able to send a request to an
      application function (Edge Enabler Server), including parameters
      such as application client ID, requested response time, bandwidth,
      compute, memory and storage resources.  The reply will include
      information on the selected edge application server
      [_3GPP.23.558].

   As illustrated in multiple edge computing system designs ([Kaur],
   [_3GPP.23.558], [Gedeon]), as part of the discovery process a network
   node may collect QoS requirements from the service consumer, and then
   select or reserve resources for this service.  One challenge may be
   to limit the impact of this step on edge computing discovery.
   Collecting and using requirements may for example be performed by the
   service consumer, when used with passive discovery methods that
   provide enough information.  Collecting and using requirements may
   also occur at different stages of discovery (e.g., pre-connection, or
   later after connecting to an edge computing platform).  Finally, in
   some cases this step may not be needed at all (e.g., for a best
   effort edge computing service, or if a QoS is implied for a given
   service).

2.2.  Multiple Interfaces and Data Networks

2.2.1.  Challenge Description

   Mobile devices can have multiple radios, resulting in the added
   challenge of determining which network interface(s) to use for
   discovery, either initially or for session continuity when
   relocating.  Additionally, even once a mobile device is attached to
   an access point, multiple (local- and wide-area) data network may be
   locally accessible, also resulting in multiple network interfaces on
   the device.  The problem of dealing with multiple interfaces is not
   unique to mobile device (e.g. routers participating in edge computing
   will have similar issues), however with mobile devices network
   interfaces are much more dynamic as part of normal operation.  This
   problem area has been discussed in MIF [I-D.cao-mif-srv-dis-ps],
   however not within the context of edge computing.








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2.2.2.  Discussion

   One strategy is to connect to several available access points and
   discover service instances concurrently, following a happy eyeball
   strategy [RFC8305].  Otherwise, a mobile device should select the
   network interfaces to use based on available information (including
   from pre-attachment/pre-connection methods above).  Once a connection
   is established, multiple discovery methods are available:

   *  In passive discovery methods network nodes advertise information
      to end devices, without requiring a specific request.  One
      possibility is to extend existing passive discovery methods for
      edge computing services.  For example:

      -  Leveraging provisioning domains (e.g., listing available
         service and instance names),

      -  Leveraging router advertisements (e.g., advertising Virtual
         Infrastructure Management resources, as described in
         [I-D.bernardos-sfc-fog-ran])

      -  Leveraging DHCP signalling (e.g., advertising the IP address of
         an edge computing platform server).

   *  Active discovery protocols include DNS-based discovery methods
      such as DNS-SD [RFC6763] and mDNS [RFC6762].  Mobile service
      producers can make themselves known using multicast (for mDNS) or
      register with the DNS system, e.g. using [I-D.ietf-dnssd-srp]

   One additional challenge is to make multi-interface discovery methods
   available as early as possible to save resources (e.g. pre-
   attachment/connection).  For example, a recent proposal in 5G is to
   use policy information to deploy provisioning domains on mobile
   devices prior to establishing a PDU connection: the mobile device can
   then look at provisioning domain attributes and determine which data
   network to use and related connection parameters [_3GPP.23.748].

2.3.  Service Continuity













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2.3.1.  Challenge Description

   Service continuity and latency can also be impacted by service or
   resource discovery.  When a mobile device (either service consumer or
   provider) moves to a new location, a new service instance may need to
   be discovered to maintain the level of service (e.g. keep rendering
   or processing video without losing a frame or more than _n_ frames).
   In cases where edge computing is used for real time applications with
   stringent requirements, the time used to discover a new edge
   computing instance influences the level of service.

2.3.2.  Discussion

   Mobile devices are faced with the challenge to select a proper
   service continuity strategy, each time a new access point becomes
   available or unavailable.  Edge computing service discovery methods
   may need to provide information not only to facilitate this
   selection, but to factor in service continuity strategies within the
   discovery process.  Typical edge computing service continuity
   strategies are: a mobile device may keep connecting to the same
   serving instance through a new AP (using connection migration or
   multiple paths); or a mobile device may discover a new instance and
   then use it to replace or complement its connection to the first
   instance.  For example, a mobile device may be in range of 2 APs, one
   suitable for the first strategy and the other one suitable for the
   second.

3.  Security Considerations

   One concern is for the consumer to trust that discovery information
   relayed by the network provider is legitimate, to avoid, for example,
   phishing or denial of service attacks.  Another concern is for the
   provider to limit the amount of information given to unauthenticated
   requesters.  For pre-connection discovery, these types of concerns
   are typically addressed by authorization (e.g. in 5G, a device must
   be attached to the network prior to discover services) or hashing
   (e.g. in 802.11aq service names are advertised through hashes or
   bloom filters).

4.  Acknowledgment

   The authors would like to thank Chonggang Wang for his valuable
   comments and suggestions on this document.

