Retransmission Timeout Research Articles

ORIT: A Transport Layer Protocol Design for Underwater DTN Sensor Networks

Research challenges have focused on underwater acoustic sensor networks characterized by long propagation delay, narrow bandwidth, and frequently disconnected interruption, among others, which can be viewed as delay/disruption tolerant networks (DTNs). However, limited research has been conducted on goodput performance considering the total data packets transmitted in the channel, which is referred to as the remove redundant goodput (RRG) performance of underwater DTN sensor networks. In this paper, we propose a transport layer protocol, called optimal retransmission timeout (RTO) interval stop-and-wait transmission (ORIT), used in underwater DTN sensor networks. In most general transport layer protocols, the RTO timer is set to longer than the RTT to avoid pseudo-retransmissions. However, great network latency could be introduced by applying such a mechanism in underwater communication networks. In ORIT, we propose an RTO optimization algorithm to maximize the RRG performance of the network by reducing the RTO timer. Meanwhile, we adopt the interval stop-and-wait transmission mechanism to avoid data pseudo-retransmissions caused by setting the RTO timer shorter than the RTT in narrow acoustic channels. Through adopting the RTO timer, the ORIT can achieve the best RRG performance under an RTO timer, which we call the optimal RTO timer. We compare the ORIT with other transport layer protocols in the DTN network. The results show that the ORIT with the optimal RTO timer can shorten the long propagation delay and effectively increase the data delivery rate in the underwater DTN sensor networks.

Adaptive Control of Congestion in Tough Wireless Environments Using DCM+ Algorithm

The aim of this paper is to present DCM+, a new congestion control protocol for data networks. It stands for Dynamic Congestion control for Mobile networks. New metrics have been newly invented and introduced like normalized advancing index (NAI) and complete transmission time (CTT). The simulations are done for a simple single-hop-topology (sender-router-receiver). The outcomes of this protocol are excellent and, in most cases, better than other approaches. The excellent properties of our proposed protocol were possible through tracking the available slow-start threshold. We achieved performance improvement, minimized end-to-end delay and large reduction in transmission time. DCM+ was able to combine many advantages at same time of the protocols NewReno and Westwood+. The results show, that DCM+ is extremely adequate for different types of networks. Feedback as main principle of control theory was used to control the congestion in the network. The parameters Round-Trip-Time (RTT) and Retransmission Timeout (RTO) are used as feedback signals to adjust the next congestion window (cwnd).

Low-High Burst: A Double Potency Varying-RTT Based Full-Buffer Shrew Attack Model

The full-buffer Shrew (FB-Shrew) denial of service (DoS) attack is a variant of the classic Shrew attack that exploits the congestion control mechanism of transmission control protocol (TCP). Here, an attacker sends a high-rate burst of attack packets only after the router buffer is filled with TCP packets, causing the router to drop legitimate packets, and forcing the retransmission of TCP packets. As such, an FB-Shrew attack can cause maximum damage with minimum resources. In this paper, we challenge an assumption of constant round trip time adopted in the original FB-Shrew model. As a result, this model fails to achieve its expected attack effect. In response, we analyze the TCP congestion window and queue behaviors to develop two low-high burst models for maximizing the potency of the FB-Shrew attack. Model 1 is designed to achieve the attack effect expected of the original model. Then, the attack potency of Model 1 is enhanced by simply adjusting the starting time of the attack burst to form Model 2. Mode 1 only exploits the retransmission timeout (RTO) mechanism. Model 2 takes advantage of both the RTO mechanism and the fast retransmission mechanism. In this way, Model 2 further slows down the growth of the congestion window and extends the attack period. A combination of theoretical analyses and simulations are adopted to first validate the proper functioning and effectiveness of the two models for a standard network configuration, and then we assess their attack performances with variations in different network parameters. Our performance assessment demonstrates that one attack unit of Model 2 damages almost twice the number of TCP units as one attack unit of Model 1, which represents an increase in attack potency of nearly 200 percent. The present study provides an expanded basis to explore FB-Shrew attack patterns that may be utilized by attackers. Moreover, the damage that could be inflicted by such attack and the extent to which defense strategies are capable of mitigating the attack's impact could be assessed more precisely by defenders.

