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VoIP (Voice over Internet Protocol) is an internet protocol handset where a group of facilities are utilized to run and transmit voice data via internet. VOIP transfers information via digital form in separate packets instead of regular circuit dedicated procedure of PSTN (Public Switched Network). The cost of call prices are minimum when compare to normal handsets, these are considered as the benefits of both VOIP and internet telephony (Thomas Porter, 2006). Handset services are substitute of traditional telephone which are provided by VOIP as it is available for minimum rates when compare with the normal companies. There are several many technologies which are similar and provide same services like VoIP, but VoIP has the ability to overcome these problems which leads to usage of VoIP has been prominently increasing. Public Switch Telephone Network (PSTN) is the individual tools that offer services similar to VOIP (Collins, 2005). PSTN usually offers voice conversation but circuit setup needs a physical communication for managing calls which becomes tough in the network. Security is provided efficiently by VoIP using encryption, decryption and cryptographic techniques which eliminate the unauthorized access. VoIP provides clarity over call, reduces cost for long call and efficient clarity is voice for communicating with the clients (Pelin Aksoy and Laura DeNardis, 2007). Many organizations are implementing this technology because of its advantages and helps in improving the productivity of organization. The cost of organization reduces by the implementation of VoIP, as it reduces cost of traditional telephone charges. By keeping VoIP in homes or in business areas it offers variety of benefits by offering low rates for worldwide calls etc, and it's very easy to use (Doug Lowe, 2008). VoIP provides good Quality of Service (QoS) for the clients in voice communication (Anthony T. Velte, 2004). Hence from this data it can be recognised that the rise in the usage of VoIP depends on the user necessity. VoIP provides clarity over call, reduces cost for long distant call and clarity of voice is efficient for communicating with the clients. Many organizations are implementing this technology because of its advantages and helps in improving the productivity of organization.
VoIP is the latest inventory in the communication field. The easy function is that which sells itself is the reason that it makes calls using the Internet. Obsolete advantages, VoIP is declared to be the best and the easy to make calls to international locations now-a-days (Marion Tracey, 2008). Also, easy set up and to use, the service can be found easily. Voice over IP is discovery in the world of communication. It made communication clearer and low in price. Now international calls are not very expensive. Everyone need internet connection with perfect device, to make web calls at any time anywhere in the world and at much reduced prices (Timothy V. Kelly, 2005). VoIP provides voice coding techniques which can be acceptable for all the networks. VoIP has the capability of providing confidentiality and security in communications. VoIP makes use of cryptography and encryption methods in order to provide security for voice communications. VoIP was introduced in voice communication, to overcome the problems in circuit switched network (James F. Ransome and John W. Rittinghouse, 2005). When one switch to an IP based communications system, it is being found that it increases productivity and allows time to focus on more important matters than IT. VOIP is soon attracting the Voice service for many organizations (Yogesh k. Dwivedi, Anastasia Papazafeiropoulou and Jyoti Choudrie, 2008). One can spend less money on travel by using online conferencing and other tools for better collaboration. Employees will have more ways to stay connected with easier ways to maintain access to the network, whether at work or at home. PSTN is also called as circuit switched network which offers conversation using physical paths from starting point to end terminal point. VoIP can avoid physical paths for communication by transmitting the data through packets (Juanita Ellis, Charles Pursell and Joy Rahman, 2003). Using VOIP client can select region codes and telephone numbers. In simple terms, this means that one in the same number by transferring it to a pure new VoIP. So, VoIP act as a transmission media that enables public to use internet for telephone calls.
VoIP Components and its Requirements
The main network parts of the VoIP are equal in functions to the switched network of the circuit. VoIP networks should do all the functions as PSTN done, and also able to perform the function of the gateway to the existing network of the public. VoIP architecture involves many components which help in the communication. The components involved in VoIP architecture are (Endler and Mark Collier, 2007):
- Ethernet Switch.
