Contact Us:





2324 Stanley Avenue

Dayton, Ohio 45404




9891 Montgomery, Rd.

Cincinnati, Ohio 45242




2783 Martin Rd.

Dublin, OH 43017


Mailing Address:

P.O. Box 13343

Dayton, Ohio 45413





Conventional, Digital, VoIP, IP Softphone and Mobile Telephony in one System.
Scalable from 2 to 600 Stations, 1 to 536 Lines

Vertical Summit

Vertical Summit Family of Products

Call 800-821-2686 for a no obligation demonstration and quotation for your business.

Ask about our exclusive 5 year parts and labor warranty!


Key Features
Ohio TeleCom LLC 800-821-2686 Scalable from 2 to 600 Stations, 1 to 536 Lines
Ohio TeleCom LLC 800-821-2686 Connect up to 250 Separate Vertical Summit Systems making one Company Wide Telephone System
Ohio TeleCom LLC 800-821-2686VoIP, IP Telephony, Mobile Client and Conventional Telephony in one Economical Platform
Ohio TeleCom LLC 800-821-2686 5 Year parts and Labor warranty
Ohio TeleCom LLC 800-821-2686 UCS Desktop Client with Voice (Softphone)
Ohio TeleCom LLC 800-821-2686 UCS Mobile Client Presence
Ohio TeleCom LLC 800-821-2686 Voice Conferencing
Ohio TeleCom LLC 800-821-2686 Call Recording
Ohio TeleCom LLC 800-821-2686 Voice Mail w/Email Notification
Ohio TeleCom LLC 800-821-2686 Automatic Call Distribution (ACD)
Ohio TeleCom LLC 800-821-2686 Auto Attendant
Ohio TeleCom LLC 800-821-2686Mobile & SIP Extensions
Ohio TeleCom LLC 800-821-2686 Green Power Save

Voice. UC. BYOD. Mobile.
Now you can have it all – with the versatile Vertical Summit™ unified communications (UC) platform. More than a simple phone system, the Summit gives you cost-effective options that add up to real-time communications and bottom-line business benefits with the ability to easily – and affordably – migrate from analog to IP for true mobility and more. Simple to set up and administer, the Summit’s optimized IP/TDM hybrid architecture gives you all the standard features you need while supporting more advanced UC and mobility applications, so you can communicate and collaborate seamlessly wherever your business takes you. In addition to standard call handling features including one-touch call transfer, call recording, Caller ID and music on hold, the Vertical Summit offers more advanced functions through integrated applications and features such as a multi-level Auto Attendant and voice mail with email notification; at-a-glance presence management and call routing capabilities; videoconferencing; and even the ability to place calls by simply clicking on a number in a Windows-based Web page or document.

Your License to Communicate
To ensure peak performance from the Summit’s powerful suite of multimedia, collaboration and productivity tools and applications, each system includes licenses for the standard Summit Unified Communications Solution (UCS) Desktop Client with Voice (softphone), as well as Summit UCS Mobile Client licenses.* The Summit’s UCS clients give you seamless, single-number connectivity to customers, co-workers and features from your PC or smartphone, so you can:
Ohio TeleCom LLC 800-821-2686 Make, receive and transfer calls from anywhere with one touch
Ohio TeleCom LLC 800-821-2686 Quickly handle calls with at-a-glance, presence-based call management and individual call routing
Ohio TeleCom LLC 800-821-2686 Access directories, call logs, paging and other system features with the tap of a finger
Ohio TeleCom LLC 800-821-2686 Automatically integrate and synchronize private and shared directories with your contacts and schedule for more efficient communications
Ohio TeleCom LLC 800-821-2686 Send and receive secure IM, text and broadcast messages
Ohio TeleCom LLC 800-821-2686 Easily set up and manage videoconferences with up to six people
Ohio TeleCom LLC 800-821-2686 Share applications, white boards and desktops in real time
Ohio TeleCom LLC 800-821-2686 Record calls with a single click
Ohio TeleCom LLC 800-821-2686 Conduct 3-way conference calling

Optimize Your Communications with Optional Applications  
To get peak performance from your Summit system, optional applications are available to further enhance your business’s communications capabilities and bottom line.
IPCR Call Recording

IPCR Call Recording

IP Attendant (Office/Hotel)

IP Attendant (Office/Hotel)



IPCR Call Recording - Ensure compliance with regulatory requirements and improve employee training and customer service with more advanced call recording capabilities. IPCR Call Recording lets you securely record and monitor calls to and from any phone on your Summit system on demand or systemwide, and quickly search, retrieve and replay calls via your Web browser.
IP Attendant (Office/Hotel) - Streamline call handling and distribution with simplified control of the Summit’s Attendant features and functions via this easy-to-use interface and high voice quality, built-in IP softphone. IP Attendant software displays call, user and system status for standard office use, and is also available with a dedicated hospitality telephony feature set that integrates with various hotel/motel property management systems.
ClickCall – Now you can make calls from numbers in any Windows-based application, Web page, or document without dialing your phone. Save time and eliminate misdials by simply highlighting the number and dragging it into the ClickCall pop-up window to place the call automatically from your desktop phone.

Affordable Expandability
Vertical Summit 800

The easily expandable Vertical Summit™ 800 system delivers both digital and VoIP capabilities to small
and medium-sized businesses in a single, cost-effective system for 50 and up to 800 users.

Vertical Summit IP

The cost effective Vertical SummitTM platform is ideally suited for small businesses with five to
50 users, and with optional expansion unit, can accommodate up to 140.

  Easy to set up, maintain and use, each Summit platform gives you the flexibility to design an affordable, dynamic communications system that’s truly the best fit for your business with:
Ohio TeleCom LLC 800-821-2686 Advanced VoIP technology
Ohio TeleCom LLC 800-821-2686 Low cost SIP trunking
Ohio TeleCom LLC 800-821-2686 On/off premise mobility
Ohio TeleCom LLC 800-821-2686 Remote connectivity With the Summit, you can easily expand your communications infrastructure as your business grows with extra expansion units to serve up to 800 users. The Summit is also compatible with Vertical’s SBX IP and MBX IP platforms, so you can quickly network up to 250 sites together while creating a simple migration path to the full-feature and cost-saving benefits of the Summit’s built-in VoIP technology.
Ohio TeleCom LLC 800-821-2686 Displays call, user and system status for faster response to and routing of calls
Ohio TeleCom LLC 800-821-2686 High quality voice communication via built-in IP softphone

Summit Wireless DECT System
Cost-effective, secure and reliable wireless solution to easily expand your coverage, voice traffic and number of users
Ohio TeleCom LLC 800-821-2686 Expands up to 48 extensions
Ohio TeleCom LLC 800-821-2686 Customize by adding base stations (each base supports up to six simultaneous conversations)
Ohio TeleCom LLC 800-821-2686 Improve employee productivity, mobility, reaction time and safety

Powerful, compact communications – in and out of the office.
 With built-in VoIP technologies and advanced pure-IP software, the Vertical Summit is a flexible, cost-effective solution ideally suited for the mobile workplace. Stay connected in and out of the office with the tap of a finger or click of the mouse, and easily expand your communications base as your business grows.

Simple set up
 Installation and maintenance are simple with the Web-based Install Wizard, and the Summit’s award-winning, stylish design allows for compact communications that fit securely in a standard 19” rack. Save power and money, too. With the Summit’s Green Power Save feature, you can automatically or manually disable power to phones connected to the system at night or during holidays for more energy-efficient and cost effective system operation.

Flexible phone options
 Get the most out of the Summit’s feature set with Vertical’s new 9000 Series digital phones and DECT phones featuring display-based interfaces, call logs, self labeling keys and simplified administration. The Summit also integrates with other SBX IP and MBX IP digital, SIP and IP phones, as well as Vodavi single-line analog, XTS, STS and Triad phones to further extend your current communications capabilities and investment. ..........












































“IP Mobility Columbus Ohio Oh ”

IP Mobility Columbus Ohio Oh

IP Mobility Columbus Ohio Oh

IP Mobility Columbus Ohio Oh

IP Mobility Columbus Ohio Oh

IP Mobility Columbus Ohio Oh

Analog audio signals
Analog audio signals are used to transmit voice data over telephone lines. This is done by varying or modulating the frequency of sound waves to accurately reflect the pitch of the sound. The same technology is used for radio wave transmissions.
Asynchronous Communication
A data communications method in which bits are sent one after the other with a start and stop bit IP Mobility Columbus Ohio Oh used for flow control. This as opposed to synchronous communication where blocks of data are transmitted using a synchronizing clock.

ATA or the analog telephone adaptor is the hardware device that connects the conventional IP Mobility Columbus Ohio Oh telephone to the Internet through a high speed bandwidth line, provides the interface to convert the analog voice signals into IP packets, delivers dial tone and manages the call setup.
Audio encoding
The ITU has defined multiple audio codecs for use with H.323. All of them are also compatible with SIP, which is codec-agnostic.

G.711 is 3 kHz audio encoded at 64-kbps. G.711 is PCM audio, the format used for voice delivery over traditional telephone networks and exchanges.

G.722 is high-quality 7kHz audio in 48-, 56-, or 64-kbps streams. Two lower-quality, narrow-band IP Mobility Columbus Ohio Oh revisions exist: G.722.1 encodes the audio at 24- or 32-kbps, and G.722.2 encodes at around 16kbps.

G.723.1 is used for compressing speech at very low bit rates: 5.3- and 6.3-kbps.

G.728 is 3.4kHz audio encoded at 16-kbps, but uses much smaller packet sizes (.625 millisecond, as compared to 37.5ms for G.723.1) to guarantee low delays.

G.729 is a newer voice codec using 8-kbps streams and 15ms packet sizes. There are two variations, G.729 and G.729A, that differ only in their mathematical implementation.

Speex is an open source speech codec. In contrast to the G-series codecs listed above, it is not protected by patents. It encodes at variable bitrates, from 2.15- to 44.2-kbps.

GSM6.10 is another open source codec, encoding at 13.3-kbps. At this time there is an unresolved IP Mobility Columbus Ohio Oh patent dispute surrounding the codec, but is still supported by multiple software programs.