Reliable Middleware for Wireless Sensor-Actuator Networks

Many important and critical applications use wireless sensor/actuator networks (WSAN). These applications are spanning widely that range in several environments, including industrial, commercial, and residential. Most of these applications need a certain level of real-time communication in addition to reliable data delivery service. Data distribution service (DDS) is a known standard for supporting real-time distributed systems based on the publish/subscribe model. The DDS specification offers two disparate quality-of-service levels of data reliability, namely: best-effort and fully-reliable. TinyDDS is a lightweight and partial porting of DDS middleware to sensor-based platforms, specifically for platforms with limited resources. However, TinyDDS in its current form lacks the reliability support for data delivery. In this paper, we extended the DDS data reliability service and integrated it into TinyDDS, which resulted in Reliable TinyDDS. Moreover, we provide a prototype and comprehensive performance evaluation of the reliability functions taking into account: number of hops, number of publishers, and several other network parameters. The achieved results indicate that reliable data delivery in real-time for WSAN is possible with optimized system parameters, such as retransmission time-out value of 400ms and number of hops not exceeding 10 for an end-to-end delay ranging from 10 to 100s of milliseconds.

Comparison of CoAP and CoCoA Congestion Control Mechanisms in Grid Network Topologies

Nesnelerin İnterneti (IoT) geleceğin İnternet’inin bir vizyonudur. IoT cihazlarının sınırlı kaynakları nedeniyle yeni nesil protokoller ve algoritmalar geliştirilmekte ve standartlaştırılmaktadır. Kısıtlı Uygulama Protokolü (CoAP), uygulama katmanı iletişimi için Internet Mühendisliği Görev Gurubu (IETF) tarafından tasarlanmıştır. CoAP, ağ içinde tıkanıklığı karşılamayan basit bir taşıma katmanı protokolü olan Kullanıcı Datagram Protokolü (UDP) üzerine kurulmuştur. Bununla birlikte, IoT ağlarında tıkanıklık olayı da büyük bir sorundur. Bu nedenle, çekirdek CoAP spesifikasyonu, ikili üstel geri çekilme (BEB) ile yeniden iletim zaman aşımına (RTO) dayalı temel bir CoAP tıkanıklık kontrolü (CC) mekanizması sunar. Mevcut CoAP CC, ağ koşullarına duyarsızdır. Bu nedenle, mevcut CoAP CC'yi geliştirmek için IETF CoRE çalışma grubu tarafından taslak bir spesifikasyonda tanımlanan CoAP Simple Congestion Control/Advanced (CoCoA) mekanizması standartlaştırılmaktadır. Ancak mevcut CoAP CC ve CoCoA'nın karşılaştırılması literatürde yeterince araştırılmamıştır. Bu çalışmada, eşzamanlı istemcilerin sayısının değiştirilmesiyle her istemcinin sürekli olarak 1x6, 3x6 ve 5x6 grid ağ topolojilerinde yer alan sunuculara arka arkaya trafik gönderilerek mevcut CoAP CC ve CoCoA'nın performansları iş/zaman oranı (yani istek sayısı/saniye) açısından karşılaştırılmış ve sunulmuştur. Elde edilen sonuçlar, CoCoA'nın bazı senaryolarda mevcut CoAP CC'den iş/zaman oranı açısından her zaman daha iyi olmadığını göstermektedir. Sonuç olarak, yeni CoAP CC mekanizmalarının tasarımı ve geliştirilmesi araştırmaya açıktır.