Ethernet Switch: Ethernet Switch receives the data and it has ability to check for the data or voice before passing it to destination. The networks of the computer, that is two or more than that, in a home or in the office or college make use for transferring data is Ethernet protocol. This switch is an essential device for the network of the customer, it makes the connection process easier and it gives guarantee to the computers of the clients that it connects to the internet in equal intervals of time with high speed.
Gateway: The device that changes fax and voice calls in-time between the PSTN and an IP network. The most important functions of a VoIP gateway include voice and fax compression/decompression, call routing and control signaling (Salvador Bracho del Pino, 2002). Some features also added interfaces to external controllers, such as Soft switches or Gatekeepers and billing systems.
Router: A router is a device in computer networking that forwards data packets to their destinations, based on their addresses. The work done by a router is called routing, which is somewhat like switching, but a router is different from a switch (Thomas Porter, 2006). The latter is simply a device to connect machines to form a LAN.
Firewall: A firewall is a small part of software which may is mixed with hardware in some situations that is created to protect from unauthorized access of a private network (James Edwards, Richard Barmante and Al Martin, 2006). A firewall normally blocks useless traffic data from inside to outside of the network and vice versa.
Advances are made every day, demanding almost constant change to keep pace with and surpass your competitors. One can however have an advantage getting the productivity and cost saving of VoIP today. For the best quality experience, VoIP uses highest quality equipment available (Tim Szigeti and Christina Hattingh, 2005). The requirements of VoIP may be of software or hardware. Some of the requirements that are generally preferred are Bandwidth, Quality and VoIP Adapter. In order to make VoIP as the best quality experience, high quality equipments should be provided. A computer with a broadband internet connection, PC speakers and a microphone are required and recommended (Essential Computing Advice, 2009). Hence, it can be stated that the customer can get benefited with the services offered by the VoIP only when the providers fulfill the requirements of VoIP.
Network design skills required for creating and deploying VoIP in an organization
The network design aspects should be done in a manner so that even the future technologies are integrated with ease. There are many issues while dealing with the transmission of voice. The major factor that contributes to the VOIP architecture in an organization is the network infrastructure. Delays are constantly present in the VOIP network architecture. It's one of the main criteria for VOIP network performance (John R. Abrahams and Mauro Lollo, 2003). The delay depends upon various factors like network set up, distance between the caller and receiver, total number of users accessing the network, type of network in use and finally the equipment that is deployed.
There are many call monitoring and management tools to be regarded for design system. They are both software and hardware based tools. Hardware-based tools are expensive and difficult to deploy and to get actual, leaving the stair to monitor the call of the software-packages. Mainly, a monitoring software of the call do these things, which are different to others: call recording, monitoring call conversations, VoIP call center, call recording backup, remote access, reporting with graphic displays of call activity and others deliver high quality services (Thomas E. Stern, George Ellinas, and Krishna Bala, 2008).From the above context it can be stated that all the software and hardware concepts are to be analyzed during the network design phase .There are many tools that support the networking process but the high standard ones as per the requirement has to chosen.
The hardware components should be given precedence as they are difficult to deploy, takes time, expensive and finally they get obsolete. The basic hardware components such as routers, gateways and other participating devices are also configured accordingly. The jittering is caused due to the time variation and improper routing techniques. Routers are also configured accordingly so as to minimize the jittering effect. Security factor should be one of the main features of the design aspect as it is one of the causes that degrade QoS of VOIP (Timothy V.Kelly, 2005). From the above context it can be stated that during the installation of hardware devices consideration for the transmission errors has to given for a better VOIP system.
