Protocol Boosters in the Virtual World
Virtual environment (VE) designs have evolved from text-based systems to
graphical ones. The next logical step of this evolution is to have a fully
immersive environment in which thousands of widely distributed users will be
able to move around and interact. Current VE architectures are unable to
fully meet these requirements and a new network/protocol architecture is
needed.
The VENUS (A Virtual Environment Network Using Satellites) approach
addresses these problems by creating a network architecture which is
scalable and flexible. We define a new architecture consisting of a
transmit-only satellite/server and bi-directional links (as shown in the
diagram below) which will be capable of sustaining a wide-area virtual
environment. VENUS enables users equipped with the appropriate devices
(video goggles, gloves etc.) to move around and interact with other users in
a 3-D virtual world.
Boosters in VENUS
Protocol Boosters play a key role in several parts of VENUS. For the broadcast by the satellite it is not possible to rebroadcast any portion of the frame that has been lost/corrupted during transmission since the broadcast is being sent to several thousand users. Instead, we will use Boosters to include error correction information with some of the essential packets so that receivers will be able to recover data from corrupted transmissions.
On the terrestrial links, a user transmitting from a high speed wired
link will have very different charactersitics than one transmitting over
a slower (and noisy) cellular link. A point-to-point link may be more secure,
and thus require less encryption than a shared link. Boosters are needed
to transparently adapt data according to the type of data, link quality
and also available bandwidth.
Project Status
We have set up a network of computers to emulate the satellite/server, as
shown in the figure below. The first ethernet network (Eth0) is used to
emulate the bidirectional links, and the second one (Eth1) is a
broadcast-only network for the server. The setup is fully functional and we
are currently conducting experiments to evaluate the effects of packet size,
number of objects and link latency on the overall system. We will later also
measure the effects of Boosters on the system. The preliminary results are
available upon request
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