MPTCP Meets FEC: Supporting Latency-Sensitive Applications Over Heterogeneous Networks

Over the past years, TCP has gone through numerous updates to provide performance enhancement under diverse network conditions. However, with respect to losses, little can be achieved with legacy TCP detection and recovery mechanisms. Both fast retransmission and retransmission timeout take at least one extra round trip time to perform, and this might significantly impact the performance of latency-sensitive applications, especially in lossy or high delay networks. While forward error correction (FEC) is not a new initiative in this direction, the majority of the approaches consider FEC inside the application. In this paper, we design and implement a framework, where FEC is integrated within TCP. Our main goal with this design choice is to enable latency sensitive applications over TCP in high delay and lossy networks, but remaining application agnostic. We further incorporate this design into multipath TCP (MPTCP), where we focus particularly on heterogeneous settings, considering the fact that TCP recovery mechanisms further escalate head-of-line blocking in multipath. We evaluate the performance of the proposed framework and show that such a framework can bring significant benefits compared with legacy TCP and MPTCP for latency-sensitive real application traffic, such as video streaming and web services.

Modeling Optimal Retransmission Timeout Interval for Bundle Protocol

Delay/disruption tolerant networking (DTN) was proposed as a networking architecture for reliable data delivery despite an extremely long propagation delay and frequent/lengthy link disruptions. The challenging problem of mission control and data delivery in deep-space explorations is a typical application scenario of the DTN technology. Reliable data delivery of DTN relies heavily on its core bundle protocol (BP). Performance evaluation and improvement of BP for deep-space communications are presently underway. The setting of the retransmission time-out (RTO) timer of BP is critical for reliable and highly efficient file transfer in a deep-space communication environment. In this paper, we present analytical modeling of an optimal RTO timer interval for the best goodput performance of BP in deep-space communications characterized by a very long signal propagation delay and lossy data links. A model is developed to compute the RTO timer interval that will result in the best goodput performance of BP normalized with respect to the total data load transmitted in order to achieve successful delivery of an entire file. Experimental validation using a PC-based testbed indicates that the RTO timer interval indicated by the model achieves the best normalized goodput performance of BP. The model predicts performance in all the experimented scenarios.

FJADA: Friendship Based JellyFish Attack Detection Algorithm for Mobile Ad Hoc Networks

TCP and UDP are considered the most popular and well known transport layer protocols to facilitate the end to end communication between two nodes in the network. TCP is used as the transport layer protocol in packet delivery and error sensitive applications, where packet loss cannot be compromised. However, low-rate TCP targeted Denial of Service (DoS) attacks exploit the retransmission timeout and congestion control features of TCP protocol. These low-rate TCP targeted Denial of Service (DoS) attacks are also called JellyFish (JF) attacks. These attacks perform the malicious activities either by delaying, or periodically dropping or mis-ordering the data packets on the route from source to destination node in the network, and cause severe degradation in end-to-end throughput in the network. JellyFish attack is further classified as JF-Delay Variance Attack, JF-Periodic Drop Attack and JF-Reorder Attack based on the type of the malicious activities being performed. JellyFish attack conforms to all existing routing and packet forwarding protocol specifications, and therefore it becomes very difficult to detect its presence in the network. In this paper, a Friendship Based JellyFish Attack Detection Algorithm (FJADA) is presented for Mobile Ad Hoc Networks, where the basic concept of friendship mechanism is added to the existing Direct Trust-based Detection (DTD) algorithm to save the valuable resources of a node in monitoring the activities of its one hop neighbours, through promiscuous mode. FJADA also minimizes the possibility of overestimating the malicious behaviour of innocent nodes due to radio transmission errors, network congestion or packet collisions. The results obtained throughout the simulation experiments clearly show the feasibility and effectiveness of the proposed detection algorithm.

