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DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

MAHARISHI ARVIND

INSTITUTE OF ENGINEERING AND TECHNOLOGY

ACKNOWLEDGMENT

A scholarly and quality work like studying any seminar topic can be accomplished by

motivation guidance and inspiration of certain quarters besides the individual efforts. Let

us in this page express our heartiest gratitude to all those who helped us in various stages

In this seminar report.

During our seminar period all the staff member of Deptt. Have helped us with their

skills. Also we are thankful to other technical staff of the Deptt. who have helped us to

complete our report successfully. We Wish to express our deep sense of gratitude to our

seminar guide “Mr. Lokesh Sharma” for his valuable guidance and kind cooperation

without which this report would have not been possible.

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Maharishi Arvind Institute of Engineering & Technology (Approved by AICTE and Affiliated to Rajasthan TechnicalUniversity,Kota) Sector7, Madhyam Marg, Mansarovar, Jaipur-302020, Rajasthan, India Department of Electronics & Communication Engineering.

Certificate

This is to certify that the Seminar report entitled “SOFTPHONES” being submitted by NIMISHA BHATNAGAR is a bonafide record of project work carried out by him under my supervision and guidance, and hence approved for submission to the Department of Electronics & Communication Engineering in partial fulfilment of the requirements for the award of the degree of Bachelor of Technology in Electronics & Communication Engineering of the Rajasthan Technical University Kota, Rajasthan during the academic year 2011-2012.

Mr. Lokesh Sharma Mr. K.K. Bhargava Lect. & Project Guide Associate Professor& Head of the Dept.

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INDEX

SOFTPHONES

COMMUNICATION PROTOCOLS

CIRCUIT SWITCHING vs. PACKET SWITCHING

SOFTSWITCH

IP TELEPHONY

IP ADDRESSES AND NAMES

ROUTERS AND ROUTING

SESSION INITIATION PROTOCOL (SIP)

ADVANTAGES OF SOFTPHONES

DISADVANTAGES OF SOFTPHONES

VoIP BASED SOFTPHONES

CONCLUSION

REFERENCES

SOFTPHONES4

Introduction:

A softphone is a software program for making telephone calls over the Internet using a

general purpose computer, rather than using dedicated hardware. Often a softphone is

designed to behave like a traditional telephone, sometimes appearing as an image of a phone,

with a display panel and buttons with which the user can interact. A softphone is usually used

with a headset connected to the sound card of the PC, or with a USB phone.

A VoIP softphone enables you to make calls with just your computer using a VoIP service.

How soft phone works is very similar to a regular telephone. The only difference is that it is

found in our computer.

How It Works:

We can download soft phones or it may be part of the VOIP package. Regardless, a soft

phone may look like a regular telephone in your PC. If we want to use it, we may need to

open a window, press the shortcut key in your keyboard, or open a program where it’s

currently embedded.

If we need to talk to someone, make sure that we are wearing our headset and the microphone

is on. Soft phones can be used for any type of calls, from PC to PC as well as from phone line

to PC and vice versa.

Requirements:

To make voice calls over the Internet, a user typically requires the following:

A modern PC with a microphone and speaker, or with a headset, or with USB phone.

Reliable high-speed Internet connectivity like Digital subscriber line (DSL) or cable

service.

Account with an Internet telephony service provider or IP PBX provider.

Who Can Benefit From VoIP Softphones?

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Softphones can be used by anybody with a computer. There are a few types of users who can

really benefit from the features of a VoIP softphone:

VoIP beginners

Heavy travelers

Telecommuters

Call centre employees

Small businesses

Frequent long-distance callers

VoIP beginners can quickly and cheaply explore how the service works by downloading a

VoIP softphone to make free computer-to-computer or computer-to-phone calls. Heavy

travellers can avoid racking up large bills on their mobile phones or at hotels by using a low-

cost VoIP service with a VoIP softphone. Telecommuters can register a VoIP softphone with

their office PBX system to enjoy the same call features available to them at the office while

they are on the move. Call centre employees and small businesses can save on costs by

pairing a VoIP service with a softphone to avoid purchasing and maintaining desk phones.

International and long-distance rates are much lower when using a VoIP softphone, so those

making regular or frequent calls out-of-state or country can cut some major costs.

VoIP Softphone Features:

VoIP softphones offer the same features that traditional phones offer and more:

Call forwarding.

