VoIP (Voice over Internet Protocol)

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VoIP Telephony

Voice over Internet Protocol is a category of hardware and software that enables people to use the Internet as the transmission medium for telephone calls by sending voice data in packets using IP rather than by traditional circuit transmissions of the PSTN (Public Switched Telephone Network).

VoIP converts Analog voice signals into digital data packets and supports real-time, two-way transmission of conversations using Internet Protocol (IP). VoIP calls can be made on the Internet using a VoIP service provider and standard computer audio systems. VoIP offers a substantial cost savings over traditional long distance telephone calls.

Understanding the terms are a first step toward learning the potential of this technology:

• IP Telephony encompasses the full suite of VoIP enabled services including the interconnection of phones for communications; related services such as billing and dialing plans; and basic features such as conferencing, transfer, forward, and hold. These services might previously have been provided by a PBX.
• IP Communications includes business applications that enhance communications to enable features such as unified messaging, integrated contact centers, and rich-media conferencing with voice, data, and video.
• Unified Communications takes IP communications a step further by using such technologies as Session Initiation Protocol (SIP) and presence along with mobility solutions to unify and simply all forms of communications, independent of location, time, or device. (Learn more about unified communications.)

The steps and principles involved in originating VoIP telephone calls are similar to traditional digital telephony and involve signaling, channel setup, digitization of the analog voice signals, and encoding. Instead of being transmitted over a circuit-switched network, however, the digital information is packetized, and transmission occurs as IP packets over a packet-switched network. Such transmission entails careful considerations about resource management different from time-division multiplexing (TDM) networks.

One of the most significant advantages of VoIP (over a traditional public switched telephone network (PSTN - also known as a legacy networks) is that one can make a long distance phone call and bypass the toll charge. Furthermore, when compared with circuit-switched services (yet another name for legacy networks), IP networks can carry 5 to 10 times the number of voice calls over the same bandwidth.

The interesting thing about VoIP is that there is not just one way to place a call. There are three different "flavors" of VoIP service in common use today:

• ATA: The simplest and most common way is through the use of a device called an ATA (analog telephone adaptor). The ATA allows you to connect a standard phone to your computer or your Internet connection for use with VoIP. The ATA is an analog-to-digital converter. It takes the analog signal from your traditional phone and converts it into digital data for transmission over the Internet. Providers like Vonage and AT&T CallVantage are bundling ATAs free with their service. You simply crack the ATA out of the box, plug the cable from your phone that would normally go in the wall socket into the ATA, and you're ready to make VoIP calls. Some ATAs may ship with additional software that is loaded onto the host computer to configure it; but in any case, it's a very straightforward setup.
• IP Phones: These specialized phones look just like normal phones with a handset, cradle and buttons. But instead of having the standard RJ-11 phone connectors, IP phones have an RJ-45 Ethernet connector. IP phones connect directly to your router and have all the hardware and software necessary right onboard to handle the IP call. Wi-Fi phones allow subscribing callers to make VoIP calls from any Wi-Fi hot spot.
• Computer-to-Computer: This is certainly the easiest way to use VoIP. You don't even have to pay for long-distance calls. There are several companies offering free or very low-cost software that you can use for this type of VoIP. All you need is the software, a microphone, speakers, a sound card and an Internet connection, preferably a fast one like you would get through a cable or DSL modem. Except for your normal monthly ISP fee, there is usually no charge for computer-to-computer calls, no matter the distance.

VoIP is available on many smartphones, personal computers, and on Internet access devices. Calls and SMS text messages may be sent over 3G or Wi-Fi.

Historical Milestones

1973: Network Voice Protocol (NVP) developed by Danny Cohen and others to carry real time voice over Arpanet.

1973, First Voice Data Packet Transmitted

1974: The Institute of Electrical and Electronic Engineers (IEEE) published a paper titled "A Protocol for Packet Network Interconnection".

1975: CompuServe is born.

1975, CompuServe Born

1974: Network Voice Protocol (NVP) first tested over Arpanet in August 1974, carrying 16k CVSD encoded voice – first implementation of Voice over IP

1977: Danny Cohen, Vint Cerf, Jon Postel agree to separate IP from TCP, and create UDP for carrying real time traffic

1981: IPv4 is described in RFC 791.

