tunnel management and control. GTP-C protocol for control signalling between SGSN servers and GGSN supports end- user authentication interacting with a RADIUS server located at the ISP service network or in a corporate network. For this purpose, the GGSN includes a RADIUS client. The optional IPsec function makes it possible to have secure transfer between SGSN and GGSN nodes and between GGSN and external networks. The IPsec may also be used to secure the link between the GGSN node and the network management terminal. The security function also includes the packet filtering options in order to protect against intrusion or denial of service attacks. 6.14.3 E-COMMERCE AND M-COMMERCE SOLUTIONS Micro-payments and protection of m-commerce are important subjects. The security measures include access control, user authentication, signing, data integrity, non-repudiation. 6.14.4 WLAN SOLUTIONS A WLAN security solution should provide transparent mobility and security for mobile users who want to access their company networks. WLANS have basically an inferior protection compared with wired networks. The reason is that radio waves propagate outside the intended area. In non-controlled areas there is a risk of false base stations. The idea could be to attract clients and get hold of their passwords. Thus both clients and infrastructure are unreliable and must be authenticated. On the other hand wireless networks can have a higher availability if the access points have secure positions, and the coverage between access points overlap. Then a lost access point can just result in a handover. To protect for unauthorized access-to-access points many WLAN operators use the function access control list (ACL) in the access points. ACL defines what clients can access the base stations. The basic security solution in WLAN according to IEEE 802.11/802.11b is called WEP 128 (wired equivalent privacy 128), with the ambition to protect against unauthorized connection or eavesdropping. WEP generates secret shared encryption keys that both t