Impacts of VOIP Deployment
Having different networks for getting data and voice would be costly, both at the beginning and while functioning. Other than cost-cutting and staff, running data and voice on the single network will provide a certain level of services of communication. This will lead to wave the way for emerging business applications like unified messaging, which combines data, video and voice (Frank Ohrtman, and Konrad Roeder, 2003 ). The network must be able to control both data and voice. For example, bandwidth is a parameter, which is crucial in getting that. Other important things which can be taken into account are flexibility, scalability and reliability of the network. VoIP comes with many choices, which are used previously as well as some new ones. Checking phone calls through computer while traveling, or having an email sent every time for a new voice mail message (Doug Lowe, 2008). The technologies that integrate computer and the service of the phones are exposed up to a whole new playing in the communication fields. From the above context it can be stated that VOIP provides features such as voice mail, checking the phone calls through computers and others that were not present in the recent technologies.
VoIP is the future technology for calling purpose. While the technology develops gradually many and many choices are available. Depending on the usage, savings are done. For user at home, who makes international calls and also for home based businesses, it is a high cost saving option (Clint Smith and John Meyer, 2005). From the above context it can be said that VOIP is the next generation technology for communication especially when it comes to the home users who make distant calls too often. It also supports the small business firms and for large ones integration is needed with the existing technology.
VOIP Proposed Architecture for the Clients
VoIP can be deployed in many different network segments. Now-a-days, it has been mostly deployed in the backbone and enterprise networks. Deploying VoIP as an end-to-end Next-Generation Network solution introduces additional constraints and issues. VoIP has become popular as it provides many advantages to the clients. VoIP is the cheaper way of communication over internet; many other components are developing day by day to increase effectiveness of VoIP architecture and the systems that are deploying VoIP (Syed A. Ahson and Mohammad Ilyas, 2008). VoIP architecture and systems limits to work not more than two systems, many of the business departments are striving hard to implement the VoIP architecture between different networks. VoIP architecture involves many components which help in the communication. Architecture should be proposed in such a way that it must be secured from hackers or unauthorized networks (Jonathan Davidson, James Peters, Monaj Bhatia, Satish Kalidindi and Sudipto Mukherjee, 2006). Corporate data and voice communications requires expensive exchange systems for the office and service from huge telephone companies. Today, organizations can use VoIP to supply internal communications, and go on to use a local telephone carrier for PSTN interface. In order to provide secured networks VoIP is adopting new architectures for voice communication. This proposed architecture comprises of:
- PBX Replacement.
- Media Servers.
The figure shows that the media server is connected in parallel fashion to the PBX via Voice over IP gateway, so that media server can communicate with PBX in proper channel. The data which are collected from the PBX via VoIP gateway is stored in the mail store. So Media Server is the main communication bridge in between gateway and data center and vice versa. The functions of the components are explained below:
PBX Replacement: Variety of platforms are available to interface a system onto a voice network, which includes the Intel architecture, accepting a PBX replacement to be build using available components (Jason Sinclair and Paul J. Fong, 2002). Linux creates a platform for such a hardware, being stable, as well as being able to provide the magnified network capabilities that a VoIP installation inquired, including QoS at the 802.11 VLAN (Virtual Local Area Network) and IP level support for segmentation of an Ethernet network.
Media Servers: In a Packet cable environment and other VoIP networks a media server processes and generates media streams. In internet and online communication, the media server processes all multimedia applications, such as call distribution, on-demand faxing, e-mail programs and others (Lorne Mason, Tadeusz Drwiega and James Yan, 2007). In VoIP specific applications, the media server handles all functions related to tasks such as decoding tones, bridging multiple streams, processing scripts, and recording audio.
Gatekeepers: The Gatekeeper provides communication for clients. These are clients that use Gatekeeper compliant applications. Net Meeting 3.0 or later is an example, such as application. The Gatekeeper receives client requests and then checks whether the requests are authorized or not. If they are authorized, the Gatekeeper routes the request to the proper address (James F. Ransome and John W. Rittinghouse, 2005).
Hence, from this context it can be understood that VoIP functions in a better way when compare to other technologies as the designers takes more steps while designing the VoIP architecture by including various technologies and techniques.
Quality of Service (QoS)
In spite of benefits like cheaper call rates, mobility and wireless features there is a need for the quality of service to be determined in VOIP. The traffic is one of the main areas that deserve utmost attention. The things to be considered in the VOIP transmission are end-to-end delay and packet loss. The end-to-end packet delays such as coding, packet and also network delay. The coding and packet delays can range up to 30ms (Lars Christian Wolf, David Hutchison and Ralf Steinmetz, 2001). The delay factors should be nonexistent or minimum as the people are habituated for the telephony systems which had least delays.
The following guidelines are recommended for providing a better QoS to their clients:
- Packet loss should be less than one percent.
- One-way latency must be inside 150ms.
- Jitter should be lesser than 30ms.
Assign an Inter active video to either a first priority queue or a second priority queue (during support) when making use of Cisco IOS LLQ, stipulation the minimum-priority bandwidth guarantee to the maximum of the video conferencing session will be more than 20 percent (Sudhir Dixit and Ramjee Prasad, 2003, p.194). From the above context it can be stated that the traffic control has a major influence on the quality of VOIP services. The delays should be least or should not exist, to increase the quality of VOIP. If latency, jitters are well within the restricted zone for effective communication.
Dealing latency independently, it had the honor of existence of VoIP's enemy, as also known as lag. Lag is the time difference between the packet of voice that is send from one point to another. This will have some time gap and an echo. It is because of links in the network is slow, which conducts to an echo. Latency is measured in milliseconds (ms) to thousands of seconds. A latency of 150ms, no more than that is notable so is acknowledged. More than that, quality begins to suffer. When it goes more than 300 ms, it will have the poor quality (International Engineering Consortium, 2007, p.61).The next big threat for the VOIP quality comes from the jitters.
Jitter is different in transiting of the packet delay which is caused by serialization, queuing and contention effects through the network. It is estimated as increase in the utilization of QoS controls such as bandwidth reservation and high speed links will control problems to some extent in the future, as jitter will stay as a problem for some time to come (Juanita Ellis, Charles Pursell and Joy Rahmanha, 2003, p.255) From the above context it can be stated that jitters occurs due to the packets have varying transmission times. These variations are caused due to the queuing times in the routers and different paths implemented during routing. The jitters will be existent to some extent as it seems to be difficult to completely eradicate the jitters in the VOIP services. VoIP applies equally to packet video and real time jitter traffic which are sensitive and other forms.
Impact of different carrier technologies on the effectiveness of a VoIP system
VOIP has been existent for years and has faced many challenges with the emerging and existing technologies. There are many carrier technologies that have an impact on VOIP either positively or negatively. The technologies considered are Wi-Fi and Wi-Max, as these technologies are emerging ones and the most effective ones in the future. Wi-Fi means wireless fidelity; it is technology with wireless which allows connection between two or more than that device wirelessly for data sharing purposes. Wi-Fi is a transportable connectivity technology for business, individual, for long-distance or for certain area. Many people in the world use Wi-Fi in their homes for conversation to anyone with Wi-Fi connected devices (David D. Coleman and David A. Westcott, 2009). The voice traffic is highly sensitive to latency and frame loss; users are immediately aware of the disturbances and are intolerable to small degradation in voice call quality. During the design aspect of the VoWi-Fi networks all the worst case scenarios are to be the initial points. The bandwidth of the spectrum is reduced while using the VoWi-Fi (Osborne, 2005). From the above context it can be stated that Wi-Fi is the next generation technology for VOIP, but there are more disadvantages than advantages. The disadvantages are so severe that users may not use Wi-Fi for VOIP as it reduces the quality of service for VOIP. During the design aspect of VOIP all the worst case scenarios like degradation in voice quality and others are to be considered.
