FINAL REPORT FOR
ICT 499 CAPSTONE PROJECT
- VoIP System via SKYPE Network
Student Name
: Teo Mao Sheng
Student PI Number
: K0605686
Abstract
As we are now in the information age, the high demand of communications around the world has been very common, especially in the telecommunication and internet communication region. This project is aim to develop a VoIP system which allows the users to communicate through the IP network at a minimum cost.
By using VoIP system, it eliminates the heavy costing fee for calling oversea as well as the subscription fee for retaining the telephone lines. As long as the broadband internet connection is available, users can communicate with any users around the world via IP-to-IP connection or IP-PSTN connection. On top of the VoIP system, with technologies such as Wi-Fi and Bluetooth, further enhancements are being done and allow greater mobility for the user while communicating with another user from the VoIP network.
The method employed in this project is to tap on Skype’s widely scale network as the backbone infrastructure of the VoIP system and run on Skype’s client
software on the user’s end. Skype’s softphone was installed on different platforms and various VoIP tests were conducted with significant results concluded.
Moving forward to a higher bandwidth connection, the prospect of VoIP system is very promising. The new technology opened up an extremely cost-effective business model with almost complete elimination of expensive infrastructure investments. The VoIP system can also be extended to the 3.5G and WIFI network which, inevitably allowing users to communicate around the globe without paying any fee.
Acknowledgment
I would like to thank the following people for making this project possible: Dr. Tan B K, for his patient guidance and efforts in shaping out the project, his constant encouragements really push me to the end of the project.
Matthias Tan, for his valuable assistance in planning this project. Lawrence Ong, for his guidance and valuable feedback of this project. Munir Hussein, for his support and valuable comments of this project. My family, for giving me moral supports as and when I needed.
List of Figures
Figures 1: Devices connected to VoIP system Figures 2: VoIP system
Figures 3: How Skype is connected Figures 4: PC connection to Skype Figures 5: Laptop connection to Skype Figures 6: Mobile phone connection to Skype Figures 7: PSP connection to Skype
Figures 8: DECT phone connection to Skype Figures 9: Various platforms connected to Skype
List of Tables
Table 1: Comparison table for different connected devices Table 2: Comparison table for oversea connection
Table of Contents Abstract...2 Acknowledgements ...3 List of Figures ...4 List of Tables...4 Table of Contents ...5
Chapter 1 : Introduction and Aims...6
1.1 Introduction ...6
1.2 Aims:...7
Chapter 2 : VoIP System ...8
2.1 What is VoIP...8
2.2 How does VoIP works... 10
2.3 Benefits of VoIP ... 11
2.4 Challenges of VoIP... 12
Chapter 3 : Skype... 14
3.1 What is Skype ... 14
3.2 What can Skype do ... 16
3.3 Why Use Skype ... 19
Chapter 4 : Methodology ... 20
4.1 Research Purpose... 20
4.2 Research Approach ... 21
4.2.1 PC connection to Skype... 21
4.2.2 Laptop connection to Skype ... 21
4.2.3 Mobile Phone connection to Skype ... 22
4.2.4 Gaming Console connection to Skype... 22
4.2.5 DECT phone connection to Skype ... 23
4.3 Research Strategy ... 24
Chapter 5: Conclusion, Recommendations and Reflections... 26
5.1 Conclusion ... 26
5.2 Recommendations ... 27
5.3 Reflections ... 28
Reference ... 29
Appendix A: How to configure Skype on PC ... 30
Appendix B: How to configure Skype on PSP ... 39 Glossary...Error! Bookmark not defined.49
Chapter 1: Introductions and Aims 1.1: Introductions
In the 1990s, the Internet was generally limited to use in academic environments, both in educational and corporate institutions. Due to the exponential growth of the internet and high data transmission demand around the globe, a fast
increasing number of businesses and individuals are using the internet for voice communication. This technique is called Voice over Internet Protocol (VoIP). Traditionally, the telephone systems convert sound waves from the microphone into electrical signals and reverts the electrical signals back into sound waves via the speaker at the other end. This technique has been used for the past century until the deployment of the first systems that could transmit multiple phone calls into one by converting every call into a stream of data digitally. VoIP systems continue this evolution by taking those digital data streams compressing them, breaking them into packets, and sending those packets over the Internet. At the receiving end, the process is reversed to construct back the original message. As such, with a VoIP system people can communicate with one other through
speakers and microphones connected directly to their computers.
