With the grown popularity of the Internet and the increasing use of business and multimedia applications the users' demand for higher and more predictable quality of service has risen. A first improvement to offer better than best-effort services was made by the development of the integrated services architecture and the RSVP protocol. But this approach proved only suitable for smaller IP networks and not for Internet backbone networks. In order to solve this problem the concept of differentiated services has been discussed in the IETF, setting up a working group in 1997. While RSVP classifies packets according to application flow properties, differentiated services are based on the idea that the user negotiates a service profile with his Internet service provider (ISP) for specially marked packets and then transmits marked packets over the ISP network. A further significant difference to RSVP consists in the fact that for scaling reasons the service profile is only negotiated and policed for a set of aggregated flows. This article gives an overview of the activities of the IETF with regards to differentiated services and presents several proposals for the implementation of differentiated services.