Reliable Cross-Layer Data Transport Protocol for MANETs

Consistent data delivery in constrained networks such as wireless sensor networks (WSN), which has a significant role in Internet of Things (IoT), is vital due to the high probability of packet loss, not only because of the unreliable channel but also from link and buffer congestions. Thus, a reliable transport protocol should be used. Data caching at intermediate nodes is one way of improving the reliability performance of transport protocols in WSNs. However, it is not yet known up to what extent data caching alone can alleviate congestion in WSNs. This study investigates and analyses how a cache-based transport protocol, that has no congestion control mechanism and has a fixed transmission window, performs under congestion states. The transport protocol, called DTSN, is evaluated under link and buffer congestion states and the optimal performance is determined in terms of goodput, transmission cost and cache hit metrics. The results of our analysis reveal that intermediate caching was able to perform significantly during congestions in WSN. However, the amount of traffic being sent and intermediate node's cache memory should be taken into account. The optimum caching performance during link contentions is reached at higher transmission window and cache size values, while for buffer congestions, it is achieved at lower transmission window but higher cache size values, respectively. These values obtained can guarantee optimum usage of cache while ensuring congestion avoidance. In addition, the correlation that is established can serve as a basis for developing congestion window management for transport protocols in WSN that employ data caching.

We explore the performance of reliable data communication in mobile computing environments. Motion across wireless cell boundaries causes increased delays and packet losses while the network learns how to route data to a host's new location. Reliable transport protocols like TCP interpret these delays and losses as signs of network congestion. They consequently throttle their transmissions, further degrading performance. We quantify this degradation through measurements of protocol behavior in a wireless networking testbed. We show how current TCP implementations introduce unacceptably long pauses in communication during cellular handoffs (800 ms and longer), and propose an end-to-end fast retransmission scheme that can reduce these pauses to levels more suitable for human interaction (200 ms). Our work makes clear the need for reliable transport protocols to differentiate between motion-related and congestion-related packet losses and suggests how to adapt these protocols to perform better in mobile computing environments.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The traditional reliable transport protocols are originally designed for the wired networks, which regard any packet loss as the indication of network congestion and halve their congestion windows to alleviate the traffic overload of network. However, unlike in wired networks, non-congestion losses will severely degrade the performance of traditional transport protocols in wireless networks. Thus some corruption-aware transport protocols have been proposed to overcome the performance degradation caused in the error-prone wireless networks. Unfortunately, the corruption-aware transport protocols cannot work in realistic networks up to now since the corrupted packets will be discarded by the link layer checksum mechanisms before they are delivered to the transport layer. This paper introduces a cross-layer adaptive partial Frame Check Sequence scheme to safely enable the corruption-aware transport protocols in the next generation wireless communications without disabling the link layer 32-bit Cyclic Redundancy Check checksum mechanisms. Simulation results show that the proposed scheme can help the corruption-aware transport protocols to significantly improve their performance compared to that of the existing schemes.

This chapter presents a distributed program that implements the reliable transport service (Chap. 20) over an LRD (loss, reorder, duplication) channel, as illustrated in Fig. 21.1. In computer networking, such a program is referred to as a transport protocol. Following this terminology, we refer to the system at each address as a “tp” system, where “tp” is short for transport protocol. We refer to the messages exchanged between tp users as “data blocks”, and reserve the term “messages” for the messages exchanged between the tp systems; the former would be sent inside the latter.

Pragmatic General Multicast (PGM) is a reliable multicast transport protocol for applications that require ordered or unordered, duplicate-free, multicast data delivery from multiple sources to multiple receivers. PGM guarantees that a receiver in the group either receives all data packets from transmissions and repairs, or is able to detect unrecoverable data packet loss. PGM is