Call conferencing.

Hold capabilities.

Call transferring.

Voicemail.

Greeting capabilities.

Text, IM, and video capabilities.

Echo cancellation to improve sound quality.

Contact list/address book.

Communication Protocols:

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Voice over Internet Protocol(VoIP) :

Voice over IP (VoIP) commonly refers to the communication protocols, technologies,

methodologies, and transmission techniques involved in the delivery of voice

communications and multimedia sessions over Internet Protocol (IP) networks, such as

the Internet. Other terms commonly associated with VoIP are IP telephony, Internet

telephony.

Internet telephony refers to communications services —voice, fax, SMS, and/or voice-

messaging applications— that are transported via the Internet, rather than the public switched

telephone network (PSTN). The steps involved in originating a VoIP telephone call are

signalling and media channel setup, digitization of the analog voice signal, encoding,

packetization, and transmission as Internet Protocol (IP) packets over a packet-switched

network. On the receiving side, similar steps (usually in the reverse order) such as reception

of the IP packets, decoding of the packets and digital-to-analog conversion reproduce the

original voice stream.

VoIP is available on many smartphones and Internet devices so that users of portable devices

that are not phones, may place calls or send SMS text messages over 3G or Wi-Fi.

VoIP allows both voice and data communications to be run over a single network, which can

significantly reduce infrastructure costs. VoIP devices have simple, intuitive user interfaces,

so users can often make simple system configuration changes. Dual-mode phones enable

users to continue their conversations as they move between an outside cellular service and an

internal Wi-Fi network, so that it is no longer necessary to carry both a desktop phone and a

cell phone.

Session Initiation Protocol (SIP):

The Session Initiation Protocol (SIP) is an IETF-defined signalling protocol widely used for

controlling communication sessions such as voice and video calls over Internet Protocol (IP).

The protocol can be used for creating, modifying and terminating two-party (unicast) or

multiparty (multicast) sessions. Sessions may consist of one or several media streams.

Other SIP applications include video conferencing, streaming multimedia distribution, instant

messaging, presence information, file transfer and online games.

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How VoIP Works?

If you've never heard of VoIP, get ready to change the way you think about long-distance

phone calls. VoIP, or Voice over Internet Protocol, is a method for taking analog audio

signals, like the kind you hear when you talk on the phone, and turning them into digital

data that can be transmitted over the Internet.

How is this useful? VoIP can turn a standard Internet connection into a way to place free

phone calls. The practical upshot of this is that by using some of the free VoIP software that

is available to make Internet phone calls, you're bypassing the phone company (and its

charges) entirely.

VoIP is a revolutionary technology that has the potential to completely rework the world's

phone systems. VoIP providers like Vonage have already been around for a while and are

growing steadily. Major carriers like AT&T are already setting up VoIP calling plans in

several markets around the United States, and the FCC is looking seriously at the potential

ramifications of VoIP service.

Above all else, VoIP is basically a clever "reinvention of the wheel." In this article, we'll

explore the principles behind VoIP, its applications and the potential of this emerging

technology, which will more than likely one day replace the traditional phone

system entirely.

The interesting thing about VoIP is that there is not just one way to place a call. There are

three different "flavors" of VoIP service in common use today:

ATA -- The simplest and most common way is through the use of a device called

an ATA (analog telephone adaptor). The ATA allows you to connect a standard

phone to your computer or your Internet connection for use with VoIP. The ATA is

an analog-to-digital converter. It takes the analog signal from your traditional

phone and converts it into digital data for transmission over the Internet. Providers

like Vonage and AT&T Call Vantage are bundling ATAs free with their service.

You simply crack the ATA out of the box, plug the cable from your phone that

would normally go in the wall socket into the ATA, and you're ready to make VoIP

calls. Some ATAs may ship with additional software that is loaded onto the host

computer to configure it; but in any case, it's a very straightforward setup.

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IP Phones -- These specialized phones look just like normal phones with a

handset, cradle and buttons. But instead of having the standard RJ-11 phone

connectors, IP phones have an RJ-45Ethernet connector. IP phones connect directly

to your router and have all the hardware and software necessary right onboard to

handle the IP call. Wi-Fi phones allow subscribing callers to make VoIP calls from

any Wi-Fi hot spot.

