 isochronous traffic is identified at the entrance node (edge router or MGWs), eventually marked and allowed to flow through a special path, where the delay may be kept within acceptable values. Differentiation of traffic at certain entrance points is therefore a common procedure on modern networks. For all differentiation of traffic (quality, security etc.) there is a need for a policy. A policy server is a common solution. The server provides mapping facilities for services, business and network configuration concepts. QoS bearer service provision, secure tunnel configuration or IPsec configuration Telecom Management - Operations DSCP - Differentiated services code point 'DS byte' DSCP (6 bits) IP version 4: 'Type of service' field IP version 6: 'Traffic class' field VoATM Figure 16.23 Some QoS standards and issues can easily be specified in high-level terms. Example: 'Provide GOLD service for all SAP traffic from site A to site B'. The policy server creates logical rules on how this can be realized in the network, permanently or temporarily. If a particular link fails, or QoS demands are not met under normal conditions, under- lying network resources can be reconfigured, or low-priority connections can be dropped. As described in Chapters 7 and 12, RSVP, MPLS and Diffserv are important QoS standards. RSVP, through resource reservation, MPLS through label switching or DiffServ with a defined per hop behaviour in each router, have the same goal, which is to open differentiated lane for voice/video communications through a possibly congested area (the heavy traffic highway assigned to best-effort traffic). The combination of IP and ATM contributes to QoS as IP can rely on the powerful ATM QoS handling capabilities. However, new standards offering interesting QoS alternatives are evolving for IP networks, such as MPLS and GMPLS. Thus, telecom management plays a very important role in the satisfactory development of the network QoS. Performance management may lead to different traffic engineer- ing initiatives and 