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VOICE OVER INTERNET PROTOCOL -VOIP

A SEMINAR REPORT

SUBMITTED TOWARDS PARTIAL FULFILLMENT FOR THE AWARD

OF DEGREE

Bachelor of Technology

In

Computer Science and Engineering

Submitted By

RAHUL SINGH

COMPUTER SCIENCE AND ENGINEERING DEPARTMENT

Vidya College of Engineering (Meerut)

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INDEXS.NO. CONTENTS PAGENUMBER

1.Abstract3

2. Introduction 4

3.History of VoIP 5

4.How VoIP works?6

5.Requirements of a VoIP 9

6. H.323 Protocol 13

7.SIP Protocol 18

8.Q.923 Protocol19

9.H.245 Protocol 20

10. Advantages of VoIP20

11. Advanced Applications 22

12. Opportunities 22

13. Weaknesses (limitations) 23

14. Security issue 25

15. VoIP Equipment and Solution Vendors 28

16. Conclusion 31

17. REFERENCES 32

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1) Abstract

Ever tried placing a voice call over the Internet? If you have, we are sure you

havent had a pleasant experience. You might have even promised yourself

never to try it again.

But, Stop right there!!

Now get ready tochange your mind. In the near future, if you make a telephone

call, it is more than likely that it would be over the Internet or some other packet

network. But, what is it that would make this possible? It is a bunch of protocols

and standards; and years of research done by organizations all over the world

that would bring about this revolution. They call it VOICE OVER IP,

INTERNET TELEPHONY& a host of other names. VoIP (voice over IP -

that is, voice delivered using the Internet Protocol) is a term us ed in IP

telephony for a set of facilities for managing the delivery of voice information

using the Internet Protocol (IP). In general, this means sending voice

information in digital form in discrete packets rather than in the traditional

circuit-committed protocols of the public switched telephone network (PSTN).A major advantage of VoIP and Internet telephony is that it avoids the tolls

charged by ordinary telephone service. VoIP is therefore telephony using a

packet based network instead of the PSTN (c ircuit switched).

With the passes of time VoIP replace the PSTN and people will acquaint with

the new technology which will reduce their cost and they will no more inclined

to the PSTN to make a call anywhere. Somehow it will take time to replace the

communication system invented by Bell.

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2) Introduction

Voice over IP (VoIP) is a blanket description for any service that delivers

standard voice telephone services over Internet Protocol (IP). Computers to

transfer data and files between computers normally use Internet protocol.

"Voiceover IPis the technologyofdigitizingsound, compressingit, breakingit

up into datapackets, andsending it over an IP (internetprotocol) network

where it is reassembled, decompressed, and converted back into an analog

waveform. The transmission of sound over a packet switched network in this

manner is an order of magnitude more efficient than the transmission of sound

over a circuit switched network.

VoIP saves bandwidth also by sending only the conversation data and not

sending the silence periods. This is a considera ble saving because generally

only one person talks at a time while the other is listening. By removing the

VoIP packets containing silence from the overall VoIP traffic we can reach up

to 50% saving. In a circuit switched network, one call consumes the en tire

circuit. That circuit can only carry one call at a time.

In a packet switched network, digital data is chopped up into packets, sent

across the network, and reassembled at the destination. This type of circuit can

accommodate many transmissions at the same time because each packet only

takes up what bandwidth that is necessary.. Internet Telephony simply takes

advantage of the efficiencies of packet switched networks.

Gateways are the key component required to facilitate IP Telephony. A gateway

is used to bridge the traditional circuit switched PSTN with the packet switched

Internet. The gateway allows the calls to transfer from one network to the other

by converting the incoming signal into the type of signal required by the

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network it is required to send it on. For example, A PC user wishes to call

someone using a conventional phone. The PC sends the IP packets containing

digitized voice to the gateway.

Applications involving voice over internet protocol technology:

Internet Voice Telephony.

Intranet & Enterprise network voice telephony.

Internet fax service.

Multimedia internet collaboration.

Internet call centres.

PBX intercommunications.

3)History of VoIP

During the early 90's the Internet was beginning its commercial spread. TheInternet Protocol (IP), part of the TCP/IP suite (developed by the U.S.

