Voice over IP

Example of residential network including VoIP
Asterisk-based PBX for small business

Method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet.

- Voice over IP
Example of residential network including VoIP

500 related topics

Relevance

Screenshot of Skype version 8 (14.32.55.0) for Windows desktop on Windows 10 in dark mode (note: contacts censored)

Skype

Screenshot of Skype version 8 (14.32.55.0) for Windows desktop on Windows 10 in dark mode (note: contacts censored)
Screenshot of Skype version 8 (14.32.55.0) for Windows desktop on Windows 10 in dark mode (note: contacts censored)
Skype 4.0 (released 2009)
PRISM: a clandestine surveillance program under which the NSA collects user data from companies like Skype and Facebook

Skype is a proprietary telecommunications application operated by Skype Technologies, a division of Microsoft, best known for VoIP-based videotelephony, videoconferencing and voice calls.

Comparison of spectrograms of audio in an uncompressed format and several lossy formats. The lossy spectrograms show bandlimiting of higher frequencies, a common technique associated with lossy audio compression.

Speech coding

Application of data compression of digital audio signals containing speech.

Application of data compression of digital audio signals containing speech.

Comparison of spectrograms of audio in an uncompressed format and several lossy formats. The lossy spectrograms show bandlimiting of higher frequencies, a common technique associated with lossy audio compression.

Some applications of speech coding are mobile telephony and voice over IP (VoIP).

SIP user agent registration to SIP registrar with authentication.

Session Initiation Protocol

Signaling protocol used for initiating, maintaining, and terminating real-time sessions that include voice, video and messaging applications.

Signaling protocol used for initiating, maintaining, and terminating real-time sessions that include voice, video and messaging applications.

SIP user agent registration to SIP registrar with authentication.
Establishment of a session through a back-to-back user agent.
Example: User1's UAC uses an invite client transaction to send the initial INVITE (1) message. If no response is received after a timer-controlled wait period the UAC may choose to terminate the transaction or retransmit the INVITE. Once a response is received, User1 is confident the INVITE was delivered reliably. User1's UAC must then acknowledge the response. On delivery of the ACK (2), both sides of the transaction are complete. In this case, a dialog may have been established.

SIP is used for signaling and controlling multimedia communication sessions in applications of Internet telephony for voice and video calls, in private IP telephone systems, in instant messaging over Internet Protocol (IP) networks as well as mobile phone calling over LTE (VoLTE).

FaceTime

Proprietary videotelephony product developed by Apple Inc. FaceTime is available on supported iOS mobile devices running iOS 4 and later and Mac computers that run Mac OS X 10.6.6 and later.

Proprietary videotelephony product developed by Apple Inc. FaceTime is available on supported iOS mobile devices running iOS 4 and later and Mac computers that run Mac OS X 10.6.6 and later.

The iPhone's screen when a call is in progress, showing the FaceTime button (grayed out, middle of bottom row).

SIP – IETF signaling protocol for VoIP.

XMPP

Open communication protocol designed for instant messaging (IM), presence information, and contact list maintenance.

Open communication protocol designed for instant messaging (IM), presence information, and contact list maintenance.

A simple XMPP network with the servers jabber.org and draugr.de. Green clients are online, yellow clients are writing each other and small green subclients are the resources of one user. The brown network is not connected to the internet. The server draugr.de is connected to other IM services (ICQ, AIM and other) via XMPP transports.
A standard JID
File transfer options in a chat in Conversations, an XMPP client for Android
Alice sends a message through the XMPP net to the ICQ transport. The message is next routed to Bob via the ICQ network.
Buddy list and a multi-user chat in Spark
Jabber logo

Designed to be extensible, the protocol offers a multitude of applications beyond traditional IM in the broader realm of message-oriented middleware, including signalling for VoIP, video, file transfer, gaming and other uses.

A fax machine from 1999 employing inkjet printing, which was modern for fax machines at that time.

Fax

Telephonic transmission of scanned printed material (both text and images), normally to a telephone number connected to a printer or other output device.

Telephonic transmission of scanned printed material (both text and images), normally to a telephone number connected to a printer or other output device.

A fax machine from 1999 employing inkjet printing, which was modern for fax machines at that time.
Fax machine from 1990, using thermal printing which required special, relatively expensive thermal paper.
Children read a wirelessly transmitted newspaper in 1938.
Laser fax having a compact, built-in laser printer, 2001.
Professional laser fax machine for office use with the Super G3 standard for faster fax transmission.
The Dacom DFC-10—the first digital fax machine
The chip in a fax machine. Only about one quarter of the length is shown. The thin line in the middle consists of photosensitive pixels. The read-out circuit is at left.
Paper roll for direct thermal fax machine

T.38 is designed to work with VoIP services and often supported by analog telephone adapters used by legacy fax machines that need to connect through a VoIP service.

Figure 2. The TCP/IP model or Internet layering scheme and its relation to some common protocols.

Real-time Transport Protocol

Network protocol for delivering audio and video over IP networks.

Network protocol for delivering audio and video over IP networks.

Figure 2. The TCP/IP model or Internet layering scheme and its relation to some common protocols.

RTP is one of the technical foundations of Voice over IP and in this context is often used in conjunction with a signaling protocol such as the Session Initiation Protocol (SIP) which establishes connections across the network.

A commercial IP telephone, with keypad, control keys, and screen functions to perform configuration and user features.

Quality of service

Description or measurement of the overall performance of a service, such as a telephony or computer network or a cloud computing service, particularly the performance seen by the users of the network.

Description or measurement of the overall performance of a service, such as a telephony or computer network or a cloud computing service, particularly the performance seen by the users of the network.

A commercial IP telephone, with keypad, control keys, and screen functions to perform configuration and user features.

In particular, developers have introduced Voice over IP technology to allow computer networks to become as useful as telephone networks for audio conversations, as well as supporting new applications with even stricter network performance requirements.

Early-1970s Telephone Exchange model TESLA Automatic system

Business telephone system

Multiline telephone system typically used in business environments, encompassing systems ranging in technology from the key telephone system to the private branch exchange (PBX).

Multiline telephone system typically used in business environments, encompassing systems ranging in technology from the key telephone system to the private branch exchange (PBX).

Early-1970s Telephone Exchange model TESLA Automatic system
Early model 464G Western Electric key telephone set
A 1930s key telephone for a private branch exchange.
A typical rotary dial key telephone: the Western Electric eighteen-button Call Director, manufactured from 1958 to the early '80s.
Nortel T Series Key System Telephone
An Avaya G3si PBX with front cover removed (view from the top)
An Alcatel Lucent PABX Omni PCX Enterprise (Front view)
Racks of a Strowger telephone exchange, showing two-motion selectors in the United Kingdom.
Cord PBX switchboard (c.1975)
Early 1945 telephone exchange model N935 system featuring cordless operation.
Manual cord telephone exchange exhibited in Ainokura Traditional Industry Museum in Japan.

The modern key system is usually fully digital, although analog variants persist and some systems implement VOIP services.

This column about "trucks and cars" from Popular Mechanics in 1914 was written when the word truck did not necessarily connote a motor truck and the word car did not necessarily connote a motor car. The same topics today would most likely be talked about with the terms hand trucks and railroad cars. Those terms existed in 1914 as well, but they were not required for clarity, as they would be today.

Plain old telephone service

Retronym for voice-grade telephone service employing analog signal transmission over copper loops.

Retronym for voice-grade telephone service employing analog signal transmission over copper loops.

This column about "trucks and cars" from Popular Mechanics in 1914 was written when the word truck did not necessarily connote a motor truck and the word car did not necessarily connote a motor car. The same topics today would most likely be talked about with the terms hand trucks and railroad cars. Those terms existed in 1914 as well, but they were not required for clarity, as they would be today.

POTS was the standard service offering from telephone companies from 1876 until 1988 in the United States when the Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) was introduced, followed by cellular telephone systems, and voice over IP (VoIP).