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This paper considers a wireless networked control system (WNCS) where the controller and controlled object (plant) are connected via an unreliable wireless network. The control system should be designed considering the reliability of the given network while its network reliability is controllable by changing transmission power. Thus, this paper provides a joint optimization of transmission power and control-input for the focused WNCS, which is a kind of cross-layer design of communication and control layers. This work assumes that the total transmission power for the feedforward (from the controller to plant) and feedback (from the plant to controller) channels is limited and can be adaptively allocated to each wireless channel. If more transmission power is allocated to the feedforward channel, the control-input can be more reliably transmitted, while the control-state is less reliably transmitted over the feedback channel. Furthermore, the appropriate power allocation depends on the control-state and the previous communication results. Considering the above facts, this paper proposes a model-predictive control (MPC) based joint optimization and shows that the proposed system can provide appropriate power allocation and control-input and thus can enhance the quality of control.

The usage of internet protocol for voice communication is widely used and more efficient rather than an analog signal. However, there is no security guaranteed on IP-based voice communication. The voice payload can be easily tapped or even manipulated. In the case of improving the security aspect, communication quality should be also considered. VoIP requires sufficient bandwidth to get proper communication quality. The ITU-T released a standard unit of communication quality, known as Mean Opinion Score (MOS) which is made from the subjective judgments of some individuals. However, MOS method takes time and is expensive. In this research, we measure VoIP communication which is secured by using VPN and build a tool for analyzing the voice packet between communication peers. The tool has capabilities to measure delay, jitter, and packet loss. Since VoIP has a QoS standard by ITU-T, the usage of VPN for security purpose needs to be considered. The sound quality might be decreased due to the addition of header for tunneling method, as well as the additional delay when the encryption processing is carried out. We used 3 types of codec: a-Law, GSM, and iLBC which will be passed on 4 types of bandwidth (256, 128, 64, 32 kbps) through the UDP-based VPN that use 3 types of encryption method (3-DES, Blowfish, AES).

The TCP/IP network stack defines two completely different protocols at the transport layer - TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). Being defined above the network layer and corresponding IP protocols (IPv4 and IPv6), both transport layer protocols include additional identification (addressing) of network processes, by introducing a transport layer port. All the other features are TCP or UDP specific - while TCP provides reliable communication, flow and congestion control mechanisms, establishing a virtual connection between source and destination, UDP offers simple (and unreliable) exchange of user datagrams. Theoretically, TCP and UDP have almost nothing in common. But, standard communication between clients and servers may look functionally the same for end-users not familiar with networking theory details. That is why we find it quite important to give a proper, lab example based explanation of protocol differences when teaching networking to STEM students. This paper gives a short introduction to the transport layer protocols and standard client-server architecture. It includes a description of our standard networking lab - using the well-known, but quite simple tool called netcat (nc) both TCP and UDP client-server communication are implemented on the virtual testbed network. Generated and exchanged traffic is analyzed using Wireshark, and a few specific events and protocol behaviors are noted and explained. TCP connection establishment and termination is discused and visualized, too. The goal of the paper is to provide an explanatory example that can help STEM students understand both the usage and differences of standard transport layer protocols. The educational relevance of the paper is summarised as follows. STEM students, especially engineers, should be familiar with basic details of networking: TCP and UDP differences and specifics, with emphasis to TCP as most used transport protocol. The paper shows that it can be identified and analysed using virtual testbed based labs (controlled, but completely realistic environment), which should be considered a benefit for engineering oriented students.

Developments in computer networking have raised concerns of the associated Botnets threat to the Internet security. Botnet is an inter-connected computers or nodes that infected with malicious software and being controlled as a group without any permission of the computer’s owner. This paper explores how network traffic characterising can be used for identification of botnet at local networks. To analyse the characteristic, behaviour or pattern of the botnet in the network traffic, a proper network analysing tools is needed. Several network analysis tools available today are used for the analysis process of the network traffic. In the analysis phase, the botnet detection strategy based on the signature and DNS anomaly approach are selected to identify the behaviour and the characteristic of the botnet. In anomaly approach most of the behavioural and characteristic identification of the botnet is done by comparing between the normal and anomalous traffic. The main focus of the network analysis is studied on UDP protocol network traffic. Based on the analysis of the network traffic, the following anomalies are identified, anomalous DNS packet request, the NetBIOS attack, anomalous DNS MX query, DNS amplification attack and UDP flood attack. This study, identify significant Botnet characteristic in local network traffic for UDP network as additional approach for Botnet detection mechanism.

