In telecommunications, VoIP (Voice over Internet Protocol) is the new buzzword as many companies and individuals try to take advantage of the cost savings it offers. Another new term connected with VoIP is SIP (Session Initiation Protocol) due to the appearance of many SIP phones. The main difference between SIP and VoIP is their scope. VoIP is actually not a discrete technology but a family of technologies that are primarily concerned with setting up voice calls across packet networks like the Internet. SIP is just one of the technologies that are under the VoIP umbrella.
There are many technologies used in VoIP. There are technologies that are used to convert and compress the audio signal; there are technologies that are used to format the digital data and transmit it to the destination, and there are technologies that are used by devices to communicate with each other. SIP is in the latest of the three. It is a protocol that standardizes signals to initiate, terminate, accept, reject, hold, or redirect VoIP calls. It is basically a language used by the phones in order to communicate what it wants to do with each other. SIP is not concerned with how the voices are carried across the network once the call has been initiated as other protocols are used for that.
What confuses most users is the difference between VoIP handsets and SIP handsets. Keep in mind that a SIP handset is also a VoIP handset. The products that are commonly called VoIP phones require to be connected to a computer, and the computer has to be turned on in order to conduct calls. It is not very desirable to have a computer running just so you can make and receive calls. SIP phones are able to do the signaling without the need for a computer. It can, therefore, be plugged into an Ethernet outlet and connected to the Internet. In this scenario, only your modem needs to be constantly powered to give the SIP phone access to the Internet. In this manner, SIP phones behave more like traditional phones.
