IP Telephony Unveiled
Figure 1-3 illustrates how an IP gateway (often referred to as an IP blade) that
is added to the existing PBX gives those PBX users the ability to place calls over
a company’s IP network from location to location in order to reduce long-distance
charges. Toll-bypass, as this is commonly referred to, is the most obvious beneﬁt
of this type of VoIP deployment.
In Figure 1-3, the IP gateway could easily be a single card that is installed/
integrated into the PBX as are other cards on a PBX shelf. Furthermore, it could
be a card within a data router that currently resides on a company’s IP network.
Either approach (integrated as a card in the PBX or a router) provides
organizations with a cost-effective means for integrating gateways into their
environments. For many companies, reducing long-distance charges has been the
desired state, and upon accomplishing this task, they move on to other projects. In
their minds, their VoIP project is completed.
The Telephone as Client
Many organizations, however, see VoIP as far more than this. More than
simply using the network as transport (or plumbing), many organizations see value
in not only placing voice “trafﬁc” onto the IP network, but also in placing the
actual voice “clients” (the telephones themselves) and new voice applications onto
the IP network. This approach, although technically still VoIP, is commonly
referred to as IP telephony; i.e., deploying a total telephony solution (including
telephones, components, applications, and by extension, users) within the IP
In other words, IPT takes the premise of voice and data integration to its
natural, albeit long-awaited conclusion: new voice clients (telephones, wireless
devices, and desktop software) that, in their basic form, are designed to interface
and interact with an IP network, obeying the rules of the IP network, utilizing its
protocols, managed by its resources, and most importantly, accessing the myriad
of applications that (can) exist on the network.
NOTE Whereas VoIP places voice trafﬁc on the IP network, IP telephony
places voice clients, applications, and trafﬁc on the IP network,
thereby providing a different value proposition.
Chapter 1: Haven’t We Been Here Before?
As shown in Figure 1-4, IP telephony allows phones to be directly connected
to the IP network. A new type of phone, called an IP phone, is designed to
interface directly to the Ethernet switch on the IP network, much like any other IP
device, such as a PC, a laptop computer, or a network printer.
Figure 1-4 IP Phones Connect Directly to the IP Network
So, for the purpose of this book, VoIP is deﬁned as technology that places
voice trafﬁc onto the IP network, whereas IP telephony is technology that places
voice clients and voice applications as well as voice trafﬁc onto the IP network.
Each technology has a different goal, or desired state. The value proposition
provided by IPT is very different than what was described previously for VoIP,
primarily because the desired state for IP telephony is different.
The question most often asked by companies who investigate IP telephony is
a simple one: Why should I put my telephones on the IP network? The simple
answer is because managing one network instead of two (or more) is easier and
more cost-effective, and that is where the majority of applications reside.
Unlike the traditional applications generally associated with voice, this new
breed of applications is different. New applications are being developed quickly,
with fewer resources, and at a lower cost. Instead of developing applications
against a speciﬁc vendors’ proprietary operating environment, IPT allows
organizations to write applications using industry-standard (and widely used) data
languages and protocols. In this new environment, just as data applications are
written using Java, XML, HTML, Visual Basic or other similar tools, so too are
new voice applications. Application development time is reduced from years and
months to days and weeks. At Selsius Systems, we saw this trend develop in front
of our eyes.