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Woosh Phone New Zealand |
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Voice over Internet Protocol, also
called VoIP, IP Telephony, Internet telephony, Broadband
telephony, Broadband Phone and Voice over Broadband is the
routing of voice conversations over the Internet or through any
other IP-based network.
Protocols which are used to carry voice signals over the IP
network are commonly referred to as Voice over IP or VoIP
protocols. They may be viewed as commercial realizations of the
experimental Network Voice Protocol (1973) invented for the
ARPANET.ce providers. Some cost savings are due to utilizing a
single network to carry voice and data, especially where users
have existing underutilized network capacity they can use for
VoIP at no additional cost. VoIP to VoIP phone calls on any
provider are typically free, whilst VoIP to PSTN calls generally
costs the VoIP user.
There are two types of PSTN to VoIP services: DID (Direct Inward
Dialing) and access numbers. DID will connect the caller
directly to the VoIP user while access numbers require the
caller to input the extension number of the VoIP user. Access
numbers are usually charged as a local call to the caller and
free to the VoIP user(citation/example needed) while DID usually
has a monthly fee. There are also DID that are free to the VoIP
user but is chargeable to the caller .
Functionality
VoIP can facilitate tasks that may be more difficult to achieve
using traditional networks:
Incoming phone calls can be automatically routed to your VoIP
phone, regardless of where you are connected to the network.
Take your VoIP phone with you on a trip, and wherever you
connect to the Internet, you can receive incoming calls.
Free phone numbers for use with VoIP are available in the USA,
UK and other countries from organizations such as VoIP User.
Call center agents using VoIP phones can work from anywhere with
a sufficiently fast and stable Internet connection.
Many VoIP packages include PSTN features that most telcos
normally charge extra for, or may be unavailable from your local
telco, such as 3-way calling, call forwarding, automatic redial,
and caller ID.
Mobility
VoIP allows users to travel anywhere in the world and still make
and receive phone calls:
Subscribers of phone-line replacement services can make and
receive local phone calls regardless of their location. For
example, if a user has a New York City phone number and is
traveling in Europe and someone calls the phone number, it will
ring in Europe. Conversely, if a call is made from Europe to New
York City, it will be treated as a local call. Of course, there
must be a connection to the Internet e.g. WiFi to make all of
this possible.
Users of Instant Messenger based VoIP services can also travel
anywhere in the world and make and receive phone calls.
VoIP phones can integrate with other services available over the
Internet, including video conversation, message or data file
exchange in parallel with the conversation, audio conferencing,
managing address books and passing information about whether
others (e.g. friends or colleagues) are available online to
interested parties.
Drawbacks
VoIP technology still has a few shortcomings that have led some
to believe that it is not ready for widespread deployment.
However, many industry analysts predicted that 2005 was the
"Year of Inflection," where more IP PBX ports shipped than
conventional digital PBX ports. This date has been moved on an
annual basis and only now (mid 2006) is it beginning to happen.
However, many purchasers of VoIP ports just want a phone, so the
statistics can be misleading when interpreted by marketeers.
Faxes
One drawback is the difficulty in sending faxes due to software
and networking restraints in most home systems. However, an
effort is underway to define an alternate IP-based solution for
delivering Fax-over-IP, namely the T.38 protocol. Another
possible solution to overcome the drawback is to treat the fax
system as a message switching system which does not need real
time data transmission - such as sending a fax as a email
attachment (see iFax) or remote printout (see Internet Printing
Protocol). The end system can completely buffer the incoming fax
data before displaying or printing the fax image.
Internet Connection
Another drawback of VoIP service is its frequent reliance upon
another separate service - an Internet connection. The quality
and overall reliability of the phone connection is entirely
reliant upon the quality, reliability, and speed of the internet
connection which it is using. Shortcomings with internet
connections and Internet Service Providers (ISPs) can cause a
lot of grief with VoIP calls. Higher overall network latencies
can lead to significantly reduced call quality and cause certain
problems such as echoing.
VoIP isn't entirely reliant upon internet connections, however.
VoIP systems can also utilize regular telephone lines and
business-grade connections like T1's for voice service. A few
business VoIP Providers offer dedicated point-to-point T1
connections, thereby not relying on an internet connection for
service. Although residential VoIP service typically uses only
an internet connection, business-grade VoIP service can use a
variety of connection methods to provide ongoing phone service.
Many VoIP users still maintain a traditional analog voice line
(business line) which allows them to dial emergency numbers and
utilize a traditional fax machine.
Power Outages
Another drawback of VoIP is the inability to make phone calls
during a power outage, but this problem also exists with many
phones used with conventional land lines and can be remedied
with a battery backup. During a power outage you also have the
choice to forward your phone to your cell phone or another phone
number so you would still be able to receive calls. Although you
can't call out on your home phone system during a power outage,
at least you can still receive calls.
If VoIP is used in solitary LAN (with no internet connection),
it would consume more resources compared to a PABX.
Modems are now available with lithium ion battery backup so that
you can use the service with no power.
Implementation challenges
Because UDP does not provide a mechanism to ensure that data
packets are delivered in sequential order, or provide Quality of
Service guarantees, VoIP implementations face problems dealing
with latency and jitter. This is especially true when satellite
circuits are involved, due to long round trip propagation delay
(400 milliseconds to 600 milliseconds for geostationary
satellite). The receiving node must restructure IP packets that
may be out of order, delayed or missing, while ensuring that the
audio stream maintains a proper time consistency. This
functionality is usually accomplished by means of a jitter
buffer.
Another challenge is routing VoIP traffic through firewalls and
address translators. Private Session Border Controllers are used
along with firewalls to enable VoIP calls to and from a
protected enterprise network. Skype uses a proprietary protocol
to route calls through other Skype peers on the network,
allowing it to traverse symmetric NATs and firewalls. Other
methods to traverse firewalls involve using protocols such as
STUN or ICE.
VoIP challenges:
Delay/Network Latency
Packet loss
Jitter
Echo
Security
Fixed delays cannot be controlled but some delays can be
minimized by marking voice packets as being delay-sensitive
(see, for example, Diffserv).
The principal cause of packet loss is congestion, which can be
controlled by congestion management and avoidance. Carrier VoIP
networks avoid congestion by means of traffic engineering.
Variation in delay is called jitter. The effects of jitter can
be mitigated by storing voice packets in a buffer (called a
play-out buffer) upon arrival, before playing them out. This
avoids a condition known as buffer underrun, in which the
playout process runs out of voice data to play because the next
voice packet has not yet arrived, but increases delay by the
length of the buffer.
Common causes of echo include impedance mismatches in analog
circuitry, and acoustic coupling of the transmit and receive
signal at the receiving end.
DSL Internet access
VoIP technology does not necessarily require broadband Internet
access, but this usually supports better quality of service. A
sizable percentage of homes today are connected to the Internet
through DSL, which requires a traditional phone line. Having to
pay for VoIP in addition to both a basic phone line and
broadband Internet access reduces the potential benefits of VoIP.
However, some regional telephone companies now offer DSL service
without the phone (often called "naked DSL" or "dry loop DSL"),
thus saving subscribers money when they switch to VoIP. VoIP can
also be used with Cable Internet instead of DSL, potentially
eliminating the need for a traditional phone line entirely.
Reliability
Conventional telephones are connected directly to telephone
company phone lines, which in the event of a power failure are
kept functioning by back-up generators or batteries located at
the telephone exchange. However, household VoIP hardware uses
broadband modems and other equipment powered by household
electricity, which may be subject to outages dictating the use
of an uninterruptible power supply or generator to ensure
availability during power outages. Early adopters of VoIP may
also be users of other phone equipment, such as PBX and cordless
phone bases, that rely on power not provided by the telephone
company. Even with local power still available, the broadband
carrier itself may experience outages as well. While the PSTN
has been matured over decades and is typically extremely
reliable, most broadband networks are less than 10 years old,
and even the best are still subject to intermittent outages.
Furthermore, consumer network technologies such as cable and DSL
often are not subject to the same restoration service levels as
the PSTN or business technologies such as T-1 connection.
Quality of Service
Some broadband connections may have less than desirable quality.
Where IP packets are lost or delayed at any point in the network
between VoIP users, there will be a momentary drop-out of voice.
This is more noticeable in highly congested networks and/or
where there is long distances and/or interworking between end
points. Technology has improved the reliability and voice
quality over time and will continue to improve VoIP performance
as time goes on.
Emergency calls
The nature of IP makes it difficult to geographically locate
network users. Emergency calls, therefore, cannot easily be
routed to a nearby call center, and are impossible on some VoIP
systems. Moreover, in the event that the caller is unable to
give an address, emergency services may be unable to locate them
in any other way. Following the lead of mobile phone operators,
several VoIP carriers are already implementing a technical
work-around. For instance, one large VoIP carrier requires the
registration of the physical address the VoIP line will be used
at. When you dial the emergency number for your country, they
will route it to the appropriate local system. They also
maintain their own emergency call center that will take
non-routable emergency calls (made, for example, from a software
based service that is not tied to any particular physical
location) and then will manually route your call once learning
your physical location.
The United States government had set a deadline, requiring VoIP
carriers to implement E911; however, the deadline is being
appealed by several of the leading VoIP companies.
This is a different situation with IPBX systems, where these
corporate systems often have full E911 capabilities built into
the system.
Integration into global telephone number system
While the traditional Plain Old Telephone System (POTS) and
mobile phone networks share a common global standard (E.164)
which allocates and identifies any specific telephone line,
there is no widely adopted similar standard for VoIP networks.
