Beginner's guide to Voip

This small guide is an introduction to VoIP from an end-user perspective. I don't pretend to go much deeper into concepts like protocols, communications, devices and network deployment. Instead of this I will focus on VoIP end-user benefits and disadvantages explaining if you could take profit from VoIP technology.
VoIP offers many improvements to your business communications: lower rates, better sound quality with HD voice, communications "on the go", video conferencing and many more ...
We have talked about lower rates but not free, just don't believe that VoIP is free. If somebody tells you so, go ahead and keep your search because nobody is giving a good VoIP service for free and even not Skype should be considered a good VoIP service. Again you should notice that if you want to call landlines even from Skype you will have to pay for it.

Voice over IP (VoIP) is a form of communication that allows everybody to make phone calls over a broadband internet connection instead of typical analog telephone lines (called POTS). Basic VoIP
access usually allows you to call others who are also receiving calls over the internet.
Interconnected VoIP services and gateways also allow you to make and receive calls to and from traditional landline numbers, usually for a service fee. Some VoIP services require a computer or a dedicated VoIP phone, while others allow you to use your landline phone to place VoIP calls through a special adapter, ATA which stands for Analog Telephone Adapter.
VoIP is becoming an attractive communications option for consumers. Given the trend towards lower fees for basic broadband service and the brisk adoption of even faster internet offerings,
VoIP usage should only gain popularity with time. However, this is not always good, as VoIP usage increases, so will the potential threats to the typical user. While VoIP vulnerabilities are typically similar to the ones users face on the internet, new threats, scams, and attacks unique to IP telephony are now emerging.

There are three main protocols used for VoIP call signalling: H.323, SIP and IAX. IAX is only used with Asterisk PBX, although is now an RFC standard it's not yet widely used. H.323 is a bit older and has begun to get appart in benefit of SIP which seems to be the VoIP standard nowadays.
So, if you want to use VoIP service providers or want to buy a brand new ip-phone to start your VoIP network make sure that they are SIP compatible.
For media transmission RTP is the used codec in most implementations but for security reasons it can be replaced with SRTP (which stands for secure RTP).

Security is from an end-user point of view the main concern and the main disadvantage when using VoIP. Many VoIP services are not secured by default. SIP protocol is generally using UDP protocol for data transmission and there's no encription and no integrity. This is the main problem which can be solved just replacing the old deployment and switching to SIP over TCP/TLS which takes benefit of Transport Layer Security, that means message encryption and integrity checking.
VoIP security problems are closely related with traditional network services, thus includes: Denial of Service (DoS) attacks, phishing, Caller-ID spoofing, and many more. That's the main reason why you should consider contacting a professional service in order to secure your VoIP network. There are many tools to get into an office PBX (Private Branch Exchange) and take benefit of the fact that you can make calls you will not pay.