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| author | Thomas Voss <mail@thomasvoss.com> | 2024-11-27 20:54:24 +0100 |
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| committer | Thomas Voss <mail@thomasvoss.com> | 2024-11-27 20:54:24 +0100 |
| commit | 4bfd864f10b68b71482b35c818559068ef8d5797 (patch) | |
| tree | e3989f47a7994642eb325063d46e8f08ffa681dc /doc/rfc/rfc9556.txt | |
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diff --git a/doc/rfc/rfc9556.txt b/doc/rfc/rfc9556.txt new file mode 100644 index 0000000..5aa6c1f --- /dev/null +++ b/doc/rfc/rfc9556.txt @@ -0,0 +1,1751 @@ + + + + +Internet Research Task Force (IRTF) J. Hong +Request for Comments: 9556 ETRI +Category: Informational Y-G. Hong +ISSN: 2070-1721 Daejeon University + X. de Foy + InterDigital Communications, LLC + M. Kovatsch + Huawei Technologies Duesseldorf GmbH + E. Schooler + University of Oxford + D. Kutscher + HKUST(GZ) + April 2024 + + + Internet of Things (IoT) Edge Challenges and Functions + +Abstract + + Many Internet of Things (IoT) applications have requirements that + cannot be satisfied by centralized cloud-based systems (i.e., cloud + computing). These include time sensitivity, data volume, + connectivity cost, operation in the face of intermittent services, + privacy, and security. As a result, IoT is driving the Internet + toward edge computing. This document outlines the requirements of + the emerging IoT edge and its challenges. It presents a general + model and major components of the IoT edge to provide a common basis + for future discussions in the Thing-to-Thing Research Group (T2TRG) + and other IRTF and IETF groups. This document is a product of the + IRTF T2TRG. + +Status of This Memo + + This document is not an Internet Standards Track specification; it is + published for informational purposes. + + This document is a product of the Internet Research Task Force + (IRTF). The IRTF publishes the results of Internet-related research + and development activities. These results might not be suitable for + deployment. This RFC represents the consensus of the Thing-to-Thing + Research Group of the Internet Research Task Force (IRTF). Documents + approved for publication by the IRSG are not candidates for any level + of Internet Standard; see Section 2 of RFC 7841. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + https://www.rfc-editor.org/info/rfc9556. + +Copyright Notice + + Copyright (c) 2024 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 + (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 and restrictions with respect + to this document. + +Table of Contents + + 1. Introduction + 2. Background + 2.1. Internet of Things (IoT) + 2.2. Cloud Computing + 2.3. Edge Computing + 2.4. Examples of IoT Edge Computing Use Cases + 3. IoT Challenges Leading toward Edge Computing + 3.1. Time Sensitivity + 3.2. Connectivity Cost + 3.3. Resilience to Intermittent Services + 3.4. Privacy and Security + 4. IoT Edge Computing Functions + 4.1. Overview of IoT Edge Computing + 4.2. General Model + 4.3. OAM Components + 4.3.1. Resource Discovery and Authentication + 4.3.2. Edge Organization and Federation + 4.3.3. Multi-Tenancy and Isolation + 4.4. Functional Components + 4.4.1. In-Network Computation + 4.4.2. Edge Storage and Caching + 4.4.3. Communication + 4.5. Application Components + 4.5.1. IoT Device Management + 4.5.2. Data Management and Analytics + 4.6. Simulation and Emulation Environments + 5. Security Considerations + 6. Conclusion + 7. IANA Considerations + 8. Informative References + Acknowledgements + Authors' Addresses + +1. Introduction + + At the time of writing, many IoT services leverage cloud computing + platforms because they provide virtually unlimited storage and + processing power. The reliance of IoT on back-end cloud computing + provides additional advantages, such as scalability and efficiency. + At the time of writing, IoT systems are fairly static with respect to + integrating and supporting computation. It is not that there is no + computation, but that systems are often limited to static + configurations (edge gateways and cloud services). + + However, IoT devices generate large amounts of data at the edges of + the network. To meet IoT use case requirements, data is increasingly + being stored, processed, analyzed, and acted upon close to the data + sources. These requirements include time sensitivity, data volume, + connectivity cost, and resiliency in the presence of intermittent + connectivity, privacy, and security, which cannot be addressed by + centralized cloud computing. A more flexible approach is necessary + to address these needs effectively. This involves distributing + computing (and storage) and seamlessly integrating it into the edge- + cloud continuum. We refer to this integration of edge computing and + IoT as "IoT edge computing". This document describes the related + background, use cases, challenges, system models, and functional + components. + + Owing to the dynamic nature of the IoT edge computing landscape, this + document does not list existing projects in this field. Section 4.1 + presents a high-level overview of the field based on a limited review + of standards, research, and open-source and proprietary products in + [EDGE-COMPUTING-BACKGROUND]. + + This document represents the consensus of the Thing-to-Thing Research + Group (T2TRG). It has been reviewed extensively by the research + group members who are actively involved in the research and + development of the technology covered by this document. It is not an + IETF product and is not a standard. + +2. Background + +2.1. Internet of Things (IoT) + + Since the term "Internet of Things" was coined by Kevin Ashton in + 1999 while working on Radio-Frequency Identification (RFID) + technology [Ashton], the concept of IoT has evolved. At the time of + writing, it reflects a vision of connecting the physical world to the + virtual world of computers using (often wireless) networks over which + things can send and receive information without human intervention. + Recently, the term has become more literal by connecting things to + the Internet and converging on Internet and web technologies. + + A "Thing" is a physical item made available in the IoT, thereby + enabling digital interaction with the physical world for humans, + services, and/or other Things [REST-IOT]. In this document, we will + use the term "IoT device" to designate the embedded system attached + to the Thing. + + Resource-constrained Things, such as sensors, home appliances, and + wearable devices, often have limited storage and processing power, + which can create challenges with respect to reliability, performance, + energy consumption, security, and privacy [Lin]. Some, less- + resource-constrained Things, can generate a voluminous amount of + data. This range of factors led to IoT designs that integrate Things + into larger distributed systems, for example, edge or cloud computing + systems. + +2.2. Cloud Computing + + Cloud computing has been defined in [NIST]: + + | Cloud computing is a model for enabling ubiquitous, convenient, + | on-demand network access to a shared pool of configurable + | computing resources (e.g., networks, servers, storage, + | applications, and services) that can be rapidly provisioned and + | released with minimal