Audio Menu
A verbal choice provided by a recording over the phone. Audio choice menus are common in automated attendant, IVR and fax-on-demand systems. They are prompts for IP Mobility Columbus Ohio Oh caller input. Audio menus can instruct you to speak commands or hit touch-tones as commands.

Audio Response Unit (ARU)
A computer telephony system incorporating voice store and forward technology. There are both passive and interactive ARUs. Passive ARUs simply play out messages. Interactive ones play messages based on input from callers.

Audio Teleconferencing
Or Audio Conferencing. The original technology used for audio teleconferencing was based on PBX conferencing circuits. Setting up conference calls through the PBX is cumbersome, IP Mobility Columbus Ohio Oh voice quality degrades as the number of people on a call increases and there are capacity limitations. As a result, specialized conference bridges were developed to improve capacity and voice quality. Conference bridges, however, require trained operator intervention to schedule and invoke most features. As a result, individual corporations find the cost of ownership prohibitive, and the market for such products has been concentrated on service bureau providers. Today, PC-based systems combine the freedom of conference bridges. By installing a conference server on your voice networks, you can set up, attend, IP Mobility Columbus Ohio Oh and manage your own conferences over any touch-tone telephone. Additionally, users can schedule meetings using desktop software from their e-mail systems, or from a Web browser. The latest word in this area is having the endpoints themselves being able to provide local mixing, hence eliminating the need for network based conference servers!

IP Mobility Columbus Ohio Oh

Bandwidth is the volume of data that can be transmitted over a communication line in a fixed IP Mobility Columbus Ohio Oh amount of time. It is expressed in bits per second (bps) or bytes per second for digital devices and in cycles per second, or Hertz (Hz) for analog devices. Bandwidth can also be defined as the difference between a band of frequencies or wavelengths.

IP Mobility Columbus Ohio Oh

Cable modem

IP Mobility Columbus Ohio Oh

The cable modem is a device that is used to connect a computer to the high speed coaxial cable run by cable TV companies to provide access to the Internet. The connection is made through an Ethernet port, which is a shared medium and IP Mobility Columbus Ohio Oh can affect download speeds if too many users log on simultaneously to the Internet on that particular cable segment. However, despite this cable modems provide extremely fast access to the net.

Call duration
The time interval between when the phone is taken off the hook for a test call and when it is put back on the hook.

Circuit switched networks
These networks have been used for making phone calls since 1878. They use a dedicated point-to-point IP Mobility Columbus Ohio Oh connection for each call. This reduces their utility because no network traffic can move across the switches that are being used to transmit a call.

Client (Softphone client)
The software installed in the user’s IP Mobility Columbus Ohio Oh computer to make calls over the Internet.

Call hunting
A calling feature for inbound calls that will “roll past” a busy signal or try multiple numbers until the call is answered.

Call setup time
The length of time, measured in seconds, required to establish a circuit-switched call between users.

IP Mobility Columbus Ohio Oh

Class 5 (Telephony) switch
A Class 5 switch, in United States telephony jargon refers to a telephone switch or exchange located at the local telephone company’s central office, directly serving subscribers. Class 5 switch services include basic dial-tone, calling features, and additional digital and data services to subscribers using the IP Mobility Columbus Ohio Oh local loop. A key part of SIP/VoIP/IMS networks/systems are IP based class 5 switches (In the IMS environment they are known as class 5 App Servers).

The loss of speech-signal components, resulting in the dropping of the initial or end parts of a word or words.

C-message noise
The noise on a channel or circuit with a termination but no signal (holding tone) at the transmitting end, measured through a C-message filter.

Codec is a term that arises from the Compressor-Decompressor or enCOder/DECoder process. It is used for software or hardware devices that can convert or transform a data stream. For instance, at the transmitting end codecs can IP Mobility Columbus Ohio Oh encode a data stream or data signal for easy transmission, storage or encryption. At the receiving end, they can decode the signal in the appropriate form for viewing. They are most suitable for videoconferencing and streaming media solutions.

This is a term that is used to indicate the squeezing of data in a format that takes less space to store or less bandwidth to transmit. It is very useful in handling large graphics, audio and video files.
Conference Bridge
A device used to connect multiple parties over the phone. A proctor or operator can man conference bridges, or they can be supervised. There are both stand-alone conference bridges and conference bridge functions built in to some PBXs (Private Branch Exchange). These systems have circuitry for summing and balancing the energy (noise) on each channel so everyone can hear each other. More sophisticated conference bridges have the IP Mobility Columbus Ohio Oh ability to “idle” the transmit side of channels of non- speaking parties. Some conference bridges use “clVoxising” to idle or reject the input of touch tones or other signals. There are VoIP based Conference Bridge servers. They may be controlled via protocols such as SIP or Megaco. they send/receive media by using the RTP protocol.

Data compression
This is the process that is used to compress large data files into mall files so that they use less bandwidth during transmission and less disk space when stored. The IP Mobility Columbus Ohio Oh compression depends upon the repeatable patterns of binary 0s and 1s. The higher the number of repeatable patters, the higher is the compression. The right compression codes can compress data files to 40% of their original size. The graphics files can be compressed even more – from 20% to 90%.

Dial-tone delay
The time interval, measured in milliseconds, between when a phone is taken off the hook and when a dial tone sounds.
Digital Subscriber Line
A high-sped digital switched service using existing copper pairs to connect subscriber CPE (Customer Premises Equipment) to the Central Office. DSL handles more data downstream (data flowing towards the subscriber) than upstream (towards the network).


A computer program running on a web server, translating domain names into IP addresses. In the last years special types of domain names records were added to the DNS world-wide system, which provide support to SIP/VoIP (SRV/NAPTR, ENUM).

IP Mobility Columbus Ohio Oh

DSL modem
A DSL modem is a device that is used to connect one or more computers to the high speed DSL line provided by a DSL operator to gain access to the Internet. IP Mobility Columbus Ohio Oh The customers use these modems to log on the net to download or transmit data. Since the DSL lines have high bandwidth capacity the data transfer speeds are very high.

IP Mobility Columbus Ohio Oh

Dual-tone multifrequency (DTMF)
The system used by touch-tone telephones. DTMF assigns a specific frequency (made up of two separate tones) to each key so that it can easily be identified by a microprocessor. This is basically the technology behind touch tone dialing.
The designation for the 2.048Mbps. ITU standard for Europe’s 30-channel digital telephone service. It is the European version of T-1 (DS-1). The bandwidth is IP Mobility Columbus Ohio Oh divided into two signaling channels (channels 15 and 31 starting from 0) and thirty bearer (voice channels). A&B bit signaling (robbed bit signaling) is not used here. E-1 uses one of the control channels for signaling and the other for clock synchronization.

E911 is the short form of the term Enhanced 911, and is used for providing emergency service on cellular and Internet voice calls.

Echo-path delay (EPD)
The time lapse between a transmitted signal and its reflection.

Echo-path loss (EPL)
The difference in signal strength between a transmitted signal and its reflection (expressed in dB). EPL is dependent on EPD.

Emergency 911 calls
This is an emergency telephone number that handles all calls related to police, fire or medical emergencies. The number, which is allotted under the North American IP Mobility Columbus Ohio Oh Numbering Plan (NANP), is answered by either a telephone operator or an emergency service dispatcher, who, in turn, alerts the appropriate emergency service.

ENUM (E.164 Number Mapping)

IP Mobility Columbus Ohio Oh

ENUM is a way to use the Domain Name System (DNS) for storage of E.164 numbers. More specifically, how DNS can be used for identifying available services connected to one E.164 number.
Fax Server
A computer based fax machine. Fax servers are “shared use” devices, typically installed on a LAN. Clients on the LAN can use the fax server from their PCs in much the same way they share a network-based (shared) printer. Faxes can be generated by users at their workstations and “printed” to the fax server for transmission. Likewise, fax servers can route incoming IP Mobility Columbus Ohio Oh faxes to printers, file server directories or to individual users. Fax servers save users from having to print documents, carry them to the fax machine and subsequently wait for them to be transmitted after creating a cover page.

A feature that allows calls to find you wherever you are, ringing multiple phones (such as your cell phone, home phone, and work phone) all at once.

IP Mobility Columbus Ohio Oh

Frame mutes
The duration and number of prolonged clipping events during a call, where the degraded surface of the signal falls close to zero. The ratio of frame mutes to total clipping IP Mobility Columbus Ohio Oh events is displayed by the Frame Muting Ratio (%) indicator.
Frame Relay
In data communications, a packet switching method that uses available bandwidth only when it is needed. This fast packet switching method is efficient enough to transmit voice communications with the proper network management.

Full Duplex
In telephony and data communications, the ability for both ends of a communication to simultaneously send and receive information without degrading the quality or intelligibility of the content.

Gateway In VoIP systems
A network device that converts voice and fax calls in real time from the public switched telephone IP Mobility Columbus Ohio Oh network (PSTN) to an IP network.

An ITU standard that lays down guidelines for real time voice and videoconferencing utilities IP Mobility Columbus Ohio Oh on the Internet. The H.323 standard supports voice, video, data, application sharing and whiteboarding and defines media gateways for conversion to packets.

IP Mobility Columbus Ohio Oh

Refers to devices or deployment strategies designed to provide access to fully functioning systems at all times. One such strategy is to cluster devices so that the primary device can fail over to the secondary one if necessary.

IP Mobility Columbus Ohio Oh

IM, which stands for Instant Messenging, is a software that allows users to exchange messages IP Mobility Columbus Ohio Oh in real time. However, to do so both the users must be logged on to the instant messaging service at the same time. Some of the popular IM services are: MSN Messenger, AOL Instant Messenger, Yahoo! Messenger, Google Talk and ICQ.

