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Performing flow control inside a network can effectively avoid packet loss due to buffer overflow in switches. IEEE 802.3x exercises a per-hop link-based flow control scheme to achieve this goal. IEEE 802.1Qbb Priority-based Flow Control (PFC) improves IEEE 802.3x by proposing a per-hop per-service-class flow control scheme. Although PFC is better than IEEE 802.3x, it still suffers from several serious problems such as congestion spreading, deadlock, and packet loss. In this work, we propose a per-hop per-flow scheme to mitigate these problems. We design, implement, and evaluate the performance of our scheme in P4 hardware switches. Experimental results show that (1) our scheme outperforms PFC in many aspects including avoiding congestion spreading, deadlock, and packet loss, and (2) the bandwidth overhead of our scheme is only slightly higher than that of PFC.

Hybrid broadcasting utilizing heterogeneous networks can provide not only Audio/Video(A/V)-based unidirectional broadcast services but also various interactive A/V and data services via both broadcast and communication networks. Customers of hybrid broadcasting services can then consume A/V content that is transmitted from broadcasting stations and data services relevant to A/V content through communication networks, such as the Internet. Since interactive data can be widely ingested in various countries and regions, it is advantageous for it to be customized for personalized services depending on consumer preferences and locations. However, the current broadcasting standard has not yet defined a standardized method of inserting content into a broadcasting program. Thus, the research on content insertion technology using heterogeneous networks is actively progressing. The most important technical challenge of inserting content is rendering a smooth replacement of on-air broadcast content with media data through communication networks and an accurate return to the over-the-air broadcast content consistent with the rendering timeline using legacy receivers. Since most legacy receivers have one decoder, both the inserted content and the broadcast content have to be handled by one decoder. When two video streams are processed by one decoder, decoding and rendering problems due to the buffer overflow may occur, and buffer management of the decoder is required to solve this problem. Therefore, this paper proposes a content insertion method of using a frame control-based receiver buffer model to enable smooth and accurate rendering of inserted and on-air content without any blackout scenes.

RISC-V is a promising open-source architecture that targets low-power embedded devices and system-on-chips (SoCs). However, there is a dearth of practical and low-overhead security solutions in the RISC-V architecture. Programs compiled using RISC-V toolchains are still vulnerable to code injection and code reuse attacks, such as buffer overflow and return-oriented programming (ROP). In this article, we propose two hardware-implemented security extensions to RISC-V that provides a defense mechanism against such attacks. We first employ a physically unclonable function (PUF)-based randomized canary generation technique that removes the need to store the sensitive canary words in memory or CPU registers, thereby being more secure, while incurring low overheads. We implement the proposed Canary Engine in RISC-V RocketChip with rocket custom coprocessor (RoCC). The simulation results show 2.2% average execution overhead with a single buffer protection, while a $10\times $ increase in buffer count only increases the overhead by $1.5\times $ when protection is extended to all buffers. We further improve upon this with a dedicated security coprocessor flow integrity extensions for embedded RISC-V (FIXER), implemented on the RoCC. FIXER enforces fine-grained control-flow integrity (CFI) of running programs on backward edges (returns) and forward edges (calls) without requiring any architectural modifications to the processor core. Compared to software-based solutions, FIXER reduces energy overhead by 60% at minimal execution time (1.5%) and area (2.9%) overheads.

Today, a code reuse technique is often used when exploiting software vulnerabilities, such as a buffer overflow. These attacks bypass the protection against execution of code in the stack, which is implemented on the hardware and software levels in modern information systems. The attacks are based on finding suitable sections of executable code–gadgets–in the vulnerable program and linking these gadgets into chains. The article proposes a method to protect applications against code reuse attacks. The method is based on detecting properties that distinguish between chains of gadgets and typical chains of legitimate program basic blocks. The appearance of an atypical chain of basic blocks during program execution may indicate the execution of a malicious code. One of the properties of a chain of gadgets is that at the end of the chain a special processor instruction used to call a function of the operating system is executed. Experiments are carried out for the x86/64 Linux operating system which show the importance of this property for detecting malicious code execution. An algorithm for identifying atypical chains is developed which makes it possible to detect all currently known code reuse techniques.

Recently, the demand for technology that can wirelessly transmit images taken by unmanned aerial vehicles (UAVs) has increased. Relay transmission technology is attracting particular attention, as it can provide wireless transmission to remote locations even in environments lacking infrastructure. Here, we focus on further developing an existing relay transmission system, namely, the simultaneous reception and transmission method, using multiple frequency bands. In this method, a relay node receives data from a source node and simultaneously transmits data to a destination node using another channel. This technology has the advantages of high frequency utilization efficiency and a short transmission time; however, buffer overflow at the relay node may remain, which could contribute to video quality degradation. Thus, we propose a buffer control method involving two proposed elements: a channel selection method, and a transmission start timing control method. By applying these two methods, we show that the buffer overflow rate at the relay node is decreased, and the amount of data that can be received by the destination node is maximized within the assigned sub frame. Ultimately, these results can contribute to improving the quality of videos transmitted in real-time using relay transmission with UAVs.

Real-time video transmission is one of the most popular applications that are included in the versatile video coding (VVC) standard. However, real-time applications are encountered with practical limitations, including the buffer size and available bandwidth. In these applications, the buffer overflow and underflow should be strictly prevented and also the bit-rate fluctuation should be suppressed. In this paper, a video bit-rate controller is proposed that completely conforms with the constraints of real-time applications. The proposed controller is based on a multi-layer perceptron (MLP) neural network which estimates the proper quantization parameter (QP) modification at the frame level. The buffer occupancy is directly included in the QP derivation process for robust buffer control. Experimental results show that the proposed bit-rate controller fulfils the buffering constraints and controls the bit-rate accurately. The average bit-rate error of the proposed method is 0.29% while providing a low initial buffering delay of about 0.21 s. Also, the rate-distortion analysis shows that the performance of the proposed method is close to those of the conventional algorithms.

Development of energy-efficient wireless sensor networks is crucial in the deployment of IoT and IIoT for modern day applications like smart home, smart vehicles, and smart industries. Several methods like network clustering, mobile sink deployment and dynamic sensing rate have been used in improving the energy-efficiency of wireless sensor networks in IoT framework. However, these methods have been developed independently which can lead to certain network issues like reduced lifetime, network breakdown among others. In this work, an energy-efficient method that optimizes mobile sink scheduling while concurrently providing dynamic buffer management is proposed. A cooperative network model that incorporates node clustering and mobile sink deployment in variable node sensing rate scenario is first developed. However, in such cooperative network models, mobile sink scheduling and buffer overflow management which causes information loss become challenging. This is primarily due to limited buffer size, variable sensing rate of the nodes, and the unavailability of mobile sink at all times near a cluster. Therefore, a reinforcement Q-learning framework is developed for scheduling the mobile sink while minimizing the information loss caused by buffer overflow in each cluster of a clustered WSN. More specifically, the network behaviour is learnt in the context of buffer overflow using Q-learning approach. The proposed method computes the adaptive halt-times for the mobile sink based on information loss and buffer overflow in each cluster. Performance of the proposed joint mobile sink scheduling and dynamic buffer management method is evaluated on a medium scale WSN. A clustered wireless sensor network with a total of 600 sensor nodes is considered for performance evaluation. The proposed method is shown to learn the variable node sensing rate in a reasonable amount of time using convergence analysis. Numeric evaluations indicate that the proposed method minimizes the information loss in a medium scale wireless sensor network while improving the network lifetime simultaneously. The proposed cooperative network model also outperforms in terms of energy-efficiency when compared to conventional WSN. The results are motivating enough for the use of cooperative network model in practical WSNs for IoT applications.

We analyze a queueing-inventory system which can model airline and railway reservation systems. An arriving customer to an idle server joins for service immediately with exactly one item from inventory at the moment of service completion if there are some on-hand inventory, or else he accesses to a buffer of varying size (the buffer capacity varies and equals to the number of the items in the inventory with maximum size S). When the buffer overflows, the customer joins an orbit of infinite capacity with probability p or is lost forever with probability 1−p. Arrivals form a Poisson process, and service time has phase type distribution. The time between any two successive retrials of the orbiting customer is exponentially distributed with parameter depending on the number of customers in the orbit. In addition, the items have a common life time with exponentially distributed. Cancellation of orders is possible before their expiry and intercancellation times are assumed to be exponentially distributed. The stability condition and steady-state probability vector have been studied by Neuts–Rao truncation method using the theory of Level Dependent Quasi-Birth-Death (LDQBD) processes. Several stationary performance measures are also computed. Furthermore, we provide numerical illustration of the system performance with variation in values of underlying parameters and analyze an optimization problem.