management effort or service provider + | interaction. + + The low cost and massive availability of storage and processing power + enabled the realization of another computing model in which + virtualized resources can be leased in an on-demand fashion and + provided as general utilities. Platform-as-a-Service (PaaS) and + cloud computing platforms widely adopted this paradigm for delivering + services over the Internet, gaining both economical and technical + benefits [Botta]. + + At the time of writing, an unprecedented volume and variety of data + is generated by Things, and applications deployed at the network edge + consume this data. In this context, cloud-based service models are + not suitable for some classes of applications that require very short + response times, require access to local personal data, or generate + vast amounts of data. These applications may instead leverage edge + computing. + +2.3. Edge Computing + + Edge computing, also referred to as "fog computing" in some settings, + is a new paradigm in which substantial computing and storage + resources are placed at the edge of the Internet, close to mobile + devices, sensors, actuators, or machines. Edge computing happens + near data sources [Mahadev] as well as close to where decisions are + made or where interactions with the physical world take place + ("close" here can refer to a distance that is topological, physical, + latency-based, etc.). It processes both downstream data (originating + from cloud services) and upstream data (originating from end devices + or network elements). The term "fog computing" usually represents + the notion of multi-tiered edge computing, that is, several layers of + compute infrastructure between end devices and cloud services. + + An edge device is any computing or networking resource residing + between end-device data sources and cloud-based data centers. In + edge computing, end devices consume and produce data. At the network + edge, devices not only request services and information from the + cloud but also handle computing tasks including processing, storing, + caching, and load balancing on data sent to and from the cloud [Shi]. + This does not preclude end devices from hosting computation + themselves, when possible, independently or as part of a distributed + edge computing platform. + + Several Standards Developing Organizations (SDOs) and industry forums + have provided definitions of edge and fog computing: + + * ISO defines edge computing as a "form of distributed computing in + which significant processing and data storage takes place on nodes + which are at the edge of the network" [ISO_TR]. + + * ETSI defines multi-access edge computing as a "system which + provides an IT service environment and cloud-computing + capabilities at the edge of an access network which contains one + or more type of access technology, and in close proximity to its + users" [ETSI_MEC_01]. + + * The Industry IoT Consortium (IIC) (now incorporating what was + formerly OpenFog) defines fog computing as "a horizontal, system- + level architecture that distributes computing, storage, control + and networking functions closer to the users along a cloud-to- + thing continuum" [OpenFog]. + + Based on these definitions, we can summarize a general philosophy of + edge computing as distributing the required functions close to users + and data, while the difference to classic local systems is the usage + of management and orchestration features adopted from cloud + computing. + + Actors from various industries approach edge computing using + different terms and reference models, although, in practice, these + approaches are not incompatible and may integrate with each other: + + * The telecommunication industry tends to use a model where edge + computing services are deployed over a Network Function + Virtualization (NFV) infrastructure, at aggregation points, or in + proximity to the user equipment (e.g., gNodeBs) [ETSI_MEC_03]. + + * Enterprise and campus solutions often interpret edge computing as + an "edge cloud", that is, a smaller data center directly connected + to the local network (often referred to as "on-premise"). + + * The automation industry defines the edge as the connection point + between IT and Operational Technology (OT). Hence, edge computing + sometimes refers to applying IT solutions to OT problems, such as + analytics, more-flexible user interfaces, or simply having more + computing power than an automation controller. + +2.4. Examples of IoT Edge Computing Use Cases + + IoT edge computing can be used in home, industry, grid, healthcare, + city, transportation, agriculture, and/or educational scenarios. + Here, we discuss only a few examples of such use cases to identify + differentiating requirements, providing references to other use + cases. + + *Smart Factory* + As part of the Fourth Industrial Revolution, smart factories run + real-time processes based on IT technologies, such as artificial + intelligence and big data. Even a very small environmental change + in a smart factory can lead to a situation in which production + efficiency decreases or product quality problems occur. + Therefore, simple but time-sensitive processing can be performed + at the edge, for example, controlling the temperature and humidity + in the factory or operating machines based on the real-time + collection of the operational status of each machine. However, + data requiring highly precise analysis, such as machine life-cycle + management or accident risk prediction, can be transferred to a + central data center for processing. + + The use of edge computing in a smart factory [Argungu] can reduce + the cost of network and storage resources by reducing the + communication load to the central data center or server. It is + also possible to improve process efficiency and facility asset + productivity through real-time prediction of failures and to + reduce the cost of failure through preliminary measures. In the + existing manufacturing field, production facilities are manually + run according to a program entered in advance; however, edge + computing in a smart factory enables tailoring solutions by + analyzing data at each production facility and machine level. + Digital twins [Jones] of IoT devices have been jointly used with + edge computing in industrial IoT scenarios [Chen]. + + *Smart Grid* + In future smart-city scenarios, the smart grid will be critical in + ensuring highly available and efficient energy control in city- + wide electricity management [Mehmood]. Edge computing is expected + to play a significant role in these systems to improve the + transmission efficiency of electricity, to react to and restore + power after a disturbance, to reduce operation costs, and to reuse + energy effectively since these operations involve local decision- + making. In addition, edge computing can help monitor power + generation and power demand and make local electrical energy + storage decisions in smart grid systems. + + *Smart Agriculture* + Smart agriculture integrates information and communication + technologies with farming technology. Intelligent farms use IoT + technology to measure and analyze parameters, such as the + temperature, humidity, sunlight, carbon dioxide, and soil quality, + in crop cultivation facilities. Depending