Overlay networks create virtual topologies on top of the existing networking
infrastructure and come as a middle layer between end-user applications and the basic
network services. The main reasons of using an intermediate level of communication
are the new service functionality and the improved performance oered by application
specic protocols that can be deployed in overlay networks. This thesis explores the
benets oered by overlay networks and introduces new mechanisms that improve
performance and oer additional functionality to networking applications.
Multicast services are rarely used today, mainly due to scalability and security
concerns. An overlay architecture addresses these issues by moving the service
management and deployment above the network infrastructure. We present an architecture
for transparent overlay multicast and an optimal distributed
ow control
for reliable multicast in overlay networks that scales with the number of participants
and groups.
Even though capacity grows exponentially over time, latency is dicult to
improve. We present an overlay approach that can substantially decrease the number
of delayed packets in wide area reliable communication and increase the delivery
ratio of best eort communication, leading to improved performance in time-sensitive