jor resources: radio resources at the air interface and transport resources in the terrestrial radio access network. Accordingly, there are specific resource management functions for organizing each resource. The following subsections introduce the associated resources management functions for each type of the resource in the UTRAN. 3.3.4.1 Radio Access Bearer (RAB) Before addressing the radio resource management functions, it is necessary to introduce the Radio Access Bearer (RAB). When one user requests a connection, this connection requires resources to be dedicated in order to transfer the information flows across the UMTS network. The RABs are the UTRAN resources, which are dedicated to transport user information for particular user connections across the UTRAN network, and it can be viewed as a service, which UTRAN provides to CN and UE. Radio Access Bearer Service The Radio Access Bearer Service is characterized by a set of attributes such as traffic class, maximum bit rate, guaranteed bit rate, maximum SDU size, etc., which define that particular traffic aspect or Quality of Service profile of that particular application or service [3GP06c]. Traffic classes are explained in Table 3.1. The main distinguishing factor between these traffic classes is how delay sensitive the traffic is: The Conversational class is for traffic which is very delay sensitive, while the Background class is the most delay insensitive traffic class. Both the Conversational and Streaming RABs require a certain reservation of resources in the network, they are mainly intended for carrying Real-Time (RT) traffic flows, such as video telephony and audio/video streams. The Interactive and Background RABs are so- called Best Effort (BE), i.e. no resources are reserved and the throughput depends on the load in the cell. They are mainly used for carrying Internet applications like web, email, and ftp. Due to less stringent delay requirements, compared to Conversational and Streaming classes, both Interactive and Background RABs provide bet