Tese de mestrado. Redes e Serviços de Comunicação. Faculdade de Engenharia. Universidade do Porto. 2006

Dissertação apresentada para obtenção do grau de Mestre em Redes e Serviços de Comunicação, na Faculdade de Engenharia da Universidade do Porto, sob a orientação do Professor Doutor Raúl Filipe Teixeira Oliveira

Το VoIP (Voice Over IP) αναφέρεται στη μετάδοση και τη σηματοδοσία επικοινωνιών φωνής π.χ τηλεφωνικές κλήσεις πάνω από IP δίκτυα όπως είναι το διαδίκτυο. Σκοπός της παρούσας διπλωματικής ήταν η μελέτη της παρεχόμενης ποιότητας ομιλίας VoIP τηλεφωνικών συσκευών (Sitel,Polycom) κάτω από σενάρια διαφορετικών συνθηκών κίνησης στο δίκτυο. Αρχικά παρουσιάζονται οι εφαρμογές του voip και στη συνέχεια αναλύονται η λειτουργία, η αρχιτεκτονική και τα πρωτόκολλα της τεχνολογίας αυτής. Ακολούθως περιγράφεται η πειραματική διάταξη που απαιτήθηκε για να συγκεντρωθούν οι μετρήσεις από τις συσκευές και στη συνέχεια οι γραφικές αναπαραστάσεις των μετρήσεων αυτών που αφορούν της παρεχόμενη ποιότητα ομιλίας. Γίνεται ανάλυση των γραφικών και σύγκριση με ανάλογες της βιβλιογραφίας. / The VoIP technology refers to the transmission of voice samples over the Internet Protocol. The aim of the thesis is to investigate the QoS of a VoIP call under various networks circumstances when various impairments occur. The devices that we put under test belong to Sitel and Polycom company.

This master thesis deals with the design and implementation of an application for analyzing Voice over IP quality using NetFlow. In the beginning, there is summarized basic information about VoIP technology and NetFlow - its principles, the most used protocols, factors that have influence on call quality and call quality rating methods. Later there is presented proposal of application and then described its implementation. The created application was tested on samples, which simulate calls in network with delays and packet-loss. Within testing was made the comparison with commercial application and the results are discussed.

<p>One of the most parts of VOIP management is fault management and, in having a good fault management, finding good mechanisms to detect faults in the network have to be considered.</p><p>The main focus of this project is to implement different types of fast fault recovery protocols in networks<strong>,</strong> especially networks that carry IP telephony. Having a complete understanding of some common link failure detection and fault recovery protocols<strong>,</strong> such as spanning tree protocol (STP), rapid spanning tree protocol (RSTP) and per-VLAN spanning tree protocol (PVSTP)<strong>,</strong> and also having a complete understanding of three other common techniques for fault detection and fault recovery, such as hot standby routing protocol (HSRP), virtual router redundancy protocol (VRRP) and gateway load balancing protocol (GLBP) will be regarded in the project. We are going to test some fault recovery protocols which can be used in IP telephony networks and choose the best. We intend to focus on this issue in LAN environment in theoretical descriptions and practical implementations.</p><p>The final outcome of the thesis is implementation in the Halmstad University’s lab environment to obtain the final result. For doing our thesis, we are going to use some technical tools as hardware tools (Cisco L3 and L2 switches, Routers, IP Phones) and tools which are used for network performance monitoring<strong>,</strong> like as CommVeiw.</p>

One of the most parts of VOIP management is fault management and, in having a good fault management, finding good mechanisms to detect faults in the network have to be considered. The main focus of this project is to implement different types of fast fault recovery protocols in networks, especially networks that carry IP telephony. Having a complete understanding of some common link failure detection and fault recovery protocols, such as spanning tree protocol (STP), rapid spanning tree protocol (RSTP) and per-VLAN spanning tree protocol (PVSTP), and also having a complete understanding of three other common techniques for fault detection and fault recovery, such as hot standby routing protocol (HSRP), virtual router redundancy protocol (VRRP) and gateway load balancing protocol (GLBP) will be regarded in the project. We are going to test some fault recovery protocols which can be used in IP telephony networks and choose the best. We intend to focus on this issue in LAN environment in theoretical descriptions and practical implementations. The final outcome of the thesis is implementation in the Halmstad University’s lab environment to obtain the final result. For doing our thesis, we are going to use some technical tools as hardware tools (Cisco L3 and L2 switches, Routers, IP Phones) and tools which are used for network performance monitoring, like as CommVeiw.