CASE STUDY

Case Study



Table of Content

Introduction3

Discussion3

Firewall4

Network Address Translation5

Application Impact6

Network Intrusion Detection System6

Visualization and Clustering7

TCP SYN-Flood Attack7

Flow-based Packet Selection8

Intrusion Prevention System9

Distributed and Demand-driven Intrusion Prevention10

Security Service Deployment Strategies and Simulation10

Future Work11

Conclusion11

References12

Case Study

Introduction

The goal of a voice communication system is to pass on the voices of the participant within some predetermined measurements of quality. The quality of the system is not only determined by the quality of the voice but also by how long the transmission time is in order for interactive communication to take place. This chapter we will survey the way that quality of service (QoS) is guaranteed in a VoIP implementation. The chapter is divided in to three sections; quality discussion, key issues and measurements for QoS.

When implementing a VoIP system decisions about what speech quality this new network will be capable of delivering are made. The quality can hardly be noticeably worse than the PSTN network, or the users will have a hard time adapting to the new system. Assuming the application is the use of VoIP hardware without quality defects of the next important area to start worrying is the same wide area network, ie the data pipe that will carry voice packets across. A congested WAN consisting of burst packet loss, latency, and jitter all work to degrade the quality of VoIP calls. Different VoIP implementations suffer differently from these effects; however these effects all contribute to lower quality calls in some sense. All kinds of loss in quality due to slow/unpredictable IP traffic patterns can be compensated by an increase in bandwidth [1]. Although this approach often brings extra costs and there may be an imminent risk that the cost for the VoIP solution is higher than the conventional, circuit-switched PSTN calls.

Discussion

Most manufacturers of VoIP solutions generally assume a generally high level of QoS, and basing the settings and performance requirements in the system as a static entry. Though, IP QoS often varies with time-of-day traffic patterns and sometimes takes major hits during very unpredictable data traffic events. On congested IP networks routers will discard packets if their packet inflow exceeds their outflow for a given data route, leading to a big loss of packets when the network gets too busy. If there were some way to measure when things were starting to degrade, VoIP networks could attempt to dynamically improve the quality of current and subsequent calls. Very few VoIP products today have a way of dynamically monitoring QoS, let alone intelligently adapting to changing real-world QoS conditions.

The QoS issues specifically interesting with regards to VoIP are all part of general QoS issues in packet networks. The way that the issues are significant may be a bit different though since the metrics for quality in interactive communication are different from general data traffic. This section will list and describe the key issues concerning VoIP QoS. Different versions of packet delay cause problems. One is echo, which is caused by the signal reflections of the speaker's voice from the far-end telephone equipment ...