Generally, a VoIP adapter is used to convert electrical signals to Internet packets. VoIP gateways can interconnect the Internet-based systems with the world-wide Public Switch Telephone Network (PSTN), creating a communication between a computer and a telephone.. In this project, we only work on purely VoIP network and no switching of gateways are involved due to the fact that typically there is a fee for using such gateways.
Skype is a proprietary VoIP system developed by Skype Technologies S.A., based on peer-to-peer technology. Instead of transmitting all voice calls through a central server like most of the VoIP system available now in the market, Skype uses client-based software to seek out and find other Skype clients, then build from these connections a network that can be used to search for other users and send them messages. Skype system earns revenue by charging for the use of the gateway that interconnects the Skype network with the PSTN. Hence in this project, no fee is incurred for using the Skype network. Skype’s VoIP system, in simple terms, is the process of breaking up audio or video into small chunks of data, transmitting those data over Skype’s network, and reassembling those chunks of data back at the other end so that two people can communicate using audio and video.
1.2: Aims
The main objective of this project is to develop a VoIP system which allows the users to communicate through the IP network at a minimum cost. This project focus is on implementing the VoIP system using the Skype’s network as the infrastructure and Skype’s client software on the user’s end platforms.
The following diagram illustrates how the various communication platforms link up via the Skype’s network:
Notebook
Workstation
Gaming Console
Mobile Phone DECT Phone (with Skype built-in) VoIP system through
Skype’s Network Internet Connection Internet Connection WiFi 3.5G network WiFi
Figure 1: Devices connected to VoIP system
The main aim of the project is to make sure all testing platforms can be link up via the Skype’s network. This allows us to use the Skype’s network and make voice communication to all different platforms without any charges.
Chapter 2: VoIP System 2.1: What is VoIP?
VoIP (Voice over Internet Protocol) is technologies designed to deliver voice information using the IP (Internet Protocol) which enables voice calls to be carried over the Internet as opposed to the traditional copper telephone lines system via the PSTN (Public Switched Telephone Network). The potential for VoIP is very promising as it represents a major change in the telecommunication regions.
By digitized voices into packets over the internet, it has high potential to converge with other digital technologies, which in turn will result in many new services as well as applications become available in the future. In the long-term, VoIP is likely to impact on many developments such as virtual universities, mobile offices, and integration with enterprise-level services and applications. One of the main drivers in developing VoIP was the potential to cut the cost of telephone calls. Traditional voice calls, running over the PSTN, are made using circuit switching, where a dedicated circuit or channel is set up between two points before the users talk to one another.
The advantage of this is that once the circuit is set up, the call quality is very good, because it is running over a dedicated line. But this type of switching is expensive because the network needs a great deal of capacity. VoIP uses IP protocols, originally designed for the Internet, to break voice calls up into digital packets and in order for a call to take place the separate packets travel over an IP network and are reassembled at the far end.
The breakthrough was in being able to transmit voice calls, which are much more sensitive to any time delays or problems on the network, in the same way as data. Whereas calls over the PSTN are metered, so the user pays for the amount of time taken by their call, Internet usage is not metered. The user pays a set fee for their Internet service and their VoIP service and can then use the Internet to get free phone calls to other users on the same VoIP service, or pay a small fee to call users on other VoIP services or on the PSTN.
Packetized voice also enables much more efficient use of the network because bandwidth is only used when something is actually being transmitted. Also, the network can handle connections from many applications and many users at the same time, unlike the dedicated circuit-switch approach.
One of the most important things to point out is that VoIP is not limited to voice communication. In fact, a number of efforts have been made to change this popular marketing term to better reflect the fact that VoIP means voice, video, and data conferencing. All such attempts have failed up to this point, but do understand that video telephony and real-time text communication, for example, is definitely within the scope of the VoIP.
VoIP is important because, for the first time in more than 100 years, there is an opportunity to bring about significant change in the way that people communicate. In addition to being able to use the telephones we have today to communicate in real-time, we also have the possibility of using pure IP-based phones, including desktop and wireless phones. We also have the ability to use videophones, much like those seen in science fiction movies. Rather than calling home to talk to the family, a person can call home to see the family.
One of the more interesting aspects of VoIP is that we also have the ability to integrate a stand-alone telephone or videophone with the personal computer. One can use a computer entirely for voice and video communications (softphones), use a telephone for voice and the computer for video, or can simply use the computer in conjunction with a separate voice/video phone to provide data conferencing functions, like application sharing, electronic whiteboarding, and text chat.
