Within the last years, network applications requires higher availability and reliability for critical application environments. In addition, realtimeness and security issues also have been addressed. The purpose of this research is nationwide integrat ...
Within the last years, network applications requires higher availability and reliability for critical application environments. In addition, realtimeness and security issues also have been addressed. The purpose of this research is nationwide integration of network application for Air navigation control centers for the Republic of Austria with this critical requirement. There are big internet infrastructure between several operation centers and wireless transmission towers nationwide. With this networking environment, this research integrates various network applications over internet with the consideration of high availability, reliability, realtimeness and security.
Among the various applications, VoIP (Voice over Internet Protocol) calls the attention of Air navigation since voice communication is the most for the air traffic control. From the aspect of network application, VoIP replaces more frequently common analog and digital circuit switched communication technologies. Due to the use of the IP network not only for voice communication but also for numerous additional services, advantages for companies which extend their PSTN (Public Switch Telephone Network) by VoIP can get achieved. Additional, the internet coverage and bandwidth increase, forwards VoIP propagation among private and commercial internet users.
Actual VoIP technology makes its entrance in safety critical communication applications like emergency call systems. Hence not only network security but also availability issues arise for Air navigation control. VoIP operates on the base of IP (Internet Protocol) networks and therefore on the base of routers, switches, and gateways. If a node or link failure results in a communication breakdown, a new path between two endsystems should be found within milliseconds for availability issues. Therefore the underlying network has to reconfigure itself straight away. Even static routing algorithms can be an appropriate solution for this problem, the maintenance complexity decreases by using dynamical routing technologies. Common Layer 2 and Layer 3 network protocols like STP (Spanning Tree Protocol), RSTP (Rapid Spanning Tree Protocol), LACP (Link Aggregation Control Protocol), IS-IS (Intermediate System to Intermediate System Protocol), or OSPF (Open Shortest First) are commonly used in networks even a failover of some seconds or nearly a minute seems to be sufficient there. This VOLARE project takes a look at the OSPF routing protocol and the routing protocol independent Hello protocol BFD (Bidirectional Forwarding Detection). In a topology using COTS (Common off the shelf) Layer 2 and Layer 3 networking hardware its use for time critical VoIP applications is verified. Actually only the end-systems are of interest the switching time within the network between the end systems will be discussed. The result of this work should be a well-priced, highly available network which reaches failover times down to milliseconds.
In order to maintain high availability, another back-up network has been introduced. High Altitude Platforms (HAP) are one of the useful solution for carrying wireless network routers. In other words, those HAPS can work as mobile base stations (MBS). Deployed around 21Km height, multiple HAPS can back-up the terrestrial network in case of its corruption or any unavailable situation. In this research, we focused configuration problem of HAP based backup network. In order to place HAP MBS on the proper location for maximum availability of network, Expectation-Maximization algorithm used in order to cluster ground nodes and HAP MBS were put on the centroid of each cluster. Our result meets the requirement of ITU recommendations and we guess it is one of the useful solution for backup network configuration. One of the possible next research will be the joint operation between terrestrial network and HAP based backup network and finallly seamless integration between those two networks.