The IETF has standardized two frameworks to meet the demand for Quality of Service (QoS) support: the Integrated Services (IntServ) and Differentiated Services (DiffServ) architectures. DiffServ defines an architecture for implementing scalable service differentiation in the Internet. The differentiated service is obtained through traffic conditioning and packet marking at the edge of the network along with simple differentiated forwarding mechanisms at the core. DiffServ achieves scalability by aggregating traffic at network boundaries and marking accordingly each packet header with an adequate codepoint. Packets containing the same codepoint receive an identical forwarding treatment on nodes along their path, thus eliminating the need of state or complex forwarding decisions within the network core. In this chapter, we briefly describe the DiffServ model and its several components.