Since the appearance of OpenFlow back in 2008, Software-Defined Networking (SDN) has gained momentum. Although there are some discrepancies between the standards developing organisations working with SDN about what SDN is and how it is defined, they all outline Traffic Engineering (TE) as a key application. One of the most common objectives of TE is the congestion minimisation, where techniques such as traffic splitting among multiple paths or advanced reservation systems are used. In such a scenario, this manuscript surveys the role of a comprehensive list of SDN protocols in TE solutions, in order to assess how these protocols can benefit TE. The SDN protocols have been categorised using the SDN architecture proposed by the Open Networking Foundation (ONF), which differentiates among Data-Controller Plane Interfaces, Application-Controller Plane Interfaces and Management Interfaces, in order to state how the interface type in which they operate influences TE. In addition, the impact of the SDN protocols on TE has been evaluated by comparing them with the Path Computation Element (PCE)based architecture. The PCE-based architecture has been selected to measure the impact of SDN on TE because it is the most novel TE architecture until the date, and because it already defines a set of metrics to measure the performance of TE solutions. We conclude that using the three types of interfaces simultaneously will result in more powerful and enhanced TE solutions, since they benefit TE in complementary ways.
With the increment of passenger railway traffic especially in high speed lines, improvements in railway transportation safety become even more crucial. This paper presents technological and commercial trends in this area, enumerates innovative on-going related projects and proposes the application of new wireless communication standards such as, DSRC -WAVE (Dedicated Short Range Communications and Wireless Access in Vehicular Environment) or 802.11p; 802.16 or WiMAX; and MBWA (Mobile Broadband Wireless Access) or 802.20, in train control communications networks. In order to validate this proposal, we have designed a model for a wireless communication system deployed in a fully redundant configuration. The application of these new open-standard technologies will allow an affordable deployment, ubiquitous, always-on and interoperable muti-vendor mobile broadband train control communication system that supports new safety services and applications. Railway, signaling, wireless, 802.11b/g, MBWA
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