عنوان مقاله:
تحقیق درباره پروتکل های استاندارد سازی برای اینترنت اشیا
Survey of Standardized Protocols for the Internet of Things
سال انتشار: 2017
رشته: مهندسی کامپیوتر - فناوری اطلاعات
گرایش: اینترنت و شبکه های گسترده - رایانش ابری - شبکه های کامپیوتری
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مشاهده سایر مقالات جدید:
Service discovery protocols
In the Internet, the most extended discovery architecture is based on Domain Name Server (DNS), but this is not a suitable option for the Internet of Things, because IoT devices join or leave networks more often. So, two extensions have been developed, called DNS-SD (Service Discovery) and mDNS (multicast DNS). The challenges that they must face, related to Internet of Things, are scalability, since there is an estimation that, in 2020, there will be almost 50 billion devices connected, dynamism, for wearable smart devices, that can easily switch connections, devices in sleep mode, leading to a limitation for queries addressed to endpoints and payload size, as less data is transferred. Local directories should be extended to give information on other domains where resources are available. Also, directories should support multicast, for queries such as “turn off all lights in the room”, where all the endpoints are treated as one. The access to directories should be done in an already known manner and a common description should be used for services and attributes [8]. A. mDNS and DNS-SD mDNS (RFC6762) [9] is a service that can perform the task of a DNS server. In a local network, every client has a cache where it keeps the pairing between names and addresses. Every time a device wants to get name information, it sends a multicast query and waits for a response. The targeted machine sends a multicast response in the network and all the devices that receive it save the pairing in their local cache. It has the advantage that there is no need for a dedicated server and it also adapts easily to changes in the network [2]. DNS-SD (RFC6763) [10] is a solution proposed by IETF ZeroConf WG that re-uses and extends the capabilities of the DNS. It uses the same types of queries (AAA, PTR) and enables locating and publishing services in a network [9]. For instance, clients that want to get printer services in the network use DNS-SD. They have firstly to get the names of the devices that provide the required service, then they use mDNS to get the address. It is essential to first find the hostname, because the IP addressed may change. The main drawback of these two protocols is the need to keep cache entries in devices with low memory. Bonjour and Avahi are two well-known implementations based on DNS.
infrastructure protocols
At the physical and media access layer, the standardized protocols are designed for different needs. Part of them are specialized for local networks, which require low distances and low power. They are addressed especially to smart buildings or homes. Others can offer a high range, being able to supply the needs of smart cities or industrial environments. A. IEEE 802.15.4 The IEEE 802.15.4 [13] standard was especially designed for low-power, short-range and low-bit rate embedded devices. The IEEE 802.15 working groups aims to keep the hardware costs low, to spread the protocol compatibility among sensors. The protocol describes the physical layer and the media access control sublayer [14]. The physical layer is responsible with activation and deactivation of the radio transceiver, receiving and transmitting data and selecting a channel and listening on it. At this layer, there are two supported frequencies. The low-band (868/915 MHz), that uses binary phase shift key modulation and the high band (2.4GHz) that uses offset quadrature phase shift keying modulation. There are 27 available channels, 11 in low band and 16 in high band. The raw bit rates are 20-40kbps in low band and 250kbps in high band. By using these modulations and spreading techniques, the transmissions are robust and noise resistant [15]. At the MAC layer, CSMA/CA is enabled, together with optional time slot structure and security. Every time a device wants to send data, the medium is checked by the PHY layer. If it is occupied, the transmission is postponed for a certain period of time [14]. The transmission units are called Physical Protocol Data Unit for Layer 1 and MAC Protocol Data Unit. The PPDU header has two fields, then the payload is added. The SYNC field is used for clock synchronization and the PHY field contains the length of the payload. In the MAC frame, the first two bytes indicate the type of the frame [14]. There are four types of frames defined in the standard. The first ones, beacon frames are used by coordinators to describe the way the channels can be accessed. Then, there are data frames and acknowledgements sent as responses for control and data packets. The last, control frames are used for network management, such as associations or disassociations [15]. The next flag, the sequence number, is used by acknowledgements and refers to the received frame. Then, there are addressing pieces of information, related to source, destination addresses and security. The last two bytes represent the checksum, used for data integrity.
چکیده
اینترنت اشیا یک فناوری در حال رشد است که در حوزه های متعددی از جمله خانه های هوشمند تا سلامت و صنایع در حال توسعه است. از دیدگاه فناورانه، اینترنت اشیا توسعه پروتکل ها و سناریوهای جدید را امکان پذیر می سازد چرا که مجموعه پروتکل های استاندارد شبکه نمی تواند با تعداد رو به رشد دستگاه های متصل و داده های ارسالی مواجه شود. هدف این مقاله ارائه پروتکل های استاندارد متعدد در سطوح مختلف شبکه است که به طور ویژه برای دستگاه های تعبیه شده با حافظه کم، توان پردازشی پایین و نرخ داده پایین توسعه داده شده است. ما همچنین سناریو خانه هوشمند را پیشنهاد می دهیم که تنها از پروتکل های استاندارد شده اینترنت اشیا استفاده می کند.
