Current communication infrastructures comprise fixed networks (e.g. Ethernet and
ADSL), mobile Wide Area Networks (e.g. GPRS and UMTS), Wireless Local Area
Networks (WLAN) and their associated terminals. Services supporting all kinds of
media, such as voice, video and data, are offered over these infrastructures by an increasing number of providers. Examples are voice over IP provided by telephony providers, conferencing services and multimedia streaming. Though these communication infrastructures have capable functionality, they fail to meet obvious upcoming
user requirements: users are technology agnostic, they want to have universal access
to their services, and their services should be adapted according to the context and/or
their personal preferences [16]. In order to meet these user requirements, the following system requirements must at least be imposed on a supporting infrastructure. The
first is seamless mobility, which includes hand-overs to other terminals, to other access networks as well as to other administrative domains