The next technology for the VOIP systems is the Wi-Max technology. Wi-Max is, Worldwide operated reciprocally for Microwave Access, a technology standard that allows high speed internet of wireless. Wi-Max is an advanced version of Wi-Fi, a similar technology. Wi-Max need not be a direct line of sight to the receptor from the source. It has a high shared rate of data at 70Mbps, which is high to reach about a thousands of homes (Syed Ahson and Mohammad Ilyas, 2007).The disadvantages of the Wi-Max are; not everyone is allowed to set up a Wi-Max network, this will decrease the VOIP usability. The reach ability of Wi-Max is limited when compared to the Wi-Fi (World Bank, 2009, p.62). From the above context it can be stated that the Wi-Max is the advanced version of Wi-Fi. Wi-Max will reduce the usability of VOIP services as it is not possible for everyone to set up a Wi-Max network. It can be understood from the emerging technologies that they need a large phase development to support VOIP services. Especially if no considerable development takes place in Wi-Max technologies then VOIP may not be advised for this kind of network.
Planned Site Assessment
Assessing the Company network for VoIP readiness is a process and through this process, it will assist in identifying problem spots in the network prior to deployment.
In this process we will be interacting most of the time with Leeds Western Company technical staff. We will be requiring the followings from Leeds Western Company (Nortel, 2009):
- The key technical people from Company who will be involved in this VoIP Deployment from Company like their name, telephone contact number, and email id which will assist us to be in touch with the people and update on latest development regarding VoIP implementation.
- The address of point where we need to send the VoIP assessment kit.
- The computers which will be required as endpoints during the assessment in Company. These computers will be suing VoIP services.
We will be using hard phones as end point for VoIP assessment for Leeds Western Company.
- The physical and logical network diagrams [Existing LAN/WAN] that shows the network components over which the network components are run, as well as the communication and routing protocol in use which will assist us in for defining network speeds, modes, and protocol to be tested.
- Once we have an accurate picture of their current network topology Sometime may uncover areas that require improvement prior to VoIP implementation, such as re-routing multi-site paths to more efficient Configurations.
- Company technical team needs to update with the complete and current set of telephony currently being deployed in the company such as communication system, LAN/WAN equipment, ALN/telephony application (Nortel, 2009).
- Company technical team needs to provide other additional network information such as location of users, Links type, speeds, utilization, Routing protocol, Quality of service strategy etc.
The Company technical department need to verify network assessment kits to see whether they have appropriate tools once the network assessment kits are arrived, such as,
- PCs assessment
- Configuration verification
- Required Networks Assessment tools
- Network Bandwidth Calculator
- Network Assessment Tools
- Network Utilization tools
- Verification and Debugging tool
- Network Modelling Tools
- VoIP network management tools
Set up Assessment
- We will get the assessment kit from the main location.
- We will be meeting with the Leeds Western Technical Staff and participants to provide an overview of the activities explaining the types of tests to be run on the network, such as quality of service, VoIP, firewall and stress tests.
- We will also be setting up network assessment tools. We will deploy endpoint PCs and collect IP addresses of endpoints (Nortel, 2009).
We will be running some preliminary tests. We will be scheduling for an assessment after discussing with the Company in a planned way. We aim to get plenty of data, from different days of the week when network traffic conditions are different. However, for your first assessment, we will be running for a few hours and then scan the network results. If it appears that the assessment is providing meaningful results and including enough representative endpoints to cover the network, reset the schedule for a longer time period. This way we will be setting up the assessment.
We will be starting first with the basic Assessment (Nortel, 2009):
- We will fist going through VoIP traffic simulation for Company network to see whether the network can handle excessive traffic.
- We will be conducting metrics testing for packet loss, jitter and delay.
- We will also be conducting VoIP QoS verification which is a key aspect for the deployment.
In this case we will do various simultaneous calls between the locations and based on that we will make a report about how well the current network infrastructure is handling the calls.
VoIP Quality assessments will be run an approximation of the average call volume during work hours.
