Network theory

COEN: 4331

NETWORK THEORY

Student Name

Asma Hamad Alharbi

ID: 200700045

Instructor Name

Dr.Nazeeruddin Mohammad     

Table of Contents

3.1 IP PBX 4

3.2 Clients 4

3.3 ATA(Analog telephone Adapter) 5

3.4 Services 5

4. How Voice over IP Works 6

5. Company example 7

6. advantages of VoIP 8

7. disadvantages of VoIP 8

8. Conclusion 8

Motivation:

When you call someone, you will follow the routine steps of calling; you pick up the phone handset, dial up the number, and wait the receiver to pick up it, have conversation and finally close the telephone hand set. However, Have you ever thought of having another method cheapest, and can substitute the ordinary phone which you pay a fixed fee every month? Actually, the substituted method become true by using Voice over IP or (VOIP) technology that allow you to use your laptop, or special equipment as method to communicate freely with anyone in any place and that safe a lot of money for large company. It is a nice technology that allows the communication to be sent using Internet protocol.

In the past and until now, ordinary telephone uses Public Switching Telephone Network (PSTN) where the entire connection or path is dedicated between sender and receiver during the duration of conversation; however, the motivation to find alternative way to make phone call without restrict the resources or path was possible by integrating data, audio and video via data network. Voice in the data network is handled as data that can be sampled and sent in packets formats. These packets are identified by IP address using User Datagram Protocol (UDP) taking any path through Internet till it reach to destination. This technology that can identify destination by IP address called Voice over IP. Voice over IP (VOIP) is a term that describes a technology that can carry voice, video and instant messages, voice email or any media through Internet Protocol.

In voice over IP where the voice travel in a form of packets on Ethernet network, there must be components required to enable the use of technology VoIP:

1. 
   PBX system (real time server): PBX is stand to Private Branch Exchange. This server is responsible for connecting PSTN and VoIP telephony system that are used in the company internally. If the company have one telephone line used from outside, it can link all the employees offices who use VoIP phones with three to four digits to dial up among each other and using the external telephone line if they want to call from outside. The opposite is true, when someone need to call employee in company it required to have the extension number. PBX has roles such as creating connection between users, maintain, and end the connections.
   

PBX comes into two configuration either hosted PBX and premise PBX:

• 
  Hosted PBX: when the company doesn’t want to maintain server on the building so it pays to service provider money in monthly basis which provide the PBX server as service. In that module, the company need to keep in the building switch that connect users and the switch connect to the router which has the responsibility to route all calls through internet to the hosted PBX.
  

• 
  Premise PBX:
  

2. 
   VoIP Clients :
   

• 
  Hard phone or voice over IP phone:
  

• 
  Softphone:
  

• 
  Ordinary phone:
  

3. 
   Analog Telephone Adapter or( gate way) :
   

• 
  It provide analog interface for the telephone to communicate via Voice over IP.
  
• 
  It is responsible for converting analog signals from ordinary telephone to digital form that used in data network and vice versa.
  

Both types of ATA perform the same functions but they differ in the connection:

• 
  It uses USB port into personal computer and it requires software to be installed in the PC to enable VoIP services.
  
• 
  It connects directly into high speed Ethernet DSL and no need to install any software.
  

4. 
   Services :
   

In general, voice over IP work in three Cases:

Let’s imagine person X want to communicate with person Y. what must X follow to communicate with Y if we consider Y always uses VoIP technology.

First Case: ordinary telephone to communicate with number using (VoIP):

• 
  A person X has an ordinary telephone and he wants to uses Voice over IP Communication. First he needs to have a small device called Analog Telephone Adapter (ATA).this device must be attached to the ordinary telephone to do the required changing from analog to digital signals that enables the voice to be carried in the internet using IP .In another network, the digitalized packets go to the PBX Server that is attached to switch that will forward the call to the right VOIP device by examining the extension number.
  

Second Case: two telephone using VOIP technology:

A person X wants to call person Y which is located in another branch of the company. X needs to call the number of Y which directed to IPPBX server and routed the voice digitalized packet to another router then IPPBX server gives the number to the switch that forward the call to the proper destination

Company real example:


Gate way

In order to understand the most powerful and wonderful advantage of Using VOIP technology this example gives an idea how it reduces the cost for calling.

Let’s consider the blue centered building is the main company building that has different branches on the same country. These branches communicate with each other using VOIP technology and communicate with the main company building using VOIP. The company main building and its branches communicate via interment and IPPBX serves provided in each building. Naturally, every company has customers that want to communicate with company and vice versa.

Case 1: Let consider the company wants to communicate with one of its clients who uses normal telephone. So the plan is to have one telephone line in each branch and when the call comes from the main company building it will go via internet using VOIP technology to the nearest branch that will use the local telephone number to call the customer.

Case 2: let’s consider the customer wants to call the company which uses VOIP technology. First, he will call the number of the company. The requested number will be send to PSTN that will do the required converting from analog to digital signal to be in a form that is acceptable to VOIP technology than a digitalized voice packets will be carried in the interment until it reaches the destination IPPBX server .

Advantage of using Voice over IP:

1. 
   Low Cost:
   

2. Features:

In regular phone one must pay money for any additional services he order but in voice over IP many free features available like call waiting.

Also, it allows video communication at reasonable price in normal cases we need to have cheap web camera and microphone.

1. 
   No service during a power outage:
   

2. 
   Voice over IP does not support emergency calls or numbers because it uses IP that makes it difficult to trace the location of communication but that is not the case with ordinary telephone.
   

Voice over IP is a powerful technology that can reduce the cost but it cannot replace the normal phone completely because of the drawbacks that has such as the need to have stable constant power supply. So, in case of no electricity and an emergency situation occurs, no VOIP telephone will help in this situation, the only telephone work is the ordinary telephone. So, voice over IP can work in parallel with telephone.

http://www.3cx.com/PBX/voice-over-ip.html

http://voip.about.com/od/servicesandsolutions/a/VoIPProviders.htm

http://faq.programmerworld.net/voip/voip-advantages-disadvantages.htm