Introduction
In today's society multimedia applications are already playing an important role in the telecom industry and the expectations for the future are even brighter. In the past there was a clear separation between datacommunication and telecommunication, but today they are both merging more or less together. Nowadays the number of fixed workstations exceeds the number of laptops, but this is also likely to change in the future, simply because people are more and more mobile but still want to be able to compute and maintain network reachability. Two techniques to realize mobile computing and networking are the GSM network (indicated as circuit-switched strategy) and Mobile IP (indicated as packet-switched strategy). The question is which one is the best solution for supporting voice, data and video.

Circuit-switched strategy:
Here the starting point is the GSM network. By offering techniques like High Speed Circuit Switched Data (HSCSD) and General Packet Radio Service (GPRS) a telecom provider can offer not only voice but also services like data and video. Since HSCSD -a circuit-switched technology- is quite inefficient the GSM network will evolve towards packet-switched technology provided by GPRS, Enhanced Data rate GSM Evolution (EDGE) or Universal telecommunication system (UMTS).

We have chosen in our report for the packet-switched technology as the best solution to support voice, data and video. In the following section we shall explain why we this.

Packet-switched strategy:
Here we start straight ahead with a packet-switched technology: Mobile IP.
Mobile IP is a protocol enabling the user to communicate with its home network when visiting an foreign network. How it exactly works is briefly described in our report including advanced reading literature as well.

Features Mobile IP:

Mobility
Mobile IP offers the user the opportunity to use his own laptop in a foreign network to go up the internet or his home network. The IP address on his laptop stays the same during the session; a big advantage since we're running out of IP addresses. No new terminal or equipment is needed with Mobile IP. Another advantage of mobile IP is the scope of the traditional internet leading to a world wide coverage and reachability.

Implementation
Because Mobile IP is in fact nothing else than an extension to the traditional Internet Protocol (IP) the major part of the internet doesn't need to be modified in order to implement Mobile IP. Only routers serving one or more point of attachments need to be upgraded, leaving the rest of the internet unaffected. This so called point of attachments are points at which a visitor can plug his laptop in. Companies can reserve special rooms for visitors offering internet access and networking possibilities. Often the upgrading consists of uploading software in the router enabling them to support Mobile IP. Next to routers also Home and Foreign Agent are needed which can be thought of as a couple of servers.

Future perspective
Mobile IP is future proof since it can cooperate with IPv4 and IPv6. Although IPv6 has some properties for supporting mobility still Mobile IP will be needed. Another reason is that the internet will be playing an important role in the transportation of voice, data and video. Besides with more bandwidth and some form of Quality of Service (QoS) it will become more attractive to do so. After all IP is the convergence layer because it is flexible and efficient. It will certainly not be replaced by something else.

Security
For Businessmen far from home but still wanting to be able to receive company information through the internet, IP security is sufficient for guaranteeing security. It can cooperate with Mobile IP and performs authentication and encryption of the packets.

Latency
A disadvantage of Mobile IP is the latency due to the redirection mechanism from the Home Agent to the Foreign Agent. In a small local network this latency is about tens of milliseconds but for a world wide large network like the internet it’s more likely to be a couple of seconds. However, Route Optimization Mobile IP allows a reduction in the delay by letting the mobile user communicate directly with the correspondent node (a person with whom the mobile users communicate). The Home Agent is still needed in case of initialization and as back-up.

Wireless
Since Mobile IP is a layer above the data link layer it is capable of functioning together with technologies like WLAN, DECT, GPRS and other data link layer protocols. In cellular networks Mobile IP offers a handoff rate of once per second. The transfer rate of Mobile IP depends on the underlying data link protocol (GPRS: ~115 kb/s, DECT: maximum 552 kb/s  and WLAN: maximum 2Mb/s). Of course when better and faster data link layer protocols are deployed in the future Mobile IP will still be compatible. Cellular wireless networks have a much too big end-to-end latency for making real-time running smoothly, but with more bandwidth in the wireless link and the internet backbone or fixed links the latency problem can be reduced to acceptable numbers.

Conclusion
The packet-switched strategy is better than the circuit-switched strategy. The investment costs are lower, and with sufficient bandwidth and fast data link layer protocols Mobile IP can offer voice, data and video with reasonable quality. With the future bringing more and more bandwidth and Quality of Service real-time applications will be transported through the internet. Since mobile computing and networking will increase there is a need to maintain reachability. Mobile IP is right now the only protocol on the internet providing this need.