hile public IP addresses are those that are seen by other network elements and can be changed. Parameters related to the IP addresses and routing tables should be defined. DETAILED PLANNING Synchronisation Parameters Parameters related to the synchronisation of ATM cross-connections, such as definition of the clock source or synchronisation source, should be defined, along with the priority of these sources if there is more than one clock. 8.6.4 Summary of ATM Planning Features A detailed understanding of ATM technology is necessary for ATM planning. ATM planning constitutes attention to the definition of: the types of traffic the VP and VC connections the number of VPs and VCs (i.e. VPIs and VCIs) VP and VC cross-connections physical, VP and VC connection parameters. Some of these aspects are shown in Figure 8.12, in which 'grey' lines depict the physical paths, thick black lines show the VPCs, and thin black lines show the VCCs. Site6 26.56 MSCO 3/ Site0 Site4 Sitel Site3 Site2 Site5 Figure 8.12 ATM planning All these aspects of ATM planning are complicated, especially for a large network. In the network rollout phase, this process becomes complicated and tedious. For this reason, good ATM planning tools are used. 3G TRANSMISSION NETWORK PLANNING AND OPTIMISATION 8.6.5 Synchronisation Plan The design of the synchronisation plan for a 3G network is quite similar to that for a 2G network. The clock moves from the MSC to the BSC, from the BSC to the BTS, and from the BTS to the other network elements. The external clock (usually the primary reference clock, PRC) is applied to the MSC, which then distributes it further to the MGW, which sends it further to the RNC; and finally it is distributed to the base stations and other network elements. This is depicted in Figure 8.13. Clock Figure 8.13 Synchronisation hierarchy It is important to remember that, even in 3G networks, there might be some network elements that belong to a 2G network. In such cases, the ATM parameters need to be observed very carefully, as the 2G