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Emmanuel DurosI am no longer working at INRIA .I founded with several co-founders a start-up called UDcast in June 2000. It provides a technology that has been developed at INRIA.
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However, this type of network is by nature unidirectional and is not supported by common routing protocols. Routing protocols assume that links are bidirectional and therefore routers connected to an "outgoing" unidirectional link cannot be aware of the existence of networks reachable through this link.
I have been designing and implementing mechanisms in order to support unidirectional links (e.g. broadcast satellite networks) in the Internet. Basically, there are two approaches, the first one is to modify routing protocols to take into account unidirectional links, the second one is to set up link layer tunnels between receivers and feeds. The latter emulates below IP level a bidirectional connectivity in the presence of a unidirectional link: a receiver can send routing messages (through link layer tunnels) to feeds without having to provide modifications to routing protocols.
These mechanisms are being discussed in the UniDirectional Link Routing Working Group of the Internet Engineering Task Force (IETF). This will lead to a standardization of the integration of Broadcast Satellite network in the Internet. Current available documents are given in the next section.
Beside the routing issues, Eutelsat provides us the satellite capacity and the hardware (up-link station and satellite dishes) to experiment IP over satellite. I developed the Unix drivers for the unidirectional interfaces (emission and reception boards for PC). These drivers are written for FreeBSD platforms and are available. FreeBSD platforms can be configured as IP routers and various routing protocols are supported by this operating system. This led me to implement the mechanisms discussed in the UDLR working group and to experiment them with the INRIA satellite network.
I have been experimenting point to point video-conference sessions as well as multicast sessions over the satellite link (taking advantage of high bandwidth services). The latter including dynamic multicast routing which has been demonstrated during the retransmission of the SIGCOMM'97 sessions over the MBone via satellite.
From June 1995 to January 1996, I worked in Sydney (Australia) at the Multimedia Research Center in the University of Technology of Sydney . I interconnected a mobile network mainly composed of Linux stations to the university network. I implemented a client server audio and video application that would adapte itself to the available bandwidth. For instance, selected Mpeg video frames were dropped by the router connected to the mobile network before forwarding the video stream over the wireless link. This was good fun!
In February 1996 till May 2000, I went back to the South of France and I joined the High Speed Networking group at INRIA Sophia-Antipolis. I left the mobile network for a satellite network.
Emmanuel Duros
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