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.
TopIntegrated Service
The Internet Integrated services framework provides the ability for applications to choose among multiple, controlled levels of delivery service for their data packets. To support this capability, two things are required; first, individual network elements (subnets and IP routers) along the path followed by an application's data packets must support mechanisms to control the quality of service delivered to those packets. Second, a way to communicate the application's requirements to network elements along the path and to convey QoS management information between network elements and the application must be provided.
In the integrated services framework the first function is provided by QoS control services such as Controlled-Load service (Wroclawski, 1997) and Guaranteed service (Shenker, Partridge, & Guerin, 1997). The second function may be provided in a number of ways, but it is frequently implemented by a Resource Reservation Setup Protocol such as RSVP (Black, Brim, Carpenter, & Le Faucheur, 2001).