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(Voice Over IP) A telephone service that uses the Internet as a global telephone network. Many companies, including Vonage, 8x8 and AT&T (CallVantage), typically offer calling within the country for a fixed fee and a low per-minute charge for international. Broadband Internet access is required, and regular house phones plug into an analog telephone adapter (ATA) provided by the company or purchased from a third party.
Advantages Cost:
In general, phone service via VoIP is free or costs less than equivalent service from traditional sources but similar to alternative Public Switched Telephone Network (PSTN) service 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. |
Functionality: VoIP can facilitate tasks that may be more difficult to achieve using traditional phone 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 Internet connection.
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.  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: Faxes:
One drawback is the inability to send 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.
Internet Connection:
Another drawback of VOIP service is its 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 (ISP's) can cause a lot of grief with VOIP calls.
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.
Implementation challenges:
Because IP 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. 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.
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VoIP
