7.5.5 DIFFERENTIATED SERVICES More text about differentiated services (Diffserv) can be found in Chapter 12. What follows here is just a brief introduction. Essentially, differentiated services specify the transfer priority of a packet as it passes through each network device on its journey through the network. In order to allocate this priority, differentiated services marks the packets with a code point value, called the DiffServ code point, which is used by network devices such as routers to determine the per-hop behaviour (PHB) treatment. Diffserv does not give any guarantees. It is like travelling by train without knowing when you will arrive. The standard is a compromise between reservation and prioritization. (you travel faster than packets with a lower priority). Diffserv is considered a scalable technology that can offer differentiated services for various needs in large networks. 7.5.6 MPLS MPLS and a development of MPLS called generalized MPLS are further dealt with in Chapter 12. What follows here is an introduction. See Figure 7.19. MPLS (multi-protocolo label switching) introduces connection-oriented label switching mechanisms inside the otherwise connectionless IP technology. Switch according to label Conversational class, Remove incoming label, what LSP provides such QoS? Insert a new one according to calculated LSP Need for new LSP? (for aggregate traffic) Label switched path, LSP PSTN/ISDN) 140.20.10.50 Ex WCDMA RAN Internet intranets MPLS signalling 140.20.10.20 to set up LSP, Topology based e.g RSVP-TE, routing protocols LDP, CR-LDP e.g. OSPF, OSPF-TE (present on all links in the figure) Figure 7.19 MPLS terminology and way of working Quality of Service MPLS offers dynamic bandwidth allocation, traffic engineering, scalable IP over ATM support and support for VPNs. MPLS introduces the concept of label-switched paths (LSP) for both individual aggregated traffic streams. Separate LSPs are used to serve flows with different QoS requirements. LSPs are set up between media gateways based on topolog