Differentiated Services have emerged in the Internet arena as a Class of Service approach to providing better than best effort quality, in contrast to Integrated Services which uses the more stringent, and complex Quality of Service approach.
Essentially, the observation is that through pricing, and understanding of user requirements, it appears that we can control, and users can accept a limited repertoire of quality of service parameters which can be defined as profiles for particular application usage types. These have detailed specifications, but since they are only added at the rate at which new usage patterns and new applications are devised, there is no need to signal the parameters explicitly. Instead the parameters are programmed into routers, and a class of service is slected by subscription or by marking using class of service bits in the Differentiated Services byte present in every pacjet in the IPv4 and IPv6 packet headers. Other functions are still present (later in this chapter we will describe them in detail) but are simplified and invoked less frequently.
There is great enthusiasm for this approach at the current time.