LAN Chat Messenger using TCP/IP offers reliability, security and zero cost communication among staff members of acompany. As well, this study offers file transfer. It helps to solve the communication problems that related to time and cost. The proposedprotocol facilitates information exchange among individuals by providing many communication options. It is a standaloneapplication using JAVA as the programming language and tested at LANs of our institute (college's Labs networks).

Mobile Ad hoc Network (MANET) is a combination of wireless nodes that share resources and information. One of the major issues in MANET is to minimize the energy consumption of wireless nodes. Higher energy consumption nodes minimize the network life while lower energy consumption nodes increase the network life. Various routing protocols have been proposed for energy saving. Ad hoc On-demand Distance Vector (AODV) is an energy efficient routing protocol. In this paper, the energy based performance of AODV routing protocol is evaluated under Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) by using different simulation scenarios. NS2 has been used for simulation purposes. An energy model is defined in which power for receiving and transmitting one packet, initial energy, sleep power, idle power, transition power and transition time values are kept constant for different simulation scenarios. The simulation results show that AODV routing protocol consumes less energy in TCP environment as compared to UDP environment.

A comprehensive experimental study to analyze the security performance of a WLAN based on IEEE 802.11 b/g/n standards in various network scenarios is presented in this paper. By setting-up an experimental testbed we have measured results for a layered security model in terms of throughput, response time, encryption overheads, frame loss and jitter. Through numerical results obtained from the testbed, we have presented quantitative as well as realistic findings for both security mechanisms and network performance. It establishes the fact that there is always a tradeoff between the security strength and the associated network performance. It is observed that the non-roaming network always performs better than the roaming network under all network scenarios. To analyze the benefits offered by a particular security protocol a relative security strength index model is demonstrated. Further we have presented the statistical analysis of our experimental data. We found that different security protocols have different robustness against mobility. By choosing the robust security protocol, network performance can be improved. The presented analysis is significant and useful with reference to the assessment of the suitability of security protocols for given real time application.

It is a well-known fact that the forthcoming names are distinctively different: interference range, career sense, and transmission. The given paper reveals the underlying study of disengagement of a request to send (RTS)/ clear to send (CTS) dialog. It was basically adopted under the influence of both; the presence of distributed coordination function of IEEE 802.11 and a sub-layer protocol which is called media access control (MAC) protocol. The demonstration was seen when applying a type of traffic flows such as Constant Bit Rate (CBR), Transmission Control Protocol (TCP), and besides User Datagram Protocol (UDP). When these are applied the output performance in term of throughput shows a very linear topology configuration of the network. To sum up, a new RTS /CTS mechanism was proposed based on the results obtained from the above suggestions. The detailing for the new mechanism showed that a terminal node will be responsible for deciding if it is authorized to use an RTS/CTS protocol dialog to send one of its packets or not. Needless to say, this process will be dynamic in nature.

Cloud computing, with its staggering and on-demand services had revamped the technology so far. Cloud consumers are freely to use the applications and software on the premises of Pay-as-you go concept. This concept decreased the cost and make the services less expensive and more reliable. One of the most important characteristic of cloud structure is on demand self-service. Cloud computing applications can be accessed anywhere at any time with much less cost. As cloud provide its consumers with its tremendous on demand services, besides this it is surviving from the excruciating security issues that are discourteous towards the cloud. There are, as many different attacks that results in making the servers down. One of the most hazardous attack is DDoS. This paper hiloghted the DDoS attack and its prevention technique which results in making the server side less vulnerable. The scenario includes, a transmission of million and trillion of packets in the form of DDoS at cloud-based websites, thus making it differentiated though different hosts. Making use of operating systems such as ParrotSec to make the attack possible. Last step includes detection and prevention through the most effective algorithms namely, Naive Bayes and Random forest. This paper also focused the categories of attacks on cloud computing.

