Until UC stabilizes into a few configuration profiles, each case will likely be unique. A mix of hardware vendors and carriers will generate more permutations and combinations than any book could itemize reasonably. Setting up a gateway, session border controller, or call control server is different for each device. Good vendors provide written instructions and user manuals that consist of thousands of pages of detailed references to their command line interfaces, web portals, or SNMP MIB extensions.
That amount of detail doesn't contribute to the broad understanding that is the goal of this book. What follows is common across all situations.
Digital PBXs in smaller sizes often mount on the wall in a closet that has only nominal air conditioning from an office environment. Internal batteries provide backup power for phones, which demand little current when idle. Analog phones draw no current when on hook.
VoIP installations, particularly with many UC services, resemble larger PBXs installations or small data centers in requiring rack space for servers and greater attention to cooling. Backup power is external to the servers, and needs higher capacity batteries than those inside a PBX. IP phones are computers that need constant power to hold up the processor and display, in the range of 8 to 15 watts each.
Planning for a migration to UC must consider all of these physical factors as well as the configuration and ...