Department of Defence to link dissimilar computers across many kinds of data

networks) seemed to have the necessary qualities to become the successor of the

PSTN.

The first VoIP as a technology demonstration, was introduced in 1995 - an

"Internet Phone". An Israeli company by the name of "Vocal Tec" was the one

developing this application. The application was designed to run on a basic PC.

The idea was to compress the voice signal and translate it into IP packets for

transmission over the Internet.

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VocalTec's Internet phone was a significant breakth rough, although the

application's many problems prevented it from becoming a popular product.

Since this step IP telephony has developed rapidly. The most significant

development is gateways that act as an interface between IP and PSTN

networks.

This "first generation" VoIP application suffered from delays (due to

congestion), disconnection, low quality (both due to lost and out of order

packets) and incompatibility.

4) How VoIP works?

i. Part one :- Technology overview

Let us look at very simple VoIP call. Consider two VoIP telephones connected

via an IP network .In this example both VoIP telephones are connected to a

local LAN. Sallys phone has an IP address of 192.168.1.1, Bills phone is

192.168.1.2, and the IP addresses uniquely identify the telephones. Both our

phones are configured to use a widely used VoIP standard called H.323.

Bill wants to talk to Sally and his phone knows the IP address of Sallys phone.

Bill lifts the handset and 'dials' Sally, the phone sends a call setup request packet

to Sally's phone, Sallys phone starts to ring, and responds to Bill's phone with a

call proceeding message. When Sally lifts the handset the phone sends a

connect message to Bill's phone. The two phones will now exchange the data

packets containing the speech. At the end of the call Bill replaces his handset

and phone stops sending voice data sends a disconnect message and Sally's

phone responds with a release message.

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IP PBX A traditional Private Branch Exchange (PBX) connects all the phones

within an organization to the public telephone network. Essentially IP PBX

replaces all the internal phones with VoIP telephones. The IP PBX has standard

telephone trunk connections to the public telephone network. The IP PBX i s a

PBX with VoIP, but it also has the ability to support VoIP over the Internet and

Office to Office VoIP.

ii. Part 2: The Protocols.

I have made an assumption that both ends of a VoIP telephone conversation are

compatible. This compatibility only happens if both ends agree to use the same

protocol. All manufacturers who claim to be producing industry standard voice

over IP either support SIP or H.323 protocol.

iii. Part 3 : Encoding

The call control part of H.323 sets up the parameters for the full duplex voice path between source telephone and destination telephone. I will continue with

my analogies to explain how your voice gets transpor ted across the Internet. In

terms of H.323 there is a trade-off between call quality and bandwidth, in

general the higher the quality the greater the bandwidth required. During the

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call setup portion of H.323 the phones have to decide which speech

encoder/decoder to use when they send the speech to the other phone, Bill and

Sally both have phones that support G.723.1, G.711 and G729. The main

difference between each of these encoders is the amount of bandwidth they use,

G.711 uses 64kbit/s and G.723.1 can use as little as 5.3kbit/s. Although it would

seem obvious to use the encoder with the lowest bandwidth, there is a loss of

quality with a lower bandwidth.. At the same time a stream of G723.1 encoded

voice data starts being sent from each phone to the other phone.

G.723.1 defines how an audio signal with a bandwidth of 3.4KHz should be

encoded for transmission at data rates of 5.3Kbps and 6.4Kbps. G.723.1

requires a very low transmission rate and delivers near carrier class quality. The

VoIP Forum as the baseline Codec for low bit rate IP Telephony has chosen this

encoding technique.

G.711.The ITU standardised PCM (Pulse Code Modulation) as G.711. This

allows carrier class quality audio signals to be encoded for transmission at data

rates of 56Kbps or 64Kbps. G.711 uses A-Law or Mu-Law for amplitude

compression and is the baseline requirement for most ITU multimedia

communications standards.

iv. Part 4 :Hear the Quality

The performance or quality of the speech depends up on encoders at each end,

the number of packets lost on route, Latency and Jitter. As a general rule the

occasional lost packet will not affect too drastically the quality of a call, but lose

in 5 a row the entire word is lost and this will be a problem. So if you are going

to have lost packets make sure they are only lost in a regular distributed manner.

5% lost packets distributed evenly will not result in the loss of words lose .

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Quality also varies with manufacturer. If a manufacturer has a G.723.1 encoder

it may not sound the same as another manufacturer who claims to have G.723.1,

quality does vary.

5) Requirements of a VoIP

The requirements for implementing an IP Telephony solution to support Voice

over IP vary from organization to organization, and depend on the vendor and

product chosen. The following section aims to identify the fundamental

requirements:-

Software Requirements

Hardware Requirements

Protocol Requirements

i.

Software Requirements

The software package chosen will reflect the organizational needs, but should

contain the following modules - Voice Over IP Publication, and other sources.

Voice Processing Module:- This aspect of the software is required to prepare

voice samples for transmission. The functionality provided by the voice

processing module should support:

A PCM Interface is required to receive samples from the telephony interface

(e.g. a voice card) and forward them to the Voice Over IP software for further

processing.

Echo Cancellation is required to reduce or eliminate the echo introduced as a

result of the round trip exceeding 50 milliseconds.

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Idle Noise Detection is required to suppress packet transmission on the network

when there are no voice signals to be sent. This helps to reduce network traffic

as up to 60% of voice calls are silence and there is no point in sending silence.

A Tone Detector is required to discriminate between voice and fax signals by

detecting DTMF (Dial Tone Multi frequency) signals.

The Packet Voice Protocol is required to encapsulate compressed voice and

fax data for transmission over the network.

A Voice Playback Module is required at the destination to buffer the incoming

packets before they are sent to the Codec for decompression.

Call Signalling Module. This is required to serve as a signalling gateway

which allows calls to be established over a packet switched network as opposed

to a circuit switched network (PSTN for example).

Packet Processing Module. This module is required to process the voice and

signaling packets ready for transmission on the IP based network.

Network Management Protocol.Allows for fault, accounting and

configuration management to be performed.

ii. Hardware Requirements

The exact hardware, which would be required, again, depends on organizationalneeds and budget. The list below highlights the most general hardware required.

The most obvious requirement is the existence (orinstallation)ofan IP based

network within the branch office gateway is required to bridge the differences

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between the protocols used on an IP based network and the protocols used on

the PSTN.

The gateway takes a standard telephone signal and digitizes it before

compressing it using a Codec. The compressed data is put into IP packets and

these packets are routed over the network to the intended destination.

The PC's attached to the IP based network require the voice/fax software

outlined above. They also require Full DuplexVoice Cards which allow both

communicating parties to speak at the same time - as often happens in reality.

As an alternative to installing Voice Cards, IP Telephones can be attached to the

network to facilitate Voice Over IP. A secondary gateway should be considered

as a backup in the event of the failure of the primary gateway.

iii. Protocol Requirements There are many protocols in existence but

the main ones are considered to be the f ollowing:

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H.323 is an ITU (International Telecommunications Union) approved standard

which defines how audio /visual conferencing data is transmitted across a

network. H.323 relies on the RTP (Real-Time Transport Protocol) and RTCP

(Real Time Control Protocol) on top of UDP (User Datagram Protocol) to

deliver audio streams across packet based networks.

a) Real-Time Transport Protocol (RTP)

It defines a standardized packet format for delivering audio and video over IP

networks. It is the standard protocol for streaming applications developed

within the IETF (Internet Engineering Task Force).

RTP is used extensively in communication and entertainment systems that

involve streaming media, such as telephony, video teleconference applications

and web-basedpush-to-talkfeatures.

RTP is used in conjunction with the RTP Control Protocol (RTCP). While RTP

carries the media streams (e.g., audio and video), RTCP is used to monitor

transmission statistics andquality of service (QoS) and aids synchronization of

multiple streams. When both protocols are used in conjunction, RTP is

originated and received on even port numbersand the associated RTCP

communication uses the next higher odd port number.It is one of the technical foundations of Voice over IP and in this context is

often used in conjunction with a signalling protocol which assists in setting up

connections across the network. RTP was developed by the Audio -Video

Transport Working Group of the Internet Engineering Task Force (IETF) and

first published in 1996 as RFC 1889, superseded by RFC 3550 in 2003.

b) Resource Reservation Protocol (RSVP) is the protocol which supports

the reservation of resources across an IP network. RSVP can be used to indicate

the nature of the packet streams that a node is prepared to receive.

