esponse UMTS bearer service with negotiated QoS RAB = Radio access bearer, RRM = Radio resource management Figure 7.21 RAB negotiation for the UMTS access network the network checks the available resources and the user type of subscription and then responds. The user either accepts or rejects the offer. The properties of a bearer service affect the price of a service. See Figure 7.21. At the start of UMTS service not all of the QoS functions will be implemented, and therefore delay-critical applications such as speech and video telephony will be carried on (more expensive) circuit-switched bearers, Later, it will be possible to support delay- critical services transported as IP packet data with QoS functions. 7.7.2 QOS HANDLING Another UMTS QoS issue is the choice of QoS enabler for IP traffic (RSVP, MPLS etc.), ATM service classes or frame relay. The applications and services are divided into four different QoS classes according to Chapter 5 and beginning of this chapter. The subscriber QoS profile, if any, is stored in the HLR. It is possible to store a differentiated QoS. The SGSN server, the MGW and the GGSN are responsible for QoS negotiation and handling. For a specific call the QoS that is requested from the application or the user is mapped to the QoS profile that is negotiated at PDP context activation. The PDP QoS is mapped to the QoS mechanisms of the concerned networks, such as: DSCP values in Diffserv networks, MPLS labels in MPLS networks, ATM service classes, frame relay traffic parameters, etc. See Figure 7.22. Understanding Changing Telecommunications - Building a Successful Telecom Business Other network Terminal if any Content Content Service network, if any Applications Service enablers Service enablers (Mobility), QoS, security management Access F2 E1D3 Core connectivity Different DiffServ or MPLS External QoS channel mechanisms, types serv. Ex RSVP For example AAL2 in early releases Figure 7.22 Example of chosen QoS enablers in 3GPP R99 Subscriber QoS profile Other network (CPN, If any) Cont