<p>Firewalls protect network traffic and decide witch traffic to send further and witch traffic will be blocked. All this depends on the rules in the firewall. The firewall is installed between the internal network and the Internet. It is difficult to find a firewall that can protect us against different threats. Firewalls have both advantages and disadvantages and all this make them vulnerable. It is important to understand how the firewall protects the network and how to configure it. This paper gives the reader a clear idea how firewalls can protect against different attacks and improve the security.</p><p>Computers are not safe when connected to Internet. This paper is about how to use a personal firewall to protect a computer when connected to Internet. One of the firewalls in this examination is Norton Personal Firewall 2005.</p><p>Perkins, “Firewalls 24seven, 2nd Edition” and Brian Komar, Ronald Beekelaar and Joern Wettern “Firewalls for Dummies”. Information has also been collected from Apples home page.</p><p>It is important to have knowledge about different attacks against network traffic and also about how to protect against them. To know the risks is the first step to be able to evolve an own strategy; too defend network attack.</p>

Die vorliegende Arbeit entwickelt und implementiert ein System für die Bereitstellung von Internet-Diensten an öffentlichen Orten. Besonderer Wert wurde auf eine einfache Handhabung für den Nutzer, eine breite Unterstützung von Klienten und ein breites Spektrum möglicher Privilegien (von der vollen Internetkonnektivität bis zu einer Art Infoterminalstatus) gelegt.

Diese Diplomarbeit beschreibt eine Software zur dreidimensionalen Visualisierung der Vorgänge in Computernetzwerken. Dabei werden die Protokolle TCP, UDP, IP, ARP und Ethernet grafisch veranschaulicht. Das Programm stellt außerdem Routing und NAT (Network Address Translation) dar. Zusätzlich gibt es drei von der Software erstellte Videos (je 2 - 15 MB).

There is no doubt that BitTorrent nowadays is one of the most popular peer-to-peer (P2P) applications on the Internet, contributing to a significant portion of the total Internet traffic and being a basis for many other emerging services such as P2P Internet Protocol Television and Video on Demand. On the other hand, Network Address Translation (NAT) devices have become pervasive in almost all networking scenarios. Despite of the effort of NAT traversal, it is still very likely that applications, especially P2P ones, cannot receive incoming connection requests properly if they are behind NAT. Although this phenomenon has been widely observed in measurement work, so far there is no quantitative study in the literature examining the impact of NAT on P2P applications. In this work, we build analytical models to capture the performance of BitTorrent-like P2P systems in a steady state, in the presence of homogeneous and heterogeneous NAT peers. We also propose biased optimistic unchoke strategies, in order to improve the overall system performance and fairness metrics considerably. The analytical models have been validated by simulation results, which also reveal some interesting facts about the coexistence of NAT and public peers in P2P systems.

In recent years, adaptive HTTP streaming protocols have become the de facto standard in the industry for the distribution of live and video-on-demand content over the Internet. In this thesis, we solve the problem of distributing adaptive HTTP live video streams to a large number of viewers using peer-to-peer (P2P) overlays. We do so by assuming that our solution must deliver a level of quality of user experience which is the same as a CDN while trying to minimize the load on the content provider’s infrastructure. Besides that, in the design of our solution, we take into consideration the realities of the HTTP streaming protocols, such as the pull-based approach and adaptive bitrate switching. The result of this work is a system which we call SmoothCache that provides CDN-quality adaptive HTTP live streaming utilizing P2P algorithms. Our experiments on a real network of thousands of consumer machines show that, besides meeting the the CDN-quality constraints, SmoothCache is able to consistently deliver up to 96% savings towards the source of the stream in a single bitrate scenario and 94% in a multi-bitrate scenario. In addition, we have conducted a number of pilot deployments in the setting of large enterprises with the same system, albeit tailored to private networks. Results with thousands of real viewers show that our platform provides an average offloading of bottlenecks in the private network of 91.5%. These achievements were made possible by advancements in multiple research areas that are also presented in this thesis. Each one of the contributions is novel with respect to the state of the art and can be applied outside of the context of our application. However, in our system they serve the purposes described below. We built a component-based event-driven framework to facilitate the development of our live streaming application. The framework allows for running the same code both in simulation and in real deployment. In order to obtain scalability of simulations and accuracy, we designed a novel flow-based bandwidth emulation model. In order to deploy our application on real networks, we have developed a network library which has the novel feature of providing on-the-fly prioritization of transfers. The library is layered over the UDP protocol and supports NAT Traversal techniques. As part of this thesis, we have also improved on the state of the art of NAT Traversal techniques resulting in higher probability of direct connectivity between peers on the Internet. Because of the presence of NATs on the Internet, discovery of new peers and collection of statistics on the overlay through peer sampling is problematic. Therefore, we created a peer sampling service which is NAT-aware and provides one order of magnitude fresher samples than existing peer sampling protocols. Finally, we designed SmoothCache as a peer-assisted live streaming system based on a distributed caching abstraction. In SmoothCache, peers retrieve video fragments from the P2P overlay as quickly as possible or fall back to the source of the stream to keep the timeliness of the delivery. In order to produce savings, the caching system strives to fill up the local cache of the peers ahead of playback by prefetching content. Fragments are efficiently distributed by a self-organizing overlay network that takes into account many factors such as upload bandwidth capacity, connectivity constraints, performance history and the currently being watched bitrate. / <p>QC 20131122</p>

