An ECN Approach to Congestion Control Mechanisms in Mobile Ad hoc Networks

Explicit congestion notification (ECN) mechanism capture network congestion status by using feedback based mechanism.  It determines the level of congestion more accurate than pure end-to-end schemes with an ECN-like marking scheme. The purpose of the ECN bit is to notify TCP sources of an incipient congestion and mark packets before losses occur. ECN is a binary indicator which does not reflect the congestion level and its convergence speed is relatively low due to insufficient congestion feedback. In this paper, we proposed a novel approach to handle congestion in MANETs. The same is tried to resolve by using concept of explicit congestion Notification (ECN) bits which is an extension to transmission control protocol (TCP). It allows end to end notification of network congestion without dropping packets which is done conventionally in TCP/IP networks with a bit difference of additional bit. This additional bit allows more flexibility to adjust window size to handle congestion, in comparison to a single ECN bit. Aforesaid concept is tries to simulate and performance of the same has been evaluated with appropriate environment and parameters.   Keywords: Explicit Congestion Notification (ECN), Mobile ad hoc Networks (MANET), Congestion control, Congestion window Transmission Control Protocol (TCP)

Network coding meets TCP

We propose a mechanism that incorporates network coding into TCP with only minor changes to the protocol stack, thereby allowing incremental deployment. In our scheme, the source transmits random linear combinations of packets currently in the congestion window. At the heart of our scheme is a new interpretation of ACKs - the sink acknowledges every degree of freedom (i.e., a linear combination that reveals one unit of new information) even if it does not reveal an original packet immediately. Such ACKs enable a TCP-like sliding-window approach to network coding. Our scheme has the nice property that packet losses are essentially masked from the congestion control algorithm. Our algorithm therefore reacts to packet drops in a smooth manner, resulting in a novel and effective approach for congestion control over networks involving lossy links such as wireless links. Our experiments show that our algorithm achieves higher throughput compared to TCP in the presence of lossy wireless links. We also establish the soundness and fairness properties of our algorithm.Comment: 9 pages, 9 figures, submitted to IEEE INFOCOM 200

TCP-Carson: A loss-event based Adaptive AIMD algorithm for Long-lived Flows

The diversity of network applications over the Internet has propelled researchers to rethink the strategies in the transport layer protocols. Current applications either use UDP without end-to-end congestion control mechanisms or, more commonly, use TCP. TCP continuously probes for bandwidth even at network steady state and thereby causes variation in the transmission rate and losses. This thesis proposes TCP Carson, a modification of the window-scaling approach of TCP Reno to suit long-lived flows using loss-events as indicators of congestion. We analyzed and evaluated TCP Carson using NS-2 over a wide range of test conditions. We show that TCP Carson reduces loss, improves throughput and reduces window-size variance. We believe that this adaptive approach will improve both network and application performance

ECN based Congestion Control for a Software Defined Network

This paper deals with congestion control in a software defined network (SDN) setting. Presently, explicit router schemes, such as Explicit Congestion Notification (ECN), work in conjunction with the TCP protocol to handle congestion in a distributed manner. With the emergence of SDN and centralized control, it is possible to leverage the global view of the network state to make better congestion control decisions. In this work, we explore the advantages of bringing in global information into distributed congestion control. We propose a framework where the controller with its global view of the network actively participates in the congestion control decisions of the end TCP hosts, by setting the ECN bits of IP packets appropriately. Our framework can be deployed very easily without any change to the end node TCPs or the SDN switches. We also show 30x improvement over the TCP Cubic variant and 1.7x improvement over TCP/RED in terms of flow completion times for one implementation of this framework, using the Mininet emulator

Performance enhancement of DCCP TCP - like over long delay link networks

The performance of DCCP TCP-like degrades significantly over long delay link networks.Despite the TCP-like congestion control mechanism follows the TCP SACK, the performance is really affected by the congestion window growth algorithms as employed by Jacobson based TCP variants. In this paper, all the experiments are done using Network Simulator ns-2, and we manipulated the congestion window size drop during congestion avoidance phase to enhance the performance of DCCP TCP-like over long delay link networks. Instead of halving the current congestion window when congestion events are detected, the reduction of current congestion window drop has been shown to improve the DCCP TCP-like throughput with minimal drop packet percentage

TCP-Aware Backpressure Routing and Scheduling

In this work, we explore the performance of backpressure routing and scheduling for TCP flows over wireless networks. TCP and backpressure are not compatible due to a mismatch between the congestion control mechanism of TCP and the queue size based routing and scheduling of the backpressure framework. We propose a TCP-aware backpressure routing and scheduling that takes into account the behavior of TCP flows. TCP-aware backpressure (i) provides throughput optimality guarantees in the Lyapunov optimization framework, (ii) gracefully combines TCP and backpressure without making any changes to the TCP protocol, (iii) improves the throughput of TCP flows significantly, and (iv) provides fairness across competing TCP flows