VoIP: Voice Over Internet Protocol

History

Voice over Internet Protocol (VoIP) has been a subject of interest almost since the first computer network.

By 1973, voice was being transmitted over the early Internet.The technology for transmitting voice conversations over the Internet has been available to end-user since at least the early 1980s.

In 1996, a shrink-wrapped software product called VocalTec Internet Phone provided VoIP along with extra features such as voice mail and caller ID. However, it did not offer a gateway to the PSTN, so it was only possible to speak to other Vocaltec Internet Phone users.

In 1997, began development of its first softswitch (a term they invented in 1998) softswitches were designed to replace traditional hardware telephone switches by serving as gateways between telephone networks

Introdution



Voice over Internet Protocol (VoIP), is a technology that allows you to make voice calls using a broadband Internet connection instead of a regular (or analog) phone line. Some VoIP services may only allow you to call other people using the same service, but others may allow you to call anyone who has a:

• Telephone number


• Including local


• Long distance


• Mobile


• International numbers

Also, while some VoIP services only work over your computer or a special VoIP phone, other services allow you to use a traditional phone connected to a VoIP adapter.

What Kind if Equipment Do I Need?

• Broadband (high speed Internet)
• Computer
• Adaptor
• Specialized phone is required

Some VoIP services only work over your computer or a special VoIP phone, while other services allow you to use a traditional phone connected to a VoIP adapter.

If you use your computer you will need some:

• software


• inexpensive microphone

Special VoIP phones plug directly into your broadband connection and operate largely like a traditional telephone. If you use a telephone with a VoIP adapter, you'll be able to dial just as you always have, and the service provider may also provide a dial tone.

What Are Some Advantages of VoIP?

Some VoIP services offer features and services that are not available with a traditional phone, or are available but only for an additional fee. You may also be able to avoid paying for:

• Broadband connection


• Traditional telephone line

What Are Some disadvantages of VoIP?

If you're considering replacing your traditional telephone service with VoIP, there are some possible differences:

• Some VoIP services don't work during power outages


• May not offer backup power


• Not all VoIP services connect directly to emergency services


• VoIP providers may or may not offer directory assistance/white page listings.

Reliability

Conventional phones are connected directly to telephone company phone lines, which in the event of a power failure are kept functioning by backup generators or batteries located at the telephone exchange. However, IP Phones and the IP infrastructure they connect to typically depend on the availability of mains electricity or another locally generated power source.

Voice travels over the internet in almost the same manner as data does in packets. So when you talk over an IP network your conversation is broken up into small packets. The voice and data packets travel over the same network with a fixed bandwidth. This system is more prone to congestion and DoS attacks than traditional circuit switched systems.

To increase the reliability of VoIP phones the VoIP provider needs to increase dedicated and redundant connectivity via T-1 access and backup DSL, with automatic failover at each location.The company can create a reliable network by reducing the number of single points of failure.

VoIP phone accessibility and portability

If using a software based soft-phone, calls can only be placed from the computer on which the soft-phone software resides. Thus with a soft-phone the caller is typically limited to a single point of calling.

When using a hardware based VoIP phone-device/phone-adapter it is possible to connect traditional analog phones directly to a VoIP phone-adapter without the need to operate a computer.

The converted analog phone signal can then be connected to multiple house phones or extensions, just as any traditional phone company signal can be connected. A second VoIP hardware configuration option involves the use of a specially designed VoIP telephone which incorporates a VoIP phone adapter directly into the phone itself, and which also does not require the use of a computer.

A third VoIP hardware configuration option involves the use of a WiFi router and a WiFi SIP phone which can extend a service range throughout a home or office. WiFi SIP phones can also be used at any location where an "unauthenticated" open hotspot Wi-Fisignal is available.However, note that many hotspots require browser-based authentication, which most SIP phones do not support.

Outgoing Call Control Flow Diagram

After adding VoIP functionality, the outgoing call control flow of a phone application will be as shown below: