System information

functions such as voicemail and conferencing being provided through external modules
that may cost thousands of dollars. This topology is illustrated in Figure 22-1.
Figure 22-1. Traditional call center
Such systems will utilize a set of rules for delivering calls to agents through the standard
automatic call distribution (ACD) rules, and will have little flexibility. It will likely be
either impossible or expensive to add remote agents, as the calls would need to be
delivered over the PSTN, which utilizes two phone lines: one for the incoming caller
to the queue, and another to be delivered to the remote agent (in most cases, the agents
just need to reside at the same physical location as the PBX itself).
These traditional phone systems are slowly being phased out, though, as more people
start clamoring for the features VoIP brings to the table. And even for systems that
aren’t going to be using VoIP, solutions like Asterisk bring to the table features that
once cost thousands of dollars as an included part of the software.
Of course, with the money invested in expensive hardware in traditional systems, it is
natural that organizations with these systems will want to get as much use from them
as possible. Plus, simply swapping out an existing system is not only expensive (wiring
costs for SIP phones, replacement costs for proprietary handsets, etc.), but may be
invasive to the call center, especially if it operates continuously.
Perhaps, though, the time to expand has come, and the existing system is no longer
able to keep up with the number of lines required and the number of seats necessary
to keep up with demand. In this case, it may be advantageous to look toward a hybrid
system, where the existing hardware continues to be used, but new seats and features
are added to the system using Asterisk.
Hybrid Systems
A hybrid phone system (Figure 22-2) contains the same functionality and hardware as
a traditional phone system, with the exception of another system such as Asterisk being
attached to it, thereby providing additional capacity and functionality. Adding Asterisk
to a traditional system is typically done via a PRI connection. From the viewpoint of
the traditional system, Asterisk will look like another phone company (central office,
or CO). Depending on the way the traditional system operates and the services available
490 | Chapter 22: Clustering