| Vol. 2, No. 1, November 2005 - Art. 2 |
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| A Top Down View of Quality of Service |
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by
Fouad Tobagi (Stanford University)
Copyright
Copyright © Fouad Tobagi, 2005 |
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Abstract
There is a great interest today in voice communication over the Internet (VoIP). If the Internet is to become the universal network for all communications needs, and thus is to displace the telephone network for voice communication, it must be capable of providing the same level of service quality as the telephone network. Today, this does not seem to be the case. For example, the performance of VoIP is impaired by packet loss and variable packet delay in the network. Although measures are taken to overcome these problems (e.g., loss concealment and adaptive playout), their effectiveness is limited to certain ranges of network conditions. There is also a sense of dissatisfaction on the part of users when using the Internet for interactive data applications, such as Telnet and Web browsing; long delays are experienced in web page downloads and in telnet echoes. New data applications such as online trading and gaming also have stringent reliability and delay constraints that are not always met in the Internet in its current state. Clearly, improvements in the quality of service that the Internet can provide must be made. Knowing the application requirements and understanding the impairments that result if these requirements are not met is crucial to the design of the network. What is also crucial is an understanding of the characteristics of packet delay and packet loss in the network so as to devise the appropriate solutions. The latter may require extensive measurements and possibly simulation of a good representation of paths in the Internet. This paper summarizes research results pertaining to the handling of various traffic types (voice, video, real-time data) in various types of networks that may be found in an end-to-end path in the Internet; specifically, wide area backbone networks, metropolitan area networks, and wireless LANs. |
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