trol with inter-domain re- source negotiation and supported by QoS signalling and SLAs. Mapping between QoS techniques is necessary, for example transfer of a particular Diffserv behaviour aggregate to an MPLS FEC (forward equivalence class). Provided Diffserv is used in a user-operator interface the following characteristics could be regulated: traffic profile, classification and marking rules, network behaviour for specific DSCP values. PDP context shows a stage of QoS handling. 15.8 PDP CONTEXT ACTIVATION FOR CONNECTION TO A DATA NETWORK order for the user to be able to transfer data, a packet data protocol (PDP) context must be activated in the mobile station, SGSN and GGSN. The user initiates this proce- dure, which is similar to logging on to the required destination network. The process is illustrated and described below. The user initiates the logging on process, using an application on the PC or mobile station. The mobile station requests sufficient radio resources to support the context activa- tion procedure. Once the radio resources are allocated, the mobile station sends the activate PDP context request to the SGSN. This signalling message includes key information about the user's static IP address (if applicable), the QoS requested for this context, the access point name (APN) of the external network to which connectivity is requested, the user's identity and any necessary IP configuration parameters (e.g. for security reasons). After receiving the activate PDP context message, the SGSN checks the user's sub- scription record to establish whether the request is valid. Interconnection If the request is valid, the SGSN sends a query containing the requested APN to the DNS server. The DNS server uses the APN to determine the IP address of at least one GGSN that will provide the required connectivity to the external network. The GGSN IP address is returned to the SGSN. The SGSN uses the GGSN IP address to request a connection tunnel to the GGSN. Upon receiving this request the GGSN completes the establi