Steady-state throughput discrete model of multipath TCP based on linked increase algorithm

This paper established a discrete model for the steady-state throughput of multipath TCP (MPTCP), which is based on linked increase algorithm (LIA) and is presented to analyse the relationship between subflow performances and throughput capacity under the steady-state bulk transmission of MPTCP data. With consideration of the coupling of subflow congestion windows' changes, the characteristics of subflow in states such as the congestion avoidance, fast recovery timeout retransmission and slow start was analysed. Furthermore, by calculating the expectations of transmitted packet number and transmission duration in a given MPTCP connection, the discrete model of MPTCP steady-state throughput can be established. Simulation results show that the proposed model can achieve the improved accuracy and robustness when predicting the steady-state transmission throughput of MPTCP.

Steady-state throughput discrete model of multipath TCP based on linked increase algorithm

This paper established a discrete model for the steady-state throughput of multipath TCP (MPTCP), which is based on linked increase algorithm (LIA) and is presented to analyse the relationship between subflow performances and throughput capacity under the steady-state bulk transmission of MPTCP data. With consideration of the coupling of subflow congestion windows' changes, the characteristics of subflow in states such as the congestion avoidance, fast recovery timeout retransmission and slow start was analysed. Furthermore, by calculating the expectations of transmitted packet number and transmission duration in a given MPTCP connection, the discrete model of MPTCP steady-state throughput can be established. Simulation results show that the proposed model can achieve the improved accuracy and robustness when predicting the steady-state transmission throughput of MPTCP.

Internet delay forecasting for correlated and uncorrelated scenarios

SummaryMost Internet end‐to‐end communications rely on the transmission control protocol, and transmission control protocol performance depends upon the efficient detection of packet losses and delay estimations. Thus, several retransmission timeout prediction algorithms, which play an important role in the quality of service assurance, have been suggested in the literature. In this paper, we propose a novel forecasting algorithm, which, in contrast to those reported previously, is suitable for both the correlated and the uncorrelated delay scenarios. The proposed algorithm is compared with other methodologies by using standardized delay traces reported in the literature, and it is shown that the proposed algorithm obtains an improved performance with smaller errors than those of current predictors.

Efficient Traffic Engineering Strategies for Improving the Performance of TCP Friendly Rate Control Protocol

Multimedia services will play a prominent role in the next generation of internet. With increasing real time requirements, internet technology has to provide Quality of Service (QoS) for various kinds of real time streaming services. When the bandwidth required exceeds the available network resources, network paths can get congested, which results in a delay in packet delivery and packet loss. This situation leads to the design of new strategies for congestion avoidance and control. One of the popular and appropriate congestion control mechanisms that is useful in transmitting multimedia applications in the transport layer is TCP Friendly Rate Control Protocol (TFRC). However, TFRC still suffers from packet loss and delay due to long distance heavy traffic and network fluctuations. This paper introduces a number of key concerns like enhanced Round Trip Time (RTT) and Retransmission Time Out (RTO) calculations, Enhanced Average Loss Interval (ALI) methods and improved Time to Live (TTL) features are applied to TFRC to enhance the performance of TFRC over wired networks.

Mitigating incast-TCP congestion in data centers with SDN

In data center networks (DCNs), the presence of long-lived TCP flows tends to bloat the switch buffers. As a consequence, short-lived TCP-incast traffic suffers repeated losses that often lead to loss recovery via timeout. Because the minimum retransmission timeout (minRTO) in most TCP implementations is fixed to around 200 ms, interactive applications that often generate short-lived incast traffic tend to suffer unnecessarily long delays waiting for the timeout to elapse. The best and most direct solution to such problem would be to customize the minRTO to match DCNs delays; however, this is not always possible; in particular in public data centers where multiple tenants, with various versions of TCP, co-exist. In this paper, we propose to achieve the same result by using techniques and technologies that are already available in most commodity switches and data centers and that do not interfere with the tenant’s virtual machines or TCP protocol. In this approach, we rely on the programmable nature of SDN switches and design a SDN-based incast congestion control (SICC) framework, that uses a SDN network application in the controller and a shim-layer in the host hypervisor, to mitigate incast congestion. We demonstrate the performance gains of the proposed scheme via real deployment in a small-scale testbed as well as ns2 simulation experiments in networks of various sizes and settings.