IP Mobility Columbus Ohio Oh

IMS stands for IP Multimedia Subsystem. It is a general-purpose, open industry standard for voice and multimedia communications over packet-based IP networks (originally defined by the 3GPP standard organization). It is a core network technology, that can serve as a low-level foundation for technologies like Voice over IP (VoIP), Push-To-Talk (PTT), Push-To-View, Video Calling, and Video Sharing. IMS is based primarily on SIP (session initiation protocol).
Interactive Voice Response IVR.
In computer telephony, Interactive Voice Response is a horizontal application wherein computer-based information is accessed over the phone – with a telephone versus IP Mobility Columbus Ohio Oh a computer. An IVR platform uses computer telephony components to translate callers’ touch-tones or voice commands into computer queries after the callers hear an audio menu. For example: “Please enter your account number using the touch-tones on your telephone.” These queries are then “fetched” by the IVR platform from the host computer. In some cases, the information resides in the same platform (self-hosted). The information is then converted into voice commands and then spoken over the phone to the caller. These spoken prompts can be pre-recorded, digitized speech messages that are then concatenated to form whole sentences. For example: “Your bank balance is five hundred and sixty-three dollars”. The responses to the caller an also take the form of text-to-speech prompts. IVR systems can also be used for callers to change the information in a database instead of just “listen” to the information.

The current-day public and global computer network or “information super-highway.” The Internet is an outgrowth and combination of a variety of university and government sponsored computer networks. Federal and private sector subsidies supported the DARPA-NET. NSFnet (National Sciences Foundation) and thousands of other subnetworks, which were used to do inter-agency research and communication. Today, the IP Mobility Columbus Ohio Oh Internet is made up of millions upon millions of computers and subnetworks – almost entirely supported by commercial funds except in countries where deregulation has not occurred. The internet is the substrate and chief communications backbone for the World Wide Web (WWW), the “graphical interface” of the Internet.

Internet congestion
Internet congestion occurs when a large volume of data is being routed on low bandwidth lines or across networks that have high latency and cannot handle large volumes. The result is slowing down of packet movement, packet loss and drop in service quality.

Internet Telephony (AKA Telephone Systems)
Any means of transmitting the human voice (real time or close to real time) over the internet. There are several components: 1) On the client side, a multimedia-equipped PC with special client software will digitize your voice. This can be done with a voice modem or other voice encoding method; 2) A direct or dial-up connection to the internet allows your voice to be transmitted in packet form to its destination; 3) Connection with the far side is achieved by IP address search, common servers or beacons to identify the called party (and to “ring” that person’s phone); 4) A similar arrangement on the far end completes the call and allows both parties to speak. There are also PSTN/Internet gateways that allow regular telephone callers to make Phone-to-Internet-to-Phone connections. There are PC-to-Phone connections and Phone-to-PC connections.

IP, which is the acronym for Internet Protocol, defines the way data packets, also called datagrams, should be moved between the destination and the source. More technically, it can be defined as the network layer protocol in the TCP/IP communications protocol suite.

IP address
An IP address, also known as Internet Protocol address, is the machine number used to identify all IP Mobility Columbus Ohio Oh devices that are connected to the net. Each device has its own unique number which it uses to communicate. This number is fixed in the case of those computing devices that have a fixed IP address. The rest are allotted a dynamic IP address, which is valid for the period they are connected to the net. The numbers range from to

IP mapping
IP mapping is the process of identifying IP addresses on the basis of their geographical locations. The mapping enables web administrators to pinpoint the location of any computing device connected to the Internet.

IP Phone (AKA Internet Phone or SIP Phone or VoIP Phone (or H.323 Phone))
An IP phone is one that converts voice into digital packets and vice versa to make phone calls over IP Mobility Columbus Ohio Oh Internet possible. It has built-in IP signaling protocols such as SIP or H.323 that ensure that the voice is routed to the right destination over the net. On the media side the IP Phone uses audio or/and video codecs such as G.711 or/and H.261 respectively over RTP. The IP phones come with several value added services like voicemail, e-mail, call number blocking etc.
Internet Service Provider. A business that provides subscriber-based access to the Internet. Subscribers can be individuals or businesses. According to Jack Rickard, publisher of Boardwatch Magazine, ISPs operate at the fourth or lowest level of the Internet. At the third level, regional providers aggregate traffic from lower-order ISPs to the second, backbone level. The highest level in North America is the NAP (Network Access Point), which act as peer-to-peer interconnection points for the largest backbone IP Mobility Columbus Ohio Oh s. There are three “official” NAPs located in San Francisco, Chicago and Pennsauken, New Jersey. ISPs use both Internet Routers, Servers and Rack-Mounted modems to provide a variety of services including Web Site hosting, FTP service, e-mail accounts, unified messaging, IP Mobility Columbus Ohio Oh audio and video broadcasting and in some cases – Internet Telephony and Fax Gateway service.

ITU, which is the acronym of International Telecommunication Union, is a telecommunications standards body based in Geneva. It works under the aegis of the United Nations and makes recommendations on standards in telecommunications, information technology, consumer electronics, broadcasting and multimedia communications.

IP Mobility Columbus Ohio Oh

It is a term used to indicate a momentary fluctuation in the transmission signal. This happens IP Mobility Columbus Ohio Oh in computing when a data packet arrives either ahead or behind a standard clock cycle. In telecommunication, it may result from an abrupt variation in signal characteristics, such as the interval between successive pulses.

IP Mobility Columbus Ohio Oh

Kbps is the acronym for kilobits per second and is used to indicate the data transfer speed. If the modem speed, for instance, is 1 Kbps then it means that the modem can route data at the speed of one thousand bits per second.

Lag is the term used to indicate the extra time taken by a packet of data to travel from the source IP Mobility Columbus Ohio Oh computer to the destination computer and back again. The lag may be caused by poor networking or by inefficient or excessive processing.

Latency is the time that elapses between the initiation of a request for data and the start of the actual data transfer. This delay may be in nanoseconds but it is still used to IP Mobility Columbus Ohio Oh judge the efficiency of networks.

Mean opinion score (MOS)
A measurement of the subjective quality of human speech, represented as a rating index. MOS is derived by taking the average of numerical scores given by juries to rate quality and using it as a quantitative indicator of system performance.

IP Mobility Columbus Ohio Oh

MEGACO/H.248 (RFC 3525 defines version 1 (replaced MGCP))
This is the latest industry standard protocol for interfacing between hosts and call agents called Media IP Mobility Columbus Ohio Oh Gateway Controllers (MGC’s) and Media Gateways (MG’s) – eg. an IP Telephone and the PSTN. The standard is the result of a unique collaborative effort between the IETF and ITU standards organizations. Derived from MGCP (which, in turn, was derived from the combination of SGCP and IPDC).
In computer telephony, any means of message store and forward. This includes fax mail, voice mail and broadcast messaging. This horizontal application is the most popular of all other voice solutions. Messaging systems provide for the store and IP Mobility Columbus Ohio Oh forward of “non-real time” communication. For example, a recorded voice message can be stored for later play back either locally or remotely, or a fax can be received and stored before it is re-transmitted to the ultimate recipient. Messages, then, can vary in content and media type – the distinction being that they are recorded or stored for pick up in the future. The time between original storage and retrieval of a message can be created and stored by a sales manager for later retrieval by multiple (worldwide) sales people. The sales staff can listen to the message at different times over an extended period. This is due to the nature if random retrieval by the recipients in their respective time zones. Messaging systems are a kind of “shared tenant” answering machine, because messages that were intended for as many as a thousand or more users IP Mobility Columbus Ohio Oh can be stored and controlled by the same system. If a community of users agree on some basic ground rules, messages can be shared, forwarded, and distributed to multiple recipients in the same fashion as e-mail.

MGCP (later was replaced by Megaco/H.248)
Media Gateway Control Protocol; RFC 2705 – is worth mentioning. It is an in-development IETF standard for converting voice signals from the conventional telephone network into data packets (and vice-versa), and may be used in conjunction with SIP or H.323. As its name suggests, it is used mainly by Media Gateway Controllers to control Media Gateways.
Short for Modulator/Demodulator. Equipment that converts digital signals to analog signals and vice-versa. Modems are used to send data signals (digital) over the telephone network, which is usually analog. A modem modulates binary signals into tones that can be carried over the telephone network. At the other end, the demodulator part of the modem converts the tones to binary code.

Stands for North American Numbering Plan. A telephone numbering system that has evolved the way area IP Mobility Columbus Ohio Oh codes and numbers are allotted. The system was established in 1947 and covers the United States, Canada and a few neighboring areas. It uses a three-digit area code and seven-digit telephone numbers. Its fiat is, however, limited to the public switched telephone networks only.

A logically grouped unit of data. Packets contain a payload (the information to be transmitted), originator, destination and synchronizing information. The idea with packets is to transmit them over a network so each individual packet can be sent along the most optimal route to its. Packets are assembled on one end of the communication and re-assembled on the receiving end based on the header addressing information at the front of each packet. Routers in the network will store and forward packets based on network delays, errors and re-transmittal requests from the receiving end.

Packet loss
Packet loss is the term used to indicate the loss of data packets during transmission over a computer network. This may happen on account of high network latency or on account of overloading of switches or routers that are unable to process or route all the incoming data.

Packet Switching
A means of economically sending and receiving data over alternate, multiple network channels. The premise for packet switching is the packet, a small bundle of information containing the payload and routing information. Packet switching takes data, breaks it down into packets, transmits the packets and does the reverse on the other end. Packets can be sent in order and then be received in a different order – only to be put back in the correct order IP Mobility Columbus Ohio Oh in seconds. There are slow packet switching networks, like the old SNA networks – and there are fast packet networks based on Frame Relay and ATM. Although traditionally used for data, packet networks, especially well-managed ones, are becoming suitable for real-time transmission of voice and video.

IP Mobility Columbus Ohio Oh

Private Branch Exchange. Or PABX (Private Automatic Branch Exchange). In telephony, a PBX system behaves as a customer’s premises over trunk lines (thus the term “branch”). At first, PBXs mimicked a small telephone company switchboard. Users would use an operator to take and make telephone calls to and from the PSTN (Public Switched Telephone Network). Over time, users were able to dial directly, without the use of an operator. Today, computer telephony platforms such as automated attendants are able to route incoming calls automatically, too.

Peer-to-Peer (P2P)
The term peer-to-peer is used to indicate a form of computing where two or more than two users can IP Mobility Columbus Ohio Oh share files or CPU power. They can even transmit real time data such as telephony traffic on their highly ad hoc networks. Interestingly, the peer-to-peer network does not work on the traditional client-server model but on equal peer nodes that work both as “clients” and “servers” to other nodes on the network.
Point of Presence, equivalent of a local phone company’s central office. The place your long distance carrier terminates your long distance lines just before those lines are IP Mobility Columbus Ohio Oh connected to your local phone company’s lines, or to your own direct hookup.