Computer-to-computer -- This is certainly the easiest way to use VoIP. You don't

even have to pay for long-distance calls. There are several companies offering free

or very low-cost software that you can use for this type of VoIP. All you need is

the software, a microphone, speakers, a sound card and an Internet connection,

preferably a fast one like you would get through a cable or DSL modem. Except for

your normal monthly ISP fee, there is usually no charge for computer-to-computer

calls, no matter the distance.

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Circuit Switching Vs Packet Switching:

Existing phone systems are driven by a very reliable but somewhat inefficient method for

connecting calls called circuit switching.

Circuit switching is a very basic concept that has been used by telephone networks for more

than 100 years. When a call is made between two parties, the connection is maintained for the

duration of the call. Because you're connecting two points in both directions, the connection

is called a circuit. This is the foundation of the Public Switched Telephone Network (PSTN).

The important thing to look for in transmitting information over such a complex network is

the path or circuit. The devices making up the path are called nodes. For instance, switches,

routers and some other network devices are nodes.

In circuit-switching, this path is decided upon before the data transmission starts. The system

decides on which route to follow, based on a resource-optimizing algorithm, and transmission

goes according to the path. For the whole length of the communication session between the

two communicating bodies, the route is dedicated and exclusive, and released only when the

session terminates.

In Circuit Switching networks, when establishing a call a set of resources is allocated for this

call. These resources are dedicated for this call, and can be used by any of the other calls.

Circuit Switching is ideal when data must be transmitted quickly, must arrive in sequencing

order and at a constant arrival rate. There for when transmitting real time data, such as audio

and video, Circuit Switching networks will be used.

Packets:

To be able to understand packet-switching, you need to know what a packet is. The Internet

Protocol (IP), just like many other protocols, breaks data into chunks and wraps the chunks

into structures called packets. Each packet contains, along with the data load, information

about the IP address of the source and the destination nodes, sequence numbers and some

other control information. A packet can also be called a segment or datagram.

Once they reach their destination, the packets are reassembled to make up the original data

again. It is therefore obvious that, to transmit data in packets, it has to be digital data.

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In packet-switching, the packets are sent towards the destination irrespective of each other.

Each packet has to find its own route to the destination. There is no predetermined path; the

decision as to which node to hop to in the next step is taken only when a node is reached.

Each packet finds its way using the information it carries, such as the source and destination

IP addresses.

Packet switching main difference from Circuit Switching is that that the communication lines

are not dedicated to passing messages from the source to the destination. In Packet Switching,

different messages can use the same network resources within the same time period. Since

network resources are not dedicated to a certain session the protocol avoid from waste of

resources when no data is transmitted in the session. Packet Switching is more efficient and

robust for data that is burst in its nature, and can withstand delays in transmission, such as e-

mail messages, and Web pages.

Consider the two following examples to answer your question:

Example of Circuit Switching:-

 You pick up your land phone and dial your friend. At that point, the TELCO provider creates

a dedicated Circuit for that session and connects you to your friend's telephone. No matter

how long you keep the line open with your friend, the circuit will remain, and packets

flowing between both telephones will always follow the same path. This is an example of a

circuit-switched network.

Example of packet-switching:-

 In the second example, you switch on your PC and connect to your favorite site that offers a

number of applications you can download from, so you begin downloading one application at

a time. Each packet has to find its own route to the destination, i.e., your computer. Each

packet finds its way using the information it carries, such as the source and destination IP

Address. If network congestion occurs, the routers responsible for routing packet between

networks will automatically select different paths to ensure data is transferred as required.

This is an example of a packet-switched network.

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Soft switch

A softswitch is a central device in a telecommunications network which connects telephone

calls from one phone line to another, typically via the internet, entirely by means of software

running on a general-purpose computer system. Most landline calls are routed by purpose-

built hardware, formerly using physical switchboards, but softswitches are the dominant 21st

century trend.

A softswitch is typically used to control connections at the junction point between circuit-

switched and packet-switched networks. A single device containing both the switching logic

and the switching fabric can be used for this purpose.

Softswitch is the functional component that provides call-related features. Capabilities such

as call forwarding, call waiting, last call return and three way videoconferencing, if

implemented in the network

VoIP Softswitches are subdivided into two classes. Class 4 softswitches and Class 5

softswitches.