A network of randomly deployed sensor nodes which shares limited resources like bandwidth, buffer, queue, and battery powered nodes is known as wireless sensor network. Such network must have energy, to avoid the chances of congestion because congested network degrades the performance of network. Congestion may occur due to several reasons like data packet collision, transmission channel contention and buffer overflow. A congestion control protocol must acquire the functionalities that can increase the lifetime and efficiency of network which are major responsibilities of wireless sensor network. In this paper traffic oriented, resource oriented and a hybrid approach with some additional functionalities of controlling congestion are discussed in a wide manner. The hybrid approach is best as per this survey as it integrates various factors of wireless sensor networks to control and mitigate the situation. A comprehensive analysis is also done on these factors to justify the nature of different approaches.

Despite all the efforts made by the scientific community in terms of computer security, buffer overflow vulnerabilities continue being the biggest security flaw in applications, since they compromise the security of the system through memory corruption. To tackle this problem, there are different techniques based on the binary analysis of the application in question. With this objective in mind, the present paper proposes an algorithm based on the dynamic instrumentation of binaries, that is, dynamic local variables belonging to the functions of the program are detected, and a check is performed to see whether there is an overflow of memory between them. The results obtained show how the proposed algorithm is able to detect buffer overflow errors in the stack frames of a function.

Congestion detection and management are difficult to realize in Mobile Opportunistic Networks (MONs) due to the lack of end-to-end connectivity, global information, absence of ACKs/NACK messages. One of the simplest means of detecting congestion in any network, primarily in the intermediate nodes, is buffer overflow leading to packet drop. Although researchers in this area have used this phenomenon to detect congestion, this is not always true for a MON, especially under large buffers. We show that in MONs with large buffers, there exists a critical buffer occupancy beyond which congestion sets in, and network performance degrades even though the buffer may not be full. To study this behavior, we develop an analytical model based on forwarding probability by considering the nodes to have a large buffer size and finite bandwidth. Using Epidemic forwarding as the underlying routing protocol, the analytical model is used to detect the exact buffer occupancy that leads to congestion. The theoretical results have been compared with the simulation results to prove the correctness of the model.

Overlapped time domain multiplexing (OvTDM) is an innovative encoding scheme that can obtain high spectral efficiency. However, the intentional inter-symbol interference (ISI) caused by OvTDM will make the decoding process more complex. The computational complexity of maximum likelihood sequence detection increases exponentially with the growth of spectral efficiency in OvTDM. As a consequence of high complexity, the decoding effort for a given spectral efficiency may occasionally exceed the physical limitations of the decoder, leading inevitably to buffer overflows and information erasures. In this paper, we propose a bidirectional Viterbi algorithm (BVA) based on the bidirectional sequence decoding for OvTDM. With the BVA, the decoding operation starts simultaneously from the both ends of the corresponding trellis and stops at the middle of trellis. The simulation results show that compared with Viterbi algorithm (VA), the decoding time of BVA can be reduced by about half. And the memory space of two decoders in BVA are about half of that in VA, which means that the BVA has lower memory requirements for decoder. And the decoding performance of BVA is almost the same as VA.

The subject of the article is the evaluation of the results of a mathematical model consisting of systems of equations that describe the various states of the system and the laws of distribution of packet service time, which allows to investigate the main probability-time characteristics and analyze the operation of a single device. The purpose of the article is to evaluate the results of a mathematical model of the operation of a data network with competing access based on a switching device with a finite buffer size. To achieve the maximum probability, it is necessary to use switches with the optimal size of the buffer, so that the delay was small, and the buffer did not overflow too quickly at high load of the switch, which is the task of this article. A mathematical model consisting of systems of equations describing different states of the system and packet service time distribution laws is proposed, which allows to investigate the main probability-time characteristics and analyze the operation of a single system device and its interaction with other network devices based on the density of the probability distribution of packet service time. The final result is the obtained distribution densities of packet delivery time for different operating modes of the system that can be approximated by the corresponding analytical distribution law. The model allows to calculate the probability of data delivery, taking into account the final size of the buffers used by the data. The conclusion can be considered that, for achievement of the maximum probability it is necessary to use switches with the optimum size of the buffer that both delay was small, and the buffer is not overflowed too quickly at high loading of the switch. Thus, with the help of the developed model it is possible to solve the problem of choosing the optimal size of the switch buffer and estimating the data delivery time. Since buffer overflow leads to loss of information frames, which, in turn, leads to increased packet delivery time.