A large number of network services use IP and reliable transport protocols. For applications with constant pressure of data, loss is handled satisfactorily, even if the application is latency sensitive. For applications with data streams consisting of intermittently sent small packets, however, users experience extreme latencies more frequently. Due to the fact that such thin-stream applications are commonly interactive and time-dependent, increased delay may severely reduce the experienced quality of the service. When TCP is used for thin-stream applications, events of highly increased latency are common, caused by the way retransmissions are handled. Other transport protocols that are deployed in the Internet, like SCTP, model their congestion control and reliability on TCP, as do many frameworks that provide reliability on top of unreliable transport. We have tested several application-and transport layer solutions, and based on our findings, we propose sender-side enhancements that reduce the application-layer latency in a manner that is compatible with unmodified receivers running commodity opeating systems like Linux, *BSD, Mac OSX and Windows. We have implemented the mechanisms as modifications to the Linux kernel, both for TCP and SCTP. The mechanisms are dynamically triggered so that they are only active when the kernel identifies the stream as thin. To evaluate the performance of our modifications, we have conducted a wide range of experiments using replayed thin-stream traces captured from real applications as well as artificially generated thin-stream data patterns. From the experiments, effects on latency, redundancy and fairness were evaluated. The analysis of the performed experiments shows great improvements in latency for thin streams when applying the modifications. Surveys where users evaluate their experience of several applications' quality using the modified transport mechanisms confirmed the improvements seen in the statistical analysis. The positive effects of our modifications were shown to be possible without notable effects on fairness for competing streams. We therefore conclude that it is advisable to handle thin streams separately, using our modifications, when transmitting over reliable protocols to reduce retransmission latency.

Wireless networks and systems are an inseparable part of current communications systems and we use them almost every day to connect to the Internet (via local networks or public hot spots) from fixed and mobile devices. Analogous to satellite networks they are based on wireless links characterized higher bit error rates. A higher level of bit errors in a network causes packet losses and together with packet losses due to network congestion these losses degrade overall performance of reliable transport protocols. The Transport control protocol (TCP) is one of the most used transport protocols in the current Internet. TCP based on its original definition manipulated various packet losses in the same way as if they lose due to network congestion. This method of treatment is not suitable for packet losses due to link bit errors and degrades the performance of TCP. In this paper, we present a modification of TCP (Sni2Wi-TCP) we proposed. In order to increase TCP performance, we integrated a selective negative acknowledgement as well as a loss determination algorithm to classify types of losses.

In this paper we propose a transport connection model managed by reliable transport protocol with forward error correction (FEC) in the modes of selective and group reject in the form of a discrete-time Markov chain. It takes into account the influence on the transport connection throughput by protocol parameters (window size and acknowledge time-out duration), error level in the communication channels of the data transmission path, round-trip delay, and forward error correction process parameters. We assessed the benefits of the transport protocol with FEC over the classic transport protocol in the multidimensional feature space of influencing variable values.

Existing works have approached the problem of reliable transport in ad hoc networks by proposing mechanisms to improve TCP's performance over such networks, In this paper, we show through detailed arguments and simulations that several of the design elements in TCP are fundamentally inappropriate for the unique characteristics of ad hoc networks. Given that ad hoc networks are typically stand-alone, we approach the problem of reliable transport from the perspective that it is justifiable to develop an entirely new transport protocol that is not a variant of TCP. Toward this end, we present a new reliable transport layer protocol for ad hoc networks called ATP (ad hoc transport protocol). We show through ns2-based simulations that ATP outperforms default TCP as well as TCP-ELFN and ATCP.

A lot of research on mobile ad hoc networks has focused on the development of routing and transport protocols. Specifically, this research is focused on the performance of TCP over wireless mobile ad hoc networks. Reliable transport protocols such as TCP are tuned to perform well in traditional networks where packet losses occur mostly due to congestion. However, networks in wireless links perform poorly and suffer from losses due to reasons such as bit error and handoffs. TCP responds to all losses by invoking congestion control and avoidance algorithms resulting in degraded end-to-end performance in wireless systems. The paper sets out the basis for research into the design and development of a new algorithm that is integrated with Mobile IPv6 in order to be implemented in future needs, and thus improve the performance of TCP in such networks. It is proposed to use OMNET++ as the simulation tool to compare the performance of TCP using different approaches with that of the general TCP.