Alternate Definition: Post Office Protocol. An Internet standard for the storage and retrieval of email messages

Post-dial delay
The time interval between when the caller presses the last digit of a number and when the phone on the other end begins to ring. It is the basic quantifier for routing speed as perceived by the user.

IP Mobility Columbus Ohio Oh

POTS (plain old telephone service)
The typical, familiar model of a single phone line and a single phone number.

It is a convention or standard that defines the procedures to be adopted regarding the transmission of data between two computing end points. These procedures include the way the sending device should sign off a message or how the receiving device should indicate the receipt of a message. Similarly, the protocols also lay down guidelines for error checking, data compression, and other relevant operational details.
Public Switched Telephone Network. The combination of local, long-distance, and international carriers that make up the worldwide telephone network. IP Mobility Columbus Ohio Oh

QoS (quality of service)
The ability of a network (including applications, hosts, and infrastructure devices) to deliver traffic with minimum delay and maximum availability.
Real Time
A communication wherein any perceptible delay between the sender and receiver are minimal IP Mobility Columbus Ohio Oh and tolerated. Regular telephone calls are real time. Point-to-point fax transmissions are “close” to real time. Voice messaging is in non-real time.

The designation for connecting a tip and ring circuit to a standard, modular, six-position jack. The green and red wires go in the middle (only) pair, and the outside positions of the connector are unused.

Eight-position modular connector used for data transmission over standard twisted or flat pairs.

A router is a network device that that handles message transfer between computers that form part of the Internet. The messages, which are in the form of data IP Mobility Columbus Ohio Oh packets, are forwarded to their respective IP destinations by the router. A router can also be called the junction box that routes data packets between computer networks.

This is a methodology used to measure the value of an analog signal at regular intervals, and encoding IP Mobility Columbus Ohio Oh it into a digital format for VoIP phone services.
Service Provider
An addressable entity providing application and administrative support to the client environment by responding to client requests and maintaining the operational integrity of the server.

Signaling System #7
Or SS7. The basis for modern methods to route traffic with out-of-brand signaling. Its forerunner, CCIS (Common Channel Interoffice Signaling), used 4.8 Kbps data links to transmit call set up and tear down messages to switching office adjunct computers and packet switches. SS7 in itself is not a network service offering, but rather the underlying infrastructure with which many existing and proposed offerings are based. For example, local Basic Rate ISDN (BRI) services can tap into SS7, so 64 Kbps packetized data can be routed with the help of the network’s out-of-band signaling capability. In addition, nationwide Primary Rate ISDN (PRI) services can use the same backbone.

SIP (Session Initiation Protocol)
An Internet Engineering Task Force (IETF) standard for initiating, maintaining, and terminating an IP Mobility Columbus Ohio Oh interactive user session involving video, voice, chat, gaming, virtual reality, and more.

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SIP phone (Also see above IP Phone)
A SIP phone is a telephone that uses the SIP (Session Initiation Protocol) standard to make a voice call over the Internet (for signaling (and uses RTP for media)). The SIP IP Mobility Columbus Ohio Oh phones come with several value added services like voicemail, e-mail, call number blocking etc. There are (normally) no charges for making calls from one SIP phone to another, and negligible charges for routing the call from a SIP phone to a PSTN phone.

Skype is a peer-to-peer Internet telephony company that revolutionized the way voice calls are made by using VoIP technology. The company, which has been acquired by eBay, was founded by Niklas Zennström and Janus Friis. Skype users can speak to other Skype users for free, but have to pay a small fee for calling or receiving calls from conventional phones.

Soft phone

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Telephone Systems software that lets users send and receive calls from non-dedicated hardware, such as a PC or Pocket PC device. It is typically used with a headset and microphone.
Note: Soft Phone and SIP Phone might be (but not necessarily) special cases of each other.

Soft switch
It is a software application that is used to keep track of, monitor or regulate connections at the junction point between circuit and packet networks. This software is loaded in computers and is now replacing hardware switches on most telecom networks.

Speech power
The measure of the strength of a received voice signal.
Speech Recognition
Speech recognition describes a group of special technologies that allow callers to speak words, phrases, or IP Mobility Columbus Ohio Oh utterances that are used to control applications. In the case of voice processing, speech recognition is used to replace touch-tone input, make for more intuitive menu structures, and ad a level of simplicity and security to some systems. Speech recognition, on the other hand, is a technology that uses the spoken word as input that has an effect on the logic flow and execution of the program in question.

Store And Forward
As the name implies, the discipline of storing a message or transmission for later playback or transmission. As opposed to real time communication, store and forward is the basis for all messaging systems including email, fax-on-demand, unified messaging, etc. In data communications, store and forward applies to momentary buffering of packets or other data strings.

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North American digital standard for high-capacity transmission of telephony and data communications. In telephone T-1 provides a 1.544 Mbps link which is broken down IP Mobility Columbus Ohio Oh in to 24 discrete, 64 Kpbs voice-grade channels. In data communications, T-1 links are used to directly connect CPE (Customer Premises Equipment) routers to the Internet and for Private Data Network or VPN circuits.

North American standard for DS-3. Operates at a signaling rate of 44.736 Mbps, or the equivalent of 28 T-1s.

Transmission Control Protocol. IP Mobility Columbus Ohio Oh The transport layer protocol developed for the ARPAnet which comprises layers 4 and 5 of the OSI model. TCP controls sequential data exchange in TCP/IP for remotely hosts in a peer-to-peer network.

Taken from Greek root words meaning “far sound”, telephony is the discipline of converting or transmitting voice or other signals over a distance, and then re-converting them to an audible sound at the far end.

A multi-user, multi-tasking operating system originally developed in 1969 by Ken Thompson of AT&T Bell Laboratories. UNIX is used in telephone company and mission critical applications.

Video encoding
There are fewer video codecs (than audio codecs) associated with the H.323 and SIP protocol suites (thankfully).

H.261 is a video codec use for wideband (>= 64Kbps). H.263 is used for narrowband (< 64-kbps). Both are widely supported.

H.264 is a newer narrowband codec that produces higher-quality results than H.263 and is IP Mobility Columbus Ohio Oh recommended in its place. H.264 is also known as ISO 14496-10 and as MPEG-4 part 10 and as MPEG-4 AVC (Advanced Video Coding).

Voice Messaging
An application of store and forward wherein telephone access to private messages are retrieved by users for playback. Imagine a shared tenant answering machine that handles multiple telephone lines and can record incoming messages for hundreds of people simultaneously. Imagine the intended parties being able to retrieve these messages over the phone with simple touch-tone commands. Imagine full security, so no one can pick up anyone else’s messages without a special, private access code. That’s voice messaging. Voice messaging systems take many forms. IP Mobility Columbus Ohio Oh There are CPE (Customer Premises Equipment) versions and Service Bureau or Telco versions. The basic idea is the non real-time sending and receiving of private messages. Some systems support the broadcast of messages to multiple recipients. Some provide message waiting notification via pager, message waiting light or “outdial” telephone calls.

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VoIP (Voice over IP)
The process of making and receiving voice transmissions over any IP network. IP networks include the Internet, office LANs, and private data networks between corporate offices. The main advantage of VoIP is that users can connect from anywhere and make phone calls without incurring typical analog telephone charges, such as for long-distance calls.

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VoIP closed systems (as opposed to Open Standards (such as SIP, H.323 or MGCP)
AOL, Yahoo, and Apple all offer “voice chat” capability via their instant messaging networks. These systems are closed and for the most part unable to interoperate with other, standards-based products and may use undocumented protocols. However, even where the protocols are known or have been reverse-engineered, IP Mobility Columbus Ohio Oh the audio codecs are proprietary. It is known that AOL’s voice chat uses codecs from Qualcomm, Yahoo’s uses TrueSpeech from DSP Group, and Apple’s uses PureVoice QCELP.
The popular Skype service is similarly closed. It is known to use three audio codecs: iLBC (Internet Low-Bitrate Codec) and iSAC (Internet Speech and Audio Coder) from GlobalIPSound, and a third as-yet unidentified codec. The Skype protocols have not been reverse-engineered.

VOIP Gateway
This device provides the conversion interface between the public switched telephone network (PSTN) and an IP network for voice and fax calls. Its primary functions include: voice and fax compression/decompression, packetization, call routing and control signaling. It also provides an interface to Gatekeepers or Softswitches, billing systems, and network management systems.

VoIP PBX, which stands for Voice over Internet Protocol Private Branch eXchange, is a telephone switch that converts IP phone calls into traditional circuit-switched IP Mobility Columbus Ohio Oh TDM connections. It also supports traditional analog and digital telephones.

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VOIP Phone
A VoIP phone is one that uses the Internet to route voice calls by converting the voice data into IP packets and vice versa. The phones come with built-in IP signaling IP Mobility Columbus Ohio Oh protocols such as H.323 or SIP that help in the routing of data to the right destination. A VoIP phone can also be a software application that is installed in the user’s PC. In this case it is known as the Softphone. Also, the calls in this case have to be made from the PC, and not through a telephone instrument.
Web Browser
Client software used to view information on Web servers. Can display graphics. Web browsers are also packaged with email clients, newsreaders and in some cases, Telephone Systems clients.

Web-Enabled Call Center
Any call center whose “callers” can establish a traditional of Internet-Based phone call with an agent initiated via Web Browsing Interaction. Imagine this: You cruise to a Web Page and see a product you’d like to buy. You click on a button that says “speak to a live agent”. A form pops-up and you’re prompted to enter your phone number. A few moments later your phone rings. It’s an agent from the call center associated with the Web Page you just visited.

Web Server
On the World Wide Web, a server dedicated to storing data (such as Web pages in HTML format) and distributing it to Web Browsing users. Web browsers are able to download video, text, still images and audio from Web Pages. Some servers support Unified Messaging.

Wideband noise
The noise level measured on a wideband channel in the absence of a signal.

WiFi Hotspot
An area where a wireless access point enables users carrying wireless-enabled laptops to log on to the Internet. The limiting condition is that the access point is configured to broadcast its presence and does not require authorization for access. Generally, WiFI hotspots are located in public places like airports, train stations, libraries, marinas, convention centers, coffee shops and hotels.

