VoIP Protocol: The Mechanics of Internet Telephony

So much has been said about VoIP (Voice over Internet Protocol) – the way it is a useful and cheaper alternative to regular phones as it uses the internet as the conduit of communication. However few things are discussed about the way the system works per se. Usually, all people know is that with VoIP, one talks over the internet instead of phone lines, and that’s about it.

Also called Internet Telephony, Broadband Telephone, and IP Telephony, VoIP works by channeling vocal conversation over the internet or through any other network that uses IP (Internet Protocol) as its medium. Unlike traditional phone system that transmits lines through dedicated circuit switches, the VoIP protocol travels through a multi-purpose network with packet switches. This means that the road upon which voice conversations travel in VoIP is the same road taken by data, images, text, and other things that travel through the internet, as opposed to traditional system where the line is devoted only for one type of information – vocal.

Any network that uses Internet Protocol can deply VoIP, even networks that are not connected to the internet itself. For example, a Local Area Network for an office building could very well serve as a VoIP medium, being a very useful means of communictions of the employees of the said building. This could be more useful than using the age-old intercom systems as VoIP can be integrated to employee’s computers.

The two most popular types of VoIP, namely SIP (Sesion Initiation Protocol) and H.323. The debate as to which one is better has been ongoing among VoIP enthusiast circles. At the start of the VoIP phonemenon, H.323 reigned as the most popular version of the protocol. However, due to the poor traversal that H.323 performes with NAT and firewalls, its popularity has diminished, particularly in the “local loop”. The domestic users of VoIP shifted to SIP, and the protocol has become widely used. On the other hand, H.323 became the more widely used protocol for backbone voice networks. H.323 has been found to be useful for large carriers. Recently however, H.323 has been enhanced to traverse NAT and firewall devices easily and reliably. Soon H.323 may well gain its popularity again with a renewed flexibility owed to its ne capability to adapt to the said devices.

The concepts of signaling proxy and full media proxy are very important where VoIP travels through many Soft Switches of providers. Three streams of data make up H.323, first – H.225.0 call signaling, second – H.245, third – Media. For instance, a caller who is from Autralia would like to contact the US with a provider that is in Europe, when the call is made using a full proxy mode, the three streams would travel halfway around the globe with a high rate of delay and packet loss (about 500-600ms). Meanwhile, when signalling proxy mode is used, the delay is reduced dramatically to only about 120 to 150 ms. There concepts are seen to be the ones to give way to true global VoIP service providence.

There are other protocols being used aside from SIP and H.323. Each protocol have its own unique feature that caters to different types of users. The choice depends on one’s needs and one’s resources.

Many consider VoIP as a great blessing in the realm of communication. Perhaps it is good to join the bandwagon and reap the great benefits of this revolutionary tool.