TCP as a reliable transport protocol is tuned to operate efficiently within traditional networks. Within wireless communication scenarios, TCP's congestion avoidance mechanism is falsely triggered by higher bit error probabilities of wireless links and disruptions due to handoffs within cellular communication networks. To separate wired and wireless subpaths of a hybrid communication path the indirect transport protocol model has been introduced. It subdivides the end-to-end transport connection into several subconnections, operating over wired subpaths and over wireless subpaths. Thus, the negative effects of the wireless subpath do not influence the transport connection operating over the wired part of the network. Interconnection of transport connections is realized by so called transport gateways. Due to the potential mobility of wireless attached stations, the migration of transport gateways to network nodes located nearby the current location of the mobile stations is needed. The migration approach presented by Bakre and Badrinath (1995) interrupts transport communication by up to 1.4 seconds. Our approach reduces communication pauses to 75 milliseconds. This is achieved by the so called delayed migration approach, that enables transport layer communication while state information of the transport protocol is transferred to the new gateway. To support the delayed migration approach modifications of the Mobile IP proposal are required. These modifications and performance measurements are presented in this paper.

This work presents new experimental results examining the loss tolerant unicast congestion control behavior of the NACK-Oriented Reliable Multicast (NORM) transport protocol documented initially as Internet Proposed Standard, Request for Comments (RFC) 5740. While RFC 5740 specifies a reliable multicast UDP-based transport protocol, NORM also has the ability to provide loss tolerant UDP unicast reliable transport that is well-suited for lossy wireless environments where protocols like TCP may not perform well. In addition, we introduce the design and use of a unicast SOCKS proxy for the NORM protocol called the NACK-Oriented Proxy (NORP) and validate the results of NORP performance against other NORM unicast experimental results. The availability of NORP will reduce the transition risk and improve the use of NORM unicast capabilities by not requiring end system application modifications. Our results examine a number of unicast congestion control variants of the NORM protocol, including an explicit congestion notification (ECN) mode, within an emulated lossy link modeled network environment. We include COTS hardware routing and radio-to-router interface (R2RI) within the test environment to examine and validate the use and performance of ECN-based packet marking and improved cross-layer flow control when available. The initial experiments demonstrate the significant advantage of using ECN-based assistance within error-prone wireless environments. We also show increased performance of an additional loss tolerant mode that does not require ECN infrastructure support. Coexistent transport fairness results show that NORM unicast modes are friendly to both inter-protocol flows (e.g., TCP flows coexisting) and to intra-protocol flows (e.g., Other NORM flows coexisting). We conclude by summarizing findings and discussing future work planned.

We analyze the maximum throughput that known classes of reliable multicast transport protocols can attain. A new taxonomy of reliable multicast transport protocols is introduced based on the premise that the mechanisms used to release data at the source after correct delivery should be decoupled from the mechanisms used to pace the transmission of data and to effect error recovery. Receiver-initiated protocols, which are based entirely on negative acknowledgments (NAKS) sent from the receivers to the sender, have been proposed to avoid the implosion of acknowledgements (ACKS) to the source. However, these protocols are shown to require infinite buffers in order to prevent deadlocks. Two other solutions to the ACK-implosion problem are tree-based protocols and ring-based protocols. The first organize the receivers in a tree and send ACKS along the tree; the latter send ACKS to the sender along a ring of receivers. These two classes of protocols are shown to operate correctly with finite buffers. It is shown that tree-based protocols constitute the most scalable class of all reliable multicast protocols proposed to date.

The shift to network centric warfare highlights the deficiencies of existing reliable transport protocols in tactical network environments. Existing transports are designed upon a set of assumptions that are violated by noisy, wireless tactical networks where end-to-end encryption and authentication must be maintained. Protocols such as TCP that are designed for low-corruptive-loss environments provide abysmal performance when deployed in tactical network environments. TCP adaptations that address corruptive loss rates generally violate tactical-network security requirements. As part of a DARPA-funded effort to dramatically improve reliable-transport performance in tactical network environments, Architecture Technology Corporation (ATC) has analyzed the tactical network environment and has examined the behavior of various reliable transport protocols within such environments.

Transport layer reneging