5.  Informative References






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   [Gedeon]   Gedeon, J., Meurisch, C., Bhat, D., Stein, M., Wang, L.,
              and M. Muhlhauser, "Router-Based Brokering for Surrogate
              Discovery in Edge Computing", IEEE 37th International
              Conference on Distributed Computing Systems Workshops
              (ICDCSW) , 2017,
              <https://ieeexplore.ieee.org/abstract/document/7979808>.

   [I-D.bernardos-sfc-fog-ran]
              Bernardos, C., Rahman, A., and A. Mourad, "Service
              Function Chaining Use Cases in Fog RAN", Work in Progress,
              Internet-Draft, draft-bernardos-sfc-fog-ran-07, 11 March
              2020, <http://www.ietf.org/internet-drafts/draft-
              bernardos-sfc-fog-ran-07.txt>.

   [I-D.cao-mif-srv-dis-ps]
              Cao, Z. and A. Ding, "Service Discovery in a Multiple
              Connection Environment: Problem Statement", Work in
              Progress, Internet-Draft, draft-cao-mif-srv-dis-ps-03, 27
              August 2013, <http://www.ietf.org/internet-drafts/draft-
              cao-mif-srv-dis-ps-03.txt>.

   [I-D.ietf-dnssd-srp]
              Cheshire, S. and T. Lemon, "Service Registration Protocol
              for DNS-Based Service Discovery", Work in Progress,
              Internet-Draft, draft-ietf-dnssd-srp-02, 8 July 2019,
              <http://www.ietf.org/internet-drafts/draft-ietf-dnssd-srp-
              02.txt>.

   [I-D.mcbride-edge-data-discovery-overview]
              McBride, M., Kutscher, D., Schooler, E., and C. Bernardos,
              "Edge Data Discovery for COIN", Work in Progress,
              Internet-Draft, draft-mcbride-edge-data-discovery-
              overview-03, 29 January 2020, <http://www.ietf.org/
              internet-drafts/draft-mcbride-edge-data-discovery-
              overview-03.txt>.

   [IEEE-802.11aq]
              IEEE, ., "IEEE 802.11 Specifications Amendment 5:
              Preassociation Discovery", IEEE Std 802.11aq-2018 , 2018.

   [Kaur]     Kaur, K., Dhand, T., Kumar, N., and S. Zeadally,
              "Container-as-a-service at the edge: Trade-off between
              energy efficiency and service availability at fog nano
              data centers", IEEE wireless communications , 2017,
              <https://ieeexplore.ieee.org/document/7955911>.






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   [Mastorakis]
              Mastorakis, S. and A. Mtibaa, "Towards Service Discovery
              and Invocation in Data-Centric Edge Networks", IEEE 27th
              International Conference on Network Protocols (ICNP) ,
              2019,
              <https://ieeexplore.ieee.org/abstract/document/8888081>.

   [RFC6335]  Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
              Cheshire, "Internet Assigned Numbers Authority (IANA)
              Procedures for the Management of the Service Name and
              Transport Protocol Port Number Registry", BCP 165,
              RFC 6335, DOI 10.17487/RFC6335, August 2011,
              <https://www.rfc-editor.org/info/rfc6335>.

   [RFC6762]  Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
              DOI 10.17487/RFC6762, February 2013,
              <https://www.rfc-editor.org/info/rfc6762>.

   [RFC6763]  Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
              <https://www.rfc-editor.org/info/rfc6763>.

   [RFC7558]  Lynn, K., Cheshire, S., Blanchet, M., and D. Migault,
              "Requirements for Scalable DNS-Based Service Discovery
              (DNS-SD) / Multicast DNS (mDNS) Extensions", RFC 7558,
              DOI 10.17487/RFC7558, July 2015,
              <https://www.rfc-editor.org/info/rfc7558>.

   [RFC8305]  Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2:
              Better Connectivity Using Concurrency", RFC 8305,
              DOI 10.17487/RFC8305, December 2017,
              <https://www.rfc-editor.org/info/rfc8305>.

   [Varghese] Varghese, B., Wang, N., Barbhuiya, S., Kilpatrick, P., and
              D.S. Nikolopoulos, "Challenges and Opportunities in Edge
              Computing", IEEE International Conference on Smart Cloud ,
              2016, <https://ieeexplore.ieee.org/document/7796149>.

   [_3GPP.23.558]
              3GPP, ., "Architecture for enabling Edge Applications;
              (Release 17)", 3GPP TS 23.558 , 2020,
              <http://www.3gpp.org/ftp/Specs/html-info/23558.htm>.

   [_3GPP.23.748]
              3GPP, ., "Study on enhancement of support for Edge
              Computing in 5G Core network (5GC)", 3GPP TS 23.748 ,
              2020, <http://www.3gpp.org/ftp/Specs/html-info/23748.htm>.




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Authors' Addresses

   Xavier de Foy
   InterDigital Communications, LLC
   1000 Sherbrooke West
   Montreal  H3A 3G4
   Canada

   Email: xavier.defoy@interdigital.com


   Akbar Rahman
   InterDigital Communications, LLC
   1000 Sherbrooke West
   Montreal  H3A 3G4
   Canada

   Email: akbar.rahman@interdigital.com

































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