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Chapter 1: INTRODUCTION

1.1 INTRODUCTION

Congratulations on purchasing the VBell™ Video SIP VoIP Intercom. This Intercom is a Smart Home intercom, which

includes a high definition camera, as well as a two-way communication sound system, using Voice over IP (VoIP)

video-audio transfer technology. This device can be accessed through your smart phone or tablet from any location

around the world, and provides a simple way to protect and secure your home.

What is VoIP? (Voice over Internet Protocol) which, simply stated, means using the Internet to make and receive

telephone calls. How exactly does it work? What are the advantages? All the computers connected to the Internet

understand how to send and receive data packets; thankfully, they all agree to work in exactly the same way using

exactly the same system, which is known as the Internet Protocol or IP. (One of the key parts of the IP that you may

be familiar with is that every computer can be "addressed" by quoting a unique number, known as its IP address,

which is a bit like the computer equivalent of a telephone number or building address. Currently most computers

have IP addresses made from four pairs of two digits separated by points, such as 12.34.56.78.

There are three different kinds of VoIP but we will explain only one applicable for VBell™ Intercom - is entirely

computer based; Skype™ is the best-known example. When you use Skype to call someone, it sets up a more or

less direct connection (known as a peer-to-peer or P2P) connection with someone else's computer, across the

Internet. You send and receive text messages, voice data, or webcam chat over this direct link. Apart from the

initial logging on process, there is no intermediate computer managing the communication between the sender

and receiver, which makes Skype relatively secure compared to other forms of telephone communication.

That's exactly how VBell™ operates.

The biggest plus point of VoIP is call cost, which is typically either free or much less than making traditional calls

over the PSTN. (That's a huge plus point for customers, but a huge drawback for the big telephone companies,

who've been forced to regear their businesses to meet the threat from Internet telephony.) VoIP is easy and often

immediate to set up, and generally requires no long-term contract (although you do need to set up an account of

some kind to create a phone number or user name where people can call you). You can usually send any kind of

data over VoIP, from text and images of your computer desktop to voice and webcam chat. Another big plus is that

VoIP liberates you from a fixed, physical location; With VBell™ App you can talk and receive calls and see your

visitors from your Intercom basically anywhere in the world via secure P2P connection.

What is SIP? The Session Initiation Protocol (SIP) is a communications protocol for signalling, for the purpose of

controlling multimedia communication sessions. The most common applications of SIP are in Internet telephony for

voice and video calls, private IP telephone systems, as well as instant messaging over Internet Protocol (IP)

networks.

The protocol defines the messages that are sent between endpoints, which govern establishment, termination and

other essential elements of a call. SIP can be used for creating, modifying and terminating sessions consisting of

one or several media streams. SIP is designed to be independent (although not agnostic) of the underlying

transport layer, and can be used with UDP, TCP, and SCTP; it can also be secured using TLS over the latter two. It is

a text-based protocol, incorporating many elements of the Hypertext Transfer Protocol (HTTP) and the Simple Mail

Transfer Protocol (SMTP).

By itself, SIP only provides signalling; it is used in conjunction with other protocols that specify the media format

and protocol to be used to subsequently communicate the media. Although SIP can carry arbitrary data, SIP is

typically used to carry a Session Description Protocol (SDP) message specifying the codec and the use of either the

Real-time Transport Protocol (RTP) or Secure Real-time Transport Protocol (SRTP) for media communication.