With the evolutions of UMTS radio access technologies like HSPA, HSPA+ and LTE, which are aiming to increase the system capacity and the user peak throughput for packet based services, the capacity bottleneck mainly lies in the transport network as the transport resources on the radio access side are scarce. These high speed radio access technologies are optimized only regarding the radio resource usage and are mostly defining strict delay requirements for the transport network. In order to achieve optimal radio resource utilization, the congestion in the transport network has to be avoided. Moreover, the transport network is not dedicated to high speed radio access traffic only, it is a shared resource used to carry fixed traffic (fixed mobile convergence) as well as Rel99 traffic. Based on these considerations, the transport network should be dimensioned carefully in order to support different traffic and as well guarantee their strict delay requirements over the transport network and to reduce the probability of network congestion. Usually, in order to guarantee the stringent delay and loss requirements over the transport network, various functions can be taken within the transport 1 Introduction network for managing the transport resources: traffic control, resource control, routing optimization and traffic engineering. These functions will cause considerable impact on the performance of the transport network, which are discussed in detail in Chapter 4. They also need to be carefully considered for the dimensioning of the transport network. In order to achieve optimal transport resource usage various transport solutions have been adopted: service prioritization, hybrid backhaul, migration from ATM to Internet Protocol (IP) transport, etc. These solutions are aiming to increase system resource usage and at the same time decrease the transport costs by improving the multiplexing gain on the links, e.g. with service prioritization and path separation, and by migrating to IP transport, like changing to full IP UT