ween Company P and Company Q. Chapter 12: Case Studies 265 San Jose, CA CUCM Cluster H.323 d I b Conferencing H.323 Server H.323 Company Q H.323 World Wide Gatekeeper Company P Call flow Any Cluster Figure 12-2 SIP Trunk Connectivity We talked to Company P to find out the motivation of this migration process. Initially we thought it wanted to replace the PSTN links to save toll costs, but money was not the only factor. It also wanted to achieve the following things from this migration process: One conferencing platform for all employees. It has multiple conferencing servers in different locations. It wanted to shut them down and use a single unified solution for everyone. Multiple failover sites. The SP offered redundant services all over the world. So, the enterprise wanted to connect more than one location via SIP trunk, which is conven- ient for it. Active. Active Voice Cluster between conferencing servers located in Mountain View, California and London, England. Audio failover between the two locations. Global disaster recovery capabilities for main sites. Create user distribution based on load and the proximity to a conferencing server. Figure 12-3 shows the redundancy between two locations. 266 SIP Trunking Company P Company Q San Jose, CA CUCM Cluster Mountain View, CA H.323 CAP NET Europe Europe London, UK CUCM Cluster H.323 Initial Meeting Prompt RTP Stream Figure 12-3 SIP Trunk Redundancy Migrating a small system from few T1s/E1s to a SIP trunk is easy; but, when you need to handle thousands of users, it becomes challenging. Although it planned for many things, it could not achieve the target within the given time frame. It planned the whole migra- tion in multiple phases, and the process is still going on. Here are the few things it could not achieve while we interviewed employees to get the status of the project: Did not fit all internal users. The size of the company is SO big that it could not bring everyone under the same platform. So, it has to keep internal conferencing servers to accommodate the