The Internet has transformed itself into a critical global information infrastructure, and fundamentally altered the ways we access information, communicate and interact with each other, purchase goods and services, and entertain ourselves. Despite its enormous success, the Internet suffers certain well-known shortcomings, and is increasingly strained to meet the high availability, reliability, mobility, manageability and security demands of Internet applications, users, and service providers alike. Much of my research is centered on addressing the challenges posed by these new demands.

The injection of artificially fragmented prefixes through BGP is a widely used traffic engineering technique. In this paper we examine one particular economic side-effect of deaggregation, namely the impact on the transit traffic bill. We show that the use of more-specific prefixes has a traffic stabilization side-effect which translates into a decrease of the transit traffic bill. We propose an analytical model in order to quantify the impact of deaggregation on the transit costs. We validate our results by means of simulations and through the extensive analysis of real BGP routing information data.

Economic forces behind the Internet evolution have diversified the types of ISP (Internet Service Provider) interconnections. In particular, settlement-free peering and paid peering proved themselves as effective means for reducing ISP costs. In this paper, we propose T4P (Transit for Peering), a new type of hybrid bilateral ISP relationships that continues the Internet trend towards more flexible interconnections at lower costs.

Wireless communication for intelligent transportation systems (ITSs) is a promising technology to improve driving safety, reduce traffic congestion and support information services in vehicles. A new era of vehicular networks that include vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications is approaching.

Sleep modes are emerging as a promising technique for energy-efficient networking: by adequately putting to sleep and waking up network resources according to traffic demands, proportionality between energy consumption and network utilization can be approached, with important reductions in energy consumption. Previous studies have investigated and evaluated sleep modes for wireless access networks, computing variable percentages of energy savings.

The placement of regenerators in optical networks has become an active area of research during the last years. Given a set of lightpaths in a network G and a positive integer d, regenerators must be placed in such a way that in any lightpath there are no more than d hops without meeting a regenerator. In the talk I present a few optimization problems that arise within this framework.

Formally, the Internet inter-domain routing system is a collection of networks, their policies, peering relationships and organizational affiliations, and the addresses they advertize. It also includes components like Internet exchange points. By its very definition, each and every aspect of this system is impacted by BGP, the de-facto standard inter-domain routing protocol.

As wireless ad hoc networking becomes more and more popular and ad hoc networks are used for an increasing number of applications, the integration of these networks in today's Internet, still mostly organized as a set of interconnected fixed and wired networks, becomes a key research field in the computer networking domain. Flooding and routing are some of the main challenges posed by the convergence of the Internet and wireless ad hoc networks

Inter-domain traffic engineering is an important aspect of network operation both technically and economically. Traffic engineering the outbound direction is less problematic as routers under the control of the network operator are responsible for the way traffic leaves the network. The inbound direction is considerably harder as the way traffic enters a network is based on routing decisions in other networks.

A majority of ISPs (Internet Service Providers) support connectivity to the entire Internet by transiting their traffic via other providers. Although the transit prices per Mbps decline steadily, the overall transit costs of these ISPs remain high or even increase, due to the traffic growth. The discontent of the ISPs with the high transit costs has yielded notable innovations such as peering, content distribution networks, multicast, and peer-to-peer localization.