on the analysis + results, control devices are used to set the environmental + parameters to an appropriate state. Remote management is also + possible through mobile devices, such as smartphones. + + In existing farms, simple systems, such as management according to + temperature and humidity, can be easily and inexpensively + implemented using IoT technology [Tanveer]. Field sensors gather + data on field and crop condition. This data is then transmitted + to cloud servers that process data and recommend actions. The use + of edge computing can reduce the volume of back-and-forth data + transmissions significantly, resulting in cost and bandwidth + savings. Locally generated data can be processed at the edge, and + local computing and analytics can drive local actions. With edge + computing, it is easy for farmers to select large amounts of data + for processing, and data can be analyzed even in remote areas with + poor access conditions. Other applications include enabling + dashboarding, for example, to visualize the farm status, as well + as enhancing Extended Reality (XR) applications that require edge + audio and/or video processing. As the number of people working on + farming has been decreasing over time, increasing automation + enabled by edge computing can be a driving force for future smart + agriculture [OGrady]. + + *Smart Construction* + Safety is critical at construction sites. Every year, many + construction workers lose their lives because of falls, + collisions, electric shocks, and other accidents [BigRentz]. + Therefore, solutions have been developed to improve construction + site safety, including the real-time identification of workers, + monitoring of equipment location, and predictive accident + prevention. To deploy these solutions, many cameras and IoT + sensors have been installed on construction sites to measure + noise, vibration, gas concentration, etc. Typically, the data + generated from these measurements is collected in on-site gateways + and sent to remote cloud servers for storage and analysis. Thus, + an inspector can check the information stored on the cloud server + to investigate an incident. However, this approach can be + expensive because of transmission costs (for example, of video + streams over a mobile network connection) and because usage fees + of private cloud services. + + Using edge computing [Yue], data generated at the construction + site can be processed and analyzed on an edge server located + within or near the site. Only the result of this processing needs + to be transferred to a cloud server, thus reducing transmission + costs. It is also possible to locally generate warnings to + prevent accidents in real time. + + *Self-Driving Car* + Edge computing plays a crucial role in safety-focused self-driving + car systems [Badjie]. With a multitude of sensors, such as high- + resolution cameras, radars, Light Detection and Ranging (LiDAR) + systems, sonar sensors, and GPS systems, autonomous vehicles + generate vast amounts of real-time data. Local processing + utilizing edge computing nodes allows for efficient collection and + analysis of this data to monitor vehicle distances and road + conditions and respond promptly to unexpected situations. + Roadside computing nodes can also be leveraged to offload tasks + when necessary, for example, when the local processing capacity of + the car is insufficient because of hardware constraints or a large + data volume. + + For instance, when the car ahead slows, a self-driving car adjusts + its speed to maintain a safe distance, or when a roadside signal + changes, it adapts its behavior accordingly. In another example, + cars equipped with self-parking features utilize local processing + to analyze sensor data, determine suitable parking spots, and + execute precise parking maneuvers without relying on external + processing or connectivity. It is also possible to use in-cabin + cameras coupled with local processing to monitor the driver's + attention level and detect signs of drowsiness or distraction. + The system can issue warnings or implement preventive measures to + ensure driver safety. + + Edge computing empowers self-driving cars by enabling real-time + processing, reducing latency, enhancing data privacy, and + optimizing bandwidth usage. By leveraging local processing + capabilities, self-driving cars can make rapid decisions, adapt to + changing environments, and ensure safer and more efficient + autonomous driving experiences. + + *Digital Twin* + A digital twin can simulate different scenarios and predict + outcomes based on real-time data collected from the physical + environment. This simulation capability empowers proactive + maintenance, optimization of operations, and the prediction of + potential issues or failures. Decision makers can use digital + twins to test and validate different strategies, identify + inefficiencies, and optimize performance [CertMagic]. + + With edge computing, real-time data is collected, processed, and + analyzed directly at the edge, allowing for the accurate + monitoring and simulation of physical assets. Moreover, edge + computing effectively minimizes latency, enabling rapid responses + to dynamic conditions as computational resources are brought + closer to the physical object. Running digital twin processing at + the edge enables organizations to obtain timely insights and make + informed decisions that maximize efficiency and performance. + + *Other Use Cases* + Artificial intelligence (AI) and machine learning (ML) systems at + the edge empower real-time analysis, faster decision-making, + reduced latency, improved operational efficiency, and personalized + experiences across various industries by bringing AI and ML + capabilities closer to edge devices. + + In addition, oneM2M has studied several IoT edge computing use + cases, which are documented in [oneM2M-TR0001], [oneM2M-TR0018], + and [oneM2M-TR0026]. The edge-computing-related requirements + raised through the analysis of these use cases are captured in + [oneM2M-TS0002]. + +3. IoT Challenges Leading toward Edge Computing + + This section describes the challenges faced by the IoT that are + motivating the adoption of edge computing. These are distinct from + the research challenges applicable to IoT edge computing, some of + which are mentioned in Section 4. + + IoT technology is used with increasingly demanding applications in + domains such as industrial, automotive, and healthcare, which leads + to new challenges. For example, industrial machines, such as laser + cutters, produce over 1 terabyte of data per hour, and similar + amounts can be generated in autonomous cars [NVIDIA]. 90% of IoT + data is expected to be stored, processed, analyzed, and acted upon + close to the source [Kelly], as cloud computing models alone cannot + address these new challenges [Chiang]. + + Below, we discuss IoT use case requirements that are moving cloud + capabilities to be more proximate, distributed, and disaggregated. + +3.1. Time Sensitivity + + Often, many industrial control systems, such as manufacturing + systems, smart grids, and oil and gas systems, require stringent end- + to-end latency between the sensor and control nodes. While some IoT + applications may require latency below a few tens of milliseconds + [Weiner], industrial robots and motion control systems have use cases + for cycle times in the order of microseconds [IEC_IEEE_60802]. In + some cases, speed-of-light limitations may simply prevent cloud-based + solutions; however, this is not the only challenge relative to time + sensitivity. Guarantees for bounded latency and jitter ([RFC8578], + Section 7) are also important for industrial IoT applications. This + means that control packets must arrive with as little variation as + possible and within a strict deadline. Given the best-effort + characteristics of the Internet, this challenge is virtually + impossible to address without using end-to-end guarantees for + individual message delivery and continuous data flows. + +3.2. Connectivity Cost + + Some IoT deployments may not face bandwidth constraints when + uploading data to the cloud. Theoretically, both 5G and Wi-Fi 6 + networks top out at 10 gigabits per second (i.e., 4.5 terabytes per + hour), allowing the transfer of large amounts of uplink data. + However, the cost of maintaining continuous high-bandwidth + connectivity for such usage is unjustifiable and impractical for most + IoT applications. In some settings, for example, in aeronautical + communication, higher communication costs reduce the amount of data + that can be practically uploaded even further. Therefore, minimizing + reliance on high-bandwidth connectivity is a requirement; this can be + done, for example, by processing data at the edge and deriving + summarized or actionable insights that can be transmitted to the + cloud. + +3.3. Resilience to Intermittent Services + + Many IoT devices, such as sensors, actuators, and controllers, have + very limited hardware resources and cannot rely solely on their own + resources to meet their computing and/or storage needs. They require + reliable, uninterrupted, or resilient services to augment their + capabilities to fulfill their application tasks. This is difficult + and partly impossible to achieve using cloud services for systems + such as vehicles, drones, or oil rigs that have intermittent network + connectivity. Conversely, a cloud backend might want to access + device data even if the device is currently asleep. + +3.4. Privacy and Security + + When IoT services are deployed at home, personal information can be + learned from detected usage data. For example, one can extract + information about employment, family status, age, and income by + analyzing smart meter data [ENERGY]. Policy makers have begun to + provide frameworks that limit the usage of personal data and impose + strict requirements on data controllers and processors. Data stored + indefinitely in the cloud also increases the risk of data leakage, + for instance, through attacks on rich targets. + + It is often argued that industrial systems do not provide privacy + implications, as no personal data is gathered. However, data from + such systems is often highly sensitive, as one might be able to infer + trade secrets, such as the setup of production lines. Hence, owners + of these systems are generally reluctant to upload IoT data to the + cloud. + + Furthermore, passive observers can perform traffic analysis on + device-to-cloud paths. Therefore, hiding traffic patterns associated + with sensor networks can be another requirement for edge computing. + +4. IoT Edge Computing Functions + + We first look at the current state of IoT edge computing + (Section 4.1) and then define a general system model (Section 4.2). + This provides a context for IoT edge computing functions, which are + listed in Sections 4.3, 4.4, and 4.5. + +4.1. Overview of IoT Edge Computing + + This section provides an overview of the current (at the time of + writing) IoT edge computing field based on a limited review of + standards, research, and open-source and proprietary products in + [EDGE-COMPUTING-BACKGROUND]. + + IoT gateways, both open-source (such as EdgeX Foundry or Home Edge) + and proprietary products, represent a common class of IoT edge + computing products, where the gateway provides a local service on + customer premises and is remotely managed through a cloud service. + IoT communication protocols are typically used between IoT devices + and the gateway, including a Constrained Application Protocol (CoAP) + [RFC7252], Message Queuing Telemetry Transport (MQTT) [MQTT5], and + many specialized IoT protocols (such as Open Platform Communications + Unified Architecture (OPC UA) and Data Distribution Service (DDS) in + the industrial IoT space), while the gateway communicates with the + distant cloud typically using HTTPS. Virtualization platforms enable + the deployment of virtual edge computing functions (using Virtual + Machines (VMs) and application containers), including IoT gateway + software, on servers in the mobile network infrastructure (at base + stations and concentration points), edge data centers (in central + offices), and regional data centers located near central offices. + End devices are envisioned to become computing devices in forward- + looking projects but are not commonly used at the time of writing. + + In addition to open-source and proprietary solutions, a horizontal + IoT service layer is standardized by the oneM2M standards body to + reduce fragmentation, increase interoperability, and promote reuse in + the IoT ecosystem. Furthermore, ETSI Multi-access Edge Computing + (MEC) developed an IoT API [ETSI_MEC_33] that enables the deployment + of heterogeneous IoT platforms and provides a means to configure the + various components of an IoT system. + + Physical or virtual IoT gateways can host application programs that + are typically built using an SDK to access local services through a + programmatic API. Edge cloud system operators host their customers' + application VMs or containers on servers located in or near access + networks that can implement local edge services. For example, mobile + networks can provide edge services for radio network information, + location, and bandwidth management. + + Resilience in the IoT can entail the ability to operate autonomously + in periods of disconnectedness to preserve the integrity and safety + of the controlled system, possibly in a degraded mode. IoT devices + and gateways are often expected to operate in always-on and + unattended modes, using fault detection and unassisted recovery + functions. + + The life-cycle management of services and applications on physical + IoT gateways is generally cloud based. Edge cloud management + platforms and products (such as StarlingX, Akraino Edge Stack, or + proprietary products from major cloud providers) adapt cloud + management technologies (e.g., Kubernetes) to the edge cloud, that + is, to smaller, distributed computing devices running outside a + controlled data center. Typically, the service and application life + cycle is using an NFV-like management and orchestration model. + + The platform generally enables advertising or consuming services + hosted on the platform (e.g., the Mp1 interface in ETSI MEC supports + service discovery and communication), and enables communication with + local and remote endpoints (e.g., message routing function in IoT + gateways). The platform is usually extensible to edge applications + because it can advertise a service that other edge applications can + consume. The