Abstract:
Traditionally, two types of network measurement (active and passive) have been introduced to monitor characteristics in a network. Examples of such network characteristics are jitter and latency which impact delay-sensitive Voice over IP (VoIP) and other real-time applications. In this thesis, we develop an active measurement tool that we refer to as the beacon software. We use this tool to investigate the impact of path characteristics including jitter, latency, packet loss, and out-of-order arrivals on real-time applications such as VoIP, streaming and download style traffic. Starting with a simulated VoIP over User Datagram Protocol (UDP) experiment, we record information such as the inter-arrival time of packets, serial number, and the time to live (TTL) value of packets. Then we use our data to determine the above mentioned path characteristics. An additional aspect of this thesis looks at the application of T-entropy to determine if load balancing is a contributing factor to jitter. Furthermore, in our VoIP over Transmission Control Protocol (TCP) experiment we record information such as the size, serial number and arrival time of data chunks. With the information from these experiments we determine characteristics including the minimum buffer time requirement for VoIP application. In addition, we also perform experiments to study the impact of congestion on web and file transfer applications. In these experiments, we simulate file download TCP sessions between nodes and we use the data to determine characteristic such as the percentage of congested chunks. Our studies indicate that high jitter, latency and poor voice quality occur in countries that use high latency satellite connections. The second part of this thesis looks at potential solutions for improving goodput and proposes the use of TCP over Network Coding (TCP/NC) as a solution. We conducted experiments with nodes deployed in countries with high latency satellite connections and found that TCP/NC can improve goodput during periods of high packet loss.