WiFi phone
A WiFI phone is one that enables users to make phone calls from public WiFi hotspots or residential WiFI network environments. Besides voice calls, these phones can be used to send e-mails wirelessly.
Products and Solutions
Solution By Tech IP Phone Systems
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Whether via distributed architecture or in the cloud, Vertical IP PBX makes communications easier
What Is An IP Phone System?
At the heart of every business phone system is the PBX (Private Branch Exchange), which makes connections among the internal telephones of a business or other IP Mobility Columbus Ohio Oh private organization and connect them to the public switched telephone network (PSTN). Traditional hard-wired PBX systems evolved in the 1990s to use Internet Protocol (IP) to carry calls. An IP PBX uses Voice Over Internet Protocol (VoIP) and can also be known as a VoIP PBX, IP-PBX, virtual PBX or IPBX.

IP PBX phone systems perform four main call processing duties:

Establishing connections between the telephone sets of two users
Maintaining the connections as long as needed
Disconnecting the connections when the users hang up
Providing information for accounting purposes
An IP PBX system consists VoIP enabled phones and an IP PBX. The phones register with the IP PBX server, and when they make a call the IP PBX establishes the connection. VoIP phones can be simple software-based softphones or purpose-built hardware devices that appear much like an ordinary telephone or a cordless phone.

Vertical IP PBX integrates communication features such as video conferencing, instant messaging (IM), mobility and online collaboration into a single easy-to-use IP PBX solution. Eliminating separate tools is only one way that Vertical IP PBX’s brilliantly simple VoIP phone systems help boost IP Mobility Columbus Ohio Oh productivity and reduce costs.

Vertical IP PBX For Managed Cloud Phone Systems
Vertical IP PBX is focused on providing brilliantly simple communications solutions, and that’s why we offer a smarter cloud-based phone system, with flexibility and service beyond just dial tone. We’ve been voice specialists since the beginning of the VoIP revolution. We provide a wide range of business phone products and services that address IP Mobility Columbus Ohio Oh organization’s business communication needs – no matter how large or complex. Our cloud-based phone system is at the heart of what we do: easy to install, easy to use, available throughout the U.S., and works anywhere in the world.

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Most hosted cloud business phone service providers utilize core technology that is developed and maintained by a third party. But Vertical IP PBX is an “end-to-end” provider, from the phones to the platform to the applications software—so of course we built our own hosted platform in the cloud. Our cloud phone system is the key to our solution and is engineered for highest reliability and functionality.

Our technology tailors the user experience for companies who put a premium on sales and service and consider the phone to be a strategic part of their business. It IP Mobility Columbus Ohio Oh allows us to integrate more tightly with other business applications and to have granular data measuring everything we manage.

Vertical IP PBX For Onsite Business Phone Systems
Built to leverage the power of VoTelephone Systems, Vertical IP PBX IP phone systems have pioneered a fundamentally different approach to IP PBX. Thanks to its ingenious purpose-built single-image architecture, a Vertical IP PBX on-premises communications platform grows across as many sites, or as many continents, as you need. IT staff can manage your entire VoIP phone system with plug-and-play ease using a single browser-based interface. And because it is an open system, it integrates with popular business applications, enabling you to get more out of your most valuable assets: people and information.

The Vertical IP PBX distributed architecture is incorporated into a unique on-site, appliance-based, IP PBX platform with no single point of failure: each switch and site functions as an independent call processor. In the event of wide area network (WAN) failure, the phone system continues to place IP Mobility Columbus Ohio Oh and receive calls on the Public Switched Telephone Network (PSTN). This gives customers 99.999% availability for 100% peace of mind.

Vertical IP PBX’s on-premises IP PBX phone system offers the lowest  in the industry. Many customers report a return of investment within a year. Over the long term, the unified communications tools of a Vertical IP PBX business VoIP telephone system reduce costs company-wide by streamlining business processes, putting critical information in reach, and eliminating both missed calls and the need for expensive third-party conference services.

Which Is Right For Your Company?
Some things to consider as you pick your VoIP business phone solution

Vertical IP PBX Sky is the most reliable VoIP hosted cloud business phone system

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A hosted, managed cloud phone system

Consider these factors:

Are you ready to stop managing your phone system?
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Do you want your phone system to upgrade to the newest version automatically?
Do you prefer a monthly subscription to a capital investment?
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An owned and operated onsite phone system

Consider these factors:

Do you want to control and manage IP Mobility Columbus Ohio Oh your phone system in-house?
Do you plan to deploy your phone system during a coming quarter?
Do you prefer to have your IT team upgrade your phone system on their schedule?
Do you prefer a planned capital investment to a monthly operational expense?


Systems Overview

cloud based phone

Vertical SBX Cloud Based Phone System

Vertical SBX, the leading manufacturer of telephone system across the world, provides the best communication solutions and services. They have brought in innovation into services and Vertical SBX has a large network of dealers to provide the best possible solutions to businesses across the world. There are a variety of cloud based phone systems available from Vertical SBX to meet a wide range of enterprise communication needs.

Vertical SBX has even come up with their unique cloud based phone solution – VIPedge. This solution is IP Mobility Columbus Ohio Oh best suited for organizations that want to avail the most advanced telephony feature without investing a lot. can be deployed without any upfront costs where users are able to leverage the power of by paying only a monthly subscription fee. Vertical SBX maintains the entire system on the cloud and customers need not worry about anything other than answering the incoming calls.

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Business of every size would be able to use and get the best out of their communication systems. Switching to Vertical SBX VIPedge is extremely easy where you will hardly have to worry about the hardware infrastructure and the complex equipments.

Voice over IP
From Wikipedia, the free encyclopedia
Voice over IP (VoIP) is a methodology and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. Other terms commonly associated with VoIP are Telephone Systems, Internet telephony, broadband telephony, and broadband phone service.

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The term Internet telephony specifically refers to the provisioning of communications services (voice, fax, SMS, voice-messaging) over the public Internet, rather than via the public switched telephone network (PSTN). The steps and principles IP Mobility Columbus Ohio Oh 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.

Early providers of voice-over-IP services offered business models and technical solutions that mirrored the architecture of the legacy telephone network. Second-generation providers, such as Skype, have built closed networks for private user bases, offering the benefit of free calls and convenience while potentially charging for access to other communication networks, such as the PSTN. This has limited the freedom of users to mix-and-match third-party hardware and software. Third-generation providers, such as Google Talk, have adopted[1] the concept of federated VoIP—which is a departure from the architecture of the legacy networks. These solutions typically allow dynamic interconnection between users on any two domains on the Internet when a user wishes to place a call.

VoIP systems employ session control and signaling protocols to control the signaling, set-up, and tear-down of calls. They transport audio streams over IP networks using special media delivery protocols that encode voice, audio, video with audio codecs, and video codecs as Digital audio by streaming media. IP Mobility Columbus Ohio Oh Various codecs exist that optimize the media stream based on application requirements and network bandwidth; some implementations rely on narrowband and compressed speech, while others support high fidelity stereo codecs. Some popular codecs include μ-law and a-law versions of G.711, G.722, a popular open source voice codec known as iLBC, a codec that only uses 8 kbit/s each way called G.729, and many others.

VoIP is available on many smartphones, personal computers, and on Internet access devices. Calls and SMS text messages may be sent over 3G/4G or Wi-Fi.[2]

Contents [hide]
1 Pronunciation
2 Protocols
3 Adoption
3.1 Consumer market
3.2 PSTN and mobile network providers
3.3 Corporate use
4 PSTN integration
4.1 Number portability
4.2 Emergency calls
5 Fax support
6 Power requirements
7 Security
8 Caller ID
9 Compatibility with traditional analog telephone sets
10 Support for other telephony devices
11 Operational cost
12 Regulatory and legal issues
12.1 European Union
12.2 India
12.3 Middle East
12.4 South Korea
12.5 United States
13 Historical milestones
14 Quality of service
15 See also
16 References
17 External links
The term VoIP may be pronounced as initials (V-O-I-P) or as an acronym, usually voyp, as in voice.[3] or it may be spoken as Voice over I-P.

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

Media Gateway Control Protocol (MGCP)
Session Initiation Protocol (SIP)
H.248 (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
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.

Consumer market[edit]

Example of residential network including VoIP
A major development that started in IP Mobility Columbus Ohio Oh 2004 was the introduction of mass-market VoIP services that utilize existing broadband Internet access, by which subscribers place and receive telephone calls in much the same manner as they would via the public switched telephone network (PSTN). Full-service VoIP phone companies provide inbound and outbound service with direct inbound dialing. Many offer unlimited domestic calling for a flat monthly subscription fee. This sometimes includes international calls to certain countries. Phone calls between subscribers of the same provider are usually free when flat-fee service is not available. A VoIP phone is necessary to connect to a VoIP service provider. This can be implemented in several ways:

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Dedicated VoIP phones connect directly to the IP network using technologies such as wired Ethernet or Wi-Fi. They are typically designed in the style of traditional digital business telephones.
An analog telephone adapter is a device that connects to the network and implements the electronics and firmware to operate a conventional analog telephone attached through a modular phone jack. Some residential Internet gateways and cablemodems have this function built in.

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A softphone is application software installed on a networked computer that is equipped with a microphone and speaker, or headset. The application typically presents a dial pad and display field to the user to operate the application by mouse clicks or keyboard input.
PSTN and mobile network providers[edit]
It is becoming increasingly common for telecommunications providers to use VoTelephone Systems over dedicated and public IP networks to connect switching centers and to interconnect with other telephony network providers; this is often referred to as “IP backhaul”.[4][5]

Smartphones and Wi-Fi-enabled mobile phones may have SIP clients built into the firmware or available as an application download.

