Voip

CHAPTER 1 1. INTRODUCTION 1.1 What is Voice Over Internet Protocol? Voice over Internet Protocol is a general term for a family of transmission technologies for delivery of voice communications over internet protocol networks such as the internet or other packet-switched networks. Other terms frequently encountered and synonymous with voice over internet protocol are internet protocol telephony, internet telephony, voice over broadband, broadband telephony, and broadband phone. internet telephony refers to communications services — voice, facsimile, and/or voice-messaging applications — that are transported via the internet, rather than the public switched telephone network. •

PC to PC

Fig 1.1:- Alternative voice over internet protocol Architectures

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The basic steps involved in originating an Internet telephone call are conversion of the analog voice signal to digital format and compression/translation of the signal into internet protocol packets for transmission over the internet; the process is reversed at the receiving end. Voice over internet protocol systems employ session control protocols to control the set-up and tear-down of calls as well as audio codecs which encode speech allowing transmission over an internet protocol network as digital audio via an audio stream. Codec use is varied between different implementations of voice over internet protocol (and often a range of codecs are used); some implementations rely on narrowband and compressed speech, while others support high fidelity stereo codecs. Voice over Internet Protocol is a technology for communicating using “Internet protocol” instead of traditional analog systems. Some voice over internet protocol services need only a regular phone connection, while others allow you to make telephone calls using an Internet connection instead. Some voice over internet protocol services may allow you only to call other people using the same service, but others may allow you to call any telephone number - including local, long distance, wireless, and international numbers. Voice over internet protocol is mainly concerned with the realization of telephone service over internet protocolbased networks such as the internet and intranet. Internet protocol telephony is currently breaking through to become one of the most important service on the net. The actual breakthrough was made possible by the high bandwidth available in an intranet and, increasingly, on the internet. Another fundamental reason is the cost associated with the various implementations.

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Phone to Phone via the Internet

Fig 1.2:- voice over internet protocol Architectures The public telephone network and the equipment makes it possible are taken for granted in most parts of the world. Availability of a telephone and access to low-cost, high quality worldwide network is considered to be essential in modern society (telephone are even expected to work when the power off).There is, however, a paradigm shift beginning to occur since more and more communication is in digital form and transported via packet networks such as internet protocoland Frame Relay frames. Since data traffic, there has been considerable interest in transporting voice over data networks. Support for voice communications using the internet protocol, which is usually just called “Voice over internet protocol” or voice over internet protocol, has become especially attractive given the low-cost, flat-rate pricing of the public Internet. In fact, toll quality telephony over internet protocol has now become one of the key steps leading to the convergence of the voice, video, and data communications industries. The feasibility of carrying voice and signaling message over the internet has already been demonstrated but delivering high-quality commercial products, establishing public services, and convincing users to buy into the vision are just beginning.

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Phone to Internet to Gateway to PSTN

Fig 1.3:- Alternative voice over internet protocol Architectures

1.2 Definition Voice over internet protocol can be defined as the ability to make telephone calls and to send facsimiles over internet protocol- based data networks with a suitable quality of service and a much superior cost/benefit. Equipment producers see Voice over internet protocol as a new opportunity to innovate and copete. The challenge for then is turning this vision into reality by quickly developing new voice over internet protocol-enabled equipment. For Internet service providers, the possibility of introducing usage-based pricing and increasing their traffic volumes is very attractive. Users are seeking new types of integrated voice/data applications as well as cost benefits. Successfully delivering voice over packet networks presents a tremendous opportunity; however, implementing the products is not as straightforward a task as it may first appear. This document examines the technologies, infrastructures, software, and systems that will be necessary to realize voice over internet protocol on a large scale. The types of

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applications that will both drive the market and benefit the most from the convergence of voice and data networks will be identified.

1.3 History of Voice Over Internet Protocol Voice over Internet Protocol owes its existence to the difference in price between longdistance connections and the use of data networks. This technology uses data networks such as the Internet to transmit voice information from a simple PC. A telephone conversation is conducted via microphone and loudspeaker connected to the sound card. Microsoft NetMeeting is the most common Internet telephony program. Its features also include Internet video communication (image telephony). Or, a specially adapter can be used to hook standard telephones up to the data network. All devices that support the same standard can be connected over one data network. Gateways are also available for connecting these devices to telephones in the normal telephone network. These possibilities have led to the creation of IPbased telephone systems using voice over internet protocol. The development of voice over internet protocol technology is summarized and predicted in the following: 1995=> The year in which to PCs are connected using PC software 1996=> The year of the IP telephony client. 1997=> The year of the Gateway. 1998=> The year of the Gatekeeper. 1999=> The year of the Application. .

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CHAPTER 2 2. Voice Over Internet Protocol Components The components of VoIP include: end-user equipment, network components, call processors, gateways and protocols.

2.1End-user equipment It is used to access the VoIP system to communicate with another end point. Connection to the network may be physically cabled or may be wireless. The end-user equipment may be a phone that sits on a desk or a softphone that is installed on a PC.Functions include voice and possibly video communication, and may contain instant messaging, monitoring and surveillance capabilities. 7 Though end-user equipment is often deployed on an internal, protected network, it is usually is not individually protected by other devices (firewalls) and may be threatened if the equipment has vulnerabilities. The threat, of course, is also dependent on the level of security that exists on the internal network. If the device is allowed to reach or can be reached from a public or unprotected network, there may be threats that are not normally found on the internal network. Softphone software may have vulnerabilities, there may be vulnerabilities in the operating system it is running on, and there may be vulnerabilities of other applications running on the operating system. Patching operating system, soft phone software and those other applications can help mitigate the risk of any threats that are present. Additionally, some enduser equipment may have firmware upgrades that can be applied or may be able to obtain updated software during registration. For operating system based Voice over internet protocol solutions, consideration should be given to virus detection and host based firewalls as well as host-based intrusion detection. Centralization of management of these security components is best, allowing the users of the solution to focus on their duties instead of security details, increasing productivity.

2.2Network components It include cabling, routers, switches and firewalls. Usually the existing IP network is where a new Voice over internet protocol system is installed. The impact on the internet protocol network is greater than merely adding more traffic. The added traffic has more of an urgency to reach its destination than most of the data traffic that is already supported. Switches, routers and

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firewalls will need to recognize and act on Voice over internet protocol data in order to keep latency down. Additional security measures, addressed later, will complicate this process. Performance can be gained by separating the data traffic from the voice over internet protocol traffic by putting them on different virtual local area networks. This allows management of the data to be segregated so it can be handled based on data type. Since the voice over internet protocol data must have a higher level, isolation of the data types via virtual local area network can help increase the performance at the cost of that on other virtual local area network. This cost may be very low to the other applications. Although virtual local area network should not be relied on alone, they will add a layer of security. The ability to listen to, or sniff, the network, potentially allows the hacker to monitor calls and manipulate the voice over internet protocol system. It is generally more difficult for a hacker to sniff or interfere with the voice traffic from the data virtual local area network when the voice traffic is on its own virtual local area network, but it can be done by manipulating the routing of the network. Encryption can also help defend against sniffing. Another internetprotocol network concern is network slowdowns that might increase latency, jitter or packet loss. Slowdowns can be caused for many reasons including configuration issues, denial of service attacks or high bandwidth utilization by other systems on the network. Configuration issues are probably best addressed with education and checking mechanisms, such as having a co-worker verify configurations. Denial of service attacks are difficult to defend against, but may be reduced by filtering the traffic that can communicate on the network to be only that which is allowed. This may prove difficult due to the use of random ports by voice over internet protocol. Regular network bandwidth analysis can help with tuning of a network and helps with capacity planning. Being aware of bandwidth growth trends helps network administrators know when bandwidth needs to be addressed. Voice over internet protocol suffers from most of the same internet protocol network vulnerabilities as other systems. A well secured internal network is the first step to protecting the voice over internet protocol system as it was for the pre-existing internet protocol network. Care must be taken to ensure security solutions keep latencies low or the security solution itself may prove to be a denial of service.

