Internet router buffers are commonly made very large with the aim of minimising losses and maximising link utilisation, supported by the ever-decreasing cost of memory. However, large packet queues not only increase the energy consumption, but can also adversely affect network performance which has recently been attracting attention under ‘bufferbloat’. This study compares the buffer-related energy consumption of two models, that is, ‘large-buffer with on–off server’ and ‘small-buffer with always-on server’ in the presence of multiplexed on–off traffic and FTP traffic; and demonstrates that the latter model is more energy efficient. Further analysis is then carried out on the ‘small-buffer model with always-on server’ for the evaluation of its performance against different levels of energy consumption. Relationships among energy, delay, throughput and loss are studied in a range of scenarios, quantifying the variations in performance metrics in relation to energy consumption. In general, lower buffer sizes which reduce the energy consumption were found to improve delay, but sacrifice throughput by 5–8% at high load. Based on a broad set of results, this study provides guidelines for sizing router buffers in realistic networks which would lead to optimal trade-offs between energy consumption and quality of service.

Packet level measurement is now routinely used to evaluate the loss and delay performance of broadband networks. In active measurement, probe packets provide samples of the loss and delay and from these samples the performance of the traffic as a whole can be deduced. However this is prone to errors: inaccuracy due to taking insufficient samples, self-interference due to injecting too many probe packets, and possible sample-correlation induced bias. In this paper we consider the optimisation of probing rate by treating all measurements as numerical experiments which can be optimally designed by using the statistical principles of design of experiments. We develop an analytical technique that quantifies an overall utility function associated with: (i) the disruption caused per probe packet, (ii) the bias and (iii) the variance as a function of the probing (sampling) rate. Our numerical results show that the optimal probing rate depends strongly on what parameter the network engineer seeks to measure.

The IEEE 802.11 standard uses Carrier Sense Multiple Access with Collision Avoidance to avoid multiple devices simultaneous transmitting on a shared transmission medium. In this study, Bianchi's model for IEEE 802.11 is studied and the authors suggest some important improvements. Firstly, they expand the state space of the Markov chain to model the evolution of a network, instead of a single device. Secondly, they relax the assumption that the network must be saturated. Thirdly, they extend the model to allow for heterogeneous devices with different transmission profiles. They use this new model to perform Monte Carlo simulation to discover the impact of the minimum and maximum contention window times (CW_min and CW_max) in the standard on measures of throughput in a network. By exhaustive search over a parameter space, they find optimal values for these devices for any given network model, and show that the recommended parameters in the IEEE 802.11 standard are not optimal. They consider both average and minimum throughput, and show that increases in throughput of around 8% are possible for saturated networks, and that even greater improvements are possible for any case in which the traffic sources are not homogeneous, that is, any real scenario.

The growing energy consumption has posed new challenges for the future development of networks. Some earlier work has proposed solutions to improve energy consumption based on the existing control plane, for example, node/links sleeping. This study presents a new possibility to reduce network energy consumption by proposing a new integrated control plane structure utilising Software Defined Networking technologies. The integrated control plane increases the efficiencies of exchanging control information across different network domains, while introducing new possibilities to the routing methods and the control over quality of service (QoS). The structure is defined as an overlay generalised multi-protocol label switching (GMPLS) control model. With the defined structure, the integrated control plane is able to gather information from different domains (i.e. optical core network and the access networks), and enable energy efficiency networking over a wider area. In the case presented, the integrated control plane collects the network energy related information and the QoS requirements of different types of traffic. This information is used to define the specific group of traffic's (flow's) routing behaviours. With the flexibility of the routing structure, results show that the energy efficiency of the network can be improved without compromising the QoS for delay/blocking sensitive services.