Corporate use[edit]
Because of the bandwidth efficiency and low costs that VoIP technology can provide, businesses are migrating from traditional copper-wire telephone systems to VoIP systems to reduce their monthly phone costs. In 2008, 80% of all new Private branch exchange (PBX) lines installed internationally were VoIP.[6]

VoIP solutions aimed at businesses have evolved into unified communications services that treat all communications—phone calls, faxes, voice mail, e-mail, Web conferences, and more—as discrete units that can all be delivered via any means and to any handset, including cellphones. Two kinds of competitors are competing in this space: one set is focused on VoIP for medium to large enterprises, while another is targeting the small-to-medium business (SMB) market.[7]

VoIP allows both voice and data communications to be run over a single network, which can significantly reduce infrastructure costs.[8]

The prices of extensions on VoIP are lower than for PBX and key systems. VoIP switches may run on commodity hardware, such as personal computers. Rather than closed architectures, these devices rely on standard interfaces.[8]

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VoIP devices have simple, intuitive user interfaces, so users can often make simple system configuration changes. Dual-mode phones enable users to continue their conversations as they move between an outside cellular service and an internal Wi-Fi network, so that it is no longer necessary to carry both a desktop phone and a cellphone. Maintenance becomes simpler as there are fewer devices to oversee.[8]
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Skype, which originally marketed itself as a service among friends, has begun to cater to businesses, providing free-of-charge connections between any users on the Skype network and connecting to and from ordinary PSTN telephones for a charge.[9] IP Mobility Columbus Ohio Oh

In the United States the Social Security Administration (SSA) is converting its field offices of 63,000 workers from traditional phone installations to a VoIP infrastructure carried over its existing data network.[10][11]

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PSTN integration[edit]
The Media VoIP Gateway connects the digital media stream, so as to complete creating the path for voice as well as data media. It includes the interface for connecting the standard PSTN networks with the ATM and Inter Protocol networks. The Ethernet interfaces are also included in the modern systems, which are specially designed to link calls that are passed via the VoIP.[12] IP Mobility Columbus Ohio Oh

E.164 is a global numbering standard for both the PSTN and PLMN. Most VoIP implementations support E.164 to allow calls to be routed to and from VoIP subscribers and the PSTN/PLMN.[13] VoIP implementations can also allow other identification techniques to be used. For example, Skype allows subscribers to choose “Skype names”[14] (usernames) whereas SIP implementations can use URIs[15] similar to email addresses. Often VoIP implementations employ methods of translating non-E.164 identifiers to E.164 numbers and vice versa, such as the Skype-In service provided by Skype[16] and the ENUM service in IMS and SIP.[17]

Echo can also be an issue for PSTN integration.[18] Common causes of echo include impedance mismatches in analog circuitry and acoustic coupling of the transmit and receive signal at the receiving end.

Number portability[edit]
Local number portability (LNP) and Mobile number portability (MNP) also impact VoIP business. In November 2007, the Federal Communications Commission in the United States released an order extending number portability obligations to interconnected VoIP providers and carriers that support VoIP providers.[19] Number portability is a service that allows a subscriber to select a new telephone carrier without requiring a IP Mobility Columbus Ohio Oh new number to be issued. Typically, it is the responsibility of the former carrier to “map” the old number to the undisclosed number assigned by the new carrier. This is achieved by maintaining a database of numbers. A dialed number is initially received by the original carrier and quickly rerouted to the new carrier. Multiple porting references must be maintained even if the subscriber returns to the original carrier. The FCC mandates carrier compliance with these consumer-protection stipulations.

A voice call originating in the VoIP environment also faces challenges to reach its destination if the number is routed to a mobile phone number on a traditional mobile carrier. VoIP has been identified in the past as a Least Cost Routing (LCR) system, which is based on checking the destination of each telephone call as it is made, and then sending the call via the network that will cost the customer the least. This rating is subject to some debate given the complexity of call routing created by number portability. With GSM number portability now in place, LCR providers can no longer rely on using the network root prefix to determine how to route a call. Instead, they must now determine the actual network of every number before routing the call.

Therefore, VoIP solutions also need to handle MNP when routing a voice call. In countries without a central database, like the UK, it might be necessary to query the GSM network about which home network a mobile phone number belongs to. As the popularity of VoIP increases in the enterprise markets because of least cost routing options, it needs to provide a certain level of reliability when handling calls.
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MNP checks are important to assure that this quality of service is met. Handling MNP lookups before routing a call provides some assurance that the voice call will actually work.

Emergency calls[edit]
A telephone connected to a land line has a direct relationship between a telephone number and a physical location, which is maintained by the telephone company and available to emergency responders via the national emergency response service centers in form of emergency subscriber lists. When an emergency call is received by a center the location is automatically determined from its databases and displayed on the operator console.

In Telephone Systems, no such direct link between location and communications end point exists. Even a provider having hardware infrastructure, such as a DSL provider, may only know the approximate location of the device, based on the IP address allocated to the network router and the known service address. However, some ISPs do not track the automatic assignment of IP addresses to customer equipment.[20] IP Mobility Columbus Ohio Oh

IP communication provides for device mobility. For example, a residential broadband connection may be used as a link to a virtual private network of a corporate entity, in which case the IP address being used for customer communications may belong to the enterprise, not being the network address of the residential ISP. Such off-premises extensions may appear as part of an upstream IP PBX. On mobile devices, e.g., a 3G handset or USB wireless broadband adapter, the IP address has no relationship with any physical location known to the telephony service provider, since a mobile user could be anywhere in a region with network coverage, even roaming via another cellular company.

At the VoIP level, a phone or gateway may identify itself with a Session Initiation Protocol (SIP) registrar by its account credentials. In such cases, the Internet telephony service provider (ITSP) only knows that a particular user’s equipment is active. Service providers often provide emergency response services by agreement with the user who registers a physical location and agrees that emergency services are only provided to that address if an emergency number is called from the IP device. IP Mobility Columbus Ohio Oh

Such emergency services are provided by VoIP vendors in the United States by a system called Enhanced 911 (E911), IP Mobility Columbus Ohio Oh based on the Wireless Communications and Public Safety Act of 1999. The VoIP E911 emergency-calling system associates a physical address with the calling party’s telephone number. All VoIP providers that provide access to the public switched telephone network are required to implement E911,[20] a service for which the subscriber may be charged. However, end-customer participation in E911 is not mandatory and customers may opt out of the service.[20]

The VoIP E911 system is based on a static table lookup. Unlike in cellular phones, where the location of an E911 call can be traced using assisted GPS or other methods, the VoIP E911 information is only accurate so long as subscribers, who have the legal responsibility, are diligent in keeping their emergency address information current.

Fax support[edit]
Support for fax has been problematic in many VoIP implementations, as most voice digitization and compression codecs are optimized for the representation of the human voice and the proper timing of the modem signals cannot be guaranteed in a packet-based, connection-less network. An alternative IP-based solution for delivering fax-over-IP called T.38 is available. Sending faxes using VoIP is sometimes referred to as FoIP, or Fax over IP.

The T.38 protocol is designed to compensate for the differences between traditional packet-less communications over analog lines and packet-based transmissions IP Mobility Columbus Ohio Oh which are the basis for IP communications. The fax machine could be a traditional fax machine connected to the PSTN, or an ATA box (or similar). It could be a fax machine with an RJ-45 connector plugged straight into an IP network, or it could be a computer pretending to be a fax machine.[21] Originally, T.38 was designed to use UDP and TCP transmission methods across an IP network. TCP is better suited for use between two IP devices. However, older fax machines, connected to an analog system, benefit from UDP near real-time characteristics due to the “no recovery rule” when a UDP packet is lost or an error occurs during transmission.[22] UDP transmissions are preferred as they do not require testing for dropped packets and as such since each T.38 packet transmission includes a majority of the data sent in the prior packet, a T.38 termination point has a higher degree of success in re-assembling the fax transmission back into its original form for interpretation by the end device. This in an attempt to overcome the obstacles of simulating real time transmissions using packet based protocol.[23]

There have been updated versions of T.30 to resolve the fax over IP issues, which is the core fax protocol. Some newer high end fax machines have T.38 built-in capabilities which allow the user to plug right into the network and transmit/receive faxes in native T.38 like the Ricoh 4410NF Fax Machine. A unique feature of T.38 is that each packet contains a portion of the main data sent in the previous packet. With T.38, two successive lost packets are needed to actually lose any data. The data one will lose will only be a small piece, but with the right settings and error correction mode, there is an increased likelihood that they will receive enough of the transmission to satisfy the requirements of the fax machine for output of the sent document.

While many late-model analog IP Mobility Columbus Ohio Oh telephone adapters (ATAs) support T.38, uptake has been limited as many voice-over-IP providers perform least-cost routing which selects the least expensive PSTN gateway in the called city for an outbound message. There is typically no means to ensure that that gateway is T.38 capable. Providers often place their own equipment (such as an Asterisk PBX installation) in the signal path, which creates additional issues as every link in the chain must be T.38 aware for the protocol to work. Similar issues arise if a provider is purchasing local direct inward dial numbers from the lowest bidder in each city, as many of these may not be T.38 enabled.

Power requirements[edit]
Telephones for traditional residential analog service are usually connected directly to telephone company phone lines which provide direct current to power most basic analog handsets independently of locally available electrical power.

IP Phones and VoIP telephone adapters connect to routers or cable modems which typically depend on the availability of mains electricity or locally generated power.[24] Some VoIP service providers use customer premises equipment (e.g., cablemodems) with battery-backed power supplies to assure IP Mobility Columbus Ohio Oh uninterrupted service for up to several hours in case of local power failures. Such battery-backed devices typically are designed for use with analog handsets.
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Some VoIP service providers implement services to route calls to other telephone services of the subscriber, such a cellular phone, in the event that the customer’s network device is inaccessible to terminate the call.

The susceptibility of phone service to power failures is a common problem even with traditional analog service in areas where many customers purchase modern IP Mobility Columbus Ohio Oh telephone units that operate with wireless handsets to a base station, or that have other modern phone features, such as built-in voicemail or phone book features.

IP Mobility Columbus Ohio Oh

The security concerns of VoIP telephone systems are similar to those of any Internet-connected device. This means that hackers who know about these vulnerabilities can institute denial-of-service attacks, harvest customer data, record conversations and compromise voicemail messages. The quality of internet connection determines the quality of the calls. VoIP phone service also will not work if there is power outage and when the internet connection is down. The 9-1-1 or 112 service provided by VoIP phone service is also different from analog phone which is associated with a fixed address. The emergency center may not be able to determine your location based on your virtual phone number.[25][26][27] Compromised VoIP user account or session credentials may enable an attacker to incur substantial charges from third-party services, such as long-distance or international telephone calling.