2.3 Call processor 7

These functions can include phone number to internet protocol translation, call setup, call monitoring, user authorization, signal coordination, and may help control bandwidth. 6 Call processors are usually software that runs on a popular OS. This leaves it open to network attacks for the vulnerabilities of the given OS, the vulnerabilities of the application and other applications running on the operating system. 2.4 Gateways It can be categorized into three functional types: Signaling Gateways,Media Gateways and Media Controllers. In general, they handle call origination and detection and analog to digital conversion. Signaling gateways manage the signal traffic between an internet protocol network and a switched circuit network, while media gateways manage media signals between the two. Media Gateway Controllers manage traffic. The most common gateway protocols are megaco. Both are composites or derivations of previously but now less used protocols.6 Vulnerabilities can exist between the internal internet protocol network and the “gated”, circuit switched network. Care should be taken to ensure any vulnerabilities are mitigated. Gateway communication should be secured with internet protocol Sec to prevent interference with calls and to prevent unauthorized calls from being setup. The gateway itself is vulnerable to internet protocol based attacks and can be mitigated by using internet protocol Sec and by removing any unnecessary services and open ports, as should be done with any server.

CHAPTER 3 3.working 8

Voice over internet protocol converts the voice signal from your telephone into a digital signal that can travel over the internet. If you are calling a regular telephone number, the signal is then converted back at the other end. Depending on the type of voice over internet protocol service, you can make a voice over internet protocol call from a computer, a special voice over internet protocol phone, or a traditional phone with or without an adapter. In addition, new wireless "hot spots" in public locations such as airports, parks, and cafes allow you to connect to the Internet, and may enable you to use Voice over internet protocol service wirelessly. If your Voice over internet protocol service provider assigns you a regular telephone number, then you can receive calls from regular telephones that don’t need special equipment, and most likely you’ll be able to dial just as you always have.

Fig 3.1:-voice over internet protocol work service The exploratory nature of this study produced focus groups as an appropriate method for data collection. Our overarching goal was to improve our understanding of how Latino voice over internet protocol users employ the technology and why they select certain voice over internet protocol services and providers. In addition, we wanted to learn about Latinos not connected to the Internet-what they know about voice over internet protocol and why they are

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not online. Moreover, we sought to learn whether the lower cost of telephone calls associated with voice over internet protocol are enough of an incentive for non-Internet users to get online, and, if so, under what conditions. Four focus groups of 9 to 12 participants were held in Los Angeles in August 2008 (total sample size, N = 43). Two of the focus groups consisted of Latinos who are Internet users and have either heard of or used some form of voice over internet protocol technology and service. The other two groups consisted of Latinos who reported that they do not use the Internet. The study participants were residents of Glendale, Cudahy, Huntington Park, and South Gate, cities that are part of Los Angeles County, a large metropolitan area with a significant and diverse Latino population. Glendale is the third largest city in Los Angeles County and it is the most ethnically diverse area of the four in this study. Twenty percent (20%) of the population is Latino, 21% is Armenian, 35% is White (non-Armenian, non-Hispanic), and 16% is Asian from different countries of origin. Approximately 40% of the residents are homeowners. The median household income is $41,800 (U.S. Census, 2000). In Glendale, 70% of Latinos are connected to the Internet. This is one of the highest connectedness rates across Latino communities in Los Angeles County (Wilkin et al., 2007). The contiguous cities of Huntington Park, South Gate, and Cudahy are in Southeast Los Angeles. Over 90% of the population is Latino, and most residents are of Mexican origin. The median household income is about $32,000, and only 24% of the population is connected to the Internet.

CHAPTER 4 4. PROTOCOL There are several protocols used for voice over internet protocol but two are most common. They are H.323 and Session Initiation Protocol.

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Fig 4.1:- Protocol Layers 4.1 H.323 H.323 is a protocol suite specified by the International Telecommunications Union that lays a foundation for internet protocol based real-time communications including audio, video and data.8 H.323 allows for different configurations of audio, video and data. Possible configurations include audio only, audio & video, audio & data and, audio, data and video. H.323 does not specify the packet network or transport protocols. This standard specifies four kinds of components: Terminals, Gateways, Gatekeepers and Multi-point Control Units .Terminals are the end-user equipment discussed above. Gateways handle communication between unlike networks with protocol translation and media format conversion. Gatekeepers provide services such as addressing, authorization and authentication, accounting functions and call routing. Multi-point Control Units handle conferencing. The International Telecommunications Union defines the H.323 zone that consists of terminals, gateways, Multi-point Control Units, and a gatekeeper. The gatekeeper manages the

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zone. H.323 uses different protocols to manage different needs. There are audio codecs and video codecs that encode and decode the audio and video data. H.225 covers registrations,

Fig 4.2:- H.323 Architecture admissions & status and call signaling. Realtime Transport Control Protocol handles various functions between the endpoints and the gateway, including registrations and admission control as its name implies. It also manages changes in bandwidth and disengage procedures. A Realtime Transport Control Protocol channel is opened, prior to opening other channels, between the gateway and endpoint whereby Realtime Transport Control Protocol messages are passed. Call signaling channels are opened between endpoints and between an endpoint and a gatekeeper. They are used to set up connections. Call setup and termination uses Q.931.9 H.245 is for channel negotiations such as flow controls and general commands and H.235 specifies security. Real-time Transport Protocol is used to transport data, typically via user datagram protocol and provides a timestamp, sequence number, data type and ability to monitor delivery. Realtime Transport Control Protocol is used mainly to monitor quality and manage synchronization. As mentioned above, the H.235 protocols of H.323 are for security profiles. These standards address authentication, integrity, privacy, and non-repudiation 10 and are expressed as Annexes to H.235 Version 2. They are Annexes D, E & F as follow:

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 Annex D provides message integrity and/or authentication using symmetric keys. It also

has a voice encryption option.  Annex E provides authentication, message Integrity and non-repudiation using

asymmetric methods.  Annex F is a hybrid of Annex D and Annex E providing authentication, non-repudiation

and message integrity. The four security goals, authentication, integrity, privacy, and non-repudiation are accomplished with the four mechanisms: configuration, authentication, key exchange and encryption. During the initial stage of configuration, the device is authorized to the network and may be authenticated. Integrity and privacy are accomplished through encryption using symmetric or asymmetric keys. A signature is attached to gain the fourth goal of nonrepudiation. H.323 Security Concerns Using H.323 to setup voice over internet protocol connections is a complicated process that is made more complex by adding security measures. Many of the protocols used with the H.323 suite use random ports causing problems securing through firewalls but may be able to be mitigated by using direct routed calls. Since the ports required for H.323 are not set, a filtering firewall would have to have all possibly needed ports left open. Therefore, the firewall would need to be H.323 aware allowing communication without opening up the firewall to other traffic. A stateful firewall and/or application firewall is required to ensure consistency of the characteristics of connections. Network Address Translation is a problem for H.323 because the internet protocol and port on the internet protocol header do not match those in the messages. This may be mitigated with an H.323 aware firewall. Additionally, there will be restrictions in other security measures if Network Address Translation is involved. 4.2 Session Internet Protocol Session Initiation Protocol is a signaling protocol specified by the Internet Engineering Task Force used to set up and tear down two-way communications sessions. session internet protocol operates on the application level so can be used with several different protocols. Using tansmission control protocol allows use of providing more security whereas,user datagram protocol allows for faster, lower latency, connections. Usual components of an Session Internet Protocol system are the user agent, proxy server, registrar server, and the redirect server. The

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usual components software contains client and server components. The client piece makes outgoing calls and the server is responsible for receiving incoming calls. The proxy server forwards traffic, the registrar server authenticates requests, and the redirect server resolves information for the usual components client. The endpoints begin by connecting with a proxy and/or redirect server which resolves the destination number into an internet protocol address. It then returns that information to the originating endpoint which is responsible for transmitting the message directly to the destination. A security advantage of session internet protocol is that it uses one port. The main concerns for security of are confidentiality, message integrity, nonrepudiation, authentication and privacy. New security mechanisms were not created for session internet protocol instead, session internet protocol uses those provided by Hyper Text Transfer Protocol and Simple Mail Transfer Protocol as well as Internet Protocol Security.

Fig 4.3:- Self-Provided Customer Architecture

Signal confidentiality is best provided with full encryption, however, since some session internet protocol message fields must be read and/or modified by some proxies, care must be

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taken and possibly other methods used. If however, the proxy can be trusted, then encryption at the transport and/or network layers may be the best solution. Security at the transport and networking layers accomplishes full packet encryption using internet protocol sec. TLS had been used, but has been deprecated. Full encryption requires support of the encryption method at each end point where it is implemented. hyper text transfer protocol authentication uses the 401 and 407 response codes and header fields. This provides a stateless challenge-base mechanism for authentication whereby the hallenge and user credentials are passed in the headers. When a proxy or usual components receives a request, it may challenge to ensure the identity of the sender. Once identity has been confirmed the receiver should also verify that the requester is authorized. Details of this “digest” method may be found in rfc 326112. Secure/Multipurpose Internet Mail Extension is an enhancement to Multipurpose Internet Mail Extension that replaces Pretty Good Privacy. Since Multipurpose Internet Mail Extension bodies are carried by session internet protocol, session internet protocol may use to enhance security, Multipurpose Internet Mail Extension contains components that can provide integrity and encryption for Multipurpose Internet Mail Extension data and as rfc 2633 states Multipurpose Internet Mail Extension can be used for “authentication, message integrity and non-repudiation of origin (using digital signatures) and privacy and data security (using encryption). Multipurpose Internet Mail Extension is useful when full encryption of the packet is not feasible due to the need of network components to use data from the header fields. User identification is done via certificate belonging to the user that is compared to the header information. Integrity of the message is verified by matching the information in the outside header with that of the inside header. Normally, Multipurpose Internet Mail Extension is used to encrypt Session Description Protocol but there may be requirements to encrypt certain header components. Session internet protocol can provide header privacy by encapsulating the entire message using Multipurpose Internet Mail Extension type message/sip. If used for anonymity the message will need to be decrypted before the certificate can be identified and consequently validated. Session internet protocol Security Concerns hyper text transfer protocol digest does not provide the best integrity. Without Multipurpose Internet Mail Extension, spoofing of the header would not be difficult. Multipurpose Internet Mail Extension requires a public key infrastructure. Since certificates are associated with users, moving from one device to another may be difficult. With Multipurpose Internet Mail Extension there may be issues with firewalls or other proxy devices that may

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require viewing and/or changing session internet protocol bodies. There is information in session internet protocol headers that may be considered sensitive, i.e. an unlisted phone number. Consideration may need to be given to providing per-user options that allow protection of this information. Session internet protocol and H.323 both use protocols that may use random ports requiring that the firewall be able to open and close ports as required. An H.323 or session internet protocol aware firewall may be required. As with H.323, network address translation presents problems for session internet protocol.

4.3 Network Address Translation Network Address Translation allows one network address to be translated at a gateway between two networks into another address so that the packet will have a valid source address on the network it is on. Most commonly Network Address Translation is used to change private internet protocol addresses into public, Internet routable, internet protocol addresses. Ports may also be translated. Network Address Translation traversal is usually only a concern if end-user devices connect directly with an external network or if they connect to the internal network from an external network.

Fig 4.4:- Network Address Translation Architecture

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Network Address Translation is a layer of security because it hides the real addresses on the internal network from the public network. Network Address Translation can however, be a problem, because the routing device does not know the actual internet protocol address of the device. The information defining the endpoint is in the header. The routing device must be able to read the header and in some cases (i.e. with proxy firewalls) change it. This is hampered when encryption is used. The best solution is to not use Network Address Translation if at all possible. By removing the issue, the problem disappears, though another problem may present itself. When Network Address Translation is required, care must be taken to select application and proxy firewalls that handle the implementation or, alternatively, consider a service offered by the public networks. 4.4 Denial of Service Denial of Service is caused by anything that prevents the service from being delivered. A Denial of Service can be the result of unavailable bandwidth or voice over internet protocol components being unavailable. Many things can cause a Denial of Service including: a network getting congested to a level that it cannot provide the bandwidth needed to support the application; servers not capable of handling the traffic; extraneous services may be running that reduce the available resources to the server; malicious programs such as viruses and Trojan horses; other malicious programs with the purpose of causing Denial of Service or hacking activity.

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Fig 4.5:- PSTN Architecture

If Denial of Service is caused by bandwidth constraints, potential solutions are increasing the bandwidth and/or isolating the voice over internet protocol traffic so that it gets service first. Various methods of ensuring servers don’t stop working, such as failover methods like clustering, can help reduce Denial of Service from failing components. Each component of the voice over internet protocol system offered by the vendor, should be evaluated, removing those that are unnecessary. Server size should be planned such that all desired vendor services and expected traffic can be supported, adding some percentage for expected growth. Defending against malicious programs and activity is more difficult but should begin with applying appropriate patches in a timely manner, and installing virus protection with frequent updates. In addition, installation designers should consider a host based firewall, intrusion detection and/or intrusion prevention. Defense against Denial of Service attacks of public servers can best be done by locating the device with the public available internet protocol addresses

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behind a firewall or other device that only allows communication from trusted sources. Also, harden the operating systems in use, removing all unnecessary services and applications from the servers and workstations, patching, etc. 4.5 Other Concerns Additional concerns of a VoIP system that need to be considered are databases, web servers, additional VoIP services offered by the vendor, protocol stacks, access to public or unknown networks, physical security and electrical power. Databases are needed at some point of the VoIP implementation to store and retrieve information as needed to accommodate various functions of the system. Database security principles should be applied including changing the default administrator password, patches as they become available, and best practices concerning access to the database, especially from sources other than the voice over internet protocol system. A common feature of end-user equipment is a web browser, the purpose of which is to provide additional functionality and increased productivity. A voice over internet protocol system server may have a web browser interface allowing management. If supported, patch the device when the patch becomes available and use as strong authentication as can be supported. Each vendor, having their own implementation of voice over internet protocol system, may require any number of services to run on a server to support their product. As mentioned before, keep patches up to date and turn off all unneeded services. If the risk is great enough, consider encryption and/or protection by another device such as a firewall. The voice application and the operating system have similar vulnerabilities and should be patched as well. If the voice over internet protocol system stays within a secured network and only connects to the public network through a gateway, the gateway is a vulnerability that needs addressing. Deploy the hardened gateway behind an appropriate firewall, i.e. one that is aware of the protocols used. voice over internet protocol system must process the protocols that it supports so it needs to have some implementation of a network stack. Stack implementations are written by the vendor orurchased from another vendor. With the latter, all vendors that purchased a specific vendor’s stack will share the same vulnerabilities. Patch if necessary, when patches become available. Ensure that the components are physically secure. Access to the box allows ownership. There are many methods of compromising a device, depending on the device and the underlying operating system, with physical access. Good security practices include removing the a-disk and the CD-

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ROM from the boot list and password protect the configuration. If a component is unavailable, then there is a denial of service.

CHAPTER 5 5. APPLICATIONS AND BENEFITS Voice communication will certainly remain a basic from of interaction for all of us. The public switched telephone network mply cannot be replaced, or even dramatically changed, in the short term (this may not apply to provide voice networks, however). The immediate goal for voice over internet protocol service providers is to reproduce existing telephone capabilities at a significantly lower “total cost of operation “and to offer a technically competitive alternative to the public switched telephone network.

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Fig 5.1:- Voice over internet protocol infrastructure It is the combination of voice over internet protocol with point-of-service applications that shows great promise for the longer term. The first measure of success for voice over internet protocol will be cost saving for long distance calls as long as there are no additional constraints imposed on the end user. For example, callers should not be required to use a microphone on a pc. voice over internet protocol provides a competitive threat to the providers of traditional telephone service that, at the very least, will stimulate improvements in cost and function throughout the industry implemented using an internet protocol network. This design would also apply if other types of packet networks (such as frame relay) were being used. Some example of voice over internet protocol applications that are likely to be useful would be: 5.1 Public switched telephone network gateways Interconnection of the Internet to the public switched telephone network can be accomplished using a gateway, either integrated into or provided as a separate device. A PCbased telephone, for example, would have access to the public network by calling a gateway at a point close to the destination (thereby minimizing long distance charges). 5.2 Internet-aware telephones

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Ordinary telephones (wired or wireless ) can be enhanced to serve as an Internet access device as well as providing normal telephony. Directory services, for example, could be accessed over the Internet by submitting a name and receiving a voice. 5.3 Internet-office trunking over the corporate intranet Replacement of tie trunks between company-owned using an private branch exchange Intranet link would provide economies of scale and help to consolidate network facilities. 5.4 Remote access from a branch (or home) office A small office (or a home office) could gain access to corporate voice, data, and facsimile services using company’s Intranet (emulating a remote extension for a private branch exchange, for example). This may be useful for home-based agents working in a call center. 5.5 Voice calls from a mobile PC via the Internet One example would be using the Internet to call from a hotel instead of using expensive hotel telephones. This could be ideal for submitting or retrieving voice messages. 5.6 Internet call center access Access to call center facilities via the Internet is emerging as a valuable enable adjunct to electronic commerce applications. Internet call center access would enable a customer who has questions about a product being offered over the Internet to access customer service agents online. Another voice over internet protocol application for call centers is the interconnection of multiple call centers. Widespread deployment of a new technology seldom occurs without a clear and sustainable justification, and this is also the case with voice over internet protocol. Demonstrable benefits to end users are also needed if voice over internet protocol products (and services ) are to be a long-term success. Generally, the benefits of technology can be divided into the following four categories:  . Cost Reduction. Although reducing long distance telephone costs is always a popular

topic and would provide a good reason for introducing voice over internet protocol, the actual saving over the long term are still a subject of debate in the industry. Flat rate pricing is available with the Internet and can result in considerable savings for both voice and facsimile (at least currently). It has been estimated that up to 70% of all calls to Asia are to send faxes, most of which could be replaced by internet protocol. These lower prices, however, are based on avoiding telephony access charges and settlement fees rather than being a fundamental reduction in resources costs. The sharing of equipment

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and operations costs across both data and voice users can also improve network efficiency since excess bandwidth on one network can be used by the other, thereby creating economies of scale for voice (especially given the rapid growth in data traffic ).  . Simplification. An integrated infrastructure that supports all forms of communication

allows more standardization and reduce all forms of communication allows more standardization and reduces the total equipment complement. This combined infrastructure can support dynamic bandwidth optimization and a fault tolerant design. The difference between the traffic patterns of voice and data offer further opportunities for significant efficiency improvements. 

Consolidation. Since people are among the most significant cost elements in a network, any opportunity to combine operations, to eliminate points of failure, and to consolidate accounting systems would be beneficial.. Universal use of the internet protocol for all applications holds out the promise of both services and security services may be more easily shared. s Even though basic telephony and facsimile are the initial applications for voice over internet protocol, the longer term benefits are expected to be derived from multimedia and multi service applications. For example, Internet commerce solution can combine WWW access to a call center agent from the PC. Needless to say, voice is an integral part of conferencing systems that may also include shared screens, white boarding, etc. Combining voice and data features into new application will provide the greatest returns over the longer term. Although the use of voice over packet networks is relatively limited at present, there is considerable user interest and trials are beginning. End user demand is to grow rapidly the next five years. Frost & Sullivan and other research firms have estimated that the compound annual growth rate for IP-enabled telephone equipment will be 132% over the period from 1997 to 2002 (from $47.3 M in 1997 to $3.16B by 2002). It is expected that VoIP will be deployed by 70% of the Fortune 1000 companies by the year 2000. Industry analysts have also estimated that the annual revenues for the IP fax gateway market will increase from less than $20M in 1996 to over $100M by the year 2000. It is clear that a market has already been established and there exists a window of opportunity for developers to bring their products to market.

5.7 Product Development Challenges

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The goal for developers is relatively simple: add telephone calling capabilities ( both voice transfer and signaling) to internet protocol-based networks and interconnect these to the public telephone network and to private voice networks in such as way as to maintain current voice quality standards and preserve the features everyone expects from the teleph Fig illustrates an overall ;

Fig 5.2:- overall architecture for VoIP an product developer arise Architecture for voice over internet protocol an Suggests that the challenges for the product developer arise in five specific areas: 1. Voice quality should be comparable to what is available using the public switched telephone network, even over networks having variable levels of operating system. 2. The underlying internet protocol network must meet strict performance criteria including minimizing call refusals, network latency, packet loss and disconnects. This is required even during congestion condition or when multiple users must share network resources. 3. Call control (signaling) must make the telephone calling process transparent so that the callers need not know what technology is actually implementing the service. 4. public switched telephone network service interworking (and equipment interoperability) involves gateways between the voice and data network environments. 5. System management, security, addressing (directories, dial plans) and accounting must be provided, preferably consolidated with the public switched telephone network operation support systems.

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CHAPTER 6 6. Conclusion Data traffic has traditionally been forced to fit onto the voice network (using modems, for example). The Internet has created an opportunity to reverse this integration strategy – voice and facsimile can now be carried over internet protocol networks, with the integration of video and other multimedia applications close behind. The Internet and its underlying internet protocol suite have become the driving force for new technologies, with the unique challenges of realtime voice being the latest in a series of developments. Telephony over the Internet cannot make compromise in voice quality, reliability, scalability, and manageability. Future extensions will include innovative new solutions including conference bridging, voice/data synchronization, combined real-time and message-based services, text-to- speech conversion and voice response systems. The market for voice over internet protocol products is established and is beginning its rapid growth phase. Producers in this market must look for ways to improve their time-to market

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if they wish to be market leaders. Buying and integrating predefined and pre-tested software (instead of custom building everything) is one of the options. Significant benefits of the “buy vs. build “ approach include reduced development time, simplified product integration, lower costs, off-loading of standard compliance issues, and fewer risks. Software that is known to conform to standards, has built-in accommodation for difference in national telephone systems, has already been optimized for performance and reliability, and has “plug and play” capabilities can eliminate many very time-consuming development tasks.

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REFERENCES [1] ISDN am computer, Torsten Schulz, Springer Verlag Berlin, 1998 [2] Delivering Voice over IP Networks, Daniel Emma Minoli, John Wiley & Sons, Inc., 1998 [3] LAN line –Telecommunication Spezial, Awi Verlag, V/1998 [4] PC Professionell – Telefonieren im IP-Netz, ZIFF-DAVIS Verlag, November 1998 [5] Voice over IP(VOIP) Technology Review, Brendan Murphy, May 1999. [6] Babbage, R., Moffat, I., O’Neill, A., & Sivaraj, S. (1997). Internet phone —changing the telephony paradigm ? British Telecommunications Technology Journal, 15 (2), 145-157. [7] Ball-Rokeach, S. J. (1985). The origins of individual media system dependency: A sociological framework. Communication Research, 12, 485-510. [8] Bernstein Research (2006).Boyer, M., & Mercier, C. (2005). VoIP regulation in Canada. Centre Interuniversitaire de Recherche en Analyse des Organizations (CIRANO), Scientific Series. Available via: http://econpapers.repec.org/paper/circirwor/2005s-36.htm. [9] Cha, J. (2006, April). Competitive strategy in the new VoIP market: the adoption and commercialization of VoIP services by MSOs, Telcos, and independent providers. Submitted to the National Cable and Telecommunications Association Academic Seminar. [10] Conradie, D. P., Morris, C., & Jacobs, S. J. (2003). Using communication and information technologies (ICTs) for deep rural development in South Africa, Communication, 29 (3), 199217. [11] Jie Li Qi-Fan CuiColl. of Commun. Eng., Hangzhou Dianzi Univ Publication Date: 25-28 June 2006 Volume: 3, On page(s): 1782-1785 Location: Guilin, ISBN: 0-7803-9584-0 INSPEC Accession Number: 9319626 Digital Object Identifier: 10.1109/ICCCAS.2006.285019 Current Version Published: 2007-01-15

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