| 461. |
|
|
| 462. |
- Isaksson, Lennart
(författare)
-
Improved Performance of Bluetooth with Focus on Ad-Hoc Applications
- 2004
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The number of devices making use of Bluetooth cable-replacement technology has rapidly increased in numbers thanks to the amount of implementations in cellular telephones, Personal Digital Assistants (PDAs), etc. Instead of the point-to-point technique used today the wireless community demands more sophisticated solutions to transmit information between two devices, e.g. using a chat program within an ad-hoc network. However, Bluetooth provides neither a routing protocol, nor is the slave/slave bridge, which is an important enabler for point-to-multipoint communication in so-called scatternets, implemented in hardware. Another issue relates to the time-to-connect which determines the usability of Bluetooth in scenarios where the units move around. In order to build research on these topics on trustworthy ground, we first address the validation of a Bluetooth simulation model, implementing the Frequency Hopping Spread Spectrum (FHSS) technique of Bluetooth version 1.1 in a correct way. A potential source of problems in reference simulation models has been identified and corrections are described. Next, an improvement is presented for the pseudo random hop sequence regarding the distribution of frequencies used in the Adapted Channel Hopping (ACH) scheme for Bluetooth version 1.2. Further, the impact of the random backoff boundary, which determines the duration of the inquiry procedure and thus of the time-to-connect, is studied by simulation. Obviously, the settings of this parameter contained in the specification leads to suboptimal behaviour. In this thesis, a lower random backoff boundary parameter is suggested, which yields much faster time-to-connect. Finally, the Modified Reverse Path Forwarding (MRPF) routing algorithm for Bluetooth is proposed. This algorithm reduces the amount of connections needed to transmit Asynchronous Connection Less (ACL) data packets as compared to the standard RPF, at the cost of additional overhead. Altogether, especially with the proposed improvements of Bluetooth performance, this technology can be considered to be well suited for nomadic scenarios.
|
|
| 463. |
- Isaksson, Lennart, et al.
(författare)
-
On-Demand Ad Hoc Routing with Modified Reverse Path Forwarding for Bluetooth
- 2004
-
Konferensbidrag (refereegranskat)abstract
- In an ad hoc network connection establishment is done to secure a path for routing packets from source to destination. This path is then maintained to secure further transmissions. In the case of Wireless Personal Area Networks (WPAN) which are more flexible, this is not usable. This is especially the case for Bluetooth. Some constraints in Bluetooth demands a more flexible on-demand ad hoc network compared to other types of ad hoc network protocols. Initially we found that creating a scatternet is not practically possible using Bluetooth version 1.1. The slave/slave bridge is not implemented into the hardware to create a scatternet. In this paper, we present a modified version of the Reverse Path Forwarding (RPF) algorithm to make it suitable for Bluetooth routing. With an on-demand ad hoc network solution together with the modified RPF algorithm we present a suitable solution for Bluetooth packets to be routed in a flexible ad hoc network. To be able to test the modified RPF and the on-demand ad hoc network, a test platform has also been developed.
|
|
| 464. |
- Isaksson, Lennart, et al.
(författare)
-
Validation of Simulations of Bluetooth's Frequency Hopping Spread Spectrum Technique
- 2004
-
Konferensbidrag (refereegranskat)abstract
- The need for performance studies avoiding expensive hardware installations and the lack of analytical models motivates the need of trustworthy simulation models for the cable-replacement technology Bluetooth. In this paper we show a detailed description of the Bluetooth technique and validation of different simulation models used today. To do this, a two-step approach for validation and credibility is necessary. First, a comprehensive empirical measurement was performed to establish a "status quo" of the behavior of today's Bluetooth technology. Second, a validation between empirical and simulation model is conducted to ensure the comparability. To accomplish these objectives we developed and validated a simulation model with frequency hopping algorithms and the whole state machine including collision detection. The results in form of histograms of different Bluetooth-specific durations indicate problems in case of already established simulation programs. So, finally, some changes and suggestions how to correct these defects are given.
