As the network fundamental infrastructures become mature, broadband network turns into the main stream. Sufficient bandwidth makes many applications, for example, voice over IP (VoIP), become possible. Through IP phone, people only need to pay local Internet service fee, which is relatively more inexpensive, to be able to make long-distance call with remote people. After the basic calling facility is ready, additional VoIP services become more and more important. User will demand for more additional service functions. In this thesis, I propose and implement a voice recording facility based on SIP-based VoIP system. Users can record both caller and callee's voice together in digital way. Furthermore, we use this facility to provide a voice message recording service. When callee does not pickup his/her phone, caller's phone will be redirected to voice message recording server. Caller can record his/her voice message into callee's directory on the voice recording server, and callee can listen to his/her own voice message later.

When a service on the internet is scaled horizontally with multiple server instances, there are different solutions on how to map a client request to one of those server instances. In this paper I am evaluating a select few solutions for using the nearest server instance to handle a client request. I classified those solutions on the criteria ease of use, does this solution require a change of program behavior, how many resources are required for set up, the response time, are there already existing open source software or open data solutions available, how accurate is the solution, does it scale horizontally and lastly how robust the solution is. In this paper I evaluated GeoDNS, a central hyper text transfer protocol (HTTP) redirect server, decentralized instances and using an Anycast internet protocol (IP) address as a solution. Based on the described evaluation criteria I found that the central redirect server in combination with a GeoDNS server works best to map a client request to the nearest server instance. The decentralized instances are a specialization of the redirect server and setting up a public routable Anycast address is complicated. I compared three methods of matching a client IP address to a geolocation. In this practical implementation I found using local files matching IP ranges to countries works best over using regional internet registry provided registration data access protocol (RDAP) endpoints or using the same RDAP method with a cache. The local mapping file implementation is the fastest, compared to the other described implementation, and less error-prone. The entire source code of this work and implemented programs can be found here (https://paulgo.dev/mrpaulblack/bachelor-thesis).:1 Introduction and Intention 2 Solutions 2.1 Geolocation DNS 2.2 Central Redirect Server 2.3 Decentralized Implementation 2.4 IP Anycast 3 Implementation 3.1 Experiment Setup 3.2 Method of Observation 3.3 Observations and Analysis 4 Conclusion Bibliography List of Figures List of Tables List of Source Codes

The feasibility of relocating a small (~500,000 kg) Near-Earth Asteroid (NEA) to High Earth Orbit via Solar Electric Propulsion (SEP) is evaluated with the orbital simulation software General Mission Analysis Tool (GMAT). Using prior research as a basis for the mission parameters, a retrieval mission to NEA 2008 HU4 is simulated in two parts: approach from Earth and return of the Asteroid Redirect Vehicle (ARV) with the asteroid in tow. Success of such a mission would pave the way for future missions to larger NEAs and other deep space endeavors. It is shown that for a hypothetical launch time of 24 May 2016, the ARV could arrive within 25 km of 2008 HU4 on 28 Jun 2017 with a Delta V of 0.406 km/s, begin return maneuver on 08 Dec 2017 and reach Earth altitude of 450,000 km by 23 Apr 2026 with a Delta V of 44.639 m/s.

This diploma thesis deals with the design and implementation of a tool for network attack detection from a captured network communication. It utilises the tshark packet analyser, the meaning of which is to convert the input file with the captured communications to the PDML format. The objective of this conversion being, increasing the flexibility of input data processing. When designing the tool, emphasis has been placed on the ability to expand it to detect new network attacks and on integrating these additions with ease. For this reason, the thesis also includes the design of a complex declarative descriptions for network attacks in the YAML serialization format. This allows us to specify the key properties of the network attacks and the conditions for their detection. The resulting tool acts as an interpreter of proposed declarative descriptions allowing it to be expanded with new types of attacks.