- After detailed study of the network through the assessment Vishnu VoIP Services will prepare a summary report with Pass/Fail status for VoIP deployment for the company.
- We will also be including recommendations if there are issues.
Finalize Assessment and make recommendations
By the conduct of the VoIP assessment we will be knowing the existing traffic demands on their data and voice networks which will assist us in determining the QoS requirements and potential increased (or decreased) bandwidth needs for Company's new IP Telephony network for the support of VoIP.
We will also be detecting and resolving underlying network issues such as bottlenecks in certain LAN segments or frequent retransmissions of data packets for clearing the path for the smoother implementation (Nortel, 2009).
Vishnu VoIP Services will provide two pre-configured report types to the Leeds Western Company:
Executive Summary Report-provides a summary, with relevant charts and graphs, of the results that most directly indicated VoIP Readiness or that affected the overall quality of VoIP calls on the network.
Complete Report-provides information, charts, and graphs about every type of data collected during the assessment. Complete Reports take varying amounts of time to generate, depending on the number of devices and WAN links you discovered and monitored and the number of call groups in the VoIP Quality assessment.
Conclusion and Recommendations
VoIP applications probably becoming more widely used as the requirements of customer are increased. Currently, the main problem for such applications is the lack of QoS guarantees. When QoS supporting protocols are used on a larger scale, this will certainly make VoIP more popular since people can then communicate with the quality that they desire. On LANs, where there is normally plenty of bandwidth, VoIP applications can already be used with little or no problems. However, on a larger scale, like the Internet, such QoS providing protocols will be necessary to make VoIP applications perform adequately. VoIP is a packet switched network introduced for voice communication over internet. VoIP is the most popular technology used by many organizations in order to complete their day-to-day business operations. VoIP was introduced in order to overcome the problems in traditional approach. The traditional approach used for voice communication is Public Switched Telephone network (PSTN). In this traditional approach circuit switched networks were used for communicating. In PSTN physical connections will be required for every call in order to provide communication between source and destination. Using physical connection for every call increases the infrastructure in the network, so cost of call will increase. This problem can be reduced by using VoIP technology. Hence, VoIP uses internet protocols instead of circuits to pursue voice communication and converts analog signals into digital signals and vice versa in order to communicate with destination.
There are many factors that contribute to the improvement of VOIP. Loss of service during outages is still a liability in VOIP service. Without the power supply VOIP phones are no use, so in that case, that is during power loss it can be a major problem. With the usage of VOIP emergency calls, it will be very hard to identify and send help in exact time. During calls, sometimes there will be silence for certain period when data is missing, while it is resolved. Traffic and Latency are the major regions in VOIP architecture (June Jamrich Parsons and Dan Oja, 2009). No standard protocol is applicable, so a protocol that performs to the requirement has to be developed or implemented. The VOIP complaints are fairly good if the callers are using a service which is free. As technology is getting upgraded, VOIP will match with the quality of traditional telephone technology. These are some of disadvantages and advantages of VOIP. Not only that Management should examine the network from time to time when organizing VoIP systems by enabling all the firewalls and test the security features of VoIP. Usage of soft phones should be reduced (Bourque, L. 2005) and proper network architecture should be designed in order to provide security. Mobiles with Wi-Fi should be used for VoIP instead of wired equivalent systems. Emergency services should be given special consideration for automatic location service. Hence, VoIP can be considered as the best technology compare to others.
- Anthony T. Velte (2004) Cisco: a beginner's guide, McGraw-Hill Professional Publishers, pp. 737.
- Clint Smith and John Meyer (2005) 3G wireless with WiMAX and Wi-Fi, McGraw-Hill Professional Publications, pp.234
- Collins (2005) Carriers Grade Voice Over IP, Tata McGraw-Hill Publishers, pp. 523.
- David D. Coleman and David A. Westcott (2009) CWNA: Certified Wireless Network Administrator Official Study Guide, John Wiley and Sons, pp.768.