Adaptive RTO for handshaking-based MAC protocols in underwater acoustic networks

Underwater acoustic networks (UANs) are attracting interest in recent decades. The unique characteristics of the underwater acoustic channel, such as long propagation delay, delay variance, and high bit error rate, present challenges for the medium access control (MAC) protocol design in UANs. Most existing medium access control protocols ignore the delay variance which prevents the accurate estimation of round trip time (RTT). The expected RTT value can be used to compute the Retransmission Time-Out (RTO) or the waiting time in MAC. The estimation of RTT is also meaningful for Automatic Repeat re-Quest (ARQ) scheme because the system should ensure reliable data transmissions in the presence of high bit error rate in the underwater acoustic channel. By analyzing the impact of RTO on throughput under the effect of delay variance, we conclude that the fixed RTO is inefficient and RTO should be adaptively set to improve the throughput. We present a novel approach of predicting the RTT using a Bayesian dynamic linear model, and then adjust RTO adaptively according to the predicted values. Simulation results show that the predicted values can adapt quickly to the sample RTT values. Under the effect of RTT fluctuations, the Bayesian algorithm offers performance gains in terms of throughput and prediction performance, comparing with Karn’s algorithm. Our study highlights the value of predicting the RTT using Bayesian approach in underwater acoustic networks.

Optimal RTO Timer for Best Transmission Efficiency of DTN Protocol in Deep-Space Vehicle Communications

The delay/disruption-tolerant network (DTN) was proposed as an end-to-end networking architecture for file delivery service in a stressed communication environment. A typical application of DTN technology is for reliable data delivery in deep-space vehicle communications. The main protocol of DTN, i.e., bundle protocol (BP), utilizes a store-and-forward mechanism and a custody transfer option for transmission reliability. However, little work has been done on the performance evaluation of DTN's BP in deep-space communications. In this paper, we present a study of the retransmission timeout (RTO) timer setting for the use of BP for reliable file (or data) transmission over a relay-based deep-space vehicle communication infrastructure characterized by extremely long latency, lossy data links, and highly asymmetric channel rates. Unlike most studies proposed for terrestrial Internet for which the RTO timer is set equal to or longer than the round-trip time (RTT), we propose to set the RTO timer shorter than the RTT and expect that it will increase delivery efficiency per unit of time. We intend to find an RTO timer setting for maximum data delivery performance of BP, which is considered to be an optimal RTO timer, for deep-space missions. For the first time, analytical models are built for delivery performance involving the RTO timer. Using the built models, we tune the RTO timer toward the highest data delivery performance. The models are validated by running text file transfer experiments using a PC-based testbed and tuning the RTO timer toward the best performance of BP. A performance comparison between the optimal RTO timer proposed in this study and the existing commonly used RTO timers is also presented.

Enhancement of congestion control of Constrained Application Protocol/Congestion Control/Advanced for Internet of Things environment

With the wide spread of Internet of Things, efficient communication between the nodes is getting more important. Constrained Application Protocol was developed to accommodate the resource-constrained nodes and low-power communication links. Being an Internet protocol, Constrained Application Protocol must adhere to congestion control, primarily to keep the backbone network stable. An advanced congestion control mechanism for Constrained Application Protocol, called Congestion Control/Advanced, has also been recently developed. In this article, we propose a new round trip time–based adaptive congestion control scheme, which further improves Congestion Control/Advanced by utilizing the retransmission count in estimating the retransmission timeout value and the lower bound in round trip time variation. An experiment is conducted based on Californium Constrained Application Protocol framework and real devices, and the performance is compared with Constrained Application Protocol, Congestion Control/Advanced, and an existing scheme. It reveals that the proposed scheme significantly increases the throughput and rate of successful transactions in comparison with the other schemes. The approach of utilizing the option field of Constrained Application Protocol enables the proposed scheme to be implemented without any conflict with the existing protocol and extra overhead.

