VoIP is a great technology which is being used widely around the world. But there are some major disadvantages to this technology and must be considered before investing.

The Disadvantages

• The biggest issue with the VoIP technology is the quality of sound. We can guarantee the sound quality will be good on the local network but there is no one that guarantees the sound quality over the internet as there are several other things at the same time.
• VoIP packets (data, voice or fax) are separated into smaller chunks and then transmitted over an IP network which is the base of the problem. Due to interference there can be packet drops causing the gap in the voice or some part may not be buffered quickly to let the parties in conversation hear things accurately. Once a packet is dropped, it's been re-requested causing others in sequence to brake for a second or two and wait until the lost packet is found to reform the original packets by the VoIP hardware, to be heard by the parties. This is where quality of sound is tested.
• Latency is a major issue with the VoIP system and you will still find some problems in the best available today due either the internet connection speed is goofy, or the systems doesn't have enough processing power etc. lack of bandwidth can cause VoIP systems to go crazy sometimes and the quality is affected always as normally a VoIP call would need 20k per connection and we expect the data to reach the destination before the parties could be notified of a delay in VoIP communication.
• One problem is compatibility. When it comes to PC to PC VOIP calls, there is no one universal standard. Some VOIP systems are proprietary in nature, and will only allow calls to others who are using the same software.
• Data transmitted over an IP network is usually compressed and this kind compression and de-compression take away a good amount of processing power and degrade the quality of sound being received by either party. You would also get to hear echoes which required additional modules which again eat up another portion of processing power.
• A VoIP phone does not need any processing power but is very expensive as compared to an ordinary phone. Well, yes if you want to cut down regular monthly telephone bills than this one time investment is to its value.
• If your VoIP systems is a computer based product, then you would need to protect that PC from outside world as virus, worms, Trojans are all waiting for it. Get either a PIX firewall or another firewall which would need investment in case you don't have it already. If the VoIP computer goes down, ever VoIP phone will go down.
• Since both the VoIP phone and VoIP server/computer are powered, If you lose power or internet connection, the VoIP technology will not work

Since we are running Voice over IP, the caller identification number is not going to appear as it's an IP address which is calling unless you pay for such a (caller ID) service.