Quality of Service Support of Distributed Interactive
Virtual Environment Applications in IP Networks
This paper reports on the performance of Distributed Interactive Virtual Environment (DIVE) applications, deployed through Internet. Our goal is to understand the behaviour of a DIVE application, its interaction with competing traffic streams, as well as its network resource requirements for a satisfactory performance. As DIVE is becoming the building block of new applications and services, impacting several established or new and growing sectors of our economy (e.g. electronic commerce, tele-training, transportation, health), it is important that we understand the resource requirements of these applications, as well as the “stress” they will impose on the network.
Distributed Interactive Virtual Environments (DIVE) [1, 2] are shared virtual worlds that could radically alter the way people work, play, learn, consume and collaborate. In DIVE applications, a simulated world runs not on one computer system, but on several, connected over a network (e.g. Internet). People who use those computers are able to interact in real time, sharing the same virtual world. Each of the machines participating in the simulation of the virtual word is called a “host”. On each host there is a number of “entities” (things in the virtual environment) that communicate their changing state by sending “update messages”. The specific entity that corresponds to a participant’s virtual body is called “avatar”. Avatars are either included within the virtual world during initialization or dynamically created at a later time. The following are some of the key features of DIVE applications:
•They are sensitive to packet delays. Any action issued
by any participant in the DIVE (transported through
packets) must reach the other participants within 100
•They should be capable of scaling to large number of
participants. The number of participants should be
unlimited to allow everybody to enter the virtual world.
•Messages are transported through short packets (few
tens of bytes) and frequently. This characteristic differs
from other multimedia application data like audio and
•They demonstrate high level of dynamicity in group
structure and topology. Participants should be able to
join and leave the session dynamically.
While DIVE applications will be used in services related to commerce, health, training, transportation and business, there is no adequate understanding on how they behave in modern networks. In , we presented the first (to the best of our knowledge) research results dealing with sensitivity analysis of DIVE applications in Ethernet and ATM networks, and modeling of DIVE traffic. The work was conducted under a CANARIE funded research project. For completeness, some of our results, reported in  will be included in this work. This paper, expands the work reported in , by testing a VR application in a Differentiated Services (Diffserv) network. Our objective is to assess the ability of DiffServ to support these delay, packet loss and performance sensitive applications, understand the effect “main-stream applications”, such as video, ftp etc., have on DIVE, when they co-exist in the same network, as well as “fine tune” the network’s parameters and architecture, in order to provide acceptable performance levels to DIVE applications. We conducted our study through experimentation. A DIVE based application of tele-training nature was used, which was developed by researchers of the Multimedia Communications Research Laboratory (MCRLab) of the University of Ottawa. Its function is to enable instructors and technical support to train and guide remote users through Internet, on maters related to Newbridge’s ATM
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