IP Quality of Service Models

Abstract

Currently the Internet offers a point-to-point delivery service, which is based on the “best effort” delivery model. In this model, data will be delivered to its destination as soon as possible, but with no commitment about bandwidth or latency. Using protocols such as the Transmission Control Protocol (TCP), the highest guarantee the network provides is reliable data delivery. This is adequate for traditional data applications like e-mail, web browsing, File Transfer Protocol (FTP) and Telnet, but inadequate for applications requiring timeliness. For example, multimedia conferencing or audio and video streaming applications, which require high bandwidth capacity and are sensitive to delay and delay variation. For these applications to perform adequately, Quality of Services (QoS) must be quantified and managed, and the Internet must be modified to support real-time QoS and controlled end-to-end delays. The efforts to enable end-to-end QoS over the Internet Protocol version 4 (IPv4) networks have led to the development of two different architectures, the Integrated services architecture (Intserv) and the Differentiated services architecture (Diffserv), which although different, support services that go beyond the best effort service. This chapter will present a detailed discussion on these IPv4 quality of services models. First, the Integrated services architecture with its related issues such as the reservation setup protocol will be demonstrated. Second, the Differentiated services architecture with a description of the services they provide will be described. Finally, a comparison between the Best-effort, the Integrated and Differentiated services will be done.