File systems are too large to be bug free. Although handwritten test suites have been widely used to stress file systems, they can hardly keep up with the rapid increase in file system size and complexity, leading to new bugs being introduced. These bugs come in various flavors: buffer overflows to complicated semantic bugs. Although bug-specific checkers exist, they generally lack a way to explore file system states thoroughly. More importantly, no turnkey solution exists that unifies the checking effort of various aspects of a file system under one umbrella. In this article, to highlight the potential of applying fuzzing to find any type of file system bugs in a generic way, we propose H ydra , an extensible fuzzing framework. H ydra provides building blocks for file system fuzzing, including input mutators, feedback engines, test executors, and bug post-processors. As a result, developers only need to focus on building the core logic for finding bugs of their interests. We showcase the effectiveness of H ydra with four checkers that hunt crash inconsistency, POSIX violations, logic assertion failures, and memory errors. So far, H ydra has discovered 157 new bugs in Linux file systems, including three in verified file systems (FSCQ and Yxv6).

We consider an energy harvesting sensor transmitting latency-sensitive data over a fading channel. We aim to find the optimal transmission scheduling policy that minimizes the packet queuing delay given the available harvested energy. We formulate the problem as a Markov decision process (MDP) over a state-space spanned by the transmitter’s buffer, battery, and channel states, and analyze the structural properties of the resulting optimal value function, which quantifies the long-run performance of the optimal scheduling policy. We show that the optimal value function (i) is non-decreasing and has increasing differences in the queue backlog; (ii) is non-increasing and has increasing differences in the battery state; and (iii) is submodular in the buffer and battery states. Taking advantage of these structural properties, we derive an approximate value iteration algorithm that provides a controllable tradeoff between approximation accuracy, computational complexity, and memory, and we prove that it converges to a near-optimal value function and policy. Our numerical results confirm these properties and demonstrate that the resulting scheduling policies outperform a greedy policy in terms of queuing delay, buffer overflows, energy efficiency, and sensor outages.

In recent years many security attacks occur when malicious codes abuse in-process memory resources. Due to the increasing complexity, an application program may call third-party code which cannot be controlled by programmers but may contain security vulnerabilities. As a result, the users have the risk of suffering information leakage and control flow hijacking. However, current solutions like Intel memory protection extensions (MPX) severely degrade performance, while other approaches like Intel memory protection keys (MPK) lack flexibility in dividing security domains. In this paper, we propose IMPULP, an effective and efficient hardware approach for in-process memory protection. The rationale of IMPULP is user-level partitioning that user code segments are divided into different security domains according to their instruction addresses, and accessible memory spaces are specified dynamically for each domain via a set of boundary registers. Each instruction related to memory access will be checked according to its security domain and the corresponding boundaries, and illegal in-process memory access of untrusted code segments will be prevented. IMPULP can be leveraged to prevent a wide range of in-process memory abuse attacks, such as buffer overflows and memory leakages. For verification, an FPGA prototype based on RISC-V instruction set architecture has been developed. We present eight tests to verify the effectiveness of IMPULP, including five memory protection function tests, a test to defense typical buffer overflow, a test to defense famous memory leakage attack named Heartbleed, and a test for security benchmark. We execute the SPEC CPU2006 benchmark programs to evaluate the efficiency of IMPULP. The performance overhead of IMPULP is less than 0.2% runtime on average, which is negligible. Moreover, the resource overhead is less than 5.5% for hardware modification of IMPULP.

MANET (Mobile Ad hoc Network) is self-configuring, self-organizing, infrastructure-less network of mobile devices connected without wires. Because of the dynamic changes in the network topology, there is no centralized control in ad hoc networks. So, mobile nodes can communicate with each other via intermediate nodes. The buffer size of intermediate nodes plays a significant role to hold packets in the buffer before dropping the newly arrived packets. In MANET, buffer overflow (congestion) occurs in any intermediary nodes when data packets pass through source to destination and incurs packet loss, which causes the performance degradations of a network. Congestion can be reduced by using several Active Queue Management [AQM] techniques. Queue Management Node or “QMN” is an active queue management strategy to control packet drops by assigning space of a buffer node to all its neighbouring nodes dynamically depending upon the total number of packets received from its neighbours. In this scheme, authors did not take into account the impact of collaboration between neighbors of a central node. They only consider the characteristics of nodes, while ignoring the message properties in MANET. And also a new node has to be waiting until it will get enough equal space from the QMN along with other neighbor nodes. During this waiting period, high packet loss can be occurred. So, an efficient buffer overflow control scheme is required to make sure every node has adequate storage space to hold the data once the buffer of the node is near to congestion. In this paper, we proposed a scheme that integrates QMN technique with combinational buffer management (CBM) strategy, which includes both the features of messages and nodes, and transfer the duplicated messages to neighbour node for total utility optimization, rather than deleting them. By using this scheme packet loss can be mitigated in MANETs efficiently. Our simulation results here reveal that, the proposed scheme achieves better performance than other existing schemes in terms of packet delivery ratio, throughput, overhead ratio and end to end delay

