Traditionally, Internet of Things (IoT) communication technologies have been designed to offer low bit rates (from ∼10 2 to ∼10 6 bit/s). However, recent IoT-intended technologies like 5G Reduced Capability (RedCap) support significantly greater bit rates (up to ∼10 8 bit/s), enabling emerging IoT use cases that demand greater capacity. Thus, the spectrum of IoT scenarios and corresponding requirements is expanding, a trend which is expected to continue with 6G networks. In this context, support, configuration and performance of a crucial upper-layer protocol like TCP become challenging. In this paper, based on our IETF standardization work, we describe how TCP can run suitably on a wide variety of IoT environments (from highly constrained scenarios to resource-rich ones). Furthermore, we present and study the novel TCP option called TCP Acknowledgment Rate Request (TARR), designed for further TCP adaptability, which is particularly useful for current and future IoT networks.

In traditional IoT applications, energy saving is crucial, whereas the demand for high bandwidth is not frequent. Nonetheless, a new generation of IoT applications show a wider and varying range of requirements, where bandwidth or delay become key performance indicators to consider, which can be satisfied by technologies like Wi-Fi. However, Wi-Fi does not provide a long link range, and it exhibits a high energy consumption. To solve these issues, we propose a Wi-Fi mesh architecture where devices are equipped with a secondary, Wake-up Radio (WuR) interface, based on the new IEEE 802.11ba amendment. A WuR allows the main radio to remain in a power-saving state for long periods. Simulation results demonstrate that this architecture drastically reduces energy consumption, while keeping delay figures similar to those of traditional, single-interface approaches. To our best knowledge, this work pioneers the exploration of WuR's practicality in optimizing energy consumption in Wi-Fi-based mesh networks.

The static context header compression and fragmentation (SCHC) framework has been recently designed by the Internet engineering task force (IETF). SCHC provides adaptation layer functionality intended to efficiently support IPv6-based and other applications over low power wide area network (LPWAN) technologies. As of the writing, technology-specific profiles are being standardized in order to describe how SCHC can be tailored when used over a given underlying technology. In this article, we provide the first performance evaluation of SCHC over Sigfox, a flagship LPWAN technology. We focus on the main SCHC over Sigfox fragmentation mode, called ACK-on-Error, which offers low overhead, reliability, and reassembly functionalities. We provide a theoretical analysis and an experimental evaluation in real environments that correspond to two geographical zones with different Sigfox radio settings: 1) Barcelona (Spain) and 2) Santiago (Chile). The study focuses on modeling and evaluating packet transfer times, and the required number of uplink and downlink messages. The results show that a small change in packet sizes may significantly affect the transfer times, especially when no duty-cycle restrictions are enforced. Also, we observe that, under certain conditions, an increase in the fragment loss rate (FLR) may decrease the packet transfer time, and that the number of uplink and downlink messages is not proportional to such increase due to the fact that downlink messages are device-driven. The results provide useful insights for researchers, developers, implementers, and providers, with applicability to the application design, network planning, and resource management of Internet of Things (IoT) solutions.

The Internet engineering task force (IETF) has standardized a new framework for IPv6 support over low-power wide-area networks (LPWANs), called static context header compression and fragmentation (SCHC). SCHC includes acknowledgment (ACK)-based mechanisms for reliable fragmented packet transmission. For the latter, SCHC defines a receiver-feedback technique (RFT), called compressed bitmap (CB), by which a receiver reports to the sender whether the fragments carrying a packet have been received or not. Such information is carried as ACK payload. Considering the extraordinary frame size and message rate constraints of LPWANs, ACK payload size becomes crucial. In this article, we compare the performance of CB with that of several alternative RFTs, namely, list of lost fragments (LLF), List of Deltas (LoD), and uncompressed bitmap (UB), where the latter is used as a benchmark. We evaluate the considered RFTs in terms of ACK size, number of Layer 2 (L2) frames needed to carry an ACK, and ACK Time on Air. Our analysis shows that the use of RFTs different from CB offers significant performance improvement in many scenarios. Furthermore, we provide guidance on which RFT should be used for different packet sizes, error rates, and error patterns.

RPL is the de-facto IPv6-based routing protocol for the Internet of Things (IoT), where networks are mainly formed by sensors and other low capacity devices. However, RPL lacks scalability and is inefficient in any-to-any communications. In this article, we present IoTorii, a hierarchical protocol that creates routes based on a probe frame, instead of the computation of a distance vector, as in RPL. We implemented a proof-of-concept of IoTorii and compared it with RPL, proving lower number of table entries, decreased exchanged control messages and faster convergence time, with similar path hop count, which is particularly promising in the IoT field.

