necting gateway points between the networks. The translations take time (in this case it could add to more than 100 ms), which adds to the total delay. This means a reduced quality for the interactive real-time services, such as telephony and interactive multimedia (like video conferences). Delay is not a problem for data communication, where a gateway might translate from one mail format to another one or from one ASCII table to another. Instead the readability might be affected. 7.4.3 LAYERED NETWORKS The horizontal network gives us increased freedom of choosing technology in the various layers. It is cheaper to manage one network than many. But there are two sides of the Quality of Service Billing Varying terminal capabilities, Telecom business web services a new QoS risk User requirements Introduction of Scarce traffic extra overhead, and control Service IPsec tunnels resources Service Service, security, QoS, Service layer management TCP/IP impact: Numbering Dimensioning Introduction of delays Charging Routing Control layer Dependability and delay variations Signalling by switch/router. Mobility management Introduction of Inter-system retransmission by roaming, hand over TCP slow start Switching Frequency mechanism Organization Transmission Traffic resources Synchronization in connectivity layer Delays, jitter, radio Introduction transmission impact, of slip might BER vs compression cause packet loss Figure 7.7 Possible threats to QoS from other FPs coin. The introduction of a new, widely layered approach gives initially an increased complexity and a poorer performance compared with tailored solutions. When combining 'ordinary' layering with for example an IPsec tunnel, carried over IP, carried over frame relay, over ATM, on SDH, using WDM on optical fibres, what will the overall quality and efficiency become? What about QoS control? Is a kind feedback possible from underlying layers to the application level? SLA between layers? In Chapter 12 the standard GMPLS is presented, with a kind of common overall appr