in turn determines the complexity of the networking device. Figure 17.6 Classification memory overheads. Making Telecoms Work 17.9.1 Summary - Telecom Cost Complexity Telecom costing has always been a complex process involving amortisation of fixed facilities with a life span of 50 years or more (think telegraph poles and traditional telephone exchanges). Universal service obligations and access guarantees have always implied a substantial over- provisioning of access and network bandwidth. 17.9.2 Popular Myths - Packet is Cheaper The transition from circuit-switched to packet-routed networks has been promoted as a mech- anism for improving network and transmission bandwidth multiplexing efficiency that in turn is supposed to deliver a decrease in the cost of delivery measured in euroherz or dollarherz or eurobytes or dollarbytes of network transmission bandwidth. Multiplexing efficiency is dependent on buffering. Buffering has two cost components - the cost of the memory and processor bandwidth needed to store, manage and prioritise buffered packet streams and the (largely hidden) cost of supporting differentiated classes of service. This cost is dependent on the offered traffic mix - conversational traffic costs more to deliver than best effort because it cannot be buffered. This is of course only true if the multiplexing efficiency of buffering exceeds the cost of overprovisioning transmission bandwidth beyond the point at which buffering would no longer be required. If a significant percentage of offered traffic is real time/conversational, the assumption of a multiplexing gain from buffering is invalid. Additional network efficiency is supposedly achievable by deploying flexible end-to-end routing. Again, any efficiency gain achievable is directly dependent on the offered traffic mix. If a significant percentage of offered traffic is real time/conversational, the assumption of a multiplexing gain from routing flexibility is invalid. The amount of bandwidth used increases as the number of hops increase and/or