Gateway-Assisted Retransmission for Lightweight and Reliable IoT Communications.

Message Queuing Telemetry Transport for Sensor Networks (MQTT-SN) and Constrained Application Protocol (CoAP) are two protocols supporting publish/subscribe models for IoT devices to publish messages to interested subscribers. Retransmission mechanisms are introduced to compensate for the lack of data reliability. If the device does not receive the acknowledgement (ACK) before retransmission timeout (RTO) expires, the device will retransmit data. Setting an appropriate RTO is important because the delay may be large or retransmission may be too frequent when the RTO is inappropriate. We propose a Gateway-assisted CoAP (GaCoAP) to dynamically compute RTO for devices. Simulation models are proposed to investigate the performance of GaCoAP compared with four other methods. The experiment results show that GaCoAP is more suitable for IoT devices.

Smart Experts for Network State Estimation

Several network protocols, services, and applications adjust their operation dynamically based on current network conditions. Consequently, keeping accurate estimates of the network and its performance as it fluctuates over time is critical. For example, both TCP and IEEE 802.11 periodically adapt some of their key operating parameters, namely, the retransmission timeout and the contention window size based on the average round trip time and the number of collisions, respectively. In this paper, we present a novel mechanism to estimate “near-future” network performance based on past network conditions. We call our approach to network performance estimation as smart experts for network state estimation (SENSE). SENSE uses a simple, yet effective, algorithm combining a machine learning method known as fixed-share with exponentially weighted moving average (EWMA). SENSE also introduces novel techniques that improve the predictability of the fixed-share framework without increasing computational complexity. SENSE is thus able to respond to network dynamics at different time scales, i.e., long- and medium-term fluctuations as well as short-lived variations. We evaluate SENSE’s performance using synthetic and real datasets. Our experimental results show that, when compared to fixed-share and EWMA, SENSE yields higher estimation accuracy for all datasets due to its ability to more closely track data fluctuations.

CoAP congestion control for the internet of things

CoAP is a lightweight RESTful application layer protocol devised for the IoT. Operating on top of UDP, CoAP must handle congestion control by itself. The core CoAP specification defines a basic congestion control mechanism, but it is not capable of adapting to network conditions. However, IoT scenarios exhibit significant resource constraints, which pose new challenges on the design of congestion control mechanisms. In this article we present CoCoA, an advanced congestion control mechanism for CoAP being standardized by the Internet Engineering Task Force CoRE working group. CoCoA introduces a novel round-trip time estimation technique, together with a variable backoff factor and aging mechanisms in order to provide dynamic and controlled retransmission timeout adaptation suitable for the peculiarities of IoT communications. We conduct a comparative performance analysis of CoCoA and a variety of alternative algorithms including state-of-the-art mechanisms developed for TCP. The study is based on experiments carried out in real testbeds. Results show that, in contrast to the alternative methods considered, CoCoA consistently outperforms the default CoAP congestion control mechanism in all evaluated scenarios.

A Method Based on RTO and Selective Acknowledgement for Improving SCTP Protocol Performance in Mobile Ad Hoc Networks

With the increasing development of Mobile Ad Hoc Network usage, there will be more need to have a transport protocol with an appropriate throughput in end to end transport. Because of the design nature of TCP protocol for wired Networks, its application in Mobile Ad-hoc Networks causes a reduction in efficiency, performance and throughput.Protocols such as SCTP with sufficient validity and reliability in data transfer are proposed as solution for increasing throughput. However, in order to provide the above quality, sacrifice factors such as Network balance. In the present paper, two optimized transporting algorithm are introduced. These algorithm act based on retransmission timeout control and selective acknowledgement number for transmissions in SCTP protocol. The offered algorithms using implemented NS-2 simulator and throughput improvement and reduction of packet delay time are compared with former protocols.