1985: The National Science Foundation commissions the creation of NSFNET.

1986: Proposals from various standards organizations for Voice over ATM, in addition to commercial packet voice products from companies such as StrataCom

1991: First Voice Over IP application, Speak Freely, released as public domain. Originally written by John Walker and further developed by Brian C. Wiles.

1992: Voice over Frame Relay standards development within Frame Relay Forum

1993: First Video Telepresence System.

1993, Video Conference System by AT&T

1994: MTALK, a freeware VoIP application for Linux

1995: VocalTec releases the first commercial Internet phone software.

• Beginning in 1995, Intel, Microsoft and Radvision initiated standardization activities for VoIP communications system.

1996:

• ITU-T begins development of standards for the transmission and signaling of voice communications over Internet Protocol networks with the H.323 standard.
• US telecommunication companies petition the US Congress to ban Internet phone technology.

1997: Level 3 began development of its first softswitch, a term they coined in 1998.

1999:

• The Session Initiation Protocol (SIP) specification RFC 2543 is released.
• Mark Spencer of Digium develops the first open source private branch exchange (PBX) software (Asterisk).

2004: Commercial VoIP service providers proliferate.

2007: VOIP device manufacturers and sellers boom in Asia, specifically in the Philippines where many families of overseas workers reside.

History

There are two fundamental technologies that are necessary for the existence of VoIP. The first, and most widely used, is the telephone. The second technology is the Internet. The telephone was as direct result of the (independent) work of Alexander Gram Bell and Elisha Gray in the 1870s. Early telephones were leased in pairs to subscribers. The subscriber was required to put up their own line to connect with another.

Alexander Gram Bell and Elisha Gray in the 1870s

In 1889, Almon B. Strowger, a Kansas City undertaker, invented a switch that could connect one line to any of 100 lines by using relays and sliders. This switch became known as "The Strowger Switch" and was still in use in some telephone offices well over 100 years later.4 To make a call, the user needed to push a button on their phone the required number of times to dial the receivers phone number. This button was replaced in 1896. Interestingly, Philadelphia was the last city to give up the dual service (rotary and button) in 1943. About the same time the transistor was invented, mathematician Dr. Claude Shannon published "A Mathematical Theory of Communication," which promoted the concept of communicating in binary code. Dr. Shannon's paper formed the basis of the entire digital communications revolution, from cell phones to the Internet.

In 1968 the Internet was first developed by ARPANET (Advanced Research Projects Agency Network), founded by the U.S. Department of Defence in 1957. ARPANET was developed to provide a decentralized communications network that would not be disrupted by a potential global war. As the PC became popular, online service companies formed to provide proprietary information and email services. Subscribers would dial into the network with their telephone lines would pay an hourly fee to receive the services offered.

Although the telephone and Internet were vital to the existence of VoIP, there is another technology that is closely related, and just as important. In 1972 Dr. Vint Cerf was the man who invented Transmission Control Protocol / Internet Protocol (TCP/IP) – the technical protocol that defines the form of net data packets and how they travel to their destinations. VoIP started in February of 1995 by a small company in Israel called Vocaltec, Inc. Their product, Internet Phone, allowed one user to call another user via their computers, a microphone and a set of speakers. Additionally, this application/product only worked if both the caller and the receiver had the same software setup. By 1998 some entrepreneurs started to market PC-to-phone and phone-to-phone VoIP solutions.

Protocols

Voice over IP has been implemented in various ways using both proprietary protocols and protocols based on open standards. Examples of the VoIP protocols are:

• H.323
• Media Gateway Control Protocol (MGCP)
• Session Initiation Protocol (SIP)
• H.248 (also known as Media Gateway Control (Megaco))
• Real-time Transport Protocol (RTP)
• Real-time Transport Control Protocol (RTCP)
• Secure Real-time Transport Protocol (SRTP)
• Session Description Protocol (SDP)
• Inter-Asterisk eXchange (IAX)
• Jingle XMPP VoIP extensions
• Skype protocol
• Teamspeak

The H.323 protocol was one of the first VoIP protocols that found widespread implementation for long-distance traffic, as well as local area network services. However, since the development of newer, less complex protocols such as MGCP and SIP, H.323 deployments are increasingly limited to carrying existing long-haul network traffic. In particular, the Session Initiation Protocol (SIP) has gained widespread VoIP market penetration.

