Abstract: In a communication network in which terminals (11) are mobile in the network, the mobility must be managed, and in particular the location of the mobile terminal needs to be determined. Networks each have an associated name server (13) and the name server (13) stores a care-of-address for the terminal (11), as well as a permanent address. As the terminal moves from one subnet of the network to another the care-of-address is changed to reflect the current subnet. Therefore, the input of the name of the mobile terminal (11) identifies via the care-of-address the subnet in which the terminal is currently located. The network is divided with domains each with its own name server (13, 14) as the terminal (11) moves from its home domain to a foreign domain, the name server (14) of that foreign domain may be updated with details of the mobile terminal (11) so that any query to the terminal (11) originating in the foreign domain may be resolved within that foreign domain.

Abstract: An SIP/SDP compression method, transmitter (510) and receiver (550) for communicating a message from the transmitter to the receiver by, at the transmitter, removing from the message element (s) thereof and inserting into the message an indication (200) of absence of the removed element (s); and, at the receiver, inserting into a message received from the transmitter element (s) pre-cached at the receiver in replacement for the element (s) whose absence is indicated. This provides a lightweight SIP/SPD compression scheme (LSSCS) that (i) removes the information redundancy generated at the application layer, and (ii) can achieve 100% compression efficiency for the redundant SIP and SDP URL fields.

Abstract: Transmission of voice over internet protocol is achieved in a Universal Mobile Telecommunications System (UMTS) by using a hybrid mode of attach whereby the speech bearer path from a mobile phone (1) is transported to the network controller (4) in circuit-switched mode and from thereonwards in packet mode. The control signalling from the mobile phone (1) is sent over the internet protocol to the core network (9). The invention has the advantage of providing the optimised speech path by using the most appropriate parts of existing circuit-switched and packet-switched domains, thus, enabling voice calls, facsimile transmissions and computer-generated data to be transported over a single data network.