communication link for the data transmission in the embodiment described the required information is requested by the first sgsn 203 as part of the gprs attach for the mobile radio subscriber appliance 201 attach accept message 221 and the required information is also transmitted to the first sgsn 203 as part of the gprs attach attach complete message 222 in another embodiment the required information is requested and transmitted as part of a routing area update in a similar fashion to the attach request message 220 the mobile radio subscriber appliance 201 transmits a routing area update request message as part of a routing area update procedure this is described in 3gpp ts 24 008 v6 7 0 3rd generation partnership project technical specification group core network mobile radio interface layer 3 specification core network protocols stage 3 release 6 the first sgsn 203 responds to the routing area update request message with a routing area update accept message which is essentially in a form as in 3gpp ts 24 008 v6 7 0 3rd generation partnership project technical specification group core network mobile radio interface layer 3 specification core network protocols stage 3 release 6 but in this embodiment contains the request to the mobile radio subscriber.