The UMTS provides end-to-end services.

An end-to-end service has a certain QoS provided to the user by the network. To realize a certain network QoS, a bearer service with well-defined characteristics and functionality must be set up from the source to the destination of the service.

The UMTS bearer service has two parts: the radio access bearer (RAB) service and the core network bearer (CNB) service.

The RAB service provides a secured transport of signaling and user data between the MT and CN Iu edge node. The core network bearer service of the CN connects the CN Iu edge node with the CN gateway to the external network.

UMTS defines four different QoS classes. These are conversational class, streaming class, interactive class, and background class. The main distinguishing factor between these classes is how delay sensitive the traffic is.

The conversational and streaming classes are mostly used to carry real-time traffic flows. Real-time services, such as video telephony and speech are the most delay sensitive applications. They require data streams to be carried in conversational class. Streaming class carry lesser delay sensitive traffic.

The interactive class and background class are mainly used for traditional applications such as www, email, Telnet, FTP, and news. These applications have less stringent delay requirements compared to the conversational and streaming classes.

The main difference between the interactive and background class is that the interactive class is mainly used for interactive applications (e.g., e-mail or interactive web browsing), and the background class is meant for background traffic (e.g., background of e-mails or to background the downloading).

The defined UMTS bearer attributes ranges and radio access bearer attributes ranges and their relationship for each bearer class is summarized in Tables 1 and 2.