Selective Acknowledgement Research Articles

A Survey Of Tcp Reno, New Reno And Sack Over Mobile Ad-Hoc Network

Transmission Control Protocol (TCP) is often preferred to be implemented at the transport layer of a Mobile Ad-hoc Network (MANET) because of its wide range of applications, which enjoys the advantage of reliable data transmission in the Internet. However, because of some unique characteristics of MANET, TCP cannot offer reliable services while using e-mail, internet search and file transmission in such a network. The research investigates how well the different versions of TCP respond to various performance differentials when subjected to different network stresses and topology changes, aside from identifying the most efficient and robust TCP version(s) for different MANET scenarios. Among several TCP variants, three types are considered important for the analysis, namely TCP Reno, TCP New Reno and TCP Selective Acknowledgment (SACK). In most cases, the TCP performance is found in our study to decrease when the node size and mobility rate is increased in the network. There is, however, exception to this. As our simulation results demonstrate, the increases in the node velocity sometimes help the TCP to attain a better performance. The study also reveals that out of the three variants, TCP SACK can adapt relatively well to the changing network sizes while TCP Reno performs most robustly in the presence of different mobility rates within MANET.

Implementation of TCP Retransmitted Packet Loss Recovery using ns-2 Simulator

Transmission control protocol(TCP) widely used as a transport protocol in the Internet includes a loss recovery function that detects and recovers packet losses by retransmissions. The loss recovery function consists of the two algorithms; fast retransmit and fast recovery. There have been researches to avoid nonnecessary retransmission timeouts (RTOs), which leads to selective acknowledgement (SACK) option and limited transmit scheme that are standardized by IETF (Internet Engineering Task Force). Recently, a method that covers the case in which a retransmitted packet is lost again has been propsed. The method, however, is not proved in terms of the additive increase multiplicative decrease (AIMD) principle of TCP congestion control. In this paper, therefore, we analyzed the method in terms of the principle by ns-simulations.

Engineering TCP transmission and retransmission mechanisms for wireless networks

Transmission Control Protocol (TCP) provides mechanisms for reliable data communications. Although it works well in wired networks, it fails to offer satisfactory performance in lossy and wireless environments. And in the multi-hop wireless infrastructure, packet delivery suffers high cumulative loss rate if traveling over multiple wireless hops. The Selective acknowledgment (SACK) is one header option that might be used to combat segment corruptions in air channels. In this paper, an alternative set of flow control mechanisms is proposed to handle high packet loss rate in a wireless medium. Using a measurement-based mechanism, sustainable segment delivery is achievable through a novel size-reduction method. Multiple segment retransmission mechanisms are introduced to reduce successive timeout events. One single byte loss is sufficient to waste all other bytes in a file received at a destination. That is, a good TCP flow control mechanism should provide a high successful file transmission completion rate, and this is set as our design goal. Through thorough simulations, our proposed multi-segment retransmission designs perform with higher successful file transfer rate and fewer timeout events than NewReno and SACK under a wide range of packet loss probabilities.

Routing Misbehavior Detection in MANETs Using 2ACK

This paper proposes routing misbehavior detection in MANETs using 2ACK scheme. Routing protocols for MANETs are designed based on the assumption that all participating nodes are fully cooperative. However, due to the open structure and scarcely available battery-based energy, node misbehavior may exist. In the existing system, there is a possibility that when a sender chooses anintermediate link to send some message to a destination, the intermediate link may pose problems such as, the intermediate node may not forward the packets to destination, it may take very long time to send packets or it may modify the contents of the packet. In MANETs, as there is no retransmission of packets once it is sent, care must be taken not to loose packets. We have analyzed and evaluated a technique, termed 2ACK scheme to detect and mitigate the effect of such routing misbehavior in MANETs environment. It is based on a simple 2-hop acknowledgment packet that is sent back by the receiver of the next-hop link. 2ACK transmission takes place for only a fraction of data packets, but not for all. Such a selective acknowledgment is intended to reduce the additional routing overhead caused by the 2ACK scheme. Our contribution in this paper is that, we have embedded some security aspects with 2ACK to check confidentiality of the message by verifying the original hash code with the hash code generated at the destination. If 2ACK is not received within the wait time or the hash code of the message is changed then the node to next hop link of sender is declared as the misbehaving link. We simulated the routing misbehavior detection using 2ACK scheme to test the operation scheme in terms of performance parameters.

Appropriate SACK Handling for Temporary Disconnections in a Wireless Multi-Homed Environment

In this letter, we describe inappropriate SACK (Selective Acknowledgement) handling in SCTP multi-homed environment, and propose a simple modification. The main idea of the modification is that a sender does not increase the congestion control window size of a primary path when availability of the path is ambiguous. Through simulation, we show that the performance is much improved with this simple modification compared to standard SCTP.