Low-power wide-area networks (LPWANs) are experiencing high momentum as an inexpensive solution for enabling the Internet-of-Things (IoT) applications. Recent Internet connectivity support developments are expected to further fuel the adoption of LPWAN. However, the latter present challenges to the Internet protocols. Remarkably, many LPWAN scenarios exhibit a multimodal round-trip time (RTT) distribution, which deviates from the common Internet RTT characteristics. This leads to a significant mismatch between retransmission timeout (RTO), computed by the standard transmission control protocol (TCP) or alternative experimental RTO algorithms, and RTT. In this article, we present the Multimodal RTO algorithm, which is able to self-adapt to the current RTT mode and produce suitable RTO values. The evaluation results show that the Multimodal RTO reduces the RTO versus RTT misalignment of the TCP RTO algorithm by an average factor of up to 5, and reduces latency in the presence of losses by up to 2 orders of magnitude, while operating safely. The Multimodal RTO is currently being considered by the IETF as a candidate mechanism for standardization.

The Constrained Application Protocol (CoAP) is a new Web protocol for the Internet of Things that allows to connect IoT devices directly to services hosted in the cloud. CoAP is based on UDP to better fit the requirements of constrained environments with resource-constrained nodes and low-power communication links. Being an Internet protocol, CoAP must still adhere to congestion control, primarily to keep the backbone network stable. Thus, the base specification uses conservative parameter values for the number of open requests, the retransmission timers, and the overall message rate. More powerful CoAP nodes, however, can use metrics to optimize these parameters to achieve a better quality of service. For this, the IETF CoRE working group is designing an advanced congestion control mechanism for CoAP called CoCoA. This paper presents first evaluation results for a mechanism that improves the communication between cloud services and resource-constrained IoT devices. We implement CoCoA for the Californium (Cf) CoAP framework and evaluate its performance on a wireless sensor network testbed that runs IPv6. Our results show that CoCoA can better utilize the available network capacity and can increase throughput by 19-112%.

The development of IPv6 stacks for wireless constrained devices that have limited hardware resources has paved the way for many new areas of applications and protocols. The Constrained Application Protocol (CoAP) has been designed by the IETF to enable the manipulation of resources for constrained devices that are capable of connecting to the Internet. Due to the limited radio channel capacities and hardware resources, congestion is a common phenomenon in networks of constrained devices. CoAP implements a basic congestion control mechanism for the transmission of reliable messages. Alternative CoAP congestion control approaches are a recent topic of interest in the IETF CoRE Working Group. New Internet-Drafts discuss the limitations of the default congestion control mechanisms and propose alternative ones, yet, there have been no studies in the literature that compare the original approach to the alternative ones. In this paper, we target this crucial study and perform evaluations that show how the default and alternative congestion control mechanisms compare to each other. We use the Cooja simulation environment, which is part of the Contiki development toolset, to simulate CoAP within a complete protocol stack that uses IETF protocols for constrained networks. Through simulations of different network topologies and varying traffic loads, we demonstrate how the advanced mechanisms proposed in the drafts perform relative to the basic congestion control mechanism.

The IETF ROLL WG is currently in the final steps of the specification of RPL, a new routing protocol for low power and lossy networks (e.g. wireless sensor networks). RPL may use layer two- and layer three-based mechanisms for neighbor reachability maintenance. Since layer two mechanisms may not always be available, RPL relies by default on the 6LoWPAN Neighbor Discovery, a version of the IPv6 Neighbor Discovery which is optimized for LLNs. This paper provides an analysis of the impact of various RPL and 6LoWPAN Neighbor Discovery parameter settings on the link availability and end-to-end path availability, and the related message overhead. Results show that careful tuning of the relevant parameters is critical for obtaining good network performance.

Wireless sensor networks (WSNs) have gained momentum as a technology for monitoring and control applications in a plethora of scenarios. Some examples include home automation, industrial control and environmental monitoring. In fact, these networks may enable the futuristic paradigm called ambient intelligence. Despite the challenges that present these networks, a variety of solutions (many of which are proprietary) have emerged. In parallel, the Internet Engineering Task Force (IETF) is devoting a lot of effort to the development of standard networking solutions for WSNs based on the Internet Protocol (IP). This work will allow straightforward interoperability between WSNs and the Internet and will also constitute a significant step towards the ‘Internet of Things’.

Web download performance is dramatically degraded in UMTS, resulting in perceived throughputs of around 25% of the expected bandwidth even in favorable conditions. We analyze the main factors that lead to this low performance. We then propose end-to-end mechanisms and proxy-based approaches to improve overall performance and maximize link utilization in UMTS. We evaluate these solutions in a real UMTS scenario. The results show an improvement of up to 50% in terms of download time and a saving of around 10% of the exchanged information in UMTS networks with channel switching mechanisms.

