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VoIP (Voice over Internet
Protocol)
This guide presents VoIP articles, tutorials, examples, tips,
tools, white papers, expert advice and more to pump up your VoIP
know-how quickly.
TABLE OF CONTENTS
What
is VoIP?
How
does VoIP work?
Circuit switching vs. packet switching
H.323
and SIP
PBXs,
IP-PBXs and hybrid systems
Advantages
and disadvantages
Hosted
vs. in-house VoIP
Regulatory
issues/E911
Securing
VoIP
QoS
More
Learning Guides
What is
VoIP?
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VoIP (Voice over IP ) is a term used in
IP telephony for a set of facilities for managing the delivery
of voice information using the Internet Protocol (IP). In general,
this means sending voice information in digital form in discrete
packets rather than in the traditional circuit-committed protocols
of the public switched telephone network (
PSTN). This guide will help you understand the technology
behind VoIP. In addition, this guide delves into key VoIP issues
such as; security, regulations, advantages and disadvantages,
outsourcing and
QoS.
How does
VoIP work?
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VoIP works by converting your analog voice into data packets
(digital format), sending them over your existing data network and
reconverting them to voice at the destination. The benefit of a
digital format is that it can be controlled. It can be routed,
modified, condensed, expanded and saved. Digital signals are also
more noise tolerant than analog. This section will help you to
understand the basic processes and functionalities of VoIP.
Circuit switching vs. packet switching
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Circuit switching was developed for analog-based telephone
systems. Circuit switching has been used extensively for the public
switched telephone network (
PSTN). In
circuit switching, users have exclusive use of a connection
until the conversation is over and the connection is released. In
packet switching, messages are divided into
packets, and many users share access to a circuit by taking
turns putting their packets onto the channel. Breaking
communication down into packets increases capacity. This type of
communication between sender and receiver is known as
connectionless (rather than dedicated). Most traffic over the
Internet uses packet switching.
H.323 and
SIP
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The Session Initiation Protocol (
SIP) is an Internet Engineering Task Force (IETF) standard
protocol for initiating an interactive user session that involves
multimedia elements such as video, voice, chat, gaming, and virtual
reality.
H.323 is a standard approved by the International
Telecommunication Union (ITU) in 1996 to promote compatibility in
videoconference transmissions over IP networks.
PBXs, IP-PBXs and
hybrid systems
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A
PBX is a telephone system that switches calls between
enterprise users on local lines while allowing all users to share a
certain number of external phone lines. The main purpose of a PBX
is to save the cost of requiring a line for each user to the
telephone company's central office. An
IP PBX is a private branch exchange that switches calls between
VoIP users on local lines while allowing all users to share a
certain number of external phone lines. A typical IP PBX can also
switch calls between a VoIP user and a traditional telephone
user.
Many major vendors are offering hybrid voice systems that
combine elements of VoIP and public switched telephone network
(PSTN) systems. These new hybrid systems may give enterprises an
opportunity to benefit from VoIP cost savings by combining the
traditional telephony hardware with new technologies.
Advantages and disadvantages
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VoIP technologies can reduce telecommunication and networking
costs and offer new voice capabilities. However, it is important
that you understand the advantages and disadvantages of VoIP before
you begin an implementation. Some advantages include; reduction of
intra-office toll charges, lower hardware costs, productivity
benefits for remote and traveling workers, improved security and
reduced system downtime. Some of the risks involved with a VoIP
project can include; quality of service/performance issues, cost
and resources needed for user and administrative training and
proprietary vs. open systems interoperability. This section takes a
closer look at the good, bad and ugly of VoIP.
Hosted vs.
in-house VoIP
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Many carriers are now offering low-maintenance hosted VoIP
services for enterprises. Is hosted VoIP right for your company?
There are many things to consider when making the choice between
hosted and in-house VoIP. Quality of service (
QoS) issues, hardware stability, network monitoring and
latency are all very important factors to look at. This section
will help you better understand the pros and cons of both
options.
Regulatory
issues/E911
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In many countries, VoIP is illegal. In many others (including
the United States) telecom regulations are changing faster than you
can say 911. Recently, the Supreme Court ruled to uphold FCC
regulations permitting cable operators to block rivals from using
their infrastructures. This could hurt VoIP providers and increase
costs significantly. In addition, the FCC has set a mandate for
VoIP providers to get E911 services up and running soon. This
section will help you sort through the intricate web of VoIP
regulations.
Securing
VoIP
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Deploying effective VoIP security is challenging. Since
telephony traffic must travel over the IP network between gateways,
stations, servers and proxies, there are plenty of places to
attack. The list of possible threats includes; toll fraud,
impersonation, hijacking of calls, session replay, media tampering,
denial of service and
SPIT. This section will help you avoid some security
pitfalls.
QoS
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A big component of VoIP infrastructure is effectively deploying
a Quality of Service (QoS) model. QoS is the idea that transmission
rates, error rates and other characteristics can be measured,
improved, and to some extent, guaranteed in advance. QoS is of
particular concern for the continuous transmission of
high-bandwidth video and multimedia information. There are many
ways to ensure
QoS. This section will help you decide which QoS method is
right for you.
More
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