Section: New Results
Experimental Environment for future Internet architecture
Realistic Networking experimental platforms
The Internet is relatively resistant to fundamental change (differentiated services, IP multicast, and secure routing protocols have not seen wide-scale deployment).
A major impediment to deploying these services is the need for coordination: an Internet service provider (ISP) that deploys the service garners little benefit until other domains follow suit. Researchers are also under pressure to justify their work in the context of a federated network by explaining how new protocols could be deployed one network at a time, but emphasizing incremental deployability does not necessarily lead to the best architecture. In fact, focusing on incremental deployment may lead to solutions where each step along the path makes sense, but the end state is wrong. The substantive improvements to the Internet architecture may require fundamental change that is not incrementally deployable.
Network virtualisation has been proposed to support realistic large scale shared experimental facilities such as PlanetLab and GENI. We are working on this topic in the context of the European OneLab project.
Testing on PlanetLab has become a nearly obligatory step for an empirical research paper on a new network application or protocol to be accepted into a major networking conference or by the most prestigious networking journals. If one wishes to test a new video streaming application, or a new peer-to-peer routing overlay, or a new active measurement system for geo-location of internet hosts, hundreds of PlanetLab nodes are available for this purpose. PlanetLab gives the researcher login access to systems scattered throughout the world, with a Linux environment that is consistent across all of them.
However, network environments are becoming ever more heterogeneous. Third generation telephony is bringing large numbers of handheld wireless devices into the Internet. Wireless mesh and ad-hoc networks may soon make it common for data to cross multiple wireless hops while being routed in unconventional ways. For these new environments, new networking applications will arise. For their development and evaluation, researchers and developers will need the ability to launch applications on endhosts located in these different environments.
It is sometimes unrealistic to implement new network technology, for reasons that can be either technological - the technology is not yet available -, economical - the technology is too expensive -, or simply pragmatical - e.g. when actual mobility is key. For these kinds of situations, we believe it can be very convenient and powerful to resort to emulation techniques, in which real packets can be managed as if they had crossed, e.g., an ad hoc network.
In the OneLab project, we work to provide a unified environment for the next generation of network experiments. Such a large scale, open, heterogeneous testbed should be beneficial to the whole networking academic and industrial community.
Enhancing network simulations
We also need a new generation of simulation tools, that support more heterogeneous, yet closer to reality, models for links and access networks. Modelling the physical characteristics of the actual transmission media, notably for wireless networks, is required and now seems reachable for producing simulated results that would constructively complement experimental results.
We are contributing to ns3 (the future version of the ns network simulator) in order to fulfill the two following objectives: 1) the need to perform accurate experimentations in a more controlled environment than that provided by traditional testbeds such as PlaneteLab, Onelab, Emulab, or Vini. 2) the need to use accurate models of 802.11 and Wimax MAC and PHY systems to study the impact of cross-layer (Application-IP-to-MAC/PHY) optimizations, and,
1) This year, we started investigating the possibility of using simulators as a sort of super testbed where the real code written for real networks runs within the simulator. The goal of this approach is two fold: - we want to provide a more realistic environment than conventional simulations by allowing users to run the same code which runs in real networks unmodified (or minimally modified), - we want to provide a more controllable experimentation environment than conventional real-world testbeds.
To evaluate this line of research, we developed a new simulator, named YANS (see section 5.5). This initial prototype showed the feasability of the approach and we decided not to pursue the development of this tool but to contribute to the ns-3 project that was launched roughly 8 months after we started working on YANS: the stated goals of the ns-3 project are sufficiently close to those we had for YANS that we decided to contribute to the development of the ns-3 project rather than continue the development of our adhoc tool.
Since then, we have been associated to the development of the core infrastructure of the ns-3 simulator: we contributed the event scheduler and the packet data structure used in ns-3. We also contributed to the specification and refinement of the core ns-3 Node data structure. In the future, we plan to keep contributing to architectural discussions and we hope to influence the associated decisions to allow us to realize our vision of a simulator used as a more controllable real-world testbed.
2) the development of MAC/PHY models started 1.5 years ago: we developed a 802.11a/e MAC and PHY model in ns-2. This model implementation was subsequently ported to the YANS simulator  to validate the architecture of YANS. More recently, we started developing a Wimax MAC model for ns-3. This effort is currently focused on the identification of the components required in our model. i.e., we cannot afford to implement all of the specification given our manpower so, we need to identify the relevant components required to perform the type of application-level simulation we are interested in. In parallel to the development of this Wimax MAC model, we have started a ns-3 PHY model project which aims at defining a common API for physical layer models of signal interference and signal propagation. We plan to use the API defined within the context of this project for the above-mentioned Wimax MAC model. Furthermore, we plan to port our 802.11 MAC model to ns-3 and to the PHY-layer API of ns-3.