VoIP allows something else: the ability to use a single high-speed Internet connection for all voice, video, and data communications. This idea is commonly referred to as convergence and is one of the primary drivers for corporate interest in the technology. The benefit of convergence should be fairly obvious: by using a single data network for all communications, it is possible to reduce the overall maintenance and deployment costs. The benefit for both home and corporate customers is that they now have the opportunity to choose from a much larger selection of service providers to provide voice and video communication services. Since the VoIP service provider can be located virtually anywhere in the world, a person with Internet access is no longer geographically restricted in their selection of service providers and is certainly not bound to their Internet access provider.
In short, VoIP enables people to communicate in more ways and with more choices.
2.2: How does VoIP work?
VoIP works by converting audio signals into digital signals using ADC (analogue to digital converter). This digital signal will then go through speech compression. In places like LAN, there might be sufficient bandwidth, so under such
circumstances the compression process is skipped. By current standards, the compression ratio for internet phone is on the order of 16 to 1.
RTP (real time protocol) is used for time stamping and content identification of UDP packets after voice packets have been converted into data packets. After which, the signaling system will attempt to find out the destination IP address and establish a connection.
After this connection has established, the transmission can occur. However, things get a little bit more complicated when it’s doing Internet-to-PSTN. At the receiving end, the packets get reassembled and the digital audio data is
converted back into analog signals.
Figure 2: VoIP system (diagram extracted from http://www.demon.net/vob/how-voip-works/index.html )
2.3: Benefits of VoIP Operational Costs
VoIP can reduce the cost of communication and infrastructure. Phone calls can be routed using existing data networks, as opposed to needing a
separate voice network. Features that telecommunication companies usually charge for an extra fee, such as call forwarding, call waiting, conference calling etc… are available for free.
Flexibility
VoIP, being run in a software environment, allows the implementations of additional value-added service easily as compared to PSTN. This is also possible as VoIP can support multiple phone calls over the same broadband connection. So, adding a new phone line does not require additional rewiring to the home or office. Calls can also be made secure using existing protocols. VoIP is also location independent, as one only requires a fast and stable internet connection.
2.4: Challenges of VoIP Quality of Service
Due to the underlying unstable IP network, as opposed to the traditional circuit-switch phone networks, VoIP suffers from the effects of data packets not arriving in sequential order, or provide QoS guarantees. This results in problems such as latency and jitter.
Delays
Several types of delays could happen in the VoIP system, namely,
propagation delay, network delay, accumulation delay, and processing delay. Propagation delay occurs as the signal requires traveling a distance. Network delays occur due to the capacity of the network and the processing of the packets as they travel through the network. Accumulation delay occurs as some amount of time is required to collect a frame before processing can continue. Processing delay occurs as some time is required to encode and decode the samples into and from packets.
Latency
Latency occurs when the voice data is queued at the router or other network element, causing delayed from reaching its destination. It also causes
problems such as echo and talker overlap. Generally, the end to end latency is accepted within the 150ms range for good quality phone calls. To ensure the latency remains below 150ms range, the primary causes of latency need to be considered.
Packet Loss
Packet loss occurs when packets are lost during transmission or simply arrive too late to be used. Transmission of data (such as a webpage) makes use of the TCP/IP protocol suite which allows for retransmission of missing packets, but VoIP, which uses UDP, does not allow retransmission and the missing packets are simply left out of the call. Such loss causes voice clipping and skips .This is less of a problem than latency or jitter, since the codec used in voice processing can cope with a certain amount: up to 1% is usually
undetectable, more than 3% is the maximum permitted within industry standards
Call Dropping/Blocking
Call dropping refers to the unexpected termination of VoIP connection. It could be due to an equipment failure at either end or at the midpoint element, or because of excessive network congestion and the subsequent dropping of large number of packets.
Evolving Standards and Interoperability
Standards for VoIP and its support are still evolving, hence the device interoperability standards are still developing.
Chapter 3: Skype 3.1: What is Skype?
Skype is a software application that enables users to make telephone calls over the internet. Skype supports skype calls as well as
skype-to-landlines/mobile phone calls. Calls made to other skype clients as well as free-of-charge numbers are free, while calls made to landlines and mobile phone can be made for a certain sum of payment.
Skype was created by Ahti Heinla, Priit Kasesalu and Jaan Tallinn, who were the original developers of Kazaa, a peer-to-peer file sharing software application. Skype was initially called “Sky peer-to peer”, which is then shortened to Skyper. However, the domain name for Skyper was already taken, and so they decided to drop the “r” at the end, which became Skype.