IP Mobility Columbus Ohio Oh

The technical details of many VoIP protocols create challenges in routing VoIP traffic through firewalls and network address translators, used to interconnect to transit networks or the Internet. Private session border controllers are IP Mobility Columbus Ohio Oh often employed to enable VoIP calls to and from protected networks. Other methods to traverse NAT devices involve assistive protocols such as STUN and Interactive Connectivity Establishment (ICE).

Many consumer VoIP solutions do not support encryption of the signaling path or the media, however securing a VoIP phone is conceptually easier to implement than on traditional telephone circuits. A result of the lack of encryption is a relative easy to eavesdrop on VoIP calls when access to the data network is possible.[28] Free open-source solutions, such as Wireshark, facilitate capturing VoIP conversations.

Standards for securing VoIP are available in the Secure Real-time Transport Protocol (SRTP) and the ZRTP protocol for analog telephony adapters as well as for some softphones. IPsec is available to secure point-to-point VoIP at the transport level by using opportunistic encryption.

Government and military organizations use various security measures to protect VoIP traffic, such as voice over secure IP (VoSIP), secure voice over IP (SVoIP), and secure voice over secure IP (SVoSIP).[29] The distinction lies in whether encryption is applied in the telephone or in the network[30] or both. Secure voice over secure IP is accomplished by encrypting VoIP with protocols such as SRTP or ZRTP. Secure voice over IP is accomplished by using Type 1 encryption on a classified network, like SIPRNet.[31][32][33][34][35] Public Secure VoIP is also available with free GNU programs and in many popular commercial VoIP programs via libraries such as ZRTP.[36]

Caller ID[edit]
Further information: Caller ID spoofing
Caller ID support among VoIP providers varies, but is provided by the majority of VoIP providers. Many VoIP service providers allow callers to configure arbitrary caller ID information, thus permitting spoofing attacks.[37] Business-grade VoIP equipment and software often makes it easy to modify caller ID information, providing many businesses great flexibility.
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The United States enacted the Truth in Caller ID Act of 2009 on December 22, 2010. This law makes it a crime to “knowingly transmit misleading or inaccurate caller identification information with the intent to defraud, cause harm, or wrongfully obtain anything of value …”.[38] Rules implementing the law were adopted by the Federal Communications Commission on June 20, 2011.[39]

Compatibility with traditional analog telephone sets[edit]
Most analog telephone adapters do not decode dial pulses generated by older telephones, supporting only touch-tone. Pulse-to-tone converters are commercially available;[40] a user reports that a few specific ATA models (such as the Grandstream 502) recognise pulse dial directly, but are poorly documented and provide no assurance that newer models in the same series will retain this compatibility. This however, will only work for one VoIP conversation at a time.[41]

IP Mobility Columbus Ohio Oh

Support for other telephony devices[edit]
Another challenge for VoIP implementations is the proper handling of outgoing calls from other telephony devices such as digital video recorders, satellite television receivers, alarm systems, conventional modems and other similar devices that depend on access to a PSTN telephone line for some or all of their functionality.

These types of calls sometimes complete without any problems, but in other cases they fail. If VoIP and IP Mobility Columbus Ohio Oh cellular substitution becomes very popular, some ancillary equipment makers may be forced to redesign equipment, because it would no longer be possible to assume a conventional PSTN telephone line would be available in consumers’ houses.

Operational cost[edit]
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.[42]
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.[43]
Eliminating the need of hiring personnel to greet and distribute incoming calls with the use of a Virtual PBX
VoIP can be scaled easy, allowing it to grow with the business without restrictive contracts [44]
Regulatory and legal issues[edit]
As the popularity of VoIP grows, governments are becoming more interested in regulating VoIP in a manner similar to PSTN services.[45]

Throughout the developing world, countries where regulation is weak or captured by the dominant operator, restrictions on the use of VoIP are imposed, including in Panama where VoIP is taxed, Guyana where VoIP is prohibited and India where its retail commercial sales is allowed but only for long distance service.[46] In Ethiopia, where the government is nationalising telecommunication service, it is a criminal offence to offer services using VoIP. The country IP Mobility Columbus Ohio Oh has installed firewalls to prevent international calls being made using VoIP. These measures were taken after the popularity of VoIP reduced the income generated by the state owned telecommunication company.

European Union[edit]
Ambox current red.svg
This section is outdated. Please update this article to reflect recent events or newly available information.
Last update: 2006 (September 2013)
In the European Union, treatment of VoIP service providers is a decision for each national telecommunications regulator, which must use competition law to define relevant national markets and then determine whether any service provider on those national markets has “significant market power” (and so should be subject to certain obligations). A general distinction is usually made between VoIP services that function over managed networks (via broadband connections) and VoIP services that function over unmanaged networks (essentially, the Internet).[citation needed]

IP Mobility Columbus Ohio Oh

The relevant EU Directive is not clearly drafted concerning obligations which can exist independently of market power (e.g., the obligation to offer access to emergency calls), and it is impossible to say definitively whether VoIP service providers of either type are bound by them. A review of the EU Directive IP Mobility Columbus Ohio Oh is under way and should be complete by 2007.[citation needed]

In India, it is legal to use VoIP, but it is illegal to have VoIP gateways inside India.[47] This effectively means that people who have PCs can use them to make a VoIP call to any number, but if the remote side is a normal phone, the gateway that converts the VoIP call to a POTS call is not permitted by law to be inside India. Foreign based Voip server services are illegal to use in India.[47]

In the interest of the Access Service Providers and International Long Distance Operators the Internet telephony was permitted to the ISP with restrictions. Internet Telephony is considered to be different service in its scope, nature and kind from real time voice as offered by other Access Service Providers and Long Distance Carriers. Hence the following type of Internet Telephony are permitted in India:[48]

IP Mobility Columbus Ohio Oh

(a) PC to PC; within or outside India
(b) PC / a device / Adapter conforming to standard of any international agencies like- ITU or IETF etc. in India to PSTN/PLMN abroad.
(c) Any device / Adapter conforming to standards of International agencies like ITU, IETF etc. connected to ISP node with static IP address to similar device / Adapter; within or outside India.
(d) Except whatever is described in condition (ii) above, no other form of Internet Telephony is permitted.
(e) In India no Separate Numbering Scheme is provided to the Internet Telephony. Presently the 10 digit Numbering allocation based on E.164 is permitted to the Fixed Telephony, GSM, CDMA wireless service. For Internet Telephony the numbering scheme shall only conform to IP addressing Scheme of Internet Assigned Numbers Authority (IANA). Translation IP Mobility Columbus Ohio Oh of E.164 number / private number to IP address allotted to any device and vice versa, by ISP to show compliance with IANA numbering scheme is not permitted.
(f) The Internet Service Licensee is not permitted to have PSTN/PLMN connectivity. Voice communication to and from a telephone connected to PSTN/PLMN and following E.164 numbering is prohibited in India.
Middle East[edit]
In the UAE and Oman it is illegal to use any form of VoIP, to the extent that Web sites of Gizmo5 are blocked. Providing or using VoIP services is illegal in Oman. Those who violate the law stand to be fined 50,000 Omani Rial (about 130,317 US dollars) or spend two years in jail or both. In 2009, police in Oman have raided 121 Internet cafes throughout the country and arrested 212 people for using/providing VoIP services.[citation needed]
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South Korea[edit]
In South Korea, only providers registered with the government are authorized to offer VoIP services. Unlike many VoIP providers, most of whom offer flat rates, Korean IP Mobility Columbus Ohio Oh VoIP services are generally metered and charged at rates similar to terrestrial calling. Foreign VoIP providers encounter high barriers to government registration. This issue came to a head in 2006 when Internet service providers providing personal Internet services by contract to United States Forces Korea members residing on USFK bases threatened to block off access to VoIP services used by USFK members as an economical way to keep in contact with their families in the United States, on the grounds that the service members’ VoIP providers were not registered. A compromise was reached between USFK and Korean telecommunications officials in January 2007, wherein USFK service members arriving in Korea before June 1, 2007, and subscribing to the ISP services provided on base may continue to use their US-based VoIP subscription, but later arrivals must use a Korean-based VoIP provider, which by contract will offer pricing similar to the flat rates offered by US VoIP providers.[49]

United States[edit]
In the United States, the Federal Communications Commission requires all interconnected VoIP service providers to comply with requirements comparable to those for traditional telecommunications service providers.[50] VoIP operators in the US are required to support local number portability; make service accessible to people with disabilities; pay regulatory fees, universal service contributions, and other mandated payments; and enable law enforcement authorities to conduct surveillance pursuant to the Communications Assistance for Law Enforcement Act (CALEA).

