dar and contact list that the user might occasionally access. The need for keeping this data in sync with the other data sources is an absolute requirement in order for the devices to be of their greatest value, and for the user to work efficiently. 5.6 ECONOMY OF SERVICE BY MEANS OF CACHING A new dimension in network design is introduced by content-based networks. In order to save capacity in the network modern cache systems can be used. Caching is a type of middleware function. When surfing you often don't know the location of the 'B-subscriber' (the source). The content can be web pages, e-business, bank services, streaming video, broadcasting etc. Considering the traffic load the source should be as close as possible to the surfer. Such source could be an intermediate cache-type storage in a mirror server at the edge of the network. In order to perform intermediate storing, the various services must be discriminated. This means that you have to enter layer 4 in the Internet. Content-based 'layer 4 switches' can direct traffic to the cache to be stored there for a time, which could vary from seconds to hours. News has a fairly long storage time, despite the fast ageing process. Information with high requirements on security, such as a bank account balance not stored. An ordinary web page can contain about 50 objects, text, figures etc. The content view opens up for content networks with different QoS and content server nodes. Figure 5.10 illustrates a content-based view of a small network. 5.7 ECONOMY OF SERVICE BY MEANS OF SAVING BANDWIDTH The Internet explosion and the intra-company business traffic have been instrumental in a process towards wideband and broadband services offerings. See Figure 5.11 which relates to the fixed networks. However, there is normally no linear correlation between bandwidth and revenue. It should be noted that there are several ways to fulfil bandwidth requirements of the original source. This means that it is difficult to define a bandwidth need as it appears in the transmission