Revised on Nov. 19, 2001
Diversified network applications are making their appearance as the Internet continues to develop and spread. In particular, a great variety of new applications such as realtime streaming audio and video are coming into use. These kinds of new applications not only generate considerable traffic compared to usual applications but also demand the network to provide new services not required in the past. One example is the need for Quality of Service (QoS) functions to make the transfer of audio and video data more efficient.
In addition, data links that connect to the Internet are becoming increasingly diversified and sophisticated. These include the Ethernet and the tagged Ethernet extension, asynchronous transfer mode (ATM) links, and satellite links, all having various characteristics and functions. Compared to conventional data links that were limited in functionality and variety, today's environment of diversified and high-performance data links presents the possibility of more efficient network use if the functions of these data links can be utilized from the application side.
In the above way, the requirements of applications and the environment surrounding networks are undergoing major changes compared to the situation in the past. Nevertheless, protocol stacks continue to use these data links simply as communication channels for transferring packets and deal only with whether packets have been successfully sent and received on these links. They conceal network details and provide applications with abstract packet-transfer functions. While this approach is sufficient for conventional applications and networks that deal mostly with text transfer, it cannot satisfy the demands of multimedia applications. For example, even if QoS functions like priority setting and resource reservation are provided on data links, they cannot be directly used by applications. Furthermore, since network information is hidden from applications, it becomes difficult for applications to adapt to dynamic changes in network status.
To solve this problem, we propose Clea, a framework for the coordination of applications and networks. Clea provides a platform so that requests from applications can be conveyed to the network and network information can be used by applications. As a result, applications can adapt flexibly to dynamic changes in network status and can make use of network resources more effectively. Clea also enables the coordination of applications and networks to be described in a uniform and concise manner.
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© Toshiharu Sugawara