IoT communication services include protocol + translation, analytics, and transcoding. Communication between edge + computing devices is enabled in tiered or distributed deployments. + + An edge cloud platform may enable pass-through without storage or + local storage (e.g., on IoT gateways). Some edge cloud platforms use + distributed storage such as that provided by a distributed storage + platform (e.g., EdgeFS and Ceph) or, in more experimental settings, + by an Information-Centric Networking (ICN) network, for example, + systems such as Chipmunk [Chipmunk] and Kua [Kua] have been proposed + as distributed information-centric objects stores. External storage, + for example, on databases in a distant or local IT cloud, is + typically used for filtered data deemed worthy of long-term storage; + although, in some cases, it may be for all data, for example, when + required for regulatory reasons. + + Stateful computing is the default on most systems, VMs, and + containers. Stateless computing is supported on platforms providing + a "serverless computing" service (also known as function-as- + a-service, e.g., using stateless containers) or on systems based on + named function networking. + + In many IoT use cases, a typical network usage pattern is a high- + volume uplink with some form of traffic reduction enabled by + processing over edge computing devices. Alternatives to traffic + reduction include deferred transmission (to off-peak hours or using + physical shipping). Downlink traffic includes application control + and software updates. Downlink-heavy traffic patterns are not + excluded but are more often associated with non-IoT usage (e.g., + video Content Delivery Networks (CDNs)). + +4.2. General Model + + Edge computing is expected to play an important role in deploying new + IoT services integrated with big data and AI enabled by flexible in- + network computing platforms. Although there are many approaches to + edge computing, this section lays out an attempt at a general model + and lists associated logical functions. In practice, this model can + be mapped to different architectures, such as: + + * A single IoT gateway, or a hierarchy of IoT gateways, typically + connected to the cloud (e.g., to extend the centralized cloud- + based management of IoT devices and data to the edge). The IoT + gateway plays a common role in providing access to a heterogeneous + set of IoT devices and sensors, handling IoT data, and delivering + IoT data to its final destination in a cloud network. An IoT + gateway requires interactions with the cloud; however, it can also + operate independently in a disconnected mode. + + * A set of distributed computing nodes, for example, embedded in + switches, routers, edge cloud servers, or mobile devices. Some + IoT devices have sufficient computing capabilities to participate + in such distributed systems owing to advances in hardware + technology. In this model, edge computing nodes can collaborate + to share resources. + + * A hybrid system involving both IoT gateways and supporting + functions in distributed computing nodes. + + In the general model described in Figure 1, the edge computing domain + is interconnected with IoT devices (southbound connectivity), + possibly with a remote (e.g., cloud) network (northbound + connectivity), and with a service operator's system. Edge computing + nodes provide multiple logical functions or components that may not + be present in a given system. They may be implemented in a + centralized or distributed fashion, at the network edge, or through + interworking between the edge network and remote cloud networks. + + +---------------------+ + | Remote Network | +---------------+ + |(e.g., cloud network)| | Service | + +-----------+---------+ | Operator | + | +------+--------+ + | | + +--------------+-------------------+-----------+ + | Edge Computing Domain | + | | + | One or more computing nodes | + | (IoT gateway, end devices, switches, | + | routers, mini/micro-data centers, etc.) | + | | + | OAM Components | + | - Resource Discovery and Authentication | + | - Edge Organization and Federation | + | - Multi-Tenancy and Isolation | + | - ... | + | | + | Functional Components | + | - In-Network Computation | + | - Edge Caching | + | - Communication | + | - Other Services | + | - ... | + | | + | Application Components | + | - IoT Devices Management | + | - Data Management and Analytics | + | - ... | + | | + +------+--------------+-------- - - - -+- - - -+ + | | | | | + | | +-----+--+ + +----+---+ +-----+--+ | |Compute | | + | End | | End | ... |Node/End| + |Device 1| |Device 2| ...| |Device n| | + +--------+ +--------+ +--------+ + + - - - - - - - -+ + + Figure 1: Model of IoT Edge Computing + + In the distributed model described in Figure 2, the edge computing + domain is composed of IoT edge gateways and IoT devices that are also + used as computing nodes. Edge computing domains are connected to a + remote (e.g., cloud) network and their respective service operator's + system. The computing nodes provide logical functions, for example, + as part of distributed machine learning or distributed image + processing applications. The processing capabilities in IoT devices + are limited; they require the support of other nodes. In a + distributed machine learning application, the training process for AI + services can be executed at IoT edge gateways or cloud networks, and + the prediction (inference) service is executed in the IoT devices. + Similarly, in a distributed image processing application, some image + processing functions can be executed at the edge or in the cloud. To + limit the amount of data to be uploaded to central cloud functions, + IoT edge devices may pre-process data. + + +----------------------------------------------+ + | Edge Computing Domain | + | | + | +--------+ +--------+ +--------+ | + | |Compute | |Compute | |Compute | | + | |Node/End| |Node/End| .... |Node/End| | + | |Device 1| |Device 2| .... |Device m| | + | +----+---+ +----+---+ +----+---+ | + | | | | | + | +---+-------------+-----------------+--+ | + | | IoT Edge Gateway | | + | +-----------+-------------------+------+ | + | | | | + +--------------+-------------------+-----------+ + | | + +-----------+---------+ +------+-------+ + | Remote Network | | Service | + |(e.g., cloud network)| | Operator(s) | + +-----------+---------+ +------+-------+ + | | + +--------------+-------------------+-----------+ + | | | | + | +-----------+-------------------+------+ | + | | IoT Edge Gateway | | + | +---+-------------+-----------------+--+ | + | | | | | + | +----+---+ +----+---+ +----+---+ | + | |Compute | |Compute | |Compute | | + | |Node/End| |Node/End| .... |Node/End| | + | |Device 1| |Device 2| .... |Device n| | + | +--------+ +--------+ +--------+ | + | | + | Edge Computing Domain | + +----------------------------------------------+ + + Figure 2: Example of Machine Learning over a Distributed IoT Edge + Computing System + + In the following, we enumerate major edge computing domain + components. Here, they are loosely organized into Operations, + Administration, and Maintenance (OAM); functional; and application + components, with the understanding that the distinction between these + classes may not always be clear, depending on actual system + architectures. Some representative