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Fig :- OSI reference model layer in VOIP

6)What is H.323 ?

It is designed to act above transport layer and is mainly used for transmission of

voice, data and video conferencing over packet networks .Over the next few

years, the industry will address the bandwidth limitations by upgrading the

Internet backbone to asynchronous transfer mode (ATM), the switching fabric

designed to handle voice, data, and video traffic. Such network optimization

will go a long way toward eliminating network congestion and the associated

packet loss. The Internet industry also is tackling the problems of network

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reliability and sound quality on the Internet through the gradual adoption of

standards.

H.323 can be applied in a variety of mechanisms

Audio only (IP telephony),

Audio and Video (Video telephony),

Audio, Video, Data.

H.323 can also be applied to multipoint -multimedia communications. H.323

provides myriad services and therefore can be applie d in a wide variety of areas:

Consumer, Business and Entertainment.

H.323 Components :-

The H.323 standard specifies 4 kinds of components, which when networked

together, provide the pointto-point and point-to-point-to-multipoint multimedia

communication services:

Terminals

Gateways,

Gatekeepers,

Multipoint Control Units (MCUs).

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i. Terminals:

Used for real-time bidirectional multimedia communications, an H.323 terminalcan either be a personal computer (PC) or a stand -alone device, running an

H.323 & the multimedia applications. It supports audio communication and can

optionally support video or data communications. As the basic service provided

by an H.323 terminal is audio communications, an H.323 terminal plays a key

role in IP-telephony services.

H.323 terminals are the client endpoints on the LAN that provide real-time,

two-way communication. They can be realized either as SW -Clients running on

a PC or workstation or as a dedicated HW-devices. All terminals must support

voice communication; video and are optional.

Function of the Terminal:

The terminal is the user or the end point.

Provides real-time 2 way communication.

Optional: Video & data streaming.

Mandatory voice streaming.

Protocols Supported by the Terminal

H.232

H.245 (Control channel usage & capabilities)

sQ.931 (Call setup &signalling )

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RAS (for use with Gatekeepers/Registration/ Admission/Status)

RTC/RTCP (sequence Audio & status video packets)

ii. Gateways :

A gateway connects two dissimilar networks. An H.323 gateway provides

connectivity between an H.323 network and a non -H.323 network. For example,

a gateway can connect and provide communication between an H.323 terminal

and SCN networks (SC N networks includes all switched telephony networks,

e.g. public switched telephone network [PSTN]).

This connectivity of dissimilar networks is achieved by translating protocols for

call setup and release, converting media between different networks, and

transferring information between the networks connected by the gateway. A

gateway is not required, however, for communication between two terminals on

an H.323 network.

The Gateway also translates between audio and video codecs and performs call

setup and clearing on both the LAN side and the PSTN side.

The Functions of the gateway can be stated as follows :

Task-translation.

Audio Codec

Video codec

H.245 H.221 (ISDN Conference)

H.245 H.242 (Audio-Visual terminals)

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iii. Gatekeepers :-

A gatekeeper can be considered the brain of the H.323 network. It is the most

important component of an H.323 enabled network.

It is the focal point for all calls within the H.323 network.

Although they are not required, gatekeepers provide important serv ices such as

addressing, authorization and authentication of terminals and gateways;

bandwidth management; accounting; billing; and charging. Gatekeepers may

also provide call-routing service.

The Functions of the Gatekeeper can be stated as follows:

Task: user information / name server

Gatekeeper is optional but essential.

Managing communications.

Address translation.

Call Control.

Routing services.

System management.

Security policies.

iv. Multipoint Control Unit:-

MCUs provide support for conferences of three or more H.323 terminals. All

terminals participating in the conference establish a connection with the MCU.

The MCU manages conference resources, negotiates between terminals for the

purpose of determining the audio or video coder/decoder (CODEC) to use, and

may handle the media stream.

