The Effect of the Buffer Size in QoS for Multimedia and bursty Traffic: When an Upgrade Becomes a Downgrade

This work presents an analysis of the buffer features of an access router, especially the size, the impact on delay and the packet loss rate. In particular, we study how these features can affect the Quality of Service (QoS) of multimedia applications when generating traffic bursts in local networks. First, we show how in a typical SME (Small and Medium Enterprise) network in which several multimedia flows (VoIP, videoconferencing and video surveillance) share access, the upgrade of the bandwidth of the internal network may cause the appearance of a significant amount of packet loss caused by buffer overflow. Secondly, the study shows that the bursty nature of the traffic in some applications traffic (video surveillance) may impair their QoS and that of other services (VoIP and videoconferencing), especially when a certain number of bursts overlap. Various tests have been developed with the aim of characterizing the problems that may appear when network capacity is increased in these scenarios. In some cases, especially when applications generating bursty traffic are present, increasing the network speed may lead to a deterioration in the quality. It has been found that the cause of this quality degradation is buffer overflow, which depends on the bandwidth relationship between the access and the internal networks. Besides, it has been necessary to describe the packet loss distribution by means of a histogram since, although most of the communications present good QoS results, a few of them have worse outcomes. Finally, in order to complete the study we present the MOS results for VoIP calculated from the delay and packet loss rate

Traffic characteristics mechanism for detecting rogue access point in local area network

Rogue Access Point (RAP) is a network vulnerability involving illicit usage of wireless access point in a network environment. The existence of RAP can be identified using network traffic inspection. The purpose of this thesis is to present a study on the use of local area network (LAN) traffic characterisation for typifying wired and wireless network traffic through examination of packet exchange between sender and receiver by using inbound packet capturing with time stamping to indicate the existence of a RAP. The research is based on the analysis of synchronisation response (SYN/ACK), close connection respond (FIN/ACK), push respond (PSH/ACK), and data send (PAYLOAD) of the provider’s flags which are paired with their respective receiver acknowledgment (ACK). The timestamp of each pair is grouped using the Equal Group technique, which produced group means. These means were then categorised into three zones to form zone means. Subsequently, the zone means were used to generate a global mean that served as a threshold value for identifying RAP. A network testbed was developed from which real network traffic was captured and analysed. A mechanism to typify wired and wireless LAN traffic using the analysis of the global mean used in the RAP detection process has been proposed. The research calculated RAP detection threshold value of 0.002 ms for the wired IEEE 802.3 LAN, while wireless IEEE 802.11g is 0.014 ms and IEEE 802.11n is 0.033 ms respectively. This study has contributed a new mechanism for detecting a RAP through traffic characterisation by examining packet communication in the LAN environment. The detection of RAP is crucial in the effort to reduce vulnerability and to ensure integrity of data exchange in LA

Specification of Smart AP solutions - version 2

This document includes the specification of the second version of the Smart Access Point (AP) Solutions, which are being developed within WP3 of the Wi-5 project. After the Literature Review, a global view of the Wi-5 architecture is presented which includes not only the Smart AP Solutions but also the Cooperative Functionalities being developed in WP4. Next, the Smart AP Solutions are described including the summary of the general approach being followed based on Light Virtual APs (LVAPs). The functionalities enabling Radio Resource Management (i.e. Dynamic Channel Allocation, Load Balancing and Power Control) are reported in detail and the current status of the implementation of the solutions is detailed, with a set of improvements aimed at integrating the support of different channels within the Wi-5 framework. A multi-channel handoff scheme has been designed, requiring a good synchronisation between the different events, in order to make the LVAP switching happen at the same moment when the STA switches its channel. In addition, the beacon generation has been modified in order to improve the scalability and to give a better user experience during handoffs. Tests measuring the handoff delay are presented using three wireless cards from different manufacturers, and using as test traffic a flow of an online game with real-time constraints. The results show that fast handovers ranging from 30 to 200 milliseconds can be achieved. The savings provided by frame aggregation, and its effect on subjective quality have also been studied. A methodology including subjective tests with real users has evaluated this effect, using paired comparison. The results indicate that bandwidth usage savings and especially significant packet rate reduction can be obtained without degrading players’ Quality of Experience (QoE), as long as the overall latency is kept under 100ms. An important finding coming from these results is that the players do not register delay variation introduced by multiplexing