Nowadays users expect to experience highly dependable network connectivity and services. However, several recent episodes demonstrate that software errors and operator mistakes continue to cause undesired disturbances and outages. Software-defined networking (SDN) is a new kind of network architecture that decouples the control plane from the data plane – a vision currently embodied in OpenFlow. By logically centralizing the control-plane computation, SDN provides the opportunity to remove complexity from and introduce new functionality in our networks. On the other hand, as the network programmability enhances, risks arise that buggy software in network controllers may disrupt an entire network.

The purpose of this seminar is to provide an introduction to state-of-art technologies and standards related to mobile multi-hop wireless networks, as broadly classified into three categories depending on their typical coverage: broadband wireless access (BWA), wireless local area networks (WLAN) and wireless personal area networks (WPAN).

The talk will cover recent results on cooperative communication schemes for ad hoc and sensor networks. We will first discuss the offline computation of optimal policies for multi-hop virtual MISO transmission for distributed ad hoc networks in the presence of channel impairments such as path loss and multipath fading. Thus, we will elaborate on heuristic and opportunistic routing policies, by comparing their performance to that of optimal routing.

Since its inception in 2005, YouTube has seen explosive growth in its popularity; today it is indisputably the world’s largest video sharing site. Given the number of viewers and the accompanying traffic volume, its geographical span and scale of operations, the design of YouTube’s content delivery infrastructure is a highly challenging engineering task. In this talk, I will present our recent studies on "reverse-engineering" the YouTube video delivery system through passive and active measurements.

Content-Centric Networking (CCN) is a clean-slate proposal to replace/enrich the current Internet. CCN is focused on content instead of machines, so users can request a given content by sending Interest messages with the name of the content. CCN routers have three main data structures: a FIB mapping content names to outbound faces, a Content Store to cache data packets and a pending Interest table (PIT) to forward incoming packets towards the consumers, using a breadcrumb mechanism. Security is part of the proposal, as all data packets are signed by its publisher.

The number of mobile users and their traffic demand is expected to be ever-increasing in future years, and this growth can represent a limitation for deploying current mobility management schemes that are intrinsically centralized, e.g., Mobile IPv6 and Proxy Mobile IPv6. For this reason it has been waved a need for distributed and dynamic mobility management approaches, with the objective of reducing operators' burdens, evolving to a cheaper and more efficient architecture.

Rate Allocation for Layered Multicast Streaming with Inter-Layer Network Coding Abstract Multi-layer video streaming allows to provide different video qualities to a group of multicast receivers with heterogeneous receive rates. The number of layers received determines the quality of the decoded video stream. For such layered multicast streaming, network coding provides higher capacity than multicast routing.

Distributed Opportunistic Scheduling (DOS) techniques have been recently proposed to improve the throughput performance of wireless networks. With DOS, each station contends for the channel with a certain access probability. If a contention is successful, the station measures the channel conditions and transmits in case the channel quality is above a certain threshold.

Supporting voice traffic in existing WLANs results extremely inefficient, given the large overheads of the protocol operation and the need to prioritize this traffic over, e.g., bulky transfers. In this paper we propose a simple scheme to improve the efficiency of WLANs when voice traffic is present.

Dr. Kowalski will present recent advances on contention resolution and packet queuing on a multiple access channel. His will include description of algorithms, both already known and newly developed, accompanied by theoretical analysis of queue sizes and latency. He will conclude with showing and elaborating on selected simulation results that support theoretical formulas.