A fuzzy rate controller with buffer constraint in combination with a perceptual quality controller is proposed for streaming applications of the AVC/H.264 scalable (SVC) video. The bit rate of each video layer is controlled separately by the fuzzy controller that adjusts the quantization parameter (QP) on a group of pictures (GOP) basis. The QPs of pictures are computed from the GOP QP by the well-known QP cascading technique. While the fuzzy controller provides the buffering constraint for each video layer, the quality controller tries to improve the perceptual quality of the compressed video based on the foveated just-noticeable distortion (FJND) model. The quality controller regulates the QP of each macroblock around the picture QP based on the visibility threshold of the FJND model. In these applications, the initial buffering allows slight variations of the bit rate leading to produce a variable bit rate (VBR) video bit stream with consistent quality. Experimental results show that the proposed algorithm effectively adapts to the buffer size, while strictly prevents buffer overflow and underflow. In addition, incorporating the perceptual quality controller into the fuzzy rate controller achieves higher perceptual quality at the same bit rate.

[ES] A raíz del desarrollo de la técnica de protección NX (Non eXecutable), el uso de shellcodes para la ejecución de código arbitrario se vio seriamente afectado. Fruto de esta limitación, los atacantes desarrollaron nuevas técnicas para poder explotar las vulnerabilidades presentes en los sistemas informáticos. La técnica más importante es ROP (Return Oriented Programming), que permite reordenar el código ejecutable presente en un proceso para conseguir ejecutar lo que un atacante desee. El presente trabajo aborda la implementación de una herramienta en el lenguaje C, que a partir de un fichero ejecutable ELF de la arquitectura de computadores RISC-V, halle todos los gadgets que podrían ser utilizados para la construcción de payloads., [EN] Following the development of the NX (Non eXecutable) protection technique, the use of shellcodes for arbitrary code execution was seen seriously affected. As a result of this limitation, the attackers developed new techniques to exploit the vulnerabilities present. in computer systems. The most important technique is ROP (Return Oriented Programming), which allows reordering the present executable code in a process to get whatever an attacker wants to execute. This paper deals with the implementation of a tool in the C language, which from an ELF executable file of the RISC-V computers, find all the gadgets that could be used for the construction of payloads., [CA] Arran del desenvolupament de la t`ecnica de protecci´o NX (Non eXecutable), l’´us de shellcodes per a l’execuci´o de codi arbitrari es va veure seriosament afectat. Fruit d’aquesta limitaci´o, els atacants van desenvolupar noves t`ecniques per poder explotar les vulnerabilitats presents en els sistemes inform`atics. La t`ecnica m´es important ´es ROP (Return Oriented Programming), que permet reordenar el codi executable present en un proc´es per aconseguir executar el que un atacant desitja. El present treball aborda la implementaci´o d’ una eina en el llenguatge C, que a partir d’ un fitxer executable ELF de l’ arquitectura de computadors RISC-V, trobi tots els gadgets que podrien ser utilitzats per a la construcci´o de payloads.

Fuzz testing is an important means of vulnerability discovery, but now fuzz testing technology is most for application software on traditional computer platforms, which can be not used on embedded software. We propose a fuzzing method for embedded software, which can solve the two technical difficulties: abnormal monitoring and automation. Also, we independent research and develop embedded fuzzy testing tool called Efuzzer. Experiments prove that the tool has very good practicality and is effective for discover buffer overflow vulnerabilities which can cause a system crash. Now the tool is tried in several software testing institutions, a few vulnerabilities were discovered.

In smartphones, and more generally in IoT devices, manufacturers focus their efforts on securing communications with the outside world that are more exposed to attack while considering communications between secure components. By doing this, it results in internal communication buses with little or no security against attackers. I2C is the most used internal communication bus in IoT devices to communicate with sensors and memories. It is also used in recent smartphones to connect the Trusted Execution Environments (ARM TrustZone, Apple SEP, or Google Titan M) to a dedicated EEPROM memory that contains secret information such as encryption keys, anti-replay counter, or the boot ROM. In this paper, we propose a non-invasive attack through a hardware trojan on the I2C bus, which will allow us to perform two attack scenarios: a heart bleeding type attack which will allow retrieving additional information at each memory read, and a buffer overflow attack which will allow writing additional data in the memory at each write which can result in modifying secret information such as password or counters. These attacks can be performed on any device using the I2C bus. In the context of smartphones, these attacks will allow the extraction of sensitive information stored in the secure EEPROM memory.