research challenges are + associated with those functions. We used input from coauthors, + participants of T2TRG meetings, and some comprehensive reviews of the + field ([Yousefpour], [Zhang2], and [Khan]). + +4.3. OAM Components + + Edge computing OAM extends beyond the network-related OAM functions + listed in [RFC6291]. In addition to infrastructure (network, + storage, and computing resources), edge computing systems can also + include computing environments (for VMs, software containers, and + functions), IoT devices, data, and code. + + Operation-related functions include performance monitoring for + Service Level Agreement (SLA) measurements, fault management, and + provisioning for links, nodes, compute and storage resources, + platforms, and services. Administration covers network/compute/ + storage resources, platform and service discovery, configuration, and + planning. Discovery during normal operation (e.g., discovery of + compute or storage nodes by endpoints) is typically not included in + OAM; however, in this document, we do not address it separately. + Management covers the monitoring and diagnostics of failures, as well + as means to minimize their occurrence and take corrective actions. + This may include software update management and high service + availability through redundancy and multipath communication. + Centralized (e.g., Software-Defined Networking (SDN)) and + decentralized management systems can be used. Finally, we + arbitrarily chose to address data management as an application + component; however, in some systems, data management may be + considered similar to a network management function. + + We further detail a few relevant OAM components. + +4.3.1. Resource Discovery and Authentication + + Discovery and authentication may target platforms and infrastructure + resources, such as computing, networking, and storage, as well as + other resources, such as IoT devices, sensors, data, code units, + services, applications, and users interacting with the system. In a + broker-based system, an IoT gateway can act as a broker to discover + IoT resources. More decentralized solutions can also be used in + replacement of or in complement to the broker-based solutions; for + example, CoAP enables multicast discovery of an IoT device and CoAP + service discovery enables one to obtain a list of resources made + available by this device [RFC7252]. For device authentication, + current centralized gateway-based systems rely on the installation of + a secret on IoT devices and computing devices (e.g., a device + certificate stored in a hardware security module or a combination of + code and data stored in a trusted execution environment). + + Related challenges include: + + * Discovery, authentication, and trust establishment between IoT + devices, compute nodes, and platforms, with regard to concerns + such as mobility, heterogeneous devices and networks, scale, + multiple trust domains, constrained devices, anonymity, and + traceability. + + * Intermittent connectivity to the Internet, removing the need to + rely on a third-party authority [Echeverria]. + + * Resiliency to failure [Harchol], denial-of-service attacks, and + easier physical access for attackers. + +4.3.2. Edge Organization and Federation + + In a distributed system context, once edge devices have discovered + and authenticated each other, they can be organized or self-organized + into hierarchies or clusters. The organizational structure may range + from centralized to peer-to-peer, or it may be closely tied to other + systems. Such groups can also form federations with other edges or + with remote clouds. + + Related challenges include: + + * Support for scaling and enabling fault tolerance or self-healing + [Jeong]. In addition to using a hierarchical organization to cope + with scaling, another available and possibly complementary + mechanism is multicast [RFC7390] [CORE-GROUPCOMM-BIS]. Other + approaches include relying on blockchains [Ali]. + + * Integration of edge computing with virtualized Radio Access + Networks (Fog RAN) [SFC-FOG-RAN] and 5G access networks. + + * Sharing resources in multi-vendor and multi-operator scenarios to + optimize criteria such as profit [Anglano], resource usage, + latency, and energy consumption. + + * Capacity planning, placement of infrastructure nodes to minimize + delay [Fan], cost, energy, etc. + + * Incentives for participation, for example, in peer-to-peer + federation schemes. + + * Design of federated AI over IoT edge computing systems [Brecko], + for example, for anomaly detection. + +4.3.3. Multi-Tenancy and Isolation + + Some IoT edge computing systems make use of virtualized (compute, + storage, and networking) resources to address the need for secure + multi-tenancy at the edge. This leads to "edge clouds" that share + properties with remote clouds and can reuse some of their ecosystems. + Virtualization function management is largely covered by ETSI NFV and + MEC standards and recommendations. Projects such as [LFEDGE-EVE] + further cover virtualization and its management in distributed edge + computing settings. + + Related challenges include: + + * Adapting cloud management platforms to the edge to account for its + distributed nature, heterogeneity, need for customization, and + limited resources (for example, using Conflict-free Replicated + Data Types (CRDTs) [Jeffery] or intent-based management mechanisms + [Cao]). + + * Minimizing virtual function instantiation time and resource usage. + +4.4. Functional Components + +4.4.1. In-Network Computation + + A core function of IoT edge computing is to enable local computation + on a node at the network edge, typically for application-layer + processing, such as processing input data from sensors, making local + decisions, preprocessing data, and offloading computation on behalf + of a device, service, or user. Related functions include + orchestrating computation (in a centralized or distributed manner) + and managing application life cycles. Support for in-network + computation may vary in terms of capability; for example, computing + nodes can host virtual machines, software containers, software + actors, unikernels running stateful or stateless code, or a rule + engine providing an API to register actions in response to conditions + (such as an IoT device ID, sensor values to check, thresholds, etc.). + + Edge offloading includes offloading to and from an IoT device and to + and from a network node. [Cloudlets] describes an example of + offloading computation from an end device to a network node. In + contrast, oneM2M is an example of a system that allows a cloud-based + IoT platform to transfer resources and tasks to a target edge node + [oneM2M-TR0052]. Once transferred, the edge node can directly + support IoT devices that it serves with the service offloaded by the + cloud (e.g., group management, location management, etc.). + + QoS can be provided in some systems through the combination of + network QoS (e.g., traffic engineering or wireless resource + scheduling) and compute and storage resource allocations. For + example, in some systems, a bandwidth manager service can be exposed + to enable allocation of the bandwidth to or from an edge computing + application instance. + + In-network computation can leverage the underlying