Some allocate an E.164 number which can be used for VoIP as well
as incoming/external calls. However, there are often different,
incompatible schemes when calling between VoIP providers which
use provider specific short codes.
Single point of calling
With hardware VoIP solution it is possible to connect the VoIP
router into the existing central phone box in the house and have
VoIP at every phone already connected. Software based VoIP
services require the use of a computer, so they are limited to
single point of calling, though handsets are now available,
allowing them to be used without a PC. Some services provide the
ability to connect WiFi SIP phones so that service can be
extended throughout the premises, and off-site to any location
with an open hotspot. However, note that many hotspots require
browser-based authentication, which most SIP phones do not
support.
Mobile phones
Telcos and consumers have invested billions of dollars in mobile
phone equipment. In developed countries, mobile phones have
achieved nearly complete market penetration, and many people are
giving up landlines and using mobiles exclusively. Given this
situation, it is not entirely clear whether there would be a
significant higher demand for VoIP among consumers until either
a) public or community wireless networks have similar
geographical coverage to cellular networks (thereby enabling
mobile VoIP phones, so called WiFi phones) or b) VoIP is
implemented over legacy 3G networks. However, "dual mode"
handsets, which allow for the seamless handover between a
cellular network and a WiFi network, are expected to help VoIP
become more popular. The first company launching mobile VoIP in
the world was ((truphone)). Phones like the Nokia E60, E61 have
been the first "dual mode" handsets capable of delivering mobile
VoIP with long battery live times.
Security
The majority of consumer VoIP solutions do not support
encryption yet. As a result, it is relatively easy to eavesdrop
on VoIP calls and even change their content. There are several
open source solutions that facilitate sniffing of VoIP
conversations. A modicum of security is afforded due to patented
audio codecs that are not easily available for open source
applications, however such security through obscurity has not
proven effective in the long run in other fields. Some vendors
also use compression to make eavesdropping more difficult.
However, real security requires encryption and cryptographic
authentication which are not widely available at a consumer
level. The existing secure standard SRTP is available on Analog
Telephone Adapters(ATAs) from some manufacturers like Sipura/Linksys,
with a certificate from Voxilla, a VoIP information site. SRTP
is also available for Gizmo Project for softphones (PCs/laptops
emulating a phone).
The Voice VPN solution provides secure voice for enterprise VoIP
networks by applying IPSec encryption to the digitized voice
stream.
Pre-Paid Phone Cards
VoIP has become a major provider of phone services to travellers,
migrant workers and ex-pats, who either, due to not having a
fixed or mobile phone or high overseas roaming charges, choose
instead to use VoIP services to make their phone calls. Pre-Paid
phone cards can be used either from a normal phone or from
Internet Cafes that have phone services. The undeveloped markets
are usually markets where Pre-Paid cards are used; however in
cities with high tourist or immigrant communities they are also
common.
Caller ID
Caller ID support among VoIP providers varies, although the
majority of VoIP providers now offer full Caller ID w/ Name on
Outgoing calls. When calling a traditional PSTN number from some
VoIP providers, Caller ID isn't supported, and therefore the
target person will not know who is calling. The number shows up
as 'Unknown' or '000-012-3456'.
In a few cases, VoIP providers may allow a caller to spoof the
Caller ID information, making it appear as though they are
calling from a different number. Business grade VoIP equipment
and software often makes it easy to modify caller ID
information. Although this can provide many businesses great
flexibility, it is also open to abuse.
Adoption
Mass-market telephony
A major development starting in 2004 has been the introduction
of mass-market VoIP services over broadband Internet access
services, in which subscribers make and receive calls as they
would over the PSTN. Full phone service VoIP phone companies
provide inbound and outbound calling with Direct Inbound
Dialing. Many offer unlimited calling to the U.S., and some to
Canada or selected countries in Europe or Asia as well, for a
flat monthly fee.
These services take a wide variety of forms which can be more or
less similar to traditional POTS. At one extreme, an analog
telephone adapter (ATA) may be connected to the broadband
Internet connection and an existing telephone jack in order to
provide service nearly indistinguishable from POTS on all the
other jacks in the residence. This type of service, which is
fixed to one location, is generally offered by broadband
Internet providers such as cable companies and telephone
companies as a cheaper flat-rate traditional phone service.
Often the phrase "VoIP" is not used in selling these services,
but instead the industry has marketed the phrase "Internet
Phone" or "Digital Phone" which is aimed at typical phone users
who are not necessarily tech-savvy. Typically, the provider
touts the advantage of being able to keep one's existing phone
number. According to a study by Telephia, the top nine providers
in the United States include Vonage, Verizon VoiceWing, AT&T
CallVantage, SunRocket, Lingo, NetZero, BroadVoice, America
Online, Packet8, and Earthlink. Verizon VoiceWing and AT&T
CallVantage are both listed in second place with 5.5% market
share.