Throughput analysis of Non-Renegable Selective Acknowledgments (NR-SACKs) for SCTP

Preliminary work introduced Non-Renegable Selective Acknowledgments (NR-SACKs) and showed they (i) better utilize a data sender’s memory in both SCTP and CMT, and (ii) improve throughput in CMT. In this paper, we provide the latest specification of NR-SACKs, and extend the investigation of throughput improvements that NR-SACKs can provide. Using ns-2 simulation, for various loss conditions and bandwidth-delay combinations, we show that the throughput observed with NR-SACKs is at least equal and sometimes better than the throughput observed with SACKs. We introduce “region of gain” which defines for a given bandwidth, delay, and send buffer size combination, what range of loss rates results in significant throughput improvement when NR-SACKs are used instead of SACKs. In both SCTP and CMT, NR-SACKs provide greater throughput improvement as the send buffer size decreases, and as end-to-end delay decreases. Provided that the bandwidth-delay product (BDP) ⩾ send buffer size, additional bandwidth does not increase NR-SACKs’ throughput improvements for either SCTP or CMT. For BDPs < send buffer size, the throughput improvement decreases as the BDP decreases.

Performance Analysis of TCP-AFC for Satellite-based Networks

Satellite has been identified as a potential candidate to meet the explosive Internet demand and to evolve the global Internet services. With a view to combat channel errors predominant in satellite based networks, TCP with Adaptive Flow Control and Delayed Fast Recovery (TCP-AFC) has been designed to identify a random loss with the help of selective acknowledgments. TCPAFC has demonstrated significant performance enhancement in error prone environments through simulations and experiments on an active emulated network. In order to substantiate the improvement, we investigate the performance of TCP-AFC in a real environment consisting of a Ku band satellite link, which is more susceptible to atmospheric conditions. This paper focuses on evaluation of TCP-AFC in real life situations having appreciable channel noise and delay. Results of the extensive experiments conducted on a test bed consisting of a symmetric GEO satellite link for different channel conditions, data volume, data type and data traffic are presented in this paper. Analysis of the results reconfirms the compatibility of TCP-AFC in a heterogeneous network besides the performance improvement over a dedicated satellite link .

Dynamic Bandwidth Allocation for QoS Provisioning in IEEE 802.16 Networks with ARQ-SA

In this paper, bandwidth allocation, in terms of distributing available data slots among different users, is studied for QoS provisioning in IEEE 802.16 networks. By considering the automatic repeat request with selective acknowledgement (ARQ-SA) scheme for erroneous wireless channels, a mathematical model is established to theoretically analyze the delay performance of transmitting service data unit (SDU) under a multiuser environment. The analytical results indicate that the delivery delay of the SDU is dominated by the time spent for the first transmission of all its protocol data units (PDUs). Based on this observation, a novel dynamic bandwidth allocation algorithm is proposed and a detailed performance analysis is provided. Simulation results show that the proposed bandwidth allocation algorithm can significantly improve the delay performance of SDUs and ensure the fairness among different users.

Improving TCP/IP Performance over Third-Generation Wireless Networks

As third-generation (3G) wireless networks with high data rate get widely deployed, optimizing the transmission control protocol (TCP) performance over these networks would have a broad and significant impact on data application performance. In this paper, we make two main contributions. First, one of the biggest challenges in optimizing the TCP performance over the 3G wireless networks is adapting to the significant delay and rate variations over the wireless channel. We present window regulator algorithms that use the receiver window field in the acknowledgment (ACK) packets to convey the instantaneous wireless channel conditions to the TCP source and an ACK buffer to absorb the channel variations, thereby maximizing long-lived TCP performance. It improves the performance of TCP selective ACK (SACK) by up to 100 percent over a simple drop-tail policy, with small buffer sizes at the congested router. Second, we present a wireless channel and TCP-aware scheduling and buffer sharing algorithm that reduces the latency of short flows while still exploiting user diversity for a wide range of user and traffic mix.

A comparative investigation of acknowledgment mechanisms for data transport in space internet

As the Internet is changing the world dramatically, an initiative is being proposed within NASA and in the military to expand the Internet into space and for network-centric warfare using network protocols. An end-to-end effective data transport protocol is critical to the reliable transfer of information in space and for a battlefield environment. Consequently, a reliable and efficient acknowledgment mechanism is required to accommodate these unreliable communication conditions. In this article we conduct a comparative investigation of existing data transport acknowledgment mechanisms for possible adoption in the unreliable environment of space or a similarly stressed communication environment. We also introduce the selective negative acknowledgment (SNACK), which is designed as a reliable retransmission mechanism for space and stressed tactical communications, followed by a brief performance evaluation of the effectiveness of SNACK compared to the standard SACK mechanism.

