International Journal of Computer Networks and Applications

Vincent O. Nyangaresi ¹, Solomon O Ogara ¹, Silvance O. Abeka ¹

Affiliations
1 School of Informatics and Innovative Systems, Jaramogi Oginga Odinga University of Science and Technology, KE

Abstract

In mesh networks, the sender machine is connected to the receiver machine via multiple paths. Efficient transmissions along these paths require proper link choice so as to quickly deliver the packets the destination. Poor link selection can lead to overutilization of some links while the other redundant links remain underutilized. Over-utilized links experience heavy congestions under peak hours. The transmission control protocol (TCP) employs congestion control algorithms to prevent transmitters from overloading the network with data. These algorithms include slow start, congestion avoidance, fast retransmit and fast recovery. The slow start algorithm is utilized during the initial communication phase while congestion avoidance, fast retransmit and fast recovery are reactionary algorithms one packet loss is detected. This paper aimed to analyze the behavior of TCP under these congestion control algorithms in wired mesh networks. The dimensions that were used for this analysis included three way handshake, packet loss, duplicate acknowledgements, segment retransmissions, recovery, I/O plots and time-sequence plots. The objective of this study was to practically understand how the TCP protocol detects and handles network congestions in mesh networks. To achieve this objective, an experimental research design was employed. It involved the practical design of experimental setups that were used to collect data that was analyzed to provide an explanation of the TCP congestion control mechanisms. The results obtained indicate that the TCP first carries out a three handshake before data transmission can take place. It was also observed that the receipt of three duplicate acknowledgements is interpreted by TCP to be packet loss caused by network congestion. Moreover, it was established that TCP initiates fast retransmit and fast recovery when packet loss is detected. The contribution of this paper lies in the fact that it provided a practical understanding of how TCP detects and reacts to mesh network congestion, a concept that is critical to network administrators in their quest for packet loss prevention over the TCP architecture. Towards the end of the paper, suggestions for developing better ways of congestion handling in mesh networks by use of round trip times as a basis for adaptive congestion detection and control are elaborated.

Keywords

TCP, Congestion, Throughput, Bandwidth, Algorithm.

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Vincent O. Nyangaresi ¹, Silvance O. Abeka ¹, Solomon. O. Ogara ¹

Affiliations
1 School of Informatics & Innovative Systems, Jaramogi Oginga Odinga University of Science & Technology, KE

Abstract

In the recent years, many organizations have turned to cloud technology to support their information technology services. The cloud servers are therefore increasingly holding huge and sensitive information belonging to diverse groups of individuals and companies. Additionally, some organizations employ the cloud to provide them with online backup services. One of the most outstanding requirements for cloud customers is availability – the customers must be able to access their information and other resources stored in the cloud any time and from anywhere on the globe. This means that there should be efficient network design such that any delays are averted. The connection between the customer and the cloud can therefore be regarded as delay senstive. Network congestions often lead to delays and packet losses. Transmission control protocol employs four congestion control algorithms – slow start, congestion avoidance, fast retransmit and fast recovery, all of which fail to meet the requirements of delay intolerance. Transmission control protocol pacing has been suggested as a possible solution to delays and packet dropping in computer networks. However, the conventional pacing is static in nature, meaning that constant pauses are introduced between packet transmissions to prevent bursty transmissions which can lead to delays at the receiver buffers. This paper therefore presents a congestion aware packet routing where the delay period is hinged on the prevailing network conditions. This dynamic pacing algorithm was designed and implemented in Spyder using Python programming language. It employed probe signals to gather network intelligence such as the applicable round trip times of the network. Thereafter, this network intelligence was employed to tailor the paces to these network conditions. The results obtained showed that this algorithm introduced longer paces when more packets are transmitted and shorter paces when few packets are transmitted. In so doing, this new algorithm gives enough time for large packets to be delivered and smaller paces when few packets are sent. The analysis was done in terms of bandwidth utilization efficiency, round trip times and congestion window size adjustments. The congestion window – time graphs and throughput – time graphs showed that the developed dynamic pacing algorithm adjusted quickly to network congestions hence ensuring that the network is efficiently utilized by averting delays

Keywords

Cloud Computing, Congestion, Network Delays, Algorithm, TCP Pacing.

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