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Voice over Internet Protocol (VoIP)
What is VoIP?
VoIP (pronounced just as it is spelt) is short for “voice over Internet Protocol”. Also known as Internet Telephony, VoIP is the general term used to describe transmitting two-way voice over the Internet in real (or near-real) time. The concept of Internet Telephony is found to be confusing by a lot of people, but in reality, and the way most people end up using it, it is not very different from standard telephones. One thing to keep in mind is that most people do not understand the technology used to carry the voice signals with standard or mobile telephones, they just know that it works. The same goes for VoIP. Being a new technology however, it is important to understand what benefits it can bring to an organisation and in a very basic way at least, how it will interact with existing office systems.
Very briefly, the POTS (Plain Old Telephone System) carries voice using analogue signalling over dedicated electronic circuits (at least to the telephone exchange – nowadays the telephone carriers digitise the signals between exchanges, and some even use VoIP). VoIP is a method by which the voice signal is digitised and then transmitted over the Internet in packets, in a similar manner to how an email with a sound file attachment is send over the Internet. It is not the fact that the Internet is used to transmit voice that is of great interest (since many telcos have been doing this for years on their long-haul routes), but the fact that VoIP is brought right to the edge of the network, to the end users’ equipment which makes it interesting…
Although voice over IP, or “voice chat” as it was more commonly known about 10 years ago, has been around for a while as a method for PC users to communicate with each other over the Internet, it is only in the last few years that bandwidth, customer equipment, and protocols have provided us with a viable substitute for the PSTN (public switched telephone network). A very important part of voice over IP, and the thing that makes it useful to most people, is the interconnection with the PSTN – the ability for VoIP users to call people on standard telephones, and vice versa. This essential service is the lifeblood of the hundreds of VoIP providers who terminate calls for end users on to the PSTN at relatively inexpensive rates by purchasing minutes from the big telcos in bulk. The key idea here is that the voice data is carried over the Internet to a point much closer to the end destination of the phone call, and hence the leg on the PSTN is likely to be a lot cheaper. Consider the common example where a VoIP user in Adelaide calls a non-VoIP user in Sydney – by carrying the call over the Internet to Sydney, before jumping onto the PSTN, the total call cost is equal to the cost of Internet traffic from Adelaide to Sydney (generally considered to be minimal) plus the cost of an un-timed local call in Sydney!
VoIP vs. PSTN
VoIP offers end users a lot of features and cost savings compared to the traditional PSTN . The following table is a brief comparison of the two technologies:
Carrier Lines
PSTN Dedicated lines required from the telco.
VoIP All voice channels can be transmitted over the one Internet connection
Bandwidth
PSTN Each analogue telephone line uses 64kbps in each direction.
VoIP Using compression, VoIP can use as little as ~10kbps in each direction. Further bandwidth can be saved by using silence suppression (not transmitting when the person is not speaking).
Features such as
call waiting, Caller ID, conferencing, music on hold, etc.
PSTN Often available at an extra cost.
VoIP Generally available for free.
Remote PABX extensions for teleworkers and branch-offices.
PSTN Very costly and require dedicated lines for each remote extension.
VoIP Remote extensions are a standard feature.
Expansability and upgradeability
PSTN Complex: can require significant hardware additions, provisioning of new lines, etc.
VoIP Often just requires more Internet bandwidth and software upgrades.
Choice of companies to terminate calls
PSTN Each line is provisioned by a single telco, meaning there is very limited least cost routing.
VoIP Hundreds of VoIP providers to choose from to terminate calls.
Typical business line rental
PSTN $40
VoIP $11
Typical local call cost
PSTN 17c
VoIP 14c
Typical mobile call cost
PSTN 35c/min + flagfall
VoIP 32c/min (no flagfall)
Free Calls
PSTN None
VoIP To other VoIP users of the same gateway (eg., between offices)
Features of a VoIP Enabled Office
VoIP enabling an office can take one of two forms:
1. Add VoIP to an existing PABX. This is useful if your office already has a PABX which fulfils all of your telephony needs, but you want to take advantage of the lower costs associated with using VoIP for outgoing calls. Any number of outgoing lines can be VoIP enabled. This is also particularly useful if you have a number of offices with frequent calls between offices. By VoIP enabling the PABXs in each office, calls between offices can be trunked over the Internet.
2. Installing a software-based PABX (IP PABX) that connects both to local telephone lines, and to the Internet for VoIP terminated calls. Additionally, VoIP is used between the PABX and the extensions allowing for extensions to be located at any geographic location with an Internet connection. The PABX is software configurable and runs on a standard PC server. Additionally, users can utilise traditional telephones, IP phones, or even soft-phones with a headset. An IP PABX has all the features of the most advanced PABXs including interactive voice responses, music on hold, conferencing facilities, voicemail, call hold, call transfer, multiple lines and least cost routing. The initial installation cost of an IP PABX is often less than a traditional PABX with similar features, and the ongoing costs in telephone calls, line rental and maintenance is significantly lower.
(Contributed by Mr Kevin Mayer, OzVoIP.com, the specialist VoIP consultant who spoke at our recent VoIP seminar.)
If you would like further information on VoIP, please call Tripos IT and we will obtain the answers you seek.
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