In this study, the authors study the problem of allowing customers to use their storage energy, grid energy, as well as privately owned renewable sources of energy. The customer has three options – grid, storage and self-generated energy, to fulfill the energy requirements. The grid decides real-time price to maximise its revenue, while ensuring customers’ participation depending on three factors – ‘demand’, ‘supply’ and ‘time of use’. On the other hand, a customer needs to choose strategies on his/her required energy and associated cost, depending on the storage and self-generated energy, to maximise the pay-off. They use Markov decision process (MDP) to design this decision making policy of the customer. In such a MDP-based decision model, a cost-effective energy management process is established, and, thus, utility of the customers is maximised. Simulation results show that using the proposed approach, the customers decide the strategies to optimise a trade-off between energy exchange and associated cost. Thus, the utility for customer is increased approximately 60% with the presence of grid, storage and self-generated energy sources than that of using only grid and storage energy.

The fast handover Mobile IPv6 (FMIPv6) offers a handover preparation mechanism for a mobile node (MN) to reduce the handover latency over wireless network. However, FMIPv6 mainly deals with one MN instead of multiple MNs. In the wireless network, a group of MNs may move from the same previous network to the next network. In this paper, a group-based fast handover (GB-FH) control scheme is proposed to resolve the aforementioned problem. For the proposed GB-FH scheme, one MN initiates a handover preparation and other neighboring MNs can join the handover preparation using the “hitch-and-ride” concept, which means that when one MN is preparing for a handover, its neighbours can join the on-going handover preparation. Through the use of the shared invocation of the handover preparation procedure, (1) the handover preparation delay and handover latency can be reduced for about 20% and 8% respectively comparing with FMIPv6, (2) handover control messages can be reduced for about 57% comparing with FMIPv6 and (3) the contention of the wireless channel for multiple MNs can be improved due to the use of fewer control messages.

Wireless body area networks (WBANs) can help in enabling efficient patient monitoring solution for ubiquitous healthcare. Communication in WBANs is undertaken in two phases: intra-WBAN and extra-WBAN. The prevailing WBANs use cellular network or WiFi in the extra-WBAN phase involving communication between the on-body coordinator and access points (APs) connected to the medical server through the internet. The medical applications of the WBANs have stringent requirements of low end-to-end delay and high packet delivery ratio. The authors evaluate the performance of extra-WBAN communication in the network of WBANs which is deployed within a building environment. They proposed a mobility model named random room mobility (RRM), which is used to capture the dynamics of WBAN user mobility within the building. They studied the performance of extra-WBAN communication using the proposed mobility model and a random waypoint mobility model. The metrics used in evaluating the performance are packet drop ratio, average node-to-AP delay and average residual energy per node. The authors show that with an increase in the number of WBANs, the traffic generation rate and the payload size have high impact on the packet loss in the network. They studied the performance of extra-WBAN communication using the priority mode available in IEEE 802.11 for provisioning quality-of-service (QoS). We show that it is suitable for medical applications, when the size of network consisting of WBANs, including the QoS-enabled WBANs, is small.

In this study, the authors investigate epidemic failure spreading in large-scale transport networks under generalised multi-protocol label switching control plane. By evaluating the effect of the epidemic failure spreading on the network, they design several strategies for cost-effective network performance improvement via differentiated repair times. First, they identify the most vulnerable and the most strategic nodes in the network. Then, via extensive event-driven simulations they show that strategic placement of resources for improved failure recovery has better performance than randomly assigning lower repair times among the network nodes. They believe that the event-driven simulation model can be highly beneficial for network providers, since it could be used during the network planning process for facilitating cost-effective network survivability design.

The transition from IPv4 to IPv6 is an inexorable trend in the development of Internet. However, since IPv4 has been widely deployed for many years, it is mandatory that the existing IPv4 and the newly deployed IPv6 coexist and interoperate seamlessly. With the study of various mechanisms proposed for the interoperability between IPv4 and IPv6, some mobility management protocols are also extended to work in the mixed mobile Internet. In this study, the authors carry out an in-depth analysis of three types of standardised mobility management protocols with dual-stack support. Owing to the difference of underlying basic protocols, their individual dual-stack extensions have different features and thus are suited for deployment in different scenarios and stages in the evolution of the mobile Internet.