ring, the various services must 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 is 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 system. Transfer of high quality pictures can for example be solved either by high bandwidth (bits/s) or by using efficient codecs with compression algorithms (see Figure 5.12). More- over, if the user data is not transferred in conversational or streaming modes, time is a third parameter to play with. WAP provides faster communication through compressed and encoded data and headers. A very efficient header compression is offered by the standard robust header compression Services Examples of traffic situations FTP traffic 634 Mbps SMTP traffic 30 Kbps FTP traffic 8 Mbps HTTP traffic 45 Kbps Figure 5.10 A content-based view 1. Voice (fixed PSTN developing towards cellular PLMN) 2. Dialled up Internet 3. Broadband Internet 'Always on', etc. Figure 5.11 Driving applications in the fixed network (ROHC). See Figure 5.12. The ROHC can be used for services such as VoIP, video ov