This is the story of researchers who solved the problem of integrating
satellites into the Internet infrastructure, created a startup and
are now developing new applications of their standard.
In 1996, Eutelsat, a worldwide operator in satellite infrastructure,
approached INRIA in order to study the possibility of integrating satellites
into the Internet and thus transmit broadband data. Their idea was
simple: geostationary satellites put into orbit in view of the deployment
of digital TV (using the DVB standard, Digital Video Broadcast) have
a huge unused transmission capacity. Why not try and use them just
like the fiber optics infrastructure to transmit broadband Internet
data (at that time the most powerful modems connected to the telephone
network were liberally transmitting 56 kilobits per second)? INRIA
research scientists rapidly identified the technological deadlocks—the
routing protocols used to transmit the information and data. These
protocols work through an exchange of data between routers—the
communication nodes—that let them know about the network topology
and find transmission paths. This functioning mode assumes a two-way
communication: point B is assumed to be reachable by router A if router
A is receiving information from B.
Now in the case of a satellite, due to economic reasons, a home user
may only receive data: reception antennas are cheap as opposed to transmitter
antennas which are very costly. The idea was thus to use satellites
to receive broadband data and keep the telephone network and modems
to send data, without modifying the functioning of the network. In
other words, the point was to integrate satellites using one-way communications
into a network, the routing protocols of which assume two-way links.
A routing protocol dedicated to satellites
Eutelsat was convinced that satellites were an interesting solution
for broadband data transmission. The company thus funded a study
carried out by the team of project RODEO of Sophia Antipolis. A transmitter
antenna was purchased and Eutelsat set aside hours of satellite transmission
for INRIA during a few years to perform experiments. Within six months,
the researchers had devised a first, theoretical solution. The trick
was to make believe that the satellite link was two-way.
In December 1996, INRIA created a dedicated work group at the IETF
(Internet Engineering Task Force), the Internet protocol standardization
body. The group was called UDLR (Unidirectional Link Routing) and co-chaired
by Walid Dabbous, Head of project RODEO (renamed PLANETE since 2001)
and Yongguang Zhang (Hughes Research Labs). “We needed one year
of theoretical discussions before we could even think about the first
developments,” remembers Walid Dabbous, “Then our team
worked for two years on software, computer boards, experiments and
development.” In addition to RODEO members, Japanese researchers
from project WIDE (a group of Japanese scientists and industry representatives)
participated in the design of the standard.
The protocol, also called UDLR, and the deployment of services were
tested on satellite links independently by INRIA and a Japanese team.
In April 2001, the researchers' efforts were crowned with success.
After four years of validation by the international community, their
protocol was recognized by the IETF under RFC 3077 (Request For Comments),
an indispensable open sesame prior to any standardization. The protocol
is now validated as a “proposed standard.”
A startup to boot
In June 2000, bolstered by their success, four INRIA researchers-engineers
(Emmanuel Duros, Luc Ottavj, Patrick Cipière and Antoine Clerget)
together with Didier Tymen launched themselves in industry in order
to market and integrate the UDLR protocol into ready for use software.
They founded the UDcast company at Sophia Antipolis.
In the meantime, the advent of broadband, especially that of ADSL over
phone lines, had considerably diminished the interest of satellite
Internet integration. In effect, the ADSL technology is cheaper and
offers better performance with shorter transmission delays, which allows
for better interactivity. Nonetheless, satellites remain an interesting
solution to establishing broadband links in rural areas, or in countries
with problematic connectivity even in urban areas. They also make it
possible to secure terrestrial corporate networks against natural or
criminal risks. Emergency satellite links offer the guarantee of a
separate, direct and immune path in case of failure of terrestrial
equipment.
Satellites and interactive digital TV
In addition, the UDLR protocol as it was designed is not specifically
dedicated to satellite links, but above all to unidirectional routing.
Today, it finds an increasing number of applications in entirely
different contexts. This is the case for example in terrestrial digital
audio streaming or in digital television for portable devices, in
particular to make such broadcasted services fully interactive. The
UDLR protocol also paradoxically regains interest in terrestrial
networks of TV on demand contents distribution over fiber optics,
which are characterized by heavy downlink throughput towards the
user and light uplink throughput. The protocol makes it possible
to practically divide the number of fibers by two and reduce the
cost of coupling devices (the interfaces used to send data into the
fiber optics).
The excellent health of UDcast is proof of the multiple applications
of UDLR. The company now has a staff of 22 with an office in Paris
and one in Washington D.C. The company focused on solving performance
and security problems concerning the distribution of IP protocols and
offers Internet access and application providers products, hardware
and software. It has established a strong partnership with Nokia to
distribute data or TV on mobile phones using the frequencies of digital
terrestrial TV.
