block diagram of fig1 the various elements of the network and their functions may but need not be those described in the general packet radio service gprs service description stage 2 3g ts 23 060 version 3 2 1 published by the 3 rd generation partnership project www 3gpp org and which is hereby incorporated by reference the elements and their functions may instead be those described in an earlier or later version of the 3g ts 23 060 specifications or may be those of any other known packet switched wireless communications network the description of network elements and their functions hereby incorporated by reference is merely a non limiting example of packet switched wireless communication networks several elements of the example network illustrated in fig1 are particularly relevant to this invention the mobile terminal mt commonly referred to as a cell phone or mobile phone is only one possible part of user equipment ue typically terminal equipment cte used together with a mobile terminal mt constitutes user equipment ue any ue may be utilized in conjunction with this invention so that it operates or can be programmed to operate in the manner described below the umts terrestrial radio access network utran and the base station system bss in gprs manage and control the radio access between the network and a number of ues the serving gprs support node sgsn is the node that serves the ue at pdp context activation the sgsn establishes a pdf context used for data forwarding purposes the gateway gprs support node ggsn is the node accessed by the packet data network due to evaluation of the pdp address it contains routing information for attached gprs users the routing information is used to tunnel protocol data units pdus to the sgsn the sgsn and ggsn.