Since the launch of its services, Skype has experienced a rather rapid growth. Ebay acquired Skype in September 2005 for $2.6 billion. Ebay has also
announced a public stock offering for 2010 to spin Skype off as a separate company.
Figures 3: How Skype is connected (diagram extracted from
3.2: What Can Skype Do?
Besides the ability of making VoIP calls, Skype can also make video calls and send instant messages over the internet.
SkypeOut
SkypeOut is a service which allows users to make Skype-to-phone calls. This includes landline numbers as well as mobile phone numbers. This service used to be free when making calls within Canada and the United States, however, as at January 30th, 2007, the service is no longer free.
The SkypeOut service is free when making calls to toll free numbers in certain countries, such as France, Poland, United Kingdom, the United States, and Canada. This is so even when they do not have the service. However, the service is not supported in many other countries. There is also no support for calling emergency numbers.
The quality of service has been said to be rather bad, and users often experienced disconnections and distortions.
SkypeIn
SkypeIn is a service which allows users to get phone-to-Skype calls. This allows landline phones and mobile phones to make calls to a local Skype phone number, and receive calls from the computer. This service allows users to subscribe to numbers in selected countries.
Skype Voicemail
Skype Voicemail is a service that allows callers to leave voice-mail messages to Skype users. This is a paid service though the company Kishkish provides the service for free.
The service has been relatively unstable, and many problems were encountered by users, such as not receiving the voice mails.
Skype chat
Skype allows its users to have group chats, similar to IRC. Users could chat in groups of up to 150 users.
Skype Me
Skype allows people from around the world to make voice chat with each other. By setting the user status to ‘Skype Me’, the user indicates his
availability for voice chat to anyone from around the world. This feature can be used to make new friends and some users use it to learn foreign
languages. Note that enabling this service also opens up the possibility of getting contacted by spammers and scammers.
Skype video calling
Skype allows its users to make video calls to another Skype user. Currently, only one-to-one video calls can be made, though multiple voice chats can still be established. This feature is available in multiple platforms, making Skype one of the few cross-platform video conferencing solutions available.
In Skype 3.6, high definition video conferencing is supported, allowing users to have video conferencing in high definition.
Skypecasts
Skypecast is a feature that allows live, moderated conferencing of up to 100 users. Users could listen in to the host, and the host is able to mute or pass the microphone to other users. This feature has been discontinued.
Skype SMS
Skype SMS is a feature that allows its users to send SMS messages out to mobile phones. Depending on the region, the recipient may either see a generic number, or the first 11 Skype user number, or a mobile phone
number. If it is from a mobile number, the recipient is able to reply to the SMS messages as per normal, and if it is not, the recipient won’t be able to reply to the messages. The cost of the SMS is cheaper than standard rates.
Skype web toolbar
The Skype Web Toolbar is a plug-in for Internet Explorer and Mozilla Firefox. It detects phone numbers on internet web pages, and turns them into
clickable links. The link can be clicked which will prompt the user if he wants to call the number using Skype. Right clicking on the number gives other options, such as adding that number to your Skype contact list.
Skype history logs
Skype keeps a log file to store history messages between a contact pair for every contact. These are stored in the local drive, so the history is only available on that computer, and does not transfer to other computers with Skype that one has signed on to. History logs need to be manually enabled in the configuration.
SkypeFind
SkypeFind is a community-based directory listing. Skype Prime
Skype Prime is a feature that let the user call numbers that charge by the minute. This feature is not available in Linux.
Invisible Calling
This allows Skype to connect with other users without having to be in a conference. The user will be able to talk to multiple users without those users being able to communicate with each other.
Skype Extras
Skype provides additional tools to extend its capabilities. Third party plugins can be obtained from https://extras.skype.com. Some of these add-ons include a voice recorder, games, and also a plugin that enables sending of faxes.
PocketSkype
PocketSkype is the mobile version of Skype for the handheld devices such as the PDA. Users can connect to Wi-Fi networks and enjoy making free,
unlimited calls using their PDA. Portable Skype
This is a version of Skype that could be run directly from a USB memory stick, without the need to have it being installed into the computer.
3.3: Why Use Skype?
Skype is widely popular. Within the first week of, more than 60,000 people
downloaded the Skype client. Skype is available for Windows, MacOS, PocketPC and Linux, Currently Skype has more than five million users.