These protocols can be used by special-purpose software, such as Jitsi, or integrated into a web page (web-based VoIP), like Google Talk.

Working

To transport voice over a data network, the human voice must be “packetized.” This process contrasts significantly with the circuit-switching mechanism used in traditional networks. Voice packetization involves appending headers with routing information to the voice data. Multiple voice samples are combined into a packet and the voice packet is switched hop-by-hop through the network. To summarize, the voice signal is broken up into small pieces (packets) and sent though the network one-by-one. The process of packetization compresses the caller’s voice signal, transfers it over the IP network and it is then decompressed at the other end.

Working of VoIP

Operational Cost

VoIP can be a benefit for reducing communication and infrastructure costs. Examples include:

• Routing phone calls over existing data networks to avoid the need for separate voice and data networks.
• The ability to transmit more than one telephone call over a single broadband connection.
• Secure calls using standardized protocols (such as Secure Real-time Transport Protocol). Most of the difficulties of creating a secure telephone connection over traditional phone lines, such as digitizing and digital transmission, are already in place with VoIP. It is only necessary to encrypt and authenticate the existing data stream.
• Utilized existing network infrastructure to minimize the operating cost.
• Eliminating the need of hiring personnel to greet and distribute incoming calls with the use of a Virtual PBX

Benefits

When many people first learn about VoIP, they commonly say, “So, we are sending voice over data cables instead of voice cables...what is so big about that?” It seems like the biggest benefit is saving cabling costs, nothing more. After you dig deeper into the ramifications of running voice over data networks, you begin to uncover many business benefits that were previously untapped. The business benefits of VoIP include the following:

• Reduced Cost of Communicating: Instead of relying on expensive tie lines or toll charges to communicate between offices, VoIP allows you to forward calls over WAN connections.
• Reduced Cost of Cabling: VoIP deployments typically cut cabling costs in half by running a single Ethernet connection instead of both voice and data cables. (This cost savings is most realized in newly constructed offices.)
• Seamless Voice Networks: Because data networks connect offices, mobile workers, and telecommuters, VoIP naturally inherits this property. The voice traffic is crossing “your network” (relatively speaking) rather than exiting to the PSTN. This also provides centralized control of all voice devices attached to the network and a consistent dial-plan. For example, all users can dial each other using four-digit extensions, even though many of them may be scattered around the world.
• Take your Phone with You: Cost estimates for moves, adds, and changes (MAC) to a traditional PBX system range from $55 to $295 per MAC. With VoIP phone systems, this cost is virtually eliminated. In addition, IP phones are becoming increasingly plug-and-play within the local offices, allowing moves with little to no reconfiguration of the voice network. In addition, when combined with a VPN configuration, users can take IP phones home with them and retain their work extension.
• IP SoftPhones: SoftPhones represent an ideal example of the possibilities when combining voice and data networks. Users can now plug a headset into their laptop or desktop and allow it to act as their phone. SoftPhones are becoming increasingly more integrated with other applications such as e-mail contact lists, instant messenger, and video telephony.
• Unified E-mail, VoiceMail, and Fax: All messaging can be sent to a user’s e-mail inbox. This allows users to get all messages in one place and easily reply, forward, or archive messages.
• Increased Productivity: VoIP extensions can forward to ring multiple devices before forwarding to voicemail. This eliminates the “phone tag” game.
• Feature-Rich Communications: Because voice, data, and video networks have combined, users can initiate phone calls that communicate with or invoke other applications from the voice or data network to add additional benefits to a VoIP call. For example, calls flowing into a call center can automatically pull up customer records based on caller ID information or trigger a video stream for one or more of the callers.
• Open, Compatible Standards: In the same way that you can network Apple, Dell, and IBM PCs together, you can now connect devices from different telephony vendors together. Although this benefit has yet to be fully realized, this will allow businesses to choose the best equipment for their network, regardless of the manufacturer.

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@NetwaxLab