Voice over IP (VoIP)

Solution Preview

An interesting emerging market is using Internet phone and a company's high speed LAN to replace the same company's PBX. Write a one page report on this issue. Cover the following questions in your report:
a. What is a PBX?

See http://en.wikipedia.org/wiki/Pbx for a thorough explanation.

Basically, a PBX is a Private Branch Exchange - a private telephone switch that allows a company or other organization to privately manage telephone numbers within an environment.

Most companies use a PBX for their internal phone system. The PBX provides the interface between internal telephone extensions and the phone company.

b. Consider a call between a user in the company and another user out of the company who is connected to a traditional telephone network. What sort of technology is needed at the interface between the LAN and the traditional telephone network?

See http://en.wikipedia.org/wiki/Voice_over_IP and http://www.cisco.com/en/US/products/sw/voicesw/networking_solutions_products_generic_content0900aecd804f00ce.html for more info.

When a caller using any digital phone system - not just VoIP - places a call, the call is transmitted digitally from their handset to the PBX/VoIP Switch which then translates the digitally encoded audio information into the proper format to be transmitted over the trunk line. A trunk line is a circuit between switching equipment - the interface between the PBX and the phone company.

Trunks are typically T-carrier connections (http://en.wikipedia.org/wiki/T-carrier).

In the case of VoIP, a server with switching software fills the role of the PBX and acts as the interface between the IP telephone and the traditional telephone network.

Owen Linderholm presents a great explanation below - also available here: http://www.voip-news.com/news/features/voip-phone-system-components-062606/

Owen Linderholm

For the average business user, the decision to move to VoIP starts with the decision that the organization needs a new phone system - either that or it is a new organization looking for its first phone system. And for most businesses, that's as complex as they want the decision to be - they want every employee to have a phone with an extension, they want voicemail, they want to transfer calls and so forth. The rest of the details are relatively unimportant.

But that isn't the way that VoIP companies provide phone ...