Voice over IP (VoIP) services based on Session Initiation Protocol (SIP) has gained much attention as compared to other protocols like H.323 or MGCP over the last decade. SIP is the most favorite signaling protocol for the current and future IP telephony services, and it‘s also becoming the real competitor for traditional telephony services. However, the open architecture of SIP results the provided services vulnerable to different types of security threats which are similar in nature to those currently existing on the Internet. For this reason, there is an obvious need to provide some kind of security mechanisms to SIP based VOIP implementations. In this research, we will discuss the security threats to SIP and will highlight the related open issues. Although there are many threats to SIP security but we will focus mainly on the session hijacking and DoS attacks. We will demonstrate these types of attacks by introducing a model/practical test environment. We will also analyze the effect and performance of some the proposed solutions that is the use of Network Address Translation (NAT), IPSec, Virtual Private Networks (VPNs) and Firewalls (IDS/IPS) with the help of a test scenario.

Firewalls protect network traffic and decide witch traffic to send further and witch traffic will be blocked. All this depends on the rules in the firewall. The firewall is installed between the internal network and the Internet. It is difficult to find a firewall that can protect us against different threats. Firewalls have both advantages and disadvantages and all this make them vulnerable. It is important to understand how the firewall protects the network and how to configure it. This paper gives the reader a clear idea how firewalls can protect against different attacks and improve the security. Computers are not safe when connected to Internet. This paper is about how to use a personal firewall to protect a computer when connected to Internet. One of the firewalls in this examination is Norton Personal Firewall 2005. Perkins, “Firewalls 24seven, 2nd Edition” and Brian Komar, Ronald Beekelaar and Joern Wettern “Firewalls for Dummies”. Information has also been collected from Apples home page. It is important to have knowledge about different attacks against network traffic and also about how to protect against them. To know the risks is the first step to be able to evolve an own strategy; too defend network attack.

This study assesses elephant induced damage and mortality of baobab and common star-chestnut trees in the northern Kruger National Park. Comparisons are made between the populations north and south of the Luvuvhu River. The density, population size and age structure are estimated. The population structure of neither species has been shaped by elephant utilisation. While the baobab population has a healthy age distribution, that of the star-chestnut population shows that recruitment has declined in recent decades. Utilisation has been found to be higher in the south as a result of higher elephant densities, although recently damage has been greater in the north. Damage increases with tree size. The mortality of baobabs is lower than in other areas where elephants and baobabs co-exist. Elephants are not playing a significant role in mortality of either tree species and management of factors other than elephant is required to improve regeneration rates of these species. / Dissertation (MSc (Wildlife Management))--University of Pretoria, 2007. / Animal and Wildlife Sciences / unrestricted

This diploma thesis deals with the topic of proxy servers and firewalls and considers other associated technologies and network techniques. It systematically describes the general issues of firewalls, with a special focus on proxy firewalls and their safety. Additional systems mentioned in this document are intrusion detection systems (IDS), antivirus systems and content control filters – as these are also connected with safety of networks, servers and workstations or with limiting various Internet sources. IDS systems can be typically supplemented with various additional applications or tools that enrich them and increase their potential – including graphic additions. This part is remembered too. Some systems can communicate with each other, which is successfully utilised (FW & IDS co-operation, for example). The purpose of the first large chapter is to present firewall technologies, to list firewall types, their basic functionality and to present the final comparison. It marginally mentions firewall applications in practice. Chapter two explains the theory of network address translation (NAT), deals with its functionality, safety and with limiting the NAT mechanism. Chapter three brings a comprehensive presentation of proxy servers. It explains their principle from the point of view of functionality and the specification of application areas. The chapter is complete with a clear list of proxy server types and their descriptions. The last chapter named Linux Proxy Firewall is the key part of the work. It deals generally with the Linux platform, the Debian GNU/Linux distribution, principles of safety policy, network configuration, network server safety, Linux firewalls (Netfilter framework, Iptables tool) and with the Squid proxy server. The following subchapters respect the previous structure: they describe the theories of intrusion detection systems, antivirus checks and content filtering based on different methods. All this is presented similarly to the previous chapters. A proxy firewall solution built on the Linux operating system has been proposed in the practical part. The Debian GNU/Linux distribution has been chosen, being very suitable for server use due to its features. This environment is also used for additional safety software contained in the proxy firewall: antivirus protection, content filtering and an intrusion detection system. The priority is the most comprehensive computer network security, which requires detection abilities with the broadest possible coverage in the area of network safety. The purpose of this diploma thesis is not only to describe the principle of operation of proxy servers and to compare them with other types and other systems, but it also brings my own proposed free solution, which increases network safety and has the ambition of comparing it with clearly commercial products available on the market.

Diese Diplomarbeit beschreibt eine Software zur dreidimensionalen Visualisierung der Vorgänge in Computernetzwerken. Dabei werden die Protokolle TCP, UDP, IP, ARP und Ethernet grafisch veranschaulicht. Das Programm stellt außerdem Routing und NAT (Network Address Translation) dar. Zusätzlich gibt es drei von der Software erstellte Videos (je 2 - 15 MB).