services provided + using data generated by IoT devices and access networks. Such + services include IoT device location, radio network information, + bandwidth management, and congestion management (e.g., the congestion + management feature of oneM2M [oneM2M-TR0052]). + + Related challenges include: + + * Computation placement: in a centralized or distributed (e.g., + peer-to-peer) manner, selecting an appropriate compute device. + The selection is based on available resources, location of data + input and data sinks, compute node properties, etc. with varying + goals. These goals include end-to-end latency, privacy, high + availability, energy conservation, or network efficiency (for + example, using load-balancing techniques to avoid congestion). + + * Onboarding code on a platform or computing device and invoking + remote code execution, possibly as part of a distributed + programming model and with respect to similar concerns of latency, + privacy, etc. For example, offloading can be included in a + vehicular scenario [Grewe]. These operations should deal with + heterogeneous compute nodes [Schafer] and may also support end + devices, including IoT devices, as compute nodes [Larrea]. + + * Adapting Quality of Results (QoR) for applications where a perfect + result is not necessary [Li]. + + * Assisted or automatic partitioning of code. For example, for + application programs [COIN-APPCENTRES] or network programs + [REQS-P4COMP]. + + * Supporting computation across trust domains. For example, + verifying computation results. + + * Supporting computation mobility: relocating an instance from one + compute node to another while maintaining a given service level; + session continuity when communicating with end devices that are + mobile, possibly at high speed (e.g., in vehicular scenarios); + defining lightweight execution environments for secure code + mobility, for example, using WebAssembly [Nieke]. + + * Defining, managing, and verifying SLAs for edge computing systems; + pricing is a challenging task. + +4.4.2. Edge Storage and Caching + + Local storage or caching enables local data processing (e.g., + preprocessing or analysis) as well as delayed data transfer to the + cloud or delayed physical shipping. An edge node may offer local + data storage (in which persistence is subject to retention policies), + caching, or both. Generally, "caching" refers to temporary storage + to improve performance without persistence guarantees. An edge- + caching component manages data persistence; for example, it schedules + the removal of data when it is no longer needed. Other related + aspects include the authentication and encryption of data. Edge + storage and caching can take the form of a distributed storage + system. + + Related challenges include: + + * Cache and data placement: using cache positioning and data + placement strategies to minimize data retrieval delay [Liu] and + energy consumption. Caches may be positioned in the access- + network infrastructure or on end devices. + + * Maintaining consistency, freshness, reliability, and privacy of + data stored or cached in systems that are distributed, + constrained, and dynamic (e.g., due to node mobility, energy- + saving regimes, and disruptions) and which can have additional + data governance constraints on data storage location. For + example, [Mortazavi] describes leveraging a hierarchical storage + organization. Freshness-related metrics include the age of + information [Yates] that captures the timeliness of information + received from a sender (e.g., an IoT device). + +4.4.3. Communication + + An edge cloud may provide a northbound data plane or management plane + interface to a remote network, such as a cloud, home, or enterprise + network. This interface does not exist in stand-alone (local-only) + scenarios. To support such an interface when it exists, an edge + computing component needs to expose an API, deal with authentication + and authorization, and support secure communication. + + An edge cloud may provide an API or interface to local or mobile + users, for example, to provide access to services and applications or + to manage data published by local or mobile devices. + + Edge computing nodes communicate with IoT devices over a southbound + interface, typically for data acquisition and IoT device management. + + Communication brokering is a typical function of IoT edge computing + that facilitates communication with IoT devices, enables clients to + register as recipients for data from devices, forwards traffic to or + from IoT devices, enables various data discovery and redistribution + patterns (for example, north-south with clouds and east-west with + other edge devices [EDGE-DATA-DISCOVERY-OVERVIEW]). Another related + aspect is dispatching alerts and notifications to interested + consumers both inside and outside the edge computing domain. + Protocol translation, analytics, and video transcoding can also be + performed when necessary. Communication brokering may be centralized + in some systems, for example, using a hub-and-spoke message broker or + distributed with message buses, possibly in a layered bus approach. + Distributed systems can leverage direct communication between end + devices over device-to-device links. A broker can ensure + communication reliability and traceability and, in some cases, + transaction management. + + Related challenges include: + + * Defining edge computing abstractions, such as PaaS [Yangui], + suitable for users and cloud systems to interact with edge + computing systems and dealing with interoperability issues, such + as data-model heterogeneity. + + * Enabling secure and resilient communication between IoT devices + and a remote cloud, for example, through multipath support. + +4.5. Application Components + + IoT edge computing can host applications, such as those mentioned in + Section 2.4. While describing the components of individual + applications is out of our scope, some of those applications share + similar functions, such as IoT device management and data management, + as described below. + +4.5.1. IoT Device Management + + IoT device management includes managing information regarding IoT + devices, including their sensors and how to communicate with them. + Edge computing addresses the scalability challenges of a large number + of IoT devices by separating the scalability domain into local (e.g., + edge) networks and remote networks. For example, in the context of + the oneM2M standard, a device management functionality (called + "software campaign" in oneM2M) enables the installation, deletion, + activation, and deactivation of software functions and services on a + potentially large number of edge nodes [oneM2M-TR0052]. Using a + dashboard or management software, a service provider issues these + requests through an IoT cloud platform supporting the software + campaign functionality. + + The challenges listed in Section 4.3.1 may be applicable to IoT + device management as well. + +4.5.2. Data Management and Analytics + + Data storage and processing at the edge are major aspects of IoT edge + computing, directly addressing the high-level IoT challenges listed + in Section 3. Data analysis, for example, through AI/ML tasks + performed at the edge, may benefit from specialized hardware support + on the