The fifth generation (5G) mobile technology features the ultra-reliable and low-latency communications (URLLC) as a major service class. URLLC applications demand a tight radio latency with extreme link reliability. In 5G dynamic time division duplexing (TDD) systems, URLLC requirements become further challenging to achieve due to the severe and fast-varying cross link interference (CLI) and the switching time of the radio frame configurations (RFCs). In this work, we propose a quasi-dynamic inter-cell frame coordination algorithm using hybrid frame design and a cyclic-offset-based RFC code-book. The proposed solution adaptively updates the RFCs in time such that both the average CLI and the user-centric radio latency are minimized. Compared to state-of-the-art dynamic TDD studies, the proposed scheme shows a significant improvement in the URLLC outage latency, i.e., ∼ 92% reduction gain, while boosting the cell-edge capacity by ∼ 189% and with a greatly reduced coordination overhead space, limited to B-bit.

Extracelluar nucleotides have been identified as regulatory factors in asthmatic pathogenesis by activating purinergic receptors. This research aimed to investigate the function of the purinergic receptor P2Y6 in mediating airway inflammation in allergic asthma. Wild-type (WT) and P2Y6-deficient mice were stimulated with ovalbumin (OVA) to construct asthmatic mouse models. Overexpression of P2Y6 and uridine 5'-diphosphate (UDP)-releasing were demonstrated in lung tissues in ovalbumin-induced asthmatic mice. The release of the cytokine IL-4, mast cell invasion, and the airway remodeling phenotypes were more severe following the application of UDP in asthmatic mice. However, P2Y6 deficiency reduced these asthmatic pathogeneticsymptoms markedly in a mouse model. In vitro, we found that P2Y6 in purified mast cells enhanced the functions of mast cells in the inflammatory response in the asthmatic process by triggering their capability for migration, cytokine secretion and granule release. Moreover, P2Y6 stimulated the function of mast cells through activation of the AKT signaling pathway. Our data provides evidence that P2Y6 contributes to allergic airway inflammation and remodeling by enhancing the functions of mast cells in ovalbumin-induced asthmatic mice.

Fixed-point models have already been successfully used to analytically study networks consisting of persistent TCP flows only, or mixed TCP/UDP flows with a single queue per link and differentiated buffer management for these two types of flows. In the current study, we propose a nested fixed-point analytical method to obtain the throughput of persistent TCP and UDP flows in a network of routers supporting class-based weighted fair queuing allowing the use of separate queues for each class. In particular, we study the case of two classes where one of the classes uses drop-tail queue management and is intended for only UDP traffic. The other class targeting TCP, but also allowing UDP traffic for the purpose of generality, is assumed to employ active queue management. The effectiveness of the proposed analytical method is validated in terms of accuracy using ns-3 simulations and the required computational effort.

The purpose of this paper is to work on the cross-layer design and study the impact of transport layer protocol; Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) on the quality of service parameters of ad hoc network using Improved Ad hoc On-Demand Distance Vector Routing(IAODV) protocol. IAODV has a cross-layer approach with improvements on the physical layer, data link layer and transport layer. It combines the effect of modifications in expanded ring search, wait time and time to live; and allows node participation only above a set energy level while establishing a route. At transport layer, selection of TCP or UDP protocol will help in optimizing the performance of overall ad hoc network. The simulation result indicates that UDP performs better for the specified optimized values of IAODV. Our results show that the improved protocol IAODV offers lower Energy consumption in the range of 12% to 23%, End to End Delay is reduced in the range of 12% to 27%. The performance on account of PDR remains same for both AODV and IAODV. By deploying UDP protocol for transport layer using Constant Bit Rate (CBR) traffic further improves the performance of the end to end delay, retransmissions and overhead over 30%. The performance of energy and packet delivery ratio remains unaffected.

// Xiaobin Ma 1 , Xinhua Pan 1 , Yinglei Wei 1 , Binhe Tan 1 , Linli Yang 1 , Hua Ren 1 , Min Qian 1 , Bing Du 1 1 Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China Correspondence to: Bing Du, email: bdu.ecnu@gmail.com Keywords: UDP, P2Y 6 , MMP-9, metastasis, breast cancer Received: November 30, 2015 Accepted: March 28, 2016 Published: April 09, 2016 ABSTRACT Although purinergic signaling is important in regulation of immune responses, the therapeutic potential of it in the tumor microenvironment is little defined. In this study, we demonstrate that UDP/P2Y 6 signaling facilitates breast cancer metastasis both in vitro and in vivo . We found that P2Y 6 is not only aberrantly expressed and mutated in most tumor types, but also highly correlated with poor prognosis in breast cancer patients. Furthermore, the migration and invasion of breast cancer cells was obviously increased by UDP and blocked by P2Y 6 specific inhibitor MRS2578 and P2Y 6 shRNA. Similar results was also found in breast cancer cell metastasis mouse model. Interestingly, the endogenous agonist UDP was released significantly by doxorubicin treated cells. In addition, the expression and enzyme activity of MMP-9 were both promoted by UDP and inhibited by MRS2578 or P2Y 6 shRNA. Furthermore, UDP-induced cell invasion was blocked by an MMP-9 inhibitor. Mechanistically, the MAPKs and NF-κB signaling pathways, known to be involved in regulation of MMP-9 expression, were both activated by UDP. Taken together, our study reveals a relationship between extracellular danger signals and breast cancer metastasis, which suggests the potential therapeutic significance of UDP/P2Y 6 signaling in cancer therapy.

The fifth generation (5G) of the wireless communication networks supports wide diversity of service classes, leading to a highly dynamic uplink (UL) and downlink (DL) traffic asymmetry. Thus, dynamic time division duplexing (TDD) technology has become of a significant importance, due to its radio frame flexibility. However, fully dynamic TDD systems suffer from potentially severe inter-cell cross link interference (CLI). In this paper, we propose a novel inter-cell radio frame coordination (RFC) scheme based on sliding codebook for fully dynamic TDD 5G networks. Proposed coordination scheme simultaneously addresses two optimization objectives of minimizing the average CLI while reliably maximizing the achievable DL/UL capacity, by virtually extending the RFC degrees of freedom through a sliding phase-offset RFC codebook design. Compared to the state-of-the-art TDD studies, the proposed scheme shows significantly improved ergodic capacity, i.e., at least 140% gain under both the TCP and UDP protocols, and with much less signaling overhead, limited to B-bit. The paper offers valuable insights about how to most efficiently pre-mitigate potential CLI in Macro TDD systems.

This paper describes a test platform for verifying the functionality of network protocols as well as optimizing their parameters. The test bed is made by using combined OPNET simulator and MATLAB development environment. This test platform connects OPNET network protocols simulator with MATLAB development environment in the way that OPNET runs simulations of network traffic, with predetermined parameter values, while MATLAB executes the script with a mathematical algorithm, which optimizes parameters listed in OPNET simulator. Video traffic is generally transmitted via UDP protocol on the transport layer in TCI/IP model. Recently, alternatives for the transmission of video traffic have emerged with the use of the transport layer TCP protocol. As an exemplary use of the test platform, we performed the analysis of these two approaches, in addition to their comparison using simulations.

In this paper, we use a New Radio (NR) simulator, based on ns-3, to assess the impact of 5G NR numerologies on the end-to-end (E2E) latencies in a realistic and complex scenario, including TCP and UDP flows. As expected, we found that TCP goodput increases with the numerology, since a larger numerology allows reducing the round-trip-time. However, although counter-intuitive, simulation results exhibit that the E2E latency of uplink (UL) UDP flows may not be reduced with the numerology. In fact, it depends on two key factors and their relationship: the processing delays (fixed or numerologydependent) and the inter-packet arrival time, which depends on the UDP flow rate and the packet size. We demonstrate how, in some cases, the latency is worsened by an increasing signaling exchange that grows with the numerology. In particular, this is due to a handshake mechanism in UL (scheduling request and UL grant) that is performed each time a data packet encounters empty RLC buffers. For some combination of flow rate, packet size, and processing delays that are not numerology dependent, increasing the numerology may not reduce the E2E delay. Therefore, we conclude that the selection of the numerology in an NR system should be carefully made by taking into account the traffic patterns and the processing delays.

