Dynamic weight parameter for the Random Early Detection (RED) in TCP networks

This paper presents the Weighted Random Early Detection (WTRED) strategy for congestion handling in TCP networks. WTRED provides an adjustable weight parameter to increase the sensitivity of the average queue size in RED gateways to the changes in the actual queue size. This modification, over the original RED proposal, helps gateways minimize the mismatch between average and actual queue sizes in router buffers. WTRED is compared with RED and FRED strategies using the NS-2 simulator. The results suggest that WTRED outperforms RED and FRED. Network performance has been measured using throughput, link utilization, packet loss and delay

Enhanced Queue Management Mechanism for Differentiated Services Networks

In the Internet, it is supposed that all connections are treated equally in the network. Due to the limitation of network resources are limited, providing guarantees on performance measures imposes declining new connections if resources are not available. Assigning network resources to connections according to their classes requires differentiating between the connection classes. For this reason, the Differentiated Services (DiffServ) has been proposed. Many of the QoS mechanisms have been developed which allow different services carried by the Internet to co-exist. Many of these mechanisms were both complex and failed to scale to meet the demands of the Internet. MRED is the common mechanism used in DifJServ routers. It suflers from large queue length variation and untimely congestion detection and notification. These consequences cause performance degradation due to high queuing delays and high packet loss. In this project, enhanced version of MRED is developed to improve the performance of Diffserv networks that use TCP as the transport layer protocol. Enhanced MRED includes average packet arrival rate when computing the packet drop probability. Enhanced MRED showed a good pedonnance compared to that of MRED, in term of fast congestion detection and notification. The limitation of the new mechanism is that it works only with responsive connections which play a big role in avoiding and controlling the congestion. The major contribution of this project is to provide an improved queue management mechanism for Diffserv networks that responds to congestion more quickly, delivers congestion notification timers, and controls the queue length directly to congestion which results in minimizing queue length variation. All these would help improve the DlffServ networks performance

The Uniformization Process of the Fast Congestion Notification (FN)

Fast Congestion Notification (FN) is one of the proactive queue management mechanisms that practices congestion avoidance to help avoid the beginning of congestion by marking or dropping packets before the routers queue gets full; and exercises congestion control, when congestion avoidance fails, by increasing the rate of packet marking or dropping. Technically, FN avoids the queue overflows by controlling the instantaneous queue size below the optimal queue size, and control congestion by keeping the average arrival rate close to the outgoing link capacity. Upon arrival of each packet, FN uses the instantaneous queue size and the average arrival rate to calculate the packet marking or dropping probability. FN marks or drops packets at fairly regular intervals to avoid long intermarking intervals and clustered packet marks or drops. Too many marked or dropped packets close together can cause global synchronization, and also too long packet intermarking times between marked or dropped packets can cause large queue sizes and congestion. This paper shows how FN controls the queue size, avoids congestion, and reduces global synchronization by uniformizing marked or dropped packet intervals.Comment: 5 Pages IEEE format, International Journal of Computer Science and Information Security, IJCSIS 2009, ISSN 1947 5500,Impact Factor 0.423, http://sites.google.com/site/ijcsis

Priority checking RED for improving QoS in IPv6

This paper presents a priority checking random early detection (PC-RED) gateway for ensuring the quality of service (QoS) of high priority dataflow in IPv6 networks. A bit in the IP header is used in PC-RED to label the packet with the current status of the QoS that the dataflow is being treated in. The status of the QoS is determined by the difference between the packet average-dropping rate and the fixed desired limit dropping rate of the dataflow. PC-RED would perform dissimilarly to every dataflow corresponding to the different QoS status throughout congestions. PC-RED has been modeled and the parameter setting has been studied. Simulations of a TCP/IP network are used to illustrate how PC-RED affects the transfer of dataflow. The result shows remarkable contrast between the high-priority and non-priority dataflow throughput under PC- RED mechanism

Modeling the interdependency of low-priority congestion control and active queue management

Recently, a negative interplay has been shown to arise when scheduling/AQM techniques and low-priority congestion control protocols are used together: namely, AQM resets the relative level of priority among congestion control protocols. This work explores this issue by (i) studying a fluid model that describes system dynamics of heterogeneous congestion control protocols competing on a bottleneck link governed by AQM and (ii) proposing a system level solution able to reinstate priorities among protocols.Comment: 9 page

A Spectrum of TCP-friendly Window-based Congestion Control Algorithms

The increasing diversity of Internet application requirements has spurred recent interest in transport protocols with flexible transmission controls. In window-based congestion control schemes, increase rules determine how to probe available bandwidth, whereas decrease rules determine how to back off when losses due to congestion are detected. The control rules are parameterized so as to ensure that the resulting protocol is TCP-friendly in terms of the relationship between throughput and loss rate. This paper presents a comprehensive study of a new spectrum of window-based congestion controls, which are TCP-friendly as well as TCP-compatible under RED

Combination of GREEN and SHRed AQM for short-lived traffic

The majority of traffic flows dominate Internet traffic is Web interactions where they are short-lived HTTP connections handled by TCP.Short-lived traffic is more sensitive to delay and has small congestion windows cwnds.This paper introduces a new active queue management (AQM) algorithms based on combination of GREEN algorithm and SHRED, to tackle issues on Short-lived flows.Active Queue Management (AQM) refers to a method to enhance congestion control, and to achieve trade off between link utilization and delay. Several example of AQM model is Random Early Detection (RED), Blue and GREEN (Generalized Random Early Evasion Network).RED has the potential to overcome some of the problems such as synchronization of TCP flows. To evaluate the performance of new algorithm, network simulation has been done using NS-2 simulation.This study provides a series of NS-2 experiments to investigate the behavior of new algorithm.The results show improvement on short-lived traffic

A linear packet marking probability function for fast congestion notification (FN)

The efficiency of queue management mechanisms depends on how well their control decisions helps in satisfying their objectives regarding congestion avoidance and control. These decisions are implemented and compelled during the design of the packet mark probability and the mark activation functions. If a packet is dropped / marked rather than being allowed to the buffer, a congestion notification is delivered and the congestion avoidance and control carries on to be applied at the router. If the queue management mechanism realizes the need to apply more aggressive congestion control, the recently arrived packet should be dropped to provide early congestion notification. In this paper, we design a new packet drop probability function with a built-in drop activation function for Fast Congestion Notification (FN) mechanism. This design enables the two control decisions, packet admissions and congestion control directing, to be made along with each other. This permits sending congestion avoidance notification as early as required even if the queue is almost empty, and preventing congestion notification even if the queue is almost full but the arrival rate is controllable, thus the buffer is fully utilized and the congestion is detected properly