Both the Skype software and use of the Skype network is free; there is a nominal charge for calls made using the “Skype Out” and "SkypeIn" features that connect Skype to the PSTN network.
Skype is much easier to use than other VoIP systems. The Skype client is easily installed. Other than choosing a username, no configuration is required. And unlike the SIP system used by Vonage, Skype clients readily work behind firewalls and Network Address Translation (NAT) systems.
Skype has an astonishingly good voice compressor, giving it fidelity that in many cases surpasses traditional telephone systems when Skype is used with a high bandwidth connection.
In additional to voice telephony, Skype supports instant messaging, search, and file transfer.
Skype is encrypted. Unlike traditional telephony and other VoIP-based systems, Skype claims to encrypt all communications with 128-bit or better cryptography ciphers, allegedly making it impossible for someone who passively intercepts a Skype conversation from deciphering or listening to its contents.
4. Methodology
4.1: Research Purpose
The purpose of the research is to have digital communications from two parties using VoIP technology. By using Skype and the various Skype supported platforms, the research is to find out whether the interoperability between different devices is operational and the cost of the communications. These findings will help in further development of business model by using VoIP technologies.
4.2: Research Approach
In this project, internet connections are established between different devices. Skype software is installed in all the devices. The following diagrams illustrate how the devices are connected through the Skype network.
4.2.1: PC connection to Skype
Figures 4: PC connection to Skype
In the PC, Skype client software is installed. After registering a unique user ID and password with Skype, the user can straight away connect to the Skype’s network as long as the internet connection is established. Once connected, the user needs to add or accept invitation from other users through the contact list. Once the contact has been added, both parties can start to communicate with one another by using instant messages or voice.
4.2.2: Laptop connection to Skype
Figures 5: Laptop connection to Skype
In the laptop, setup is the same as the PC’s environment. The only different is that the internet connection is using wireless network or 3.5G network instead of the wired local area network. As the connections are based on wireless
4.2.3: Mobile Phone connection to Skype
Figures 6: Mobile phone connection to Skype
For the mobile phone, only those which supported the Skype Mobile software can be installed and connected to the Skype network. Currently, mobile phones which run on the Windows Mobile Operating System are able to install the Skype software. The
connection from the mobile phone to the internet can be choose from WiFi, GPRS, EDGE and those are available from the mobile operators company. The marketing strategy from some of the ISP will offer free internet access to their mobile customers, hence, it is possible to connect to the Skype network without paying anything.
4.2.4: Gaming Console connection to Skype
Figures 7: PSP connection to Skype
The gaming console, PlayStation Portable, with its latest system firmware upgraded is able to connect to the Skype’s network via the wireless internet connection. This allows the PSP become a communication device, making it a truly multimedia and more sellable console.
4.2.5: DECT phone connection to Skype
Figures 8: DECT phone connection to Skype
DECT phone which already pre-installed Skype client software is able to connect to the Skype’s network as long as the DECT phone is connected to the internet via the cable modem or the ADSL modem. Once plug into the modem, the phone will become a dual connectivity device, it is a Skype phone as well as a normal telephone.
4.3: Research Strategy
Figures 9: Various platforms connected to Skype
Once the devices are connected to the internet and joined the Skype’s network, voice transmission test are carried locally and the below table shown are the gathered data.
Table 1: Comparison table for different connected devices
Connection made between: PC Laptop DECT Phone Mobile Phone PSP PC Excellent Voice Quality Good Voice Quality Excellent Voice Quality Good Voice Quality Good Voice Quality Laptop Good Voice Quality Good Voice Quality Good Voice Quality Poor voice Quality Poor voice Quality DECT Phone Excellent Voice Quality Good Voice Quality Excellent Voice Quality Good Voice Quality Good Voice Quality Mobile Phone Good Voice Quality Poor voice Quality Good Voice Quality Poor voice Quality Poor voice Quality PSP Good Voice Quality Poor voice Quality Good Voice Quality Poor voice Quality Poor voice Quality
The internet connections are based on the following standards for different platforms:
PC connections – 12Mbps via cable modem
Laptop connections – 2 Mbps via cable modem and wireless router DECT phone connections – 12Mbps via cable modem
Mobile phone – 2 Mbps via cable modem and wireless router PSP - 2 Mbps via cable modem and wireless router
There are no other internet activities going on while doing the test mentioned. In addition, another set of test is carried out to reinforce the idea that VoIP system can also work perfectly if one of the communicated party is in oversea. The setup is as such that one of the users is located at Cambridge, United Kingdom and he is connected to the Skype’s network from the laptop and wireless network connection. On the other hand, in Singapore, the other user tries to connect to Skype’s network with the testing devices. The following table is the gathered data from the test:
Connected to UK with Laptop in UK
PC Excellent Voice Quality
DECT Phone Excellent Voice Quality
Mobile Phone Poor voice Quality
Chapter 5: Conclusion, Recommendations and Reflections 5.1: Conclusion
With the successful connections between various platforms of the Skype’s software and communicate via the VoIP technology, it can be deducted that the VoIP system can be implemented with the Skype’s network for everyone.
