Multimedia Internet of Things: A Comprehensive Survey <s> VI. ROUTING PROTOCOLS FOR MULTIMEDIA IN IoT <s> This paper provides an overview of the Internet of Things (IoT) with emphasis on enabling technologies, protocols, and application issues. The IoT is enabled by the latest developments in RFID, smart sensors, communication technologies, and Internet protocols. The basic premise is to have smart sensors collaborate directly without human involvement to deliver a new class of applications. The current revolution in Internet, mobile, and machine-to-machine (M2M) technologies can be seen as the first phase of the IoT. In the coming years, the IoT is expected to bridge diverse technologies to enable new applications by connecting physical objects together in support of intelligent decision making. This paper starts by providing a horizontal overview of the IoT. Then, we give an overview of some technical details that pertain to the IoT enabling technologies, protocols, and applications. Compared to other survey papers in the field, our objective is to provide a more thorough summary of the most relevant protocols and application issues to enable researchers and application developers to get up to speed quickly on how the different protocols fit together to deliver desired functionalities without having to go through RFCs and the standards specifications. We also provide an overview of some of the key IoT challenges presented in the recent literature and provide a summary of related research work. Moreover, we explore the relation between the IoT and other emerging technologies including big data analytics and cloud and fog computing. We also present the need for better horizontal integration among IoT services. Finally, we present detailed service use-cases to illustrate how the different protocols presented in the paper fit together to deliver desired IoT services. <s> BIB001 </s> Multimedia Internet of Things: A Comprehensive Survey <s> VI. ROUTING PROTOCOLS FOR MULTIMEDIA IN IoT <s> RPL is the IPv6 routing protocol for low-power and lossy networks, standardized by IETF in 2012 as RFC6550. Specifically, RPL is designed to be a simple and inter-operable networking protocol for resource-constrained devices in industrial, home, and urban environments, intended to support the vision of the Internet of Things with thousands of devices interconnected through multihop mesh networks. More than four-years have passed since the standardization of RPL, and we believe that it is time to examine and understand its current state. In this paper, we review the history of research efforts in RPL; what aspects have been (and have not been) investigated and evaluated, how they have been studied, what was (and was not) implemented, and what remains for future investigation. We reviewed over 97 RPL-related academic research papers published by major academic publishers and present a topic-oriented survey for these research efforts. Our survey shows that only 40.2% of the papers evaluate RPL through experiments using implementations on real embedded devices, ContikiOS and TinyOS are the two most popular implementations (92.3%), and TelosB was the most frequently used hardware platform (69%) on testbeds that have average and median size of 49.4 and 30.5 nodes, respectively. Furthermore, unfortunately, despite it being approximately four years since its initial standardization, we are yet to see wide adoption of RPL as part of real-world systems and applications. We present our observations on the reasons behind this and suggest directions on which RPL should evolve. <s> BIB002 </s> Multimedia Internet of Things: A Comprehensive Survey <s> VI. ROUTING PROTOCOLS FOR MULTIMEDIA IN IoT <s> Abstract By combining energy efficient micro-controllers, low-power radio transceivers, and sensors as well as actuators in so called smart objects, we are able to connect the digital cyber world with the physical world as in cyber physical systems. In the vision of the Internet of Things, these smart objects should be seamlessly integrated into the traditional Internet. Typically, smart objects are heavily constrained in terms of computation, memory and energy resources. Furthermore, the commonly used wireless links among smart objects or towards the Internet are typically slow and subject to high packet loss. Such characteristics pose challenges, on one hand in terms of software running on smart objects, and on the other hand in terms of network protocols which smart objects use to communicate. New operating systems, application programming interfaces, frameworks, and middleware have to be designed with consideration of such constraints. In consequence, novel validation methods and experimental tools are needed to study smart object networks in vivo, new software platforms are needed to efficiently operate smart objects, and innovative networking paradigms and protocols are required to interconnect smart objects. <s> BIB003
Multimedia data exhibits stringent requirements according to diverse characteristics in terms of volume, variety, velocity, and value, especially for efficient bandwidth utilization and reliability. The deviation from Moore's law, multimedia devices are now becoming smaller in size, with a decrease in cost and memory to support mobility BIB003 . The current standards and protocols, as shown in Fig. 15 , consume a significant amount of bandwidth and energy to ensure reliability. These communication protocols are not optimized for low power multimedia communication. The current standardization activities are not focussed on multimedia communication over IoT. ITU defines traffic routing of mobile services in ITU-T Recommendation E.170  as: ''establishing a successful connection between two exchanges or the selection of path between source and sink node in the network.'' An intelligent routing protocol is in need to select an efficient route for multimedia content transmission over bandwidth and memoryconstrained wireless IoT network. The scarcity of IPv4 urges the recommendation of IPv6 for smart IoT objects. 6LoWPAN is an IP based technology for Low-power and Lossy Networks (LLNs) to bridge the gap between low-power devices and the IP world  . 6LoWPAN compresses IPv6 headers and fragmentation of large packets to make IPv6 suitable for resource-constrained devices  . International Engineering Task Force (IETF) proposed an IPv6 Routing Protocol for LLNs (RPL)  ,  . RPL is now widely adopted as a promising standard with increasing popularity because it offers flexibility and interoperability by adopting different network topologies. RPL exploits key network metrics such as throughput, node energy, latency, hop count, and link reliability. RPL supports Point-to-Point (P2P), Point-to-MultiPoint (P2MP) and MultiPoint-to-Point (MP2P) communication paradigm. Kimet al. BIB002 provided a detailed picture of the research that has investigated RPL. The authors presented the distribution of research carried out on RPL in the context of the geographical region, operating systems, hardware platforms, and network metrics. A plethora of work and survey studies of the IoT communication protocols mentioned in Fig. 16 are present in the literature BIB001 , BIB003 ,  ,  . In this section, we have extensively studied routing of multimedia content, i.e., audio, image, and video in IoT to meet the stringent requirements of multimedia communication in IoT while maintaining QoS and QoE with efficient bandwidth and energy utilization. Fig. 16 shows the classification of the existing works on multimedia routing in IoT. Cross-layer communication protocol for multimedia data routing in IoT has been discussed. Routing protocols for multimedia data streaming in a multicast or unicast manner to provide the required QoS has been extensively studied. Table 8 tabulates the performance summary and comparison of studies on multimedia data routing in IoT.