Design, implementation and evaluation of a QoS-aware transport protocol

In the context of a reconfigurable transport protocol framework, we propose a QoS-aware Transport Protocol (QSTP), specifically designed to operate over QoS-enabled networks with bandwidth guarantee. QSTP combines QoS-aware TFRC congestion control mechanism, which takes into account the network-level bandwidth reservations, with a Selective ACKnowledgment (SACK) mechanism in order to provide a QoS-aware transport service that fill the gap between QoS enabled network services and QoS constraint applications. We have developed a prototype of this protocol in the user-space and conducted a large range of measurements to evaluate this proposal under various network conditions. Our results show that QSTP allows applications to reach their negotiated QoS over bandwidth guaranteed networks, such as DiffServ/AF network, where TCP fails. This protocol appears to be the first reliable protocol especially designed for QoS network architectures with bandwidth guarantee.

Improving TCP performance with bandwidth estimation and selective negative acknowledgment in wireless networks

This paper investigates the performance of the transmission control protocol (TCP) transport protocol over IEEE 802.11 infrastructure based wireless networks. A wireless link is generally characterized by high transmission errors, random interference and a varying latency. The erratic packet losses usually lead to a curbing of the flow of segments on the TCP connection and thus limit TCP's performance. This paper examines the impact of the lossy nature of IEEE 802.11 wireless networks on the TCP performance and proposes a scheme to improve the performance of TCP over wireless links. A negative acknowledgment scheme, selective negative acknowledgment (SNACK), is applied on TCP over wireless networks and a series of ns-2 simulations are performed to compare its performance against that of other TCP schemes. The simulation results confirm that SNACK and its proposed enhancement SNACK-S, which incorporates a bandwidth estimation model at the sender, outperform conventional TCP implementations in 802.11 wireless networks.

The handover control mechanism for multi-path transmission using Stream Control Transmission Protocol (SCTP)

With the rapid advance of wireless networking technologies, end-host networking devices have been equipped with various network interfaces. Thus, it becomes possible for a wireless mobile host to improve its transmission efficiency by transmitting data through multiple network interfaces at the same time. In this paper, we focus on the mobility issues of SCTP multi-path transmission. M 2-SCTP (Mobile Multipath – Stream Control Transmission Protocol) is proposed to allow a host to perform (multi-)path handover when multi-path transmission is adopted in wireless mobile networks. Relevant mobility issues of M 2-SCTP are also investigated. We define three conditions under which the M 2-SCTP host can select the paths for multi-path data transmission. Since the paths used in M 2-SCTP may differ at each time paths are re-selected, the path handover problem must be tackled. Three concerns related to path handover that are addressed and resolved in this paper include (1) spurious retransmissions due to failed SACK (Selective Acknowledgement) transmission at the old path, (2) retransmissions of data lost before path handover and unnecessary CWND (Congestion Window) reductions, and (3) the reordering problem due to path handover. Based on the mechanisms devised to solve the path handover problem, the M 2-SCTP multi-path handover mechanism is also devised. Finally, a scheme that adopts the DDNS (Dynamic DNS) technique is proposed to resolve the locating issue of an M 2-SCTP host.

Formal Validation of the Safety Property of Sack Protocol Using Theorem Proving Technique

This paper demonstrates the formal validation process of safety properties of Selective ACKnowledgment (SACK) protocol. SACK is a complex communication protocol as it is used in various types of distributed computer systems and networks. This acknowledgment mechanism is used with sliding window protocol that allows the receiver to acknowledge packets received out of order, but within the correct sliding window. One of the critical property of SACK is its' safety property. In order to validate this property formally by using the Z/Eves theorem prover, we specify the SACK protocol using Z formal specification language. By using theorem prover tool, it helps to reduce time, energy and mistake than in relatively manual theorem proving which can be tedious and error-prone task.

On TCP performance over asymmetric satellite links with real-time constraints

Real-time transmission over asymmetric satellite IP links is challenging, since satellite systems commonly exhibit long propagation delays, while bandwidth asymmetry often enforces a variable and infrequent rate of acknowledgment packets ( ACKs) across the upstream channel with several undesirable implications. In this context, we formulate an analytical model in order to quantify the impact of satellite systems and link asymmetry on TCP performance and real-time delivery. We emphasize on the effects of asymmetric links, and especially on the implications that cause interruptions in the sending rate, and eventually disturb smooth delivery. Since TCP performance is in part throttled by the rate of arriving ACKs, we additionally investigate the impact of delayed ACKs. Although delayed ACKs occasionally diminish the transmission rate, we uncover notable gains in terms of smoothness and real-time delivery. Furthermore, we demonstrate conclusive performance studies tackling the supportive role of selective acknowledgments ( SACK) and the effect of varying bit error rates. Our simulation results illustrate that most existing end-to-end solutions do not comply with the stringent Quality of Service ( QoS) provisions of time-sensitive applications, resulting in ineffective bandwidth utilization and varying delays in data delivery. Finally, with the absence of a satellite-optimized TCP implementation for real-time transmission, we identify the most prominent end-to-end solutions that manage to alleviate most of the impairments induced by asymmetric satellite links, sustaining a relatively smooth transmission rate.