In modern cars, Electronic Control Units (ECUs) can have more than one CPU which can exchange data over built-in communication network. Since majority of these ECUs can be categorized as real-time system, special attention should be given to the communication performance between processors. In this paper, analysis of TCP/IP protocol stack for 100 Base-TX Ethernet used for Inter-Processor communication for a specific system on a chip is given. The analysis is performed regarding throughput, goodput and latency from application layer using a test application. On the transport layer UDP was used. The obtained results revealed the impact of the Linux scheduler on the performance of data sending. Apart from that, an optimal packet size was determined by taking into account obtained latency and throughput.

Time is critical for certain types of dynamic information (e.g. frequency control) in a smart grid scenario. The usefulness of such information depends upon the arrival within a specific frame of time, which in other case may not serve the purpose and effect controller’s performance. In this context, transport layer offers different levels of end-to-end communication services to the applications. For instance, TCP guarantees the transport of messages between two ends, however, at the cost of high end-to-end delays due to the retransmission mechanism. Whereas UDP offers minimum end-to-end delays at the cost of unreliable, best-effort data transportation service. The research question raised in this paper is thus, which is preferred for the delay-critical applications of smart grids, and to what degree of packet losses and round trip times, TCP is preferable to UDP and vice versa. The question is addressed by analyzing the performance of UDP and TCP over imperfect network conditions to show how the selection of transport layer protocol can dramatically affect controller’s performance. This analysis is based on a quality metric called mismatch probability that considers occurrence of events at grid assets as well as the information update strategy in one single metric which otherwise is not very intuitive and difficult to allow a similar useful comparison. Further, the analysis is concluded by providing a clear guide on the selection of the transport protocol to meet application requirements.

The growth in users streaming videos on the Internet has led to increased demand for improved video quality and reception. In next generation networks (NGNs), such as 3G and 4G LTE, quality of service (QoS) implementation is one of the ways in which good video quality and good video reception can be achieved. QoS mainly involves following an industry-wide set of standard metrics and mechanisms to achieve high-quality network performance in respect of video streaming. Adopting routing and communication protocols is one way QoS is implemented in NGNs. This article describes QoS of bit rate video streaming, and QoS performance analysis of video streaming, in relation to the main network transport protocols, namely transmission control protocol (TCP) and user datagram protocol (UDP). A simulation test bed was set up using OPNET modeller 14.5. In this setup, a network topology was created and duplicated three times, in order to configure two simulation scenarios (each using the distinct protocols), and a third simulation scenario using both protocols in hybrid form. The findings in the simulations indicated that, when a network is configured with both TCP and UDP protocols in video streaming, there is a positive change in the degree of performance in terms of the QoS of videostreaming applications, unlike when the protocols are used independently.

This article presents a distributed control mode at high-speed data communication by using UDP datagram based on a dual-port RAM, with the purpose of exploring an efficient, low CPU occupancy, high-speed, reliable and large amounts of data exchange mode. One port of the proposed dual-port RAM mode is connected to local CPU, which can be easily read and write data and the other port is connected to the reading and writing and communication control dedicated logic, which is responsible for organizing, sending, receiving and analyzing UDP datagram and also for completing the tasks of reading and writing dual-port RAM and sending interrupt request to the local processor. This model not only realizes efficient data exchange, but also provides real-time interrupt response mechanism. In this article, it discusses the functional modules required for these functions, describes the composition of the system and the advantages of technical performance. It also analyzes the feasibility of its development, and demonstrates that this model is an advanced, high performance distributed control communication program with great promising.

