Routing and Traffic Engineering in Dynamic Packet-Oriented Networks
Mihael Mohori, A. vigelj · InTech eBooks · 2012
Telecommunications Networks -Current Status and Future Trends 330 described techniques, procedures and algorithms, even if explained on an example of ISL network, can be generalised and used also in other types of networks exhibiting high level of dynamics (Liu et al., 2011;Long et al., 2010;Rao & Wang, 2010, 2011).The modular approach allows easy (re)usage of presented procedures and techniques, thus, only particular or entire procedures can be used.ISL network exhibits several useful properties which support the development of routing procedures.These properties include (Wood et al., 2001):Predictability -motion of satellites around the earth is deterministic, thus the position of satellites and their connectivity can be computed in advance, taking into account the parameters of the satellite orbit and constellation.Consequently, in an ISL network only undeterministic parameters need to be monitored and distributed through the network, thus minimizing the signalling load.• Periodicity -satellite positions and thus the configuration of the space segment, repeats with the orbit period, which is defined uniquely by the selected orbit altitude.Taking into account also the terrestrial segment, an ISL network will experience a quasi-periodic behaviour on a larger scale, defined as the smallest common integer multiple of the orbit period and the traffic intensity period, referred to as the system period.• Regularity -a LEO constellation with an ISL network is characterized by a regular mesh topology, enabling routing procedures to be considered independently of the actual serving satellite (i.e.concealing the motion of satellites with respect to the earth from the routing procedure).Furthermore, the high level of node connectivity (typically between 2 and 6 links to the neighbouring nodes) provides several alternative paths between a given pair of satellites.• Constant number of network nodes -routing procedures in ISL networks are based typically on the explicit knowledge of the network topology which, in the case of satellite constellation, has a constant, predefined number of network nodes in the space (satellites) and terrestrial (gateways) segments (except in the case of a node or a link failure).This property has a direct influence on the calculation of routing tables.The above properties are incorporated in the described routing and traffic modelling techniques and procedures.Special attention is given to properties which support the development of efficient, yet not excessively complex, adaptive routing and traffic engineering techniques.However, for the verification, validation and performance evaluation of algorithms, protocols, or whole telecommunication systems, the development of suitable traffic models, which serve as a vital input parameter in any simulation model, is of paramount importance.Thus, at the end of the chapter we are presenting the methodology for modelling global aggregate traffic comprising of four main modules.It can be used as a whole or only selected modules can be used for particular purposes connected with simulation of particular models.Routing and traffic engineering on one side require good knowledge of the type of network and its characteristics and on the other side also of the type of traffic in the network.This is needed not only for adapting particular techniques, procedures and algorithms to the www.intechopen.comRouting and Traffic Engineering in Dynamic Packet-Oriented Networks 331 network and traffic conditions but also for their simulation, testing and benchmarking.To this end this chapter is complemented by description of a methodology for developing a global traffic model suitable for the non-geostationary ISL networks, which consists of modules describing distribution of sources, their traffic intensity and its temporal variation, as well as traffic flow patterns. How to referenceIn order to correctly reference this scholarly work, feel free to copy and paste the following: