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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. de Foy & Rahman Expires 11 January 2021 [Page 1] Internet-Draft Mobile/Wireless IoT Edge Computing July 2020 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. de Foy & Rahman Expires 11 January 2021 [Page 2] Internet-Draft Mobile/Wireless IoT Edge Computing July 2020 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. de Foy & Rahman Expires 11 January 2021 [Page 3] Internet-Draft Mobile/Wireless IoT Edge Computing July 2020 * 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. de Foy & Rahman Expires 11 January 2021 [Page 4] Internet-Draft Mobile/Wireless IoT Edge Computing July 2020 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 de Foy & Rahman Expires 11 January 2021 [Page 5] Internet-Draft Mobile/Wireless IoT Edge Computing July 2020 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 de Foy & Rahman Expires 11 January 2021 [Page 6] Internet-Draft Mobile/Wireless IoT Edge Computing July 2020 [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, . [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, . [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, . [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, . [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, . [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, . de Foy & Rahman Expires 11 January 2021 [Page 7] Internet-Draft Mobile/Wireless IoT Edge Computing July 2020 [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, . [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, . [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, DOI 10.17487/RFC6762, February 2013, . [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013, . [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, . [RFC8305] Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2: Better Connectivity Using Concurrency", RFC 8305, DOI 10.17487/RFC8305, December 2017, . [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, . [_3GPP.23.558] 3GPP, ., "Architecture for enabling Edge Applications; (Release 17)", 3GPP TS 23.558 , 2020, . [_3GPP.23.748] 3GPP, ., "Study on enhancement of support for Edge Computing in 5G Core network (5GC)", 3GPP TS 23.748 , 2020, . de Foy & Rahman Expires 11 January 2021 [Page 8] Internet-Draft Mobile/Wireless IoT Edge Computing July 2020 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 de Foy & Rahman Expires 11 January 2021 [Page 9]