Softswitches used for transit VoIP traffic between carriers are usually called class 4

softswitches. Analogous with other Class 4 telephone switches, the main function of the class

4 softswitch is the routing of large volumes of long distance VoIP calls. The most important

characteristics of class 4 softswitch are protocol support and conversion, transcoding, calls

per second rate, average time of one call routing, number of concurrent calls.

Class 5 softswitches are intended for work with end-users. These softswitches are both for

local and long distance telephony services. Class 5 softswitches are characterized by

additional services for end-users.

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IP Telephony:

IP telephony (IPT) offers a viable alternative to the legacy voice exchange, delivering

improved application integration, scalability, and multi-site management. It is precisely these

features that make this rapidly-maturing technology so attractive to organizations seeking to

reduce costs, increase productivity and improve customer relations. However, voice is critical

to business, and a major change to emerging technologies like IPT requires an understanding

of a broad range of technologies, careful planning and thoughtful implementation. This guide

has been compiled to help decision makers to understand the relevant technologies as they

define their strategies.

Fig: 1.1 Network Layout of A small businesses VoIP

Following the introduction, we will review the typical components and features of an

enterprise telephony system. We then introduce voice over IP (VoIP), the underlying network

infrastructure, and then we address the various issues one must take into account when

designing the network to carry voice. We conclude by comparing these VoIP solutions to the

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traditional centralized PBX, but before we do so, we describe advanced applications such as

collaboration, presence, customer relationship management and unified messaging.

There are many reasons to implement an IP-based voice communication system reduced

long-distance telephony charges; lower capital costs; lower management and administrative

costs; reduced complexity; improved integration of distributed business entities; and a greater

ease with which voice applications may be combined with other business systems.

IP ADDRESSES AND NAMES

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2.1. IP (Internet Protocol):

The Internet Protocol (IP) is the principal communications protocol used for relaying

datagrams (also known as network packets) across an internetwork using the Internet

Protocol Suite. Responsible for routing packets across network boundaries, it is the primary

protocol that establishes the Internet.

IP is the primary protocol in the Internet Layer of the Internet Protocol Suite and has the task

of delivering datagrams from the source host to the destination host solely based on

the addresses. For this purpose, IP defines datagram structures that encapsulate the data to be

delivered. It also defines addressing methods that are used to label the datagram source and

destination.

Internet Protocol Suite is sometimes referred to as TCP/IP.

Function:

The Internet Protocol is responsible for addressing hosts and routing datagrams (packets)

from a source host to the destination host across one or more IP networks. For this purpose

the Internet Protocol defines an addressing system that has two functions: identifying hosts

and providing a logical location service. This is accomplished by defining standard datagrams

and a standard addressing system.

Datagram Constuction:

Each datagram has two components, a header and a payload. The IP header is tagged with the

source IP address, destination IP address, and other meta-data needed to route and deliver the

datagram. The payload is the data to be transported. This process of nesting data payloads in

a packet with a header is called encapsulation.

The protocol was needed that could provide an open interface between applications and the

various physical networks underneath (e.g.,, Ethernet on the LAN, Frame Relay, DSL and

ISDN in the WAN, etc..). There have been various proposed protocols including:

1. IP Internetworking Protocol – IETF standard

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2. OSI Open Systems Interconnect – ITU standard

3. IPX Internet Packet exchange – Novell.

IP Addresses:

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IP addresses are used to identify devices connected to the network. The 32-bit addresses are

written as four decimal values (with each group capable of representing less than 256 values)

separate by a dot. The first groups of numbers identify the network upon which the machine

is located, and the other groups of numbers identify the specific machine within that subnet

work. Here is an example: 169.254.70.213

Fig: 2.1 IP Windows

When installing a computer, the network manager defines the machine’s address and the

address of the default gateway – the machine on the local network that provides connectivity

to other networks. In the early days of the Internet, this machine would be a computer with

two network interfaces and it would perform the task of forwarding packets between the two

interfaces. Today however, it is more likely to be a router. For use on machines connected

directly to the Internet, IP addresses are carefully allocated in blocks and managed by the

owner of the addresses to ensure that no two machines have the same address. However,

within an enterprise the IETF has allocated certain address ranges for internal machines only.

The addresses of the internal machines are protected by a firewall that provides Network

Address Translation (NAT) that not only protects the identity of internal machines, but also

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ensures that addresses belonging to one enterprise do not conflict with similar addresses used

by another enterprise.

