Network survivability endeavors to ensure the uninterrupted provisioning of services by the network operators in case of a disaster event. Studies and news reports show that network failures caused by physical attacks and natural disasters have significant impacts on the optical networks. Such network failures may lead to a section of a network to cease to function, resulting in non-availability of services and may increase the congestion within the rest of the network. Therefore, fault tolerant and disaster-resilient optical networks have grasped the attention of the research community and have been a critical concern in network studies during the last decade. Several studies on protection and restoration techniques have been conducted to address the network component failures. This study reviews related previous research studies to critically discuss the issues regarding protection, restoration, cascading failures, disaster-based failures, and congestion-aware routing. We have also focused on the problem of simultaneous cascading failures (which may disturb the data traffic within a layer or disrupt the services at upper layers) along with their mitigating techniques, and disaster-aware network survivability. Since traffic floods and network congestion are pertinent problems, they have therefore been discussed in a separate section. In the end, we have highlighted some open issues in the disaster-resilient network survivability for research challenges and discussed them along with their possible solutions.

Passive optical networks (PONs) require a dynamic bandwidth allocation (DBA) algorithm at the optical line terminal for efficient utilization of upstream bandwidth among the optical network units (ONUs) as per the quality of service requirements for each traffic class defined by PON standardizing bodies. The GigaPON access network (GIANT) was the first International Telecommunication Union compliant DBA algorithm, which is further improved by Immediate Allocation with Colorless Grant (IACG) and Efficient Bandwidth Utilization (EBU) algorithms. However, the polling mechanism of IACG and EBU may not report the true bandwidth demand of ONUs during a service interval. Furthermore, ONU scheduling mechanisms give preference to best effort traffic over the assured traffic during recursive allocation cycles in a service interval, which results in an increase in upstream delays for the assured traffic class. This paper presents an improved bandwidth utilization (IBU) algorithm, which rectifies these deficiencies with a novel polling and scheduling mechanism. Experimental results show that IBU improves the mean of upstream delays of type 2 traffic up to 98%, 93%, and 76% and up to 99%, 92%, and 73% for type 3 traffic compared to the GIANT, IACG, and EBU algorithms, respectively. IBU also shows the least frame loss compared to these state-of-the-art algorithms.

Microring resonators (MRRs) can be used to generate optical millimetre‐wave solitons with a broadband frequency of 40–60 GHz. Non‐linear light behaviours within MRRs, such as chaotic signals, can be used to generate logic codes (digital codes). The soliton signals can be multiplexed and modulated with the logic codes using an orthogonal frequency division multiplexing (OFDM) technique to transmit the data via a network system. OFDM uses overlapping subcarriers without causing inter‐carrier interference. It provides both a high data rate and symbol duration using frequency division multiplexing over multiple subcarriers within one channel. The results show that MRRs support both single‐carrier and multi‐carrier optical soliton pulses, which can be used in an OFDM based on whether fast Fourier transform or discrete wavelet transform transmission/receiver system. Localised ultra‐short soliton pulses within frequencies of 50 and 52 GHz can be seen at the throughput port of the panda system with respect to full‐width at half‐maximum (FWHM) and free spectrum range of 5 MHz and 2 GHz, respectively. The soliton pulses with FWHMs of 10 MHz could be generated at the drop port. Therefore, transmission of data information can be performed via a communication network using soliton pulse carriers and an OFDM technique.

In time division, multiple access (TDMA)-based passive optical network (PONs), a dynamic bandwidth assignment (DBA) is necessary for efficient utilization of the available bandwidth of the upstream link. An efficient DBA scheme can improve the upstream performance of a traffic class of an ONU in two ways. First, it can increase the bandwidth assignment to it by efficiently utilizing the available bandwidth. Secondly, it can reduce the channel and frame idle time by increasing the polling frequency and by assigning extra surplus bandwidth not used by the other ONUs. Many DBA schemes have been reported for both ITU PONs (GPON and XGPON) and IEEE PONs (EPON and 10 G EPON). In this study, we explain the impact of DBA scheme on the upstream performance of PON and then do a thorough survey of both PON standards, categorize the DBA schemes and review them critically. Based on the literature review we also give our opinion on the most suitable DBA scheme for both type PONs on the basis of upstream delays, frame loss and bandwidth utilization efficiency.

Wireless Body Area Sensor Network (WBASN) is an automated system for remote health monitoring of patients. WBASN under umbrella of Internet of Things (IoT) is comprised of small Biomedical Sensor Nodes (BSNs) that can communicate with each other without human involvement. These BSNs can be placed on human body or inside the skin of the patients to regularly monitor their vital signs. The BSNs generate critical data as it is related to patient's health. The data traffic can be classified as Sensitive Data (SD) and Non-sensitive Data (ND) packets based on the value of vital signs. These data packets have different priority to deliver. The ND packets may tolerate some delay or packet loss whereas, the SD packets required to be delivered on time with minimized packet loss otherwise it can be life threating to the patients. In this research, we propose a Traffic Priority-aware Medical Data Dissemination (TPMD2) scheme for WBASN to deliver the data packets according to their priority based on the sensitivity of the data. The assessment of the proposed scheme is carried out in various experiments. The simulation results of the TPMD2 scheme indicate a significant improvement in packets delivery, transmission delay and energy efficiency in comparison with the existing schemes.