At the other extreme are services like Gizmo Project and Skype
which rely on a software client on the computer in order to
place a call over the network, where one user ID can be used on
many different computers or in different locations on a laptop.
In the middle lie services which also provide a telephone
adapter for connecting to the broadband connection similar to
the services offered by broadband providers (and in some cases
also allow direct connections of SIP phones) but which are aimed
at a more tech-savvy user and allow portability from location to
location. One advantage of these two types of services is the
ability to make and receive calls as one would at home, anywhere
in the world, at no extra cost. No additional charges are
incurred, as call diversion via the PSTN would, and the called
party does not have to pay for the call. For example, if a
subscriber with a home phone number in a U.S. area code calls
someone else in his home area code, it will be treated as a
local call regardless of where that person is in the world.
Often the user may also select a phone number with any desired
area code; this is generally done to minimize the phone tariffs
of those who frequently call.
For some users, the broadband phone complements, rather than
replaces, a PSTN line, due to a number of inconveniences
compared to traditional services. VoIP requires a broadband
Internet connection and, if a telephone adapter is used, a power
adapter is usually needed. In the case of a power failure, VoIP
services will generally not function. Additionally, a call to
the U.S. emergency services number 9-1-1 may not automatically
be routed to the nearest local emergency dispatch center, and
would be of no use for subscribers outside the U.S. This is
potentially true for users who select a number with an area code
outside their area. Some VoIP providers offer users the ability
to register their address so that 9-1-1 services work as
expected.
Another challenge for these services is the proper handling of
outgoing calls from fax machines, TiVo/ReplayTV boxes, satellite
television receivers, alarm systems, conventional modems or
FAXmodems, and other similar devices that depend on access to a
voice-grade telephone line for some or all of their
functionality. At present, these types of calls sometimes go
through without any problems, but in other cases they will not
go through at all. And in some cases, this equipment can be made
to work over a VoIP connection if the sending speed can be
changed to a lower bits per second rate. If VoIP and cellular
substitution becomes very popular, some ancillary equipment
makers may be forced to redesign equipment, because it would no
longer be possible to assume a conventional voice-grade
telephone line would be available in almost all homes in North
America and Western-Europe. The TestYourVoIP website offers a
free service to test the quality of or diagnose an Internet
connection by placing simulated VoIP calls from any Java-enabled
Web browser, or from any phone or VoIP device capable of calling
the PSTN network.
Corporate and telco use
Although few office environments and even fewer homes use a pure
VoIP infrastructure, telecommunications providers routinely use
IP telephony, often over a dedicated IP network, to connect
switching stations, converting voice signals to IP packets and
back. The result is a data-abstracted digital network which the
provider can easily upgrade and use for multiple purposes.
Corporate customer telephone support often use IP telephony
exclusively to take advantage of the data abstraction. The
benefit of using this technology is the need for only one class
of circuit connection and better bandwidth use. Companies can
acquire their own gateways to eliminate third-party costs, which
is worthwhile in some situations.
VoIP is widely employed by carriers, especially for
international telephone calls. It is commonly used to route
traffic starting and ending at conventional PSTN telephones.
Many telecommunications companies are looking at the IP
Multimedia Subsystem (IMS) which will merge Internet
technologies with the mobile world, using a pure VoIP
infrastructure. It will enable them to upgrade their existing
systems while embracing Internet technologies such as the Web,
email, instant messaging, presence, and video conferencing. It
will also allow existing VoIP systems to interface with the
conventional PSTN and mobile phones.
Electronic Numbering (Enum) uses standard phone numbers (E.164),
but allows connections entirely over the Internet. If the other
party uses Enum, the only expense is the Internet connection.
Use in Amateur Radio
Amateur radio has adopted VoIP by linking repeaters and users
with Echolink, IRLP, Dstar and EQSO. Echolink and IRLP are
programs/systems based upon the Speak Freely VoIP open source
software. In fact, Echolink allows users to connect to repeaters
via their computer (over the internet) rather than by using a
radio. By using VoIP Amateur Radio operators are able to create
large repeater networks with repeaters all over the world where
operators can access the system with actual ham radios.
Ham Radio operators using radios are able to tune to repeaters
with VoIP capabilities and use DTMF buttons to command the
repeater to connect to various other repeaters, thus allowing
them to talk to people all around the world, however powerful
their radio. Dingotel offers a similar feature for non ham radio
users by providing a P2P network to link FRS radios.
Click to call
Click-to-call is a service which lets users click a button and
immediately speak with a customer service representative. The
call can either be carried over VoIP, or the customer may
request an immediate call back by entering their phone number.
One significant benefit to click-to-call providers is that it
allows companies to monitor when online visitors change from the
website to a phone sales channel. |
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