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The gatekeepers, gateways and MCUs are logically separate components of the

H.323 standard but can be implemented as a single physical device.

The functions of the MCU can be stated as follows:

Task: maintain all audio, video data & control streams

mandatory for conferences .

7) What is SIP ?

The Session Initiation Protocol (SIP) is asignallingprotocol for initiating,managing and terminating voice and video sessions across packet networks. SIP

sessions involve one or more participants and can use unicast or multicast

communication. Borrowing from ubiquitous Internet protocols, such as HTTP

and SMTP, SIP is text-encoded and highly extensible

A SIP network is composed of four types of logical SIP entities. Each entity has

specific functions and participates in SIP communication as a client (initiates

requests), as a server (responds to requests), or as both.

i. User Agent (UA):-

In SIP, a User Agent (UA) is the endpoint entity. User Agents initiate and

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terminate sessions by exchanging requests and responses.

User Agent as an application, which contains both a User Agent client and User

Agent server, as follows:6 RADVISION SIP Overview

User Agent Client (UAC)a client application that initiates SIP requests.

User Agent Server (UAS)a server application that contacts the user when a

SIP request is received and that returns a response on behalf of the user.

ii. Proxy Server

A Proxy Server is an intermediary entity that acts as both a server and a

clientfor the purpose of making requests on behalf of other clients.

iii. Redirect Server

A Redirect Server is a server that accepts a SIP request, maps the SIP address of

the called party into zero (if there is no known address) or more new addresses

and returns them to the client.

iv. Registrar

A Registrar is a server that accepts REGISTER requests for the purpose of

updating a location database with the contact information of the user specified

in the request.

8) What is Q.923 ?

Network Layer is specified by the ITUQ-series documentsQ.923 through

Q.939. Q.931, the layer 3 protocol, is used for the ISDN call establishment,

maintenance, and termination of logical network connections between two

devices.During the layer 3 call setup, three parties are involved, and are w here

messages sent and received

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a) the Caller,

b) the ISDN Switch, and

c) the Receiver.

9) What is H.245 ?

It is a control channelprotocol used with [in]

e.g. H.323 and H.324 communication sessions, and involves the line

transmission of non-telephone signals. It also defines

separate sendand receive capabilities and the means to send these details to

other devices that support H.323.One major drawback within the initial version

of H.323 was the lengthy, four-way H.245 protocol handshake required during

the opening up the logical channels of a telephony session. Later versions of

H.323 introduced the Fast Connectprocedure, using the fast Start element of an

H.225.0 message. Fast Connect brought the negotiation down to a two -way

handshake .

10) Advantages ofVoIP

There are many advantages to be gained from implementing an IP Telephony

solution within the organization. The following list aims to highlight some of

the advantages of such a strategy:

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Single network infrastructure. When installing VoIP in the office only a

single cable is required to the desk, for both telephone and data. Eliminating

separate telephone wiring.

VoIP uses "soft" switching which eliminates most of the legacy PBX

equipment. Reducing the cost of installing a communications infra -structure and

the maintenance cost once installed.

Simple upgrade path. The VoIP PBX technology is software based. It is easier

to expand, upgrade and maintain t han its traditional telephony counterparts.

Bandwidth efficiency. VoIP can compress more voice calls into available

bandwidth than legacy telephony.. IP Telephony helps to eliminate wasted

bandwidth by not transporting the 60% of normal speech which is sil ence

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IP - the underlying protocol- is supported by most platforms and is

independent of the transport protocol used.

Only one physical network is required to deal with both voice/fax and

data traffic instead of two physical networks. Having only one physical network

has the following advantages:

Lower physical equipment cost, lower maintenance costs.

11) Advanced Applications:

The most compelling aspect of converged voice/data networking may well be

the new generation of applications it enables. These applications include Web

enabled call canters, unified messaging and real-time collaboration. Other

examples include real-time multimedia video/audio conferencing, distance

learning, and the embedding of voice links into electronic documents. Three or

four years ago, the Internet was not ready for prime time as a medium for

commerce. But now it is. VoIP will be a valuable enhancemen t.

12) Opportunities

Many vendors offer the ability to incorporate Virtual Private Networking (VPN)

with relative ease into the IP Telephony solutions they provide. This allows any

transmission to be encrypted using a number of cryptographic techniques and

providing security by transmitting the communications through a 'tunnel' which

is set up using PPTP (Point-to-Point Tunnelling Protocol) before commencing

communications.IP Telephony allows companies to exploit Computer

Telephony Integration to its full extent.

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The convergence of communications technologies allows greater control over

communications, most vendors provide logging and accounting facilities

whereby all usage can be monitored.

13) Weaknesses (limitations):-

While there are many aspects of VoIP which provide considerable benefits, the

technology is still very young and problems remain. The following section

looks at some of the weaknesses of this technology and their consequences.

The Internet is not the best medium for real time communications.

Individual packets can take different routes and varying delays can be

encountered and packets lost in transit. Waiting for delayed packets or

retransmission of lost packets can result in considerable degradation of quality.

Long delays in transit can affect quality so much that the technology can

become unusable, though many vendors do have solutions which aim to negate

the degradationsuffered due to transitdelays.

While some standards have been set by the ITU, the technology is not fully

standardized and there is no guarantee that products from different vendors will

be interoperable. Some vendors are trying to resolve this problem by forming

groups and making guarantees about the products in the group but this is only a

partial solution - vendors outwith the group cannot guarantee interoperability.

Jitter:Jitter in technical terms is the deviation in or displacement of some aspect

of the pulses in a high-frequency digital signal. As the name suggests, jitter can

be thought of as shaky pulses. The deviation can be in terms of amplitude, phase

timing, or the width of the signal pulse.

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Jitter refers to non-uniform packet delays. It is often caused by low bandwidth

situations in VOIP and can be exceptionally detrimental to the overall QoS.

Variations in delays can be more detrimental to QoS than t he actual delays

themselves . Jitter can cause packets to arrive and be processed out of sequence.

RTP, the protocol used to transport voice media, is based on UDP so packets

out of order are not reassembled at the protocol level. However, RTP allows

applications to do the reordering using the sequence number and timestamp

fields.

Heavy congestion on the network can result in considerable degradation of

service as IP is not good at providing QoS (Quality of Service) guarantees.

Feedback to Lucent Technologies customers reflect this wor ry. Major

companies are planning to install IP Telephony capabilities at some point and

have carried out initial investigations, however:

Since only one physical network for both data and voice/fax transmissions is

required, failure of the network could be catastrophic, as all communications

capabilities are lost.

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14) Security issue:-

a)The concern:-

VoIP networks and devices are vulnerable to unique security threats and

exploits, because of the real-time nature of the traffic. In addition, many new

protocols and products make up the VoIP infrastructure, which traditional

security products and approaches are not designed to protect.

The flaws were discovered by VoIP security solutions vendor s (like VoIP

shield) which revealed the vulnerabilities to the public today.

Since VoIPshield Labs and like that labs are continuously finding new

vulnerabilities, they plan on monthly disclosures to VoIP equipment vendors

followed by public disclosure.

An interesting example of an identified Cisco VoIP vulnerability is shown

below:

In the above example, a potential attacker exploiting the Cisco Unified

Communication Manager (UCM) vulnerability related to its Disaster Recovery

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Net l t i ll ess t t e UCM by getti g t e remote shell on the

attacker's machine.

Subsequently the attacker coul either disable UCM completely, download all

the information from UCM to the attacker's machine or upload an executablefile to the UCM.

Then the attacker could force allthe Cisco softphones connected to this UCMto

reboot and download that executable file.

It l t, j w .

Once the executable is downloaded and executed an attackeris able to have full

access to the users laptop running the softphone.

b) T counter measure products:-

Each product draws on VoIPshields proprietary database of VoIP-specific

vulnerabilities and signatures. They are somewhat analogues to Anti viruses.

Some ofthem are:-

VoIP Vulnerability Assessment (VVA) and penetration testing tool has been

deployed by enterprise security and telecom professionals in many network

scenarios and is being used for both risk assessment, compliance focused

auditing as well as operationally by security staff to ensure their Voice over IP

network are secure at alltimes.

VoIPguard is the industrys first VoIP Intrusion Prevention System (VIPS) with

comprehensive protection for Voice over IP systems from the leading VoIP

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vendors. V IPguard provides effective protection against known and new

attacks aimed at compromising the security of VoIP networks.

VoIP PB monitoring tool provides around the clock monitoring for hardware

failures and systems events generated by VoIP IP Public branch exchanges

(PB ). VoIPmonitor empowers PB administrators to selectively forward

events in real-time to destinations such as in-house NetworkOperations Centers

(NOC), Network Management Systems (NMS) and Operational Support

Systems (OSS) while preserving local administration processes without the

need for external monitoring services.

VoIP PB configuration management tool enables PB administrators to

quickly catalog, assess and report on configuration status and configuration

changes as they apply to regulator requirements. It allows the PB administrators detect configuration issues and changes improving overall

security and reliability of VoIP installations.

.. and many more companies are providing t e similar

solutions.some oft em are:-

Nexti a

Vocality

DCP SE VICES INC

Quintum Technologies, LLC.

SecureWorks, Inc.

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CREDANT Technologies

15) VoIP Equipment and Solution Vendors

Avaya

Avaya is the leader on the VoIP market. It has a vast variety of equipment and

solutions including IP phones, media gateways, routers, communication servers,

PBXs, wireless phones, voice application etc. Its hottest product is the IP Office

platform and communications system.

Nortel

Nortel is one of the oldest vendors around - it has been here since 1995. The

range of products it offers is more or less like Avaya, but it is more reputed for

its PBXs. Nortel is the first vendor to provide an end-to-end IP telephony

solution certified by U.S. Defence Department Joint Interoperability Test

Command (JITC) in 2004.

Cisco

Before VoIP, Cisco has been around as a networking vendor giant. Now, it is a

leading player in the VoIP equipment arena, with good IP Phones, routers and

other devices and solutions. Cisco owns Linksys, which is also well known on

the market.

Shoretel

Shoretel is a fast-growing vendor providing complete IP telephony solutions

and PBXs. Shoretel's strong points are performance and ease of installation and

use.

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Siemens

Siemens is another giant in technology which has extended its reach to VoIP

and unified communications. It provides phones, PBXs and ... just anything

concerning communication.

Mitel

Mitel is a global provider of communications solutions for enterprises and small

business. It aims at blending good human interface with powerful infrastructure.

Mitel brands include SX and ICP series.

Asterisk

Asterisk is not hardware, but a software PBX that can run on Linux, Unix,MacOS and some other operating systems. It is open source (meaning free) and

is extremely flexible and very robust.

Taridium

Taridium is a fast growing open standards VoIP solution provider. Taridium's

offering ranges from managed VoIP services for small and medium sized

businesses through to high capacity telephony sol utions for large enterprises and

service providers.

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Here are some of the other providers:

Talkswitch

Toshiba

Fonality

3Com

Polycom

Alcatel

Lucent (now owned by Avaya)

Linksys (now owned by Cisco)

D-Link

Sipura (now owned by Cisco)

Grandstream

Snom

NetGear

ZyXEL

Belkin

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16)Conclusion :-

Without a doubt, the data revolution will only gain momentum in the coming

years, with more and more voice traffic moving onto data networks. Vendors of

voice equipment will continue to develop integrated voice and data devices

based on packetized technology. Users with ubiquitous voice and data service

integrated over one universal infrastructure will benefit from true, seamless,

transparent interworking between voice and all types of data. It is not Voice

over IP, it is Everything over IP

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17) REFERENCES

Journals

An OPNET-based Simulation Approach for Deploying VoIP by K. SalahandA. Alkhoraidly

VoiceoverIP (VoIP) bySpirent Communications

Conference Recomendations

Internet telephony fall 2005- conference - LOS ANGELES

ITEXPO- Conference

Books

Switching to VOIP by Ted Wallingford 2005 ORELLY Publications.

Hacking Exposed VOIP byDavid Endler, MarkCollier, Endler 2007 TMH

Publications

Website:-

http://www.voip.com

http://www.networkworld.com

http://www.itu.int

VoIP Equipment and Solution Vendors ByNadeemUnuth, About.com

Guide