Another option is an integrated WAN link to a site with older PBX equipment that is already scheduled for replacement. The pilot can use optional routes through the PSTN as a backup measure, however. With pilot sites selected, an accurate network assessment helps managers decide where to add bandwidth capacity, packet-voice interfaces, and software features to prepare the infrastructure for carrying voice traffic. The next step is to add voice-enabled routers at both ends of the link. Most Cisco routers support packet voice, so enterprises may be ready to start the test.
Cisco supports three packet voice technologies.
It may discover that the link is already running at or near capacity, so increasing capacity ensures that it can also handle the expected volume of voice calls. Then it adds voice interfaces to the routers at each end of the link. The company may also decide to add voice compression techniques that reduce per-call bandwidth consumption. At this stage, the PBX is still a central component of the telephone network, so an enterprise requires a gateway between the traditional PBX network and the packet network. In this stage, data and voice networks combine only over the interoffice WAN link.