Like telephone numbers, the numbers to the right of the address identify the specific machine

or device. When planning an IP voice implementation, a legacy voice manager should learn

the details of the addressing scheme used within the organization before connecting new IP

devices to the network. To make it easier for people to find services on their network and on

the Internet, a name-to-number translation service was introduced called the Domain Name

System (DNS). This global system allows one to type in a name like http://www.louvre.fr/

rather than its IP address http://160.92.103.98. The DNS service simplifies things by allowing

the end user to memorize a website name instead of having to remember its IP address, which

could change if the Louvre were to change to a different service provider.

When you consider how you use phone numbers in your cell phone, you will recognize that

here too, you use people’s names rather than their numbers. Later we will show how this

facility is being introduced by the current generation of IP voice systems.

Allocating and Managing Addresses:

Given that each device has to have its own IP address, does this mean that you must manually

assign an IP address to every phone you install on your network? Fortunately, the answer to

this question is “no.”An automatic address allocation system was developed to ease the

administrative overhead associated with IP address allocation: Dynamic Host Configuration

Protocol (DHCP).The DHCP protocol resides on a server and manages a pool of IP

addresses. DHCP keeps track of which addresses are currently in use and which are available

for allocation.

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ROUTERS AND ROUTING

In the telephony world, conversations are carried out over circuits – end to end connections

between the caller and collie. All the work of determining how to route the call is done during

call setup. Once the circuit is in place, no further route decisions are required (assuming there

are no catastrophic problems on the network).Data networks, however, do not work like this.

Packets are forwarded and forgotten so that each intermediary router between the source and

the destination:

1. Reads the destination address of the packet

2. Checks which route to use

3. Forwards the packet to the interface associated with that route

4. And forgets it.

The primary function of a router is to route packets along the best path across a network.

Each router maintains a route table, essentially a roadmap of the network which is kept up to

date by exchanging information with other routers about the status of each link and the status

of the network.

Fig: 4.1 Routing technology

When an incoming packet is received, a router identifies the destination address, checks the

route tables to determine the best route, and then forwards the packet to the next router along

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the path. A router should be connected to multiple forwarding paths so that if one path fails,

packets will be re-routed around the failed connection.

Due to their strategic location in the network (at the LAN/WAN boundary), routers are

frequently used to prioritize and filter traffic. Note that WAN links are shared resources and

therefore suffer from similar contention problems inherent with the early Ethernet. This can

cause serious problems for real-time voice communications.

QoS will be discussed in the following section:

Routers are also used to act as a firewall, filtering packets to protect the network from

unwanted attempts to gain access to the network. Firewalls use techniques similar to traffic

prioritization; that is, they identify and filter traffic based on source or destination address,

protocol type, or IP port numbers. Port and socket numbers, in particular, may indicate

application functions such as telnet or file transfer protocol (FTP), and because these

applications can be used to break into a corporate network, identifying these types of traffic

before the traffic enters the network can offer valuable protection. There are literally

hundreds of well-known techniques for breaking into a network, such as IP spoofing, Denial

of Service attacks, or SYN floods. In all cases, the router or firewall must be capable of

identifying and filtering these types of traffic. Use of traffic prioritization or firewall

technology could become an issue when transporting voice over the network due to the

additional processing required for these functions. However, the newest generation of routers

and stand-alone firewall devices has become much more powerful, making use of custom

ASICs to simultaneously classify, queue, filter, and forward packets with minimal latency.

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SESSION INITIATION PROTOCOL (SIP)

The Session Initiation Protocol (SIP) is an IETF-defined signalling protocol widely used for

controlling communication sessions such as voice and video calls over Internet Protocol (IP).

The protocol can be used for creating, modifying and terminating two-party (unicast) or

multiparty (multicast) sessions. Sessions may consist of one or several media streams.

Other SIP applications include video conferencing, streaming multimedia distribution, instant

messaging, presence information, file transfer and online games.