This would help to achieve the main objective of the project that is to minimize the cost of communication between two parties, especially if it is oversea communication. As a result, the resources saved could be budgeted to other area if this solution is catering for corporate organizations.
The project has proved its potential value as it is software base, it can run on many different platforms and the costing for running the program is only the internet connection charges. As long as the internet connection is available, voice communications between users can communicate with any users around the world via IP-to-IP connection or IP-PSTN connection. It eliminates the heavy costing fee for calling oversea as well as the subscription fee for retaining the telephone lines.
The main challenge concluded from this project is that VoIP via wireless connections is still badly affected due to noise interferences. Not only the packets are dropped tremendously on several tests, the cancellation of echo effects are also badly affected, thus created a lot of echo while transmitting the voices across the network.
5.2: Recommendations
As the digital communication technologies advances rapidly around the world, VoIP system is highly recommended to replace the existing PSTN system. Cost saving remains the main selling point for using VoIP system. Secondly, the
trends of moving towards unified communications are growing in the recent years. By integrating digital communication devices such as VoIP, facsimile, workstation, mobile phone into one unified server, it allows better administrative control as well as reducing the operational cost for the company.
Due to the usage of Skype’s software and network in this project, the entire setup is rather straight forward and easy to implement. If the VoIP system is to be review or further investigate in the future, my recommendation is to choose a widely adopted VoIP software in the market as there are many different codecs and standards are still developing for the VoIP system. With that, testing of the system and finding the appropriate drivers will be much easier.
5.3: Reflections
Initially, I am using simulated Cisco’s software to run as the VoIP infrastructure. Due to its complication and lack of technical background of Cisco’s products, I got to immediately make my decision and adopted the Skype’s technology instead. From this, I have learnt that project execution plan might not always be following the project plan and contingency planning is always necessary. One must always be prepared to think out of the box and still maintaining the overall project objective.
Secondly, as the project is an individual effort and also without any funding involved, I have learnt how to interact and deal with different kind of people, negotiating skills of loaning test equipments, as well as getting valuable technical feedback from them. These skills are not taught in the school context and it really brings me to another level of managing a project.
With the understanding of technical information taught from the school and the experiences gained from doing this project, I felt that this entire project has covered its purpose and allowing me to have a greater level of confident to handle other projects in the future.
6. References
1. Wikipedia on VoIP, http://en.wikipedia.org/wiki/VoIP (website); March 2009
2. How VoIP works, http://communication.howstuffworks.com/ip-telephony.htm (website); March 2009
3. Why switch to VoIP, http://www.voipadvantage.co.uk/ (website); March 2009
4. Skype, http://www.skype.com (website); March 2009
5. The cost factor, http://www.ezilon.com/information/article_15560.shtml (website); March 2009
6. Advantages and disadvantages of Voip, http://ezinearticles.com/?VOIP-Advantages-and-Disadvantges&id=77875 (website); March 2009 7. How To Build A Voip
network,http://www.voipuser.org/forum_topic_8289.html (website); March 2009
8. Introduction to VoIP technology,
http://www.pcmech.com/article/introduction-to-voip-technology/ (website); march 2009
9. Qos VoIP network diagram, http://www.voip-revolution-info-site.com/QoS-VOIP-network-diagram.htm (website); march 2009
10. How to Skype your PSP,
http://www.gamespot.com/features/6185924/index.html (website): march 2009
Glossary
ADSL – Asymmetric Digital Subscribers Line
DECT – Digital Enhanced Cordless Telecommunication IP – Internet Protocol
ISP – Internet Service Provider Mbps – Mega bits per second PC – Personal Computer PSP – PlayStation Portable
PSTN – Public Switched Telephone Network RTP – Real Time Protocol
SMS – Short Message Service
TCP – Transmission Control Protocol QoS – Quality of Service
UDP – User Datagram Protocol VoIP – Voice over Internet Protocol WiFi - Wireless Fidelity