Abstract 2.5 Generation (2.5G) and Third Generation (3G) cellular wireless networks allow mobile Internet access with bearers specifically designed for data communications. However, Internet protocols under‐utilize wireless wide area network (WWAN) link resources, mainly due to large round trip times (RTTs) and request‐‐reply protocol patterns. Web browsing is a popular service that suffers significant performance degradation over 2.5G and 3G. In this paper, we review and compare the two main approaches for improving web browsing performance over wireless links: (i) using adequate end‐to‐end parameters and mechanisms and (ii) interposing a performance enhancing proxy (PEP) between the wireless and wired parts. We conclude that PEPs are currently the only feasible way for significantly optimizing web browsing behavior over 2.5G and 3G. In addition, we evaluate the two main current commercial PEPs over live general packet radio service (GPRS) and universal mobile telecommunications system (UMTS) networks. The results show that PEPs can lead to near‐ideal web browsing performance in certain scenarios. Copyright © 2006 John Wiley & Sons, Ltd.

Abstract Session setup delay in Packet Switched Streaming (PSS) services over Third Generation (3G) wireless networks is impacted by Real‐Time Streaming Protocol (RTSP) and Session Description Protocol (SDP) signalling exchange and negotiation, as well as media buffering at the terminal before playback. The paper discusses PSS session setup delay over 3G, and proposes two RTSP and SDP protocol extensions to reduce this delay, namely: RTSP Early Setup and usage of SDP Templates. The rationale behind this proposal is presented, particularly when a Secondary Packed Data Protocol Context (PDP‐Context) is used to support media delivery with Quality of Service (QoS) support. The RTSP Early Setup mechanism facilitates pipelining of RTSP messages and early trigger of Secondary PDP‐Context setup. The SDP Template mechanism proposes using a generic procedure to avoid transmission of frequently used SDP fields. Copyright © 2006 John Wiley & Sons, Ltd.

Availability of GPRS and UMTS networks constitutes a significant piece in the path towards a ubiquitous Internet. To ensure continuity of service, handover from UMTS to GPRS (U2G) and vice versa (G2U) is a key feature for mobile operators and user experience. This paper presents an empirical study on the impact of intersystem handover (ISHO) over the TCP/IP protocol suite. Trials include a variety of different conditions, such as two mobile operators' GPRS and UMTS public networks, uplink and downlink data transmissions, as well as indoor and outdoor scenarios. Measurements have been performed at both IP and TCP layers. Results show that significant connectivity gaps, dramatically increased delays and varying amounts of losses take place as a result of ISHO. We describe the harmful effects of such phenomena on TCP.

The IEEE 802.15.4 standard is expected to enable a wide variety of envisaged low-cost control and monitoring applications with relaxed throughput requirements and a strong emphasis on power conservation. A routing protocol is needed for the mesh topology approach, which must take into account the very limited features of the network. In this paper we provide a three-fold contribution. We first review and discuss the main AODV based routing protocol proposals and/or implementations suitable for the quoted environments. Next, we present NST-AODV, a new AODV implementation designed to provide benefits in terms of data delivery latency, network reliability and power consumption, specially in dynamic topology networks. Finally, we evaluate the tradeoffs and most critical features of our solution in a real IEEE 802.15.4 mesh sensor network testbed

A key element for MANET performance is the routing protocol. Surprisingly, little effort has been devoted up to now to analyzing the impact of routing protocol parameter settings on MANET performance. We define and study in detail the route change latency (RCL) after link failures, a critical performance metric in a non-static ad-hoc scenario, and its dependence on routing protocol parameter settings and implementation issues using OLSR. We experiment with a set of OLSR settings in a real network environment and derive its potential effect in a generic situation, showing that end-to-end connectivity can be enhanced using different parameter settings from the default ones.

Mobile ad-hoc network (MANET) technology is an essential piece in the path towards ubiquitous networking. In the past, most MANET research has been performed assuming the random waypoint mobility model for determining nodes movements. In the last years, some researchers have focused on alternative mobility models. In this paper, we perform a simulation based joint analysis of ad-hoc network performance at three layers (physical layer, network layer and transport layer) using four different mobility models, AODV as the routing protocol and TCP as the transport protocol. In some cases, we obtain counterintuitive results, which can be explained by correlating the behavior measured at the three considered layers

Mobile ad-hoc network (MANET) technology is an essential piece in the path towards a ubiquitous Internet. MANET routing protocol parameter configuration should be further analyzed since it may significantly impact network performance. In this paper, we perform tests in real MANET environments using the ad-hoc on-demand distance vector (AODV) routing protocol. We study the influence of the protocol, the implementation and a set of AODV link maintenance mechanisms parameter values on network performance, suggesting that usage of different settings from those proposed by default increase reactivity after topology changes with small impact on bandwidth and power consumption in a set of scenarios

3G wireless networks such as UMTS are currently providing wide area Internet access. However, the Internet protocols exhibit a suboptimal performance in such scenarios. In this paper we first characterize a live UMTS link from the IP level. We identify critical features such as high latency, delay spikes, high packet loss probability and connectivity gaps, specially when the user moves between cells. Next, we test a set of TCP configurations, demonstrating that TCP performance can be optimized over UMTS by the usage of adequate end-to-end mechanisms and parameter values.