Formal Specification and Validation of Selective Acknowledgement Protocol using Z/EVES Theorem Prover

Formal Specification and Validation of Selective Acknowledgement Protocol using Z/EVES Theorem Prover

On SCTP multi-homing performance

The Stream Control Transmission Protocol (SCTP) is a general purpose transport protocol featuring multi-homing support, message oriented and more flexible data delivery mechanisms than TCP, and an increased protection against well-known attacks. Originally developed for the transport of Signaling System No. 7 messages, e.g. MTP level 3 user primitives, over IP networks, SCTP has evolved to a general purpose transport protocol with a wide field of applications. With respect to multi-homing, the current SCTP standard uses this feature for network level redundancy only. Therefore we propose and evaluate in this contribution mechanisms for the application-specific optimisation of the SCTP protocol behaviour with respect to its multi-homing capabilities. To satisfy the extremely strict performance requirements for signalling transport, efficient load sharing among all active links is also highly desirable in SCTP scenarios. To this end, we propose a novel, improved load sharing algorithm for SCTP with path based selective acknowledgements which avoids some of the drawbacks of the existing algorithms and achieves an increase in throughput. Results of a comparative simulation study are presented to demonstrate the benefits of our algorithm.

An Extended Model for TCP Loss Recovery Latency with Random Packet Losses

It has been a very important issue to evaluate the performance of transmission control protocol (TCP), and the importance is still growing up because TCP will be deployed more widely in future wireless as well as wireline networks. It is also the reason why there have been a lot of efforts to analyze TCP performance more accurately. Most of these works are focusing on overall TCP end-to-end throughput that is defined as the number of bytes transmitted for a given time period. Even though each TCP's fast recovery strategy should be considered in computation of the exact time period, it has not been considered sufficiently in the existing models. That is, for more detailed performance analysis of a TCP implementation, the fast recovery latency during which lost packets are retransmitted should be considered with its relevant strategy. In this paper, we extend the existing models in order to capture TCP's loss recovery behaviors in detail. On the basis of the model, the loss recovery latency of three TCP implementations can be derived with considering the number of retransmitted packets. In particular, the proposed model differentiates the loss recovery performance of TCP using selective acknowledgement (SACK) option from TCP NewReno. We also verify that the proposed model reflects the precise latency of each TCP's loss recovery by simulations.

Which transmission mechanism is best for space Internet: window-based, rate-based, or a hybrid of the two?

There is an urgent need to find the best congestion-control mechanism for space Internet. This article presents an experimental study of rate-based congestion control, window-based congestion control, and a hybrid of the two in a simulated small-satellite environment using the space-to-ground link simulation (SGLS) testbed. The study is done by examining the throughput performance and transmission behavior of pure rate-control and a variant of each of the window-based transmission control protocol (TCP) selective acknowledgment (TCP-SACK) and TCP-Vegas congestion-control mechanisms, with and without the channel-rate control being hybridized. The study reveals that the traffic-shaping mechanism of a rate-based transmission mechanism is more effective than the bursty flow of window-based mechanisms in error-prone space environments with a long link delay. Pure rate-control is preferable to other mechanisms in space in which channel resource reservation is available. The performance differences arise from their different behaviors in controlling data transmission.

Enhancing TCP performance to persistent packet reordering

In this paper, we propose a simple algorithm to adaptively adjust the value of dupthresh, the duplicate acknowledgement threshold that triggers the transmission control protocol (TCP) fast retransmission algorithm, to improve the TCP performance in a network environment with persistent packet reordering. Our algorithm uses an exponentially weighted moving average (EWMA) and the mean deviation of the lengths of the reordering events reported by a TCP receiver with the duplicate selective acknowledgement (DSACK) extension to estimate the value of dupthresh. We also apply an adaptive upper bound on dupthresh to avoid the retransmission timeout events. In addition, our algorithm includes a mechanism to exponentially reduce dupthresh when the retransmission timer expires. With these mechanisms, our algorithm is capable of converging to and staying at a near-optimal interval of dupthresh. The simulation results show that our algorithm improves the protocol performance significantly with minimal overheads, achieving a greater throughput and fewer false fast retransmissions.