|
|
| 465. |
- Jacobsson, Andreas
(författare)
-
Exploring Privacy Risks in Information Networks
- 2004
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Exploring privacy risks in information networks is analysing the dangers and hazards that are related to personal information about users of a network. It is about investigating the dynamics and complexities of a setting where humans are served by technology in order to exploit the network for their own good. In the information network, malicious activities are motivated by commercial factors in that the attacks to privacy are happening, not in the name of national security, but in the name of the free market together with technological advancements. Based on the assumption of Machiavellian Intelligence, we have modelled our analyses by way of concepts such as Arms Race, Tragedy of the Commons, and the Red Queen effect. In a number of experiments on spam, adware, and spyware, we have found that they match the characteristics of privacy-invasive software, i.e., software that ignores users’ right to decide what, how and when information about themselves is disseminated by others. Spam messages and adware programs suggest a hazard in that they exploit the lives of millions and millions of users with unsolicited commercial and/or political content. Although, in reality spam and adware are rather benign forms of a privacy risks, since they, e.g., do not collect and/or transmit user data to third parties. Spyware programs are more serious forms of privacy risks. These programs are usually bundled with, e.g., file-sharing tools that allow a spyware to secretly infiltrate computers in order to collect and distribute, e.g., personal information and data about the computer to profit-driven third parties on the Internet. In return, adware and spam displaying customised advertisements and offers may be distributed to vast amounts of users. Spyware programs also have the capability of retrieving malicious code, which can make the spyware act like a virus when the file-sharing tools are distributed in-between the users of a network. In conclusion, spam, spyware and virulent programs invade user privacy. However, our experiments also indicate that privacy-invasive software inflicts the security, stability and capacity of computerised systems and networks. Furthermore, we propose a description of the risk environment in information networks, where network contaminants (such as spam, spyware and virulent programs) are put in a context (information ecosystem) and dynamically modelled by their characteristics both individually and as a group. We show that network contamination may be a serious threat to the future prosperity of an information ecosystem. It is therefore strongly recommended to network owners and designers to respect the privacy rights of individuals. Privacy risks have the potential to overthrow the positive aspects of belonging to an information network. In a sound information network the flow of personal information is balanced with the advantages of belonging to the network. With an understanding of the privacy risk environment, there is a good starting-point for recognising and preventing intrusions into matters of a personal nature. In reflect, mitigating privacy risks contributes to a secure and efficient use of information networks.
|
|
| 466. |
|
|
| 467. |
|
|
| 468. |
- Jacobsson, Andreas, et al.
(författare)
-
Privacy-Invasive Software in Filesharing
- 2004
-
Konferensbidrag (refereegranskat)abstract
- Personal privacy is affected by the occurrence of adware and spyware in peer-topeer tools. In an experiment, we investigated five file-sharing tools and found that they all contained ad-/spyware programs, and, that these hidden components communicated with several servers on the Internet. Although there was no exchange of files by way of the file-sharing tools, they generated a significant amount of network traffic. Amongst the retrieved ad-/spyware components that communicated with the Internet, we discovered that privacy-invasive information such as, e.g., user data and Internet browsing history was transmitted. In effect, ad-/spyware activity in file-sharing tools creates serious problems not only to user privacy and security, but also to network and system performance. The increasing presence of hidden and bundled ad /spyware programs are therefore not beneficial for the development of a secure and stable use of the Internet.
|
|
| 469. |
- Jena, Ajit K., et al.
(författare)
-
Application Layer Tracing for Performance Evaluation
- 2002
-
Konferensbidrag (refereegranskat)abstract
- The paper reports on a set of non-intrusive tools that can be used for the performance evaluation of "classical" Internet applications such as Email, WWW, and FTP. At the application layer, key factors influencing the events are stochastic aspects of user behavior, protocol characteristics and sizes of contents transferred. A multi pronged approach involving application log analysis, direct probe of the WWW pages, and network flow analysis has been used. The measurement infrastructure is presented and diverse software tools for gathering of application layer properties are described in detail. The motivation is to build stochastic models for the key elements of application layer that can be further used to build up an integrated end-to-end performance testbed for conducting traffic engineering experiments.
|
|
| 470. |
- Jena, Ajit K., et al.
(författare)
-
End-User Performance of WWW Services
- 2001
-
Konferensbidrag (refereegranskat)abstract
- The global Internet has seen tremendous growth in terms of nodes and user base as well as of types of applications. One of the most important consequences of this growth is related to an increased complexity of the traffic models experienced in the networks. Each application has a set of unique characteristics in terms of the way it performs its transactions as well as the way transaction processing profile maps onto unique network resource requirements. In order to support Internet applications effectively, it is therefore important to understand and to characterize the application level transactions and also to investigate their scaling properties. Recent advances in high resolution traffic monitoring and analyzing capabilities have enabled us to build up realistic models for the TCP/IP protocol stack with diverse network applications. In this paper we report investigations of classical applications such as FTP, SMTP, and HTTP to evaluate end-to-end performance requirements and accordingly to assess end-user performance like Service Level Agreement (SLA) for WWW. Our results show the presence of a robust correlation structure in the traffic streams that has a fundamental bearing on the user perceived quality of the applications.
|
|
