Networking Technology

A/I Net: A Network that Integrates ATM and IP

Future networks need both connectionless and connection-oriented services and IP (Internet Protocal) and ATM (Asynchronous Transfer Mode) are major international standards of the two types. In the connectionless IP network, there is no connection setup and each data block carried the destination address which will be used by the routers inside the IP network to direct the data blocks to the destination. A connectionless network is more efficient for  browsing, email, and other non-real-time services.  In the connection-oriented ATM network, however, a connection must be set up before data transmission can start. During connection setup, bandwidth can be reserved by the customers. It is thus a better candidate for supporting services that demand real-time delivery and quality guarantee.

In the past, the two networks are implemented with separate  technologies and built on different platforms.  The goal of this  project is to build a single platform that can handle both types of traffic in a faster and more efficient way.  Furthermore the platform will be programmable and protocol independent.

Multiparty Video Conferencing over the ATM Network

Video conferencing enables people in different physical locations to see and talk to one another without leaving their offices or homes. This saves time and hence increases productivity in the workplace. In the last few years, due to improved processor, compression and network technologies and continuous drop in equipment costs, video conferencing is becoming popular even outside of the workplace. However, even compressed video streams take up a lot of network bandwidth and so video quality is often limited by the network speed. Over the telephone line, the frame rate for a two-party conference is usually only a few frames per second.

With the availability of ATM (Asynchronous Transfer Mode) connections to the homes in Hong Kong, the scenario has changed. The network need not be the limiting factor any more. The challenge is in allowing computers that run in different speeds to communicate with one another without saturating the slower machines and still maintain the best possible performance for each computer. Furthermore, the system should be able to handle workload variation due to participants joining and leaving the conference dynamically. We have developed a system that is able to adjust to workload fluctuation by recomputing the bandwidth requirement and adjusting some of the video parameters such as frame rate and compression ratio to ensure smooth video at every participant's machine. The prototype system runs on four SPARC workstations with different speeds over ATM. It is capable of providing 30 frames per second to the speaker and more than 20 frames per second to each of the other three participants. Significant improvement of video quality has been observed when the resource management mechanism is implemented. The system can also be ported to run on PCs.

A more sophisticated global conferencing system is being developed in conjunction with a German university. This is a two-tier architecture with the upper level system connecting a number of local conferencing systems. Wide area connectivity is achieved using the Internet.

Interactive Multimedia Remote Learning System over the Internet

The advances in computer, multimedia, and networking technologies can now make feasible a remote learning system that involves different media types such as audio, video, and data. Realizing the importance of making use of information technologies available today to improve the quality of teaching, the Hong Kong Government has put aside HK$5 billions to encourage innovative applications of these technologies to enhance the quality of Hong Kong's education system.

We have developed a multimedia remote learning system for an on-campus environment in a cost-effective way by using the latest networking and web technologies. The prototype system shows the efficient use of network bandwidth for providing real-time video/audio broadcast, real-time web page guiding, shared whiteboard and multiparty on-line chatting in an on-campus environment. Scalability in terms of the number of students simultaneously using the system is a major concern. We have adopted the IP multicast technology, which can overcome the problem of excessive bandwidth usage when the number of students involved is large.

The next step of the development is to implement the system over the Internet so that it can be used to conduct real-time lecturing that comprises audio, video, text, web page, graphic, Powerpoint presentation, etc. over a wide area environment (such as within Hong Kong). We will incorporate the latest audio/video streaming and coding technologies with the recently approved Real Time Protocol (RTP) standard at the user ends. In addition, we will test the performance of the system over a wide area network environment using the available wide area networking technologies such as Asynchronous Transfer Mode (ATM) and the next generation Internet Protocol to provide quality of service for the real-time traffic.