IP Telephony and VoIP Tutorial-Part 2

IP Telephony and VoIP Tutorial-Part 2
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Posted: 12 Feb 2010 10:06 AM PST

Continuing our series of posts on IP Telephony and VoIP, here is Part 2 of the tutorial:

Can an IP Telephony System be connected to the public telephone network

There are special voice gateways which can connect an IP Telephony system with the public switched telephone network (PSTN) or other telephone networks. Using the voice gateway, a VoIP phone can call a legacy telephone line phone on the public telephone network and vice versa with no problems. Basically the voice gateway translates the IP packets from the IP Telephone system into TDM voice to be transmitted over the legacy PSTN network. Generally, regardless of the infrastructure that the IP Telephony system uses to carry out the conversation, ultimately it is a private telephone network, such as those implemented in corporate call centers, which is transparent to the public telephone network.

What are the benefits of IP Telephony and VoIP

The main advantages of VoIP and IP Telephony in general include:

Single network infrastructure for data and telephony. Since the same infrastructure (communication lines and equipment) serve voice traffic and data traffic, we have significant economies of scale. Also, we achieve better management of telecommunications infrastructure.
Maximum use of telecommunications infrastructure. The packet switched networks (e.g IP Networks) make better use of their bandwidth capacity in comparison with traditional circuit switched telephone networks since the line is not fully occupied for each call conversation therefore it can carry various data packets in addition to voice.
Improved communication for remote workers. The use of IP telephony does not require the user to have a physical presence in the enterprise environment. If the user has an IP connection, he/she can take advantage of the features and functions of the enterprise telephone system, regardless of where the user is located.
New services are introduced. The usage of a single infrastructure for both data and voice allows for the development of a new generation of services such as unified messaging that can contribute significantly to productivity growth.

Why companies are interested for IP Telephony

Since almost all companies have access to the Internet, they have already implemented their corporate networks over the IP protocol. Thus, they are given a first class opportunity to utilize the IP network infrastructure, which includes, in addition to the communication lines, other equipment such as routers, switches, etc. This IP network infrastructure can be used for telephony as well. Even if the IP telephony system is confined within the enterprise, the benefits are significant. When a company uses leased circuits to connect remote branches, the use of these circuits for both IP telephony and data connectivity provides substantial benefits and cost savings to the company.

Is IP Telephony the most economical solution for voice communication

Like any technology infrastructure investment, usage of VoIP and IP Telephony should be treated as a medium to long term business. According to studies, the use of packet switched networks for voice telephony is more economical than the networks that occupy the whole communication line for each conversation. And when we can serve phone calls through our corporate IP network – which in some cases is extended to different parts of the city, other cities or other countries – we certainly save money by not using the public telephone network. When routing phone calls over our own private IP network from New York to Los Angeles and the destination call is a PSTN number in Los Angeles, the call will be charged as local in Los Angeles (it will be routed from our voice gateway in Los Angeles to the PSTN). This is an example of a toll bypass cost saving. Companies should however consider the costs for the implementation of the IP telephony infrastructure, occurring in the increased bandwidth capacity to accommodate also voice traffic, in the extra equipment (e.g IP telephones), the additional software needed, etc. Overall, however, in medium to long term, telephony over IP networks has proved to be much more economical than traditional telephony solutions.