You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations 
Chapter Title:  2) 6LoWPAN (Layer 2.5) 
1. Abstract of Cited Paper (BIB001):  Wireless sensor networks are expected to be deployed widely in various areas in coming years. The sensor device is small and has low computation power and memory thus perceived as not suitable to be loaded with the high resource IP capabilities. Due to this, the wireless sensor network remains isolated from the Internet. The emergence of IPv6 over low power wireless personal area network (6LoWPAN) has proved that IP communication is borderless and can be used for any devices. It provides a simple alternative to other wireless sensor networks and interoperable with IP-legacy systems and tools. However, the use of short addresses within the 6LoWPAN network is not visible to the outside world and hence a proper gateway is required. In this paper, we provide the architecture of the 6LoWPAN gateway which connects the wireless sensor world to the Internet. Our contribution is to provide direct accessibility to wireless sensor network using short address to full IPv6 address translation at the gateway. Our main focus is the flow of packets to and from the gateway including a simple address translation mechanism. The implementation and the use cases of the gateway are also highlighted. 
2. Abstract of Cited Paper (BIB002):  Smart object technology, sometimes called the Internet of Things, is having a profound impact on our day-to-day lives. Interconnecting Smart Objects with IP is the first book that takes a holistic approach to the revolutionary area of IP-based smart objects. Smart objects are the intersection of networked embedded systems, wireless sensor networks, ubiquitous and pervasive computing, mobile telephony and telemetry, and mobile computer networking. This book consists of three parts, Part I focuses on the architecture of smart objects networking, Part II covers the hardware, software, and protocols for smart objects, and Part III provides case studies on how and where smart objects are being used today and in the future. The book covers the fundamentals of IP communication for smart objects, IPv6, and web services, as well as several newly specified low-power IP standards such as the IETF 6LoWPAN adaptation layer and the RPL routing protocol. This book contains essential information not only for the technical reader but also for policy makers and decision makers in the area of smart objects both for private IP networks and the Internet. ::: ::: ::: ::: Shows in detail how connecting smart objects impacts our lives with practical implementation examples and case studies ::: Provides an in depth understanding of the technological and architectural aspects underlying smart objects technology ::: Offers an in-depth examination of relevant IP protocols to build large scale smart object networks in support of a myriad of new services ::: ::: Table of Contents ::: ::: Part I: The Architecture Chapter 1: What are Smart objects? Chapter 2: The IP protocol architecture Chapter 3: Why IP for smart objects? Chapter 4: IPv6 for Smart Object Networks and The Internet of Things Chapter 5: Routing Chapter 6: Transport Protocols Chapter 7: Service Discovery Chapter 8: Security for Smart Objects Chapter 9: Web services For Smart Objects Chapter 10: Connectivity models for smart object networks ::: Part II: The Technology Chapter 11: What is a Smart Object? Chapter 12: Low power link layer for smart objects networks Chapter 13: uIP A Lightweight IP Stack Chapter 14: Standardization Chapter 15: IPv6 for Smart Object Networks - A Technology Refresher Chapter 16: The 6LoWPAN Adaptation Layer Chapter 17: RPL Routing in Smart Object Networks Chapter 18: The IPSO Alliance Chapter 19: Non IP Technology ::: ::: Part III: The Applications Chapter 20: Smart Grid Chapter 21: Industrial Automation Chapter 22: Smart Cities and Urban Networks Chapter 23: Home Automation Chapter 24: Building Automation Chapter 25: Structural Health Monitoring Chapter 26: Container Tracking 
3. Abstract of Cited Paper (BIB003):  Wireless Sensor Networks (WSNs) are playing more and more a key role in several application scenarios such as healthcare, agriculture, environment monitoring, and smart metering. Furthermore, WSNs are characterized by high heterogeneity because there are many different proprietary and non-proprietary solutions. This wide range of technologies has delayed new deployments and integration with existing sensor networks. The current trend, however, is to move away from proprietary and closed standards, to embrace IP-based sensor networks using the emerging standard 6LoWPAN/IPv6. This allows native connectivity between WSN and Internet, enabling smart objects to participate to the Internet of Things (IoT). Building an all-IP infrastructure from scratch, however, would be difficult because many different sensors and actuators technologies (both wired and wireless) have already been deployed over the years. After a review of the state of the art, this paper sketches a framework able to harmonize legacy and new installations, allowing migrating to an all-IP environment at a later stage. The Building Automation use case has been chosen to discuss potential benefits of the proposed framework. 
4. Abstract of Cited Paper (BIB004):  With RPL - the “IPv6 Routing Protocol for Low-power Lossy Networks” - emerging as a Proposed Standard “Request For Comment” (RFC) in the Internet Engineering Task Force (IETF) after a ∼2-year development cycle, this paper presents a critical evaluation of the resulting protocol and its applicability and limits. The paper presents a selection of observations of the protocol characteristics, exposes experiences acquired when producing a prototype implementation of RPL, and presents results obtained from testing this protocol - both in a network simulator, and in real-world experiments on a wireless sensor network testbed. The paper aims at providing a better understanding of possible weaknesses and limits of RPL, notably the possible directions that further protocol developments should explore, in order to address these. 
5. Abstract of Cited Paper (BIB005):  Embedded devices connected to the Internet will start an increasing growth of the Internet in near future. Wireless Sensor Networks (WSN) will play a major role in that growth. In the past several solutions were proposed to make sensor network sip capable. Today there are IPv6-Stacks available including web servers running on sensor nodes. However, a gateway is always needed to convert the routing protocols and MAC-Layer Protocols including compression of IP packets to run on these devices. The overhead using IPv6 on the nodes is very high in respect of code size and message overhead. Therefore, in our approach we design and implement a system based on simple protocols target for sensor network nodes and a flexible gateway working in a hybrid fashion for our sensor network test bed. We successfully integrated this non-IP WSN in the Internet and our test bed is productive available from any computer connected to the Internet for reference. In this paper we present the architecture of our solution and present the implementation details of a standard WSN application that can be used for evaluation. 
6. Abstract of Cited Paper (BIB006):  The wireless sensor networks (WSN) concept was appeared in the middle of 90's and have been a subject under intensive research in the past few years. Several factors have contributed to this; the most important is the vast potential for application of WSNs in almost every aspect of day-to-day life is the predominant one. These networks have been developed using proprietary approaches instead of standard solutions. More recently, the importance of standards motivated the use of IETF standards in WSNs, making the Internet integration easier. The dissemination of small mobile devices with Internet connectivity can be the drive to the WSN growth, because user-friendly applications maybe used to retrieve and collect sensed data. This paper proposes a solution based on REST Web services to support the interaction between a mobile application and the IPv6 compliant WSN. Dual stack mechanisms are supported in order to accept requests from both IPv4 and IPv6 mobile devices. A WSN laboratory testbed was deployed to perform the validation and demonstration of the proposed solution. 
7. Abstract of Cited Paper (BIB007):  The Internet is smoothly migrating from an Internet of people towards an Internet of Things (IoT). By 2020, it is expected to have 50 billion things connected to the Internet. However, such a migration induces a strong level of complexity when handling interoperability between the heterogeneous Internet things, e.g., RFIDs (Radio Frequency Identification), mobile handheld devices, and wireless sensors. In this context, a couple of standards have been already set, e.g., IPv6, 6LoWPAN (IPv6 over Low power Wireless Personal Area Networks), and M2M (Machine to Machine communications). In this paper, we focus on the integration of wireless sensor networks into IoT, and shed further light on the subtleties of such integration. We present a real-world test bed deployment where wireless sensors are used to control electrical appliances in a smart building. Encountered problems are highlighted and suitable solutions are presented.

Literature Review:
Due to the restrictions imposed by the LLN devices and their underlying technologies, initially the Internet Protocol version 6 (IPv6) BIB001 was considered to be too resource intensive for such constrained devices BIB002 . Alternative proprietary solutions tended to implement complex application gateways to translate the non-IP format, understood by such networks, to the IP world BIB006 . However, various issues limited the adoption of gateways technology and led to a re-evaluation of the suitability of IPv6 for the LLNs BIB007 . In this new vision, the LLNs are no longer seen as isolated systems, i.e. proprietary solutions, rather they are seen as a key enabling technology for the ever-growing Internet of Things (IoT) paradigm where multitudes of identifiable smart objects, including smartphones, computers, laptops, actuators and sensors, are integrated into the Internet BIB004 BIB008 . However, the eventual LLN transition to the IPv6 world did not automatically resolve the old concerns about the demand on device resources and underlying communication technologies. For instance, while the key IEEE 802.15.4 medium access standard (layer 2) can only support a maximum transmission unit (MTU) of 127 bytes, the IPv6 protocol, which operates at layer 3, requires a minimum datagram size of 1280 bytes, approximately ten times greater BIB005 . In order to address such obstacles, the IETF commissioned the "IPv6 over Low Power Wireless Personal Area Network (LoWPAN) working group" to generate protocols that ensure smooth integration between LLNs and other networks running IPv6 BIB003 . These efforts culminated in specifying a new standard that allows for the IPv6 packets to be carried within the IEEE 802.15.4 MAC layer named, 6LoWPAN  . This has been enabled by identifying an adaptation layer, sometimes referred to as layer 2.5, between the IEEE 802.15.4 MAC layer (layer 2) and the IPv6 network layer (layer 3) as illustrated in Figure 2a . In particular, the 6LoWPAN adaptation layer defines the mechanisms of IPv6 header compression, IPv6 packet fragmentations and reassembly so that the IP datagram can be carried smoothly within the IEEE 802.15.4 frames.