1. SIP User Agent Clients (UACs)

2. SIP Location Server – track which IP address a client is currently using

3. SIP Proxy Servers – forwards requests to other servers on behalf of SIP clients.

4. Redirect Servers – communicates the target address of the called party to the calling party.

User Agent:

A SIP user agent (UA) is a logical network end-point used to create or receive SIP messages

and thereby manage a SIP session. A SIP UA can perform the role of a User Agent

Client (UAC), which sends SIP requests, and the User Agent Server (UAS), which receives

the requests and returns a SIP response. A SIP phone is a SIP user agent that provides the

traditional call functions of a telephone, such as dial, answer, reject, hold/unhold, and call

transfer. SIP phones may be implemented as a hardware device or as a softphone.

Proxy server:

An intermediary entity that acts as both a server (UAS) and a client (UAC) for the purpose of

making requests on behalf of other clients. A proxy server primarily plays the role of routing,

which means its job is to ensure that a request is sent to another entity "closer" to the targeted

user. Proxies are also useful for enforcing policy (for example, making sure a user is allowed

to make a call). A proxy interprets, and, if necessary, rewrites specific parts of a request

message before forwarding it.

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Registrar:

A server that accepts REGISTER requests and places the information it receives in those

requests into the location service for the domain it handles which registers one or more IP

addresses to a certain SIP URI, indicated by the sip: scheme, although other protocol schemes

are possible. More than one user agent can register at the same URI, with the result that all

registered user agents will receive a call to the SIP URI.

SIP registrars are logical elements, and are commonly co-located with SIP proxies. But it is

also possible and often good for network scalability to place this location service with a

redirect server.

Redirect server:

A user agent server that generates 3xx (Redirection) responses to requests it receives,

directing the client to contact an alternate set of URIs. The redirect server allows proxy

servers to direct SIP session invitations to external domains.

 

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Advantages of VoIP:

VoIP phone service providers offer many advantages to the residential and small office/home

office user. If you have a high speed internet connection then choosing a VoIP phone service

might be right for you.

Low Cost:

This technology leads to greater financial savings. This happens because there exists only one

network carrying the voice and data provided by only one supplier. If you have a broadband

Internet connection (DSL or cable), you can make PC-to-PC phone calls anywhere in the

world for free. If you wish to make a PC-to-phone connection, there's usually a charge for

this but probably much cheaper than your regular phone service.

You can pay as you go or you can sign up with a VOIP service provider and pay a monthly

fee in return for unlimited calls within a certain geographic area. For example, some VOIP

services in the United States allow you to call anywhere in North America at no extra charge.

Low Taxes:

Since the calls are being carried over the Internet, governments have not heavily taxed VoIP

phone services. Compare that to your local telephone bill (go ahead and take a close look)

and you will see you are spending quite a bit on taxes each month. Therefore, choosing a

VoIP provider could add up to significant savings for you and your family.

Portability:One important concept to understand about VoIP is that unlike it’s forefathers (let’s call them

PSTN for now), it is not distance or location dependent. As far as VoIP is concerned, you

could be calling your supplier 1,000 miles away in Indonesia or calling your business partner

on the other end of town, and it doesn’t make any difference at all, in terms of connectivity.

You can make and receive phone calls wherever there is a broadband connection simply by

signing in to your VoIP account. This makes VoIP as convenient as e-mail – if you are

travelling, simply pack a headset or Internet phone and you can talk to your family or

business associates for almost nothing.

No extra cables, no extra cost:A VoIP phone number, unlike your regular phone number, is completely portable. Most

commonly referred to as a virtual number, you can take it with you anywhere you go.Even if 25

you change your office address to another state, you phone number can go with you. Heck,

you can even take your whole business with you wherever you travel.

Features:Unlike regular phone service which usually charges more for extra features, VOIP comes

with a host of advanced communication features. For example, call forwarding, call waiting,

voicemail, caller ID and three-way calling are some of the many services included with VOIP

telephone service at no extra charge. You can also send data such as pictures and documents

at the same time you are talking on the phone.

VoIP phones can integrate with other services available over the Internet, including video

conversation, message or data file exchange in parallel with the conversation, audio

conferencing, managing address books and passing information about whether others (e.g.

friends or colleagues) are available online to interested parties.

Flexibility:

When you choose a VoIP phone service provider, you will be sent a converter to allow a

regular phone to use the VoIP phone service. Your phone number is programmed into the

converter. This means that you can take your phone converter and phone number and use

them wherever you travel in the world, just as long as you have access to a high-speed

Internet connection. Because your telephone number is based in your converter (and not your

home/office), you have the option of choosing any area code for your phone number. Some

carriers will allow you to have more than 1 phone number in different area codes for a small

additional fee (called a virtual phone number).

