VoIP categories

There are three categories of VoIP:
1. Phone-to-phone
Using normal telephone equipment it allows real time voice transmissions
2. Computer-to-computer:
By using software and computer hardware calls can be made between two computers connected to the internet or private network.
3. Phone-to-computer or computer-to-phone:
Using mixture of the two above.

The Future of VOIP
According to new research by Ovum, 15 per cent of UK businesses have deployed IP telephony, however it is expected that the number will increase up to 40 per cent in next two years. However some observers predict that as VOIP is more universally adopted, monthly fees for telephone service will disappear and a single internet connection could be used for telephone, television, e-mail and surfing the net. Nevertheless many businesses think that quality of service is the most common barrier for enterprises considering the switch to VoIP. [1]

Taiwan's largest telecommunications company blamed VoIP for part of the decrease in long-distance telephone calls revenue in the last years. [2]

Future potential of the three technologies
Since the voice traffic transmitting through data networks is increased dramatically in the last few years because of both supply and demand-side interactions, vendors of voice equipment will continue to develop integrated voice and data devices based on pocketsize technology.

Data and its implications for voice
Unlike most data communications, which can accept delay, voice communications must be performed in near real-time, which means that network delays must be kept short to remain barely visible to the user.

Circuit switching network is more effective and efficient in dealing and transmitting voice than packet switching networks, due to the delay of voice packets across the network, this delay occurs because of the congestion in the network that might result in dropping some packets which will affect the voice integrity. However adding bandwidth to the network is one way to overcome the problem of network delay and congestion.

The interoperability of the three technologies
It is necessary that the interoperability be transparent to the users, who want to communicate through the network and without concern for the technological issues involved.
Fragmentation techniques in Frame Relay, IP and ATM, are relatively similar, however prioritization techniques, signaling protocols and voice compression algorithms are not compatible. Nevertheless development is being made in direction of standardization within each protocol and interworking between them, however still significant work remains to be done. [3]

At present, the Frame Relay Forum has set standards for transmitting voice over Frame Relay; however, there are no standards for voice switching between VFRADs. Furthermore the interoperability standards for voice and multimedia over IP are defined by ITU H.323 which include endpoint negotiation and the format of the information but not issues such as encoding and security. [4]

However achieving interoperability between these varieties of networks will allow users to benefit from the best that each of these technologies has to offer.

References

1. Sylvia Carr 2006, Silicon.com, http://networks.silicon.com/telecoms/0,39024659,39157577,00.htm
2. Dan Nystedt 2006,Networkworld.com, http://www.networkworld.com/news/2006/033006-network-operators-voip.html
   
3. Rad.com, http://www2.rad.com/solution/voe22.htm
4. Voice over IP now, http://www.voipnow.org/2005/09/carrying_voice__1.html