- Doug Lowe (2008) Networking All-In-One Desk Reference, 3rd edition, Wiley-India Publications, pp.908
- Endler and Mark Collier (2007) hacking Exposed VoIP, Tata McGraw-Hill Publishers, pp. 539.
- Essential Computing Device (2009) "VoIP Requirements List", [Internet] available at URL: <http://www.rdweb.co.uk/voip_requirements_list/>, [accessed on 15th October 2009].
- International Engineering Consortium (2007) Beyond the Quadruple Play: Networking, Convergence, and Customer Delivery, Intl. Engineering Consortium Publications, pp.200.
- James Edwards, Richard Barmante and Al Martin (2006) Nortel Guide To Vpn Routing For Security and VoIP, Wiley-India Publishers, pp. 768.
- James F. Ransome and John W. Rittinghouse (2005) VoIP Security, Digital Press Publishers, pp. 402.
- Jason Sinclair and Paul J. Fong (2002) Configuring Cisco Voice over IP, Syngress Publishers, pp. 656.
- John R. Abrahams and Mauro Lollo (2003) Centrex or PBX: the impact of IP, Artech House Publications, pp.161.
- Jonathan Davidson, James Peters, Monaj Bhatia, Satish Kalidindi and Sudipto Mukherjee (2006) Voice over IP Fundamentals, Cisco Press Publishers, pp. 394.
- Juanita Ellis, Charles Pursell and Joy Rahman (2003) Voice, Video and Data Network Convergence, Academic Press Publishers, pp. 330.
- June Jamrich Parsons and Dan Oja, (2009) New Perspectives Computer Concepts 2010: Introductory, Cengage Learning,pp.522
- Lars Christian Wolf, David Hutchison and Ralf Steinmetz (2001) Quality of service-IW QoS 2001: 9th International Workshop, Springer Publications, pp.433.
- Lorne Mason, Tadeusz Drwiega and James Yan (2007) Managing Traffic Performance in Converged Networks, Springer Publishers, pp. 1191.
- Marion Tracey (2008) VoIP Voice over IP 100 Success Secrets, Lulu.com Publishers, pp. 140.
- Michael Bushong, Cathy Gadecki and Aviva Garrett (2008) JUNOS FOR Dummies, For Dummies Publishers, pp. 408.
- Osborne (2005) Certified Wireless Network Administrator official study guide, Mc-Graw Hill Publications, pp. 578.
- Pelin Aksoy and Laura DeNardis (2007) Information Technology in Theory, Cengage Learning Publishers, pp. 412.
- Salvador Bracho del Pino (2002) DCIS2002: Proceedings of the XVII Conference on Design of Circuits and Integrated Systems, Ed. Universidad de Cantabria Publishers, pp. 735.
- Sudhir Dixit and Ramjee Prasad (2003) Wireless IP and building the mobile Internet, Artech House Publications, pp.645.
- Syed A. Ahson and Mohammad Ilyas (2008) VoIP Handbook, CRC Press Publishers, pp. 454.
- Syed Ahson and Mohammad Ilyas (2007) WiMAX: applications, CRC Publications, pp.229.
- Thomas Porter (2006) Practical VoIP Security, Syngress Publishers, pp. 563.
- Tim Szigeti and Christina Hattingh (2005) End-to-End QOS Network Design, Cisco Press Publishers, pp. 734.
- Timothy V. Kelly (2005) VoIP for Dummies, For Dummies Publishers, pp. 272.
- World Bank (2009) Information and Communications for Development 2009: Extending Reach and Increasing Impact, World Bank Publications, pp.316.
- Yogesh K. Dwivedi, Anastasia Papazafeiropoulou and Jyoti Choudrie (2008) Handbook of Research on Global Diffusion of Broadband Data Transmission, Volume 2, Idea Group Publishers, pp. 852.