Video-conferencing:

VoIP enables advanced bandwidth capabilities and improved video-conferencing and at a

reasonable price.

Disadvantages of VoIP:

If VOIP is starting to sound really good to you, make sure you understand the following

downsides as well.

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No service during a power outage:

During a blackout a regular phone is kept in service by the current supplied through the

phone line. This is not possible with IP phones, so when the power goes out, there is no VOIP

phone service. In order to use VoIP during a power outage, an uninterruptible power supply

or a generator must be installed on the premises. It should be noted that many early adopters

of VoIP are also users of other phone equipment such as PBX and cordless phone bases that

also rely on power not provided by the telephone company.

Emergency calls:

Another major concern with VOIP involves emergency 911 calls. Traditional phone

equipment can trace your location. Emergency calls are diverted to the nearest call center

where the operator can see your location in case you can't talk. However, because a voice-

over-IP call is essentially a transfer of data between two IP addresses, not physical addresses,

with VOIP there is currently no way to determine where your VOIP phone call is originating

from.

Although many companies are making an effort to provide for emergency calls in their

service, this issue remains an important deterrent against VoIP.

Reliability:

Because VOIP relies on an Internet connection, your VOIP service will be affected by the

quality and reliability of your broadband Internet service and sometimes by the limitations of

your PC. Poor Internet connections and congestion can result in garbled or distorted voice

quality. If you are using your computer at the same time as making a computer VOIP call,

you may find that voice quality deteriorates dramatically.

This is more noticeable in highly congested networks and/or where there are long distances

and/or internetworking between end points.

VoIP Voice Quality:

VoIP has a bit to improve on Voice Quality, but not in all cases. VoIP QoS (Quality of

service) depends on so many factors: your broadband connection, your hardware, the service

provided by your provider, the destination of your call etc. More and more people are

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enjoying high quality of phone calls using VoIP, but still many users complain of hearing

Martian, having to wait a lot before hearing an answer etc.

Security:

This one is the last in this list, but it is not the least! Security is a main concern with VoIP, as

it is with other Internet technologies. The most prominent security issues over VoIP are

identity and service theft, viruses and malware, denial of service, spamming, call tampering

and phishing attacks.

Other:

The domestic customers have to use headphone to make and receive phone calls, which

usually international. But this could be changed when analogue telephones will be brought up

to serve the same purpose.

VoIP Based Softphones

VoIP Cheap:

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It is software which we can install in our computers or laptops. Through this we can talk to

anyone in the world at very cheap or rather for free. VOIP soft phones are used by millions of

users worldwide to make voice and video calls. It looks like a traditional telephone. Through

this we can make calls to any landline or mobile network.

People now no more have to think about international call rates. You can talk to your

relatives or for business point of view without thinking about the rates. Just you have to

download software called voipcheap install it and then you can easily talk to anyone like we

do it through our mobiles or landline. The only difference between this and traditional phone

is that it works through the internet.

VoIP Cheap Dialpad:

As we can see in the picture, its keypad looks the same as the traditional phones. We can dial

the number by using the mouse click. It has got many features like we can send sms even

through these softwares. If we are using the same number then we can just add the contact of

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that person in the list so that later on we don’t have to dial the number just by clicking on the

contact name the number will be dialled.

This is the way how we can send messages through this software.

CONCLUSION

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VoIP systems today cannot only match the features of legacy PBXs, but they have been built

with today’s communications environment in mind. When most of the legacy PBX

architectures were launched, the Internet was irrelevant to mainstream business activity.

Today, however, the Internet is a crucial tool in facilitating business, and IP forms the

foundation for many of the applications and systems that continue to drive our productivity to

new levels. IP telephony is inherently designed to leverage the Internet phenomenon,

providing a distributed communications infrastructure that businesses will use to both scale

and simplify their activities simultaneously.

REFERENCES

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1. Lawrence Harte “Introduction to IP Telephony Technology”; june2001; PP: 153-177.

2. Bill Stuckey “VoIP Made Easy “; august 2004; PP: 189-230.

3. Daniel Collins “Carrier Grade voice over IP”; 2003; PP: 184-215.

4. Ted Wallingford “Switching to VoIP”; 2005; PP: 44-59.

5. How stuff works site.

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