Operators of “Interconnected” VoIP (fully connected to the PSTN) are mandated to provide Enhanced 911 service without special request, provide for customer location updates, clearly disclose any limitations on their E-911 functionality to their consumers, obtain affirmative acknowledgements of these disclosures from all consumers,[51] and ‘may not allow their customers to “opt-out” of 911 service.'[52] VoIP operators also receive the benefit IP Mobility Columbus Ohio Oh of certain US telecommunications regulations, including an entitlement to interconnection and exchange of traffic with incumbent local exchange carriers via wholesale carriers. Providers of “nomadic” VoIP service—those who are unable to determine the location of their users—are exempt from state telecommunications regulation.[53]

Another legal issue that the US Congress is debating concerns changes to the Foreign Intelligence Surveillance Act. The issue in question is calls between Americans and foreigners. The National Security Agency (NSA) is not authorized to tap Americans’ conversations without a warrant—but the Internet, and specifically VoIP does not draw as clear a line to the location of a caller or a call’s recipient as the traditional phone system does. As VoIP’s low cost and flexibility convinces more and more organizations to adopt the technology, the surveillance for law enforcement agencies becomes more difficult. VoIP technology has also increased security concerns because VoIP and similar technologies have made it more difficult for the government to determine where a target is physically located when communications are being intercepted, and that creates a whole set of new legal challenges.[54]
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Historical milestones[edit]
1973: Network Voice Protocol (NVP) developed by Danny Cohen and others to carry real time voice over Arpanet.[55][56]
1974: The Institute of Electrical and Electronic Engineers (IEEE) published a paper titled “A Protocol IP Mobility Columbus Ohio Oh for Packet Network Interconnection”.[57]
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.[58]
1986: Proposals from various standards organizations[specify] 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.[59]
1992: Voice over Frame Relay standards development within Frame Relay Forum
1994: MTALK, a freeware VoIP application for Linux[60]
1995: VocalTec releases the first commercial Internet phone software.[61][62]
Beginning in 1995, Intel, Microsoft and Radvision initiated standardization activities for VoIP communications system.[63]
ITU-T begins development of standards for the transmission and signaling of voice communications over Internet Protocol networks with the H.323 standard.[64]
US telecommunication companies petition the US Congress to ban Internet phone technology.[65]
1997: Level 3 began development of its first softswitch, a term they coined in 1998.[66]
The Session Initiation Protocol (SIP) specification RFC 2543 is released.[67]
Mark Spencer of Digium develops the first open source private branch exchange (PBX) software (Asterisk).[68]
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.[69][70]
Quality of service[edit]
Communication on the IP network is perceived as less reliable in contrast to the circuit-switched public telephone network because it does not provide a network-based mechanism to ensure that data packets are not lost, and are delivered in sequential order.[citation needed] It is a best-effort network without fundamental Quality of Service (QoS) guarantees. Therefore, VoIP implementations may face problems with latency, packet loss, and jitter.[71][72]

By default, network routers handle traffic on a first-come, first-served basis. Network routers on high volume traffic links may introduce latency that exceeds permissible thresholds for VoIP. Fixed delays cannot be controlled, as they are caused by the physical distance the packets travel; however, latency can be minimized by marking voice packets as being delay-sensitive with methods such as DiffServ.[71]

IP VoIP Conventional Business IP Mobility Columbus Ohio Oh Telephone System

VoIP endpoints usually have to wait for completion of transmission of previous packets before new data may be sent. Although it is possible to preempt (abort) a less important packet in mid-transmission, this is not commonly done, especially on high-speed links where transmission times are short even for maximum-sized packets.[73] An alternative to preemption on slower links, such as dialup and digital subscriber line (DSL), is to reduce the maximum transmission time by reducing the maximum transmission unit. But every packet must contain protocol headers, so this increases relative header overhead on every link traversed, not just the bottleneck (usually Internet access) link.[73]

DSL modems provide Ethernet (or Ethernet over USB) connections to local equipment, but inside they are actually Asynchronous Transfer Mode (ATM) modems. They use ATM Adaptation Layer 5 (AAL5) to segment each Ethernet packet into a series of 53-byte ATM cells for transmission, reassembling them back into Ethernet frames at the receiving end. A virtual circuit identifier (VCI) is part of the 5-byte header on every ATM cell, so the transmitter can multiplex the active virtual circuits (VCs) in any arbitrary order. Cells from the same VC are always sent sequentially.

However, a majority of DSL providers use only one VC for each customer, even those with bundled VoIP service. Every Ethernet frame must be completely transmitted before another can begin. If a second VC were established, given high priority and reserved for VoIP, then a low priority data packet could be suspended in mid-transmission and a VoIP packet sent right away on the high priority VC. Then the link would pick up the low priority VC IP Mobility Columbus Ohio Oh where it left off. Because ATM links are multiplexed on a cell-by-cell basis, a high priority packet would have to wait at most 53 byte times to begin transmission. There would be no need to reduce the interface MTU and accept the resulting increase in higher layer protocol overhead, and no need to abort a low priority packet and resend it later.

ATM has substantial header overhead: 5/53 = 9.4%, roughly twice the total header overhead of a 1500 byte Ethernet frame. This “ATM tax” is incurred by every DSL user whether or not they take advantage of multiple virtual circuits – and few can.[71]

ATM’s potential for latency reduction is greatest on slow links, because worst-case latency decreases with increasing link speed. A full-size (1500 byte) Ethernet frame takes 94 ms to transmit at 128 kbit/s but only 8 ms at 1.5 Mbit/s. If this is the bottleneck link, this latency is probably small enough to ensure good VoIP performance without MTU reductions or multiple ATM VCs. The latest generations of DSL, VDSL and VDSL2, carry Ethernet without intermediate ATM/AAL5 layers, and they generally support IEEE 802.1p priority tagging so that VoIP can be queued ahead of less time-critical traffic.[71]

Voice, and all other data, travels in packets over IP networks with fixed maximum capacity. This system may be more prone to congestion[citation needed] and DoS attacks[74] than traditional circuit switched systems; a circuit switched system of insufficient capacity will refuse new connections while carrying the remainder without impairment, while the quality of real-time data such as telephone conversations on packet-switched networks degrades dramatically.[71]

Fixed delays cannot be controlled as they are caused by the physical distance the packets travel. They are especially problematic when satellite circuits are involved because of the long distance to a geostationary satellite and back; delays of 400–600 ms are typical.

IP Mobility Columbus Ohio Oh

When the load on a link grows so quickly that its switches experience queue overflows, congestion results and data packets are lost. This signals a transport protocol like TCP to reduce its transmission rate to alleviate the congestion. But VoIP usually uses UDP not TCP because recovering from congestion through retransmission usually entails too much latency.[71] So QoS mechanisms can avoid the undesirable loss of VoIP packets by immediately transmitting them ahead of any queued bulk traffic on the same link, even when that bulk traffic queue is overflowing.

The receiver must resequence IP packets that arrive out of order and recover gracefully when packets arrive too late or not at all. Jitter results from the rapid and random (i.e. unpredictable) changes in queue lengths along a given Internet path due to competition from other users for the same transmission links. VoIP receivers counter jitter by storing incoming packets briefly in a “de-jitter” or “playout” buffer, deliberately increasing latency to improve the chance that each packet will be on hand when it is IP Mobility Columbus Ohio Oh time for the voice engine to play it. The added delay is thus a compromise between excessive latency and excessive dropout, i.e. momentary audio interruptions.

Although jitter is a random variable, it is the sum of several other random variables that are at least somewhat independent: the individual queuing delays of the routers along the Internet path in question. Thus according to the central limit theorem, we can model jitter as a gaussian random variable. This suggests continually estimating the mean delay and its standard deviation and setting the playout delay so that only packets delayed more than several standard deviations above the mean will arrive too late to be useful. In practice, however, the variance in latency of many Internet paths is dominated by a small number (often one) of relatively slow and congested “bottleneck” links. Most Internet backbone links are now so fast (e.g. 10 Gbit/s) that their delays are dominated by the transmission medium (e.g. optical fiber) and the routers driving them do not have enough buffering for queuing delays to be significant.

It has been suggested to rely on the packetized nature of media in VoIP communications and transmit the stream of packets from the source phone to the destination phone simultaneously across different routes (multi-path routing).[75] In such a way, temporary failures have less impact on the communication quality. In capillary routing it has been suggested to use at the packet level Fountain codes or particularly raptor codes for transmitting extra redundant packets making the communication more reliable.[citation needed]

A number of protocols have been defined to support the reporting of quality of service (QoS) and quality of experience (QoE) for VoIP calls. These include RTCP Extended Report (RFC 3611), SIP RTCP Summary Reports, H.460.9 Annex B (for H.323), H.248.30 and MGCP extensions. The RFC 3611 VoIP Metrics block is generated by an IP phone or gateway during a live call and contains information on packet loss rate, packet discard rate (because of jitter), packet loss/discard burst metrics (burst length/density, gap length/density), network delay, end system delay, signal / noise / echo level, Mean Opinion Scores (MOS) and R factors and configuration information related to the jitter buffer.

RFC 3611 VoIP metrics reports are exchanged between IP endpoints on an occasional basis during a call, and an end of call message sent via SIP RTCP Summary Report or one of the other signaling protocol extensions. RFC 3611 VoIP metrics reports are intended to support real time feedback related to QoS IP Mobility Columbus Ohio Oh problems, the exchange of information between the endpoints for improved call quality calculation and a variety of other applications.

Rural areas in particular are greatly hindered in their ability to choose a VoIP system over PBX. This is generally down to the poor access to superfast broadband in rural country areas. With the release of 4G data, there is a potential for corporate users based outside of populated areas to switch their internet connection to 4G data, which is comparatively as fast as a regular superfast broadband connection. This greatly enhances the overall quality and user experience of a VoIP system in these areas. This method was already trialled in rural Germany, surpassing all expectations.[76]

IP Mobility Columbus Ohio Oh

A number of protocols that deal with the data link layer and physical layer include quality-of-service mechanisms that can be used to ensure that applications like VoIP work well even in congested scenarios. Some examples include:

IEEE 802.11e is an approved amendment to the IEEE 802.11 standard that defines a set of quality-of-service enhancements for wireless LAN applications through modifications to the Media Access Control (MAC) layer. The standard is considered of critical importance for delay-sensitive applications, such as voice over wireless IP.
IEEE 802.1p defines 8 different classes of service (including one dedicated to voice) for traffic on layer-2 wired Ethernet.
The ITU-T G.hn standard, which provides a way to create a high-speed (up to 1 gigabit per second) Local area network (LAN) using existing home wiring (power lines, phone lines and coaxial cables). G.hn provides QoS by means of “Contention-Free Transmission Opportunities” (CFTXOPs) which are allocated to flows (such as a VoIP call) which require QoS and which have negotiated a “contract” with the network controllers.
See also[edit]
Audio over IP
Capillary routing
Call shop
Communications Assistance For Law Enforcement Act
Comparison of audio network protocols
Comparison of VoIP software
Dial peer
Differentiated services
High bit rate audio video over Internet Protocol
Integrated services
Internet fax
IP Multimedia Subsystem
Managed Facility Voice Network
Mobile VoIP
Mouth-to-ear delay
Network Voice Protocol
Predictive dialers
Publicly Available Telephone Services
Push-button telephone
RTP audio video profile
Secure telephone
Session Initiation Protocol IP Mobility Columbus Ohio Oh
Sim box
SIP Trunking
Voice VPN
VoIP recording

IP Mobility Columbus Ohio Oh


IP Mobility Columbus Ohio Oh

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