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Bandwidth Requirements
One common misconception about VOIP is that it is a bandwidth hog, when,
in fact, voice is a very efficient type of traffic. Voice compression standards
like G.729 (8:1) and G.723 (10:1) are used to minimize the bandwidth required
for voice. G.723, for instance, is the maximum compression rate and requires
only 5.3K bps (plus an added 7-8K bps for IP overhead). Even at maximum
compression, your VOIP solution will still provide near toll-quality voice.
As a rule of thumb, 14K bps of bandwidth per call is ideal. This includes
the compressed voice packet and the IP overhead. To determine total VOIP
bandwidth needed per location, take the number of VOIP channels being used
and multiply by 14K bps. Then double this number to accommodate for both
voice and data traffic.
It should also be noted that bandwidth is used only when someone is speaking.
A silence suppression/Voice Activation Detection (VAD) feature is an option
that frees unused call bandwidth for data traffic. This is significant,
since callers are usually silent for 60 percent of the call.
Interoperability
Standards are still emerging that ensure VOIP features work with different
vendor solutions. The H.323 standard is the one most widely deployed and
is the only approved protocol adopted by the International Telecommunications
Union (ITU). The H.323 standard provides support for audio calls to other
H.323 clients, gateways, gatekeepers and conference servers. Another emerging
standard is the Session Initiation Protocol, or SIP. Look for products
that are adopting these two standards.
VOIP Solutions
From the wide variety of VOIP solutions available today, the one you select
depends on the size of your business, the level of networking expertise
available, the amount of integration with legacy equipment, and the level
of voice quality you require.
Routers
Router solutions usually replace an existing network router and keep voice
and data all in a single box. However, this solution requires networking
expertise, and can be costly to install, while placing network services
at risk during deployment and maintenance.
VOIP Server Cards
VOIP server cards can be an economical VOIP solution. However, they must
be compatible with the server and operating system and installations can
be complex.
IP-based PBX
The IP-based PBX is usually software running on a computer based server.
However, it often requires a forklift upgrade of the existing PBX, or at
a minimum, an extensive software and/or hardware upgrade. An IP-based PBX
is typically marketed to new installations where no legacy system is in
place.
PC-based Telephony
PC-based telephony software is by far the cheapest VOIP solution, but it
is also the clumsiest. It requires users to make phone calls using their
PC instead of a phone. This usually involves user training and an investment
in speakers and microphones for each PC. Plus, many users complain that
voice quality for this solution is not adequate for business communications.
IP Gateways
An IP gateway, like Multi-Tech's MultiVOIP, is often the most suitable
VOIP solution for small to midsize businesses and remote sites. It does
not disturb your existing data infrastructure because it simply drops into
the Ethernet network. Furthermore, it operates alongside existing PBXs
or other phone equipment to extend voice capabilities to remote locations
or users. An IP gateway requires only a minimal investment in product,
installation, and user training.
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