Active Queue Management (AQM) techniques have been proposed to support scenarios with many connections sharing the same bottleneck. The basic idea is that a smart management of the bottleneck queue can avoid the saturation of the link and ensure a smoother use of the available bandwidth. This is generally achieved by exploiting the flux control mechanism of TCP and its behavior in case of packet losses or other explicit notifications. In this paper we consider classic and innovative AQM techniques and analyse their performance under different scenarios through the use of mean field models.

In this work we report the final results of the field demonstration of the European FP7 mPlane project concerning the evaluation of the network performance with particular details regarding the access Quality of Service and traffic monitoring. We show how the proposed and experimented architecture of this measurement plane is fundamental for many future internet evolutions concerning user perception, content popularity web quality and network management. Here we point out the results dedicated to service level agreement verification and certification with analysis of the correlation between passive and active measurements in order to understand some causes concerning network and service anomalies.

Proceedings of the 2016 Applied Networking Research Workshop (ANRW '16), ISBN:978-1-4503-4443-2

Multimedia applications such as video conference, digital video broadcasting (DVB), and streaming video and audio have been gaining popularity during last years and the trend has been to allocate these services more and more also on mobile users. The demand of quality of service (QoS) for multimedia raises huge challenges on the network design, not only concerning the physical bandwidth but also the protocol design and services. One of the goals for system design is to provide efficient solutions for adaptive multimedia transmission over different access networks in all-IP environment. The joint source and channel coding (JSCC/D) approach has already given promising results in optimizing multimedia transmission. However, in practice, arranging the required control mechanism and delivering the required side information through network and protocol stack have caused problems and quite often the impact of network has been neglected in studies. In this paper we propose efficient cross-layer communication methods and protocol architecture in order to transmit the control information and to optimize the multimedia transmission over wireless and wired IP networks. We also apply this architecture to the more specific case of streaming of scalable video streams. Scalable video coding has been an active research topic recently and it offers simple and flexible solutions for video transmission over heterogeneous networks to heterogeneous terminals. In addition it provides easy adaptation to varying transmission conditions. In this paper we illustrate how scalable video transmission can be improved with efficient use of the proposed cross-layer design, adaptation mechanisms and control information.

This paper investigates "Quick UDP Internet Connections" (QUIC), which was proposed by Google in 2012 as a reliable protocol on top of UDP in order to reduce Web Page retrieval time. We first check, through experiments, if QUIC can be safely deployed in the Internet and then we evaluate the Web page load time in comparison with SPDY and HTTP. We have found that QUIC reduces the overall page retrieval time with respect to HTTP in case of a channel without induced random losses and outperforms SPDY in the case of a lossy channel. The FEC module, when enabled, worsens the performance of QUIC.

The demand for internet applications has increased rapidly. Providing quality of service (QoS) requirements for varied internet application is a challenging task. One important factor that is significantly affected on the QoS service is the transport layer. The transport layer provides end-to-end data transmission across a network. Currently, the most common transport protocols used by internet application are TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). Also, there are recent transport protocols such as DCCP (data congestion control protocol), SCTP (stream congestion transmission protocol), and TFRC (TCP-friendly rate control), which are in the standardization process of Internet Engineering Task Force (IETF). In this paper, we evaluate the performance of UDP, DCCP, SCTP and TFRC protocols for different traffic flows: data transmission, video traffic, and VOIP in wired networks. The performance criteria used for this evaluation include throughput, end to end delay, and packet loss rate. Well-known network simulator NS-2 used to implement the UDP, DCCP, SCTP, and TFRC protocols performance comparison. Based on the simulation results, the performance throughput of SCTP and TFRC is better than UDP. Moreover, DCCP performance is superior SCTP and TFRC in term of end-to-end delay.

