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Chapter 2: Context and Background
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n this chapter, we introduce the main concepts related to the problem we are addressing, in order to provide the casual reader with the necessary background information for this dissertation. As the title of this thesis is “Analysis of Security and QoS in Network with time constraints”, it is clear that our work requires a deep understanding of three main topics: security, Quality of Service (QoS) and network applications with time constraints. These three fundamental topics will be addressed in this chapter. 2.1. Security
In today's business environment, users demand seamless connectivity and stable access to servers and networks wherever they are: hotels, airports, homes, or remote offices. While these functionalities are useful for business, they can only be diffused as such if we can minimize the security risks of transmitting sensitive data across the Internet. 2.2.1. Security Definition (Security Properties)
Protecting information from unauthorized access, use, disclosure, disruption, modification, inspection, recording or destruction in order to provide confidentiality, integrity, and availability is the main goal of information security [NIST 2009]. Security is the ability of a computer system to withstand external physical stresses (fire, flooding, bombs, etc.) or logic (input errors, intrusions, hacking, malicious logic, etc.); this is generally the direction chosen by specialists of security audit, when they must assess the risks related to a computer system [Deswarte 2003].
According to ITSEC (Information Technology Security Evaluation Criteria), security can be defined as a combination of three main properties: confidentiality, integrity, and availability of information [Office 1991]. 2.2.2.1. Confidentiality
Confidentiality