computing nodes. + + Related challenges include: + + * Addressing concerns regarding resource usage, security, and + privacy when sharing, processing, discovering, or managing data: + for example, presenting data in views composed of an aggregation + of related data [Zhang], protecting data communication between + authenticated peers [Basudan], classifying data (e.g., in terms of + privacy, importance, and validity), and compressing and encrypting + data, for example, using homomorphic encryption to directly + process encrypted data [Stanciu]. + + * Other concerns regarding edge data discovery (e.g., streaming + data, metadata, and events) include siloization and lack of + standards in edge environments that can be dynamic (e.g., + vehicular networks) and heterogeneous + [EDGE-DATA-DISCOVERY-OVERVIEW]. + + * Data-driven programming models [Renart], for example, those that + are event based, including handling naming and data abstractions. + + * Data integration in an environment without data standardization or + where different sources use different ontologies + [Farnbauer-Schmidt]. + + * Addressing concerns such as limited resources, privacy, and + dynamic and heterogeneous environments to deploy machine learning + at the edge: for example, making machine learning more lightweight + and distributed (e.g., enabling distributed inference at the + edge), supporting shorter training times and simplified models, + and supporting models that can be compressed for efficient + communication [Murshed]. + + * Although edge computing can support IoT services independently of + cloud computing, it can also be connected to cloud computing. + Thus, the relationship between IoT edge computing and cloud + computing, with regard to data management, is another potential + challenge [ISO_TR]. + +4.6. Simulation and Emulation Environments + + IoT edge computing introduces new challenges to the simulation and + emulation tools used by researchers and developers. A varied set of + applications, networks, and computing technologies can coexist in a + distributed system, making modeling difficult. Scale, mobility, and + resource management are additional challenges [SimulatingFog]. + + Tools include simulators, where simplified application logic runs on + top of a fog network model, and emulators, where actual applications + can be deployed, typically in software containers, over a cloud + infrastructure (e.g., Docker and Kubernetes) running over a network + emulating network edge conditions, such as variable delays, + throughput, and mobility events. To gain in scale, emulated and + simulated systems can be used together in hybrid federation-based + approaches [PseudoDynamicTesting]; whereas to gain in realism, + physical devices can be interconnected with emulated systems. + Examples of related work and platforms include the publicly + accessible MEC sandbox work recently initiated in ETSI [ETSI_Sandbox] + and open-source simulators and emulators ([AdvantEDGE] emulator and + tools cited in [SimulatingFog]). EdgeNet [Senel] is a globally + distributed edge cloud for Internet researchers, which uses nodes + contributed by institutions and which is based on Docker for + containerization and Kubernetes for deployment and node management. + + Digital twins are virtual instances of a physical system (twin) that + are continually updated with the latter's performance, maintenance, + and health status data throughout the life cycle of the physical + system [Madni]. In contrast to an emulation or simulated + environment, digital twins, once generated, are maintained in sync by + their physical twin, which can be, among many other instances, an IoT + device, edge device, or an edge network. The benefits of digital + twins go beyond those of emulation and include accelerated business + processes, enhanced productivity, and faster innovation with reduced + costs [NETWORK-DIGITAL-TWIN-ARCH]. + +5. Security Considerations + + Privacy and security are drivers of the adoption of edge computing + for the IoT (Section 3.4). As discussed in Section 4.3.1, + authentication and trust (among computing nodes, management nodes, + and end devices) can be challenging as scale, mobility, and + heterogeneity increase. The sometimes disconnected nature of edge + resources can avoid reliance on third-party authorities. Distributed + edge computing is exposed to reliability and denial-of-service + attacks. A personal or proprietary IoT data leakage is also a major + threat, particularly because of the distributed nature of the systems + (Section 4.5.2). Furthermore, blockchain-based distributed IoT edge + computing must be designed for privacy, since public blockchain + addressing does not guarantee absolute anonymity [Ali]. + + However, edge computing also offers solutions in the security space: + maintaining privacy by computing sensitive data closer to data + generators is a major use case for IoT edge computing. An edge cloud + can be used to perform actions based on sensitive data or to + anonymize or aggregate data prior to transmission to a remote cloud + server. Edge computing communication brokering functions can also be + used to secure communication between edge and cloud networks. + +6. Conclusion + + IoT edge computing plays an essential role, complementary to the + cloud, in enabling IoT systems in certain situations. In this + document, we presented use cases and listed the core challenges faced + by the IoT that drive the need for IoT edge computing. Therefore, + the first part of this document may help focus future research + efforts on the aspects of IoT edge computing where it is most useful. + The second part of this document presents a general system model and + structured overview of the associated research challenges and related + work. The structure, based on the system model, is not meant to be + restrictive and exists for the purpose of having a link between + individual research areas and where they are applicable in an IoT + edge computing system. + +7. IANA Considerations + + This document has no IANA actions. + +8. Informative References + + [AdvantEDGE] + "AdvantEDGE, Mobile Edge Emulation Platform", commit + 8f6edbe, May 2023, + <https://github.com/InterDigitalInc/AdvantEDGE>. + + [Ali] Ali, M., Vecchio, M., and F. 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Bernardos, Milan Milenkovic, Dale Seed, + JaeSeung Song, Roberto Morabito, Carsten Bormann, and Ari Keränen for + their valuable comments and suggestions on this document. + +Authors' Addresses + + Jungha Hong + ETRI + 218 Gajeong-ro, Yuseung-Gu + Daejeon + 34129 + Republic of Korea + Email: jhong@etri.re.kr + + + Yong-Geun Hong + Daejeon University + 62 Daehak-ro, Dong-gu + Daejeon + 300716 + Republic of Korea + Email: yonggeun.hong@gmail.com + + + Xavier de Foy + InterDigital Communications, LLC + 1000 Sherbrooke West + Montreal H3A 3G4 + Canada + Email: xavier.defoy@interdigital.com + + + Matthias Kovatsch + Huawei Technologies Duesseldorf GmbH + Riesstr. 25 C // 3.OG + 80992 Munich + Germany + Email: ietf@kovatsch.net + + + Eve Schooler + University of Oxford + Parks Road + Oxford + OX1 3PJ + United Kingdom + Email: eve.schooler@gmail.com + + + Dirk Kutscher + Hong Kong University of Science and Technology (Guangzhou) + No.1 Du Xue Rd + Guangzhou + China + Email: ietf@dkutscher.net |