Cataloged from PDF version of article. In this paper, we introduce BilMesh, an indoor 802.11 b/g mesh networking testbed we established, and we report about our performance experiments conducted on multi-hop topologies with single-radio and multi-radio relay nodes. We investigate and report the effects of using multi-radio, multi-channel relay nodes in the mesh networking infrastructure in terms of network and application layer performance metrics. We also study the effects of physical channel separation on achievable end-to-end goodput perceived by the applications in the multi-radio case by varying the channel separation between the radio interfaces of a multi-radio relay node. We have observed that the difference between TCP and UDP goodput performances together with the delay and jitter performance depends on the hop count. We also observed that assigning overlapping channels with a central frequency separation of 5-15 MHz may render the CSMA mechanism used in 802.11 MAC ineffective and hence reduce the overall network performance. Finally, we provide some suggestions that can be considered while designing related protocols and algorithms to deal with the observed facts. (C) 2013 Elsevier Ltd. All rights reserved.

International audience; The evolution of the Internet has been mainly promoted in recent years by the emergence and proliferation of wireless access networks towards a global ambient and pervasive network accessed from mobile devices. These new access networks have introduced new MAC layers independently of the legacy “wire-oriented” protocols that are still at the heart of the protocol stacks of the end systems. This principle of isolation and independence between layers advocated by the OSI model has its drawbacks of maladjustment between new access methods and higher-level protocols built on the assumption of a wired Internet. In this paper, we introduce and deliver solutions for several pathological communication behaviors resulting from the maladjustment between WLAN MAC and higher layer standard protocols such as TCP/IP and UDP/IP. Specially, based on an efficient analytical model for WLANs bandwidth estimation, we address in this paper the two following issues: (1) Performance degradation due to the lack of flow control between the MAC and upper layer resulting in potential MAC buffer overflow; (2) Unfair bandwidth share issues between various type of flows. We show how these syndromes can be efficiently solved from neutral “cross layer” interactions which entail no changes in the considered protocols and standards.

The adoption of the IPv6 networking in IEEE 802.15.4 sensor networks, using IEEE 1451 standardization, increases the interoperability of low-power smart sensor devices in IP networks. This paper explains the design and implementation of IPv6 over Low power Wireless Personal Area Networks (6loWPAN) and it uses the IEEE 1451 standard over IEEE 802.15.4 sensor networks. We propose an application of API IEEE 1451 that uses web services to transmit IEEE 1451 commands between Network Capable Application Processor (NCAP) and Wireless Transducer Interface Module (WTIM) using the client-server architecture. In addition the design of 6loWPAN Physical Transducer Electronic Datasheet (PHYTEDS) IEEE 1451.5 is explained. All TEDS were analyzed in terms of memory size. Each IEEE 1451 command is encapsulated in an UDP socket to establish NCAP-to-WTIM communication in an environmental monitoring application.

Wireless technologies in the LAN environment are becoming increasingly important. The IEEE 802.11 is the most mature technology for Wireless Local Area Networks (WLANs). The limited bandwidth and the finite battery power of mobile computers represent one of the greatest limitations of current WLANs. In this paper, we deeply investigate the efficiency and the energy consumption of MAC protocols that can be described with a p-persistent CSMA model. As already shown in the literature, the IEEE 802.11 protocol performance can be studied using a p-persistent CSMA model [12]. For this class of protocols, in the paper, we define an analytical framework to study the theoretical performance bounds from the throughput and the energy consumption standpoint. Specifically, we derive the p values (i.e., the average size of the contention window in the IEEE 802.11 protocol [12]) that maximizes the throughput, pCopt, and minimizes the energy consumption, pEopt. By providing analytical closed formulas for the optimal p values, we discuss the trade-off between efficiency and energy consumption. Specifically, we show that power saving and throughput maximization can be jointly achieved. Our analytical formulas indicate that the optimal p values depend on the network configuration, i.e., number of active stations and length of the messages transmitted on the channel. As network configurations dynamically change, the optimal p values must be dynamically updated. In this paper, we propose and evaluate a simple but effective feedback-based distributed algorithm for tuning the p parameter to the optimal values, i.e., pEopt and pCopt. The performance of the p-persistent IEEE 802.11 protocol, enhanced with our algorithm, are extensively investigated by simulation. Our results indicate that the enhanced p-persistent IEEE 802.11 protocol is very close to the theoretical bounds both in steady-state and in transient conditions.

The mobile free-space optical channel mainly suffers from relatively long link outages, produced by short-term blockings of the line-of-sight (obstacles, clouds), pointing- and tracking-errors or deep signal-fades caused by index of refraction turbulence effects. This paper discusses the applicability of commonly used communication protocols like UDP, TCP, ARQ and the SCPS-TP from the Space Communications Protocol Standards (SCPS) in various scenarios. The performance of the protocols in the selected scenarios is evaluated using the simulation software OMNeT++. The simulations are based on channel measurements from the three FSO demonstrations FASOLT (61 km Ground - Ground link), KIODO (LEO satellite downlink), and ATENAA (land-mobile link) and from ongoing measurements at the German Aerospace Center (DLR) (short-range Ground - Ground) as part of the MINERVAA project. Based on the simulation results, recommendations for protocols in free-space optical communication scenarios are given.

Header compression gains interest with the increasing number of short packets in the Internet, where payload length is small compared to the protocol stack header length. Compression can be applied to the whole protocol stack at once, which is referred to as "monolithic profiles" or can treat individual protocol headers separately, which is referred to as "distributed profiles". In recent ROHC activity, monolithic profiles were preferred due to the domination of RTP/UDP/IPv4 packets in the VoIP area. Considering recent development in the field of transport and network protocols, the distributed profile approach becomes of interest. In this paper, distributed profiles are proposed. Compression efficiency using monolithic and distributed profiles was tested and compared on five TCP/IP, ten RTP/UDP/IP, and five SCTP/IP flows. Monolithic profiles have generally shown somewhat better efficiency, while standalone profiles displayed better robustness when the compressor had to switch to the less efficient operating mode.

The number of personal computers (PCs) in Internet based information systems has been rapidly increasing during the last few years. Designers are trying to improve the performance by choosing the appropriate hardware and software components of PCs that are running Internet based information systems. However, little research has been done to find how different hardware and software components of PCs affect the performance of the two most commonly used protocols for transferring data on Internet today, TCP and UDP. This paper compares data transmission speed for three different operating systems: Windows 95, Windows NT 4.0 Workstation and Linux 2.1.132. Three different hardware configurations based on Intel 486 DX2, Intel Pentium, and Intel Celeron A processors are also compared. Finally, we show how data packet size affects the communication speed

International audience; This work is devoted to the remote feedback control of a linear process with "Internet in the loop". In such a networked control situation, variable and unpredictable delays arise, which may decrease the global performance and, in the extreme, destabilize the system. Our aim is to obtain the best performance (here, the exponential stability rate) despite the variation of the network QoS (quality of service). The considered application is based on a Master-Slave structure. The Slave is a light mobile robot, that receives control data and sends its sampled output (position) via a UDP protocol (indeed, packet re-emission of an old output sample is not needed). A Master computer realizes the remote control, the design of which is based on a remote observer achieving a state prediction of the Slave despite the variable delays and possible packet losses. Using time-stamped packets, the Master also detects the network QoS by estimating the variable time delays. It then uses this information so to adapt its observer/controller gains and guarantee the best possible decay rate. The design of this gain scheduling strategy relies on Lyapunov-Krasovskii functionals with an LMI optimization. Experimental results are provided.

Significant progress has been made towards making ad hoc networks secure and DoS resilient. However, little attention has been focused on quantifying DoS resilience: Do ad hoc networks have sufficiently redundant paths and counter-DoS mechanisms to make DoS attacks largely ineffective? Or are there attack and system factors that can lead to devastating effects? In this paper, we design and study DoS attacks in order to assess the damage that difficult-to-detect attackers can cause. The first attack we study, called the JellyFish attack, is targeted against closed-loop flows such as TCP; although protocol compliant, it has devastating effects. The second is the Black Hole attack, which has effects similar to the JellyFish, but on open-loop flows. We quantify via simulations and analytical modeling the scalability of DoS attacks as a function of key performance parameters such as mobility, system size, node density, and counter-DoS strategy. One perhaps surprising result is that such DoS attacks can increase the capacity of ad hoc networks, as they starve multi-hop flows and only allow one-hop communication, a capacity-maximizing, yet clearly undesirable situation.